JP2007275819A - Piezoelectric vibration unit and piezoelectric loudspeaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric vibration unit which has high impact resistance, from which high sound pressure and excellent frequency characteristics and sound quality are obtained and which is made compact, and to provide a piezoelectric loudspeaker. <P>SOLUTION: The piezoelectric vibration unit is constituted so that a piezoelectric vibrator 31 is housed in a first casing 32 and a second casing 33 and a first elastic body 34 and a second elastic body 35, which are different in hardness, are packed respectively in the casings. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a piezoelectric vibration unit for generating acoustic vibrations for imparting vibration to a panel or casing to function as a speaker, and particularly suitable for vibrating a panel or casing of a mobile phone or other portable device. It relates to a vibration unit.

  A speaker used as an acoustic device uses a voice coil and a magnet, and in addition to an electromagnetic speaker that vibrates a diaphragm with an electromagnetic force generated according to a current flowing through the voice coil by an electroacoustic signal, an electric acoustic signal There is a piezoelectric speaker that utilizes a reverse piezoelectric effect of a piezoelectric vibrator that generates a distortion corresponding to the voltage of the panel, and vibrates a panel or a housing using the distortion as a driving source.

  A piezoelectric vibrator called a piezoelectric bimorph is mainly used as a piezoelectric vibrator as a driving source for vibrating the panel and the casing. This is because two plate-shaped piezoelectric ceramic plates are joined so as to sandwich a plate-shaped elastic plate, and one of the two piezoelectric ceramic plates expands in the plane direction or extends. In addition, when an electric field is applied, the other piezoelectric ceramic plate is configured to be applied with an electric field so that the other piezoelectric ceramic plate is contracted or contracted in a plane direction, and is configured to generate displacement and distortion of bending. Piezoelectric vibrator.

  Since this piezoelectric bimorph has a small structure, its resonance frequency can be easily set in the audible sound frequency range by design. In addition, since a large amplitude and a large generation force can be obtained in the audible sound frequency range, it has been widely used as a driving source for piezoelectric speakers, and many proposals of piezoelectric speakers using piezoelectric bimorphs have been made.

  For example, a piezoelectric speaker in which a circular piezoelectric bimorph is fixed to an acoustic diaphragm via a connecting member has been proposed. Such a piezoelectric speaker is disclosed in Patent Document 1. In addition, a piezoelectric speaker in which a rectangular plate-shaped piezoelectric bimorph is fixed to an acoustic diaphragm via a connecting portion has been proposed. Such a piezoelectric speaker is disclosed in Patent Document 2. Furthermore, there has been proposed a piezoelectric vibration unit for a piezoelectric speaker having a structure in which two piezoelectric bimorphs having different rectangular plate lengths are stacked. Such a piezoelectric vibration unit is disclosed in Patent Document 3.

  In these piezoelectric speakers or piezoelectric vibration units, the center of the piezoelectric bimorph is supported as a support point. The vibration generated by the piezoelectric bimorph accompanies the movement of the center of gravity of the piezoelectric bimorph itself, resulting in an inertial force at the support point. This inertial force is a value obtained by multiplying the acceleration of each mass point by the mass, and is obtained as the sum of minute inertial forces generated in the direction opposite to the acceleration. Accordingly, a large amplitude and a large generated force can be obtained.

  In addition, a rectangular plate-shaped piezoelectric bimorph can be supported in a cantilever shape by fixing one end in the longitudinal direction. The inertial force generated at the support point directly acts on one point of the panel or casing that is in contact with the support point to become a vibration drive source for a new vibration system, and to become a speaker that emits sound waves in the air. As the force acting here is stronger, the sound output generated by the loudspeaker becomes larger. Therefore, it has been proposed to use a plurality of piezoelectric bimorphs for generating acoustic vibrations as needed.

JP 2000-209697 A JP 2000-201398 A JP 2004-104327 A

  A plate-like piezoelectric ceramic plate is used for the piezoelectric bimorph described above. The material of the piezoelectric ceramic plate is usually a so-called PZT type piezoelectric ceramic of lead zirconate titanate type. This PZT-based piezoelectric ceramic is a porcelain composition, in other words, a ceramic. Therefore, the mechanical strength is weak, and in particular, there is a problem that the strength is weak against a drop impact.

