JP2007053890A - Surface acoustic wave actuator - Google Patents

Abstract

A surface acoustic wave actuator capable of reliably moving a moving element is provided.
A surface acoustic wave actuator includes a piezoelectric substrate 2 and a pair of interdigitated electrodes 3 and 4 that are disposed to face the surface of the piezoelectric substrate 2 at a predetermined distance and excite surface acoustic waves on the piezoelectric substrate 2. A stator 1 provided thereon, a mover 5 mounted on the surface of the piezoelectric substrate 2 and moved by the surface acoustic wave, and preload means for bringing the mover 5 into contact with the stator 1 at a predetermined pressure N. The pair of cross-finger electrodes 3 and 4 are configured to reflect the surface acoustic wave excited by the opposite cross-finger electrode toward the opposite cross-finger electrode, and the surface acoustic waves traveling in the same direction have the same phase. Is set to have.
[Selection] Figure 1

Description

  The present invention relates to a surface acoustic wave actuator.

  Conventionally, an ultrasonic motor is known as an actuator for driving an object. An ultrasonic motor generates mechanical vibrations in an elastic body by an ultrasonic vibrator, and extracts a driving force mainly from an elliptical motion that appears on the surface of the elastic body through a frictional force.

As one of such ultrasonic motors, a surface acoustic wave actuator (SAW (Surface Acoustic Wave) actuator) has been conventionally provided, and the surface acoustic wave actuator includes a surface acoustic wave element serving as a stator (stator), A drive electrode (excitation electrode) made of IDT (Interdigital Transducer) formed on both sides of the surface of the surface acoustic wave element, a slider (slider) mounted on the surface acoustic wave element for linear movement, and a slider And a preloading means for contacting the stator with a predetermined pressure (for example, Patent Document 1).
JP-A-9-233865 (FIG. 1)

  In conventional surface acoustic wave actuators, when a high-frequency (several MHz band) surface acoustic wave is excited by a drive electrode, the mover obtains thrust from a few nanometers of vibration obtained by the surface acoustic wave and moves on the stator. By switching the drive electrode for exciting the surface acoustic wave, the movable element can be reciprocated on the stator.

  Here, in order to move the moving element, it is necessary to excite a surface acoustic wave having energy in a plane direction that can vibrate against the pressure of the preloading means (can lift the moving element) by the IDT, When the surface acoustic wave actuator is driven with low power, there is a problem that the surface acoustic wave energy applied to the moving element is insufficient and the moving element cannot be moved.

  Such a problem seems to be solved by lowering the pressure of the preloading means according to the surface acoustic wave energy when driving the surface acoustic wave actuator with low power, but when the pressure of the preloading means is lowered Naturally, since the contact pressure between the moving element and the stator becomes low, it becomes difficult for the moving element to obtain thrust from the surface acoustic wave generated in the stator, and as a result, the moving element becomes difficult to move. Problems will arise.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a surface acoustic wave actuator that can move a moving element with certainty.

  In order to solve the above-mentioned problems, in the invention of the surface acoustic wave actuator according to claim 1, a pair of piezoelectric substrates and a pair of surfaces that are disposed to face the surface of the piezoelectric substrate at a predetermined distance and excite surface acoustic waves on the piezoelectric substrate. A stator having crossed finger electrodes, a mover placed on the surface of the piezoelectric substrate and moved by the surface acoustic wave, and preload means for bringing the mover into contact with the stator at a predetermined pressure, The pair of cross finger electrodes is a surface acoustic wave actuator configured to reflect the surface acoustic wave excited by the opposing cross finger electrode toward the opposing cross finger electrode, and the surface acoustic wave traveling in the same direction. A phase adjusting means for adjusting the phase is provided.

  According to the surface acoustic wave actuator of the first aspect of the invention, since the phase adjustment means for adjusting the phase of the surface acoustic wave traveling in the same direction is provided, the elastic surface directed from one cross finger electrode to the other cross finger electrode. It is possible for the surface acoustic wave that is reflected the same number of times by each cross finger electrode and directed to the other cross finger electrode to have the same phase, so that the surface acoustic wave traveling in the same direction has the same phase. The surface acoustic wave energy is accumulated on the stator and can be vibrated against the pressure of the preloading means even when the power is low when the surface acoustic wave is excited by one of the interdigital electrodes. A surface acoustic wave having a large amount of energy in the surface direction can be applied to the movable element, thereby producing an effect that the movable element can be reliably moved.

  In a surface acoustic wave actuator according to a second aspect of the present invention, there is provided a stator including a piezoelectric substrate and a pair of cross-finger electrodes that are disposed to face the surface of the piezoelectric substrate at a predetermined distance and excite surface acoustic waves on the piezoelectric substrate. A movable element placed on the surface of the piezoelectric substrate and moved by the surface acoustic wave; and a preload means for bringing the movable element into contact with the stator at a predetermined pressure, and the pair of cross finger electrodes face each other. A surface acoustic wave actuator configured to reflect a surface acoustic wave excited by a cross finger electrode toward the opposing cross finger electrode, and a distance between equivalent reflection surfaces of a pair of cross finger electrodes is determined by each cross finger. It is characterized by being set to a value substantially equal to an integral multiple of a half wavelength of the surface acoustic wave generated at the electrode.

  According to the surface acoustic wave actuator of the second aspect, the distance between the equivalent reflective surfaces of the pair of cross finger electrodes is approximately equal to an integral multiple of half the wavelength of the surface acoustic wave generated at each cross finger electrode. Therefore, the surface acoustic wave that travels from one crossed finger electrode to the other crossed finger electrode and the surface acoustic wave that is reflected the same number of times by each crossed finger electrode and travels to the other crossed finger electrode have the same phase. As a result, the surface acoustic waves traveling in the same direction are superposed in the same phase and the energy of the surface acoustic waves is accumulated on the stator, and when the surface acoustic waves are excited by one of the interdigitated electrodes In addition, it is possible to give the moving element a surface acoustic wave having energy in the direction of the plane that can vibrate against the pressure of the preloading means even at low power, and thereby the moving element can be moved reliably. Play.

  In the invention of the surface acoustic wave actuator according to claim 3, in addition to the configuration of claim 1 or 2, the interval between the cross fingers of the cross finger electrode so that the reflectance of the cross finger electrode with respect to the surface acoustic wave becomes a predetermined value. Alternatively, the number of a pair of cross fingers having different polarities of the cross finger electrodes is set.

  According to the surface acoustic wave actuator of the third aspect of the present invention, it is possible to achieve elasticity with a simple configuration by simply setting the distance between the cross fingers of the cross finger electrodes or the number of a pair of cross fingers having different polarities from each other. There is an effect that a cross finger electrode having a predetermined reflectance with respect to a surface wave can be obtained.

  In the surface acoustic wave actuator according to the fourth aspect of the invention, in addition to the configuration of any one of the first to third aspects, the phase adjusting means is connected to the cross finger electrode and generates a surface acoustic wave at the cross finger electrode. It is an electric circuit unit for phase adjustment that changes the phase of a surface acoustic wave according to the value of impedance when reflecting.

  According to the surface acoustic wave actuator of the fourth aspect of the present invention, the phase of the surface acoustic wave traveling in the same direction can be adjusted only by changing the impedance value of the electric circuit section for phase adjustment. There is an effect that the phase can be easily adjusted by the means.

  According to a surface acoustic wave actuator of a fifth aspect of the invention, in addition to the configuration of the fourth aspect, the phase adjusting electric circuit section includes a phase adjusting impedance element capable of adjusting an impedance value. .

  According to the surface acoustic wave actuator of the fifth aspect of the present invention, the phase adjustment impedance element that can adjust the impedance value is used in the phase adjustment electric circuit section, so that the phase adjustment by the phase adjustment means is further facilitated. The effect that it can be performed is produced.

  According to the surface acoustic wave actuator of the sixth aspect of the invention, in addition to the configuration of the fifth aspect, the phase adjustment electric circuit unit is configured to reduce the impedance value of the phase adjustment impedance element so that the speed of the moving element becomes a target value. It is characterized by having a phase control unit for setting.

  According to the invention of the surface acoustic wave actuator of the sixth aspect, the speed of the moving element is maintained at the target value by adjusting the phase of the surface acoustic wave traveling in the same direction. It is possible to prevent the speed of the moving element from being lowered due to various causes such as the above.

  According to the surface acoustic wave actuator of a seventh aspect, in addition to the structure of any one of the first to sixth aspects, a reflectance adjusting means for adjusting the reflectance of the crossed finger electrode with respect to the surface acoustic wave is provided. It is characterized by.

  According to the surface acoustic wave actuator of the seventh aspect of the present invention, the reflectance of the cross finger electrode with respect to the surface acoustic wave can be adjusted by the reflectance adjusting means, so that it is possible to easily design the cross finger electrode.

  According to the surface acoustic wave actuator of the eighth aspect of the invention, in addition to the configuration of the seventh aspect, the reflectance adjusting means is connected to the interdigital electrode and determines the reflectance of the interdigital electrode with respect to the surface acoustic wave as an impedance value. The electrical circuit unit for adjusting the reflectance is changed according to the above.

  According to the surface acoustic wave actuator of the eighth aspect of the present invention, since the reflectance of the cross finger electrode with respect to the surface acoustic wave can be adjusted by the impedance value, it is possible to further easily design the cross finger electrode. Play.

  In the invention of the surface acoustic wave actuator according to the ninth aspect, in addition to the configuration of the eighth aspect, the reflectance adjusting electric circuit section includes a reflectance adjusting impedance element whose impedance value is adjustable. And

  According to the surface acoustic wave actuator of the ninth aspect of the present invention, the reflectance adjusting impedance element that can adjust the impedance value is used in the reflectance adjusting electric circuit section. There is an effect that the adjustment can be performed more easily.

  In the invention of the surface acoustic wave actuator according to the tenth aspect, in addition to the configuration of the ninth aspect, the reflectance adjustment electric circuit section is configured so that the impedance of the reflectance adjustment impedance element is adjusted so that the speed of the moving element becomes a target value. A reflectance control unit for setting the value of is provided.

  According to the invention of the surface acoustic wave actuator of the tenth aspect, the speed of the moving element is maintained at the target value by adjusting the reflectance of the interdigital electrode with respect to the surface acoustic wave. There is an effect that it is possible to prevent the speed of the moving element from being lowered due to various causes such as errors.

  In the invention of the surface acoustic wave actuator of claim 11, in addition to the structure of any one of claims 1 to 10, it is moved by the preloading means so that the attenuation factor of the surface acoustic wave by the preloading means becomes a predetermined value. A pressure value for bringing the child into contact with the stator is set.

  According to the surface acoustic wave actuator of the eleventh aspect, the ratio of the traveling wave component and the standing wave component of the surface acoustic wave excited on the stator depends on the influence of the surface acoustic wave attenuation rate by the preloading means. Therefore, by changing the value of the pressure that causes the moving element to contact the stator by the preloading means, the traveling wave component of the surface acoustic wave excited on the stator can be obtained even after the interdigital electrodes are formed on the stator. There is an effect that the ratio with the standing wave component can be finely adjusted.

  According to the invention of the surface acoustic wave actuator of claim 12, in addition to the structure of any one of claims 1 to 11, switching means for switching the cross finger electrode that is a connection destination of a power source that applies a drive voltage to the cross finger electrode. It is characterized by having.

  According to the surface acoustic wave actuator of the twelfth aspect, since the power source is shared by the crossed finger electrodes, the number of parts and the manufacturing cost can be reduced.

  According to the surface acoustic wave actuator of the thirteenth aspect, in addition to the configuration of any one of the first to twelfth aspects, the interdigitated electrode is a reflection that reflects the surface acoustic wave traveling in a direction other than the desired direction. It is the unidirectional electrode provided with the part.

  According to the invention of the surface acoustic wave actuator of the thirteenth aspect, since the reflective portion that reflects the surface acoustic wave that travels in a direction other than the desired direction is provided in the desired direction, It is possible to excite a surface acoustic wave having a larger energy than the case where it is not provided by means of the interdigital finger electrode, thereby achieving an effect of further reducing power consumption.

  In the surface acoustic wave actuator of the present invention, the surface acoustic wave directed from one crossed finger electrode to the other crossed finger electrode is the same as the surface acoustic wave reflected the same number of times by each crossed finger electrode and directed to the other crossed finger electrode. The surface acoustic wave traveling in the same direction can be superposed in the same phase to accumulate the energy of the surface acoustic wave on the stator. When a surface acoustic wave is excited by a crossed finger electrode, a surface acoustic wave having energy in a surface direction that can vibrate against the pressure of the preloading means can be applied to the moving element even at low power. Thus, there is an effect that the mover can be reliably moved.

  Embodiments of a surface acoustic wave actuator according to the present invention will be described below with reference to FIGS.

