JP2006352464A - Acoustic vibration generating element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remedy the lowering of the band of the frequency of an acoustic vibration generating element for a loudspeaker for bone conduction, the deterioration of a mechanical Q, and a sound leakage. <P>SOLUTION: A piezoelectric bimorph element 1 or a piezoelectric unimorph element 1 and a flexible substance 2 are compounded, and the reduction of a generating vibrating force associated with the compounding can be prevented by forming notches 3 to the flexible substance. A countermeasure for the sound leakage is more effective by fitting an air chamber near a surface. When a vibration generating part and a hunger to an ear are constituted integrally, the lightweight acoustic vibration generating element can be provided for the loudspeaker for the bone conduction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an acoustic vibration generating element for bone conduction application such as a bone conduction speaker for converting an acoustoelectric signal into acoustic vibration and propagating it to a skull or arm and listening to it with an auditory nerve.

  Conventionally, as an electro-mechanical transducer for bone conduction, the electromagnetic type is mainly used, and the driving force generated by the interaction between the magnet and the current flowing through the coil of the same principle as the dynamic speaker is changed to mechanical vibration. Several proposals such as Document 1 and Patent Document 2 have been made. The generated force of the electromagnetic system is an electromagnetic force and requires an electric current, but energy loss is caused by the resistance of the winding, and most of the energy supplied from the power source is lost as Joule heat and used as acoustic energy There was a drawback that the minute was only 1%. Also, in the low frequency range, due to the low impedance, the current tends to be excessive and the load on the power supply side is large. As a result, the output must be limited in the low frequency range, so the low frequency range tends to be insufficient in sound output. There was a drawback.

  On the other hand, although there are a few, for example, there are proposals of bone conduction transducers using piezoelectric elements as in Patent Documents 3 and 4. In this case, a piezoelectric unimorph element in which a metal plate and a piezoelectric material often used as a piezoelectric sounding body are bonded is used as an acoustic vibration generating element. However, in a practical size, the resonance frequency is 1 kHz or more, so that resonance occurs. There was a drawback that reproduction in the low frequency range below the frequency tends to be insufficient. In addition, since the mechanical quality factor Q of the vibration system is high, the occurrence of vibration at a specific frequency is emphasized, and conversely, the natural sound cannot be reproduced because the vibration is attenuated.

  Furthermore, in bone conduction applications where the target is not a hearing impaired person but a normal hearing person, the requirement for the bone conduction speaker is that no sound is leaked to anyone other than the user. There is a drawback that the vibration of the structure receiving the vibration propagates to the surroundings as sound.

Japanese Patent No. 2967777 Japanese Patent No. 3358086 JP 59-140796 A JP 59-178895 A

  In the application of the piezoelectric element to bone conduction, when the low sound range is important, the resonance frequency on the piezoelectric vibrator side needs to be as low as possible. As means for lowering the resonance frequency of the piezoelectric element, there are methods such as increasing the diameter and length of the element that determines vibration, lowering the bending elastic modulus of the element, and adding mass to the antinode portion of the vibration. . However, when the target is a portable device and the size is limited, there is a limit to the method of increasing the element size.

  Another way to lower the flexural modulus can be achieved by reducing the thickness of the piezoelectric ceramic or metal plate (shim plate) sandwiched in the center, but at the same time lowering the mechanical strength and its own weight Since the resonance frequency is increased by reducing the weight, there is no substantial effect. In addition, it is possible to lower the elastic modulus of bending to some extent by selecting a material with a small elastic modulus of organic matter as a shim.However, since the specific gravity of these materials is generally small, the weight of the entire vibrator decreases, The resonance frequency tends to increase. Moreover, when adding mass, there exists a problem that intensity | strength becomes weak easily with respect to an impact vibration.