  In terms of mechanical strength, for example, when an impact is applied to the piezoelectric vibration unit, the end portion of the piezoelectric bimorph located away from the fixed portion holding the piezoelectric bimorph is greatly bent by the impact force, and the piezoelectric There is also a problem due to the structure of the piezoelectric vibration unit in which the fixed portion of the bimorph receives tensile stress and the piezoelectric ceramic plate breaks.

  The mechanical strength required for mounting on a portable device is, for example, a strength that does not break even when dropped on a concrete floor from a height of 1.8 m. For the above-mentioned reason, the unit cannot be said to have sufficient strength, and there is a problem that it is difficult to mount it on a portable device.

  Furthermore, in order to improve mechanical strength, it is conceivable to protect the piezoelectric bimorph by placing it in a case or to cover and protect the entire piezoelectric bimorph with an elastic body, but the former requires space and is downsized. There is a problem that the latter cannot be performed, and the latter has a problem that the operation of the piezoelectric bimorph element is hindered and the sound pressure, frequency characteristics, and sound quality, which are acoustic performances, are deteriorated.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art. Specifically, it is an object of the present invention to provide a piezoelectric vibration unit and a piezoelectric speaker that have high impact resistance, high sound pressure, good frequency characteristics and sound quality, and can be miniaturized.

  The present invention employs the following means in order to solve the above problems. That is, according to the present invention, in a piezoelectric vibration unit in which a piezoelectric vibrator such as a piezoelectric bimorph element or a piezoelectric unimorph element is housed in a housing, elastic bodies having different hardnesses are filled in the surface of the piezoelectric vibrator or the housing. This is the gist.

  According to the present invention, there is provided a piezoelectric vibration unit including a piezoelectric vibrator and a housing that houses and holds the piezoelectric vibrator, and the piezoelectric vibrator includes two or more elastic bodies having different hardness on the surface. Thus, a piezoelectric vibration unit can be obtained.

  The piezoelectric vibration unit according to the present invention uses a piezoelectric vibrator having an electro-mechanical conversion function. The piezoelectric vibrator is a device that uses a so-called piezoelectric ceramic material such as a lead zirconate titanate-based material and generates mechanical acoustic vibration in accordance with an input electrical acoustic signal. The piezoelectric vibrator is housed and held in a housing so as to have a fixed part for holding a part and a free part for acoustic vibration. Of the free part, the part with the largest acoustic vibration, that is, the part with the maximum displacement is called a free end part.

  At this time, two or more elastic bodies having different hardnesses are arranged in advance on the surface of the piezoelectric vibrator. For example, when the piezoelectric vibrator has a plate shape, the elastic body is attached to two surfaces forming the thickness of the piezoelectric vibrator, and two or more elastic bodies having different hardnesses are attached to the same surface. Two or more elastic bodies having different hardnesses are pasted on the other same surface so that the elastic bodies having the same hardness face each other with the piezoelectric vibrator interposed therebetween. This elastic body has the effect of absorbing the impact, and by attaching two or more elastic bodies of different hardness to the piezoelectric vibrator according to the distribution of impact received by the piezoelectric vibration unit, the displacement is not hindered. Can absorb shocks efficiently.

  According to the present invention, there is provided a piezoelectric vibration unit including a piezoelectric vibrator and a housing that houses and holds the piezoelectric vibrator, and is hard in a space formed by an inner wall surface of the housing and the surface of the piezoelectric vibrator. A piezoelectric vibration unit characterized in that it is filled with two or more elastic bodies having different values.

  The piezoelectric vibration unit according to the present invention fills the space between the inner wall surface of the housing and the surface of the piezoelectric vibrator with the elastic body. The elastic body may be disposed on the surface of the piezoelectric vibrator as described above, but the elastic body may be partially or entirely filled in the space formed by the inner wall surface of the housing and the surface of the piezoelectric vibrator. The same effect can be obtained.

