WO2007136162A1 - Piezoelectric vibrator for regenerating sound, and piezoelectric panel speaker and piezoelectric earphone having the same - Google Patents

Piezoelectric vibrator for regenerating sound, and piezoelectric panel speaker and piezoelectric earphone having the same Download PDF

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Publication number
WO2007136162A1
WO2007136162A1 PCT/KR2006/005816 KR2006005816W WO2007136162A1 WO 2007136162 A1 WO2007136162 A1 WO 2007136162A1 KR 2006005816 W KR2006005816 W KR 2006005816W WO 2007136162 A1 WO2007136162 A1 WO 2007136162A1
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WO
WIPO (PCT)
Prior art keywords
piezoelectric
piezoelectric vibrator
sound
lead
vibrator
Prior art date
Application number
PCT/KR2006/005816
Other languages
French (fr)
Inventor
Sang-Goo Lee
Original Assignee
Ibule Photonics Co., Ltd.
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Publication date
Application filed by Ibule Photonics Co., Ltd. filed Critical Ibule Photonics Co., Ltd.
Publication of WO2007136162A1 publication Critical patent/WO2007136162A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R7/00—Diaphragms for electromechanical transducers; Cones
    • H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
    • H04R7/04—Plane diaphragms
    • H04R7/06—Plane diaphragms comprising a plurality of sections or layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B06B1/0603—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a piezoelectric bender, e.g. bimorph
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K9/00—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers
    • G10K9/12—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers electrically operated
    • G10K9/122—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers electrically operated using piezoelectric driving means

Definitions

  • the present invention relates to a sound reproducer using a piezoelectric material,and more particularly, to a piezoelectric sound reproducer using a metal-made elastic material, particularly an effective electric material such as copper, tungsten, aluminum, or the like, equal to or less than 30 micrometers, and having high sound pressure with respect to a range from a low-pitched sound lower than 100 Hz to a high- pitched sound higher than 3 kHz reproduced by a multi-layer vibrator in which an piezoelectric actuator in which a piezoelectric material is attached to the elastic material is set to a single unit and several units of the piezoelectric materials are laminated by interposing sound absorbing material such as porous nano-particles such as nano-fiber, non- woven fabric, and carbon nano-tube or general nano-particles.
  • a metal-made elastic material particularly an effective electric material such as copper, tungsten, aluminum, or the like, equal to or less than 30 micrometers, and having high sound pressure with respect to a range from
  • a conventional piezoelectric panel speaker or a conventional piezoelectric earphone has the essential problem of a sound reproducer using piezoelectric material such that it is difficult to reproduce low-pitched sound lower than 500 Hz, sound pressure is low at a low-pitched sound region and unbalanced sound pressure is significantly generated at a high-pitched sound region.
  • Several approaches are attempted to solve this problem using plural piezoelectric vibrators, however the approaches do not achieve to reproduce satisfactory low-pitched sound or to obtain high sound pressure and are not widely used now.
  • FIGS. 1 and 2 are views illustrating a piezoelectric vibrator 100 disclosed in Korean Patent Application No. 2004-0100889 (hereinafter, referred to a 'previous invention').
  • FIG. 1 illustrates a piezoelectric vibrator 100 including a monomorphic piezoelectric actuator in which a piezoelectric material 110a is disposed at a side of an elastic material 110b and a vibration transmission elastic material 110.
  • the vibration transmission elastic material 110 includes a first portion 120a and a second portion 120b.
  • FIG. 2 illustrates a piezoelectric vibrator 100 including a bimorph piezoelectric actuator in which piezoelectric materials 110a are disposed at sides of an elastic material 110b and a vibration transmission elastic material 110.
  • FIGS. 3 to 6 illustrate a known piezoelectric vibrator 100 for a piezoelectric speaker having a structure similar to the previous invention.
  • FIGS. 3 and 5 illustrate a case using a monomorphic piezoelectric actuator 110
  • FIGS. 4 and 6 illustrate a case using a bimorph piezoelectric actuator 110.
  • the piezoelectric vibrators in FIGS. 5 and 6 include the piezoelectric materials 110a and the elastic materials 110b of a circular shape and do not include the vibration transmission elastic material 110.
