Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
  • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
  • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
  • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
  • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
  • B06B1/0644—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
  • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
  • G01S7/521—Constructional features

Definitions

• the invention relates to a sound transducer comprising a membrane and at least one piezoelectric element, wherein the vibration plane of the piezoelectric element is arranged parallel to the membrane, the membrane oscillates perpendicular to the vibration plane of the piezoelectric element and the oscillating surface of the membrane is larger than the surface of the piezoelectric element.
• Sound transducers are used, for example, in ultrasonic sensors with which the distance between the ultrasonic sensor and a reflecting object can be measured.
• the sound transducer serves as a transmitter and / or receiver, wherein in a first step, an ultrasonic pulse is emitted. If the ultrasonic pulse hits a reflective object, an ultrasonic echo is generated, which can be detected again via the sound transducer. From the time that elapsed between the emission of the ultrasonic pulse and the detection of the ultrasonic echo and the known speed of sound, the distance to the reflecting object can be calculated.
• the ultrasonic sensors are used, for example, in driver assistance systems to assist a driver of a vehicle in driving maneuvers. In this case, for example, during a parking operation with the aid of one or more ultrasonic sensors, the close range of the vehicle is scanned. For the use of ultrasonic sensors in other
• the transducers for distance measurements of distant objects must generate the largest possible sound pressure.
• the sound transducers should be broadband, that is, the sound transducer should be able to generate sound over a large frequency range and to be able to detect again.
• the broadband is necessary in order to move even in the case of moving objects and / or one together with the
• Vehicle moving ultrasonic sensor to be able to reliably measure, since by the Movement shifts the frequency of the received ultrasonic echo due to the Doppler effect.
• the sound transducers used in ultrasonic sensors for vehicles must meet high mechanical stability requirements.
• the sound transducer can be heavily used by flying stones or other particles.
• the piezo elements contained therein which consist essentially of a ceramic, must not be damaged. A breakage of the piezoelectric element would for
• a sound transducer which comprises a membrane made of an epoxy hollow glass sphere mixture and a piezoceramic disk.
• a piezoelectric ultrasonic transducer is known.
• the piezoelectric transducer element is housed in a pot-shaped housing.
• the bottom of the housing acts as a sound-emitting membrane.
• the piezoelectric transducer element does not touch the bottom or the membrane, but is connected to the walls of the cup-shaped housing. The connection between the
• piezoelectric transducer element and the inner wall of the pot is over a
• DE 196 20 133 A1 discloses an ultrasonic sensor with piezoelectric transducer element.
• the sensor has a cover plate which is excited by the transducer element to vibrate.
• the cover plate comprises concentric webs with which a disk acting as a membrane is mounted on the piezoelectric transducer element.
• the cavities between the transducer element and the membrane may be connected to a non-conductive
• a sound transducer comprising a membrane and at least one piezoelectric element is proposed, wherein the vibration plane of the piezoelectric element in the
• the membrane oscillates substantially perpendicular to the vibration plane of the piezoelectric element and the oscillating surface of the membrane is larger than the surface of the piezoelectric element, wherein the piezoelectric element at its edge regions on the surface of the oscillating surface of the membrane at least partially with the oscillating surface of the membrane is connected, so that forces are transmitted from the piezoelectric element to the membrane, and wherein adjacent to the membrane facing surface of the piezoelectric element at least one space, by the piezoelectric element, the vibrating surface of the membrane and the connections between the piezoelectric element and the membrane is limited, or between the piezoelectric element and the vibrating surface of the membrane, a film is arranged and wherein the remaining surfaces of the piezoelectric element do not touch the membrane.
• Such deviations may unintentionally, for example due to production-related inaccuracies, arise or intended, for example, to optimize the radiation characteristic, be provided or be caused by a combination thereof.
• the diaphragm For the emission of sound, the diaphragm must be vibrated by the piezoelectric element.
• the piezoelectric element executes vibrations along a plane that is substantially parallel to the membrane.
• Thick vibration that is, a vibration substantially along the surface normal of the membrane, the diaphragm must buckle.
• connection between the piezoelectric element and the oscillating surface of the membrane may be at least partially executed along the edge regions of the piezoelectric element, for example sequentially. Preferably, the connection is carried out substantially along the entire edge regions of the piezoelectric element. If the piezoelectric element were connected to the membrane over the entire surface, the overall composite of membrane and piezoelectric element would have a higher rigidity than the membrane alone. The oscillation amplitude of the membrane would be lower and thus also the generated sound pressure. Furthermore, a composite membrane and piezoelectric element would have a greater mass than the membrane alone. With the same oscillation amplitude, more energy must be expended for the composite of membrane and piezoelectric element than for the membrane alone.