  According to the present invention, there is obtained a piezoelectric vibration unit characterized in that the piezoelectric vibrator has a rectangular plate shape, and includes a fixed part to which a part is fixed and a free part that can vibrate. The piezoelectric vibration unit according to the present invention uses a rectangular plate-shaped piezoelectric vibrator and fixes a part of the piezoelectric vibrator. The fixed part is a fixed part, and the unfixed part is a free part. The fixing part can fix the center or the central part of the piezoelectric vibrator in the longitudinal direction or other parts to a point or a line. In addition, since the piezoelectric vibrator has a rectangular plate shape, a useless sbase is not formed with respect to the vibrating body at the time of use. Therefore, the piezoelectric device capable of miniaturizing the device itself on the side where the piezoelectric vibration unit according to the present invention is incorporated. A vibration unit is obtained.

  According to the present invention, it is possible to obtain a piezoelectric vibration unit characterized in that the two or more elastic bodies increase in hardness as they approach the fixed portion. According to the configuration of the present invention, the bending moment M generated in the piezoelectric vibrator when the voltage due to the electrical acoustic signal is applied is uniform from the fixed portion toward the free end portion. When the distance from the fixed portion is L, the bending displacement amount δ generated in this manner has a relationship of δ∝L2, and increases as the free end portion is approached. Further, the generated force F, which can be referred to as the force for preventing the displacement or the force required to maintain the displacement δ at 0, has a relationship of F∝1 / L, and the generated force F is closer to the fixed portion. growing.

  Therefore, the elastic body arranged in the piezoelectric vibrator does not significantly inhibit the displacement amount δ of the piezoelectric vibrator even if the elastic body arranged near the solid portion is harder than the elastic body arranged near the free end. That is, a decrease in acoustic performance can be prevented. On the other hand, when the free end of the piezoelectric vibrator receives an external force in a direction orthogonal to the vibration surface of the piezoelectric vibrator, the largest bending moment is generated in the vicinity of the fixed portion. Arranging an elastic body that is harder than the elastic body disposed near the free end near the fixed portion has the effect of absorbing impact. Therefore, the piezoelectric vibration unit according to the present invention provides a piezoelectric vibration unit having high strength against impact while maintaining the acoustic performance.

  According to the present invention, a piezoelectric vibration unit is obtained in which the piezoelectric vibrator has a cantilever structure. The piezoelectric vibration unit according to the present invention has the advantage that the displacement amount of the free end portion can be maximized by storing and holding the piezoelectric vibrator in the casing so as to have a cantilever structure compared to other holding states. is there. That is, a piezoelectric vibration unit having a large sound pressure and a large generation force can be obtained.

  According to the present invention, there is obtained a piezoelectric vibration unit in which the piezoelectric vibrator is composed of a piezoelectric bimorph element or a piezoelectric unimorph element. The piezoelectric vibration unit according to the present invention can efficiently convert an electrical acoustic signal into a mechanical acoustic vibration by using a piezoelectric bimorph element or a piezoelectric unimorph element as a piezoelectric vibrator. A piezoelectric vibration unit having good acoustic characteristics can be obtained.

  According to the present invention, there is obtained a piezoelectric speaker characterized in that the piezoelectric vibration unit is fixed to a diaphragm. By mounting the piezoelectric vibration unit according to the present invention on a display panel or a casing body of a cellular phone or a portable device, a piezoelectric speaker having high sound pressure, good frequency characteristics, and high impact resistance can be obtained.

  As described above, according to the present invention, it is possible to provide a piezoelectric vibration unit and a piezoelectric speaker that have high impact resistance, high sound pressure, good frequency characteristics and sound quality, and can be miniaturized. Become.

  The piezoelectric vibration unit according to the present invention includes a piezoelectric vibrator such as a piezoelectric bimorph element or a piezoelectric unimorph element housed in a casing. Further, the piezoelectric vibrator surface or the housing is filled with elastic bodies having different hardnesses.

  Hereinafter, specific examples will be given and the piezoelectric vibration unit and the piezoelectric speaker of the present invention will be described in more detail with reference to the drawings.

Example 1
FIG. 1 is an exploded perspective view of a piezoelectric vibration unit according to an embodiment. The piezoelectric vibration unit according to this example is configured by the piezoelectric vibrator 11, the first housing 12, and the second housing 13. A piezoelectric bimorph element was used for the piezoelectric vibrator 11. The piezoelectric bimorph element was manufactured by the following procedure. First, using a piezoelectric ceramic material (N17) manufactured by NEC Tokin Co., Ltd., a single layer of 70 μm green sheet is produced, and a printed film in which an electrode material composed of silver and palladium is printed on one side of the green sheet is produced. The green sheets and the printed film are alternately laminated in the thickness direction, and then pressed while applying heat to produce a laminate.