(Embodiment 1)
The surface acoustic wave actuator (SAW actuator) of the present embodiment is disposed opposite to the piezoelectric substrate 2 and the surface of the piezoelectric substrate 2 at a predetermined distance as shown in FIG. A stator (stator) 1 having a pair of crossed finger electrodes 3 and 4 for generating surface waves, a mover (slider) 5 mounted on the surface of the piezoelectric substrate 2 and moved by the surface acoustic wave, and movement Preload means (not shown) for bringing the child 5 into contact with the stator 1 at a predetermined pressure N is provided. The cross finger electrode 3 is configured to reflect the surface acoustic wave excited by the opposing cross finger electrode 4 toward the opposing cross finger electrode 4, and the cross finger electrode 4 is excited by the opposing cross finger electrode 3. The surface acoustic wave to be reflected is reflected to the opposing cross finger electrode 3 side, and the distance between the equivalent reflective surfaces of the pair of cross finger electrodes 3 and 4 is half the wavelength of the surface acoustic wave excited by the cross finger electrode. Is set to a value approximately equal to an integer multiple of.

  Here, as shown in FIG. 1B, the movable element 5 is formed using a hard material such as silicon, for example, and makes it easy to obtain a thrust from the substantially rectangular parallelepiped main body 5 a and the stator 1. For this purpose, a plurality of projections 5b are provided integrally on the surface of the main body 5a (the lower surface in the present embodiment) facing the stator 1. In addition, the protrusion 5b is not necessarily required. In short, it is sufficient that the movable element 5 can sufficiently obtain the thrust from the stator 1.

  Further, as the preload means (not shown), for example, an elastic body such as a leaf spring or a spring coil, a magnet that adsorbs a magnetic piece such as iron provided in advance on the moving element 5 or the like is used. The stator 1 is brought into contact with the stator 1.

The stator 1 includes the piezoelectric substrate 2, the first cross finger electrode 3, and the second cross finger electrode 4. Here, the piezoelectric substrate 2 serves as a base material for the stator 1, and is a rectangular piezoelectric material formed using a piezoelectric material having a high electromechanical coupling coefficient such as a LiNbO ₃ (lithium niobate) single crystal. It is a crystal plate. In addition, as such a piezoelectric substrate, not only what was formed by the piezoelectric material but what formed the piezoelectric thin film, such as ZnO, on the surface of the board | substrate of a non-piezoelectric material may be used.

  As shown in FIG. 1A, the first cross finger electrode 3 is a so-called comb-like electrode (IDT, IDT) having a shape in which a plurality of pairs of cross fingers 3a and 3b having different polarities are arranged at predetermined intervals. And is formed on one end side in the longitudinal direction of the surface of the piezoelectric substrate 2 (left end side in FIG. 1A). Further, the cross finger 3a of the first cross finger electrode 3 is connected to one end of the external high frequency power source AC1 via the switch SW1, and the cross finger 3b is connected to the other end of the high frequency power source AC1. When a high-frequency voltage is applied to the first cross finger electrode 3 by the high-frequency power supply AC1, the electrical energy of the first cross finger electrode 3 is converted into mechanical energy, and the surface acoustic wave (Rayleigh wave) is applied to the piezoelectric substrate 2. Wave) is excited. On the other hand, like the first cross finger electrode 3, the second cross finger electrode 4 has a shape in which a plurality of pairs of cross finger electrodes 3a and 3b having different polarities are arranged at predetermined intervals, as shown in FIG. As shown in a), it is formed on the other end side in the longitudinal direction of the surface of the piezoelectric substrate 2 (the right end side in FIG. 1A), and the crossing finger 4a is integrally connected to the high-frequency power source AC2 via the switch SW2. The crossing finger 4b is connected to the other end of the high frequency power source AC2. Here, these switches SW1 and SW2 serve as switching means for switching the interdigitated electrodes that generate surface acoustic waves. In FIG. 1, the cross finger electrodes 3 and 4 are shown in a simplified manner.

  Here, in the first cross finger electrode 3 and the second cross finger electrode 4, the distance between the equivalent reflection surfaces of the cross finger electrodes 3 and 4 is half of the surface acoustic wave excited by the cross finger electrodes 3 and 4. Oppositely arranged on the surface of the piezoelectric substrate 1 so as to be approximately an integral multiple of the wavelength. That is, if the wavelength of the surface acoustic wave is λ and the distance between the equivalent reflection surfaces is D, the distance D between the equivalent reflection surfaces is set so that D≈nλ / 2 (n: integer). Here, the equivalent reflection surface refers to a surface when it is assumed that a surface acoustic wave is reflected by one surface in a cross finger electrode that gradually reflects surface acoustic waves by a plurality of cross fingers.

By setting the distance D between the equivalent reflection surfaces as described above, the surface acoustic wave W ₁ that is excited by the first cross finger electrode 3 and travels toward the second cross finger electrode 4, and the cross finger electrodes 3 and 4. All of the surface acoustic waves W ₃ , W ₅ , W ₇ ... W _2n−1 reflected by the same number of times and directed toward the second cross finger electrode 4 have the same phase and are reflected by the second cross finger electrode 4. All of the surface acoustic waves W ₂ , W ₄ , W ₆ ... W _2n toward the first crossing finger electrode 3 are set to have the same phase.

  Next, the design method of each cross finger electrode 3 and 4 is demonstrated taking the 1st cross finger electrode 3 as an example. The first cross finger electrode 3 has a resonance frequency determined by the interval (pitch) l between the cross fingers 3a and 3a (or cross fingers 3b and 3b) of the same polarity, and the number of pairs of cross fingers 3a and 3b of a pair of different polarities. The frequency characteristic of the reflectance changes depending on m. Therefore, it is possible to obtain the resonance frequency, admittance characteristics (conductance and susceptance), and reflectance frequency characteristics of the interdigitated electrode from the interval l and the number m of the sets by performing a simulation. It is possible to design a cross finger electrode having a frequency characteristic of a rate.

For example, when the interval l = 132.64 μm and the number of sets m = 20, the simulation result shows that the resonance frequency of the cross finger electrode (that is, the conductance peak) f ₀ = 28.9 MHz. In this case, FIG. A cross finger electrode having reflectivity characteristics as shown in (a) is obtained, and this cross finger electrode has a reflectivity of about 0.21 for a surface acoustic wave having a frequency of 28.9 MHz. I understand. Here, when the interval l is increased, the resonance frequency is lowered, and accordingly, the frequency characteristic of the reflectance is shifted to the lower frequency side. When the interval l is reduced, the resonance frequency is increased. Accordingly, the frequency characteristic of the reflectance is shifted to the high frequency side as a whole, so the interval l is temporarily set so that the frequency characteristic of the reflectance is close to a desired value.

  After roughly setting the frequency characteristic of the reflectance by temporarily setting the interval l, the magnitude of the reflectance is set by changing the number m of sets. The graph of FIG. 2 (b) shows the reflectance characteristics of the crossed finger electrodes in which only the number of sets m is different, where a is the number of sets m = 5, b is the number of sets m = 10, and c is the number of sets. m = 15, d is the number of sets m = 20, e is the number of sets m = 30, and the interval l is 132.64 μm. Then, when such a value of the number m of sets and the maximum value of the reflectance are plotted, a graph as shown in FIG. 2C is obtained. That is, it can be seen that if the number of sets m is increased, the maximum value of the reflectance can be increased, and if the number of sets m exceeds 30, the reflectance is about 1. Further, as apparent from FIG. 2B, when the number of sets m is changed, the frequency at which the maximum value of the reflectance is gradually shifted to the lower frequency side, so that the reflectance is maximum. When the frequency that takes the value deviates from the desired value, after determining the number m of sets, the interval l is set again so that the reflectance is maximized at the desired frequency, and the optimum interval l is set. I will fix it.

  By setting the interval l and the number m of sets in this way, the interdigital electrodes 3 and 4 having the desired resonance frequency and reflectance frequency characteristics can be designed.

In the stator 1 described above, by applying a high frequency voltage upon by exciting the surface acoustic wave W ₁ energy P in the first interdigital finger electrode 3 by the high-frequency power supply AC1, the stator 1 as follows A wave will be generated. Note that the reflectance of the first cross finger electrode 3 with respect to the surface acoustic wave having the same frequency as the surface acoustic wave W ₁ is η (0 <η ≦ 1), and the reflectance of the second cross finger electrode 4 is γ (0 <γ ≦ 1). 1) and neglected because the surface acoustic wave attenuation due to propagation is small.

That is, the surface acoustic wave W ₁ excited by the first cross finger electrode 3 is directed to the second cross finger electrode 4 and reaches the second cross finger electrode 4 as shown in FIG. A part of W ₁ is reflected by the second cross finger electrode 4 toward the first cross finger electrode 3 to become a surface acoustic wave W ₂ with energy γP. When the surface acoustic wave W ₂ reaches the first cross finger electrode 3, a part of the surface wave W ₂ is reflected by the first cross finger electrode 3 toward the second cross finger electrode 4 and becomes a surface acoustic wave W ₃ with energy γηP. Similarly, a portion of the surface acoustic wave W ₃ is reflected by the second cross finger electrode ₄ and becomes a surface acoustic wave W ₄ with energy γ ² ηP and travels toward the first cross finger electrode 3. The reflection is repeated.

As described above, the surface acoustic waves W ₁ , W ₃ , W ₅ , W ₇ ... W _2n−1 have the same phase, and the surface acoustic waves W ₂ , W ₄ , W _{6 ,.} since the phase, energy _{P F} of the surface acoustic wave traveling from the first interdigital electrode 3 to the second interdigital finger electrode 4 (that is, the traveling wave) _{W F} is the surface acoustic wave _{W 1,} W _{3, W} 5, W ₇ ... W _2n-1 energy sum, and energy P _F = P {1 + γη + (γη) ² + (γη) ³ +... + (Γη) ²ⁿ⁻¹ }. Further, from the second interdigital finger electrode 4 energy _{P R} of the surface acoustic wave toward the first interdigital finger electrode 3 (that is, the reflected wave) _{W R} is the surface acoustic wave _{W 2,} W _4, W 6, a ... _{W 2n} becomes the sum of the energy, the energy _{P R = γP {1 + γη} + (γη) 2 + (γη) 3 + ... + (γη) 2n-1}. Here, the n → ∞, When a γη <1, energy P _F, the P _R can be expressed by the following equation.

The total energy P _S wave generated in the stator 1 becomes energy P _F of the traveling wave W _F and a total energy P _R of the reflected wave W _R, these to first interdigital finger electrode 3 side of the moving element 5 move to contribute stator 1 of the tangential energy along the surface (hereinafter, referred to as traveling wave component) P _H, the difference between the energy P _F of the traveling wave W _F energy P _R of the reflected wave W _R next, the energy in the plane direction of the stator 1 of the surface which do not contribute to the movement of the moving element 5 (hereinafter, referred to as standing wave component) P _V becomes the difference between the total energy P _S and the traveling-wave component P _H, these P _S , P _H , and P _V can be expressed as follows.

On the other hand, the same result can be obtained when a high frequency voltage is applied to the second cross finger electrode 4 by the high frequency power source AC2 to excite a surface acoustic wave of energy P. In this case, the reflectance of the first cross finger electrode 3 with respect to the surface acoustic wave having the same frequency as the surface acoustic wave excited by the second cross finger electrode 4 is η ′ (0 <η ′ ≦ 1), and the second cross finger electrode 4 is assumed to be γ ′ (0 <γ ′ ≦ 1), and the attenuation of the surface acoustic wave due to propagation is small, so ignoring the total energy P _S ′ of the wave generated in the stator 1 and the traveling wave component P _H ′ And the standing wave component P _V ′ can be expressed as follows:

As it is clear from the number 2 and 3 above, the surface acoustic wave actuator of the present embodiment, the reflectance of the η, η ', γ, γ ' by adjusting the traveling wave component P _H and standing wave it is possible to set the ratio of the components P _V as well as the traveling wave component P _{H 'and} standing wave component P _V'.

In the present embodiment, the energy P _F of the traveling wave W _F is, to be greater than the energy P _R of the reflected wave W _R, although to set the reflectivity of the second interdigital finger electrode 4 gamma, reflecting The rate γ can be set by appropriately setting the interval l and the number m of the interdigital electrodes as described above. Further, the reflectance gamma, against energy _{P F} of the traveling wave _{W F,} the energy _{P R} of the reflected wave _{W R} is preferably set to be equal to or less than 0.98 times 0.5 times or more, the The value of the reflectance γ at this time may be set to a value within the range of 0.5 ≦ γ ≦ 0.98 with reference to the above formula 2. This also applies to the reflectance η of the first crossed finger electrode 3, and the value of the reflectance η may be a value within the range of 0.5 ≦ η ≦ 0.98.

Next, the operation of this surface acoustic wave actuator will be described. First, when the switch SW1 is turned on and a high frequency voltage is applied from the high frequency power source AC1 to the first cross finger electrode 3, the piezoelectric substrate 2 is distorted by the electrical energy of the first cross finger electrode 3, thereby Rayleigh wave, which is a surface acoustic wave, is generated by converting mechanical energy into mechanical energy. This Rayleigh wave propagates from the first cross finger electrode 3 to the second cross finger electrode 4 side via the surface (upper surface) of the piezoelectric substrate 2 and becomes a surface acoustic wave having energy as shown in Formula 2. . Then, the surface acoustic wave, since a magnitude of the standing wave component P _V can lift the moving element 5 against the pressure N, have pressure N is applied to the moving element 5 It can also be moving element 5 to be able to move on the stator 1, and since has wave component P _H of sufficient magnitude, the moving element 5, the propagation of the surface acoustic wave A thrust is obtained from the accompanying minute vibration of the stator 1 and moves to the first cross finger electrode 3 side.

