JP2013153314A - Piezoelectric type electroacoustic transducer, electronic apparatus using the same, and electroacoustic conversion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric type electroacoustic transducer with high reliability against mechanical impact, having a flat frequency characteristic, and capable of outputting a loud voice sound even with a small size.SOLUTION: In a piezoelectric type electroacoustic transducer, a piezoelectric ceramics 3 with a torus shape is disposed in such a way as constrained by an elastic member 4 whose one end face is fixed to a frame 6 of a support member, and the transducer includes at least a vibration transmission member 2 which transmits vibration from the piezoelectric ceramics 3, and a vibrating diaphragm 1 which emits sound waves due to a vibration from the vibration transmission member 2. Impact caused when the transducer is dropped is absorbed by the vibration transmission member 2 and the vibrating diaphragm 1 having high flexibility, and the vibrating diaphragm 1 is vibrated through the elastic member 4 having a high internal loss, thus reducing mechanical quality factor Q, for flattening sound pressure frequency characteristic, while a vibrational amplitude is amplified by inertia and resilience of the vibration transmission member 2 with contractility, thereby allowing transmission to the vibrating diaphragm 1.

Description

  The present invention relates to a piezoelectric electroacoustic transducer, an electronic device using the piezoelectric electroacoustic transducer, and an electroacoustic transducing method, and more particularly to a piezoelectric electroacoustic transducer that has good frequency characteristics and is small and capable of high output. The present invention relates to an electronic device and an electroacoustic conversion method.

  As for mobile phones, development of thin and stylish mobile phones that have commercial values of sound functions such as music playback and hands-free headsets has become active.

  Among acoustic functions mounted on electronic devices such as mobile phones, electroacoustic transducers are highly demanded for being small and thin and having high sound quality. In the case of an electronic device such as a normal cellular phone, as described in Japanese Patent Application Laid-Open No. 2008-177692 “Electroacoustic Transducer” of Patent Document 1, a speaker has a simple structure and acoustic characteristics. Therefore, in general, electrodynamic (dynamic) speakers are used.

  However, since the sound pressure level of an electrodynamic speaker using a magnetic circuit depends on the volume exclusion amount, the sound pressure level is limited in principle. For this reason, it is necessary to increase the amount of vibration amplitude in order to increase the sound pressure. However, considering the driving force of the magnetic circuit, the magnetic flux is a factor, so there is a trade-off relationship with the volume of the magnet. There is. In addition, it is necessary to reduce the thickness of the voice coil as well as to reduce the thickness of the voice coil. However, in a magnetic circuit through which a large current flows, there are problems such as burning of the thinned voice coil.

JP 2008-177692 A (page 4-6)

  In order to solve the above-described electrodynamic type problem, there is a piezoelectric electroacoustic transducer as a thin electroacoustic transducer that replaces the electrodynamic type. Piezoelectric electroacoustic transducers generate vibration amplitude using the electrostrictive effect of piezoelectricity. In the case of a piezoelectric electroacoustic transducer, since the piezoelectric element itself becomes a vibration source, it is advantageous for thinning. However, as a problem of the piezoelectric electroacoustic transducer, there are a high mechanical quality factor Q and a lack of drop stability.

  In other words, since the piezoelectric electroacoustic transducer has a high mechanical quality factor Q, a large sound pressure level can be obtained in the vicinity of the resonance frequency, but the sound pressure level is rapidly attenuated in a frequency band away from the vicinity of the resonance frequency. To do. As a result, a valley occurs in the sound pressure frequency characteristic, and the flat sound pressure frequency characteristic, which is an indispensable factor for improving the sound quality, deteriorates.

  In addition, since the piezoelectric ceramic used for the piezoelectric element is a brittle material, when stress is concentrated on a specific location, breakage such as cracking or chipping occurs. As a result, there is a high possibility of breakage when an impact such as dropping is applied. An electronic device such as a mobile phone has a problem from the viewpoint of practicality because high impact resistance against dropping is required.

  In addition, since piezoelectric ceramics have high rigidity, a large shape is required to obtain a low resonance frequency. There has been a practical problem in electronic devices such as mobile phones that require miniaturization. For this reason, when the piezoelectric electroacoustic transducer is to be adopted in an electronic device such as a mobile phone, it is a revolutionary measure that has high reliability against mechanical shock and reproduces high-quality sound. Was needed.