  However, in the piezoelectric method, since the driving force source of mechanical vibration is in piezoelectric distortion and driven by voltage, there is no loss of Joule heat due to winding like the electromagnetic method, which saves energy, Since there is no need for metal fittings such as a yoke, there are many advantages such as being able to be reduced in weight and being able to be thinned, and there are problems in overcoming the drawbacks such as high resonance frequency and high mechanical Q. Met. In addition, countermeasures against sound leakage to the surroundings are an important issue that cannot be avoided in practical use of bone conduction regardless of electromagnetic type or piezoelectric type. In order to further exhibit the piezoelectric characteristics, the energy loss on the circuit side can be suppressed by making the input voltage for driving as low as possible.

  Furthermore, the bone conduction speaker is mainly used by being mounted on the head of a human body, but it is desirable for the user to be as light and simple as possible.

  Therefore, the technical problem of the present invention is to reduce the frequency of the bone conduction speaker, lower the mechanical Q, and improve sound leakage.

  According to the present invention, a flexible material member is arranged on at least one of two surfaces perpendicular to the thickness direction of the piezoelectric bimorph element or the piezoelectric unimorph element, and the flexible material member is provided with the flexible material member. An acoustic vibration generating element for bone conduction application, characterized in that a cut is formed, is obtained.

  According to the present invention, the piezoelectric bimorph element or the piezoelectric unimorph element is entirely covered with a flexible material member, and the flexible material member is cut. An acoustic vibration generating element for bone conduction application is obtained.

  Further, according to the present invention, there is obtained an acoustic vibration generating element for bone conduction application, wherein the cut is formed in parallel with a line connecting portions having equal vibration displacements of the acoustic vibration generating element. .

  Further, according to the present invention, an acoustic vibration generating element for bone conduction can be obtained, wherein the incision is processed by a processing machine or formed by a molding die.

  Further, according to the present invention, the flexible material member is arranged only on one surface perpendicular to the thickness direction of the piezoelectric bimorph element or the piezoelectric unimorph element, and the flexible material member is formed with a groove. Thus, an acoustic vibration generating element for bone conduction application can be obtained.

  Further, according to the present invention, there is obtained an acoustic vibration generating element characterized in that the groove is formed in parallel with a line connecting portions having equal vibration displacements of the acoustic vibration generating element.

  Further, according to the present invention, an acoustic vibration generating element for bone conduction application is obtained, wherein the groove is formed by a processing machine or a mold for molding a flexible substance. It is done.

  Furthermore, according to the present invention, an acoustic vibration generating element for bone conduction application is obtained, wherein the piezoelectric bimorph element or the piezoelectric unimorph element is a laminated structure of piezoelectric ceramics and internal electrodes.

  Furthermore, according to the present invention, an acoustic vibration generating element for bone conduction application, wherein an air chamber is provided on the surface of the flexible material member, is obtained.

  Furthermore, according to the present invention, there is obtained an acoustic vibration generating element for bone conduction application, wherein a part of the flexible material member constitutes an ear hook portion.

  According to the present invention, the resonance frequency of the bone conduction speaker can be lowered, and the mechanical Q can be lowered. Furthermore, it is possible to provide an acoustic vibration generating element for a bone conduction speaker that improves sound leakage and at the same time has a wide sound range. In addition, it is possible to provide an acoustic vibration generating element for a bone conduction speaker that can reduce the impact at the time of dropping, has a robust structure, and is lightweight.

  Next, an embodiment of an acoustic vibration generating element according to the present invention will be specifically described based on the drawings.

  FIG. 1A, FIG. 1B, and FIG. 1C are perspective views showing the basic configuration of the acoustic vibration generating element of the present invention. FIG. 1A shows an acoustic vibration generating element having a structure in which a flexible substance 2 is attached to two surfaces perpendicular to the thickness direction of a rectangular piezoelectric bimorph or piezoelectric unimorph 1. FIG. 1B shows an acoustic vibration generating element having a structure in which the entire surface of a rectangular piezoelectric bimorph or piezoelectric unimorph 1 is covered with a flexible material. Further, FIG. 1C shows an acoustic vibration generating element having a structure in which the entire surface of a circular piezoelectric bimorph or piezoelectric unimorph 1 is covered with a flexible material.