On the other hand, when the switch SW1 is turned off and the switch SW2 is turned on and a high frequency voltage is applied from the high frequency power supply AC2 to the second crossing finger electrode 4, distortion occurs in the piezoelectric substrate 2 as in the first crossing finger electrode 3. This generates a Rayleigh wave. This Rayleigh wave propagates from the second cross finger electrode 4 to the first cross finger electrode 3 side via the surface (upper surface) of the piezoelectric substrate 2 and becomes a surface acoustic wave having energy as shown in Equation 3. . Such a surface acoustic wave has a sufficiently large standing wave component P _V ′ and traveling wave component P _H ′ as in the case of the first interdigitated electrode 3. The mover 5 obtains a thrust from the minute vibration of the stator 1 accompanying the propagation of the surface acoustic wave, and moves to the second cross finger electrode 4 side.

  After that, when the switch SW2 is turned off to stop the power supply from the high frequency power supply AC2, the switch SW1 is turned on again and the high frequency voltage of the high frequency power supply AC1 is applied to the first crossed finger electrode 3, and the elastic surface shown in Equation 2 is obtained. The mover 5 again moves on the stator 1 to the first cross finger electrode 3 side by the wave. That is, in the surface acoustic wave actuator of this embodiment, the movable element 5 repeatedly moves in the longitudinal direction (left-right direction) of the stator 1 by switching the switches SW1 and SW2 on and off.

As described above, according to the surface acoustic wave actuator of this embodiment, the distance D between the first cross finger electrode 3 and the second cross finger electrode 4 and the equivalent reflection surface is generated at each cross finger electrode 3 and 4. The surface acoustic wave W ₁ that is excited by the first cross finger electrode 3 and travels toward the second cross finger electrode 4, and each cross finger electrode 3, The surface acoustic waves W ₃ , W ₅ , W ₇ ... W _2n−1 reflected by the same number of times 4 toward the second cross finger electrode 4 have the same phase and are excited by the second cross finger electrode 4. Since the surface acoustic wave directed to the first cross finger electrode 3 and the surface acoustic wave reflected by the respective cross finger electrodes 3 and 4 and directed toward the first cross finger electrode 3 have the same phase, Surface acoustic waves traveling in the same direction are superposed in the same phase, whereby the energy of the surface acoustic waves is placed on the stator 1. Can accumulate, resulting in the moving element 5 of the surface acoustic wave having a standing wave component P _V of size capable of lifting the moving element 5 against the pressure N of the preload means be a low power Can be given to.

Further, according to the surface acoustic wave actuator, the reflectance of each cross finger electrode 3, 4 is set by the interval l and the number m of the respective cross finger electrodes 3, 4, and a high frequency voltage is applied to the first cross finger electrode 3. upon applying surface acoustic wave _W 1 extending from the first interdigital electrode 3 to the second interdigital finger electrode _{4, W 3, W 5,} W 7 ... W total energy _{P F} of _2n-1 is the second interdigital finger Since it becomes larger than the total energy of the surface acoustic waves W ₂ , W ₄ , W ₆ ,... W _2n directed from the electrode to the first cross finger electrode 3, when the surface acoustic wave is excited by the first cross finger electrode 3 the moving element 5 can be moved by the traveling wave component P _H having a sufficient amount of energy. As described above, in the surface acoustic wave actuator of this embodiment, the movable element 5 can be reliably moved even with low power. This is the same even when a surface acoustic wave is excited by the second cross finger electrode 4. In the above example, the interval l and the number m of sets of the cross finger electrodes 3 and 4 are set so that the reflectance of each cross finger electrode 3 and 4 has a predetermined value. Such adjustment of the reflectivity may be performed by fixing only the value of the interval l while fixing the value of the number of sets m, or changing only the value of the number of sets m while fixing the value of the interval l. You may go by.

  In the surface acoustic wave actuator of the present embodiment described above, the example in which the moving element 5 moves on the stator 1 by fixing the stator 1 has been described. Conversely, by fixing the moving element 5, The stator 1 may be moved. Further, the surface of the stator 1 is not limited to a flat surface, and may be a curved surface such as a spherical surface.

(Embodiment 2)
Similar to the surface acoustic wave actuator of the first embodiment, the surface acoustic wave actuator of the present embodiment includes the stator 1, the moving element 5, and preloading means, but the surface acoustic wave traveling in the same direction. This is different in that a phase adjusting electric circuit unit composed of an inductor L is provided as a phase adjusting means for adjusting the phase of. In addition, since the other structure is the same as that of the said Embodiment 1, the same code | symbol is attached | subjected about the same structure and description is abbreviate | omitted.

As shown in FIG. 3A, the inductor L serving as the phase adjustment electric circuit section is connected between the cross fingers 4 a and 4 b of the second cross finger electrode 4. If thus connecting the inductor L, since the surface acoustic wave phase after reflection against the surface acoustic wave before the reflection is delayed, the reflection position of the over only a surface acoustic wave is left from R _E (first interdigital 3) (direction approaching 3) can be regarded as shifted to _RL . That is, the inductor L changes the phase of the surface acoustic wave according to the impedance value (in particular, the inductance value related to the reactance component value) when the surface acoustic wave is reflected by the crossed finger electrode.

Here, when the phase delay due to the inductance value of the inductor L is φ, surface acoustic waves W ₁ , W ₃ , W ₅ , W ₇ ... W _2n when D and θ satisfy 2D−φλ / 2π = nλ. _-1 can be set to the same phase, and the surface acoustic waves W ₂ , W ₄ , W ₆ ,... W _2n can be set to the same phase, and the distance between the apparent reflection positions R _E and R _{L at} this time Becomes φλ / 4π. The value of 2D−φλ / 2π does not need to be equal to the value of nλ in a strict sense, and may be a value that is approximately equal.

Therefore, even if the distance D between the equivalent reflecting surfaces does not satisfy D≈nλ / 2 (n: integer) described in the first embodiment, the phase delay φ due to the inductance value is 2D−φλ / 2π = nλ. By connecting an inductor L that satisfies the above conditions to the crossed finger electrodes, the surface acoustic waves W ₁ , W ₃ , W ₅ , W ₇ ... W _2n−1 are in phase, and the surface acoustic waves W ₂ , W ₄ , W ₆ ,... W _2n can be in phase.

As described above, in the first embodiment, the value of the distance D between the equivalent reflection surfaces of the crossed finger electrodes 3 and 4 is approximately half of the wavelength λ of the surface acoustic wave excited by the crossed finger electrodes 3 and 4. By setting the value to an integral multiple, the surface acoustic waves W ₁ , W ₃ , W ₅ , W ₇ ... W _2n−1 are in phase, and the surface acoustic waves W ₂ , W ₄ , W ₆ ,. _2n is set to have the same phase, but in this embodiment, by connecting an inductor L, surface acoustic waves W ₁ , W ₃ , W ₅ , W ₇ ... W _{2n−1. Are} set to have the same phase, and the surface acoustic waves W ₂ , W ₄ , W ₆ ,... W _2n have the same phase.

Therefore, according to the surface acoustic wave actuator of the present embodiment, the phase adjustment electric circuit section including the inductor L is provided as the phase adjustment means for adjusting the phase of the surface acoustic wave traveling in the same direction. The surface acoustic wave W ₁ that is excited by the electrode 3 and travels toward the second cross finger electrode 4 and the surface acoustic waves W ₃ and W ₅ that are reflected the same number of times by the cross finger electrodes 3 and 4 and travel toward the second cross finger electrode 4. , W ₇ ... W _2n−1 have the same phase, the surface acoustic wave that is excited by the second cross finger electrode 4 and travels toward the first cross finger electrode 3, and the same number of times at each of the cross finger electrodes 3 and 4. The surface acoustic waves that are reflected and go to the first interdigitated electrode 3 can have the same phase, so that the surface acoustic waves traveling in the same direction are superimposed in the same phase on the stator 1. The surface acoustic wave energy is stored in Effect resulting surface acoustic wave having a standing wave component P _V of size capable of lifting the moving element 5 against the pressure N of the preload means even at low power can be provided to the moving element 5 Play.

By the way, the phase adjusting means is not limited to the above-described inductor L, and an electric circuit portion for phase adjustment composed of a capacitor C can be used. In this case, as shown in FIG. A capacitor C is connected between the cross fingers 4 a and 4 b of the cross finger electrode 4. Thus when connecting the capacitor C, it means that the surface acoustic wave phase after reflected advances against the surface acoustic wave before the reflection, the reflection position of the over only a surface acoustic wave is right from R _E (first It can be considered that it has shifted to _{RC in the} direction away from the cross finger electrode 3. In other words, like the inductor L, when the surface acoustic wave is reflected by the crossed finger electrode, the capacitor C changes the surface acoustic wave phase according to the impedance value (particularly the capacitance value related to the reactance component value). Change.

Here, if the phase lead caused by the capacitance value of the capacitor C and [psi, D and [psi is a surface acoustic wave _{W 1, W 3, W 5} , W 7 ... W 2n-1 when satisfying 2D + ψλ / 2π = nλ The surface acoustic waves W ₂ , W ₄ , W ₆ ,... W _2n can have the same phase, and the apparent distance between the reflection positions R _E and _RC is ψλ / 4π. The value of 2D + ψλ / 2π does not need to be equal to the value of nλ in a strict sense, and may be a value that is approximately equal.

  Therefore, even when the capacitor C is used as the phase adjusting electric circuit section, the same effect as that obtained when the inductor L is used can be obtained.

(Embodiment 3)
In the first embodiment, mainly by setting the reflectances η and γ of the cross finger electrodes 3 and 4, the other cross that does not generate the surface acoustic wave from the one cross finger electrode that generates the surface acoustic wave. total energy P _F of the surface acoustic wave toward the finger electrodes, was set to be greater than the total energy P _R of the is reflected by the other interdigital surface acoustic wave toward the one interdigital However, the present embodiment is characterized in that, as shown in FIG. 4A, in addition to the reflectance γ of each crossed finger electrode, a pressure N applied to the moving element 5 by the preloading means is used. Since other configurations are the same as those of the first embodiment, the same reference numerals are given to the same configurations, and description thereof is omitted. 4A, the cross finger electrodes 3 and 4 are shown in a simplified manner, and the high frequency power sources AC1 and AC2 and the switches SW1 and SW2 are omitted.

  That is, when the surface acoustic wave passes through the portion where the movable element 5 is contacted, the energy of the surface acoustic wave is attenuated by the pressure N, and therefore the pressure N applied to the movable element 5 and the transmittance of the surface acoustic wave. Is as shown in the graph of FIG. That is, as the pressure N increases, the surface acoustic wave transmittance decreases.

Here, in the stator 1, when the high-frequency voltage is applied to the first cross finger electrode 3 by the high-frequency power source AC ₁ to excite the surface acoustic wave W ₁ of energy P, the elasticity due to the pressure N applied to the mover 5. Considering the surface wave attenuation factor α (0 <α <1), the following wave is generated in the stator 1. Note that the reflectance of the first cross finger electrode 3 with respect to the surface acoustic wave having the same frequency as the surface acoustic wave W ₁ is η (0 <η ≦ 1), and the reflectance of the second cross finger electrode 4 is γ (0 <γ ≦ 1). 1), and the surface acoustic wave attenuation on the stator 1 is small, and is ignored.

That is, the surface acoustic wave W ₁ excited by the first cross finger electrode 3 is caused by the pressure N applied to the movable element 5 on the way to the second cross finger electrode 4 as shown in FIG. When the surface acoustic wave W ₁ ′ whose energy is attenuated to αP reaches the second cross finger electrode 4, a part of the surface acoustic wave W ₁ ′ is reflected by the second cross finger electrode 4 toward the first cross finger electrode 3. Thus, the surface acoustic wave W ₂ with energy γαP is obtained. When the surface acoustic wave W ₂ is the energy by the pressure N reaches the Ganmaarufa ^{2 P} surface acoustic wave attenuated W _{2 'next} to the first interdigital finger electrode 3, in part by the first interdigital finger electrode 3 and the second interdigital finger electrode 4 is reflected to become a surface acoustic wave W ₃ having energy γηα ² P. Similarly, the surface acoustic wave W ₃ becomes a surface acoustic wave W ₃ ′ whose energy is attenuated to γηα ³ P by the pressure N, and a part of the surface acoustic wave W ₃ is reflected by the second crossing finger electrode 4 and has an energy γ ² ηα ³ P. towards the first interdigital finger electrode 3 become a wave W _4, and later, such a reflection is repeated.