  Next, the laminate is cut into a rectangular shape and fired to produce a rectangular plate-shaped piezoelectric ceramic plate having a length of 30 mm, a width of 4 mm, and a thickness of 0.2 mm. Next, two piezoelectric ceramic plates are prepared, and the piezoelectric ceramic plates are attached to both surfaces of a metal plate having a length of 30 mm, a width of 4 mm, and a thickness of 0.1 mm with an adhesive. Furthermore, each piezoelectric ceramic plate was subjected to polarization treatment to obtain a piezoelectric bimorph element.

  Furthermore, in the piezoelectric vibration unit according to the present embodiment, as shown in FIG. 1, the first elastic body 14 and the second elastic body 15 are attached to the front and back surfaces of the piezoelectric vibrator 11 made of the piezoelectric bimorph element with a double-sided adhesive tape. Pasted. As the first elastic body 14, a trade name “Polon SR-S-40P” manufactured by INOAC was used. This is an elastic body having a 25% compression ratio of 0.015 (N / mm) in accordance with JIS-K6254. This was processed into a length of 7 mm, a width of 4 mm, and a thickness of 0.5 mm, and pasted so as to avoid a range in which the distance measured from the free end portion 16 of the piezoelectric vibrator 11 toward the fixed portion 17 was 5 mm.

  As the second elastic body 15, a trade name “Polon MS-40P” manufactured by Inoac Co., Ltd. was used. This is an elastic body having a 25% compression rate of 0.054 (N / mm) in accordance with JIS-K6254. This was processed into a length of 7 mm, a width of 4 mm, and a thickness of 1 mm, and affixed next to the first elastic body 14 and close to the fixing portion 17.

  FIG. 2 is a cross-sectional view of the piezoelectric vibration unit according to the embodiment. 2 shows a cross section taken along the broken line AA ′ of the piezoelectric vibration unit according to this embodiment shown in FIG. In the vicinity of the fixing portion 17 including the fixing portion 17 of the piezoelectric vibrator 11 to which the first elastic body 14 and the second elastic body 15 are attached, the support portion 18 of the first casing 12 and the second casing It fixed so that it might pinch | interpose with 13 support parts 19. FIG. As described above, the piezoelectric vibrator 11 has a cantilever shape to which the fixing portion 17 is fixed, so that a large displacement is generated in the free end portion 16. The external dimensions of the piezoelectric vibration unit according to this example in which the piezoelectric vibrator 11 was housed and held in the first housing 12 and the second housing 13 were 30 mm in length, 4 mm in width, and 4 mm in thickness.

(Example 2)
FIG. 3 is a cross-sectional view of the piezoelectric vibration unit according to the embodiment. The piezoelectric vibration unit according to this example is configured by the piezoelectric vibrator 31, the first casing 32, and the second casing 33 as in the first embodiment. The piezoelectric vibrator 31 used the same piezoelectric bimorph element as in the first embodiment. Further, the first elastic body 34 and the second elastic body 35 were filled in a space 40 formed by the surface of the piezoelectric vibrator 31 and the inner wall surfaces of the first casing 32 and the second casing 33.

  As the first elastic body 34, the trade name “Polon SR-S-40P” manufactured by Inoac Corporation used in Example 1 was used. This was processed into a length of 7 mm and a width of 4 mm, and the distance 40 measured from the free end portion 36 toward the fixed portion 37 of the piezoelectric vibrator 31 was filled in the space 40 while avoiding the range of 5 mm. For the second elastic body 35, the trade name “Polon MS-40P” manufactured by Inoac Co., used in Example 1 was used. This was processed into a length of 7 mm and a width of 4 mm, and the space 40 adjacent to the first elastic body 34 and close to the fixing portion 37 was filled.