  • FIGS. 3 to 6 The most general structure illustrated in FIGS. 3 to 6 is the same as that illustrated in FIG. 4 and makes vibration generated by the bimorph piezoelectric actuator 110 vibrate a vibration panel (not shown in FIG. 2) through the vibration transmission elastic material 120.
  • the piezoelectric material when used to reproduce sound there are essential problems such as a narrow low-pitched sound range, that is, it is difficult to reproduce sound lower than 200 Hz and the sound pressure is not high.
  • the present invention has been made in view of the above problems, and it is an aspect of the present invention to provide a multi-layer piezoelectric vibrator using a thin elastic material and a sound absorption material to generate uniformly high sound pressure in an overallsound range by significantly increasing ability of reproducing low-pitched sound in a sound reproducer using the piezoelectric material.
  • a piezoelectricvibrator for reproducing sound comprising piezoelectric actuators, which respectively include an elastic material and piezoelectric materials attachedto one side or both sides of the elastic material to convert an electric signal into a mechanical vibration, are laminated to form two or more layers and a vibration adjusting sound absorption material disposed between the laminated piezoelectric actuators to increase ability of reproducing a low-pitched sound of the vibrator, to absorb a high-pitched sound, and to adjust vibration of the piezoelectric material.
  • respectively layers of the multiple layer piezoelectric material have an identical cross-sectional area and an identical shape, or neither the cross-sectional area nor the shape.
  • the elastic material is metal. Particularly, it is more effective when copper and tungsten equal to or less than 30 mircometers are used as the elastic material. Moreover, it is possible to use the elastic material having Young's modulus equal to or greater than 10 GPa.
  • a polymer nano-fiber, a carbon nano-tube, a non- woven fabric, nano- particles, and porous particles are used as the sound absorption material and the vibrators are laminated by interposing the same.
  • the piezoelectric material comprises a lead zirconium titanate (PZT) poly crystalline ceramic material or a ferroelectric single crystalline ceramic material selected from a group of a lead magnesium niobate-lead titanate (PMN-PT), a lead zinc niobate-lead titanate (PZN-PT), a lead zirconium titanate (PZT), a lead ytterbium niobate-lead titanate (PYT-PT), or lead indium noibate-lead titanate.
  • PMN-PT lead magnesium niobate-lead titanate
  • PZN-PT lead zinc niobate-lead titanate
  • PZT lead zirconium titanate
  • PYT-PT lead indium noibate-lead titanate
  • the piezoelectric material comprises a single layer or multiple layers. Moreover, respectively layers of the multiple layer piezoelectric material have an identical cross- sectional area and an identical shape, or neither the cross-sectional area nor the shape.
  • the piezoelectric material comprises a bulk type or a thin film type of the poly- crystalline material or a bulk type or a thin film type of the single crystalline material.
  • the above and other objects can be accomplished by the provision of a piezoelectric panel speaker or a piezoelectric earphone including the above-described piezoelectric vibrator.
  • two or more actuators having very thin metal-made elastic materials are laminated by interposing sound absorbing material, so that some of the high-pitched sound, an inherent property of a single piezoelectric material, is absorbed to expand the low- pitched sound range and uniformly high sound pressure can be generated over whole range of the low-pitched sound and the high-pitched sound.
  • the piezoelectric vibrator of the present invention significantly increases energy efficiency with respect to power consumption so that the reduction of the power consumption, miniaturization of products, and the reduction of signal distortion due to noise can be achieved.
  • FIGS. 1 and 2 are views illustrating configuration of a piezoelectric vibrator according to an embodiment of a previous invention
  • FIGS. 3 to 6 are views illustrating several embodiments of a conventional piezoelectric vibrator
  • FIGS. 7 to 9 are views illustrating a piezoelectric vibrator including a laminated actuator or a laminate piezoelectric buzzer according to an embodiment of the present invention
  • FIG. 10 is a view illustrating a panel speaker in which a housing is applied to the piezoelectric vibrator in FIG. 7;
  • FIG. 11 is a graph illustrating the comparison of sound range and sound pressure of the piezoelectric vibrator according to the embodiment of the present invention with a piezoelectric vibrator of the previous invention.