• the piezoelectric element By providing the connection between the piezoelectric element and the oscillating surface of the membrane at the edge regions of the piezoelectric element, a transmission of the shear stresses resulting from the oscillation of the piezoelectric element to the vibrating surface of the diaphragm is ensured, on the other hand, the piezoelectric element does not have to deform the diaphragm participate.
• the enclosed between the membrane facing surface of the piezoelectric element and the membrane space or the film between the membrane and the piezoelectric element contribute to the fact that the membrane can deform largely unhindered.
• Piezoelement also has an advantageous effect on the stone chip resistance of the transducer. Although a punctiform load, such as by a flying stone, still leads to a strong deformation and possibly a local damage to the membrane, but the piezoelectric element is not firmly bonded to the membrane over the entire surface. The space or the film between the membrane and the piezoelectric element can thus absorb the deformation without forces acting on the piezoelectric element and can damage this.
• the membrane of the transducer used may be flat or curved depending on the embodiment.
• a bending of the membrane can, for example, as a curvature in the
• the membrane may be cup-shaped. It is also conceivable to combine several forms, so that one cup-shaped membrane with a flat area or with a curved area is conceivable.
• the shape of the membrane influences the sound radiation and directivity of the transducer and can be adjusted according to the application. For example, a rotationally symmetric shape results in a more homogeneous directional characteristic than
• the piezoelectric element has a smaller area than the membrane, wherein the shape of the piezoelectric element is preferably oriented on the shape of the oscillating surface of the membrane.
• further designs such as rectangular, square, elliptical or polygonal shapes, are possible.
• a rectangular piezoelectric element can also be used.
• the adhesive is preferably such that an elongation of the piezoelectric element does not result in a deformation of the
• Adhesive passes, but over the connection in the edge areas of the
• Piezoiatas causes a deformation of the membrane. Besides gluing are also
• connection between the membrane and the piezoelectric element by gluing the edge of the
• Piezo element manufactured with arranged on the membrane webs It can be determined by the length of the webs on which the piezoelectric element is glued, the ratio of force and deflection. The shorter the webs are executed, the greater the gear ratio of the deflection of the diaphragm to the deflection of the
• this cavity filled with an elastic material for damping the membrane.
• a film is arranged between the membrane and the piezoelectric element. The power transmission from
• Piezo element on the vibrating surface of the membrane is formed by bonds between the piezo element and the film as well as between the film and the membrane in the
• the film used preferably has a high shear stiffness, so that a force transmission from the piezoelectric element to the membrane can take place via the film.
• the sound transducer according to the invention is between the
• Membrane and the piezoelectric element disposed a film, wherein the dimensions of the film are smaller than that of the piezoelectric element and the not covered by the film portions of the piezoelectric element are bonded to the membrane.
• the film acts as a spacer in this embodiment and prevents excess adhesive outside the edge region of the piezoelectric element to an unwanted connection between the membrane and the
• Piezo element leads.
• an adhesive is used which has a large shear modulus after curing, so that a force transmission can take place from the piezoelectric element to the oscillating surface of the membrane.
• Piezoceramic must be ensured on the membrane, a film arranged between the membrane and piezoelectric element can be glued in the middle, each with a glue point with the membrane and the piezoelectric element.
• a film with smaller dimensions than the piezoelectric element is used to perform this push-soft.
• a slide-soft film deforms when thrust forces occur, so that no or no appreciable force transmission from the piezoelectric element to the membrane takes place via the non-slip film.
• the connection between the vibrating surface of the membrane and the piezoelectric element may be arranged in the vicinity of the edge of the vibrating surface of the membrane. Since the enclosure of the membrane usually has a high rigidity and contributes little to the generation of the sound pressure, it is preferable to arrange a bead between the edge of the oscillating surface of the membrane and the point of the membrane, where it is connected to the piezoelectric element. This avoids that the vibration excitation of the membrane is worked against its enclosure and energy is lost unused.
• the edge of the vibrating surface of the membrane without beading or thickening.
• the beading is by reduction the material thickness is formed on the vibrating surface of the membrane.
• Design options of the bead are, for example, bulges or depressions on the vibrating surface of the membrane.
• the at least one thickening can be formed by increasing the material thickness of the membrane.
• the membrane of the sound transducer according to the invention may be made of a metal, a ceramic or a composite material, such as a fiber-plastic composite material.
• the membrane is made of a metal, in particular of aluminum.
• the piezoelectric element preferably comprises a piezoelectric ceramic, it being possible for a plurality of layers to be arranged to form a piezoelectric stack.
• the sound transducer can in the area below the piezoelectric element and in the area between the piezoelectric element and the edge of the housing a
• Damping material can be arranged.
• a non-conductive elastomer is preferably used. Due to the additional damping is a
• Receiving element is used, a short time after the transmission of a sound pulse is ready to receive echoes.
• the resonant frequency of the transducer can be adjusted by arranging beads or thickenings, the choice of shape, material and thickness of the membrane, and optionally by the shape and length of the webs.
