WO2012118101A1 - Angular velocity sensor - Google Patents

Abstract

This angular velocity sensor is provided with: an oscillator having a first drive arm and a second drive arm; a first drive element that oscillates the first drive arm; a second drive element that oscillates the second drive arm; a control unit, which makes the first drive arm and the second drive arm oscillate by outputting signals to the first drive element and the second drive element; and a detection unit, which detects oscillation from the first drive arm and the second drive arm. The control unit executes control in normal mode and self-diagnosis mode with respect to the first drive element and the second drive element.

Description

Angular velocity sensor

The present invention relates to an angular velocity sensor capable of self-diagnosis of a failure.

Conventionally, as an angular velocity sensor for detecting the angular velocity of an object or its sensor element, extremely weak vibration and displacement generated due to Coriolis force, which is a kind of inertial force generated when rotation is applied to a vibrating mass body. Is detected through a detecting means such as a piezoelectric element, and rotation and movement in each direction are detected and measured.
Such angular velocity sensors are widely used in technologies for autonomously controlling the attitude of automobiles, ships, airplanes, rockets, etc., and recently, small-sized car navigation systems, digital cameras, video cameras, game machines, mobile phones, etc. It has come to be installed in electronic devices.
Along with this, there has been a demand for further enhancement of sensitivity, thickness reduction, miniaturization and durability of angular velocity sensors, and various angular velocity sensors using piezoelectric thin film elements formed by microfabrication technology have been proposed to meet this demand. Has been.

A so-called tuning fork type angular velocity sensor having a vibrating arm (a drive arm and a detection arm) is known as an angular velocity sensor using a piezoelectric thin film element that is thin and small as described above.
However, such a tuning-fork type angular velocity sensor has a malfunction or deterioration in function due to breakage of each vibrating arm or damage including short circuit and disconnection of a drive or detection piezoelectric element and a circuit connected to each piezoelectric element. It tends to cause such troubles.

In order to prevent such problems, for example, Patent Document 1 discloses a vibrating body including a pair of tuning fork-shaped drive plates and a detection plate provided so as to be orthogonal to the tips of the pair of drive plates. Driving means provided on the driving plate for driving and vibrating the vibrating body, and detecting means provided on the detection plate for obtaining an angular velocity output generated in a direction orthogonal to the driving direction of the vibrating body. Detecting the mechanical coupling signal resulting from the mechanical coupling of the detection plate and the drive plate by the detecting means, and self-diagnosis of the occurrence of the failure in the angular velocity sensor without providing a separate means for generating the mechanical coupling signal A mechanism for this is described.

Japanese Laid-Open Patent Publication No. 8-327363

However, in the angular velocity sensor described in the above-mentioned conventional patent document 1, since the phase of the mechanical leakage vibration is in phase with the phase of the drive amplitude, a special vibration detection circuit for self-diagnosis of the failure is required. To do.
Therefore, it is difficult to determine a failure in a normal Coriolis detection circuit only with the angular velocity sensor of Patent Document 1. Therefore, if a special detection circuit is added, there is a high possibility that the special detection circuit itself will fail.

Accordingly, the present invention has been made in view of the above circumstances, and provides an angular velocity sensor that can operate in a self-diagnosis mode that detects the presence or absence of a failure in the angular velocity sensor without providing a special vibration detection circuit. Objective.

In the manufacture of an angular velocity sensor using a piezoelectric thin film element, extremely high processing accuracy is required for the arrangement mode of the piezoelectric thin film element and the dimension of the tuning fork on which the piezoelectric thin film element is arranged. Accordingly, in manufacturing a so-called minute angular velocity sensor having a very thin film thickness and a small surface area, it is required to make the shape and installation balance of each vibrating arm constituting the tuning fork as designed, and the piezoelectric thin film element. It is required to maintain the position of
However, it is extremely difficult to maintain such high accuracy when manufacturing a fine angular velocity sensor.
Therefore, when high accuracy is not maintained, for example, the X-direction vibration of the driving arm constituting the tuning fork leaks to the detection arm side, or the driving arm is not limited to vibration along the ideal xy plane. Directional vibrations also occurred.
In the normal angular velocity detection operation, such leakage vibrations are in phase and are canceled as a result. However, the angular velocity can be reduced by devising driving of the driving arm that is the source of this vibration. The present inventors have noticed that vibration having a phase difference similar to that at the time of detection can be generated.
The present invention has been made based on such findings.

In order to solve the above problems, an angular velocity sensor according to the present invention is provided on a tuning fork type vibrator having a first drive arm and a second drive arm, and provided on the first drive arm so as to vibrate along a drive plane. A first drive element for exciting the first drive arm; a second drive element provided on the second drive arm for exciting the second drive arm so as to vibrate along the drive plane; the first drive element and the first drive element; A control unit that outputs a drive signal to each of the two drive elements, vibrates the first drive arm and the second drive arm, detects vibrations from the first drive arm and the second drive arm, and inputs them to the vibrator. An angular velocity sensor that detects an angular velocity of the first drive arm, and the control unit includes a second drive arm for the first drive arm and the second drive arm with the same period and the same amplitude, respectively. Drive the first drive element and the second drive element so that their vibration phases are opposite to each other. The normal mode for outputting a signal, the first drive arm and the second drive arm have the same period and the same amplitude, and the vibration phase of the second drive arm with respect to the first drive arm is shifted from the opposite phase while the same phase is In order to avoid this, a self-diagnosis mode for outputting a drive signal to the first drive element and the second drive element is executed.

In the angular velocity sensor of the present invention having such a configuration, the first drive arm of the vibrator is provided with the first drive element, and the second drive arm is provided with the second drive element. The arm and the second drive arm can be excited to vibrate along the drive plane.
When an angular velocity is input to this vibrator, a force in a direction perpendicular to the drive plane is generated by the Coriolis force, and the first drive arm and the second drive arm vibrate in a direction perpendicular to the drive plane. In the normal mode, the angular velocity input to the vibrator is obtained by driving the first drive arm and the second drive arm with the same period and the same amplitude, and the vibration phases of each other being opposite to each other. It can be detected accurately.

By the way, since the first drive arm is provided with the first drive element and the second drive arm is provided with the second drive element, the first drive arm and the second drive arm are vibrated for the above-described manufacturing reasons. Even in the state where the angular velocity is not input to the child, the driving vibration in the vibration plane direction and the minute vibration generated in the direction orthogonal to the vibration plane are leaked to the detection unit.
The present invention is configured so that self-diagnosis can be performed by utilizing so-called “leakage vibration” that leaks to the detection unit even when the angular velocity is not input.
Specifically, the first drive arm and the second drive arm have the same period and the same amplitude, and are driven so that the vibration phases of the first drive arm and the second drive arm deviate from the opposite phase but do not become the same phase. Thus, the detection unit is configured to detect a pseudo angular velocity.
It is possible to self-diagnose whether or not a failure has occurred in the functional units constituting the angular velocity detection device depending on whether or not the pseudo angular velocity appears constantly.

Also, the angular velocity sensor configured in this way does not require an additional vibration detection circuit and special control means in order to perform self-diagnosis of the failure, so that the assembly accuracy in the manufacture of the angular velocity sensor is improved and the manufacturing cost is increased. Is reduced.
In addition, since the total number of constituent means necessary as an angular velocity sensor with a self-diagnosis function is suppressed, the risk of aging failure is also reduced.

An angular velocity sensor according to the present invention includes a base connected to a first drive arm and a second drive arm, and a pair of detections connected to positions where the connection between the first drive arm and the second drive arm is opposed to the base. It is also possible to provide a configuration in which vibrations generated in the drive arm are propagated through the base and detected by the pair of detection arms.

The angular velocity sensor configured in this way is driven through the base so that drive vibration in the drive plane and vibration in a direction perpendicular to the drive plane due to Coriolis force are extremely small compared to the drive vibration. Since the arm and the detection arm are separated from each other, it is possible to improve detection sensitivity and accuracy.

The angular velocity sensor according to the present invention can be configured to detect vibration generated in the drive arm with the drive arm.

Since the angular velocity sensor constructed in this way does not require a detection arm, the area of the angular velocity sensor itself is reduced, and the angular velocity sensor can be further reduced in size. Further, since the drive arm and the detection arm are the same, it is possible to more directly detect the vibration caused by the Coriolis force generated in the drive arm.