  • FIG. 12 is a view illustratingan earphone employing a laminated buzzer type piezoelectric vibrator according to another embodiment of the present invention. Mode for the Invention
  • FIGS. 7 to 9 illustrate an embodiment of the present invention.
  • Ap pieoelectric vibrator includes a piezoelectric actuator 110 to convert an electric signal to a mechanical vibration and another piezoelectric actuator 110 which are laminated by interposing sound absorption material to form multiple layers.
  • the piezoelectric actuator monomorphic actuator, a bimorph actuator, a conventional piezoelectric buzzer, and a multifunction vibrator disclosed in the previous patent may be employed.
  • elastic materials 110b of the respective piezoelectric actuators 110 are made by a thin plate having a thickness equal to or less than 30 micrometers.
  • Each of the piezoelectric actuators 110 includes a piezoelectric material 110a and an elastic material 110b attached to the piezoelectric material 110a.
  • An electrode is attached to the actuator 110, however is omitted from the drawings for a clear description of the features of the piezoelectric vibrator according to the embodiment of the present invention.
  • the piezoelectric vibrator according to the embodiment of the present invention includes a vibration transmission elastic material 120 attached to the piezoelectric actuator to transmit the mechanical vibration generated from the actuator 110 to the exterior.
  • the piezoelectric vibrator may include only a laminated piezoelectric actuator.
  • the piezoelectric actuator may have a rectangular shape, a disk shape, or the like, and the piezoelectric materials 110a and the elastic materials 110b may be different from or identical to in a size or a shape.
  • the configuration of the piezoelectric actuator according to the present invention is not limited to the embodiments illustrated in the drawings.
  • the piezoelectricvibrator uses a thin metal as an elastic material and at least two piezoelectric actuators laminated by interposing the sound absorbing material, the low-pitched sound range can expanded widely to the range equal to or less than 100 Hz and a high sound pressure can be obtained over whole sound range. In this case, a sound pressure increased more than 20 dB in comparison to that of the conventional piezoelectric vibrator illustrated in FIGS. 1 to 6 can be obtained.
  • FIG. 10 is a view illustratinga panel speaker in which a housing 140 is applied to the piezoelectric vibrator in FIG. 7.
  • the housing 140 is preferably made by a polymer resin to enclose the piezoelectric vibrator.
  • FIG. 11 illustrates data comparing sound pressure of the piezoelectric vibrator according to the embodiment of the present invention with that of the conventional bimorph piezoelectric vibrator.
  • FIG. 11 also illustrates the sound pressure when the housing is employed.
  • a flat board speaker employing the laminated piezoelectric vibrator and the housing can provide an enhanced sound pressure in the low-pitched sound rage equal to or less than 500 Hz.
  • a low sound pressure is generated in a low-pitched sound equal to or less than 500 Hz, and the sound pressure of the low-pitched sound only is enhanced.
  • the housing is appl ied in order to compensate this phenomenon, the sound pressure is generally decreased.
  • overall sound pressure is enhanced in comparison to the previous invention. If both the laminated structure and the housing are applied to the vibrator, the sound pressure in the low- pitched sound equal to or less than 500 Hz is more enhanced.
  • the piezoelectric vibrator 100 is mounted at a predetermined place of an edge of a vibrating panel 200. Vibration generated in the multiple layer piezoelectric actuator 110 transmitted to the vibrating panel 200 via the first portion 120a and the second portion 120b of the vibration transmission elastic material 120 to be emitted out as sound.
  • the piezoelectric vibrator 100 of the present invention including the multiple layer piezoelectric actuator 110 can provide the sound pressure much higher than that of the conventional piezoelectric vibrator due to the geometrical structural feature thereof.
  • FIG. 12 illustrates another embodiment to which the piezoelectric vibrator according to the present inventioncan be applied and a schematic view illustrating a piezoelectric buzzer earphone employing a multiple layer piezoelectric vibrator in FIG. 9.
  • Reference numerals 140, 150, 160, 170, and 200 in FIG.9 are assigned to a housing of the vibrator, a housing of the earphone, a unit cap, an air duct, and a vibrating panel, respectively.
