JP2014233063A - Piezoelectric speaker structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric speaker, having characteristics of efficient generation of a transversal wave by pressing upper and lower faces of a honeycomb diaphragm with a guide component to apply a certain flexure stress, the elimination of sound reflection and sound reverberation, and the reach of clear voice far away, and enabling mass production at low cost by the selection of a speaker configuration member.SOLUTION: A vibration proof rubber 5 is mounted on the outer peripheral part of a honeycomb diaphragm 1. Through the vibration proof rubber, the diaphragm is pressed by means of an upper guide component 2 and a lower guide component 3, having curve surface shapes, from the upper and lower faces, so that the diaphragm is bent. To the diaphragm having the added constant flexure stress, a ceramic piezoelectric element 4 is attached using a resin screen and a nut 6, to thereby provide a piezoelectric speaker generating a transversal wave. By the selection of a speaker configuration member, the characteristics of nonmagnetism and fire resistance can be given. Also, dust emission from the speaker can exceedingly be reduced.

Description

  There has been proposed a method of applying stress to improve acoustic characteristics by bending a diaphragm of a flat speaker.

  As an example, we propose a speaker that demonstrates good sound quality and frequency characteristics by pressing both ends of the diaphragm of a flat speaker through a spring or rubber, bending the diaphragm, and attaching a magnet-type vibrator to the center. Has been. (Patent Document 1)

  In addition, by applying vibration to the diaphragm in a state where stress is applied and bending stress is applied in parallel to the plate surface using a magnet-type vibrator, the longitudinal wave that is the waveform of sound from a conventional dynamic speaker A speaker that generates different transverse waves, has less interference, and has a small attenuation rate has been proposed. (Patent Document 2)

  JP 2004-120517 A   JP2007-19623   JP 2010-171927

  March 2013 “The essence of invention” Yoshiaki Muto Modern Science Co., Ltd.

  For diaphragms made of plastic, wood, etc. with low bending rigidity, the diaphragm must be bent greatly in order to obtain the bending stress value necessary to generate transverse waves, and thin speakers can be manufactured. It becomes difficult.

  On the other hand, in the method in which both ends of the vibration plate having high bending rigidity are pressed with a spring or rubber, a large pressing force is required, the structure becomes complicated, and the weight is inevitable. In addition, it is not easy to produce a product with uniform acoustic quality by applying pressure with a spring or rubber to make the bending stress value uniform.

  Furthermore, using a honeycomb diaphragm having a sandwich structure with high bending rigidity and applying pressure from the left and right sides of the diaphragm, the honeycomb core material can easily break due to buckling, or the surface layer member can break easily and uniformly. Maintaining high bending stress, and the quality and long-term durability of the diaphragm cannot be obtained.

  An object of the present invention is to generate an effective transverse wave by generating a uniform uniform bending stress inside the diaphragm by applying a uniform pressure from the upper and lower surfaces of the honeycomb diaphragm, which is lightweight and has high bending rigidity. A method for easily mass-producing and manufacturing a piezoelectric speaker is provided.

  In order to achieve the above object, according to the present invention, as described in claim 1, a vibration isolating rubber is provided on the outer peripheral portion of a diaphragm having a sandwich structure in which a honeycomb structure and surface members are joined to both main surfaces thereof. Is attached, and the upper and lower surfaces of the anti-vibration rubber are pressed by two guide parts to add a set bending amount to the entire diaphragm. As a result, a piezoelectric speaker structure with a uniform bending stress applied to the diaphragm is obtained. It is to provide.

  It is considered that a sound wave component of not only a longitudinal wave but also a transverse wave is generated from a piezoelectric speaker having a diaphragm with a bending stress applied to a lightweight and rigid honeycomb diaphragm. This sound wave has a different waveform compared to the longitudinal wave sound emitted from conventional dynamic speakers and flat speakers. Even if the sound hits an obstacle such as a wall, there is no reflection, and reverberant sound is generated even if it repeatedly hits the wall. do not do. In addition, the sound attenuation is small compared to the longitudinal wave sound emitted from a conventional dynamic speaker, and the sound reaches far.

