TW201347564A - Composite piezoelectric vibrator and piezoelectric speaker using the same - Google Patents

Abstract

A composite piezoelectric vibrator includes a polymer film composed of fiber, lightweight foam and pressure sensitive adhesive that are combined together by an adhesive and a piezoelectric actuator adhered to surface of the polymer film or embedded in the polymer film. The low-stiffness, low-gravity polymer film optimizes the mechanical properties and in turn the frequency characteristic of the composite piezoelectric vibrator so as to improve the bandwidth and low-frequency performance of the composite piezoelectric vibrator. A piezoelectric speaker made by mounting and fixing the composite piezoelectric vibrator on a frame through a flexible support is also advantaged by the improved low-frequency performance and bandwidth.

Description

Composite piezoelectric vibration plate and piezoelectric horn having composite piezoelectric vibration plate

The present invention relates to piezoelectric vibration sounding technology. More specifically, the present invention provides a composite piezoelectric vibration plate formed by bonding a polymer film and a piezoelectric actuator using a polymer film containing a fiber, a lightweight foaming material, and a pressure sensitive adhesive material. The present invention also proposes a piezoelectric horn made of the composite piezoelectric vibration plate structure and the soft support, which has the characteristics of the low-range characteristic enhancement and the wide range.

The piezoelectric sheet has the characteristics of mechanical energy and electrical energy conversion, and the structure formed by laminating the piezoelectric sheet with the metal foil can generate bending vibration and emit sound under voltage driving. Due to the specific structural shape, mechanical resonance occurs, and the emitted sound has a maximum value, resulting in poor frequency characteristics of the sound and distortion. In general, in order to avoid the occurrence of resonance, a vibration-damping sheet capable of absorbing resonance energy is used to suppress the resonance phenomenon, thereby obtaining a relatively flat sound frequency characteristic. By adjusting the combination of the vibration-damping structure and the piezoelectric vibration structure, piezoelectric sound-emitting elements having different frequency characteristics can be produced. How to match for maximum sound output (or electromechanical conversion efficiency) and flat sound frequency response, the focus of design for good piezoelectric sound components.

The piezoelectric vibration structure utilizes the mechanical energy and electrical energy conversion characteristics of the piezoelectric material to cause the piezoelectric sheet to be deformed by the AC voltage, and the deformation of the piezoelectric sheet is used to drive the metal foil which is closely coupled with the piezoelectric sheet to generate sound. Output. Piezoelectric deformation is transmitted through a highly rigid metal foil, which drives the air to generate sound. Therefore, the harder the structure of the piezoelectric vibrating piece (or the higher the rigidity), the higher the electromechanical conversion efficiency. In order to avoid the disadvantage of poor frequency response due to structural resonance, a structure or material having a low mechanical quality factor can be used, which is generally a low-rigidity material and structure having a vibration-damping effect, which is contrary to the piezoelectric vibrating piece. Therefore, it is combined with different structures or materials to combine high-voltage electric vibration and vibration-making effects, and has a patented direction for piezoelectric sounding elements.

The foamed material has a vibration-damping effect and can be applied to a piezoelectric vibrating plate to obtain a stable sound pressure. For example, Japanese Patent No. JP4082400, JP3175744, JP 2128599, JP 4157900, JP 4140999, etc. The vibrating plate, and Japanese Patent JP 63016799 uses a foamed plate as a fixed buffer for the piezoelectric vibrating plate. Although a relatively stable sound pressure can be obtained, the sound pressure value is reduced by the vibration-damping effect of the foamed material. The viscous fluid is used to provide vibration damping when the piezoelectric vibrating plate is operated. For example, Japanese patent JP3293898 still has a problem that the sound pressure value is greatly reduced. The use of low-rigidity organic materials is a common vibration-damping structural component. In order to avoid the loss of rigidity and the loss of the deformation of the piezoelectric sheet during operation, the electromechanical conversion efficiency is lowered, and the method of intercalating organic materials with high rigidity of the metal foil is often used. Piezoelectric vibrating reeds are exemplified by the Japanese patents JP9135496, JP3143198, JP2214300 and JP2006287968, and U.S. Patent No. 5,805,726.