  • the elastic materials are metal such as copper, tungsten, aluminum, or alloys thereof.
  • the elastic materials can be a material having a large Young's modulus, preferably, a polymer material having Young's modulus equal to or greater than 10 GPa, and is not limited to the kinds.
  • metal is used as the elastic material such as a metal plate equal to or less than 30 micrometers, it is more effective.
  • adhesive having a high hardness after being hardened such as epoxy is used as the laminating material using the sound absorption material and a phenomenon that a signal is decreased can be minimized.
  • the piezoelectric vibrator according to the present invention includes the vibration transmission elastic material, thicknesses, cross-sectional shapes, sizes, centers of gravity of the piezoelectric actuator 110 the elastic material 120 can be properly adjusted according to an apparatus to which the piezoelectric actuator and the elastic material are applied.
  • the piezoelectric material 110a is a poly crystalline ceramic of a lead zirconium titanate (PZT) that is widely used, or a single crystalline ceramic having a superior piezoelectric property.
  • PZT lead zirconium titanate
  • lead magnesium niobate-lead titanate (PMN-PT), lead zinc niobate-lead titanate (PZN-PT), lead zirconium titanate (PZT), lead ytterbium niobate-lead titanate (PYT-PT), or lead indium niobate-lead titanate may be used.
  • PMN-PT lead magnesium niobate-lead titanate
  • PZN-PT lead zinc niobate-lead titanate
  • PZT lead zirconium titanate
  • PYT-PT lead ytterbium niobate-lead titanate
  • lead indium niobate-lead titanate may be used.
  • the polycrystalline material or the single crystalline material of the piezoelectric material 110a may be bulk type or a film type, or may have a single layer or multiple layers.
  • a piezoelectric single crystalline material is made into a single layer, a bulk type piezoelectric single crystalline material may be grinded in the form of a thin film to be attached to an electrode or may be attached to the electrode to be grinded in the form of a thin film.
  • the piezoelectric single crystalline material is made into the thin film, the overall thickness of the piezoelectric actuator 110 may decrease.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Chemical & Material Sciences (AREA)
  • Multimedia (AREA)
  • Nanotechnology (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)
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  • Manufacturing & Machinery (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)

Abstract

Disclosed is a multiple layer piezoelectric vibrator using multiple layer piezoelectric material to significantly improve ability of reproducing low-pitched sound when sound is reproduced by a piezoelectric material and to implement high sound pressure in a broad sound range. The piezoelectric actuators including a metal-made elastic material such as copper, tungsten, and aluminum and piezoelectric materials attached to one or both sides of the elastic material are laminated by interposing a high-pitched sound absorption material such as porous nano-particles of now- woven fabric, nano-fiber, and carbon nano-tube, or nano-particles. When sound is reproduced by a multiple layer piezoelectric material, the ability of reproducing low-pitched sound can be improved. Two or more piezoelectric actuators are laminated so that sound pressure can be also improved. Moreover, cross-sections and shapes of the respective layers may be identical to or different from each other.

Description

Description PIEZOELECTRIC VIBRATOR FOR REGENERATING SOUND,
AND PIEZOELECTRIC PANEL SPEAKER AND PIEZOELECTRIC EARPHONE HAVING THE SAME
Technical Field
[1] The present invention relates to a sound reproducer using a piezoelectric material,and more particularly, to a piezoelectric sound reproducer using a metal-made elastic material, particularly an effective electric material such as copper, tungsten, aluminum, or the like, equal to or less than 30 micrometers, and having high sound pressure with respect to a range from a low-pitched sound lower than 100 Hz to a high- pitched sound higher than 3 kHz reproduced by a multi-layer vibrator in which an piezoelectric actuator in which a piezoelectric material is attached to the elastic material is set to a single unit and several units of the piezoelectric materials are laminated by interposing sound absorbing material such as porous nano-particles such as nano-fiber, non- woven fabric, and carbon nano-tube or general nano-particles. Background Art
[2] A conventional piezoelectric panel speaker or a conventional piezoelectric earphone has the essential problem of a sound reproducer using piezoelectric material such that it is difficult to reproduce low-pitched sound lower than 500 Hz, sound pressure is low at a low-pitched sound region and unbalanced sound pressure is significantly generated at a high-pitched sound region. Several approaches are attempted to solve this problem using plural piezoelectric vibrators, however the approaches do not achieve to reproduce satisfactory low-pitched sound or to obtain high sound pressure and are not widely used now.
