JP2011228794A - Electro-acoustic transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electro-acoustic transducer which is used for electronic equipment such as a cellular phone and by which reproduction of large volume and excellent sound pressure level frequency characteristics are possible though it is small.SOLUTION: In the electro-acoustic transducer, a plurality of diaphragms are formed on an array, and mountain-valley of acoustic characteristics is restored by individual and peculiar drive of the plurality of diaphragms with different reference resonance frequencies. Since the reference resonance frequency is determined by the shape of outer periphery of a vibrator, namely, periodicity, for the respective vibrators, the one with the long outer periphery has a low reference resonance frequency though they are circular in the same shape. The vibrator is the one of a unimorph type for restricting one piezoelectric element by an elastic member. In addition, electrode layers are formed on the upper and lower surfaces of the piezoelectric element, and the piezoelectric element operates by inputting an electric signal. The vibrator generates vibrational amplitude by utilizing a piezoelectric effect by the piezoelectric element.

Description

  The present invention relates to an electroacoustic transducer, and more particularly to an electroacoustic transducer used in an electronic device such as a mobile phone.

  In recent years, the demand for portable terminals (portable electronic devices) such as mobile phones and laptop personal computers (PCs) has increased. Under such circumstances, companies developing mobile devices are working on the development of high-value-added models that balance style and function, and the demand for small electroacoustic transducers with high volume and high sound quality is increasing. It's getting on.

  Conventionally, electrodynamic electroacoustic transducers have been used as acoustic components for electronic devices such as mobile phones. This electrodynamic electroacoustic transducer is composed of a permanent magnet, a voice coil, and a diaphragm. The principle of operation is that a vibration film such as an organic film fixed to a voice coil vibrates by the action of a magnetic circuit of a stator using a magnet to generate sound waves.

  However, in the acoustic performance of the electroacoustic transducer, the sound pressure level, which is a physical strength indicating the volume, is determined by the volume exclusion of the diaphragm with respect to the air. In other words, since it depends on the radiation area and the amount of amplitude, it is impossible in principle to achieve both size reduction and volume enhancement, and there is a big problem in mounting on a portable terminal that requires size reduction.

  In addition, the electrodynamic electroacoustic transducer uses a magnetic circuit as a driving source, so that a high magnetic flux density is generated to obtain a high amplitude, and the volume of the magnet, particularly the thickness direction, is sufficiently secured. Therefore, there is a limit to reducing the thickness. For example, electrodynamic electroacoustic transducers require a thickness of about 3 mm even for thin products, which is a major obstacle to promoting the stylishness of mobile phones (realization of sophisticated designs that fit the trend, reduction in size and weight). ing.

  On the other hand, there is a piezoelectric method as a method for providing a thin electroacoustic transducer. This piezoelectric method uses a piezoelectric effect of a ceramic material to generate a vibration amplitude by an electrostrictive action by inputting an electric signal. Since the ceramic itself, whose upper and lower layers are constrained by electrode materials, vibrates, it is superior in thinning compared to a magnetic circuit composed of a large number of members such as magnets and voice coils. Further, from the principle of vibration deflection, when the same electric field is input, the electric field strength increases, and therefore the thickness and amplitude of the ceramic material are proportional, which is advantageous as a thin driving source.

  However, since the ceramic material is a brittle material and has a small mechanical loss, the mechanical quality factor Q tends to be higher than that of an electrodynamic electroacoustic transducer that generates an amplitude from an organic film. For example, the electrodynamic type is about 3 to 5 and the piezoelectric type is about 50. Since the mechanical quality factor Q indicates sharpness at the time of resonance, the summary means that in the piezoelectric electroacoustic transducer, the sound pressure is high near the fundamental resonance frequency and the sound pressure is attenuated in other bands. In other words, in the sound pressure level frequency characteristics, there are peaks and valleys in the acoustic characteristics (abnormal values of the upper and lower limits of the amplitude), and the sound at a specific frequency is emphasized or lost, so that sufficient sound quality for music playback etc. is obtained. There is a problem that it may not be possible.

  For this reason, an epoch-making technology for producing a small electroacoustic transducer with high sound quality has been required.

  As a related technique, Japanese Patent Laid-Open No. 2003-153371 discloses an ultrasonic reproduction method and an ultrasonic reproduction apparatus. In this related technology, in the ultrasonic reproducing apparatus, the electroacoustic transducer has a plurality of piezoelectric elements having different resonance frequencies mounted on a common base. The electroacoustic conversion unit may be configured by arranging a plurality of ultrasonic elements EL (electro-luminescence) in a matrix or concentric circles on one surface.