Fixing the piezoelectric vibrating piece on the support structure or frame, or using a less rigid material or structure to reduce the resonance phenomenon of the piezoelectric vibrating piece, such as the Japanese patent JP2005064831, JP11331976, JP9271096, JP 60165200, etc. The polymer film or the foam material of the effect connects the piezoelectric vibrating piece and the support frame, so that the entire structure has a good audio response. A double-sided tape with a pressure-sensitive adhesive material is used as a support for fixing. For example, Japanese Patent No. JP6343199, KR20070109980 and JP 60242799, and US Pat. No. 6,205,226, etc., directly bond a double-sided tape to a piezoelectric vibration plate on a frame, which is simple to manufacture and more The characteristics of the pressure sensitive adhesive material can be utilized to adjust the tensile stress generated by the frame on the piezoelectric vibration plate, thereby reducing the problem of audio distortion. The use of a metal foil having a shape different from that of the piezoelectric sheet is a piezoelectric vibrating piece structure, and a wider audio response can be obtained without lowering the electromechanical conversion efficiency, and a cushioning vibration-damping support structure can be used to obtain a better audio response. Patents such as US6865785, JP2001285994, JP2001016692, EP0999723, US6453050, US6064746, US 5825902, and the like.

In the previous case, the piezoelectric vibrating piece and the vibration-damping structure were designed differently in material and shape, and the two structures were connected into a single piezoelectric sound-emitting element through a bonding method. However, such a multi-bond design complicates the fabrication of the structure, which is not conducive to mass production.

Piezoelectric vibrating piece is limited by high rigidity, which makes its low-frequency response worse. In order to improve the low-frequency response, it is often necessary to reduce the thickness or increase the area of the piezoelectric vibrating piece, which causes the mechanical strength of the piezoelectric vibrating piece to be lowered, and the piezoelectric vibration is caused. The sheet is damaged during processing. The mechanism layer is sandwiched between the metal foils. Since the two layers of metal foil are used and the bonded metal foil and the vibration-damping sheet are used, the thickness of the overall piezoelectric vibrating piece cannot be reduced, and the improvement of the low-frequency characteristics is rather limited. It is based on how to manufacture a piezoelectric vibrating piece with a thin structure and high mechanical strength, which is an important basis for designing a wide-frequency piezoelectric acoustic element with improved bass characteristics.

In view of the above-mentioned deficiencies of the prior art, the main object of the present invention is to provide a composite piezoelectric vibration plate which utilizes a low rigidity and low specific gravity polymer film to change the mechanical properties of the vibration plate to adjust the frequency of the vibration plate. Features, wideband and low-range effects.

Another object of the present invention is to provide a piezoelectric horn having a composite piezoelectric vibration plate which has characteristics of enhancement of a low-range characteristic and a wide range.

In order to achieve the above object, according to one embodiment of the present invention, a composite piezoelectric vibration plate comprises: a polymer film composed of a foamed material, a fiber, a pressure sensitive adhesive material, and a binder; and a piezoelectric The actuator is composed of a metal foil and a piezoelectric ceramic sheet attached to one or both sides of the metal foil. The piezoelectric actuator is embedded in the polymer film or attached to the surface of the polymer film.

According to another embodiment of the present invention, a composite piezoelectric vibration plate includes: a polymer film composed of a foamed material, a fiber, a pressure sensitive adhesive material, and a binder; and a piezoelectric actuator, It is composed of a metal foil and a piezoelectric ceramic sheet attached to one or both sides of the metal foil; and a frame for fixing the composite piezoelectric vibration plate. The frame is provided with a soft support structure for positioning the composite piezoelectric vibration plate to the frame.

For the convenience of the description, the central idea expressed by the present invention in the column of the above summary of the invention is expressed by the specific embodiments. Various items in the embodiments are depicted in terms of ratios, dimensions, amounts of deformation, or displacements that are suitable for illustration, and are not drawn to the proportions of actual elements, as set forth above. In the following description, like elements are denoted by the same reference numerals.

The audio characteristics of the diaphragm are related to the quality of the diaphragm. Reducing the quality of the diaphragm contributes to the sound generation in the low range, and the resulting sound pressure is also high. The lightweight material is represented by foaming, and the specific gravity of the material is reduced by the introduction of voids. The mechanical strength of the foamed material is weak, and there is a problem of cracking under the use condition of high sound pressure. The fiber-reinforced polymer film is an effective method for improving the mechanical strength, and a foaming material is added under sufficient mechanical strength to form a polymer film having both light weight and mechanical strength, which is the principle of realizing a wide-range horn diaphragm.