(Object of the present invention)
The present invention has been made in view of such problems, has high reliability against mechanical shock, has a flat frequency characteristic, and enables large audio output even if it is small. A piezoelectric electroacoustic transducer, an electronic apparatus using the same, and an electroacoustic conversion method are provided.

  In order to solve the above-described problems, the piezoelectric electroacoustic transducer, the electronic apparatus using the piezoelectric electroacoustic transducer, and the electroacoustic conversion method according to the present invention mainly adopt the following characteristic configuration.

  (1) A piezoelectric electroacoustic transducer according to the present invention is a piezoelectric electroacoustic transducer in which a torus-shaped piezoelectric ceramic is disposed in a state of being constrained by an elastic member having one end face fixed to a support member, At least a vibration transmission member that transmits vibration from the piezoelectric ceramic and a vibration film that radiates vibration from the vibration transmission member as sound waves, and the vibration propagated from the piezoelectric ceramic via the vibration transmission member It outputs as a sound wave from a vibration film, It is characterized by the above-mentioned.

  (2) An electronic device according to the present invention uses at least the piezoelectric electroacoustic transducer described in (1) as an electroacoustic transducer that converts an electrical signal into an audio signal in an electronic device having an audio output function. It is characterized by that.

  (3) An electroacoustic conversion method according to the present invention is an electroacoustic conversion method for converting an electric signal into an audio signal, and a torus-shaped piezoelectric ceramic is restrained by an elastic member having one end surface fixed to a support member. A vibration transmission member disposed in a state and transmitting vibrations from the piezoelectric ceramic and a vibration film that radiates vibrations from the vibration transmission member as sound waves, and from the piezoelectric ceramics via the vibration transmission member The vibration propagated in this manner is output as a sound wave from the vibration film.

  According to the piezoelectric electroacoustic transducer of the present invention, the electronic apparatus using the same, and the electroacoustic conversion method, the following effects can be obtained.

  First, since the piezoelectric ceramic forming the piezoelectric element is disposed in a state of being constrained by an elastic member having one end face fixed to a support member (frame), an elastic member having a large internal loss is interposed through the elastic member. The vibration film is vibrated, the mechanical quality factor Q of the piezoelectric electroacoustic transducer can be reduced, and the sound pressure frequency characteristics can be flattened.

  Second, even if a situation in which the piezoelectric electroacoustic transducer is accidentally dropped occurs, the impact at the time of dropping can be absorbed by a highly flexible vibration transmission member and vibration membrane, The reliability of the piezoelectric ceramic made of a brittle member against mechanical impact can be improved.

  Thirdly, the vibration transmitting member is made of resin, carbon-based material, etc., and is composed of a material having shrinkage, so that the vibration amplitude from the piezoelectric ceramic is increased by the effect of inertia and restoring force, It can be transmitted to the diaphragm, and the audio output width can be expanded.

It is sectional drawing which shows an example of an internal structure of the piezoelectric type electroacoustic transducer of this invention as Example 1. FIG. It is the perspective view which looked at the piezoelectric type electroacoustic transducer shown in FIG. 1 from diagonally upward. It is sectional drawing which shows the structural example different from FIG. 1 of the internal structure of the piezoelectric type electroacoustic transducer of this invention as Example 2. FIG. It is sectional drawing which shows an example of the internal structure of the conventional piezoelectric type electroacoustic transducer as the comparative example 1. FIG. It is sectional drawing which shows the other example of the internal structure of the conventional piezoelectric electroacoustic transducer as the comparative example 2. FIG. It is a characteristic view which shows the frequency characteristic of the sound pressure level of the piezoelectric electroacoustic transducer of Example 1, 2 shown in FIG. 1, FIG.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a piezoelectric electroacoustic transducer, an electronic apparatus using the piezoelectric electroacoustic transducer, and an electroacoustic conversion method according to the invention will be described with reference to the accompanying drawings. In the following description, the piezoelectric electroacoustic transducer and the electroacoustic conversion method according to the present invention will be described. However, an electronic device equipped with the piezoelectric electroacoustic transducer according to the present invention may be a mobile phone or a PHS (Personal Handy). -Needless to say, any device may be used as long as it is an electronic device having a voice output function, such as a Phone System), a PDA (Personal Digital Assistants), a PC (Personal Computer), a smartphone terminal, a tablet terminal, or a music player terminal. Yes.