[3] In order to increase the sound pressure, there are several proposals of using a rectangular Bimorph actuator type vibrator, disclosed in U.S. Patent No. 4,593,160, and of manufacturing an actuator by attaching ferroelectric wafer to an elastic material applied by a stress, disclosed in U.S. Patent No. 5,632,841. Although approaches to arrange several vibrators or to mount a mass to a rear side of a piezoelectric material to deform vibration, the approaches do not succeed in increasing low-pitched sound pressure of a piezoelectric speaker sufficiently.
[4] Moreover, different from other than the piezoelectric speaker, a concept about a device to increase amplitude of vibration in a bending transducer was developed in 1970's and used to be applied to an apparatus to atomize or spray liquid (See "Piezoelectric Materials in Devices", N. Setter, 2000, p. 54).
[5] FIGS. 1 and 2 are views illustrating a piezoelectric vibrator 100 disclosed in Korean Patent Application No. 2004-0100889 (hereinafter, referred to a 'previous invention'). FIG. 1 illustrates a piezoelectric vibrator 100 including a monomorphic piezoelectric actuator in which a piezoelectric material 110a is disposed at a side of an elastic material 110b and a vibration transmission elastic material 110. The vibration transmission elastic material 110 includes a first portion 120a and a second portion 120b. FIG. 2 illustrates a piezoelectric vibrator 100 including a bimorph piezoelectric actuator in which piezoelectric materials 110a are disposed at sides of an elastic material 110b and a vibration transmission elastic material 110.
[6] FIGS. 3 to 6 illustrate a known piezoelectric vibrator 100 for a piezoelectric speaker having a structure similar to the previous invention. FIGS. 3 and 5 illustrate a case using a monomorphic piezoelectric actuator 110, and FIGS. 4 and 6 illustrate a case using a bimorph piezoelectric actuator 110. Particularly, the piezoelectric vibrators in FIGS. 5 and 6 include the piezoelectric materials 110a and the elastic materials 110b of a circular shape and do not include the vibration transmission elastic material 110.
[7] The most general structure illustrated in FIGS. 3 to 6 is the same as that illustrated in FIG. 4 and makes vibration generated by the bimorph piezoelectric actuator 110 vibrate a vibration panel (not shown in FIG. 2) through the vibration transmission elastic material 120. However, according to the conventional devices, when the piezoelectric material is used to reproduce sound there are essential problems such as a narrow low-pitched sound range, that is, it is difficult to reproduce sound lower than 200 Hz and the sound pressure is not high.
Disclosure of Invention
Technical Problem
[8] Therefore, the present invention has been made in view of the above problems, and it is an aspect of the present invention to provide a multi-layer piezoelectric vibrator using a thin elastic material and a sound absorption material to generate uniformly high sound pressure in an overallsound range by significantly increasing ability of reproducing low-pitched sound in a sound reproducer using the piezoelectric material. Technical Solution
[9] The above and other objects of the present invention can be achieved by the following solutions.
[10] In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a piezoelectricvibrator for reproducing sound comprising piezoelectric actuators, which respectively include an elastic material and piezoelectric materials attachedto one side or both sides of the elastic material to convert an electric signal into a mechanical vibration, are laminated to form two or more layers and a vibration adjusting sound absorption material disposed between the laminated piezoelectric actuators to increase ability of reproducing a low-pitched sound of the vibrator, to absorb a high-pitched sound, and to adjust vibration of the piezoelectric material.
[11] According to the present invention, respectively layers of the multiple layer piezoelectric material have an identical cross-sectional area and an identical shape, or neither the cross-sectional area nor the shape.