Referring to the first figure, there is shown a cross-sectional view of a composite piezoelectric vibration plate 100 including a piezoelectric actuator according to an embodiment of the present invention. The composite piezoelectric vibration plate 100 of the present invention is constructed by embedding a bimodal piezoelectric actuator 120 in a polymer film 110 composed of a foamed material 111, a fiber 113, a pressure sensitive adhesive material 115, and a binder. . Preferably, the polymer film 110 has a specific gravity of 0.5 to 1.5, and the foamed material is a polymer material having a specific gravity of 0.01 to 0.1. The fiber is a staple fiber having a length of 5 to 30 mm and the pressure sensitive adhesive material is softened. Polymer material with a temperature of 20 to 50 °C. The piezoelectric actuator 120 includes a metal foil 121, and generates bending vibration by the piezoelectric sheet 123. In the polymer film 110, the foamed material 111 and the fiber 113 are bonded by using a binder, and the piezoelectric actuator 120 described above is embedded in a slurry form and dried to form a composite piezoelectric vibration plate 100. Wherein, the bonding agent may be polyvinyl alcohol, methyl cellulose, ethylene-vinyl acetate copolymer or acrylate, and the metal foil 121 The material can be copper, copper alloy, iron-nickel alloy or stainless steel.

In another embodiment of the present invention, the polymer film 110 may be formed into a film by a doctor blade or an extrusion molding process, and then the piezoelectric actuator 120 is attached to the surface of the polymer film 110. The composite piezoelectric vibration plate 100' shown in the second figure. In this embodiment, the anaerobic resin is used as the adhesive 130, and the piezoelectric actuator 120 is fixed to the surface of the polymer film 110.

Then, the composite piezoelectric vibration plate 100 or 100' is fixed to a frame 300 through a flexible supporting structure 200, such as a silicone or silicone rubber adhesive, to form a planar piezoelectric device as shown in the third figure. horn.

The fourth figure shows the audio response characteristics of a piezoelectric horn made of a composite piezoelectric diaphragm. The composite piezoelectric vibration plate is a bimodal piezoelectric actuator using a piezoelectric sheet having a size of 30 ^φ x 0.05 mm ^t , and the metal piece of the piezoelectric actuator is a 15 μm thick copper piece, which is embedded in the polymer. A composite piezoelectric vibration plate having a size of 52 x 45 x 0.6 mm ³ is formed in the film. The composite piezoelectric vibration plate is then fixed to the frame to form a planar piezoelectric horn shown in the third figure. The piezoelectric speaker has a starting frequency as low as 220 Hz and a maximum sound pressure of 112 dB (15 V driving voltage). It has a high sound pressure from 200 Hz to 20 kHz, which is in line with the wide range.

Referring to the first and second figures, in order to reduce the fluctuation of the sound pressure in the audio response, the present invention is characterized in that a pressure sensitive adhesive material 115 is added to the polymer film 110. By utilizing the pressure modulation viscosity of the pressure sensitive adhesive material 115, a large damping effect is obtained for the frequency of the high sound pressure. Preferably, the pressure sensitive adhesive material 115 is a polymer material having a softening temperature of 20 ° C to 50 ° C. The fifth picture shows the piezoelectric speaker's audio response with 20 wt% pressure sensitive adhesive material. The maximum sound pressure is reduced from 112 dB to 100 dB, and the sound pressure fluctuation is reduced from the original 25 dB to 14 dB, which significantly improves the speaker's audio. response.

The sixth figure compares the effect of adding pressure sensitive adhesive material on the audio response of the piezoelectric speaker under the driving of 15 V voltage. Since the pressure sensitive adhesive increases the specific gravity of the polymer film, the starting frequency is increased, only on the sound pressure fluctuation. The addition of pressure sensitive adhesive does achieve the effect of suppressing high sound pressure, which greatly reduces the fluctuation of the sound pressure in the overall audio response. The results of the sixth figure show that the addition of the pressure sensitive adhesive material improves the audio characteristics of the polymer diaphragm, and is more suitable for a wide-range speaker product.

The effect of different pressure-sensitive adhesive content on the audio response is shown in the seventh figure, in which the same fiber, foaming material and adhesive component polymer film are used, respectively, adding 5 to 20 wt% of pressure sensitive adhesive material, due to the sense The addition of the pressure-sensitive adhesive increases the composition of the viscous material and increases the effect of the vibration suppression, resulting in a decrease in the maximum sound pressure value and a decrease in the sound pressure fluctuation. Adding 20 wt% pressure sensitive adhesive material, the maximum sound pressure can still maintain more than 90 dB, and the sound pressure fluctuation is reduced to 14 dB.

Due to the high specific gravity of the pressure sensitive adhesive material, the more polymer film is added, the specific gravity is also increased, and the starting frequency (Fo) after the horn is formed is also increased. Similarly, changing the content of the foaming material will also adjust the specific gravity of the polymer film, and the starting frequency of the horn will also increase. As shown in the eighth figure, the content of the foaming material is lowered, and the polymer is equivalently improved. The specific gravity of the membrane and the starting frequency also increase, and the low specific gravity is an important basis for generating the audio response of the low range.