  This transverse wave increases the amount of bending of the diaphragm and increases the bending stress, so that the strength of the transverse wave and the generation ratio with respect to the longitudinal wave increase. In the speaker structure of the present invention, the necessary bending amount, that is, the bending stress value applied to the speaker diaphragm can be automatically obtained in the speaker assembly process without the need for adjustment.

  A fracture bending load test was performed by a four-point bending test in the longitudinal direction (260 mm) of the honeycomb diaphragm. As a result, the breaking bending load was 10.5 kgf, and the center deflection at that time was 9 mm. Further, the deflection at a load of 3.5 kgf (33% of the breaking bending load) was 3 mm.

  On the other hand, in the speaker which assumed the medium-sized building structure and the railroad car which were produced in the experiment, the transverse wave effect was able to be exhibited sufficiently with the trumami of 3 mm. Further, in a normal room, the shear wave effect was obtained at 1 mm (11% of the fracture limit bending load). If the fracture limit bend amount is 50% or more, it is considered that a greater shear wave effect can be obtained. However, when used for a long period of time, there is a possibility of occurrence of buckling of the honeycomb diaphragm or destruction of the surface material. It is desirable to make it 50% or less of the breaking bending load. From these results, it was determined that the bending load for generating a transverse wave was 10% to 50% of the fracture bending load, that is, the bending stress was 10% to 50% of the maximum bending stress.

  It has become possible to produce a double-sided speaker that has large openings on both sides of the speaker housing and allows clear sound with almost the same sound pressure to reach far away from the front and back of the speaker.

  Furthermore, as a method of manufacturing a diaphragm with added bending stress, in addition to a method in which bending is mechanically generated by a guide member, the thermal contraction rate of each of the surface layer members on both main surfaces of the honeycomb structure used for the diaphragm is reduced. It is also possible to manufacture a diaphragm in which bending stress is generated due to the difference in the shrinkage rate of the material after cooling after using different materials and fixing in the heat and pressure process. As an example, a honeycomb structure using a glass epoxy prepreg (substantially thermal expansion coefficient of 40 ppm) on one surface layer member and an aluminum foil (thermal expansion coefficient 23 ppm) on the other surface layer member, after a heat processing step of 170 degrees When cooled to room temperature, warpage (1-2 mm at 260 mm) and bending stress were generated in the honeycomb structure.

  Ceramic piezoelectric vibrators, unlike magnet type vibrators, require voltage signal input for driving, but because of their high impedance, the drive current is small, and the power consumption is extremely low compared to dynamic dynamic speakers. Have. Therefore, there is little voltage drop due to wiring, and it is possible to connect to many piezoelectric speakers from one amplifier, and the wires necessary for connection can be significantly thinner than the wires used for connecting dynamic speakers. It becomes possible.

  A ceramic piezoelectric vibrator does not generate a magnetic force when driving a speaker, unlike a magnet type vibrator. Further, since the drive current is small, the generation of magnetism from the wiring portion is also minute. Therefore, it can also be used as a non-magnetic speaker in an MRI medical measurement room that dislikes magnetism.

  Flame retardant speakers can be manufactured by selecting honeycombs made of aluminum or aramid paper, glass phenolic resin surface members, ceramic piezoelectric vibrators, flame retardant resin housings, etc. as the main speaker materials. Yes, it can be used in railway vehicles that require flame resistance. ,

  Furthermore, since the piezoelectric speaker of the present invention is made of aluminum foil, glass epoxy resin, or glass phenol resin as the surface layer member, and the amplitude of the diaphragm by the piezoelectric vibrator is small, the pulsating flow of air due to the vibration of cone paper in the conventional speaker It can be used in the pharmaceutical manufacturing industry, food factories, hospital operating rooms, clean rooms, etc. that do not dispose of dust due to the passage of sound and sound.