  In the present embodiment, the vicinity of the fixing portion 37 including the fixing portion 37 of the piezoelectric vibrator 31 is fixed so as to be sandwiched between the supporting portion 38 of the first casing 32 and the supporting portion 39 of the second casing 33. The first elastic body 34 and the second elastic body 35 were filled in a space 40 formed by the inner wall surfaces of the first casing 32 and the second casing 33 and the piezoelectric vibrator 31. As described above, the piezoelectric vibrator 31 has a cantilever shape to which the fixing portion 37 is fixed, so that a large displacement is generated in the free end portion 36. The external dimensions of the piezoelectric vibration unit according to this example in which the piezoelectric vibrator 31 is housed and held in the first case 32 and the second case 33 are 30 mm in length, 4 mm in width, and thickness as in the first example. It was 4 mm.

(Example 3)
4A and 4B are diagrams showing a piezoelectric speaker according to the embodiment, in which FIG. 4A is a front view and FIG. 4B is a cross-sectional view. FIG. 4B illustrates a cross section taken along line BB ′ indicated by a broken line in FIG. In the present embodiment, the piezoelectric vibration unit 43 obtained in the second embodiment is disposed on the back surface of the vibration plate 42 disposed on the surface of the housing 41. The casing 41 is a box whose outer dimensions are 120 mm in length 44, 60 mm in width 45, and 15 mm in thickness 46 shown in FIG.

  The diaphragm 42 uses a transparent acrylic plate having a thickness of 0.5 mm, and has outer dimensions of a length 47 shown in FIG. 4A of 75 mm and a width 48 of 50 mm. A portion 49 was provided, and the diaphragm 42 was fitted into the opening 49. In the piezoelectric speaker according to the present embodiment, mechanical acoustic vibration is generated in the piezoelectric vibration unit 43 by inputting an electroacoustic signal to the piezoelectric vibration unit 43, and the vibration is transmitted to the vibration plate 42. Acoustic vibrations are radiated from the surface of the speaker and function as a speaker.

  Here, a comparative example for comparison with this example was produced. 5 and 6 are exploded perspective views of a piezoelectric vibration unit according to a comparative example. The piezoelectric vibration unit according to the comparative example shown in FIG. 5 has a structure in which the first elastic body 34 and the second elastic body 35 are removed from the piezoelectric vibration unit according to the second embodiment. That is, Comparative Example 1 is a piezoelectric vibration unit including only the piezoelectric vibrator 31, the first housing 32, and the second housing 33.

  Further, the piezoelectric vibration unit according to the comparative example shown in FIG. 6 has a structure in which the second elastic body 35 is removed from the piezoelectric vibration unit according to the second embodiment, and this is referred to as a comparative example 2. That is, in Comparative Example 2, the piezoelectric vibrator 31, the first housing 32, the second housing 33, the inner wall surfaces of the first housing 32 and the second housing 33, and the surface of the piezoelectric vibrator 31 are This is a piezoelectric vibration unit in which the space 40 formed is filled only with the first elastic body 34. The piezoelectric vibration units according to Comparative Example 1 and Comparative Example 2 were arranged on the back surface of the diaphragm 42 of the casing 41 shown in FIG.

  A drop test was carried out using the piezoelectric vibration unit according to this example and Comparative Examples 1 and 2 as samples. The drop test was performed by a method in which the sample was naturally dropped from a height of 1.8 m toward the concrete floor. Moreover, since the sample is a hexahedron, it is dropped so that each surface faces the floor surface, a drop test is performed three times on each surface, and a total of 18 drops are performed on one sample. The test was continued. The evaluation was performed by preparing five samples and performing the drop test on a total of 15 samples, and evaluating whether or not the capacitance value of the piezoelectric bimorph element used in the piezoelectric vibration unit in each sample changed. Then, the case where there was no change was regarded as acceptable, and the case where the change was confirmed was regarded as unacceptable. Table 1 shows the evaluation results of this drop test.

  As can be seen from the evaluation results of the drop test in Table 1, the piezoelectric speaker using the piezoelectric vibration unit according to this example has a significantly improved impact resistance without being damaged by a drop impact. I was able to confirm. It was also confirmed that the impact resistance was further improved by providing two types of elastic bodies rather than only one type of elastic body.

  FIG. 7 is a graph showing the generated force of the piezoelectric vibration unit according to the example. In the graph shown in FIG. 7, the horizontal axis represents frequency (Hz) and the vertical axis represents generated force (1N is assumed to be 0 dB). The generated force is obtained when the piezoelectric vibration unit according to the second embodiment is fixed to the force pickup with a double-sided tape, and a sine wave electroacoustic signal having a frequency of 100 Hz to 10 kHz is input by an audio analyzer manufactured by B & K. This shows the generated force generated by the piezoelectric vibration unit. For comparison, the generated force of the piezoelectric vibration unit according to Comparative Example 1 is also shown in the graph.