Therefore, energy _{P F} of the surface acoustic wave traveling from the first interdigital electrode 3 to the second interdigital finger electrode 4 (that is, the traveling wave) _{W F} is the surface acoustic wave _{W 1, W 3, W 5} , W 7 ... W since the energy sum of the _2n-1, a _{P F = P {+ 1 +} γηα 2 (γηα 2) 2 + (γηα 2) 3 + ... + (γηα 2) 2n-1}. Further, from the second interdigital finger electrode 4 energy _{P R} of the surface acoustic wave toward the first interdigital finger electrode 3 (that is, the reflected wave) _{W R} is the surface acoustic wave _{W 2,} W _4, W 6, a ... _{W 2n} since the sum of the energy, the _{P R = γαP {1 + γηα} 2 + (γηα 2) 2 + (γηα 2) 3 + ... + (γηα 2) 2n-1}. Here, the n → ∞, when consideration is γηα ^{2 <1,} energy P _F, the P _R can be expressed by the following equation.

Therefore, the total energy P _S of all waves that are excited in the stator 1 becomes energy P _F of the traveling wave W _F and a total energy P _R of the reflected wave W _R, these traveling wave component P _H is advanced becomes the difference between the energy _{P F} of the wave _{W F} energy _{P R} of the reflected wave _{W R,} standing wave component _{P V} becomes the difference between the total energy _{P S} and the traveling-wave component _{P H,} these _P S, _{P H} , P _V can be expressed as:

As is apparent from the above equation, in the surface acoustic wave actuator of this embodiment, the reflectance η of the first cross finger electrode 3, the reflectance γ of the second cross finger electrode 4, and the attenuation rate α by the preloading means by adjusting the, and it is possible to set the ratio of the incident-wave component P _H and standing wave component P _V, in this embodiment, the energy P _F of the traveling wave W _F is the energy of the reflected wave W _R P _R to be larger than the reflectivity eta, but of setting γ and the attenuation factor alpha, reflectivity eta, setting of γ is the distance l and the set number m of the interdigital as described above as appropriate The attenuation rate α can be set by appropriately setting the value of the pressure N of the preload means as described above. At this time, the value of the reflectance γ attenuation rate α, relative energy _{P F} of the traveling wave _{W F,} as energy _{P R} of the reflected wave _{W R} becomes 0.5 times 0.98 times or less It is preferable to set, and referring to the above equation 4, it is sufficient that 0.5 ≦ γα ≦ 0.98.

According to the surface acoustic wave actuator of the present embodiment described above, the ratio of the incident-wave component P _H and standing wave component P _V of the surface acoustic wave excited on the stator 1, a surface acoustic wave by the preload means for receiving the impact of the attenuation factor alpha, by changing the value of the pressure N contacting the moving element 5 to the stator 1 by pre-pressurizing section, the incident-wave component P _H and standing wave component P _V by the preload means The ratio can be set, and thus there is an effect that the ratio of these components P _H and P _V can be finely adjusted even after the crossed finger electrodes 3 and 4 are formed on the stator 1.

(Embodiment 4)
In the first and third embodiments, the first cross finger electrode 3 and the second cross finger electrode 4 are both general cross finger electrodes as shown in FIG. When a high-frequency voltage is applied to the finger electrode, not only in a desired direction (in the first cross finger electrode 3 shown in FIG. 1A, the right direction on the second cross finger electrode 4 side), but also in a direction other than the desired direction The surface acoustic wave is also excited in the direction opposite to the desired direction, for example, the direction opposite to the desired direction (left side in FIG. 1A).

  Therefore, the present embodiment is characterized in that, as shown in FIG. 5A, instead of the crossed finger electrodes 3 and 4, crossed finger electrodes 6 and 7 including reflection electrodes 61 and 71 are provided. The distance between the equivalent reflective surfaces of the first cross finger electrode 6 and the second cross finger electrode 7 is substantially an integral multiple of the half wavelength of the surface acoustic wave excited by the cross finger electrodes 6 and 7, as in the first embodiment. Is set so that the energy of the surface acoustic wave is accumulated on the stator 1. In addition, since the other structure is the same as that of Embodiment 1, the same code | symbol is attached | subjected about the same structure and description is abbreviate | omitted. In FIG. 5A, the cross finger electrodes 6 and 7 are shown in a simplified manner, and the high frequency power sources AC1 and AC2 and the switches SW1 and SW2 are omitted.

  The first interdigitated electrode 6 is an excitation electrode 60 and a reflection electrode serving as a reflection part that reflects, in a desired direction, a surface acoustic wave that travels in a direction other than a desired direction among the surface acoustic waves excited by the excitation electrode 60. 61, the amplitude of the surface acoustic wave excited in a desired direction (the right direction in FIG. 5A) is larger than the amplitude of the surface acoustic wave excited in a direction other than the desired direction. A unidirectional electrode configured to be large. As shown in FIG. 5 (b), the excitation electrode 60 is a so-called comb-like electrode (IDT) having a shape in which a plurality of pairs of cross fingers 60a and 60b having different polarities are arranged at predetermined intervals. 5A, it is formed on one end side in the longitudinal direction of the surface of the piezoelectric substrate 2 (left end side in FIG. 5A). Like the excitation electrode 60, the reflection electrode 61 has a shape in which a plurality of pairs of crossing fingers 61a and 61b having different polarities are arranged at predetermined intervals, as shown in FIG. Further, it is formed on one end side in the longitudinal direction of the surface of the piezoelectric substrate 2 with respect to the excitation electrode 60. The cross finger 60a of the excitation electrode 60 is connected to one end of the external high frequency power supply AC1, and the cross finger 60b is connected to the other end of the high frequency power supply AC1.

  On the other hand, the second cross finger electrode 7 is a unidirectional electrode having an excitation electrode 70 and a reflection electrode 71, similarly to the first cross finger electrode 6. Like the excitation electrode 60, the excitation electrode 70 has a shape in which a plurality of pairs of cross fingers 70a and 70b having different polarities are arranged at a predetermined interval, as shown in FIG. 5 (a). It is formed on the other end side in the longitudinal direction of the surface of the piezoelectric substrate 2 (right end side in FIG. 5A). Similar to the excitation electrode 70, the reflection electrode 71 has a shape in which a plurality of pairs of crossing fingers 71a and 71b having different polarities are arranged at predetermined intervals, as shown in FIG. 5 (a). It is formed on the other end side in the longitudinal direction of the surface of the piezoelectric substrate 2 with respect to the excitation electrode 70.

Hereinafter, such a unidirectional electrode will be described by taking the first cross finger electrode 6 as an example. First, the excitation electrode 60 is set in the same manner as in the first embodiment. For example, the interval l between the crossed fingers of the same polarity is set to 132.64 μm and the number m of pairs is set to 20, and FIG. as shown in a), with the resonance frequency is 28.9MHz, the reflectance is set to be _{R a.}

Although then it performs setting of the reflection electrode 61, and the surface acoustic wave W _a proceeding right is excited at excitation electrodes 60, respectively P / 2 energy of the surface acoustic wave W _b proceeding to the left, excitation the reflectivity R _a of use electrode _60, the reflectivity of the reflective electrode 61 and R _B, the energy of the sum of the surface acoustic wave traveling from the first interdigital electrode 6 to the right side, P / 2 + [(1- R _A ) R _B / {2 (1-R _A R _B )}] P. Here, as R _B approaches 1, the said the first interdigital finger electrode 6 of the formula of energy of the sum of the surface acoustic wave traveling to the right closer to P, the reflective electrode 61, the excitation electrodes 60 The reflectance with respect to the surface acoustic wave excited by is preferably closer to 1. Therefore, the interval l and the number m of the reflecting electrodes 61 may be set so that the surface acoustic wave having a frequency of 28.9 MHz has a reflectance close to 1 by simulation. For example, the interval l is set to 136.5 μm. , when the number of sets m and 40, as shown by _{R B} in FIG. 6 (a), the reflective electrode has a reflectance of 0.999 with respect to the surface acoustic wave having a frequency of 28.9MHz 61 Can be obtained. Incidentally, the reflectance of the excitation electrode 60 with respect to the surface acoustic wave having a frequency of 28.9 MHz is about 0.20 with reference to FIG. Here, the reflectance _RT as the entire first interdigitated electrode 6 is given by the following equation and is as shown in FIG.

  In this way, the excitation electrode 60 and the reflection electrode 61 in which the interval l and the number of sets m are set are arranged on the piezoelectric substrate 2 with a predetermined interval therebetween. Here, when the distance between the electrodes 60 and 61 is changed, when the distance becomes substantially an integer multiple of a half wavelength of the surface acoustic wave excited by the excitation electrode 60, The result shows that the admittance with respect to the high-frequency current at the drive frequency becomes the maximum value. This is because the surface acoustic wave is excited by the excitation electrode 60 and travels to the second cross finger electrode 7, and the elasticity is reflected by the reflection electrode 61 after being excited by the excitation electrode 60 and travels to the second cross finger electrode 7. This is because the surface wave and the same phase overlap each other and current flows easily. Therefore, the distance between the electrodes 60 and 61 is preferably the above-described distance.

In this way, the first cross finger electrode 6 is designed and the second cross finger electrode 7 is designed in the same manner. However, the excitation electrode 70 and the reflection electrode 71 of the second cross finger electrode 7 are designed. respective spacing l and the set number m of, when the same value as the first interdigital finger electrode 6, the reflectance _{R T} of each interdigital electrodes 6, 7 for example with respect to a surface acoustic wave having a frequency 28.9MHz, 0.999 since the, and greatly reduced the traveling wave component P _H, the surface acoustic wave energy required to move the moving element 5 is insufficient, it may be impossible to move the moving element 5.

  Therefore, in the excitation electrode 70 and the reflection electrode 71 of the second intersecting finger electrode 7, the interval l and the number of sets m are set as follows. In other words, the resonance frequency of the excitation electrode 70 is set to a value at which the reflectance becomes low at the first crossed finger electrode 6, and the interval l and the number of sets m are set so as to have a low reflectance with respect to the frequency of 28.9 MHz. Set. For example, the interval 1 between the crossed fingers of the same polarity is set to 133.84 μm and the number m of sets is set to 20, so that the resonance frequency of the excitation electrode 70 is 28.64 MHz.

  Next, the reflective electrode 71 is set in the same manner as the first cross finger electrode 6. The reflection electrode 71 preferably has a reflectance close to 1 with respect to the surface acoustic wave excited by the excitation electrode 70, and therefore has a reflectance close to 1 with respect to a surface acoustic wave having a frequency of 28.64 MHz by simulation. In this way, the interval l and the number m of the reflecting electrodes 71 are set. For example, by setting the interval l to about 137.69 μm and the number of sets m to 40, it is possible to obtain the reflecting electrode 71 having a reflectance of 0.999 for a surface acoustic wave having a frequency of 28.64 MHz.

The first interdigital electrode 6 and the second interdigital finger electrode 7 is designed as above, the frequency characteristics of the reflectivity R _U reflectance R _T and the second interdigital finger electrode 7 of the first interdigital finger electrode 6, The values are as shown in the graph of FIG. As is apparent from the graph of FIG. 6B, the first cross finger electrode 6 has a reflectance of about 1 with respect to the surface acoustic wave having a frequency of 28.9 MHz that is excited by itself. The surface acoustic wave having a frequency of 28.64 MHz excited by the finger electrode 7 has a reflectance of about 0.64. The second cross finger electrode 7 also has a reflectance of about 1 for a surface acoustic wave having a frequency of 28.64 MHz excited by itself, and has a frequency of 28.9 MHz excited by the first cross finger electrode 6. The surface acoustic wave has a reflectance of about 0.64.

Accordingly, upon applying a predetermined high frequency voltage to the excitation electrodes 60 of the first interdigital finger electrode 6, as shown in FIG. 5 (b), the surface acoustic wave W _a and the left proceeding from the excitation electrode 60 on the right and the surface acoustic wave _{W b} proceeding is excited, these surface acoustic wave _W a, _{W b} are both have an energy of a frequency and P / 2 of 28.9MHz. In the first and second embodiments, the surface acoustic wave _Wb is directly propagated to the left end portion of the piezoelectric substrate 2 to become heat and wasted, but in the present embodiment, the reflective electrode 61 is provided. reflected to the right can be effectively utilized by the reflection electrode 61 surface acoustic wave W _b. Therefore, with the same power, it is possible to excite a surface acoustic wave having energy twice as large as that of the first and second embodiments by the first interdigitated electrode 6. This also applies to the second cross finger electrode 7.

Further, by setting the interval l so that the respective cross finger electrodes 6 and 7 have different resonance frequencies, the frequency at which the second cross finger electrode 7 is excited by the first cross finger electrode 6 is 28.9 MHz. because it has a reflectivity of 0.64 with respect to the surface acoustic wave, when obtained by exciting the first interdigital finger electrode 6, enough of the standing wave component P _V traveling wave component P _A surface acoustic wave having _H can be applied to the movable element 5. Similarly, since the first cross finger electrode 6 has a reflectance of about 0.64 for a surface acoustic wave having a frequency of 28.64 MHz excited by the second cross finger electrode 7, the second cross finger electrode 6 has a reflectivity of about 0.64. even when allowed to excite the finger electrodes 7, it is possible to provide a surface acoustic wave having a traveling wave component P _H and the standing wave component P _V large enough to the moving element 5.