[12] According to the present invention, the elastic material is metal. Particularly, it is more effective when copper and tungsten equal to or less than 30 mircometers are used as the elastic material. Moreover, it is possible to use the elastic material having Young's modulus equal to or greater than 10 GPa.
[13] According to an embodiment of the present invention, as the sound absorption material, a polymer nano-fiber, a carbon nano-tube, a non- woven fabric, nano- particles, and porous particles are used and the vibrators are laminated by interposing the same.
[14] The piezoelectric material comprises a lead zirconium titanate (PZT) poly crystalline ceramic material or a ferroelectric single crystalline ceramic material selected from a group of a lead magnesium niobate-lead titanate (PMN-PT), a lead zinc niobate-lead titanate (PZN-PT), a lead zirconium titanate (PZT), a lead ytterbium niobate-lead titanate (PYT-PT), or lead indium noibate-lead titanate.
[15] The piezoelectric material comprises a single layer or multiple layers. Moreover, respectively layers of the multiple layer piezoelectric material have an identical cross- sectional area and an identical shape, or neither the cross-sectional area nor the shape. The piezoelectric material comprises a bulk type or a thin film type of the poly- crystalline material or a bulk type or a thin film type of the single crystalline material.
[16] In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a piezoelectric panel speaker or a piezoelectric earphone including the above-described piezoelectric vibrator.
Advantageous Effects
[17] As described above, according to the piezoelectric vibrator of the present invention, two or more actuators having very thin metal-made elastic materials are laminated by interposing sound absorbing material, so that some of the high-pitched sound, an inherent property of a single piezoelectric material, is absorbed to expand the low- pitched sound range and uniformly high sound pressure can be generated over whole range of the low-pitched sound and the high-pitched sound.
[18] Moreover, the piezoelectric vibrator of the present invention significantly increases energy efficiency with respect to power consumption so that the reduction of the power consumption, miniaturization of products, and the reduction of signal distortion due to noise can be achieved.
[19] Furthermore, since a speaker and an earphone employing the piezoelectric vibrator of the present invention are less restricted by a vibration plate, the speaker and the earphonecan be manufactured for use in water or high humidity circumstances. Brief Description of the Drawings
[20] FIGS. 1 and 2 are views illustrating configuration of a piezoelectric vibrator according to an embodiment of a previous invention;
[21] FIGS. 3 to 6 are views illustrating several embodiments of a conventional piezoelectric vibrator;
[22] FIGS. 7 to 9 are views illustrating a piezoelectric vibrator including a laminated actuator or a laminate piezoelectric buzzer according to an embodiment of the present invention
[23] FIG. 10 is a view illustrating a panel speaker in which a housing is applied to the piezoelectric vibrator in FIG. 7;
[24] FIG. 11 is a graph illustrating the comparison of sound range and sound pressure of the piezoelectric vibrator according to the embodiment of the present invention with a piezoelectric vibrator of the previous invention; and
[25] FIG. 12 is a view illustratingan earphone employing a laminated buzzer type piezoelectric vibrator according to another embodiment of the present invention. Mode for the Invention
[26] Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[27] FIGS. 7 to 9 illustrate an embodiment of the present invention. Apiezoelectric vibrator includes a piezoelectric actuator 110 to convert an electric signal to a mechanical vibration and another piezoelectric actuator 110 which are laminated by interposing sound absorption material to form multiple layers. As the piezoelectric actuator, monomorphic actuator, a bimorph actuator, a conventional piezoelectric buzzer, and a multifunction vibrator disclosed in the previous patent may be employed.
[28] In the present invention, when polymer nano-fiber, carbon nano-tube, non-woven fabric, nano-particle, and porous particles are used as the sound absorption material to adjust the vibration of the piezoelectric material, it is possible to increase the ability of reproducing the low-pitched sound and to absorb the high-pitched sound.
[29] Moreover, according to the feature of the present invention, elastic materials 110b of the respective piezoelectric actuators 110 are made by a thin plate having a thickness equal to or less than 30 micrometers. Each of the piezoelectric actuators 110 includes a piezoelectric material 110a and an elastic material 110b attached to the piezoelectric material 110a. An electrode is attached to the actuator 110, however is omitted from the drawings for a clear description of the features of the piezoelectric vibrator according to the embodiment of the present invention.