  Patent Document 2 (Japanese Patent Laid-Open No. 2006-081117) discloses a super-directional speaker system. In this related technology, the super directional speaker system includes a plurality of ultrasonic transducers arranged in an array, and controls the output time difference of the plurality of ultrasonic transducers according to the demodulation direction by a phase controller. ing. Further, at least one of the amplitude of the carrier signal and the modulation degree in the amplitude modulation is controlled according to at least one of the carrier signal and the original sound signal. Thus, the sound pressure of the carrier wave is reduced while the sound pressure of the bitone sound is appropriately set, and the efficiency of sound output is improved.

  Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2009-260573) discloses a microphone unit and a method for manufacturing the same. In this related technology, a separation wall is provided that surrounds each of the plurality of diaphragm unit arrangement planned areas on the microphone substrate. The diaphragm unit may be configured as a so-called MEMS (MEMS: Micro Electro Mechanical Systems). In addition, the diaphragm may be one that uses an inorganic piezoelectric thin film or an organic piezoelectric thin film to perform acoustic-electric conversion by the piezoelectric effect, or may use an electret film. Further, the microphone substrate may be composed of a material such as an insulating molded base material, fired ceramics, glass epoxy, or plastic.

  Patent Document 4 (Japanese Patent Laid-Open No. 2009-296055) discloses an ultrasonic probe and an ultrasonic diagnostic apparatus using the same. In this related technique, a plurality of piezoelectric elements are arranged in an array (one-dimensional array). Each piezoelectric element is composed of a laminated piezoelectric element in which a receiving layer and an acoustic lens are laminated on a transmission layer. Each piezoelectric element is arranged on the substrate with a predetermined gap (groove, gap, gap) therebetween to reduce mutual interference such as crosstalk. Further, in order to reduce mutual interference, the gap is filled with an ultrasonic absorber that absorbs ultrasonic waves. As the ultrasonic absorbing material, a thermosetting resin such as a polyimide resin or an epoxy resin can be used. Further, the piezoelectric element layer of the transmission layer and the piezoelectric element layer of the reception layer are composed of a plurality of different thickness portions. Here, the resonance frequency of the piezoelectric element layer is adjusted in inverse proportion to the piezoelectric vibration direction, that is, the thickness in the thickness direction of the piezoelectric element layer, and is doubled at half thickness and quadrupled at 1/4 thickness. The resonance frequency can be set. Therefore, even if each thickness part is vibrated with a common electrode, a plurality of frequencies can be individually transmitted and received.

JP 2003-153371 A JP 2006-081117 A JP 2009-260573 A JP 2009-296055 A

  An object of the present invention is to provide an electroacoustic transducer in which a plurality of diaphragms are formed on an array, and each of a plurality of diaphragms having different fundamental resonance frequencies is independently driven to restore a valley of acoustic characteristics. It is.

  The electroacoustic transducer of the present invention is an electroacoustic transducer used in an electronic device, and includes a plurality of transducers arranged on an array and a frame surrounding the plurality of transducers. The outline shape of the frame surrounding all of the plurality of vibrators is constant. The contour shape of the individual frame surrounding each of the plurality of vibrators can be changed. Each vibrator has a different shape, is driven at an arbitrary timing, and has a different fundamental resonance frequency.

  The electroacoustic transducer of the present invention is mounted on an electronic device that uses electroacoustic conversion.

  The radiation direction of sound waves can be freely designed, and a wide directivity electroacoustic transducer can be obtained. As a result, it is possible to realize a small and high-quality electroacoustic transducer.

It is sectional drawing which shows the electroacoustic transducer of 1st Embodiment of this invention. It is a figure which shows the structural example of the vibrator | oscillator in 1st Embodiment of this invention. It is a figure which shows the structural example of the piezoelectric element in 1st Embodiment of this invention. It is a conceptual diagram of the vibrator | oscillator in 1st Embodiment of this invention. It is a structural diagram of lead zirconate titanate (PZT) shown as an example of a material having high electromechanical conversion efficiency. It is a conceptual diagram of divided vibration. It is a figure which shows the example of the phase of a division vibration. It is a figure which shows the structural example of the MEMS actuator which is a vibrator | oscillator in 2nd Embodiment of this invention. It is a figure which shows the structural example of the conventional electrodynamic electroacoustic transducer. In the electroacoustic transducer of 1st Embodiment of this invention, it is a figure for demonstrating the example which changed the outline shape of the flame | frame. It is a figure which shows the mobile telephone carrying the electroacoustic transducer of 1st Embodiment of this invention.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing the electroacoustic transducer of the present embodiment. As shown in FIG. 1, the electrodynamic electroacoustic transducer of this embodiment includes a vibrator 10 (10-i, i = 1 to n: n is the number of vibrators) and a frame 20.