  In the piezoelectric speaker of the present invention, the honeycomb diaphragm can be made thin and light, and in addition to using a small piezoelectric vibrator and class D amplifier, the piezoelectric vibrator consumes very little power due to its characteristics. Battery capacity can be reduced. Therefore, it is easy to carry around, and a portable speaker that can reach a long distance with a small, light and clear voice can be manufactured.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of a building structure and a railway vehicle speaker structure according to the present invention.
An anti-vibration rubber (5) with a groove is attached to the outer periphery of the honeycomb diaphragm (1), and an upper guide part (2) and a lower guide part (3) having curved shapes from the upper and lower surfaces through the anti-vibration rubber. ) To hold and fix the diaphragm. The guide component (2) is formed integrally with the speaker housing cover, and the guide component (3) is formed integrally with the speaker housing. The speaker cover is fastened to the speaker housing with bolts, whereby the curved surface of the guide component is mounted on the diaphragm. The amount of bending set according to the shape is automatically added to obtain the necessary bending stress value. This diaphragm has a structure in which one or two or four ceramic piezoelectric elements (4) are attached to the center of the diaphragm with acrylic resin tree screws and nuts (6). The anti-vibration rubber attached to the outer periphery of the diaphragm is most preferably α-gel (manufactured by Taica), but soft synthetic rubber having a rubber hardness of 50 ° or less can also be used.

  The honeycomb diaphragm (1) has a curved shape of guide parts (2) and (3) for adopting an aramid honeycomb panel to which a glass epoxy resin surface layer member having a size of 180 mm × 260 mm × thickness 4 mm is attached and bending the diaphragm. Is set so that 3 mm of warp is generated at the center of the diaphragm having a length of 260 mm.

  FIG. 2 shows a structure in which the direction of the diaphragm is reversed. The sound pressure distribution is substantially the same as the structure of FIG. 1, but the sound spread is slightly narrower in FIG. 1 and directivity occurs.

  FIG. 3 shows a structure in which the central portion of the two honeycomb diaphragms (1) is pulled and fixed with an acrylic resin screw and a nut (6) to which the piezoelectric vibrator is attached. With this structure, large openings can be provided on both sides of the speaker housing, making it possible to produce a speaker that efficiently emits sound of the same sound pressure from both sides of the speaker. FIG. 4 shows the result of measuring the sound pressure attenuation of the sound emitted from both sides of the speaker when this double-sided speaker is attached to the center of the structure assuming a vehicle structure. The sound pressure attenuation rate was small, and it was confirmed that human voice was transmitted clearly and without reflection or reverberation inside the 15 m long structure.

  8 and 9 show a comparison of distance attenuation between a dynamic speaker and a transverse wave speaker with a single sine wave having frequencies of 1000 Hz and 3150 Hz, respectively. The double-sided type shown in FIG. 3 was used as the speaker, and three 50-T types with large driving force were attached to the piezoelectric vibrator.

  5 and 6 show speaker structures used for indoor ceiling speakers. FIG. 5 shows a structure in which a bending stress is applied by pulling a honeycomb diaphragm from a speaker housing through a piezoelectric element with a screw. In FIG. 6, glass epoxy prepreg and aluminum foil are used as the surface layer member of the honeycomb diaphragm, and after being fixed in the heat pressing process, warpage and bending stress are generated due to the difference in thermal shrinkage rate of each material during cooling. A speaker using a honeycomb diaphragm.

  FIG. 7 shows the result of measuring the directivity of sound when the speaker of FIG. 5 is installed indoors. As a result, it was confirmed that the sound of the speaker according to the present invention showed omnidirectionality peculiar to the transverse wave and was widely transmitted throughout the room.

  In order to judge whether the audio content is clear and easy to hear for human hearing, we set indicators such as sound intensity, sound tremor, clarity, and sound change, and compared with conventional speakers The table is shown in Table 1. This table shows that the sound of the shear wave speaker is easy to hear for human hearing.