• the Sound transducer according to the invention broadband by reducing the oscillating mass.
• FIGS. 1 a
• 1 b show an embodiment of the sound transducer according to the invention, in which the piezoelement is connected via webs to the oscillating surface of the membrane,
• FIG. 2 a shows a bead arranged on the oscillating surface of the membrane
• FIG. 2b shows a thickening arranged on the oscillating surface of the diaphragm.
• An embodiment of the sound transducer in which a foil is arranged between the piezoelement and the diaphragm shows a further embodiment of the sound transducer with a foil between the piezoelement and the diaphragm
• Figure 5 shows an embodiment of the transducer with film, wherein the film is glued with a glue dot in the middle with the membrane and the piezoelectric element, shows a sound transducer with a arranged between the membrane and piezoelectric element film, the film soft is and is glued surface to the piezo element and the membrane,
• FIGS. 7a are identical to FIGS. 7a.
• FIG. 7b and FIG. 7b show various embodiments of the sound transducer in which damping material has been arranged below the piezoelectric element.
• Figure 7c shows a sound transducer, in which in between the webs, the
• Piezoelement and the membrane formed space filling material is added for damping.
• Figures 1 a and b show a transducer in which the piezoelectric element is connected via webs with the membrane.
• the sound transducer 10 comprises a membrane 12 which is shown in FIG.
• Embodiment is configured tpfformig.
• the oscillating surface 13 of the membrane 12 is here in the resting state, that is flat without stimulation to swing. In other embodiments of the invention, a curved configuration of the oscillating surface 13 is conceivable.
• webs 24 are arranged, at the ends of a piezoelectric element 14 is received by bonds 18. The position of the webs 24 is chosen so that they do not touch the edge 15 of the membrane, but allow bonding to the edge region 17 of the piezoelectric element 14.
• both the piezoelectric element 14 and the vibrating surface 13 of the membrane 12 are shown in their respective states of rest.
• the piezoelectric element 14 is electrically excited and then, depending on the frequency and strength of the exciting alternating electrical field, oscillates along the direction indicated by the reference numeral 28.
• the reference numeral 28 is about the connections of the piezoelectric element 14 with the vibrating surface 13 of the diaphragm 12 while thrust forces on the
• the piezoelectric element 14 is shown in a contracted state. Excited by an alternating electrical field, the piezoelectric element 14 contracts in the direction indicated by reference numeral 28. The shear forces occurring are transmitted via the connection of the piezoelectric element 14 to the vibrating surface 13 of the membrane 12 to the membrane 12. In the illustrated embodiment, the connection via the webs 24 and the bonds 18 is ensured. Due to the contraction of the Piezoelectric element 14, the oscillating surface 13 of the membrane 12 bulges. The frequency of this oscillation corresponds to the frequency of the electric field with which the
• Piezo element 14 is excited.
• the vibration of the diaphragm 12 causes
• the vibrating surface 13 of the membrane 12 can be excited by the sound waves from the air to vibrate and transmitted to the piezoelectric element 14 via the webs 24 and bonding 18.
• the piezoelectric element 14 is in this case the
• FIG. 2a shows a membrane 12 of a sound transducer, on which a bead is arranged.
• the membrane 12 of a sound transducer 10 has an edge 15 and a vibrating surface 13.
• webs 24 are provided in the vicinity of the edge 15 via which the edge region 17 of a piezoelectric element 14 is connected to the membrane 12 via an adhesive bond 18.
• vibrations are generated which are transmitted via the bond 18 and the web 24 to the oscillating surface 13 of the membrane.
• the stiffness of the membrane 12 is increased in the region of its edge 15.
• the bead 30 is designed in the embodiment shown as a reduction of the material thickness. As can be seen from FIG. 2 a, the membrane 12 is made thinner at the point 32 than at the point 34 which is located on the oscillating surface 13 of the membrane 12.
• FIG. 2b shows a membrane 12 of a sound transducer, on which a thickening is arranged.
• FIG. 2b An alternative to the embodiment shown in Figure 2a is shown in Figure 2b.
• a thickening 31 is arranged between the edge 15 and the region of the diaphragm 12 connected to the piezoelement 14 via the web 24.
• Thickening 31 is in the embodiment shown as an increase in material thickness executed.
• the membrane 12 is made thicker, for example at the point 33, than at the point 34 which is located on the oscillating surface 13 of the membrane 12.
• the embodiment shown in FIG. 2b is particularly advantageous at high resonance frequencies, since the thickening 31 in the region between the edge 15 and the region of the diaphragm 12 connected to the piezoelectric element 14 via the web 24 provides greater stability and thus greater rigidity.
• FIG. 3 shows a sound transducer in which a film is arranged between the piezoelement and the membrane.