  The vibrator 10 is assumed to be each of a plurality of vibrators. Here, as an example of the vibrator 10, nine vibrators 10-1 to 10-9 are shown. The transducers 10-1 to 10-9 are individually surrounded by the frame 20, and are arranged in an array.

  The vibrators 10-1 to 10-9 have different configurations and different fundamental resonance frequencies. For example, since the fundamental resonance frequency is determined by the shape of the outer periphery of the vibrator, that is, the periodicity, even if the vibrator 10-1 and the vibrator 10-2 are circular in the same shape, the vibrator 10 having a long outer circumference. -1 has a fundamental resonance frequency lower than that of the vibrator 10-2.

  Note that the piezoelectric system shown in FIG. 2 can be used for the structure of the vibrator 10. In this case, the vibrator 10 is of a unimorph type (Unimorph Type) in which one piezoelectric element is restrained by an elastic member.

  Referring to FIG. 2, the vibrator 10 includes a piezoelectric element 11 and an elastic member 12.

  The piezoelectric element 11 is provided on the elastic member 12. The piezoelectric element 11 and the elastic member 12 are surrounded by the frame 20.

  Here, as shown in FIG. 3, electrode layers are formed on the upper and lower surfaces of the piezoelectric element 11, and the piezoelectric element 11 operates by inputting an electric signal. In this case, the vibrator 10 generates vibration amplitude using the piezoelectric effect of the piezoelectric element 11.

  Referring to FIG. 3, the piezoelectric element 11 includes an upper electrode layer 111, a piezoelectric ceramic 112, and a lower electrode layer 113.

  The upper electrode layer 111, the piezoelectric ceramic 112, and the lower electrode layer 113 have a layer structure in order from the top. The upper electrode layer 111 is an electrode layer formed on the upper surface of the piezoelectric ceramic 112. The piezoelectric ceramic 112 is the core (main body) of the piezoelectric element 11. The lower electrode layer 113 is an electrode layer formed on the lower surface of the piezoelectric ceramic 112.

  The contents of FIGS. 1 to 3 are summarized as shown in FIG. That is, as shown in FIG. 4, when an AC voltage is applied to the upper electrode layer 111 and the lower electrode layer 113 and an AC electric field is applied, the piezoelectric ceramics 112 are separated from the upper electrode layer 111 and the lower electrode layer 113. A radial expansion / contraction motion (diameter expansion motion) is performed so that both main surfaces of the first and second surfaces expand or contract simultaneously. In other words, the piezoelectric element 11 performs an expansion / contraction motion that repeats the first deformation mode (a) in which the main surface expands and the second deformation mode (b) in which the main surface contracts. .

  As described above, in the electroacoustic transducer of this embodiment, nine piezoelectric vibrators operate to generate vibration amplitudes, thereby emitting sound waves.

  The vibrator of this embodiment has a function as an electromechanical converter that converts electrical energy into vibration energy.

  Any material having a piezoelectric effect may be used, regardless of whether it is an inorganic material or an organic material, but a material having high electromechanical conversion efficiency is preferable. As a material having high electromechanical conversion efficiency, for example, lead zirconate titanate (PZT) having a crystal structure as shown in FIG. 5 can be used.

  The elastic member that constrains the piezoelectric ceramic material (piezoelectric ceramics) is a material that has the function of transmitting vibrations from the piezoelectric element to the frame, such as shock absorption during dropping and expansion of vibration amplitude by reducing rigidity. Has function. As long as it is an elastic material, both metal and resin are not particularly limited. From the viewpoint of mechanical strength and workability, metal materials such as phosphor bronze, stainless steel, and copper can be used.

  Each of the vibrators constituting the electroacoustic transducer of this embodiment has an arbitrary basic resonance frequency.