  Table 2 shows a comparison of characteristics between a conventional dynamic speaker and a shear wave speaker.

FIG. 10 shows an electrical wiring diagram when a large number of speakers of the present invention are installed.
Since this speaker drives a ceramic piezoelectric vibrator by voltage, only a very small current of several millimeters to several tens of amperes flows compared to a conventional dynamic speaker due to the high impedance characteristics of the piezoelectric element. Therefore, it was confirmed that even if a large number of speakers were connected in parallel, the voltage effect was small and a large number of speakers could be driven from a single amplifier with a constant sound pressure and low power consumption.

  In the speaker of the present invention, the honeycomb structure is made of aramid paper, the surface layer member is made of aluminum foil or a phenol resin sheet, and the speaker housing is made of a phenol-based flame retardant resin, so that a flame retardant speaker can be easily manufactured. I can do it.

  The ceiling speaker shown in FIG. 5 has a surface layer member made of aluminum foil or glass cloth epoxy resin, and the amplitude of the diaphragm is small. Therefore, air pulsation and sound due to the vibration of cone paper are applied to the surface cloth of the speaker and the speaker itself. It has a feature that does not cause the problem that the speaker gets dirty due to the passage of.

  As the honeycomb core structure of the honeycomb diaphragm used in the present invention, a paper honeycomb impregnated with a phenol resin, an aluminum honeycomb, an aramid honeycomb, or the like can be used. A honeycomb made of aramid or an aramid is preferable.

  The thickness of the honeycomb diaphragm is preferably 4 mm to 8 mm. If the thickness is less than 4 mm, it is difficult to ensure strength and rigidity, and if it exceeds 8 mm, it is difficult to bend the diaphragm and the weight increases, so a ceramic piezoelectric vibrator with a large driving force is selected. There is a need to.

  The piezoelectric vibrator (4) used in the present invention is a ceramic piezoelectric vibrator having a bimorph structure in which piezoceramics (PZT) are attached to both surfaces of a metal diaphragm to efficiently generate vibration. Attach one to the center and two to four on the speaker diaphragm. The transducer connections are connected in parallel. In addition, by using multiple piezoelectric vibrators on the same axis or using a piezoelectric element with a laminated structure of several to several tens of layers, a piezoelectric speaker with large amplitude, increased driving force, and large sound can be produced. Is possible.

The material used in the present invention is ceramic piezoelectric vibrator: PZT Laboratory 50-T, W50-W bimorph type piezoelectric element paper honeycomb: Shin Nihon Feathercore Co., Ltd. Phenol impregnated paper honeycomb aramid honeycomb: Showa Aircraft Industry ( Co., Ltd. Class A power amplifier for driving aramid honeycomb core piezoelectric speaker: New Japan Radio Co., Ltd. NJW126X Series Class D amplifier board: Unitech Co., Ltd. Class D piezoelectric speaker circuit board

  Piezoelectric speaker with a diaphragm bent by a guide member   Piezoelectric speaker with a structure in which the diaphragm is bent to the opposite side of FIG.   Piezoelectric speaker with a structure that generates uniform sound from both sides   Sound pressure attenuation of a piezoelectric speaker installed in a vehicle structure   Lightweight structure piezoelectric speaker for ceiling   Piezoelectric speakers composed of surface layer members with different thermal shrinkage rates   Omnidirectional characteristics of ceiling speakers   Comparison of speaker sound pressure distance attenuation at 1000Hz single tone   Comparison of speaker sound pressure distance attenuation with 3150Hz single sound   Installation diagram of many piezoelectric speakers

Table 1

  Auditory comparison between the present speaker and the conventional speaker

Table 2

  Comparison of the characteristics of the present speaker and the conventional speaker

DESCRIPTION OF SYMBOLS 1 Honeycomb diaphragm 2 Upper guide part which presses a diaphragm 3 Lower guide part which presses a diaphragm 4 Ceramic piezoelectric vibrator 5 Anti-vibration rubber 6 Resin screw and nut 7 Ceiling structural material 8 Double-sided speaker housing

