JP6386925B2 - SOUND GENERATOR AND ELECTRONIC DEVICE USING THE SAME - Google Patents

Description

  The present invention relates to an acoustic generator and an electronic device using the same.

  Conventionally, a speaker in which a piezoelectric element is attached to a diaphragm is known (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 2004-23436

  However, the above-described conventional speaker has a problem that it is difficult to increase the sound pressure particularly in a low frequency region. In addition, as a conventional sound generator that generates low-frequency sound, a super woofer including a large electromagnetic speaker and a large resonance box is known, but it is difficult to downsize (particularly thin). was there.

  The present invention has been devised in view of such problems in the prior art, and an object of the present invention is to provide a thin acoustic generator capable of generating sound with a high sound pressure at a low frequency, and the use thereof. Is to provide the electronic equipment that was.

The acoustic generator of the present invention has a frame member, a first surface and a second surface located on the opposite side thereof, and is arranged on the inner side of the frame member at a distance from the frame member. A plate, a piezoelectric element provided on the first surface of the diaphragm, and the frame member disposed so as to close a gap between the frame member and the diaphragm, so that the diaphragm can vibrate More elastic than the material constituting the diaphragm , partially provided on the second surface of the diaphragm so that at least a portion thereof overlaps the piezoelectric element when viewed in plan A plate-like reinforcing member made of a material having a high rate, and the piezoelectric element has a shape having a length direction and a width direction, and the length direction of the piezoelectric element is Assuming the first direction, the length of the reinforcing member in the first direction is the length of the piezoelectric element. Shorter than the length in the first direction, the connecting member is made of a material having a smaller elastic modulus than the material constituting the frame member and the material constituting the diaphragm, and has an annular flat shape, It is joined to the peripheral portion of the second surface of the diaphragm .

  The electronic device of the present invention includes at least one speaker and an electronic circuit connected to the speaker, and the speaker is configured using the acoustic generator.

  The sound generator of the present invention is thin and can generate sound with high sound pressure at a low frequency. The electronic device of the present invention can generate sound with high sound pressure at a low frequency.

It is a perspective view showing typically the sound generator of a 1st embodiment of the present invention. It is the sectional view on the AB line in FIG. It is a top view showing typically the sound generator of a 1st embodiment of the present invention. It is a figure which shows the structure of the electronic device of 2nd Embodiment of this invention. It is a graph which shows the frequency characteristic of the sound pressure of the sound which the sound generator of 1st Embodiment of this invention generate | occur | produces.

  Hereinafter, an acoustic generator and an electronic apparatus using the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a perspective view schematically showing a sound generator according to a first embodiment of the present invention. 2 is a cross-sectional view taken along line AB in FIG. FIG. 3 is a plan view schematically showing the sound generator according to the first embodiment of the present invention. 3 shows a state viewed from the −z direction, and the piezoelectric element 15 disposed on the surface (surface 12a) on the + z direction side of the diaphragm 12 is indicated by a broken line. In order to facilitate understanding of the structure, FIG. 2 shows an enlarged view in the thickness direction of the sound generator (+ z direction in the figure). As shown in FIGS. 1 to 3, the acoustic generator of this embodiment includes a frame member 11, a diaphragm 12, a connection member 13, a piezoelectric element 15, and a reinforcing member 17.

  The frame member 11 has a plate shape and has a surface 11a and a surface 11b facing each other. The frame member 11 has a through hole 16 that penetrates from the surface 11b to the surface 11a. The material of the frame member 11 is not particularly limited, and various materials such as a metal material, a plastic material, and wood can be used, but it is desirable that the rigidity is higher than that of the diaphragm 12, for example, stainless steel. Can be suitably used. The thickness of the frame member 11 can be about 0.5 mm to 2 mm, for example. The outer shape of the frame member 11 is not limited to a rectangle, but may be another polygonal shape, or may be a circle or an ellipse.

  The diaphragm 12 has a plate shape and has a surface 12a (first surface) and a surface 12b (second surface) facing each other. The surface 12b is located on the −z direction side, and the surface 12a is located on the + z direction side. The diaphragm 12 has a shape smaller than the through hole 16 and is disposed in the through hole 16 (inside the frame member 11). The material of the diaphragm 12 is not particularly limited, and various materials such as a metal material, a plastic material, and wood can be used. However, since the material is preferably light and strong, for example, aluminum, magnesium, and Those alloys can be suitably used. The thickness of the diaphragm 12 can be about 0.05 mm to 0.5 mm, for example. It is desirable that the outer shape of the diaphragm 12 be elliptical, thereby suppressing unnecessary vibrations in the horizontal direction (direction parallel to the xy plane) of the diaphragm 12. Initially, the inventors considered a structure having a circular diaphragm 12, but in such a structure, unnecessary vibration in the horizontal direction (direction parallel to the xy plane) of the diaphragm 12 occurs at a specific frequency. As a result, it has become clear that the problem of noise generation occurs. As a result of various studies, it was found that unnecessary vibration in the horizontal direction (direction parallel to the xy plane) of the diaphragm 12 can be suppressed by making the diaphragm 12 into an elliptical shape. However, in some cases, the shape may not be elliptical, and may be circular or polygonal. The space | interval of the frame member 11 and the diaphragm 12 can be about 1 mm-5 mm, for example.