The angular velocity sensor according to the present invention can be configured to further include a determination circuit for diagnosing the angular velocity sensor as a failure when it is determined that the detected vibration signal does not exist within a specified numerical range.

The angular velocity sensor configured as described above can easily perform self-diagnosis of malfunctions occurring in the angular velocity sensor such as malfunction and functional deterioration, and the determination result is exchanged for the angular velocity sensor or a sensor package provided with the angular velocity sensor. It can be used as an index for maintenance time.

In the angular velocity sensor according to the present invention, the control unit can be configured to advance or delay the drive timing of the first drive arm, or both, and / or the drive timing of the second drive arm. Both can be configured to be advanced or delayed, or both.

The angular velocity sensor configured as described above does not need to be additionally provided with a dedicated circuit for detecting a failure, and is driven only by shifting the vibration timing of the first drive arm and / or the second drive arm. In addition, it is possible to accurately grasp whether or not a malfunction has occurred in the angular velocity sensor, and it is possible to easily perform self-diagnosis of the angular velocity sensor.

Each of the first and second drive arms is provided with two drive elements provided at equal intervals on the upper surface with a center line extending in the extending direction of each of the first and second drive arms as a boundary. You may comprise so that it may have.

The angular velocity sensor configured as described above has a driving element only on the upper surface of the driving arm, so that slight vibration is generated in the thickness direction of the angular velocity sensor, thereby positively acting on the angular velocity sensor. It is possible to apply leakage vibration in the Z direction.
Therefore, even when the angular velocity sensor does not cause leakage vibration due to other factors, it is possible to perform a self-diagnosis of the failure of the angular velocity sensor using the leakage vibration.

As described above, the angular velocity sensor according to the present invention includes a tuning fork type vibrator having a first drive arm and a second drive arm, and the first drive arm provided on the first drive arm so as to vibrate along the drive plane. A first drive element for exciting the drive arm; a second drive element provided on the second drive arm for exciting the second drive arm so as to vibrate along the drive plane; the first drive element and the second drive element; And a control unit that vibrates the first driving arm and the second driving arm, detects vibrations from the first driving arm and the second driving arm, and determines an angular velocity input to the vibrator. A detecting unit that detects the first driving arm and the second driving arm with the same period and the same amplitude, and the vibration phase of the second driving arm with respect to the first driving arm is opposite to the first driving arm. The normal mode for outputting the drive signal to the first drive element and the second drive element, and the first drive The first drive element and the second drive arm have the same period and the same amplitude, and the vibration phase of the second drive arm with respect to the first drive arm does not become the same phase while shifting from the opposite phase. Since the self-diagnosis mode in which the drive signal is output to the drive element is executed, a pseudo angular velocity can be detected by the detection unit using so-called “leakage vibration”.
Then, it is possible to self-diagnose whether or not a failure has occurred in the functional units constituting the angular velocity detection device depending on whether or not the pseudo angular velocity appears constantly.
In addition, the angular velocity sensor configured as described above does not require an additional vibration detection circuit and special control means in order to perform self-diagnosis of a failure, and the total number of constituent means necessary as an angular velocity sensor with a self-diagnosis function. This reduces the risk of aging failure.

FIG. 1 is a block diagram showing the configuration of a control circuit applicable to the angular velocity sensor according to the present invention. FIG. 2 is a block diagram showing a configuration of a control circuit applicable to the angular velocity sensor according to the present invention. FIG. 3 is a perspective view showing the configuration of the angular velocity sensor according to the first embodiment. 4 is an enlarged front view of the base of the angular velocity sensor shown in FIG. FIG. 5 is an XZ plane cross-sectional view of the VV cross section in FIG. 4 near the connection portion with the base portion of the drive arm of the angular velocity sensor according to the first embodiment. 6 is an XZ plane cross-sectional view of the VI-VI cross section in FIG. 4 in the vicinity of the connection portion with the base of the detection arm of the angular velocity sensor according to the first embodiment. FIG. 7 is a perspective view showing the operating principle of the angular velocity sensor according to the first embodiment. FIG. 8 is a diagram showing the behavior of an ideal virtual angular velocity sensor without leakage vibration for each operation mode. FIG. 9 is a schematic top view of the behavior of the driving arm in one cycle in an ideal virtual angular velocity sensor without leakage vibration observed from the + Y direction. FIG. 10 is a schematic top view of the behavior of the driving arm in one cycle in an ideal virtual angular velocity sensor without leakage vibration observed from the + Y direction. FIG. 11 is a diagram illustrating the behavior of the angular velocity sensor having leakage vibration in the X direction for each operation mode. FIG. 12 is an enlarged view of a waveform showing the deviation of the timing of applying vibration to the left and right drive arms in the self-diagnosis mode. FIG. 13 is a diagram illustrating the behavior of the angular velocity sensor having leakage vibration in the Z direction for each operation mode. FIG. 14 is a schematic top view of the behavior of the driving arm in one cycle in the angular velocity sensor having leakage vibration in the Z direction, observed from the + Y direction. FIG. 15 is a schematic top view of the behavior of the driving arm in one cycle in the angular velocity sensor having leakage vibration in the Z direction, observed from the + Y direction. FIG. 16 is a front view showing the configuration of the angular velocity sensor according to the second embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.
Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified.
Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios.
Further, the following embodiments are exemplifications for explaining the present invention, and are not intended to limit the present invention only to the embodiments.
Furthermore, the present invention can be variously modified without departing from the gist thereof.

<First Embodiment>
FIG. 1 and FIG. 2 are block diagrams showing a circuit configuration of a control unit AS (ASIC) applicable to the angular velocity sensor according to the present embodiment.
The control unit AS is electrically connected to each terminal of a connection pad 6 of an angular velocity sensor 1 (see FIG. 3) described later, and in each operation mode including the self-diagnosis mode, the driving arms 2 and 3 of the angular velocity sensor 1 are connected. , The detected vibration detected by the detection arms 4 and 5 is received, signal-processed internally, and then output. Hereinafter, the operation principle of the control unit AS will be described in detail with reference to FIGS. 3 to 16.

FIG. 3 is a perspective view showing an example of the configuration of the angular velocity sensor 1 according to the first embodiment of the present invention. In the figure, the angular velocity sensor 1 extends in the XY plane on the paper surface, and the thickness (Z-direction thickness) is exaggerated for easy understanding.
The angular velocity sensor 1 includes a base 10 located at the center, a pair of drive arms (left drive arm 2 and right drive arm 3) connected to the base 10 and extending in one direction (+ Y direction in FIG. 1), and A pair of detection arms (the left detection arm 4 and the right detection arm 5) extending on the opposite side to the drive arm (in the -Y direction in FIG. 1) are provided.

The angular velocity sensor 1 composed of a base 10, a pair of drive arms 2 and 3, and a pair of detection arms 4 and 5 is made of a common material (for example, silicon or quartz), and patterning a general wafer (silicon wafer or the like). It can be formed integrally or collectively by processing (MEMS processing) or the like.

FIG. 4 is an enlarged front view of the base 10 of the angular velocity sensor 1 shown in FIG. A pair of driving piezoelectric elements (driving elements) 12o and 12i are disposed on the surface of the left driving arm 2 and a pair of driving piezoelectric elements are disposed on the surface of the right driving arm 3 in the vicinity of the connection portion of each driving arm 2 and 3 with the base 10. Elements 13i and 13o are provided.
For example, in the left drive arm 2, the pair of drive piezoelectric elements 12 o and 12 i are arranged on the outer drive piezoelectric elements at positions that are symmetric with respect to the virtual center line L 2 extending in the extending direction (Y direction) of the left drive arm 2. 12o and the inner driving piezoelectric element 12i are provided to face each other.
Similarly, in the right drive arm 3, a pair of drive piezoelectric elements 13i and 13o are provided opposite to each other as an outer drive piezoelectric element 13o and an inner drive piezoelectric element 13i at positions that are axisymmetric with respect to the virtual center line L3. It has been.

Next, in the vicinity of the connection portion of the pair of detection arms 4 and 5 with the base, a detection piezoelectric element 14 is provided so as to cover the surface of the left detection arm 4 and for detection so as to cover the surface of the right detection arm 5. A piezoelectric element 15 is provided. In the detection piezoelectric elements 14 and 15, the virtual center line L4 of the left detection arm 4 extending in the extending direction (Y direction) of the detection arm coincides with the virtual center line (L14) of the detection piezoelectric element 14, The virtual center line L5 of the right detection arm 5 and the virtual center line (L15) of the detection piezoelectric element 15 are arranged to coincide with each other.