As described above, according to the surface acoustic wave actuator of the present embodiment, in addition to the same advantages as those of the first embodiment, the interdigitated electrodes 6 and 7 formed of a unidirectional electrode including an excitation electrode and a reflection electrode. Can be used to excite a surface acoustic wave having approximately twice the energy of the interdigitated electrodes 3 and 4 of the first embodiment, thereby preloading means even at a lower power than in the first embodiment. it can provide a surface acoustic wave having a magnitude of the standing wave component P _V which can oscillate against the pressure N of the moving element 5. Moreover by varying the resonant frequency in each interdigital electrodes 6 and 7, to suppress the reduction of the traveling wave component P _H due to reflected waves, so that sufficient traveling wave component P _H to move the moving element 5 is obtained Therefore, the mover 5 can be reliably moved.

  By the way, the configuration of the unidirectional electrode is not limited to the above, and for example, as shown in FIG. The unidirectional electrode 80 shown in FIG. 7A is composed of an excitation electrode 81 and a reflection electrode 82, and the excitation electrode 81 and the reflection electrode 82 are the excitation electrode 60 and the reflection electrode described above. The electrode 61 is the same as the electrode 61 except that the reflecting electrode 82 is formed in a ladder shape instead of a cross finger shape.

  Another configuration of the unidirectional electrode may be as shown in FIG. As shown in FIG. 7B, the unidirectional electrode 83 includes an excitation electrode 84 in which a plurality of pairs of cross fingers 84a and 84b having different polarities are arranged at predetermined intervals, and the excitation electrode 84. And the reflecting electrode 85 provided at a portion between the adjacent cross fingers 84a and 84b. Here, the reflecting electrode 85 is formed of a U-shaped or I-shaped electrode group arranged in a row at a predetermined interval.

Alternatively, a unidirectional electrode 86 as shown in FIGS. 7C and 7D can be used. The unidirectional electrode 86 includes an excitation electrode 87 made of an Al film in which a plurality of pairs of cross fingers 87a and 87b having different polarities are arranged at predetermined intervals, and each of the cross fingers 84a and 84a of the excitation electrode 84. And a reflecting portion 88 made of a SiO ₂ film formed on the piezoelectric substrate 2 so as to cover the left portion between 84b.

  The unidirectional electrodes 80, 83, and 86 shown in FIGS. 7A to 7D have different configurations, but the operation is the same as that of the crossed finger electrodes 6 and 7 of the present embodiment. Therefore, the description is omitted.

(Embodiment 5)
As shown in FIG. 8A, the surface acoustic wave actuator according to the present embodiment is disposed to face the piezoelectric substrate 2 and the surface of the piezoelectric substrate 2 at a predetermined distance, and generates surface acoustic waves on the piezoelectric substrate 2. A stator 1 having a pair of crossed finger electrodes 6A and 7A to be moved, a mover 5 placed on the surface of the piezoelectric substrate 2 and moved by the surface acoustic wave, and the mover 5 to the stator 1. Prestressing means (not shown) for contact with pressure N, and each interdigital electrode 6A, 7A has excitation electrodes 62, 72 and reflection electrodes 63, 73. 72 is connected to high-frequency AC power supplies AC1 and AC2, respectively, and the reflection electrodes 63 and 73 are electric circuit sections serving as reflectance adjustment means for adjusting the reflectance of the interdigital electrodes 6A and 7A with respect to the surface acoustic waves, respectively. Z1 and Z2 are connected . In addition, about the structure similar to the said Embodiment 4, the same code | symbol is attached | subjected and description is abbreviate | omitted. For simplification of the drawing, the crossed finger electrodes 6A and 7A are shown in a simplified manner in FIG. This also applies to FIGS. 9 to 13.

  The first interdigitated electrode 6A is a unidirectional electrode composed of an excitation electrode 62 and a reflection electrode 63, and one end side in the longitudinal direction of the surface of the piezoelectric substrate 2 as shown in FIG. It is formed on the left end side in FIG. The excitation electrode 62 is a comb-like electrode having a shape in which a plurality of pairs of crossing fingers 62a and 62b having different polarities are arranged at predetermined intervals in the same manner as the excitation electrode 60 described above. A high frequency power supply AC1 is connected between the 62 crossing fingers 62a and 62b via the switch SW11. The reflection electrode 63 is a comb-like electrode having a shape in which a plurality of pairs of crossing fingers 63 a and 63 b having different polarities are arranged at a predetermined interval in the same manner as the excitation electrode 62. Between the fingers 62a and 62b, the electric circuit portion Z1 is connected via the switch SW12.

  On the other hand, the second cross finger electrode 7A is a unidirectional electrode composed of an excitation electrode 72 and a reflection electrode 73 as in the case of the first cross finger electrode 6A. As shown in FIG. It is formed on the other end side in the longitudinal direction of the surface of the piezoelectric substrate 2 (right end side in FIG. 8A). The excitation electrode 72 is a comb-like electrode having a shape in which a plurality of pairs of cross fingers 72 a and 72 b having different polarities are arranged at predetermined intervals in the same manner as the excitation electrode 62. A high frequency power supply AC2 is connected between the switches 72a and 72b via the switch SW21. The reflection electrode 73 is a comb-like electrode having a shape in which a plurality of pairs of cross fingers 73 a and 73 b having different polarities are arranged at a predetermined interval in the same manner as the excitation electrode 72. Between the fingers 73a and 73b, the electric circuit portion Z2 is connected via the switch SW22.

  In the first cross finger electrode 6A, as in the case of the first cross finger electrode 6 of the third embodiment, the interval l between the excitation electrode 62 and the reflection electrode 63 and the number m of sets are set. On the other hand, the second cross finger electrode 7A is different from the second cross finger electrode 7 of the third embodiment, and the interval l between the excitation electrode 72 and the reflection electrode 73 and the number m of sets are determined by the first cross finger electrode 6A. The distance between the excitation electrode 62 and the reflection electrode 73 is set to the same value as the distance l and the number m of sets.

  Therefore, in the surface acoustic wave actuator of this embodiment, the excitation electrodes 62 and 72 of the crossed finger electrodes 6A and 7A are set to have the same resonance frequency, and the excitation electrodes 62 and 72 are excited. The reflectivity of the crossed finger electrodes 6A and 7A with respect to the surface acoustic wave is set to be approximately 1.

  The electric circuit portions Z1 and Z2 are reflectance adjusting electric circuit portions that change the reflectance of the interdigital electrodes 6A and 7A with respect to the surface acoustic wave in accordance with the value of the impedance. For example, resistors are used. The electric circuit portions Z1 and Z2 are switched between connection / disconnection to the corresponding reflection electrodes 63 and 73 by turning on / off the switches SW12 and SW22.

  Here, as shown in FIG. 8 (b), it is simulated that the reflectance with respect to the surface acoustic wave having a frequency near the resonance frequency of the cross finger electrode can be reduced by connecting a resistor between the cross fingers of the cross finger electrode. The result is obtained. In the graph indicated by R1 in FIG. 8B, the interval l and the number of sets m are such that the resonance frequency is 15 MHz and the surface acoustic wave having a frequency near the resonance frequency has a reflectance close to 1. It is a graph showing the reflectance characteristics of the crossed finger electrodes that are set (for example, the interval l = 277.8 μm, the number of sets m = 30), and the graph indicated by R2 is a predetermined resistance between the crossed fingers of the crossed finger electrodes. It is a graph which shows the reflectance characteristic at the time of connecting the resistor which has a value (for example, 100 ohms).

  As apparent from FIG. 8B, when a resistor is connected between the cross fingers of the cross finger electrode, the reflectance in the vicinity of the resonance frequency of the cross finger electrode is reduced (for example, resonance). It can be seen that the reflectance with respect to frequency is 0.84).

  That is, in the surface acoustic wave actuator of the present embodiment, when the switch SW12 is off, the electric circuit portion Z1 is not connected to the reflecting electrode 63, and thus the second crossed finger electrode 7A in the reflecting electrode 63 is used. The reflectance for the surface acoustic wave excited by is about 1. On the other hand, when the switch SW12 is on, the electrical circuit portion Z1 is connected to the reflecting electrode 63, so that the reflectivity for the surface acoustic wave excited by the second crossed finger electrode 7A in the reflecting electrode 63 is reduced. Will be.

  Further, when the switch SW22 is off, the electrical circuit portion Z2 is not connected to the reflecting electrode 73, and therefore the reflectance of the reflecting electrode 73 with respect to the surface acoustic wave excited by the second crossed finger electrode 6A is It becomes approximately 1. On the other hand, when the switch SW22 is on, the electrical circuit portion Z2 is connected to the reflecting electrode 73, so that the reflectance with respect to the surface acoustic wave excited by the first crossed finger electrode 6A in the reflecting electrode 73 is reduced. Will be.

  The operation of the surface acoustic wave actuator of this embodiment will be described below. Here, in the initial state, it is assumed that the switches SW11, SW12, SW21, and SW22 are all off.

  When the moving element 5 is moved to the first cross finger electrode 6A side, by turning on the switches SW11 and SW22 from the initial state, the driving voltage of the high-frequency power source AC1 is applied to the excitation electrode of the first cross finger electrode 6A. High-frequency voltage) and the electric circuit portion Z2 may be connected to the reflecting electrode 73 of the second crossing finger electrode 7A. In this case, as described above, the reflectance of the second cross finger electrode 7A with respect to the surface acoustic wave excited by the excitation electrode 62 is reduced, so that the first cross finger electrode 6A is directed to the second cross finger electrode 7A as described above. The total energy of the surface acoustic waves is larger than the total energy of the surface acoustic waves reflected by the second cross finger electrode 7A and directed to the first cross finger electrode 6A. As a result, the movable element 5 moves to the first cross finger. It moves to the electrode 6A side.

  On the other hand, when the moving element 5 is moved to the second crossing finger electrode 7A side, the switches SW12 and SW21 are turned on from the initial state to drive the high frequency power supply AC2 to the excitation electrode of the second crossing finger electrode 7A. A voltage (high-frequency voltage) may be applied, and the electric circuit portion Z1 may be connected to the reflecting electrode 63 of the first interdigitated electrode 6A. In this case, the reflectance of the first cross finger electrode 6A with respect to the surface acoustic wave excited by the excitation electrode 72 is reduced, so that the second cross finger electrode 7A is directed to the first cross finger electrode 6A as described above. The total energy of the surface acoustic waves is larger than the total energy of the surface acoustic waves reflected by the first cross finger electrode 6A and directed to the second cross finger electrode 7A. As a result, the movable element 5 moves to the second cross finger. It moves to the electrode 7A side.

  That is, in the surface acoustic wave actuator of this embodiment, the switch 5 can be moved to the first cross finger electrode 6A side by turning on the switches SW11 and SW22 and turning off the switches SW12 and SW21. , SW22 is turned off and switches SW12, SW21 are turned on, so that the movable element 5 can be moved to the second crossing finger electrode 7A side.

  As described above, according to the surface acoustic wave actuator of the present embodiment, in addition to the same advantages as those of the fourth embodiment, the reflectance of each crossed finger electrode 6A, 7A is determined by connecting / disconnecting the electric circuit portions Z1, Z2. Since the reflectance with respect to the surface acoustic wave excited by the opposing cross-finger electrodes in the pair of cross-finger electrodes 6 and 7 does not become approximately 1, as in the fourth embodiment, the cross-finger electrodes 6 and 6 can be easily changed. Thus, there is no need to design the interval l of 7 or the number m of sets, and the surface acoustic wave actuator can be easily designed.

  By the way, in the above example, an example is shown in which resistors are used as the electric circuit portions Z1 and Z2. However, such electric circuit portions Z1 and Z2 include coils (inductors) and capacitors (capacitors) in addition to the resistors. ) May be used. In this case, as described in the second embodiment, when the surface acoustic wave is reflected by the interdigitated electrodes to which the electric circuit portions Z1 and Z2 are connected, the phase of the surface acoustic wave is changed to each electric circuit portion Z1, It can be changed according to the impedance value of Z2. Thereby, for example, instead of setting the distance D between the equivalent reflection surfaces of the crossed finger electrodes 6A and 7A, the phase of the surface acoustic wave traveling in the same direction can be changed by changing the phase according to the impedance values of the electric circuit portions Z1 and Z2. Settings can be made so that the phases are the same. In addition, when the total amount of waves is large, it is possible to suppress the total amount of waves by shifting the phase of the surface acoustic waves traveling in the same direction by changing the phase of the surface acoustic waves by the electric circuit portions Z1 and Z2. Become.

  Further, the configuration of the interdigitated electrodes 6A and 7A is not limited to the above, and for example, as shown in FIGS. 9A to 9E. In FIGS. 9A to 9E, the high-frequency power supply AC1, the electric circuit unit Z2, and the switches SW11, SW12, SW21, and SW22 are not shown.