  FIG. 2 is a cross-sectional view in the thickness direction of the acoustic vibration generating element of the present invention shown in FIGS. 1 (a) to 1 (c). In addition, the case where a piezoelectric bimorph is used as an acoustic vibration generating element is shown. The piezoelectric bimorph 1 has a layered structure in which a shim 1b is sandwiched between piezoelectric ceramics 1a and the outer layer is covered with a flexible material 2. In this case, the resonance frequency Fr of the acoustic vibration generating element is different depending on the shape and the support type. α is a numerical value determined by the vibration type, and is 4.73 in the first-order resonance. l is the length of the piezoelectric bimorph element, K is the elastic modulus of bending, and ρs is the weight per unit length.

  The elastic modulus K of the bending of the acoustic vibration generating element is determined on both sides in addition to the width w of the piezoelectric ceramic and shim plate constituting the piezoelectric bimorph element, the thicknesses tc and 2ts, and the elastic coefficients Ec and Es. It is governed by the thickness tp of the flexible material to be added, the elastic modulus Ep, and the like, and is expressed by Equation 2.

  Further, the weight ρ S per unit length is governed by the thicknesses tc, 2ts, tp and specific gravity ρc, ρs, ρp of the piezoelectric ceramic, shim plate and flexible material constituting the acoustic vibration generating element, and the width w of the bimorph element. And expressed by equation (1).

  ρS = 2w (ρptp + ρctc + ρsts) (1)

Therefore, when a layer made of a flexible material is newly added to both surfaces of the piezoelectric bimorph element, the bending elastic modulus K and the weight ρS per unit length are changed as a result, so that the resonance frequency is affected. Depending on the flexible material selected, the resonance frequency may increase. However, a flexible material having a small elastic coefficient of about 3 to 8 × 10 ⁶ Pa, such as rubber, may be used. When used, the total flexural modulus K increases with the addition of a new layer, but the rate of increase is small compared to the rate of increase in weight ρS per unit length. The resonance frequency decreases.

  FIG. 3 is a graph showing this state. FIG. 3 is a graph showing the relationship between the thickness of the attached flexible material and the resonance frequency of the acoustic vibration generating element. In the graph, the horizontal axis indicates the thickness of the flexible material, and the vertical axis indicates the resonance frequency. FIG. 3 shows the case where silicon rubber is used as the flexible material pasted. FIG. 3 shows that the resonance frequency of the acoustic vibration generating element is lowered by applying a flexible substance to the piezoelectric bimorph element.

  In addition, since sound energy for bone conduction application is radiated in close contact with human skin, it is necessary to match the acoustic impedance between the acoustic vibration generating element and human skin. The flexible material is also effective in terms of matching this acoustic impedance.

  Using the above principle, the acoustic vibration generating element according to the present invention has a structure in which a slit is formed in the flexible material or a groove is formed in addition to the basic structure described above. FIG. 4A is a perspective view showing an embodiment of an acoustic vibration generating element according to the present invention. A flexible material 2 is bonded to two surfaces perpendicular to the thickness direction of the piezoelectric bimorph or piezoelectric unimorph element 1, and a cut 3 is formed in the flexible material 2.

  FIG. 4B is a perspective view showing another embodiment of the acoustic vibration generating element according to the present invention. The entire surface of the piezoelectric bimorph or piezoelectric unimorph element 1 is covered with a flexible material 2, and a cut 3 is formed in the flexible material 2 on two surfaces perpendicular to the thickness direction.

  This notch 3 is formed in parallel to a line connecting portions having the same displacement when the piezoelectric bimorph or piezoelectric unimorph element 1 is driven. FIG. 5 is a perspective view showing a displacement state when the piezoelectric bimorph or piezoelectric unimorph element 1 is driven. At a certain moment when a voltage is applied to the piezoelectric bimorph or piezoelectric unimorph element 1, as shown in FIG. 5, assuming that no voltage is applied as a reference 4, the central portion is a reference 4 as indicated by a displacement direction 6. In contrast, the left and right end portions are displaced downward relative to the reference 4 as indicated by the displacement direction 7. At this time, an equal displacement amount line 5 can be drawn by connecting the portions where the displacement amounts are equal to each other on a plane perpendicular to the thickness direction of the piezoelectric bimorph or piezoelectric unimorph element 1. In the present invention, the cut is formed so as to be parallel to the equal displacement amount line 5.