[30] The piezoelectric vibrator according to the embodiment of the present invention, as illustrated in FIGS. 7 and 8, includes a vibration transmission elastic material 120 attached to the piezoelectric actuator to transmit the mechanical vibration generated from the actuator 110 to the exterior. However, as illustrated in FIG. 9, the piezoelectric vibrator may include only a laminated piezoelectric actuator. Moreover, the piezoelectric actuator may have a rectangular shape, a disk shape, or the like, and the piezoelectric materials 110a and the elastic materials 110b may be different from or identical to in a size or a shape. The configuration of the piezoelectric actuator according to the present inventionis not limited to the embodiments illustrated in the drawings.
[31] According to the present invention, since the piezoelectricvibrator uses a thin metal as an elastic material and at least two piezoelectric actuators laminated by interposing the sound absorbing material, the low-pitched sound range can expanded widely to the range equal to or less than 100 Hz and a high sound pressure can be obtained over whole sound range. In this case, a sound pressure increased more than 20 dB in comparison to that of the conventional piezoelectric vibrator illustrated in FIGS. 1 to 6 can be obtained.
[32] FIG. 10 is a view illustratinga panel speaker in which a housing 140 is applied to the piezoelectric vibrator in FIG. 7. In order to further expand the sound range containing the low-pitched sound range, the housing 140 is preferably made by a polymer resin to enclose the piezoelectric vibrator.
[33] FIG. 11 illustrates data comparing sound pressure of the piezoelectric vibrator according to the embodiment of the present invention with that of the conventional bimorph piezoelectric vibrator. FIG. 11 also illustrates the sound pressure when the housing is employed. A flat board speaker employing the laminated piezoelectric vibrator and the housing can provide an enhanced sound pressure in the low-pitched sound rage equal to or less than 500 Hz.
[34] In a vibrator of a previous invention including only a single actuator, a low sound pressure is generated in a low-pitched sound equal to or less than 500 Hz, and the sound pressure of the low-pitched sound only is enhanced. When the housing is appl ied in order to compensate this phenomenon, the sound pressure is generally decreased. Even when the laminated structure is applied alone to the vibrator, overall sound pressure is enhanced in comparison to the previous invention. If both the laminated structure and the housing are applied to the vibrator, the sound pressure in the low- pitched sound equal to or less than 500 Hz is more enhanced.
[35] The piezoelectric vibrator 100 is mounted at a predetermined place of an edge of a vibrating panel 200. Vibration generated in the multiple layer piezoelectric actuator 110 transmitted to the vibrating panel 200 via the first portion 120a and the second portion 120b of the vibration transmission elastic material 120 to be emitted out as sound. The piezoelectric vibrator 100 of the present invention including the multiple layer piezoelectric actuator 110 can provide the sound pressure much higher than that of the conventional piezoelectric vibrator due to the geometrical structural feature thereof.
[36] FIG. 12 illustrates another embodiment to which the piezoelectric vibrator according to the present inventioncan be applied and a schematic view illustrating a piezoelectric buzzer earphone employing a multiple layer piezoelectric vibrator in FIG. 9. Reference numerals 140, 150, 160, 170, and 200 in FIG.9 are assigned to a housing of the vibrator, a housing of the earphone, a unit cap, an air duct, and a vibrating panel, respectively.
[37] In the piezoelectric vibrator according to the present invention, it is preferred that the elastic materials are metal such as copper, tungsten, aluminum, or alloys thereof. Moreover, the elastic materials can be a material having a large Young's modulus, preferably, a polymer material having Young's modulus equal to or greater than 10 GPa, and is not limited to the kinds. However, when metal is used as the elastic material such as a metal plate equal to or less than 30 micrometers, it is more effective.
[38] It is preferred that adhesive having a high hardness after being hardened such as epoxy is used as the laminating material using the sound absorption material and a phenomenon that a signal is decreased can be minimized.
[39] When the piezoelectric vibrator according to the present invention includes the vibration transmission elastic material, thicknesses, cross-sectional shapes, sizes, centers of gravity of the piezoelectric actuator 110 the elastic material 120 can be properly adjusted according to an apparatus to which the piezoelectric actuator and the elastic material are applied.