The above-described piezoelectric element group can be made of a piezoelectric material such as PZT (lead zirconate titanate). FIG. 5 is an XZ plane sectional view in the vicinity of the connecting portion between the driving arms 2 and 3 and the base 10 shown in FIGS. 3 and 4 (VV sectional view in FIG. 4).
As shown in FIG. 5, the driving piezoelectric elements 12 and 13 each have a three-layer structure in which the upper electrode 21 and the lower electrode 22 sandwich the PZT 20 that is a piezoelectric material.

In general, PZT has a property of self-stretching when a voltage is applied. For example, the PZT 20 expands in the longitudinal direction when a positive voltage is applied, and contracts in the longitudinal direction when a negative voltage is applied.
By utilizing this property, the positive and negative voltages are alternately applied to the upper electrode 21 and the lower electrode 22 to the driving piezoelectric elements 12 and 13, thereby causing the PZT 20 itself to repeatedly expand and contract. it can. In other words, the driving arms 2 and 3 are adjusted in the driving plane (XY plane) by adjusting the sign and timing of the voltages applied to the inner driving piezoelectric elements 12i and 13i and the outer driving piezoelectric elements 12o and 13o. It is possible to arbitrarily vibrate in the X direction.
For example, in the angular velocity sensor 1 according to the present embodiment, the control unit AS (FIG. 1) applies the inner driving piezoelectric elements 12 i and 13 i and the outer driving piezoelectric elements 12 o and 13 o in the left driving arm 2 and the right driving arm 3. On the other hand, if the same kind of voltage is applied to the inner and outer electrodes of the driving arms 2 and 3 in the same cycle, the left driving arm 2 and the right driving arm 3 are moved closer to and away from each other in the X direction in the driving plane. It can be vibrated to repeat.

6 is an XZ plane sectional view in the vicinity of the connecting portion between the detection arms 4 and 5 and the base 10 shown in FIGS. 3 and 4 (a VI-VI sectional view in FIG. 4).
As in FIG. 5, also in the detection arms 4 and 5 shown in FIG. 6, the detection piezoelectric elements 14 and 15 each have a three-layer structure in which the upper electrode 24 and the lower electrode 25 sandwich the PZT 23 that is a piezoelectric material. .

In general, PZT has a property of generating a voltage by expanding and contracting. For example, the PZT 23 generates a positive voltage when expanded in the longitudinal direction, and generates a negative voltage when contracted in the longitudinal direction.
By utilizing this property, vibration due to the Coriolis force generated in the drive arms 2 and 3 propagates to the detection arms 4 and 5 through the base 10, and PZT is detected by the vibration displacement in the detection piezoelectric elements 14 and 15. Can be expanded and contracted.
Then, the charges generated by the expansion and contraction of the PZT 23 can be detected by the upper electrode 24 and the lower electrode 25 and sent to the control unit AS as vibration detection signals.

The base 10 of the angular velocity sensor 1 is fixed in the internal space of the sensor package (not shown), so that the angular velocity sensor 1 is held in an arbitrary direction within the package.
The angular velocity sensor 1 (FIGS. 3 and 4) is connected to the connection lines 52, 53, 54, and the like by wire bonding or the like via a plurality of connection pads 6 (FIGS. 3 and 4) laid on the surface of the base 10. 55 and 57 (FIGS. 1 and 2) and the like are electrically connected to the control unit AS (FIGS. 1 and 2).
With these connections, the control unit AS can control driving and vibration of the driving arms 2 and 3 in the angular velocity sensor 1 and can receive vibration detection signals from the detection arms 4 and 5.

When a drive signal from a drive amplifier (not shown) is transmitted to the drive piezoelectric elements 12 and 13 (FIGS. 3 and 4), the control unit AS (FIGS. 1 and 2) performs the left and right control as follows. The driving arms 2 and 3 are driven.
The monitor electrode 7 shown in FIGS. 3 and 4 is provided to monitor the actual driving vibration of the driving arms 2 and 3 and to keep the driving vibration of the driving arms 2 and 3 at a constant period and amplitude.
Information such as the driving period and timing of the driving arms 2 and 3 driven by a command from the control unit AS is detected by the monitor electrode 7 and sent from the connection pad 6 to the control unit AS via the connection line 57.
The information sent to the control unit AS is then amplified by the amplifier circuit 64 and sent to the phase adjustment circuit 65. Information output from the phase adjustment circuit 65 is detected by the left and right detection arms 4, 5, differentially amplified, synchronously detected, and phase-adjusted by the phase adjustment circuit 69, along with an auto gain controller (AGC) 66. Sent to.
Part of the signal that has passed through the auto gain controller 66 enters straight into one input terminal of the adder circuits 67l and 67r, and the other part of the signal that has passed through the auto gain controller 66 branches after self-diagnosis described later. Then, one enters the other input terminal of the addition circuit 67l, the other is inverted by the inversion circuit 68, and enters the other input terminal of the addition circuit 67r.
In the adder circuits 67l and 67r, two input signals are finely adjusted, and the driving arms 2 and 3 are driven at a constant cycle. After that, the control unit AS inverts the outside signals to the left and right drive arms 2 and 3 by the inverting circuits 68l and 68r, and keeps the inside signals as they are through the connection lines 52i, 52o, 53i and 53o, respectively. And transmitted to the driving piezoelectric elements 12 and 13 (FIGS. 3 and 4).
Thus, the control unit AS of the angular velocity sensor according to the present embodiment can be used for feedback control of the driving of the driving arms 2 and 3 via the connection lines 52 and 53.

FIG. 7 is a perspective view showing the operating principle of the angular velocity sensor 1 according to the present embodiment. In its normal mode, the angular velocity sensor 1 vibrates the pair of driving arms 2 and 3 so that both of them repeat approaching and separating (arrows Vl and Vr) in the X direction within the driving plane.
When a clockwise rotational motion of the rotational angular velocity ω occurs around the central axis S in the longitudinal direction (Y direction) of the angular velocity sensor 1, Coriolis forces 32 and 33 are generated. The Coriolis forces 32 and 33 are expressed by an equation of F = 2 mvω. The Coriolis forces 32 and 33 are rotational angular velocities in a direction perpendicular to both the X-direction velocity direction and the rotation axis (Y direction) applied to the drive arms 2 and 3, that is, in the Z-direction perpendicular to the drive plane. An amplitude (displacement) proportional to the magnitude of ω can be generated in the drive arms 2 and 3. This Coriolis force becomes a vibration in the Z direction in the drive arms 2 and 3.

The vibration in the Z direction generated in the drive arms 2 and 3 travels along the base 10 toward the detection arms 4 and 5 and appears as detection vibrations 34 and 35 in the Z direction on the detection arms 4 and 5. Then, the detection piezoelectric elements 14 and 15 detect the vibration displacement in the detection arms 4 and 5, whereby the rotation direction and magnitude of the rotational angular velocity ω of the rotational motion generated in the angular velocity sensor 1 can be detected.

1. FIG. 8 shows the behavior of an ideal virtual angular velocity sensor 1 ′ in which no so-called leakage vibration exists for each operation mode.
Specifically, the graphs of the movements of the driving arms 2 and 3 and the detection arms 4 and 5, the generated Coriolis force, and waveform information such as detection vibrations and signals are shown.
The virtual angular velocity sensor 1 ′ shown in FIG. 8 operates in the normal mode MD. Specifically, the normal angular mode (when no angular velocity is applied) MDS, the normal mode (when clockwise angular velocity is applied) MDR, and the normal mode ( As applied to the counterclockwise angular velocity (MDL), the operation state is classified into three operation states according to the applied acceleration state.

In the normal mode, the virtual angular velocity sensor 1 ′ has the same period, the same amplitude, and the opposite phase (one of the phases) from the control unit AS to the inner / outer driving piezoelectric elements 12 and 13 on the left and right driving arms 2 and 3. A drive signal having a phase relationship in which the other phase is delayed / or advanced by 180 ° with respect to the phase is applied. In this embodiment, the virtual angular velocity sensor 1 'operates in the normal mode (when no angular velocity is applied) MDS (see FIGS. 8, b, and c).