  As a method of adjusting the fundamental resonance frequency of the vibrator, not only the means for changing the shape of the piezoelectric ceramic of the vibrator shown in FIG. 1 but also the thickness of the piezoelectric ceramic, the material and shape of the elastic member, and the like. It can respond by changing.

  The fundamental resonance frequency of the vibrator is determined by the load weight and rigidity. That is, even if it is the same material and the same shape, changing the thickness changes the rigidity and changes the fundamental resonance frequency. For example, by increasing the thickness of the piezoelectric element, the rigidity increases and the fundamental resonance frequency increases. The same applies to the elastic member. Further, even if the material of the elastic material is changed, the rigidity is changed and the basic resonance frequency can be adjusted.

  The vibrator of the present embodiment is configured by joining (adhering) piezoelectric ceramics, an elastic member, and a frame in a stacked manner.

  A commercially available adhesive agent etc. can be used for the joining (adhesion). For example, an epoxy adhesive is preferable. Moreover, it is preferable that the thickness of the apply | coated adhesive is 10-100 micrometers. If the thickness of the adhesive is less than 10 μm, uniform in-plane orientation on the adhesive substrate is difficult, thickness variation occurs within the surface, and adhesive strength decreases.

  Further, when the thickness of the adhesive exceeds 500 μm, the adhesive itself becomes a restraining member, which causes a decrease in vibration conversion efficiency. In this embodiment, a metal material or an organic material can be used for the frame, and the material is not particularly limited, but stainless steel, brass, or the like can be preferably used. For example, when a material with low rigidity such as a resin is used, the frame itself vibrates during propagation of vibration from the elastic member, causing energy loss and reducing conversion efficiency.

Hereinafter, the operation principle of the electroacoustic transducer of the present invention will be described.
The electroacoustic transducer of the present invention reproduces sound by driving a plurality of vibrations arranged on the array independently of each other.

  In the electroacoustic transducer shown in FIG. 1, sound is radiated by interference of sound waves radiated from nine vibrators. Further, since each vibrator has a different fundamental resonance frequency, it has a wide frequency band.

  The conventional electroacoustic transducer has a problem that the reproduction band is narrow because the sound wave is generated by using the resonance characteristics of a single vibrator. That is, since the acoustic energy is maximized in the vicinity of the resonance frequency, there is a problem that the sound pressure level is small in the band (low range) below the basic resonance frequency, and there is no profound feeling of sound.

  As a means to solve this, there is a method of reducing the fundamental resonance frequency of the electroacoustic transducer, but considering the energy distribution, if the energy is shifted to a low range where a large amount of vibration energy is required, There is a problem that the sound pressure level of 1 to 3 KHz is reduced, and the overall volume feeling is reduced.

  In the electroacoustic transducer of the present invention, since a plurality of vibrators are arranged to maximize the sound pressure level in a specific frequency band, a high sound pressure level can be realized in a wide frequency band. For example, in order to realize reproduction in a band of 100 Hz to 10 KHz that can reproduce music, by arranging vibrators having basic resonance frequencies of 250 Hz, 500 Hz, and 1 KHz, the area of each vibrator is small. Can increase the volume of the low range.

  In the electroacoustic transducer of the present invention, the sound pressure level frequency characteristics can be flattened by adjusting the basic resonance frequencies of the plurality of vibrators. This will be described in detail together with a description of the relationship between the divided vibration and the acoustic characteristics and the form of the divided vibration.

  As shown in FIG. 6, the divided vibration is formed by overlapping higher-order vibration modes generated after the fundamental resonance frequency, and a large number of vibration modes that move upside down are mixed in the radiation plane.

  In this vibration, unlike the piston motion (vibration mode generated at the fundamental resonance frequency) in which the entire surface translates in the same direction, the conversion efficiency from the input acoustic signal to the acoustic vibration is around the frequency at which the split vibration occurs. The sound pressure level frequency characteristics are undulating (sound characteristics of the sound characteristics), causing sound other than the sound signal to be generated, and the sound cannot be reproduced at a specific frequency, the sound is emphasized, or the reproduced sound is distorted. Yamatani).

  For example, the divided vibration shown in FIG. 7 forms a vibration state in which vibration modes having different phases (in-phase and opposite phase) are regularly mixed. In acoustic radiation in this divided vibration, vibration modes having different phases mixed in the radiation plane (in-phase and opposite phase) interfere with each other, and the radiated sound is cancelled.