[40] According to another feature of the present invention, it is preferred that the piezoelectric material 110a is a poly crystalline ceramic of a lead zirconium titanate (PZT) that is widely used, or a single crystalline ceramic having a superior piezoelectric property.
[41] As a ferroelectric single crystalline material used in the present invention, lead magnesium niobate-lead titanate (PMN-PT), lead zinc niobate-lead titanate (PZN-PT), lead zirconium titanate (PZT), lead ytterbium niobate-lead titanate (PYT-PT), or lead indium niobate-lead titanate may be used.
[42] According to another feature of the present invention, the polycrystalline material or the single crystalline material of the piezoelectric material 110a may be bulk type or a film type, or may have a single layer or multiple layers. When a piezoelectric single crystalline material is made into a single layer, a bulk type piezoelectric single crystalline material may be grinded in the form of a thin film to be attached to an electrode or may be attached to the electrode to be grinded in the form of a thin film. When the piezoelectric single crystalline material is made into the thin film, the overall thickness of the piezoelectric actuator 110 may decrease.
[43] Although the preferred embodiment of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

Claims
[1] A piezoelectric vibrator to reproduce sound using piezoelectric actuators to convert an electric signal into a mechanical vibration, the piezoelectric vibrator comprising: two or more laminated piezoelectric actuators respectively including elastic ma- terialand piezoelectric material attached to one side or both sides of the elastic material; and an sound absorption material disposed between the laminated piezoelectric actuators.
[2] The piezoelectric vibrator to reproduce sound according to claim 1, wherein the elastic material comprises a metal.
[3] The piezoelectric vibrator to reproduce sound according to claim 1, wherein the elastic material comprises one or moreselected from a group of copper, tungsten, aluminum, and alloys thereof having a thickness equal to or less than 30 micrometers.
[4] The piezoelectric vibrator to reproduce sound according to claim 1, wherein the elastic material comprises polymer having Young's module equal to or greater than 10 GPa.
[5] The piezoelectric vibrator to reproduce sound according to claim 1, wherein the sound absorption material comprises one or more selected from a group of a polymer nano-fiber, a carbon nano-tube, a non-woven fabric, nano-particles, or porous particles.
[6] The piezoelectric vibrator to reproduce sound according to claim 1, wherein the sound absorption material and the piezoelectric actuators are laminated using an epoxy adhesive.
[7] The piezoelectric vibrator to reproduce sound according to claim 1, wherein the piezoelectric material comprises a lead zirconium titanate (PZT) polycrystalline ceramic material or a ferroelectric single crystalline ceramic material selected from a group of a lead magnesium niobate-lead titanate (PMN-PT), a lead zinc niobate-lead titanate (PZN-PT), a lead zirconium titanate (PZT), a lead ytterbium niobate-lead titanate (PYT-PT), or lead indium noibate-lead titanate.
[8] The piezoelectric vibrator to reproduce sound according to claim 7, wherein the piezoelectric material comprises a single layer or multiple layers.
[9] The piezoelectric vibrator to reproduce sound according to claim 8, wherein respectively layers of the multiple layer piezoelectric material have an identical cross-sectional area and an identical shape, or neither the cross-sectional area nor the shape.
[10] The piezoelectric vibrator to reproduce sound according to claim 7, wherein the piezoelectric material comprises a bulk type or a thin film type of the poly- crystalline material or a bulk type or a thin film type of the single crystalline material.
[11] A piezoelectric panel speaker comprising a piezoelectric vibrator to reproduce sound according to any one of claims 1 to 10.
[12] The piezoelectric panel speaker according to claim 11, wherein the piezoelectric vibrator is enclosed by a housing made by a polymer resin to expand a sound range containing a low-pitched sound range.
[13] A piezoelectric earphone comprising the piezoelectric vibrator to reproduce sound according to any one of claims 1 to 10.
PCT/KR2006/005816 2006-05-19 2006-12-28 Piezoelectric vibrator for regenerating sound, and piezoelectric panel speaker and piezoelectric earphone having the same WO2007136162A1 (en)

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