FIG. 9 is a schematic top view of the behavior of the driving arms 2 and 3 in one cycle in the ideal virtual angular velocity sensor 1 ′ observed from the + Y direction. In the normal mode (when no angular velocity is applied) MDS in the virtual angular velocity sensor 1 ′ described above, the drive vibration is performed so that the left and right drive arms 2 and 3 repeat approach and separation in the X direction in the drive plane in the order of A to H. is doing. The drive arm vibrates in the resonance mode, and the actual vibration has a phase delayed by 90 ° from the drive signals shown in FIGS. 8, b, and c (see FIG. 8, d).
In this embodiment, the vibration of the left and right drive arms 2 and 3 propagates to the base 10 and the base 10 vibrates, so that an electrical signal corresponding to the vibration of the drive arms 2 and 3 is transmitted from the monitor electrode 7. It is sent to the control unit AS via the connection line 57. For example, in this embodiment, the monitor signal is monitored so as to have the same phase as the actual movement of the left driving arm 2 (see FIGS. 8D and 8G), but the movement of the left driving arm 2 is reversed in phase. It is also possible to monitor, and it is also possible to monitor the movement of the right drive arm 3.

In this virtual angular velocity sensor 1 ′, no leakage vibration due to the arrangement of drive piezoelectric elements 12 and 13, which will be described later, can occur, so the amplitude in the Z direction of both drive arms 2 and 3 in this mode is zero ( (See FIG. 8, e). In the normal mode (when no angular velocity is applied) MDS, the virtual angular velocity sensor is not rotated around the Y-axis with respect to 1 '(see h in FIG. 8), so naturally no Coriolis force is generated. Therefore, the signal waveforms and the like at the detection arms 4 and 5 that detect the vibration related to the Coriolis force and the leakage vibration are all 0 (see io in FIG. 8).

In the normal mode (when clockwise angular velocity is applied) MDR, the left and right drive arms 2 and 3 are driven and oscillated so as to repeat approach and separation in the X direction within the drive plane. A clockwise rotational angular velocity ω is applied around the Y axis (see FIG. 8, h), and a Coriolis force corresponding to the amount of rotation is generated in the Z direction with respect to the drive arms 2 and 3. Here, since the left and right drive arms 2 and 3 vibrate in the same period, the same amplitude, and in the opposite phase, that is, in the opposite direction in the X direction, the left and right drive arms have the same amount of Coriolis force in the opposite direction. Is applied in the Z direction (see FIG. 8, i).
That is, the left and right drive arms 2 and 3 to which the Coriolis force is applied pay attention to only the Z direction of the drive arm, and have the same period, the same amplitude, and the opposite phase, that is, the butterfly behavior in the opposite direction of the Z direction. (See FIG. 8, e).

Here, FIG. 10 is a schematic top view in which the behavior of the driving arms 2 and 3 in one cycle in the ideal virtual angular velocity sensor 1 ′ is observed from the + Y direction.
In the normal mode (when clockwise angular velocity is applied) MDR, the left and right driving arms 2 and 3 repeat approach and separation in the X direction in the same manner as the driving arms 2 and 3 in the virtual angular velocity sensor 1 ′ of FIG. In addition to driving vibration, vibration in the Z direction due to Coriolis force is applied.
Therefore, the left and right drive arms 2 and 3 in the normal mode (when applying the clockwise angular velocity) MDR are mixed with the behavior in which both of them repeat the approach and separation in the X direction and the behavior of flapping in the Z direction. It rotates in the reverse direction on the elliptical orbit shown in the order of H.

As shown in FIG. 7, in the virtual angular velocity sensor 1 ′ according to this embodiment, the left drive arm 2 and the left detection arm 4 vibrate in the same direction in the Z direction, and the right drive arm 3 and the right detection arm 5 are in the Z direction. , The drive arms 2 and 3 and the detection arms 4 and 5 corresponding to the upper and lower sides operate so as to form a bow.
That is, the vibrations of the left and right drive arms 2 and 3 having the same period, the same amplitude, and the opposite phase in the Z direction are passed through the base 10 to the detection arms 4 and 5 and have the same period, the same amplitude, and the opposite direction. The vibrations are transmitted as phase vibrations (see k in FIG. 8), so that the left and right vibrations at the detection electrode also have the same period, the same amplitude, and the opposite phase (see FIG. 8, l).

The signals detected by the detection arms 4 and 5 are taken out from the connection pad 6 through the connection lines 54 and 55, sent to the control unit AS, and differentially amplified by the differential amplifier circuit 61 in the control unit AS. (See FIG. 8, m.) After the signal differentially amplified by the synchronous detection circuit 62 is synchronously detected 62 with the monitor signal shifted by 90 ° (see FIG. 8, n), the low-pass filter is obtained. Smoothed by (LPF) 63 and output as an angular velocity signal (see o in FIG. 8).

In the normal mode (when counterclockwise angular velocity is applied) MDL, a counterclockwise rotational angular velocity −ω is applied around the Y axis to the virtual angular velocity sensor 1 ′ in which the left and right drive arms 2 and 3 are driven to vibrate. (See FIG. 8, h), Coriolis force corresponding to the rotation amount is generated in the Z direction with respect to the drive arms 2 and 3.
In this case, the generated Coriolis force is in a direction 180 ° opposite to the direction in the normal mode (when the clockwise angular velocity is applied) MDR (see FIGS. 8, e and i).
Similarly, signals propagated from the left and right drive arms 2 and 3 to the detection arms 4 and 5 via the base 10 are also opposite to the direction in the normal mode (when clockwise angular velocity is applied) MDR by 180 °. (See FIG. 8, k, l).

The signals detected by the detection arms 4 and 5 in the normal mode (when counterclockwise angular velocity is applied) are detected from the connection pad 6 via the connection lines 54 and 55 in the same manner as in the normal mode (when clockwise angular velocity is applied) MDR. The signal that is sent to the control unit AS, differentially amplified by the differential amplifier circuit 61 in the control unit AS (see FIG. 8, m), and differentially amplified by the synchronous detection circuit 62 is converted into a monitor signal 90. After synchronous detection with a signal whose phase is shifted (see n in FIG. 8), the signal is smoothed by the low-pass filter 63 and output as an angular velocity signal.
However, it can be seen that the final output signal is 180 ° opposite to the rotation direction in the normal mode (when clockwise angular velocity is applied) MDR (see FIG. 8, o).

Next, when the rotation around the Y axis is no longer applied to the virtual angular velocity sensor 1 ', the virtual angular velocity sensor 1' operates again in the normal mode (when no angular velocity is applied) MDS.

As described above, it is ideal that only the Coriolis force generated by the drive arms 2 and 3 is detected by the detection arms 4 and 5, but in actuality, it is caused by imperfectness in the processing accuracy of the angular velocity sensor 1. It is inevitable that mechanical leakage vibration is detected by the detection arms 4 and 5.
Further, the leakage vibration has a larger amplitude than the vibration caused by the Coriolis force, which is a very weak vibration.
Such leakage vibration includes leakage vibration in the X direction in which the vibration in the X direction of the driving arms 2 and 3 propagates to the detection arms 4 and 5, and Z direction other than the Coriolis force on the driving arms 2 and 3. There is a leaking vibration in the Z direction in which the above vibration occurs.
Hereinafter, a self-diagnosis method of the angular velocity sensor in each leakage vibration will be described.

2. In the case of leakage vibration in the X direction In the design of a general tuning fork type angular velocity sensor, even if the vibration in the X direction of the drive arm leaks to the detection arm side, the detection piezoelectric element in the detection arm is detected. This leakage vibration is canceled by providing it so as to be symmetrical with respect to the center line of the arm.
Specifically, when such vibration leakage occurs, for example, the balance is maintained such that the left side expansion and the right side contraction of the piezoelectric element are the same, and the single piezoelectric element for detection leaks. The design is made so as to cancel out vibrations and not generate electric charges that may be noise.

However, it is difficult in manufacturing to make the center line with respect to the extending direction of the extremely small detection piezoelectric element completely coincide with the center line of the detection arm.
In addition, with one detection arm, the charge can be completely canceled only when the center line of the arm itself and the vibration center line of the vibration applied to the arm completely match, but the tuning fork type In this angular velocity sensor, since the base for fixing and supporting the arm cannot be symmetrical with respect to each arm, the center line of the arm and the vibration center line are always shifted.
Therefore, it is difficult to maintain the balance of stress in the tuning fork type angular velocity sensor, and it is extremely difficult to prevent the vibration in the X direction from occurring in the tuning fork type angular velocity sensor.