(Features of the present invention)
Prior to the description of the embodiments of the present invention, an outline of the features of the present invention will be described first. The present invention relates to a structure of a piezoelectric electroacoustic transducer. As a piezoelectric electroacoustic transducer, vibration from a piezoelectric element constrained by an elastic member having one end face fixed to a support member. By having a structure including a vibration transmission member that transmits and a vibration film that radiates vibration from the vibration transmission member as a sound wave, the structure has high mechanical reliability and has a flat frequency characteristic, and The main feature is to realize an electroacoustic transducer capable of reproducing a large volume with high efficiency even if it is small.

(Configuration example of embodiment)
Example 1
Next, a configuration example of the piezoelectric electroacoustic transducer of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing an example of an internal configuration of a piezoelectric electroacoustic transducer according to the present invention as a first embodiment. A piezoelectric electroacoustic transducer 10 shown in FIG. 1 includes at least a vibration film 1, a vibration transmission member 2, a piezoelectric ceramic 3, an elastic member 4, a holding member 5, and a frame 6.

  In the piezoelectric electroacoustic transducer 10 shown in FIG. 1, a torus (annular) piezoelectric ceramic 3 (piezoelectric element) is formed in a state of being restrained by an elastic member 4. The elastic member 4 is composed of a metal plate, and one end face thereof is directly joined and fixed to a frame 6 that is a support member.

The piezoelectric ceramic 3 (piezoelectric element) includes a piezoelectric ceramic and an electrode layer. PZT (zirconate titanate PbZr _1-x Ti _x O ₃ : perovskite oxide ferroelectric), barium titanate, etc. can be used for the piezoelectric ceramic, and silver, silver / silver A palladium alloy or the like can be used.

  A holding member 5 made of metal is disposed in the hollow portion of the torus-shaped piezoelectric ceramic 3 (piezoelectric element), and the vibration transmission member 2 is disposed on the holding member 5. The vibration transmission member 2 is made of a resin, a carbon-based material, or the like, and is connected to the central portion of the vibration film 1 having a peripheral edge joined to the frame 6. The vibration film 1 is made of a resin material or the like and functions as a vibration surface that emits sound waves.

  FIG. 2 is a perspective view of the piezoelectric electroacoustic transducer 10 shown in FIG. 1 as viewed obliquely from above, with the upper member of the frame 6 forming a side wall as a support member removed and the interior exposed. It shows the state that was made to. As shown in FIG. 2, the piezoelectric electroacoustic transducer 10 has a cylindrical shape. From above, the vibration film 1, the vibration transmission member 2, the piezoelectric ceramic 3, the elastic member 4, and the holding member 5 are sequentially arranged concentrically. Arranged and covered by the frame 6 of the support member.

(Example 2)
Next, a configuration example different from FIG. 1 of the internal configuration of the piezoelectric electroacoustic transducer of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view showing a configuration example different from FIG. 1 of the internal configuration of the piezoelectric electroacoustic transducer of the present invention as Example 2. A piezoelectric electroacoustic transducer 10A shown in FIG. 3 differs from the piezoelectric ceramic 3 in FIG. 1 in that a torus-shaped piezoelectric ceramic in which the size of the hollow portion is different on both the front surface side and the back surface side of the elastic member 4. 3a and 3b are fixed to each other.

  That is, in the piezoelectric electroacoustic transducer 10A shown in FIG. 3, the elastic member 4 having one end face fixed to the frame 6 is disposed in a state of constraining the entire surface-side piezoelectric ceramic 3a, and the elastic member The entire torus-like piezoelectric ceramic 3b having a hollow portion larger than the piezoelectric ceramic 3a is constrained on the back surface side of the piezoelectric ceramic 3a.