  In the example shown in FIG. 9A, the number of sets of the excitation electrodes 62 and 72 and the reflection electrodes 63 and 73 of the crossed finger electrodes 6A and 7A is different. In the example shown in FIG. The difference is that the electric circuit portion Z2 is connected to the excitation electrode 62 instead of the reflection electrode 63. In the example shown in FIG. 9C, the configuration of the reflecting electrodes 63 and 73 of the crossed finger electrodes 6A and 7A is different, and a pair of crossed fingers is taken as one set, and a pair of crossed fingers having different polarities is used. It has a shape that is alternately arranged. In the example shown in FIG. 9D, the same one as the unidirectional electrode 83 made up of the excitation electrode 84 and the reflection electrode 85 shown in FIG. 7B is used instead of the crossed finger electrodes 6A and 7A. In the example shown in FIG. 9 (e), instead of the interdigitated electrodes 6A and 7A, a unidirectional electrode 86 composed of the excitation electrode 87 and the reflecting portion 88 shown in FIGS. 7 (c) and 7 (d) The same thing is adopted.

  The examples of the surface acoustic wave actuators shown in FIGS. 9A to 9E are all different in configuration, but their operations are the same as those of the surface acoustic wave actuator of the present embodiment, and the description thereof is omitted. To do.

  On the other hand, in the surface acoustic wave actuator shown in FIG. 8A, the high-frequency power sources AC1 and AC2 and the electric circuit portions Z1 and Z2 are provided on the interdigitated electrodes 6A and 7A, respectively. Z1 may be shared by the cross finger electrodes 6A and 7A.

  In this case, as shown in FIGS. 10A and 10B, wiring is performed between the pair of cross finger electrodes 6A and 7A, the high-frequency power source AC1, and the electric circuit portion Z1. That is, in the surface acoustic wave actuator shown in FIGS. 10A and 10B, the crossing finger 62a of the excitation electrode 62 of the first crossing finger electrode 6A is connected to the first contact SW31a of the first changeover switch SW31, and the reflection is performed. The cross finger 63a of the electrode 63 is connected to the second contact SW32b of the second switch SW32, and the cross finger 72a of the excitation electrode 72 of the second cross finger electrode 7A is connected to the second contact SW31b of the first switch SW31. The crossing finger 73a of the reflecting electrode 73 is connected to the first contact SW32b of the second changeover switch SW32. Further, the cross fingers 62b, 63b, 72b, 73b of the electrodes 62, 63, 72, 73 are connected to one end of the high frequency power supply AC1 and one end of the electric circuit unit Z1, and the other end of the high frequency power supply AC1 is connected to the first changeover switch SW31. And the other end of the electric circuit portion Z1 is connected to the second changeover switch SW32.

  In this case, by switching the first changeover switch SW31 to the first contact SW31a side, the high frequency power supply AC1 is connected to the excitation electrode 62 of the first crossed finger electrode 6A, and the first changeover switch SW31 is moved to the second contact SW31b side. By switching, the high frequency power supply AC1 is connected to the excitation electrode 72 of the second crossed finger electrode 7A. Further, by switching the second changeover switch SW32 to the first contact SW32a side, the electric circuit portion Z1 is connected to the reflection electrode 73 of the second crossed finger electrode 7A, and the second changeover switch SW32 is set to the second contact SW32b side. By switching, the electric circuit portion Z1 is connected to the reflecting electrode 63 of the first crossed finger electrode 6A.

  Therefore, as shown in FIG. 10A, by switching the changeover switches SW31 and SW32 to the first contacts SW31a and SW32a, respectively, the drive voltage of the high-frequency power supply AC1 is applied to the excitation electrode 62 of the first crossed finger electrode 6A. (High-frequency voltage) is applied, and the electric circuit portion Z1 is connected to the reflecting electrode 73 of the second crossing finger electrode 7A. In this case, as described above, the reflectance of the second cross finger electrode 7A with respect to the surface acoustic wave excited by the excitation electrode 62 is reduced, so that the first cross finger electrode 6A is directed to the second cross finger electrode 7A as described above. The total energy of the surface acoustic waves is larger than the total energy of the surface acoustic waves reflected by the second cross finger electrode 7A and directed to the first cross finger electrode 6A. As a result, the movable element 5 moves to the first cross finger. It moves to the electrode 6A side.

  On the other hand, as shown in FIG. 10B, by switching the changeover switches SW31 and SW32 to the second contacts SW31b and SW32b, respectively, the drive voltage of the high frequency power supply AC1 is applied to the excitation electrode 72 of the second crossing finger electrode 7A. (High-frequency voltage) is applied, and the electric circuit portion Z1 is connected to the reflecting electrode 63 of the first interdigitated electrode 6A. In this case, as described above, the reflectance of the second cross finger electrode 7A with respect to the surface acoustic wave excited by the excitation electrode 62 is reduced, so that the first cross finger electrode 6A is directed to the second cross finger electrode 7A as described above. The total energy of the surface acoustic waves is larger than the total energy of the surface acoustic waves reflected by the second cross finger electrode 7A and directed to the first cross finger electrode 6A. As a result, the movable element 5 moves to the first cross finger. It moves to the electrode 6A side.

  That is, in the surface acoustic wave actuator shown in FIGS. 10A and 10B, the movable element 5 is moved to the first cross finger electrode 6A side by switching the changeover switches SW31 and SW32 to the first contact SW31a and SW32a side. The movable element 5 can be moved to the second crossing finger electrode 7A side by switching the changeover switches SW31 and SW32 to the second contact points SW31b and SW32b.

  In such a surface acoustic wave actuator, unlike the example shown in FIG. 8A, the high-frequency power supply AC1 and the electric circuit portion Z1 are shared by the crossed finger electrodes 6A and 7A, so that the number of parts can be reduced and the manufacturing can be performed. Cost can be reduced.

  By the way, in the surface acoustic wave actuator of this embodiment, resistors are used as the impedance adjustment impedance elements in the electric circuit portions Z1 and Z2 serving as the reflectance adjustment means. Instead of using the resistors, the impedance value ( In particular, a variable resistor which is a reflectance adjusting impedance element capable of adjusting a resistance value related to the resistance component R [Ω] of the impedance Z [Ω] of the variable impedance unit 90 may be used. In this case, there is an effect that the reflectance can be adjusted more easily by the electric circuit portions Z1 and Z2.

(Embodiment 6)
As shown in FIG. 11A, the surface acoustic wave actuator of this embodiment is different from the surface acoustic wave actuator of the above-described embodiment 5 in that electric circuit portions Z3 and Z4 are provided. Since it is the same as that of the said Embodiment 5, the same code | symbol is attached | subjected about the same structure and description is abbreviate | omitted.

  Here, the electric circuit portions Z3 and Z4 are both resistors like the electric circuit portions Z1 and Z2, and the electric circuit portion Z3 is the cross fingers 62a and 62b of the excitation electrode 62 of the first cross finger electrode 6A. The electrical circuit unit Z4 is connected between the cross fingers 72a and 72b of the excitation electrode 72 of the second cross finger electrode 7A via the switch SW23. For this reason, the electrical circuit portions Z3 and Z4 are switched between connection / disconnection to the excitation electrodes 62 and 72 by turning on / off the switches SW13 and SW23, respectively.

  Therefore, in this surface acoustic wave actuator, when the switches SW12 and SW13 are off, the electric circuit portion Z1 is not connected to the reflecting electrode 63, and the electric circuit portion Z3 is not connected to the excitation electrode 62. The reflectance of the first cross finger electrode 6A with respect to the surface acoustic wave excited by the second cross finger electrode 7A is approximately 1.

  On the other hand, when the switch SW12 is turned on from the state in which both the switches SW12 and SW13 are off, the electric circuit portion Z1 is connected to the reflecting electrode 63, so that the second cross finger electrode 7A in the reflecting electrode 63 is The reflectance with respect to the excited surface acoustic wave is reduced. Further, when the switch SW13 is turned on, since the electric circuit portion Z3 is connected to the excitation electrode 62, the reflectance with respect to the surface acoustic wave excited by the second crossed finger electrode 7A in the excitation electrode 62 is reduced, As a result, the reflectance of the first cross finger electrode 6A with respect to the surface acoustic wave excited by the second cross finger electrode 7A is further reduced.

  As described above, in the surface acoustic wave actuator according to the present embodiment, the reflectance of the first cross finger electrode 6A with respect to the surface acoustic wave excited by the second cross finger electrode 7A can be adjusted by the combination of the switches SW12 and SW13 that are turned on. It can be done. Since this point is the same on the second crossing finger electrode 7A side, the description thereof is omitted.

  The operation of the surface acoustic wave actuator of this embodiment will be described below. Here, in the initial state, it is assumed that the switches SW11 to 13 and SW21 to 23 are off.

  When the movable element 5 is moved to the first cross finger electrode 6A side, by turning on the switches SW11 and SW22 from the initial state, the drive voltage of the high frequency power source AC1 is applied to the excitation electrode of the first cross finger electrode 6A. In addition, the electric circuit portion Z2 may be connected to the reflecting electrode 73 of the second crossing finger electrode 7A.

  In this case, as described above, the reflectance of the second cross finger electrode 7A with respect to the surface acoustic wave excited by the excitation electrode 62 is reduced, so that the first cross finger electrode 6A is directed to the second cross finger electrode 7A as described above. The total energy of the surface acoustic waves is larger than the total energy of the surface acoustic waves reflected by the second cross finger electrode 7A and directed to the first cross finger electrode 6A. As a result, the movable element 5 moves to the first cross finger. It moves to the electrode 6A side.

  Further, by turning on the switch SW23 in addition to the switch SW22, the electric circuit portion Z4 may be connected to the excitation electrode 72 of the second crossed finger electrode 7A. In this case, the excitation electrode 62 is excited. The reflectance of the second cross finger electrode 7A with respect to the surface acoustic wave is further reduced. As a result, the sum of the surface acoustic wave energy from the first cross finger electrode 6A toward the second cross finger electrode 7A is reflected by the second cross finger electrode 7A and the energy of the surface acoustic wave toward the first cross finger electrode 6A. As a result, the moving speed of the movable element 5 toward the first crossing finger electrode 6A can be increased as compared with the case where only the switch SW22 is turned on.

  On the other hand, when the moving element 5 is moved to the second crossing finger electrode 7A side, the switches SW21 and SW12 are turned on from the initial state to drive the high frequency power supply AC2 to the excitation electrode of the second crossing finger electrode 7A. A voltage may be applied and the electric circuit portion Z1 may be connected to the reflecting electrode 63 of the first crossed finger electrode 6A.

  In this case, the reflectance of the first cross finger electrode 6A with respect to the surface acoustic wave excited by the excitation electrode 72 is reduced, so that the second cross finger electrode 7A is directed to the first cross finger electrode 6A as described above. The total energy of the surface acoustic waves is larger than the total energy of the surface acoustic waves reflected by the first cross finger electrode 6A and directed to the second cross finger electrode 7A. As a result, the movable element 5 moves to the second cross finger. It moves to the electrode 7A side.

  Further, by turning on the switch SW13 in addition to the switch SW12, the electric circuit portion Z3 may be connected to the excitation electrode 62 of the first crossed finger electrode 6A. In this case, the excitation electrode 72 is excited. Thus, the reflectance of the first cross finger electrode 6A with respect to the surface acoustic wave to be reduced is further reduced. As a result, the sum of the surface acoustic wave energy from the second cross finger electrode 7A toward the first cross finger electrode 6A is reflected by the first cross finger electrode 6A and the energy of the surface acoustic wave toward the second cross finger electrode 7A. As a result, the moving speed of the movable element 5 toward the second crossing finger electrode 7A can be increased as compared with the case where only the switch SW12 is turned on.

  That is, in the surface acoustic wave actuator of this embodiment, the switch 5 can be moved to the first cross finger electrode 6A side by turning on the switches SW11 and SW22 and turning off the switches SW12 and SW21. Further, the moving speed of the moving element 5 can be increased by turning on the switch SW23. In the surface acoustic wave actuator of this embodiment, the switch 5 can be moved to the second crossing finger electrode 7A side by turning off the switches SW11 and SW22 and turning on the switches SW12 and SW21. Further, the moving speed of the moving element 5 can be increased by turning on the switch SW13.

  As described above, according to the surface acoustic wave actuator of this embodiment, in addition to the advantages similar to those of the fifth embodiment, not only the connection / disconnection of the electric circuit portions Z1 and Z2, but also the electric circuit portions Z3 and Z4. Since the reflectance of each cross finger electrode 6A, 7A can be changed also by connection / disconnection, there exists an effect that the freedom degree of adjustment of a reflectance increases.

  In addition, as described in the fifth embodiment, the electrical circuit portions Z1 to Z4 may be configured to change the phase of the surface acoustic wave by using one having a coil or a capacitor in addition to the resistance, In this case, there is an effect that the degree of freedom of phase adjustment is increased.