  This means that the sound pressure is attenuated and a dip (dip: the meter indicating needle indicates a small value at the resonance frequency) is generated. For this reason, how to suppress the divided vibration has been regarded as an indispensable problem for realizing flattening of the sound pressure level frequency.

  Therefore, in the present invention, any one of the plurality of vibrators is driven in accordance with the frequency at which the acoustic peaks and valleys are generated. As a result, the sound pressure level frequency characteristic is flattened by generating a sound wave having an opposite phase that cancels the sound pressure peak, or generating a sound wave having the same phase that repairs the sound pressure dip, and interfering these sound waves. Can be realized.

  In the electroacoustic transducer of the present invention, it is possible to control wide directivity. That is, the directivity can be controlled by changing the deflection angle of the plane of vibration radiation.

  In a high frequency band where the sound wave straightness is high, there is a problem in terms of convenience for the user because of the narrow directivity characteristics and the acoustic characteristics at the viewing position are different. By arranging the vibrator, the radiation direction of the sound wave can be freely designed, so that a wide directivity electroacoustic transducer can be obtained.

  The electroacoustic transducer according to the present invention can also be used as a sound source of an electronic device (for example, a mobile phone, a laptop personal computer, a small game device, etc.). Since the overall shape of the electroacoustic transducer does not increase and the acoustic characteristics are improved, the electroacoustic transducer can be suitably used for a portable electronic device.

Second Embodiment
The second embodiment of the present invention will be described below.
In the electroacoustic transducer of this embodiment, a MEMS (micro electro mechanical system) actuator is used for the vibrator. The configuration other than the vibrator is the same as that of the first embodiment.

FIG. 8 shows a configuration example of the MEMS actuator.
As for the MEMS actuator, there are methods using electrostatic force, electromagnetic force, piezoelectric effect, and thermal strain, and any method can be used. In this embodiment, a method using the piezoelectric effect is used.

  As shown in FIG. 8, the MEMS actuator 30 includes an upper movable electrode layer 31, a piezoelectric thin film layer (dielectric band layer) 32, and a lower movable electrode layer 33.

  The MEMS actuator 30 corresponds to the piezoelectric element 11 shown in FIG. The upper movable electrode layer 31 corresponds to the upper electrode layer 111 shown in FIG. The piezoelectric thin film layer (dielectric band layer) 32 corresponds to the piezoelectric ceramic 112 shown in FIG. The lower movable electrode layer 33 corresponds to the lower electrode layer 113 shown in FIG.

  Similar to the first embodiment, this is a mechanism for generating vibration amplitude due to the piezoelectric effect, and is a mechanism for generating vibration amplitude by inputting an AC signal to the electrode layer.

  Examples of the MEMS actuator manufacturing method include a method of spraying solid molten particles on the electrode layer using an aerosol deposition method (Aerosol Deposition), but the manufacturing method is not particularly limited. Note that when the aerosol deposition method is used, the piezoelectric film can be easily adsorbed to a substrate such as a curved surface, so that the degree of freedom of the shape of the vibrator is increased, which is useful for improving the characteristics of the electroacoustic transducer.

<Relationship between each embodiment>
Note that the above embodiments can be implemented in combination.

<Description of effects>
As described above, according to the electroacoustic transducer of the present invention, a plurality of transducers are arranged on the array. That is, by arbitrarily driving vibrators having different fundamental resonance frequencies, the frequency band for reproducing sound waves is expanded.

  In addition, by controlling the drive timing, that is, the phase at any frequency, it is possible to cancel or amplify the acoustic characteristics of the peaks and valleys by sound wave interference, and the flat sound pressure level frequency in a wide frequency band The characteristic can be reproduced.

<Example of the present invention>
The characteristic evaluation of the electroacoustic transducer of the present invention was performed using evaluation items 1 to 3 below.

(Evaluation 1) Measurement of sound pressure level frequency characteristics The sound pressure level when an AC voltage of 1 V was input was measured with a microphone placed at a position away from the element by a predetermined distance. The predetermined distance is 10 cm unless otherwise specified, and the frequency measurement range is 10 Hz to 10 kHz.

(Evaluation 2) Measurement of flatness of sound pressure level frequency characteristics The sound pressure level when an AC voltage of 1 V was input was measured with a microphone placed at a position away from the element by a predetermined distance. The frequency measurement range was 10 Hz to 10 kHz, and in the measurement range of 2 kHz to 10 kHz, the flatness of the sound pressure level frequency characteristic was measured by the sound pressure level difference between the maximum sound pressure level Pmax and the minimum sound pressure level Pmin. As a result, a sound pressure level difference (which indicates a difference between the maximum sound pressure level Pmax and the minimum sound pressure level Pmin) within 20 dB (decibels) was set to “◯”, and 20 dB or more was set to “x”. This predetermined distance is 10 cm unless otherwise specified.