• the transducer 10 has a membrane 12, which in the illustrated
• Embodiment is designed pot-shaped, wherein the vibrating surface 13 of the membrane 12 is configured flat in the idle state.
• a film 16 is arranged, which is a piezoelectric element 14 of the
• the film 16 and the piezoelectric element 14 are made smaller than the vibrating surface 13, so that both do not touch the edge 15 of the membrane 12.
• adhesive bonds 18 are provided for the connection between the vibrating surface 13, the film 16 and the piezoelectric element 14 adhesive bonds 18 are provided.
• Adhesive bonds 18 are present exclusively in the edge regions 17 of the piezoelectric element 14. The largest part of the membrane facing surface of the piezoelectric element 14 is not glued.
• the material of the film 16 and the adhesive used are chosen so that they are suitable for transferring shear forces, which are generated during the excitation of the piezoelectric element 14 via an electric field, to the vibrating surface 13 of the membrane 12.
• FIG. 4 shows a further embodiment of the sound transducer in which a film is arranged between the piezo element and the oscillating surface of the membrane, wherein the surface of the film is smaller than that of the piezo element.
• a film 16 is again recorded.
• the surface of the film 16 is chosen so that it does not completely cover the surface of the piezoelectric element 14.
• the film 16 acts as a spacer to regulate the distance of the piezoelectric element 14 to the vibrating surface 13 of the membrane 12. Furthermore, the film 16 prevents adhesive 18 from flowing beyond the edge region 17 of the piezoelectric element 14.
• Excess adhesive 18 flows out of the space between piezo element 14 and diaphragm 12.
• the adhesive 18 is chosen so that after its curing a rigid connection between the edge regions 17 of the piezoelectric element 14 and the vibrating surface 13 of the membrane 12 is formed, so that upon electrical excitation of the piezoelectric element 14 thrust forces can be transferred to the membrane 12.
• FIG. 5 shows a variant of the transducer with a film between the piezoelectric element and the membrane.
• the sound transducer 10 shown in Figure 5 comprises a diaphragm 12 having a vibrating surface 13.
• a piezoelectric element 14 On the underside of the vibrating surface 13 is a piezoelectric element 14, wherein a film 16 whose area is smaller than the surface of the piezoelectric element 14, serves as a spacer.
• About adhesive bonds 18, the piezoelectric element 14 is connected at its edge region 17 with the vibrating surface 13 of the membrane 12.
• Additional adhesive dots 20 are each arranged between the oscillating surface 13, the film 16 and the piezoelectric element 14, wherein the adhesive dots 20 are located in the region of the center of the piezoelectric element 14. Due to the additional adhesive dots 20 is in this
• Embodiment of the transducer 10 according to the invention a lifting of the
• FIG. 6 shows a further variant of a sound transducer in which between
• the sound transducer 10 comprises a membrane 12 with a vibrating surface 13 on the underside of a piezoelectric element 14 is arranged, wherein a film 16 between the piezoelectric element 14 and the vibrating surface 13 of the membrane 12 serves as a spacer. At the edge regions 17, the piezoelectric element 14 is connected to the vibrating surface 13 of the membrane 12 via bonds 18.
• a soft material is used for the film 16.
• FIGS. 7 a and b show embodiments of the sound transducer in which damping material is arranged below the piezo element 14.
• Figure 7a shows a transducer 10 in which between the piezoelectric element 14 and the
• Membrane 12 a film 16 is added. By bonding 18 between membrane 12, film 16 and piezoelectric element 14 in the region of the edges 17 of the piezoelectric element 14, a force transmission from the piezoelectric element 14 to the membrane 12 is ensured. Will that be
• Piezo element 14 excited via an alternating electrical field to vibrate these are transmitted via the adhesive bonds 18 and the film 16 to the membrane 12.
• Damping material 36 arranged.
• damping material 36 in particular non-conductive elastomers are suitable.
• FIG. 7b likewise shows the arrangement of damping material 36 in the free regions adjoining the piezoelectric element 14, but in this embodiment the piezoelectric element 14 is connected to the membrane 12 via webs 24 and adhesive bonds 18.
• FIG. 7 c likewise shows a sound transducer 10 in which the piezoelectric element 14 is connected to the membrane 12 via webs 24 and bonds 18, as in FIG. 7 b.
• the damping material 38 is arranged in a cavity which is formed by the piezoelement 14, the membrane 12 and the webs 24.
• Embodiments as shown in Figures 7b and 7c are combined so that cavities 36, 38 are filled with a damping material.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Mechanical Engineering (AREA)
• Piezo-Electric Transducers For Audible Bands (AREA)

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Citations (7)

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• 2012
  • 2012-02-09 DE DE102012201884A patent/DE102012201884A1/de active Pending
• 2013
  • 2013-01-25 WO PCT/EP2013/051398 patent/WO2013117437A1/fr not_active Ceased

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