  In the above example, the first cross finger electrode 6A is provided with the high frequency power source AC1 and the electric circuit portions Z1 and Z3, and the second cross finger electrode 7A is provided with the high frequency power source AC2 and the electric circuit portions Z2 and Z4. The high frequency power supply AC1 and the electric circuit portions Z1 and Z3 may be shared by the crossed finger electrodes 6A and 7A.

  In this case, as shown in FIG. 11B, wiring is performed between the pair of crossed finger electrodes 6A and 7A, the high frequency power supply AC1, and the electric circuit portions Z1 and Z3. Here, in the surface acoustic wave actuator shown in FIG. 11B, in addition to the configuration shown in FIGS. 10A and 10B described in the fifth embodiment, the excitation electrode 72 of the second crossed finger electrode 7A. The first contact SW33a of the third changeover switch SW33 is connected between the crossing finger 72a of the first changeover switch SW31 and the crossing finger 62a of the excitation electrode 62 of the first crossing finger electrode 6A. Between the first contact SW31a of the first changeover switch SW31, the second contact SW33b of the third changeover switch SW33 is connected. Further, one end of the electric circuit unit Z3 is connected to the cross fingers 62b, 63b, 72b, 73b of the electrodes 62, 63, 72, 73, and the third changeover switch SW33 is connected to the other end of the electric circuit unit Z3. . Note that the third changeover switch SW33 has a third contact (not shown), and switches to the third contact when the electric circuit unit Z3 is not used.

  In this case, like the surface acoustic wave actuator shown in FIGS. 10A and 10B, the high frequency power supply AC1 is connected to the excitation electrode 62 or the excitation electrode 72 in accordance with the switching operation of the first changeover switch SW31. The electric circuit portion Z1 is connected to the reflection electrode 73 or the reflection electrode 63 in accordance with the switching operation of the second changeover switch SW32.

  Further, by switching the third changeover switch SW33 to the first contact SW33a side, the electric circuit portion Z3 is connected to the excitation electrode 72 of the second crossed finger electrode 7A, and the third changeover switch SW33 is set to the second contact SW33b side. By switching, the electric circuit portion Z3 is connected to the excitation electrode 63 of the first interdigitated electrode 6A.

  The operation of the surface acoustic wave actuator shown in FIG. 11B will be described below. In this surface acoustic wave actuator, as shown in FIG. 11B, when the changeover switches SW31 and SW32 are switched to the first contacts SW31a and SW32a, respectively, the excitation electrode 62 of the first crossed finger electrode 6A. The driving voltage of the high frequency power supply AC1 is applied to the electric circuit portion Z1 and the electric circuit portion Z1 is connected to the reflecting electrode 73 of the second crossed finger electrode 7A.

  In this case, as described above, the reflectance of the second cross finger electrode 7A with respect to the surface acoustic wave excited by the excitation electrode 62 is reduced, so that the first cross finger electrode 6A is directed to the second cross finger electrode 7A as described above. The total energy of the surface acoustic waves is larger than the total energy of the surface acoustic waves reflected by the second cross finger electrode 7A and directed to the first cross finger electrode 6A. As a result, the movable element 5 moves to the first cross finger. It moves to the electrode 6A side.

  When the third changeover switch SW33 is further changed to the first contact SW33a from this state, the electric circuit portion Z3 is connected to the excitation electrode 72 of the second crossed finger electrode 7A. The reflectance of the second interdigitated electrode 7A with respect to the surface acoustic wave excited by the electrode 62 is further reduced. As a result, the sum of the surface acoustic wave energy from the first cross finger electrode 6A toward the second cross finger electrode 7A is reflected by the second cross finger electrode 7A and the energy of the surface acoustic wave toward the first cross finger electrode 6A. Thus, the moving speed of the movable element 5 toward the first cross finger electrode 6A is increased.

  On the other hand, when the changeover switches SW31 and SW32 are switched to the second contacts SW31b and SW32b, respectively, the driving voltage of the high frequency power supply AC1 is applied to the excitation electrode 72 of the second crossing finger electrode 7A, and the first The electric circuit portion Z1 is connected to the reflecting electrode 63 of the interdigitated electrode 6A.

  In this case, the reflectance of the first cross finger electrode 6A with respect to the surface acoustic wave excited by the excitation electrode 72 is reduced, so that the second cross finger electrode 7A is directed to the first cross finger electrode 6A as described above. The total energy of the surface acoustic waves is larger than the total energy of the surface acoustic waves reflected by the first cross finger electrode 6A and directed to the second cross finger electrode 7A. As a result, the movable element 5 moves to the second cross finger. It moves to the electrode 7A side.

  When the third selector switch SW33 is further switched to the second contact SW33b from this state, the electric circuit portion Z3 is connected to the excitation electrode 62 of the first crossed finger electrode 6A. In this case, the excitation circuit The reflectance of the first interdigitated electrode 6A with respect to the surface acoustic wave excited by the electrode 72 is further reduced. As a result, the sum of the surface acoustic wave energy from the second cross finger electrode 7A toward the first cross finger electrode 6A is reflected by the first cross finger electrode 6A and the energy of the surface acoustic wave toward the second cross finger electrode 7A. Thus, the moving speed of the moving element 5 toward the second crossing finger electrode 7A is increased.

  That is, in the surface acoustic wave actuator shown in FIG. 11B, the movable element 5 can be moved to the first cross finger electrode 6A side by switching both the changeover switches SW31 and SW32 to the first contact SW31a and SW32a side. In addition, the moving speed of the moving element 5 can be increased by switching the third changeover switch SW33 to the first contact SW33a. Further, by switching both changeover switches SW31, SW32 to the second contact SW31b, SW32b side, the movable element 5 can be moved to the second crossing finger electrode 7A side, and in addition, the third changeover switch SW33 is set to the second contact point. The moving speed of the mover 5 can be increased by switching to SW33b.

  In such a surface acoustic wave actuator, unlike the example shown in FIG. 11A, the high frequency power supply AC1 and the electric circuit portions Z1 and Z3 are shared by the crossed finger electrodes 6A and 7A. In addition, the manufacturing cost can be reduced.

(Embodiment 7)
In the surface acoustic wave actuator of this embodiment, as shown in FIGS. 12A and 12B, the connection state between the high-frequency power supply AC1 and the electric circuit unit Z1 is the same as that shown in FIGS. The configuration is different from the surface acoustic wave actuator shown in b), and the other configurations are the same as those in the fifth embodiment. Therefore, the same configurations are denoted by the same reference numerals and the description thereof is omitted.

  That is, in the surface acoustic wave actuator of this embodiment, as shown in FIGS. 12A and 12B, the cross fingers 62a and 72a of the excitation electrodes 62 and 72 of the cross finger electrodes 6A and 7A are connected to the high frequency power supply AC1. Is connected to the first contact SW4a of the changeover switch SW4, and the crossing finger 63a of the reflection electrode 63 is connected to the second contact SW4b of the changeover switch SW4. Further, the cross fingers 62b, 63b, 72b, 73b of the electrodes 62, 63, 72, 73 are connected to the other end of the high-frequency power source AC1 and one end of the electric circuit unit Z1, and the other end of the electric circuit unit Z1 is connected to the changeover switch SW4. Connected to.

  In this case, the high frequency power supply AC1 is connected to both the excitation electrode 62 of the first cross finger electrode 6A and the excitation electrode 72 of the second cross finger electrode 7A, and switches the changeover switch SW4 to the first contact SW4a side. Thus, the electric circuit portion Z1 is connected to the reflection electrode 73 of the second crossing finger electrode 7A, and the changeover switch SW4 is switched to the second contact SW4b side, whereby the reflection electrode 63 of the first crossing finger electrode 6A is electrically connected. The circuit part Z1 is connected.

  Hereinafter, the operation of the surface acoustic wave actuator of this embodiment will be described. First, in the surface acoustic wave actuator, a driving voltage is applied to both excitation electrodes 62 and 72 from the high frequency power supply AC1. Therefore, when the surface acoustic waves are excited by the respective excitation electrodes 62 and 72 and the electric circuit portion Z1 is not connected to either of the reflection electrodes 63 and 73, the excitation electrodes 62 and 72 are excited. The reflectance of the first cross finger electrode 6A with respect to the surface acoustic wave to be generated and the reflectance of the second cross finger electrode 7A with respect to the surface acoustic wave excited by the excitation electrodes 62 and 72 are approximately 1. In this case, the sum of the surface acoustic wave energy from the first cross finger electrode 6A to the second cross finger electrode 7A and the sum of the surface acoustic wave energy from the second cross finger electrode 7A to the first cross finger electrode 6A Are substantially equal, and as a result, the movable element 5 does not move in any direction.

  Here, as shown in FIG. 12A, when the changeover switch SW4 is switched to the first contact SW4a side, the electric circuit portion Z1 is connected to the reflection electrode 73 of the second crossing finger electrode 7A. As a result, the reflectance of the second interdigitated electrode 7A with respect to the surface acoustic wave excited by the excitation electrodes 62 and 72 is reduced. Thereby, the total sum of the surface acoustic wave energy from the first cross finger electrode 6A toward the second cross finger electrode 7A is greater than the total sum of the surface acoustic wave energy from the second cross finger electrode 7A toward the first cross finger electrode 6A. As a result, the mover 5 moves to the first cross finger electrode 6A side.

  On the other hand, as shown in FIG. 12B, when the changeover switch SW4 is switched to the second contact SW4b side, the electric circuit portion Z1 is connected to the reflecting electrode 63 of the first crossed finger electrode 6A. The reflectance of the first interdigitated electrode 6A with respect to the surface acoustic wave excited by the excitation electrodes 62 and 72 is reduced. As a result, the sum of the surface acoustic wave energy from the second cross finger electrode 7A toward the first cross finger electrode 6A is greater than the sum of the surface acoustic wave energy from the first cross finger electrode 6A toward the second cross finger electrode 7A. As a result, the moving element 5 moves to the second crossing finger electrode 7A side.

  That is, in the surface acoustic wave actuator shown in FIGS. 12A and 12B, the movable element 5 can be moved to the first crossing finger electrode 6A side by switching the changeover switch SW4 to the first contact SW4a side. By switching the changeover switch SW4 to the second contact SW4b side, the movable element 5 can be moved to the second crossing finger electrode 7A side.

  As described above, according to the surface acoustic wave actuator of the present embodiment, in addition to the same advantages as those of the fifth embodiment, the changeover switch for the high-frequency power supply AC1 as compared with the case shown in FIGS. 10 (a) and 10 (b). Therefore, it is possible to further reduce the number of parts and the manufacturing cost.

(Embodiment 8)
As shown in FIG. 13, the surface acoustic wave actuator of the present embodiment has the same configuration as the surface acoustic wave actuator of the fifth embodiment, but instead of having the electric circuit portions Z1 and Z2, an electric circuit It differs in having the portions 9A and 9B. In addition, about the structure similar to the surface acoustic wave actuator of the said Embodiment 5, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 14, the electric circuit unit 9A includes a variable impedance unit 90 whose impedance value can be adjusted, a speed detection unit 91, a phase detection unit 92, a phase difference calculation unit 93, an input unit 94, and an arithmetic operation. Part 95.

  The variable impedance unit 90 is a variable resistance that is a reflectance adjustment impedance element that can adjust an impedance value (particularly, a resistance value related to the resistance component R [Ω] of the impedance Z [Ω] of the variable impedance unit 90). 90a and a variable capacitor 90b in which an impedance value (particularly, a capacitance value related to the value of the reactance component X [Ω] of the impedance Z of the variable impedance unit 90) can be adjusted. The impedance Z of the unit 90 is given by R + iX (where i is an imaginary unit).

  Such a variable impedance unit 90 is connected to the reflecting electrode 63. Instead of the variable capacitor 90b, a variable coil capable of adjusting an inductance value related to the value of the reactance component X [Ω] of the impedance Z of the variable impedance unit 90 may be used as the impedance value.

  The speed detector 91 includes, for example, a speed sensor (not shown) using the Doppler effect, and detects the moving speed of the moving element 5 (relative speed of the moving element 5 with respect to the stator 1). Is output to the arithmetic unit 95. The phase detection unit 92 detects the phase of vibration (indicated by V1 in FIG. 15) in the surface portion M of the stator 1 and is configured to output the detection value to the phase difference calculation unit 93. Yes. The phase difference calculation unit 93 calculates a phase difference θ between the phase of the vibration V1 detected by the phase detection unit 92 and the phase of the high frequency voltage (indicated by V2 in FIG. 15) of the high frequency power supply AC1. The phase difference is output to the calculation unit 95. The input unit 94 is a user interface for inputting a target value of the moving speed of the moving element 5 and a target value of the phase difference θ, and each of the input moving speed target value of the moving element 5 and the phase difference θ. Are output to the calculation unit 95.

  The calculation unit 95 is configured using, for example, a CPU, and includes a reflectance control unit 95a and a phase difference control unit 95b. Here, the reflectance control unit 95a is configured so that the speed of the moving element 5 obtained from the detection value of the speed detecting unit 91 matches the target value of the moving speed of the moving element 5 obtained from the input unit 94. The resistance value of 90a (that is, the value of the resistance component R of the impedance Z of the variable impedance unit 90) is feedback-controlled.