FIG. 11 shows the behavior of the angular velocity sensor 1 in which leakage vibration in the X direction occurs for each operation mode. Specifically, the graphs of the movements of the driving arms 2 and 3 and the detection arms 4 and 5, the generated Coriolis force, and waveform information such as detection vibrations and signals are shown.
The operation mode of the angular velocity sensor 1 shown in FIG. 11 is normally composed of three modes: normal mode (when no angular velocity is applied) MDSx, normal mode (when clockwise angular velocity is applied) MDRx, and normal mode (when counterclockwise angular velocity is applied) MDLx. Mode MDx and self-diagnosis mode MCx.
Note that, in the following description, the description part overlapping with the description in the ideal virtual angular velocity sensor 1 ′ having no leakage vibration described above is not particularly mentioned in detail.

In the normal mode, the angular velocity sensor 1 has the same period, the same amplitude and the opposite phase (in one phase) with respect to the inner / outer driving piezoelectric elements 12 and 13 on the left and right driving arms 2 and 3 from the control unit AS. On the other hand, a drive signal having a phase relationship in which the other phase is delayed / or advanced by 180 ° is applied.
In the present embodiment, the angular velocity sensor 1 operates in the normal mode (when no angular velocity is applied) MDSx (see FIGS. 11, b, and c).
However, when the present angular velocity sensor 1 is activated in the normal mode (when no angular velocity is applied) MDSx, unlike the ideal virtual angular velocity sensor 1 ′ described above, leakage vibration in the X direction occurs, and the detection arm 4 and 5 vibrate in the X direction.
In the angular velocity sensor 1 according to the present embodiment, the vibrations in the detection arms 4 and 5 caused by the leakage vibration that propagates from the driving arms 2 and 3 through the base 10 are in-phase vibrations (FIG. 11, However, the element design may be such that the vibrations in the detection arms 4 and 5 due to the leakage vibrations are in reverse phase.
The angular velocity sensor 1 according to the present embodiment is effective even when the vibrations in the detection arms 4 and 5 due to the leakage vibration are not completely in phase or antiphase.

In normal mode (when no angular velocity is applied) MDSx, no rotation around the Y axis is applied to the angular velocity sensor 1 (see h in FIG. 11), so no Coriolis force is naturally generated. Vibrations in the Z direction cannot be detected by the detection arms 4 and 5 that detect the leak signal (see i in FIG. 11).
The differential amplification output of the detection signal is the difference between the left and right detection signals. As described above, the left and right detection signals have the same phase in the X direction (see j in FIG. 11) and 0 in the Z direction (see FIG. 11 and k), the resulting differential output is 0 (see FIG. 11, m and o).

In the normal mode (when clockwise angular velocity is applied) MDRx, the left and right drive arms 2 and 3 are driven and vibrated so as to repeat approach and separation in the X direction within the drive plane. Is applied with a clockwise rotational angular velocity ω, and a Coriolis force corresponding to the amount of rotation is generated in the Z direction with respect to the drive arms 2 and 3.
Here, since the left and right drive arms 2 and 3 vibrate in the same period, the same amplitude, and in the opposite phase, that is, in the opposite direction in the X direction, the same amount and opposite Coriolis force is applied in the Z direction. (See FIG. 11, i).
That is, when the left and right drive arms 2 and 3 to which the Coriolis force is applied pay attention only to the Z direction of the drive arms, they have the same period, the same amplitude, and the opposite phase, that is, the butterfly behavior in the Z direction reverse direction ( (See FIG. 11, e).

In this mode, in addition to vibration in the Z direction due to the Coriolis force in the driving arms 2 and 3 similar to the normal mode (when no angular velocity is applied) MDSx, leakage vibration in the X direction is also transferred to the detection arms 4 and 5. Propagating.
Therefore, the detection arms 4 and 5 detect not only vibrations with the same period, same amplitude and opposite phase in the Z direction (see k in FIG. 11) but also in normal mode (when no angular velocity is applied) MDSx. This is a leakage vibration in the X direction having the same period, the same amplitude, and the same phase as those detected (see FIG. 11, j).

As described above, the vibrations in the X direction in the detection arms 4 and 5 are in phase (see FIG. 11, j), and are canceled by differential amplification.
On the other hand, the vibration in the Z direction caused by the Coriolis force in the detection arms 4 and 5 is in reverse phase (see k in FIG. 11), so that the differential outputs of the detection arms 4 and 5 are finally output. It is only the Z direction component (see FIG. 11, m).
Even in this mode, the signal differentially amplified by the differential amplifier circuit 61 (see m in FIG. 11) is synchronously detected by the synchronous detection circuit 62 with a signal whose phase is shifted by 90 degrees ( The detection signal is finally smoothed by the low-pass filter 63 and output as an angular velocity signal (see FIG. 11, o).

In the normal mode (when counterclockwise angular velocity is applied) MDLx, the Coriolis force corresponding to the amount of rotation generated in the Z direction with respect to the drive arms 2 and 3 and the signal propagated to the detection arms 4 and 5 are in the normal mode (clockwise). (When angular velocity is applied) The direction in MDRx is 180 ° opposite (see FIG. 11, k, l), and the final output signal is 180 ° opposite to the rotation direction in normal mode (when clockwise angular velocity is applied) MDRx. Direction.
Also in this mode, vibrations in the X direction in the detection arms 4 and 5 are in phase (see FIG. 11, j), and vibrations in the Z direction in the detection arms 4 and 5 are in reverse phase (see k in FIG. 11). Therefore, only the Z direction component is finally output as the differential outputs of the detection arms 4 and 5 (see m in FIG. 11), and the detection signal is finally smoothed and output by the low-pass filter 63. (See FIG. 11, o).

Next, when the rotation around the Y-axis is no longer applied to the angular velocity sensor 1, the angular velocity sensor 1 operates again in the normal mode (when no angular velocity is applied) MDSx.

The self-diagnosis mode MCx (see FIG. 11A) shown in FIG. 11 is practically problematic when the angular velocity sensor 1 is not actually detecting the rotational angular velocity ω, such as when the angular velocity sensor 1 is activated or in a standby state. It is an active mode that can be executed arbitrarily in a short time.
By using this self-diagnosis mode MCx, an initial self-diagnosis signal obtained by driving the angular velocity sensor 1 in the self-diagnosis mode MCx in a state where there is no initial failure such as a factory shipment state, and after the use of the angular velocity sensor 1 is started Only by comparing with the actually measured self-diagnostic signal, various damages such as breakage or failure of the angular velocity sensors and / or driving piezoelectric elements provided in them, and short circuit and disconnection of signal lines, etc. It is possible to detect whether or not a defect has occurred.
Further, by utilizing the self-diagnosis mode MCx, it is possible to quickly and accurately determine malfunctions occurring in the angular velocity sensor, such as malfunctions and functional deterioration, and to promptly replace the angular velocity sensor or the sensor package provided with it, It can be used as an index of maintenance time.

FIG. 12 is an enlarged view of a waveform showing a shift in timing of application of vibration to the left and right drive arms 2 and 3 in the self-diagnosis mode MCx (this enlarged view corresponds to FIGS. 11, b, and c). .
As shown here, in the self-diagnosis mode MCx, the drive vibrations that are shifted by + α ° (α ° earlier) with respect to one of the drive arms 2 and 3 in the opposite phase states in the other modes are applied. A drive signal shifted by -β ° (slower by β °) is applied to the other drive arm.
That is, the control unit prevents the left driving arm 2 and the right driving arm 3 from having the same period and the same amplitude, and the vibration phases of the left driving arm 2 and the right driving arm 3 are shifted from the opposite phases and do not become the same phase. The AS controls the drive vibration of the left drive arm 2 and the right drive arm 3.

The drive control of the drive arms 2 and 3 by the control unit AS in the self-diagnosis mode MCx only needs to add the self-diagnosis block SC to the Coriolis detection control unit AS as shown in FIG.
Specifically, after a part of the signal that has passed through the auto gain controller 66 has passed through the phase adjustment circuit 81, it is directed to the start switch 82 in the self-diagnosis mode MCx. When the self-diagnosis mode MCx is ON (see FIG. 11A), a signal corresponding to the drive vibration shifted by + α ° is generated by the amplifier circuit 83, and after branching, one signal is inverted by the inverter circuit 68. Then, a drive signal is sent to the adder circuit 67 to each of the left and right drive arms 2 and 3.
For example, in the control circuit of FIG. 1, driving vibration that is shifted by + α ° (α ° faster) is applied to the left driving arm 2 and driving that is shifted by −α ° (α ° slower) is applied to the right driving arm 3. A signal can be generated.
Instead of providing the inverting circuit 68, an amplifier circuit for the left driving arm and an amplifier circuit for the right driving arm may be provided separately in order to apply driving vibrations at different timings.