(Evaluation 3) Drop Impact Test A mobile phone equipped with an electroacoustic transducer was naturally dropped 5 times from directly above 50 cm, and a drop impact stability test was performed. Specifically, breakage such as cracks after the drop impact test was visually confirmed, and the sound pressure characteristics after the test were further measured. As a result, the difference in sound pressure level (referring to the difference between the sound pressure level before the test and the sound pressure level after the test) was 3 dB or less, and 3 dB or more was evaluated as x.

[Example 1]
The characteristics evaluation of the electroacoustic transducer described in the first embodiment of the present invention was performed. The evaluation results are as follows.

〔result〕
Sound pressure level (1 kHz): 93 dB
Sound pressure level (3 kHz): 90B
Sound pressure level (5 kHz): 94 dB
Sound pressure level (10 kHz): 89 dB
Flatness of sound pressure level frequency characteristics: ○
Drop impact stability: ○

  As is clear from the above results, according to the electroacoustic transducer of the present example, the sound pressure level frequency characteristics are flat, and no peaks or valleys with large acoustic characteristics are observed. Further, it was demonstrated that the fundamental resonance frequency is 1 kHz or less, the vibration amplitude is large, and the sound pressure level exceeds 80 dB in a wide frequency band of 1 to 10 kHz.

[Comparative Example 1]
As Comparative Example 1, a conventional electrodynamic electroacoustic transducer as shown in FIG.

  As shown in FIG. 9, a conventional electrodynamic electroacoustic transducer 40 includes a diaphragm 41, a voice coil 42, a frame 43, a pole piece (iron core) 44, a permanent magnet 45, and a permanent magnet (magnetic pole). Part) 46 and a yoke 47.

〔result〕
Sound pressure level (1 kHz): 77 dB
Sound pressure level (3 kHz): 75 dB
Sound pressure level (5 kHz): 76 dB
Sound pressure level (10 kHz): 97 dB
Flatness of sound pressure level frequency characteristics: ×
Drop impact stability: ×

[Example 2]
As Example 2, the electroacoustic transducer of the second embodiment was created.

〔result〕
Sound pressure level (1 kHz): 93 dB
Sound pressure level (3 kHz): 88 dB
Sound pressure level (5 kHz): 86 dB
Sound pressure level (10 kHz): 88 dB
Flatness of sound pressure level frequency characteristics: ○
Drop impact stability: ○

  As is clear from the above results, the electroacoustic transducer of this example has the same characteristics as in Example 1, and the sound pressure level frequency characteristics are flat regardless of the drive source system. It is.

[Example 3]
In Example 3, in the electroacoustic transducer of Example 1, the contour shape of each individual frame was changed as shown in FIG.

  As shown in FIG. 10, the electroacoustic transducer of this embodiment includes six transducers 10-1 to 10-6 and a frame 20. Here, the internal area of the frame surrounding the transducer 10-1 is four times the internal area of the frame surrounding the other transducer. That is, when the frame surrounding the other transducer is one cell, the frame surrounding the transducer 10-1 is four cells. However, actually, it is not limited to these examples.

〔result〕
Sound pressure level (1 kHz): 106 dB
Sound pressure level (3 kHz): 97 dB
Sound pressure level (5 kHz): 108 dB
Sound pressure level (10 kHz): 110 dB
Sound pressure level frequency characteristics flatness: ○
Drop impact stability: ○

  As is clear from the above results, according to the electroacoustic transducer of the present embodiment, it has the same characteristics as in the first embodiment, and if the overall frame shape is constant, it is related to the individual frame shape. The sound pressure level frequency characteristic is flat.

[Example 4]
In Example 4, the elastic member was changed with respect to Example 1. A polyester film (PET film) was used as the elastic member.

〔result〕
Sound pressure level (1 kHz): 91 dB
Sound pressure level (3 kHz): 89 dB
Sound pressure level (5 kHz): 92 dB
Sound pressure level (10 kHz): 90 dB
Flatness of sound pressure level frequency characteristics: ○
Drop impact stability: ○

  As is clear from the above results, according to the electroacoustic transducer of this example, the sound pressure level is equal to that of Example 1 and the sound pressure level frequency characteristic is flat regardless of the material of the elastic member. is there. That is, if the material of the elastic member is a polyester film (PET film), the sound pressure level frequency characteristics are not impaired.