  And the holding member 5 arrange | positioned in the hollow part of the torus-like piezoelectric ceramics 3a and 3b contacted the back surface side of the elastic member 4 unlike the case where it contacted the piezoelectric ceramic 3 directly like the case of FIG. As in the case of FIG. 1, the vibration transmission member 2 is disposed on the holding member 5. As in the case of FIG. 1, the vibration transmission member 2 is made of a resin, a carbon-based material, or the like, and is connected to the central portion of the vibration film 1 with the peripheral edge joined to the frame 6. The vibration film 1 is made of a resin material or the like, as in FIG. 1, and functions as a vibration surface that emits sound waves.

(Operational effects of the piezoelectric electroacoustic transducers 10 and 10A of the first and second embodiments)
Next, the function and effect of the piezoelectric electroacoustic transducers 10 and 10A of the first and second embodiments shown in FIGS. 1 and 3 will be described.

  A voltage is applied to the piezoelectric ceramic 3 that forms the piezoelectric element in the piezoelectric electroacoustic transducer 10 shown in FIG. 1 and the piezoelectric ceramics 3a and 3b that form the piezoelectric element in the piezoelectric electroacoustic transducer 10A shown in FIG. Thus, the piezoelectric ceramic 3 and the piezoelectric ceramics 3a and 3b are caused to expand and contract by the piezoelectric effect, and mechanical vibrations are generated. The vibrations from the piezoelectric ceramic 3 and the piezoelectric ceramics 3a and 3b are joined to the frame 6 through the piezoelectric ceramic 3, the holding member 5 bonded to the piezoelectric ceramics 3a and 3b, and the vibration transmitting member 2. Propagated to the center of the vibration film 1 and radiated as sound waves from the vibration film 1.

  Here, since the piezoelectric ceramic 3 and the piezoelectric ceramics 3a and 3b forming the piezoelectric element are arranged in a state of being restrained by the elastic member 4 having one end surface fixed to the frame 6, the elastic having a large internal loss. The vibration film 1 is vibrated through the member 4, the mechanical quality factor Q of the piezoelectric electroacoustic transducers 10 and 10A can be reduced, and the sound pressure frequency characteristics can be flattened. .

  In addition, even if a situation in which the piezoelectric electroacoustic transducers 10 and 10A of the first and second embodiments shown in FIGS. 1 and 3 are accidentally dropped occurs, the impact at the time of dropping is transmitted with a highly flexible vibration. It can be absorbed by the member 2 and the vibration film 1, and the reliability of the piezoelectric ceramic 3 and the piezoelectric ceramics 3a and 3b made of a mechanical brittle member can be improved.

  Furthermore, since the vibration transmission member 2 is made of a resin, a carbon-based material, or the like and is made of a shrinkable material, vibrations from the piezoelectric ceramic 3 and the piezoelectric ceramics 3a and 3b are obtained due to the effects of inertia and restoring force. The amplitude can be expanded and transmitted to the diaphragm 1, and the audio output width can be expanded.

  Next, the electrical characteristics of the piezoelectric electroacoustic transducers 10 and 10A of Examples 1 and 2 shown in FIGS. 1 and 3 are compared with the case where the internal configuration of the conventional piezoelectric electroacoustic transducer is used. The results will be described with reference to the characteristic diagram of FIG. FIG. 6 is a characteristic diagram showing the frequency characteristics of the sound pressure level of the piezoelectric electroacoustic transducers 10 and 10A of the first and second embodiments shown in FIGS. 1 and 3, and the characteristic improvement of the first and second embodiments. In order to show the effect, the conventional piezoelectric electroacoustic transducer is also shown by a broken line.

  Here, the internal configuration of the conventional piezoelectric electroacoustic transducer is configured as shown in FIG. 4 or FIG. FIG. 4 is a cross-sectional view showing an example of the internal configuration of a conventional piezoelectric electroacoustic transducer as Comparative Example 1, and vibration transmission from the piezoelectric electroacoustic transducer 10A of FIG. 3 shown as Example 2 of the present invention. The member 2 and the vibrating membrane 1 are removed. FIG. 5 is a cross-sectional view showing another example of the internal configuration of the conventional piezoelectric electroacoustic transducer as Comparative Example 2, in which the front side and the back side of the elastic member 4a having the entire end face fixed to the frame 6 are shown. This shows a case in which cylindrical piezoelectric ceramics 3c and 3d are fixed to both sides.