The foamed material is used to make a light-weight polymer film, and the produced diaphragm has the effect of reducing the frequency of the oscillation, improving the audio response of the low range, and is advantageous for the application of the wide-range speaker. In order to improve the mechanical strength of the polymer film and avoid cracking caused by excessive sound pressure, the fiber strength is used to improve the mechanical strength of the polymer film. By using a pressure sensitive adhesive material having a high attenuation rate for high sound pressure, the polymer film has a problem that the sound pressure fluctuation caused by excessive sound pressure is excessively suppressed. A polymer film made of a foamed material, a fiber, a pressure sensitive adhesive material and a binder is used to design a piezoelectric actuator embedded or surface-attached to form a composite piezoelectric diaphragm, and the composite piezoelectric diaphragm is The soft support is fixed on the frame and becomes a wide-range flat speaker. It has a simple structure and good audio characteristics, and becomes a new practical wide-range planar speaker.

While the invention has been described in terms of the preferred embodiments, the embodiments of the invention The above embodiments are merely illustrative of the invention and are not intended to limit the scope of the invention. Any modifications or variations that are made without departing from the spirit of the invention are intended to be protected.

100. . . Composite piezoelectric diaphragm

100’. . . Composite piezoelectric diaphragm

110. . . Polymer film

111. . . foaming material

113. . . fiber

115. . . Pressure sensitive adhesive material

120. . . Piezoelectric actuator

121. . . foil

123. . . Piezoelectric sheet

130. . . Adhesive

200. . . Soft support structure

300. . . frame

The first figure is a schematic structural view of a composite piezoelectric vibration plate according to an embodiment of the present invention, in which a piezoelectric actuator is embedded in a polymer film.

The second figure is a schematic structural view of a composite piezoelectric vibration plate according to another embodiment of the present invention, wherein a piezoelectric actuator is attached to a polymer film.

The third figure is a schematic diagram of a piezoelectric horn fabricated by a composite piezoelectric diaphragm structure.

The fourth picture shows the audio response characteristics of the piezoelectric horn.

The fifth figure shows the audio response of the piezoelectric horn produced by the composite piezoelectric vibration plate structure with the pressure sensitive adhesive material added.

The sixth picture shows the effect of adding pressure sensitive adhesive material on the audio response of the piezoelectric speaker.

The seventh picture shows the effect of the pressure-sensitive adhesive material content on the audio response of the piezoelectric speaker.

The eighth figure shows the effect of the specific gravity of the polymer film on the starting frequency of the piezoelectric horn.

100. . . Composite piezoelectric diaphragm

120. . . Piezoelectric actuator

200. . . Soft support structure

300. . . frame

Claims (10)

A composite piezoelectric vibration plate comprising: a polymer film composed of a foamed material, a fiber, a pressure sensitive adhesive material and a binder; and a piezoelectric actuator which is made of a metal foil and a sticker It is composed of a piezoelectric ceramic sheet which is bonded to one side or both sides of the metal foil. The composite piezoelectric vibration plate according to claim 1, wherein the piezoelectric actuator is embedded in the polymer film or attached to the surface of the polymer film. The composite piezoelectric vibration plate according to claim 1, wherein the polymer film has a specific gravity of 0.5 to 1.5. The composite piezoelectric vibration plate according to claim 1, wherein the pressure sensitive adhesive material is a polymer material having a softening temperature of 20 ° C to 50 ° C. A piezoelectric horn having a composite piezoelectric vibration plate, comprising: a composite piezoelectric vibration plate, comprising: a polymer film composed of a foaming material, a fiber, a pressure sensitive adhesive material and a binder; and a A piezoelectric actuator comprising a metal foil and a piezoelectric ceramic sheet attached to one or both sides of the metal foil; and a frame for fixing the composite piezoelectric vibration plate. A piezoelectric horn having a composite piezoelectric vibration plate according to claim 5, wherein the frame is provided with a soft support structure for positioning the composite piezoelectric vibration plate to the frame. The piezoelectric horn having a composite piezoelectric vibration plate according to claim 6, wherein the soft support structure is made of silicone rubber or tantalum rubber. The piezoelectric horn having a composite piezoelectric vibration plate according to claim 5, wherein the piezoelectric actuator is embedded in the polymer film or attached to the surface of the polymer film. A piezoelectric horn having a composite piezoelectric vibration plate according to claim 5, wherein the polymer film has a specific gravity of 0.5 to 1.5. The piezoelectric horn having a composite piezoelectric vibration plate according to claim 5, wherein the pressure sensitive adhesive material is a polymer material having a softening temperature of 20 ° C to 50 ° C.