[Example 5]
In Example 5, the elastic member was changed with respect to Example 1. Polyvinylidene fluoride (PVDF) was used as the piezoelectric material.

〔result〕
Sound pressure level (1 kHz): 82 dB
Sound pressure level (3 kHz): 84 dB
Sound pressure level (5 kHz): 87 dB
Sound pressure level (10 kHz): 91 dB
Flatness of sound pressure level frequency characteristics: ○
Drop impact stability: ○

  As is clear from the above results, according to the electroacoustic transducer of this example, the sound pressure level is the same as that of Example 1 regardless of the material of the piezoelectric material, and the sound pressure level frequency characteristic is flat. is there. That is, if the material of the elastic member is polyvinylidene fluoride (PVDF), the sound pressure level frequency characteristics are not impaired.

[Example 6]
As Example 6, a mobile phone as shown in FIG. 11 was prepared, and the electroacoustic transducer of Example 1 was mounted in this casing. Specifically, an electroacoustic transducer is attached to the inner surface of the casing of the mobile phone.

(Evaluation)
The sound pressure level and frequency characteristics were measured with a microphone placed 10 cm away from the element. A drop impact test was also conducted.

〔result〕
Sound pressure level (1 kHz): 83 dB
Sound pressure level (3 kHz): 85 dB
Sound pressure level (5 kHz): 87 dB
Sound pressure level (10 kHz): 80 dB
Drop impact test: No cracks were observed in the piezoelectric element even after 5 drops, and the sound pressure level (1 kHz) measured after the test was 84 dB.
Flatness of sound pressure level frequency characteristics: ○

[Example 7]
As Example 7, a mobile phone as shown in FIG. 11 was prepared, and the electroacoustic transducer of Example 2 was mounted in this casing. Specifically, an electroacoustic transducer is attached to the inner surface of the casing of the mobile phone.

(Evaluation)
The sound pressure level and frequency characteristics were measured with a microphone placed 10 cm away from the element. A drop impact test was also conducted.

〔result〕
Sound pressure level (1 kHz): 80 dB
Sound pressure level (3 kHz): 79 dB
Sound pressure level (5 kHz): 81 dB
Sound pressure level (10 kHz): 81 dB
Drop impact test: No cracks were observed in the piezoelectric element even after 5 drops, and the sound pressure level (1 kHz) measured after the test was 78 dB.
Flatness of sound pressure level frequency characteristics: ○

[Industrial application fields]
The present invention proposes an electroacoustic transducer suitable for electronic equipment such as a mobile phone and capable of reproducing a small and high-quality sound. Accordingly, the fields in which the present invention can be used include general electronic devices such as electroacoustic transducers and mobile phones. However, actually, it is not limited to these examples.

  Examples of portable electronic devices include car navigation systems (car navigation systems), portable game consoles, portable audio players, IC recorders, headphones, speakers, or audio in addition to mobile phones and laptop personal computers (PCs). A gadget or the like having a function of performing output can be considered. Further, the electronic device may be one that is mounted on a moving body such as a vehicle, a ship, or an aircraft. However, actually, it is not limited to these examples.

  Note that the electronic device is not limited to a portable type. This is because there is a demand for downsizing and higher sound quality even in the fixed type.

  According to the present invention, a basic structure of an electroacoustic transducer capable of reproducing high-quality sound is provided. Moreover, the electronic device carrying the said electroacoustic transducer is provided.

<Summary>
As described above, the present invention relates to an electroacoustic transducer used in an electronic device such as a mobile phone. An electroacoustic transducer capable of reproducing a large sound volume and good sound pressure level frequency characteristics while being small in size is provided.

  The electroacoustic transducer of the present invention is characterized in that a plurality of diaphragms are formed on an array. That is, it is characterized in that a plurality of diaphragms having different fundamental resonance frequencies are individually driven to restore the peaks and valleys of acoustic characteristics.

  According to this configuration, since the piezoelectric source or MEMS (micro electro mechanical system) is used as the drive source, the electroacoustic transducer can be reduced in size. In addition, since it is configured by forming a plurality of vibrators with various shapes and different fundamental resonance frequencies on the array, by controlling the phase of vibration of each vibrator, it corrects the peaks and valleys of the acoustic characteristics. Acoustic characteristics can be realized.