On the other hand, in the speaker which assumed the medium-sized building structure and the railroad car which were produced in the experiment, the transverse wave effect was able to be exhibited sufficiently with the trumami of 3 mm. Further, in a normal room, the shear wave effect was obtained at 1 mm (11% of the fracture limit bending load). If the fracture limit bend amount is 50% or more, it is considered that a greater shear wave effect can be obtained. However, when used for a long period of time, there is a possibility of occurrence of buckling of the honeycomb diaphragm or destruction of the surface material. It is desirable to make it 50% or less of the breaking bending load. From these results, it was determined that the bending load for generating a transverse wave was 10% to 50% of the breaking bending load , that is, the bending stress was 10% to 50% of the breaking bending load .

FIG. 1 shows an example of a building structure and a railway vehicle speaker structure according to the present invention.
An anti-vibration rubber (5) with a groove is attached to the outer periphery of the honeycomb diaphragm (1), and an upper guide part (2) and a lower guide part (3) having curved shapes from the upper and lower surfaces through the anti-vibration rubber. ) To hold and fix the diaphragm. The guide component (2) is formed integrally with the speaker housing cover, and the guide component (3) is formed integrally with the speaker housing. The speaker cover is fastened to the speaker housing with bolts, whereby the curved surface of the guide component is mounted on the diaphragm. The amount of bending set according to the shape is automatically added to obtain the necessary bending stress value. This diaphragm has a structure in which one or two or four ceramic piezoelectric elements (4) are attached to the center of the diaphragm with acrylic resin tree screws and nuts (6). The vibration-proof rubber to be attached to the outer periphery of the diaphragm is most preferably a gel-like silicon material, but a soft synthetic rubber having a rubber hardness of 50 ° or less can also be used.

Claims (8)

  By attaching anti-vibration rubber to the outer periphery of a flat diaphragm having a sandwich structure in which the surface layer members are joined to the honeycomb core structure and its two main surfaces, and pressing the upper and lower surfaces of the anti-vibration rubber with guide parts A piezoelectric speaker with a ceramic piezoelectric vibrator attached to a diaphragm with bending stress.   The outer peripheral part of the two honeycomb diaphragms is fixed with vibration-proof rubber while maintaining a constant interval, and the central part of the two honeycomb diaphragms is pulled by a screw and a nut to the diaphragm to which bending stress is applied. A piezoelectric speaker with a ceramic piezoelectric vibrator.   3. The piezoelectric speaker according to claim 1, wherein open portions are provided on both sides of the piezoelectric speaker housing to which the honeycomb diaphragm is attached, and the structure is configured to emit sound having the same sound pressure from both sides of the speaker housing.   Honeycomb in which a material having different thermal shrinkage rates is used for the surface layer members on both main surfaces of the honeycomb core structure, and after being fixed in the thermal pressurization process, bending stress is applied due to the difference in thermal shrinkage rates of the surface layer members during cooling. A piezoelectric speaker with a ceramic piezoelectric element attached to the diaphragm.   5. The piezoelectric speaker according to claim 1, wherein the ceramic piezoelectric vibrator is fixed to the honeycomb diaphragm with a resin screw and nut or a resin stud and nut.   The honeycomb diaphragm, the ceramic piezoelectric vibrator, the vibration-proof rubber, the speaker housing, etc. are made of a material having a low dust generation property, and the generation of particles by driving the speaker is extremely small. Piezoelectric speaker.   A non-magnetic piezoelectric speaker comprising the above 1 to 5, wherein the honeycomb diaphragm, the ceramic piezoelectric vibrator, the vibration-proof rubber, and the speaker housing are made of a non-magnetic material and do not generate magnetism during driving.   The portable piezoelectric speaker according to claim 1, wherein a honeycomb diaphragm, a piezoelectric vibrator, an anti-vibration rubber, a speaker housing, and the like are made of a small and lightweight member to facilitate carrying and carrying.

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