  By this cutting, the elastic coefficient K of the flexible material layer is apparently reduced, and the resonance frequency can be lowered according to the principle described above.

  Furthermore, the mechanical Q of the vibrating body is reduced, the sound range is widened, and in addition, when the piezoelectric bimorph element is covered with a flexible material, an effect of reducing sound leakage that radiates unnecessary sound to the surroundings can be obtained. .

  The rectangular acoustic vibration generating element has been described above as an example, but naturally the same effect can be obtained even when a circular piezoelectric bimorph element or piezoelectric unimorph element is used.

  FIG. 4C is a perspective view showing an embodiment of an acoustic vibration generating element using a circular piezoelectric bimorph element or a piezoelectric unimorph element in the present invention. The entire surface of the circular piezoelectric bimorph element or piezoelectric unimorph element 1 is covered with a flexible material 2, and a cut 3 is formed in the flexible material 2 on two surfaces perpendicular to the thickness direction. As described above, the notch 3 is formed so as to be parallel to a line connecting portions having the same displacement when the piezoelectric bimorph element or the piezoelectric unimorph element 1 is driven. In this case, the line connecting the portions having the same amount of displacement draws a concentric circle on two surfaces perpendicular to the thickness direction of the piezoelectric bimorph element or the piezoelectric unimorph element 1, and therefore the notch 3 formed parallel to the concentric circle is also drawn. Draw.

  The incision may be formed by a processing machine such as a blade or a cutting machine, but it is molded by a mold that has been cut in advance in a mold used for molding a flexible substance. May be.

  Furthermore, the present invention also proposes an acoustic vibration generating element that can obtain the same effect as the above-described embodiment.

  FIG. 6 is a perspective view showing a further embodiment of the acoustic vibration generating element according to the present invention. A flexible material 2 is bonded to only one surface perpendicular to the thickness direction of the piezoelectric bimorph or piezoelectric unimorph element 1, and a groove 8 is formed in the flexible material 2. The groove 8 is formed in parallel to a line connecting portions having the same amount of displacement when the piezoelectric bimorph or piezoelectric unimorph element 1 is driven, as in the case of the above-described notches. The difference between the groove 8 and the above-described notch is in its cross-sectional shape. That is, the cross section of the above-described notch is formed in a linear shape having no area, whereas the cross section of the groove 8 is formed so as to have an area. FIG. 6 shows an embodiment in which the groove 8 has a V-shaped cross section and has a triangular area.

  The groove 8 may be formed by a processing machine such as a blade or a cutting machine, as in the case of the above-described cutting. However, the groove 8 is preliminarily processed to be cut into a mold used for molding a flexible material. You may shape | mold with the mold which did it.

  Hereinafter, the acoustic vibration generating element of the present invention will be described in more detail with specific examples.

  Two piezoelectric elements with a length of 30 mm, a width of 8 mm, and a thickness of 0.15 mm using NEC TOKIN piezoelectric ceramics (trade name Nepec 10) and a brass shim plate with the same outer dimensions and a thickness of 50 μm are epoxy-based. A piezoelectric bimorph element having a structure bonded with an adhesive, and two piezoelectric elements in which three piezoelectric ceramic layers having a thickness of 50 μm and a thin internal electrode layer are stacked in the thickness direction are used instead of the piezoelectric element. A piezoelectric bimorph element was prepared. The former is called a single plate structure, and the latter is called a laminated structure. For each piezoelectric bimorph element, a lead wire is provided on the outer surface of the shim and both sides of the ceramic, and when the same electric field as the polarization direction is applied to one piezoelectric element, the other piezoelectric element is connected so that the opposite electric field is applied. is there.