  For example, when there is a sound pressure peak at a frequency of 5 kHz, by inputting an electric signal that is in reverse phase to the electroacoustic transducer into a vibrator having a basic resonance frequency in the vicinity of 5 kHz, the interference of normal and reverse phase sound waves Due to the canceling effect of, the sound pressure peak is attenuated and the acoustic characteristics can be leveled.

  In addition, regarding the acoustic valley, the sound pressure level can be amplified by the interference of sound waves by inputting an acoustic signal having a positive phase to the electroacoustic transducer. In addition, since sound waves are generated from a plurality of transducers, the directivity can be controlled by changing the deflection angle of the plane of vibration radiation.

  In particular, in a high frequency band where the straightness of sound waves is high, narrow directivity characteristics are obtained, and the acoustic characteristics at the viewing position are different, which is problematic in terms of convenience for the user. According to this structure, since the radiation direction of a sound wave can be designed freely, a wide directivity electroacoustic transducer can be obtained.

  As described above, according to the present invention, it is possible to realize a small and high-quality electroacoustic transducer.

<Appendix>
Part or all of the above-described embodiments can be described as in the following supplementary notes. However, actually, it is not limited to the following description examples.

(Appendix 1)
The electroacoustic transducer of the present invention is an electroacoustic transducer having a plurality of transducers, wherein each of the plurality of transducers is arranged on an array.

(Appendix 2)
Each of the plurality of vibrators has a different fundamental resonance frequency.

(Appendix 3)
Each of the plurality of vibrators is driven at an arbitrary timing.

(Appendix 4)
The plurality of vibrators are formed by MEMS (micro electro mechanical system), and the driving method of the plurality of vibrators is any one of a piezoelectric method, an electrostatic method, an electromagnetic method, and a heat conduction method. It is characterized by.

(Appendix 5)
The driving frequency of the plurality of vibrators is 10 kHz or more.

(Appendix 6)
An electronic apparatus comprising the electroacoustic transducer according to any one of appendix 1 to appendix 5.

  As mentioned above, although embodiment of this invention was explained in full detail, actually, it is not restricted to said embodiment, Even if there is a change of the range which does not deviate from the summary of this invention, it is included in this invention.

10 (-i, i = 1 to n) ... vibrator 11 ... piezoelectric element 111 ... upper electrode layer 112 ... piezoelectric ceramic 113 ... lower electrode layer 12 ... elastic member 20 ... frame 30 ... MEMS actuator 31 ... upper movable electrode layer 32 ... Piezoelectric thin film layer (dielectric band layer)
33 ... Lower movable electrode layer 41 ... Vibration membrane 42 ... Voice coil 43 ... Frame 44 ... Pole piece (iron core)
45 ... Permanent magnet 46 ... Permanent magnet (magnetic pole)
47 ... York

Claims (5)

An electroacoustic transducer used in electronic equipment,
A plurality of transducers arranged on the array;
A frame surrounding the plurality of vibrators,
The contour shape of the frame surrounding all of the plurality of vibrators is constant,
The contour shape of the individual frame surrounding each of the plurality of vibrators can be changed,
The transducers are electroacoustic transducers having different shapes, being driven at arbitrary timings, and having different fundamental resonance frequencies. The electroacoustic transducer according to claim 1,
Each transducer is
A piezoelectric element;
An elastic member,
The flattening of the sound pressure level frequency characteristics of each vibrator is performed by changing at least one of the shape and thickness of the piezoelectric element and the shape and material of the elastic member, and the basic resonance frequency of each vibrator. Electroacoustic transducer realized by adjusting The electroacoustic transducer according to claim 2,
Each transducer is
Further comprising an adhesive for joining the piezoelectric element and the elastic member;
The electroacoustic transducer, wherein the adhesive has a thickness of 10 μm or more and 100 μm or less. The electroacoustic transducer according to any one of claims 1 to 3,
Each of the vibrators is formed by MEMS (micro electro mechanical system),
The driving method of each vibrator is any one of a piezoelectric method, an electrostatic method, an electromagnetic method, and a heat conduction method,
The electroacoustic transducer in which the drive frequency of each vibrator is 10 kHz or more.   The electronic device carrying the electroacoustic transducer as described in any one of Claims 1 thru | or 4.

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