Further, the adder circuit 67 may be connected only to the left driving arm 2 as in another embodiment of the control unit AS shown in FIG. In this case, the drive vibration of the right drive arm 3 remains fixed in all modes from time to time. Only the left drive arm 2 is deviated by + α ° in the feedback control by the auto gain controller 66 and the self-diagnosis mode MCx ( It is also possible to apply drive vibration (α ° faster).
As described above, in the self-diagnosis mode MCx, it is only necessary that the vibrations in the drive arms 2 and 3 are deviated from the opposite phases.

By giving the above-mentioned “deviation” control signal of the drive timing to both the drive arms 2 and 3, the drive arms 2 and 3 can give a deviation of the vibration timing to the leakage vibration in the X direction. it can. That is, in other modes, even in the X direction detection signal that can be detected as in-phase vibrations in the detection arms 4 and 5, it is possible to positively cause a phase shift between the left and right detection arms 4 and 5.
In this mode, rotation about the Y axis is not applied to the angular velocity sensor (see FIG. 11, h), so that no Coriolis force is generated in the drive arms 2 and 3, and Z is detected in the detection arms 4 and 5. Directional vibrations are never detected.

As described above, by generating a shift in the detection signal in the X direction, in this mode, it is possible to acquire differential vibrations for the vibration (leakage vibration) component in the X direction (see m in FIG. 11). ).
That is, in the self-diagnosis mode MCx, as in the normal mode, the signals detected by the detection arms 4 and 5 are differentially amplified by the differential amplifier circuit 61 in the control unit AS (see m in FIG. 11) and synchronized. The signal differentially amplified by the detection circuit 62 is synchronously detected by a signal whose phase is shifted by 90 ° from the monitor signal (see n in FIG. 11), and then the detection signal is smoothed by the low-pass filter 63 and used as a self-diagnosis signal. It is possible to output (see o in FIG. 11).

The angular velocity sensor 1 having a leakage vibration in the X direction according to the present embodiment receives an initial self-diagnosis signal (see o in FIG. 11) that is output in a normal state at the time of product shipment and driven in a self-diagnosis mode. For example, an output monitoring circuit (determination circuit) 70 stored in storage means such as a memory is provided.
The output monitoring circuit 70 sets conditions such as thresholds corresponding to various failure conditions for the initial self-diagnosis signal, and compares the actual self-diagnosis signal with the initial self-diagnosis signal. Then, when the value of the self-diagnosis signal deviates from this threshold value, or when a self-diagnosis signal corresponding to a specific failure state is detected, it is possible to generate an abnormality flag and notify the failure determination result to the outside. Become.

Thus, it is not necessary to add a dedicated circuit configuration to the angular velocity sensor 1 having leakage vibration in the X direction according to the present invention in order to detect a failure. The angular velocity sensor and the piezoelectric element are damaged or broken, and / or the circuit is short-circuited and the signal line is disconnected simply by shifting the vibration timing of the driving arms 2 and 3 using the normal angular velocity detection control unit AS. Thus, it is possible to accurately grasp whether or not such a failure has occurred, and a self-diagnosis for determining a failure of the angular velocity sensor can be easily performed.

3. In the case of leakage vibration in the Z direction In the design of a general tuning fork type angular velocity sensor, the driving arms 2 and 3 only have driving piezoelectric elements 12 and 13 for driving vibration in the X direction. Application of directional vibrations is not considered at all.
However, as shown in FIG. 5, since the driving piezoelectric elements 12 and 13 are arranged only on the front surfaces of the silicon driving arms 2 and 3, between the front and back surfaces of the driving arms 2 and 3, Uneven movement in the thickness direction of the drive arms 2 and 3 is generated, and it is unavoidable that vibration in the Z direction other than the X direction is generated although it is minute.

FIG. 13 shows the behavior of the angular velocity sensor 1 in which leakage vibration in the Z direction occurs for each operation mode. Specifically, the graphs of the movements of the driving arms 2 and 3 and the detection arms 4 and 5, the generated Coriolis force, and waveform information such as detection vibrations and signals are shown.
The operation mode of the angular velocity sensor shown in FIG. 13 is a normal mode consisting of three modes: normal mode (when no angular velocity is applied) MDSz, normal mode (when clockwise angular velocity is applied) MDRz, and normal mode (when counterclockwise angular velocity is applied) MDLz. MDz and self-diagnosis mode MCz.
In the following description, the overlapping description with the above description in the ideal virtual angular velocity sensor 1 ′ having no leakage vibration and the angular velocity sensor 1 having leakage vibration in the X direction is referred to in particular detail. Absent.

In the normal mode, the angular velocity sensor 1 has the same period, the same amplitude and the opposite phase (in one phase) with respect to the inner / outer driving piezoelectric elements 12 and 13 on the left and right driving arms 2 and 3 from the control unit AS. On the other hand, a drive signal having a phase relationship in which the other phase is delayed / or advanced by 180 ° is applied.
In the present embodiment, the angular velocity sensor 1 operates in the normal mode (when no angular velocity is applied) MDSz (see FIGS. 13, b, and c).
However, when the present angular velocity sensor 1 is activated in the normal mode (when no angular velocity is applied) MDSz, unlike the ideal virtual angular velocity sensor 1 'described above, the driving arm 2 of the driving piezoelectric elements 12, 13 is used. , 3 causes leakage vibration in the Z direction due to the arrangement on the surface, and the detection arms 4 and 5 vibrate slightly in the Z direction.
In the angular velocity sensor 1 according to the present embodiment, the vibrations in the Z direction that actually occur in the drive arms 2 and 3 are in the same phase on both the left and right sides (see e in FIG. 13). The element design is made so that the Z-direction vibration in the detection arms 4 and 5 caused by the leaking vibration that propagates is also the same-phase vibration (see k in FIG. 13). It is also possible to design an element such that the vibrations at the detection arms 4 and 5 are in reverse phase.
In addition, the angular velocity sensor 1 according to the present embodiment is effective even when the vibrations in the detection arms 4 and 5 due to the leakage vibration are not completely in the same phase or opposite phase.

Here, FIG. 14 is a schematic top view in which the behavior of the driving arms 2 and 3 in one cycle in the angular velocity sensor 1 having leakage vibration in the Z direction is observed from the + Y direction.
In the normal mode (when no angular velocity is applied) MDSz in the angular velocity sensor 1, the left and right drive arms 2 and 3 vibrate in the order of A to H, both of which repeatedly approach and separate in the X direction, and in the order of A to H. It can be seen that both of them are mixed in the same phase and driven in the Z direction, and as a result, repeatedly vibrated in an oblique linear direction.
The drive arms 2 and 3 and the detection arms 4 and 5 vibrate in the resonance mode, and the actual vibration has a phase delayed by 90 ° from the drive signals shown in FIGS. 13, b and c (13, d, e reference).

In normal mode (when no angular velocity is applied) MDSz, no rotation around the Y axis is applied to the angular velocity sensor (see FIG. 13, h), so naturally no Coriolis force is generated. Since the signal is not taken into consideration, only the leakage vibration in the Z direction is detected by the detection arms 4 and 5 (see k in FIG. 13). The differential amplification output of the detection signal is the difference between the left and right detection signals. As described above, the left and right detection signals have the same phase in the Z direction (see k in FIG. 13) and 0 in the X direction (see FIG. 13, j Therefore, the obtained differential output is 0 as a result (see FIG. 13, m and o).

In the normal mode (when the clockwise angular velocity is applied) MDRz, the left and right drive arms 2 and 3 are driven and vibrated so as to repeat approaching and separating in the X direction, and clockwise around the Y axis with respect to the angular velocity sensor 1. A rotational angular velocity ω is applied (see h in FIG. 13), and a Coriolis force corresponding to the amount of rotation is generated in the Z direction with respect to the drive arms 2 and 3. Here, since the left and right drive arms 2 and 3 vibrate in the same cycle, the same amplitude, and in the opposite phase, that is, in the X direction, the left and right drive arms 2 and 3 have the same amount and the opposite direction, respectively. Coriolis force is applied in the Z direction (see FIG. 13, i).
Here again, the left and right drive arms 2 and 3 to which the Coriolis force is applied, when focusing only on the Z direction of the drive arm, try to have the same period, the same amplitude, and the opposite phase, that is, the butterfly behavior in the opposite direction of the Z direction. (Refer to i in FIG. 13).