  Next, a silicon rubber solution is poured onto the entire surface of the bimorph element using a brass mold, and by curing, the two surfaces in the thickness direction are 2 mm thick, the width direction is 1 mm thick, and the bimorph element is covered with a rubber coating. An acoustic vibration generating element having a structure shown in FIG. 1B without covering and notching was produced. As for these, in the case of a single plate structure, when an acoustic signal of about 18 Vrms is inputted and one of these is pressed against the head, a clear bone conduction voice can be confirmed. In the laminated structure, the same level of output was obtained at 6 Vrms, which is about 1/3 of the input. Further, in order to evaluate the sound leaking to the outside in this case, the sound pressure of 100 Hz to 10 kHz was measured at a distance of 50 cm in an anechoic chamber and found to be 50 dB or less, and it was confirmed that sound leakage was extremely small.

  Next, in order to quantitatively confirm the acoustic effect of a flexible substance, the acceleration at the position corresponding to the auditory nerve of the human body is not covered using a cochlear implant (Artificial Mastoid Type 4930 manufactured by B & K). And after coating, the two were compared. The magnitude of acceleration in the inner ear is proportional to the intensity of the acoustic signal received by the auditory nerve.

  FIG. 7 is a graph showing measurement results of acceleration measured with the cochlear implant. The horizontal axis represents frequency and the vertical axis represents acceleration. As is clear from the graph of FIG. 7, the acceleration of the acoustic vibration generating element covered with silicon is improved by increasing the output in the low frequency range as compared with the acoustic vibration generating element not covered with silicon. Further, it can be confirmed that the sharpness of the resonance part is lost and the resonance part is greatly relaxed.

  Therefore, incisions having a depth of 0.5 mm are formed at intervals of 2 mm in the two silicon rubber portions perpendicular to the thickness direction of the acoustic vibration generating element by machining, and the acoustic vibration having the structure shown in FIG. A generating element was produced.

  Similarly, the acceleration of the acoustic vibration generating element was measured using a cochlear implant. FIG. 8 is a graph showing the measurement results of acceleration. As can be seen from the graph of FIG. 8, the acceleration of the acoustic vibration generating element having the cut according to the present invention is larger than that of the acoustic vibration generating element having no cut, and the acceleration on the low frequency side is also increased. I know that.

  Two piezoelectric elements with a diameter of 30 mmφ and a thickness of 0.15 mm using NEC TOKIN piezoelectric ceramics (trade name Nepec 10) and a brass shim with the same outer dimensions and a thickness of 50 μm are bonded together with an epoxy adhesive. A piezoelectric bimorph element having the structure described above and two piezoelectric elements in which three piezoelectric ceramic layers having a thickness of 50 μm and a thin internal electrode layer are laminated in the thickness direction are used instead of the piezoelectric element. Got ready. The former is called a single plate structure, and the latter is called a laminated structure. For each piezoelectric bimorph element, a lead wire is provided on the outer surface of the shim plate and the ceramics on both sides, and when the same electric field as the polarization direction is applied to one piezoelectric element, the other piezoelectric elements are connected so that the opposite electric field is applied. is there.

  Next, a silicon rubber solution is poured onto the entire surface of the bimorph element using a brass mold, and by curing, the two surfaces in the thickness direction are 2 mm thick, the width direction is 1 mm thick, and the bimorph element is covered with a rubber coating. Covering and further machining were performed to form concentric cuts at a depth of 0.5 mm and at intervals of 2 mm, thereby producing an acoustic vibration generating element having the structure shown in FIG. With regard to these, when an acoustic signal of about 18 Vrms is input for the single plate structure and about 6 Vrms for the laminated structure and these one side is pressed against the head, a sound by clear bone conduction can be confirmed. Also in this case, in order to evaluate the sound leaking to the outside, the sound pressure of 100 Hz to 10 kHz was measured at a distance of 50 cm in an anechoic chamber and found to be 50 dB or less, and it was confirmed that the sound leakage was extremely small.

  Next, in order to confirm the effect of the flexible substance and the incision, using the cochlear implant (Artificial Mastoid Type 4930 made by B & K), the state where the acceleration corresponding to the auditory nerve of the human body is not covered and the incision after the covering is performed. What was formed was measured and compared.