  As shown in FIG. 6, both of the piezoelectric electroacoustic transducers 10 and 10A of Examples 1 and 2 shown in FIGS. 1 and 3 are the same as those of Comparative Examples 1 and 2 shown in FIGS. It can be seen that, compared to the piezoelectric electroacoustic transducer, a high sound pressure level can be obtained in almost all frequency bands, and a flat frequency characteristic is realized.

  Accordingly, the piezoelectric electroacoustic transducers 10 and 10A of the first and second embodiments shown in FIGS. 1 and 3 are both small and have a high sound pressure level compared to the conventional piezoelectric electroacoustic transducer. And flat frequency characteristics at the same time, and as described above, high reliability against mechanical shock can be ensured. It can be used in practical applications by being mounted on electronic equipment.

  Here, as an electronic device on which a piezoelectric electroacoustic transducer such as the piezoelectric electroacoustic transducers 10 and 10A of the first and second embodiments is mounted, a mobile phone, a PHS (Personal Handy-Phone System), a PDA (Personal Any device may be used as long as it is an electronic device having an audio output function, such as Digital Assistants), a PC (Personal Computer), a smartphone terminal, a tablet terminal, and a music player terminal.

  The configuration of the preferred embodiment of the present invention has been described above. However, it should be noted that such embodiments are merely examples of the present invention and do not limit the present invention in any way. Those skilled in the art will readily understand that various modifications and changes can be made according to a specific application without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Vibration membrane 2 Vibration transmission member 3 Piezoelectric ceramic 3a Piezoelectric ceramic 3b Piezoelectric ceramic 3c Piezoelectric ceramic 3d Piezoelectric ceramic 4 Elastic member 4a Elastic member 5 Holding member 6 Frame (support member)
10 Piezoelectric Electroacoustic Transducer 10A Piezoelectric Electroacoustic Transducer

Claims (8)

  A piezoelectric electroacoustic transducer in which a torus-shaped piezoelectric ceramic is constrained by an elastic member having one end face fixed to a support member, the vibration transmitting member transmitting vibration from the piezoelectric ceramic, A piezoelectric film that includes at least a vibration film that radiates vibration from a vibration transmission member as sound waves, and outputs vibrations propagated from the piezoelectric ceramics through the vibration transmission member as sound waves from the vibration film. Electroacoustic transducer.   One end of the vibration transmitting member is joined to a holding member arranged in a hollow portion of the torus-shaped piezoelectric ceramic, and the other end of the vibration transmitting member is joined to the support member at the central portion of the vibration membrane. The piezoelectric electroacoustic transducer according to claim 1, wherein the piezoelectric electroacoustic transducer is connected to the piezoelectric electroacoustic transducer.   The torus-shaped piezoelectric ceramics having different hollow portions are respectively disposed on the front surface and the back surface of the elastic member having one end surface fixed to the support member. Piezoelectric electroacoustic transducer.   The vibration transmitting member is made of a resin or a carbon-based material, the vibration film is made of a resin material, and the elastic member is made of a metal plate. Piezoelectric electroacoustic transducer.   5. An electronic apparatus having an audio output function, wherein the piezoelectric electroacoustic converter according to claim 1 is used as an electroacoustic converter for converting an electric signal into an audio signal. .   An electroacoustic conversion method for converting an electric signal into an audio signal, wherein a torus-shaped piezoelectric ceramic is disposed in a state of being constrained by an elastic member having one end face fixed to a support member, and from the piezoelectric ceramic A vibration transmission member that transmits vibration and a vibration film that radiates vibration from the vibration transmission member as sound waves, and vibrations propagated from the piezoelectric ceramics through the vibration transmission member are converted into sound waves from the vibration films. An electroacoustic conversion method characterized by outputting.   One end of the vibration transmitting member is joined to a holding member arranged in a hollow portion of the torus-shaped piezoelectric ceramic, and the other end of the vibration transmitting member is joined to the support member at the central portion of the vibration membrane. The electroacoustic conversion method according to claim 6, wherein the electroacoustic conversion method is connected to the electroacoustic conversion method.   8. The torus-shaped piezoelectric ceramics having different hollow sizes are respectively disposed on the front surface and the back surface of the elastic member having one end surface fixed to the support member. Electroacoustic conversion method.

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