However, since the drive arms 2 and 3 have the same period, the same amplitude, and the same phase leakage vibration in the Z direction as described above, these two Z direction vibrations are mixed in the drive arms 2 and 3. (See FIG. 13, e).

Here, FIG. 15 is a schematic top view in which the behavior of the driving arms 2 and 3 in one cycle in the angular velocity sensor 1 having leakage vibration in the Z direction is observed from the + Y direction.
In the normal mode (when clockwise angular velocity is applied) MDRz, in addition to the drive vibration in which the left and right drive arms 2 and 3 repeat approaching and moving away in the X direction as shown in FIG. In addition, three vibrations are mixed with the vibration in the Z direction caused by the Coriolis force.
Accordingly, the left and right drive arms 2 and 3 in the normal mode (when clockwise angular velocity is applied) MDRz in the angular velocity sensor 1 having leakage vibration in the Z direction are shown in the order of A to H as shown in FIG. It rotates in the opposite direction with an elliptical orbit distorted in an oblique direction.
In addition, since the vibration of the elliptical orbit distorted in the oblique direction is mixed with the vibration in the Z direction caused by the Coriolis force including the butterfly behavior, the movement of the left and right drive arms 2 and 3 is the Z direction. In FIG.

In the normal mode (when clockwise angular velocity is applied) MDRz, a vibration in which the Z-direction leakage vibration and the Z-direction vibration due to the Coriolis force are mixed in the driving arms 2 and 3 propagates through the base 10 and is detected. 4 and 5 (see FIG. 13, k).
Of the detection signals in which the two Z-direction components are mixed, as described above, the leakage vibration that is the in-phase component (see e in FIG. 13) is canceled by differential amplification.
On the other hand, since the vibration component in the Z direction due to the Coriolis force has an opposite phase (see i in FIG. 13), the final output as the differential output of the detection arms 4 and 5 is due to the Coriolis force. It is only the Z direction component (see FIG. 13, m).
The differentially amplified signal is synchronously detected by a signal whose phase is shifted by 90 ° from the monitor signal, and finally smoothed by the low-pass filter 63 and output as an angular velocity signal (FIG. 13, n, o).

In the normal mode (when the counterclockwise angular velocity is applied) MDLz, the Coriolis force corresponding to the amount of rotation generated in the Z direction with respect to the driving arms 2 and 3 and the signal propagated to the detection arms 4 and 5 are in the normal mode (clockwise). (When angular velocity is applied) The direction is 180 ° opposite to the direction in MDRz (see FIG. 13, k, l), and the final output signal is 180 ° opposite to the rotation direction in normal mode (when clockwise angular velocity is applied) MDRz. Direction.
Also in this mode, the leakage vibration in the Z direction that is the in-phase component (see FIG. 13, e) is canceled by the differential amplifier 61, and the vibration component in the Z direction caused by the Coriolis force that is in the opposite phase (FIG. 13, only i) is output as a differential output (FIG. 13, m). After synchronous detection, the signal is finally smoothed by the low-pass filter 63 and output as an angular velocity signal (see n and o in FIG. 13).

Next, when the rotation about the Y axis is no longer applied to the angular velocity sensor 1, the angular velocity sensor 1 operates again in the normal mode (when no angular velocity is applied) MDSz.

The self-diagnosis mode MCz (see FIG. 13, a) is a short time that does not cause a practical problem when the angular velocity sensor 1 is not actually detecting the rotational angular velocity ω, such as when the angular velocity sensor 1 is activated or in a standby state. It can be arbitrarily executed.
The method of detecting the malfunction of the angular velocity sensor 1 in the self-diagnosis mode MCz in the angular velocity sensor 1 having leakage vibration in the Z direction is the same as that of the angular velocity sensor 1 having leakage vibration in the X direction described above.

Also in the angular velocity sensor 1 having the leakage vibration in the Z direction, the deviation of the timing of applying the vibration to the left and right drive arms 2 and 3 in the self-diagnosis mode MCz is the same as that shown in FIG. b and c correspond to FIG. 12).
Also here, the left driving arm 2 and the right driving arm 3 are controlled so as to have the same period and the same amplitude, respectively, and the vibration phases of the left driving arm 2 and the right driving arm 3 are not shifted from the opposite phase but become the same phase. The part AS controls the drive vibration of the left drive arm 2 and the right drive arm 3.

By giving such a “deviation” X-direction driving vibration to both the driving arms 2 and 3, it is possible to give a deviation in the timing of the vibration to the Z-direction leakage vibration of the driving arms 2 and 3. it can.
That is, in other modes, even in the Z-direction leakage vibration detected as the same-phase vibration in the detection arms 4 and 5, it is possible to positively cause a phase shift between the left and right detection arms 4 and 5.
In this mode, rotation about the Y axis is not applied to the angular velocity sensor 1 (see h in FIG. 13).
Therefore, no Coriolis force is generated in the drive arms 2 and 3, and there is no rotational vibration in the Z direction due to the Coriolis force.
That is, in this mode, only the leakage vibration in the Z direction including the operation timing shift (phase shift) is detected by the detection arms 4 and 5 (see FIGS. 13, k and l).
Note that vibrations in the X direction are not detected by the detection arms 4 and 5 (see FIG. 13, j).

As described above, by generating a shift in the detection signal in the X direction, in this mode, it is possible to acquire the differential vibration for the leakage vibration component in the Z direction (FIG. 13, m).
That is, in the self-diagnosis mode MCz, as in the normal mode, the signals detected by the detection arms 4 and 5 are differentially amplified by the circuit in the control unit AS (see m in FIG. 13) and differentially amplified. After the monitor signal is synchronously detected with a signal whose phase is shifted by 90 ° (see n in FIG. 13), it can be smoothed by the low-pass filter 63 and output as a self-diagnosis signal (see o in FIG. 13). It becomes.

Similar to the self-diagnostic mode MCx using the angular velocity sensor 1 having leakage vibration in the X direction described above, the angular velocity sensor 1 having leakage vibration in the Z direction is also driven in the self-diagnosis mode in a normal state at the time of product shipment. An output monitoring circuit (determination circuit) 70 is provided that stores the initial self-diagnosis signal (see o in FIG. 13) that is output in this manner in a storage means such as a memory.
The output monitoring circuit 70 sets conditions such as threshold values corresponding to various failure conditions for the initial self-diagnosis signal, compares the actual self-diagnosis signal with the initial self-diagnosis signal, and sets the threshold value. When the value of the self-diagnosis signal deviates from the above, or when a self-diagnosis signal corresponding to a specific failure state is detected, an abnormality flag can be generated to notify the failure determination result to the outside.

The angular velocity sensor 1 having leakage vibration in the Z direction according to the present invention also does not need to be additionally provided with a dedicated circuit configuration for failure detection, and the driving arm 2 is controlled by using a normal angular velocity detection control unit AS. It is possible to accurately grasp whether or not the angular velocity sensor and the piezoelectric element are broken or broken, and / or the occurrence of a malfunction such as a short circuit or a disconnection of a signal line, etc. simply by shifting the vibration timing 3. It is possible to perform a self-diagnosis for determining a failure of the angular velocity sensor.

4). When X-direction leakage vibration and Z-direction leakage vibration coexist In the design of a general tuning fork type angular velocity sensor, the X-direction driving vibration of the driving arm may leak to the detection arm side as described above. Inevitable (leakage vibration in the X direction), it is also unavoidable that vibration other than the X direction occurs in the drive arm (leakage vibration in the Z direction).
Therefore, only one of the leakage vibration in the X direction and the leakage vibration in the Z direction described above does not exist in the angular velocity sensor 1, but exists in a state where both are mixed.

However, if the angular velocity sensor that operates in the self-diagnosis mode according to the present application is used, since the phase difference is provided in the driving vibration in the X direction and the Z direction in the driving arm as described above, the X direction and the Z direction are detected from the detection signal. A combined differential output can also be extracted and output as a self-diagnosis signal for use in fault self-diagnosis.
Furthermore, the vibration detection circuit used for this diagnosis can use the angular velocity detection control unit AS used for Coriolis force detection as it is, and has a high failure detection capability while simplifying the configuration of the angular velocity sensor. By doing so, the risk of failure or the like can be greatly reduced.