  FIG. 9 is a graph showing measurement results of acceleration in the cochlear implant. The horizontal axis represents frequency and the vertical axis represents acceleration. As is clear from FIG. 9, it was confirmed that the acceleration of the acoustic vibration generating element according to the present invention was extended even in a low frequency range and the sharpness of the resonance part was greatly relaxed. Note that the effects of frequency reduction, Q relaxation, and sound leakage prevention by cutting a flexible material are shown in FIG. The same effect can be obtained even when the structure shown in FIG.

  Two piezoelectric elements with a length of 30 mm, a width of 8 mm, and a thickness of 0.15 mm using NEC TOKIN piezoelectric ceramics (trade name NEPEC 10) and a brass shim plate with the same outer dimensions and thickness of 50 μm are epoxy-based. A piezoelectric bimorph element having a structure bonded with an adhesive, and two piezoelectric elements in which three piezoelectric ceramic layers having a thickness of 50 μm and a thin internal electrode layer are stacked in the thickness direction are used instead of the piezoelectric element. A piezoelectric bimorph element was prepared. The former is called a single plate structure, and the latter is called a laminated structure. For each piezoelectric bimorph element, a lead wire is provided on the outer surface of the shim and both sides of the ceramic, and when the same electric field as the polarization direction is applied to one piezoelectric element, the other piezoelectric element is connected so that the opposite electric field is applied. is there.

  Next, silicon rubber having the same outer dimensions and a thickness of 2 mm is prepared, and only one surface perpendicular to the thickness direction of the bimorph element is pasted, and then the depth at which the cross section becomes V-shaped by machining in the silicon rubber portion A 2 mm groove was formed to produce an acoustic vibration generating element having the structure shown in FIG. As for these, in the case of a single plate structure, when an acoustic signal of about 18 Vrms is inputted and one of these is pressed against the head, a clear bone conduction voice can be confirmed. In the laminated structure, the same level of output was obtained at 6 Vrms, which is about 1/3 of the input. Further, in order to evaluate the sound leaking to the outside in this case, the sound pressure of 100 Hz to 10 kHz was measured at a distance of 50 cm in an anechoic chamber and found to be 50 dB or less, and it was confirmed that sound leakage was extremely small.

  Further, the acoustic vibration generating element was measured by the cochlear implant described in the above-described embodiment.

  FIG. 10 is a graph showing measurement results of acceleration measured with the cochlear implant. The horizontal axis represents frequency and the vertical axis represents acceleration. As is apparent from FIG. 10, the acceleration value of the acoustic vibration generating element according to the present invention is larger than that of the conventional acoustic vibration generating element, and the acceleration on the low frequency side is also increased.

  FIG. 11 is a cross-sectional view of an acoustic vibration generating element provided with an air chamber according to the present invention. For the acoustic vibration generating element prototyped in Example 2, a rubber-based circular ring (30 mmφ × 25 mmφ × 1 mm) of the same diameter and a disc (30 mmφ × 1 mm) of the same material are sequentially bonded to one surface. An air chamber 9 of 25 mmφ × 1 mm was provided on the surface on one side of the pasting using an agent. When an audio signal is input by pressing the surface on the side where the air chamber 9 is not formed as an output surface against a part of the face, sound leakage from the open surface on one side is reduced due to the presence of the air chamber 9.

  In the present embodiment, a rubber ring and a disk are used to form the air chamber 9, but it is also possible to form the air chamber 9 integrally with the flexible material to be coated. The effect is the same even if it becomes a connected structure. Needless to say, this effect is the same in the case of a rectangular shape regardless of the shape of the piezoelectric bimorph element.

  FIG. 12 is a view showing an acoustic vibration generating element in which an ear hook portion is integrally formed as a part of a flexible material covering a piezoelectric bimorph or a piezoelectric unimorph according to the present invention. This is an acoustic vibration generating element 10 in which an ear hook is integrally formed of the piezoelectric bimorph element 1 used in Example 1 and a covering silicon rubber. Moreover, FIG. 13 shows the state with which it was mounted | worn with the ear | edge of a human body. As shown in FIG. 13, when wearing and inputting an electrical signal, the cartilage of the outer ear and the skull behind the ear can be simultaneously stimulated, and the sound due to bone conduction can be heard more clearly.