  The phase control unit 95b has a capacitance value (that is, variable impedance) of the variable capacitor 90b so that the phase difference θ obtained from the phase difference calculation unit 93 matches the target value of the phase difference θ obtained from the input unit 94. The value of the reactance component X of the impedance Z of the unit 90 is feedback-controlled. By the way, the phase difference θ also affects the speed of the moving element 5. That is, when the phase difference θ is brought close to 0, 2π, 4π,..., The total energy of the surface acoustic waves traveling in the same direction can be increased, and the speed of the moving element 5 can be increased. When approaching 5π, the total energy of the surface acoustic wave traveling in the same direction is reduced, and the speed of the movable element 5 can be reduced. Therefore, by inputting the value of the phase difference θ that causes the moving element 5 to move at the target value speed, the phase control unit 95b can maintain the moving element 5 at the target value.

  In the above example, the user needs to input the phase difference θ so that the speed of the moving element 5 becomes a target value while measuring the speed of the moving element 5. Therefore, the speed of the moving element 5 detected by the speed detection unit 91 and the target value of the speed input to the input unit 94 are transmitted to the phase control unit 95b, and the speed detection is performed to the phase control unit 95b. If the function of adjusting the phase difference θ is provided so that the speed of the movable element 5 obtained by the unit 91 becomes the target value obtained by the input part 94, the speed of the movable element 5 is provided in the input part 94. It is possible to cause the phase control unit 95b to control the speed of the moving element 5 only by inputting the target value.

  The electric circuit unit 9A is configured as described above. According to the electric circuit unit 9A, the speed of the movable element 5 can be set to a desired value, and the phase difference θ is set to a desired value. Thus, the surface acoustic waves traveling in the same direction can be set to have the same phase.

  That is, the electric circuit unit 9A sets the reflectance of the cross finger electrode 6A with respect to the surface acoustic wave excited by the cross finger electrode 7A to a predetermined value, thereby setting the velocity of the movable element 5 to the target value. By setting the function as an electric circuit unit and the phase difference θ to a desired value, the speed of the moving element 5 is set to a target value, or the surface acoustic wave traveling in the same direction is set to have the same phase. It has a function as an electric circuit part for phase adjustment.

  On the other hand, the electric circuit unit 9B has the same configuration as the electric circuit unit 9A, but the variable impedance unit is connected to the reflecting electrode 73 of the second crossing finger electrode 7A and the phase difference calculation. 13 is configured to calculate a phase difference between the phase of vibration (indicated by V1 in FIG. 15) at the surface portion of the stator 1 indicated by M in FIG. 13 and the phase of the high-frequency voltage of the high-frequency power source AC2. It is different in that it is. Since the other configuration is the same as that of the electric circuit portion 9A, the description is omitted.

  As described above, according to the surface acoustic wave actuator of this embodiment, the relative speed of the moving element 5 with respect to the stator 1 can be set to a desired value. For this reason, the driving characteristics of the surface acoustic wave actuator deteriorate due to long-term operation or deterioration over time (for example, the driving force decreases due to wear of the contact portion between the moving element 5 and the stator 1), and the movement Even when the speed of the child 5 has decreased, the speed of the moving element 5 can be prevented from being reduced due to such deterioration of driving characteristics, etc., by adjusting the speed of the moving element 5 by the reflectance control unit 95a. There is an effect. Moreover, the speed reduction of the moving element 5 as described above is not limited to when the drive characteristics are deteriorated, but for example, pressure fluctuation due to preload means due to assembly error, manufacturing error, etc. This may also occur due to variation in dimensions and the surface roughness of the stator depending on the location. In these cases as well, the speed of the movable element 5 can be adjusted by the reflectance control unit 95a. Speed reduction can be prevented. As described above, according to the reflectance control unit 95a, the speed of the moving element 5 is maintained at the target value, so that the speed of the moving element 5 decreases due to various causes such as deterioration of driving characteristics and assembly errors. Can be prevented.

  Furthermore, according to the surface acoustic wave actuator of this embodiment, the phase difference θ between the phase of the vibration V1 at the surface portion M of the stator 1 and the phase of the high-frequency voltage (shown as V2 in FIG. 15) of the high-frequency power supply AC1. Can be set to a desired value. Therefore, when the operation is performed for a long time or due to aging deterioration or the like, the driving characteristics of the surface acoustic wave actuator are deteriorated (for example, a decrease or variation in the pressure N due to deterioration of the preload means), and the elastic surface traveling in the same direction. Even when a phase shift occurs between the waves, it is possible to eliminate such a phase shift by adjusting the phase difference θ by the phase control unit 95b, and thereby the movement caused by the phase shift. There is an effect that the speed reduction of the child 5 can be prevented. In addition, the phase shift as described above is not limited to when the drive characteristics are deteriorated. For example, the pressure variation due to the preload means due to the assembly error or the manufacturing error, or the variation in the dimensions of the interdigital electrodes due to the manufacturing error. The surface roughness of the stator may vary depending on the location, but in these cases as well, by adjusting the phase difference θ by the phase controller 95b, a decrease in the speed of the movable element 5 can be prevented. . As described above, according to the phase control unit 95b, the speed of the moving element 5 is maintained at the target value by adjusting the phase of the surface acoustic wave traveling in the same direction. It is possible to prevent the speed of the moving element 5 from being lowered due to various causes.

  On the other hand, in the surface acoustic wave actuator according to the present embodiment, it is possible to prevent the speed of the moving element 5 from being lowered due to various causes such as deterioration of driving characteristics and assembly errors as described above. Can be controlled to the speed desired by the user. The speed of the movable element 5 can be adjusted in accordance with the usage status of the surface acoustic wave actuator, for example, the device using the surface acoustic wave actuator, and thus the surface acoustic wave actuator can be used for various applications.

  Note that the electric circuit unit 9A is not limited to that shown in FIG. 14, and includes, for example, only the variable resistor 90a, the speed detection unit 91, the input unit 94, and the reflectance control unit 95a of the calculation unit 95. It is also possible to use a reflectance adjusting electric circuit unit that can adjust only the speed of the moving element 5.

  The electric circuit unit 9A includes, for example, a variable capacitor 90b, a phase detection unit 92, a phase difference calculation unit 93, an input unit 94, and a phase control unit 95b of the calculation unit 95. A phase adjustment electric circuit unit capable of adjusting only the phase difference θ may be used. This also applies to the electric circuit portion 9B. In addition, instead of providing the electric circuit portions 9A and 9B for the crossed finger electrodes 6A and 7A, the electric circuit portion 9A may be shared by both the crossed finger electrodes 6A and 7A.

(A) is a schematic explanatory drawing of the surface acoustic wave actuator of Embodiment 1 of this invention, (b) is a perspective view of a moving element, (c) is description of the principal part of a surface acoustic wave actuator. FIG. (A) is a graph which shows the frequency characteristic of the reflectance of the cross finger electrode of Embodiment 1 of this invention, (b) is the frequency characteristic of the reflectance at the time of changing the number of sets of a cross finger electrode. It is a graph which shows a change, (c) is a graph which shows the relationship between the number of sets of a cross finger electrode, and the maximum value of a reflectance. (A) is a schematic explanatory drawing of the surface acoustic wave actuator of Embodiment 2 of this invention, (b) is a schematic explanatory drawing which shows another example. (A) is a schematic explanatory drawing of the surface acoustic wave actuator of Embodiment 3 of this invention, (b) is a graph which shows the relationship between the pressure of a preload means, and the transmittance | permeability of a surface acoustic wave. (A) is a schematic explanatory drawing of the surface acoustic wave actuator of Embodiment 4 of this invention, (b) is explanatory drawing of the principal part. (A) is a graph which shows the frequency characteristic of the reflectance of the cross finger electrode of Embodiment 4 of this invention, (b) is a graph which shows the frequency characteristic of the reflectance of both cross finger electrodes. (A)-(c) is a partial top view which shows the other example of the cross finger electrode of Embodiment 4 of this invention, (d) is a fragmentary sectional view of the figure (c). (A) is a schematic explanatory drawing of the surface acoustic wave actuator of Embodiment 5 of this invention, (b) is a graph which shows the change of the frequency characteristic of the reflectance at the time of connecting resistance to a cross finger electrode. . (A)-(e) is a schematic explanatory drawing which shows the other example of the cross finger electrode of Embodiment 5 of this invention. (A), (b) is a schematic explanatory drawing which shows the other example of the surface acoustic wave actuator of Embodiment 5 of this invention. (A) is a schematic explanatory drawing of the surface acoustic wave actuator of Embodiment 6 of this invention, (b) is a schematic explanatory drawing which shows the other example of the surface acoustic wave actuator of Embodiment 6 of this invention. . (A), (b) is a schematic explanatory drawing of the surface acoustic wave actuator of Embodiment 7 of this invention. It is a schematic explanatory drawing of the surface acoustic wave actuator of Embodiment 8 of this invention. It is a block diagram of an electric circuit part. It is explanatory drawing which shows the phase difference of the phase of the high frequency voltage applied to the electrode for excitation, and the phase of the vibration of the stator surface detected by a phase detection part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stator 2 Piezoelectric substrate 3 1st cross finger electrode 4 2nd cross finger electrode 5 Mover N Pressure

Claims (13)

  A piezoelectric substrate, a stator having a pair of crossed finger electrodes disposed opposite to the surface of the piezoelectric substrate at a predetermined distance and exciting a surface acoustic wave on the piezoelectric substrate, and the elastic material mounted on the surface of the piezoelectric substrate A movable body that is moved by surface waves; and a preload means that brings the movable element into contact with the stator at a predetermined pressure. The pair of crossed finger electrodes are arranged to face the surface acoustic waves excited by the opposed crossed finger electrodes. A surface acoustic wave actuator configured to reflect toward a crossing finger electrode, the phase acoustic wave actuator including phase adjusting means for adjusting the phase of the surface acoustic wave traveling in the same direction.   A piezoelectric substrate, a stator having a pair of crossed finger electrodes disposed opposite to the surface of the piezoelectric substrate at a predetermined distance and exciting a surface acoustic wave on the piezoelectric substrate, and the elastic material mounted on the surface of the piezoelectric substrate A movable body that is moved by surface waves; and a preload means that brings the movable element into contact with the stator at a predetermined pressure. The pair of crossed finger electrodes are arranged to face the surface acoustic waves excited by the opposed crossed finger electrodes. The surface acoustic wave actuator is configured to reflect the crossed finger electrode, and the distance between the equivalent reflective surfaces of the pair of crossed finger electrodes is equal to the half-wavelength of the surface acoustic wave generated by each crossed finger electrode. A surface acoustic wave actuator characterized by being set to a value substantially equal to an integral multiple.   The interval between the cross fingers of the cross finger electrodes or the number of a pair of cross fingers having different polarities from each other is set so that the reflectance of the cross finger electrodes with respect to the surface acoustic wave becomes a predetermined value. The surface acoustic wave actuator according to claim 1, wherein the surface acoustic wave actuator is provided.   The phase adjusting means is an electric circuit unit for phase adjustment that is connected to the cross finger electrode and changes the phase of the surface acoustic wave according to the impedance value when the surface finger is reflected by the cross finger electrode. The surface acoustic wave actuator according to claim 1, wherein the surface acoustic wave actuator is provided.   5. The surface acoustic wave actuator according to claim 4, wherein the phase adjustment electric circuit section includes a phase adjustment impedance element capable of adjusting an impedance value. 6.   6. The phase adjustment electric circuit section includes a phase control section that sets the impedance value of the phase adjustment impedance element so that the speed of the moving element becomes a target value. Surface acoustic wave actuator.   The surface acoustic wave actuator according to claim 1, further comprising a reflectance adjusting unit that adjusts the reflectance of the cross finger electrode with respect to the surface acoustic wave.   The reflectivity adjusting means is an electrical circuit unit for adjusting the reflectivity, which is connected to the cross finger electrode and changes the reflectivity of the cross finger electrode with respect to the surface acoustic wave according to the impedance value. 8. The surface acoustic wave actuator according to 7.   9. The surface acoustic wave actuator according to claim 8, wherein the reflectance adjusting electric circuit section includes a reflectance adjusting impedance element capable of adjusting an impedance value.   10. The reflectance adjustment electric circuit section includes a reflectance control section that sets an impedance value of the reflectance adjustment impedance element so that the speed of the moving element becomes a target value. The surface acoustic wave actuator described in 1.   11. The pressure value at which the moving element is brought into contact with the stator by the preloading means is set so that the attenuation rate of the surface acoustic wave by the preloading means becomes a predetermined value. 2. The surface acoustic wave actuator according to item 1.   The surface acoustic wave actuator according to any one of claims 1 to 11, further comprising switching means for switching a cross finger electrode that is a connection destination of a power source that applies a driving voltage to the cross finger electrode. The cross finger electrode is a unidirectional electrode including a reflecting portion that reflects a surface acoustic wave traveling in a direction other than a desired direction in a desired direction. Surface acoustic wave actuator.

Images