Second Embodiment
FIG. 16 is a front view showing an example of the configuration of an angular velocity sensor 100 (angular velocity sensor) according to the second embodiment of the present invention. This angular velocity sensor 100 includes a base portion 110 and a pair of drive detection arms (a left drive detection arm 102 and a right drive detection arm 103) extending from the upper side of the base portion 110 (in the + Y direction in FIG. 11). I am doing.
In such a U-shaped angular velocity sensor 100, the driving piezoelectric elements 112 and 113 and the detecting piezoelectric elements 114 and 115 are provided in the same tuning fork vibrator, so that the area of the angular velocity sensor can be reduced. Therefore, the angular velocity sensor can be further reduced in size.
Further, since the drive arm and the detection arm are the same, it is possible to more directly detect the vibration caused by the Coriolis force generated in the drive arm.

Also in the U-shaped angular velocity sensor 100 according to the second embodiment, the mechanism that causes the leakage vibration in the X direction and the Y direction is the same as that of the first embodiment.
That is, the angular velocity sensor 100 having leakage vibrations in the X direction and the Z direction according to the present embodiment has various initial self-diagnosis signals acquired in the self-diagnosis mode MC in a state where there is no initial failure. By setting conditions such as a threshold value according to the failure status, an abnormal flag is generated when the self-diagnosis signal deviates from the threshold value or when a self-diagnosis signal corresponding to a specific failure state is detected. It is possible to notify the failure determination result.
As a result, the U-shaped angular velocity sensor 100 having leakage vibrations in the X direction and the Z direction in the present invention does not need to be additionally provided with a dedicated circuit configuration for failure detection, and the operation of the drive detection arms 102 and 103 It is possible to perform a self-diagnosis of a failure of the angular velocity sensor 100 using the normal angular velocity detection control unit AS only by shifting the timing.

Note that the present invention is not limited to the above-described embodiments, and as described above, various modifications (for example, appropriate combinations of the contents of the embodiments) are possible without departing from the spirit of the present invention. Etc.) is possible.
For example, the self-diagnosis in the present invention can be executed by taking the difference between the output of the normal mode and the self-diagnosis mode as long as a constant angular velocity ω is applied.
Furthermore, it is also possible to provide the same vibration elements as those provided on the surfaces of the drive arm and the detection arm not only on the surface of each arm but also on the back surface with the same arrangement rule.
With the angular velocity sensor configured in this way, it is also possible to improve the sensitivity of the sensor while minimizing the movement unevenness between the front and back surfaces of the drive arm and reducing the vibration that can become noise of the angular velocity sensor. It is.
Moreover, since it is extremely difficult to manufacture accurately the positions of the piezoelectric thin film elements on both the front and back surfaces, even in this case, it is inevitable that leakage vibrations in the angular velocity sensor are unavoidable. It is done.
Therefore, the angular velocity sensor having this double-sided vibration element configuration can be operated in the self-diagnosis mode according to the present invention.
This application is based on a Japanese patent application (Japanese Patent Application No. 2011-42798) filed on February 28, 2011, the contents of which are incorporated herein by reference.

DESCRIPTION OF SYMBOLS 1,100 ... Angular velocity sensor, 1 '... Virtual angular velocity sensor, 2 ... Left drive arm, 3 ... Right drive arm, 4 ... Left detection arm, 5 ... Right detection arm, 6 ... Connection pad, 7 ... Monitor electrode, 10 ... Base, 12, 13, 112, 113 ... Driving piezoelectric element, 14, 15, 114, 115 ... Detection piezoelectric element, 21, 23 ... Upper electrode, 22, 24 ... Lower electrode, 32, 33 ... Coriolis force, 34 35 ... Detection vibration, 52, 53, 54, 55, 57 ... Connection, 61 ... Differential amplifier circuit, 62 ... Synchronous detection circuit, 63 ... Low pass filter, 64 ... Amplifier circuit, 65 ... Phase adjustment circuit, 66 ... Auto Gain controller, 67 ... adder circuit, 68 ... inverting circuit, 69 ... phase adjustment circuit, 70 ... output monitoring circuit, 81 ... phase adjustment circuit, 82 ... start switch, 83 ... amplification circuit, 102 ... left drive detection arm, 103 ... Right drive detection 110: Base, AS: Control unit, MD: Normal mode, MDS: Normal mode (when no angular velocity is applied), MDR: Normal mode (when clockwise angular velocity is applied), MDL: Normal mode (when counterclockwise angular velocity is applied) , MC: self-diagnosis mode, SC: self-diagnosis block, L2, L3, L4, L5: virtual center line, S: center line, ω: rotational angular velocity, V: arrow.

Claims (10)

A tuning fork type vibrator having a first drive arm and a second drive arm;
A first drive element provided on the first drive arm for exciting the first drive arm to vibrate along a drive plane;
A second drive element provided on the second drive arm for exciting the second drive arm to vibrate along the drive plane;
A control unit that outputs a drive signal to each of the first drive element and the second drive element, and vibrates the first drive arm and the second drive arm;
An angular velocity sensor comprising: a detection unit that detects vibrations from the first drive arm and the second drive arm and detects an angular velocity input to the vibrator;
The controller is
The first drive element and the second drive arm have the same period and the same amplitude, and the vibration phase of the second drive arm with respect to the first drive arm is reversed. A normal mode for outputting a drive signal to the second drive element;
The first drive arm and the second drive arm have the same period and the same amplitude, respectively, and the vibration phase of the second drive arm with respect to the first drive arm does not become the same phase while shifting from the opposite phase. An angular velocity sensor that executes a self-diagnosis mode for outputting a drive signal to the first drive element and the second drive element. Furthermore, a base part to which the first driving arm and the second driving arm are connected, and a pair of detections connected to positions where the base part is opposed to the connection part of the first driving arm and the second driving arm. With arms,
The angular velocity sensor according to claim 1, wherein vibration generated in the drive arm is propagated through the base and detected by the pair of detection arms. The angular velocity sensor according to claim 1, wherein vibration generated in the drive arm is detected by the drive arm. The angular velocity sensor according to any one of claims 1 to 3, further comprising a determination circuit that diagnoses the angular velocity sensor as a failure when determining that the detected vibration signal does not exist within a specified numerical range. The controller is
The angular velocity sensor according to any one of claims 1 to 3, wherein the drive timing of the first drive arm is advanced or delayed, and / or the drive timing of the second drive arm is advanced or delayed. The controller is
The angular velocity sensor according to claim 4, wherein the drive timing of the first drive arm is advanced or delayed, and / or the drive timing of the second drive arm is advanced or delayed. Each of the first driving arm and the second driving arm is provided on the upper surface at equal intervals on the left and right with a center line extending in the extending direction of the first driving arm and the second driving arm as a boundary. The angular velocity sensor according to any one of claims 1 to 3, comprising two driving elements. Each of the first driving arm and the second driving arm is provided on the upper surface at equal intervals on the left and right with a center line extending in the extending direction of the first driving arm and the second driving arm as a boundary. The angular velocity sensor according to claim 4, comprising two drive elements. Each of the first driving arm and the second driving arm is provided on the upper surface at equal intervals on the left and right with a center line extending in the extending direction of the first driving arm and the second driving arm as a boundary. The angular velocity sensor according to claim 5, comprising two drive elements. A tuning fork type vibrator having a first drive arm and a second drive arm; and a first drive element provided on the first drive arm for exciting the first drive arm so as to vibrate along a drive plane; A second drive element provided on the second drive arm and configured to excite the second drive arm so as to vibrate along the drive plane, and is driven by each of the first drive element and the second drive element. A control unit that outputs a signal, vibrates the first drive arm and the second drive arm, detects vibrations from the first drive arm and the second drive arm, and determines an angular velocity input to the vibrator. A self-diagnosis method of an angular velocity sensor comprising:
The first drive element and the second drive arm have the same period and the same amplitude, and the vibration phase of the second drive arm with respect to the first drive arm is reversed. The control unit for executing a normal mode for outputting a drive signal to the second drive element has the same period and the same amplitude as each of the first drive arm and the second drive arm, and the first drive arm with respect to the first drive arm. Self-diagnosis method of angular velocity sensor for executing a self-diagnosis mode for outputting a drive signal to the first drive element and the second drive element so that the vibration phase of the second drive arm is shifted from the opposite phase but not the same phase .

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