  As can be seen from the graph shown in FIG. 7, the generated force of the piezoelectric vibration unit according to Example 2 is particularly greater than that of Comparative Example 1 when the frequency is around 3 kHz to around 6 kHz. Further, in the piezoelectric vibration unit according to Comparative Example 1, the phenomenon in which the generated force suddenly increases or decreases with respect to the frequency seen in the vicinity of 2.5 kHz or near 7 kHz is the generated force in the piezoelectric vibration unit according to Example 2. It can be seen that the steepness of the change is eased. This indicates that the mechanical Q of the piezoelectric vibration unit is lowered, and a rapid change in sound pressure is suppressed in the acoustic characteristics, and the result is a piezoelectric vibration unit with good sound quality.

  In the first to third embodiments, a rectangular piezoelectric laminated piezoelectric ceramic plate is used for the piezoelectric vibrator. However, the shape and structure of the piezoelectric ceramic plate are designed as appropriate, A piezoelectric ceramic plate may be used, or in the case of a laminated piezoelectric ceramic plate, the number of laminated layers and the thickness per layer may be appropriately designed. Further, the elastic body is not limited to the specifications used in the first to third embodiments, and may be appropriately selected in consideration of acoustic performance, impact resistance, and the like.

  As described above, according to the present invention, it is possible to provide a piezoelectric vibration unit and a piezoelectric speaker that have high impact resistance, high sound pressure, good frequency characteristics, sound quality, and can be miniaturized. Become.

  The piezoelectric vibration unit and the piezoelectric speaker according to the present invention can be used as a speaker for applying vibration to a panel or a casing, and can be used as a sound generator for a mobile phone or other portable devices. It can also be used as a bone conduction speaker.

The disassembled perspective view of the piezoelectric vibration unit by an Example. Sectional drawing of the piezoelectric vibration unit by an Example. Sectional drawing of the piezoelectric vibration unit by an Example. The figure which shows the piezoelectric speaker by an Example. FIG. 4A is a front view. FIG. 4B is a cross-sectional view. The disassembled perspective view of the piezoelectric vibration unit by a comparative example. The disassembled perspective view of the piezoelectric vibration unit by a comparative example. The graph which shows the generated force of the piezoelectric vibration unit by an Example.

Explanation of symbols

11, 31 Piezoelectric vibrators 12, 32 First housing 13, 33 Second housing 14, 34 First elastic body 15, 35 Second elastic body 16, 36 Free end portion 17, 37 Fixed portion 18 , 19, 38, 39 Support section 40 Space 41 Housing 42 Diaphragm 43 Piezoelectric vibration unit 44, 47 Length 45, 48 Width 46 Thickness 49 Opening

Claims (7)

  A piezoelectric vibration unit comprising a piezoelectric vibrator and a housing for storing and holding the piezoelectric vibrator, wherein the piezoelectric vibrator has two or more elastic bodies having different hardness on the surface. Piezoelectric vibration unit.   A piezoelectric vibration unit comprising a piezoelectric vibrator and a housing for storing and holding the piezoelectric vibrator, wherein two or more elasticity having different hardnesses in a space formed by an inner wall surface of the housing and the surface of the piezoelectric vibrator A piezoelectric vibration unit characterized by being filled with a body.   3. The piezoelectric vibration according to claim 1, wherein the piezoelectric vibrator has a rectangular plate shape, and includes a fixed part to which a part is fixed and a free part that can vibrate. 4. unit.   The piezoelectric vibration unit according to claim 3, wherein the two or more elastic bodies increase in hardness as they approach the fixed portion.   The piezoelectric vibration unit according to claim 1, wherein the piezoelectric vibrator has a cantilever structure.   The piezoelectric vibration unit according to any one of claims 1 to 5, wherein the piezoelectric vibrator is formed of a piezoelectric bimorph element or a piezoelectric unimorph element.   A piezoelectric speaker comprising the piezoelectric vibration unit according to any one of claims 1 to 6 fixed to a diaphragm.

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