  As described above, according to the present invention, an acoustic vibration generating element having a high sound pressure capable of reducing the frequency of the bone conduction speaker, lowering the mechanical Q, and further improving sound leakage can be obtained.

The perspective view which shows the basic composition of this invention. 1A is a perspective view of a configuration in which a flexible material is attached to both sides, FIG. 1B is a perspective view of a configuration in which a piezoelectric element is covered with a flexible material, and FIG. 1C is a circular shape. The perspective view of the structure which covered the piezoelectric element front surface with the flexible substance. Sectional drawing of the acoustic vibration generating element of this invention. The graph which shows the resonant frequency change of the acoustic vibration generating element of this invention. The perspective view which shows the acoustic vibration generating element of this invention. 4A is a perspective view of a configuration in which a flexible material is attached to both surfaces, FIG. 4B is a perspective view of a configuration in which a piezoelectric element is entirely covered with a flexible material, and FIG. 4C is a circular shape. The perspective view of the structure which covered the piezoelectric element entirely with the flexible substance. The perspective view explaining the displacement of a piezoelectric bimorph element or a piezoelectric unimorph element. The perspective view which shows the acoustic vibration generating element of this invention. The graph which shows the acceleration in the cochlear implant of the acoustic vibration generating element by basic composition. 3 is a graph showing acceleration in the cochlear implant of Example 1. 6 is a graph showing acceleration in the cochlear implant of Example 2. 10 is a graph showing acceleration in the cochlear implant of Example 3. Sectional drawing of the acoustic vibration generating element which provided the air chamber of Example 4. FIG. The figure which shows the acoustic-vibration generating element which integrally molded the ear hook part of Example 5. FIG. The figure which shows the state with which the human body of Example 5 was mounted | worn.

Explanation of symbols

1 Piezoelectric bimorph element or piezoelectric unimorph element 2 Flexible material 3 Cutting
4 Reference 5 Equal displacement curve 6 Displacement direction 7 Displacement direction 8 Groove 9 Air chamber 10 Acoustic vibration generating element 1a having a hooked structure made of a flexible substance Piezoelectric ceramics 1b Shim material

Claims (10)

  A structure in which a flexible material member is arranged on at least one of two surfaces perpendicular to the thickness direction of the piezoelectric bimorph element or the piezoelectric unimorph element, and a cut is formed in the flexible material member. An acoustic vibration generating element for bone conduction application.   An acoustic vibration generating element for bone conduction application, wherein a piezoelectric bimorph element or a piezoelectric unimorph element is covered with a flexible material member, and the flexible material member is cut.   3. The acoustic vibration generating element for bone conduction application according to claim 1, wherein the cut is formed in parallel with a line connecting portions having equal vibration displacement amounts of the acoustic vibration generating element.   4. The acoustic vibration generating element for bone conduction application according to claim 1, wherein the cut is formed by a processing machine or a molding die. 5.   Bone conduction characterized in that a flexible material member is disposed only on one surface perpendicular to the thickness direction of the piezoelectric bimorph element or piezoelectric unimorph element, and a groove is formed in the flexible material member. Applied acoustic vibration generating element.   6. The acoustic vibration generating element for bone conduction application according to claim 5, wherein the groove is formed in parallel with a line connecting portions having equal vibration displacements of the acoustic vibration generating element.   The acoustic vibration generating element for bone conduction application according to claim 5 and 6, wherein the groove is formed by processing with a processing machine or by a molding die.   The acoustic vibration generating element for bone conduction application according to any one of claims 1 to 7, wherein the piezoelectric bimorph element or piezoelectric unimorph element is a laminated structure of piezoelectric ceramics and internal electrodes.   The acoustic vibration generating element for bone conduction application according to any one of claims 1 to 8, wherein an air chamber is provided on the surface of the flexible material member.   The acoustic vibration generating element for bone conduction application according to any one of claims 1 to 9, wherein a part of the flexible material member constitutes an ear hook portion.

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