  The connection member 13 has a flat shape such as a film shape or a plate shape, and has an annular plane shape. The connecting member 13 has an annular surface 13a, and the outer peripheral edge portion of the surface 13a is entirely joined to the peripheral edge portion of the through hole 16 in the surface 11b of the frame member 11, and the surface 13a The inner peripheral edge is entirely joined to the peripheral edge of the surface 12 b of the diaphragm 12. In this way, the connection member 13 totally connects the peripheral portion of the through hole 16 on the surface 11 b of the frame member 11 and the peripheral portion of the surface 12 b of the diaphragm 12. For joining the frame member 11 and the diaphragm 12 and the connection member 13, various known joining members such as various adhesives can be used.

The connecting member 13 is desirably light, easily deformable, and strong. For this reason, the connection member 13 is more easily deformed than the material constituting the frame member 11 and the diaphragm 12, that is, the material having a smaller elastic modulus than the material constituting the frame member 11 and the material constituting the diaphragm 12. It is configured using. As a material of the connection member 13, for example, a resin material such as a silicone resin, or a rubber material such as urethane rubber, silicone rubber, or acrylic rubber can be used. In particular, porous rubber (foam rubber) formed using a rubber material such as urethane rubber, silicone rubber, polyethylene rubber, or the like can be suitably used. Among these, a silicone foam can be particularly preferably used. Moreover, the thickness of the connection member 13 can be about 0.1 mm-1 mm, for example.

  A piezoelectric element 15 is bonded to the center portion of the surface 12 a of the diaphragm 12 by a bonding member 19. The piezoelectric element 15 has a rectangular flat plate shape in which the length direction is the + x direction, the width direction is the + y direction, and the thickness direction is the + z direction. Although not shown in detail, the piezoelectric element 15 includes a laminate, a plurality of surface electrodes, and a plurality of side electrodes. The laminate is configured by alternately laminating piezoelectric layers made of piezoelectric ceramics and internal electrode layers in the + z direction. The plurality of surface electrodes are respectively disposed on the two surfaces of the laminate. The plurality of side electrodes are respectively provided on the surface in the length direction of the multilayer body. In addition, the surface electrode and the internal electrode layer are alternately drawn out to the surface in the length direction of the multilayer body, and are connected to the side electrodes, respectively. The piezoelectric layer and various electrodes constituting the piezoelectric element 15 can be configured using known materials.

  The piezoelectric element 15 is configured such that expansion and contraction are reversed in the + z direction and the −z direction at an arbitrary moment when an electric signal is input. Therefore, the piezoelectric element 15 is flexibly vibrated by receiving an electric signal. The piezoelectric element 15 and the diaphragm 12 are bonded to each other with a known adhesive such as an epoxy adhesive, a silicone adhesive, or a polyester adhesive, or a double-sided tape. Note that the piezoelectric element 15 may be a unimorph type vibration element configured by bonding a piezoelectric element that receives an electric signal to expand and contract and vibrates, and a metal plate. In addition, the piezoelectric element 15 may be a piezoelectric element that expands and contracts when an electric signal is input.

  The joining member 19 can be composed of various known joining members such as various adhesives. Since it is desirable to transmit the vibration of the piezoelectric element 15 to the diaphragm 12 without loss, it is desirable to form the bonding member 19 using a material having a large elastic modulus. For example, an epoxy adhesive is suitable for the bonding member 19.

A reinforcing member 17 is joined to the center portion of the surface 12 b of the diaphragm 12 by a joining member 18. The reinforcing member 17 has a plate shape, and the entire surface on the + z direction side is joined to the diaphragm 12 by the joining member 18. By providing the reinforcing member 17, it is possible to prevent the diaphragm 12 from vibrating specifically and greatly at a specific frequency while allowing normal vibration of the diaphragm 12 to generate noise. Initially, the inventors examined a structure in which the reinforcing member 17 is not present. However, in such a structure, the diaphragm 12 vibrates specifically and greatly at a specific frequency, thereby generating noise. It has become clear that it will occur. As a result of various investigations, the reinforcement member 17 is provided to prevent the diaphragm 12 from vibrating specifically at a specific frequency and preventing noise from occurring without disturbing the normal vibration of the diaphragm 12. It turns out that you can. The reinforcing member 17 is preferably disposed at the center of the diaphragm 12 so as to face the piezoelectric element 15 with the diaphragm 12 interposed therebetween. In addition, it is important that the length of the reinforcing member 17 is shorter than the length of the piezoelectric element 15. Thereby, the hindrance of the normal vibration of the diaphragm 12 can be reduced. In order to suppress vibration of the diaphragm 12 from being specifically large, it is desirable that the reinforcing member 17 is made of a material having a larger elastic modulus than the material constituting the diaphragm 12. In addition, the thickness of the reinforcing member 17 is preferably smaller than the thickness of the diaphragm 12 so as not to prevent normal vibration of the diaphragm 12. The reinforcing member 17 can be configured using a material having a large elastic modulus such as a metal material or a ceramic material. In particular, a ceramic material is suitable for the material of the reinforcing member 17. In particular, when the diaphragm 12 is made of a metal material and the reinforcing member 17 is made of a ceramic material, the diaphragm 12 can be efficiently excited by the piezoelectric element 15, and the reinforcing member 17, the abnormal vibration of the diaphragm 12 can be efficiently suppressed.

  The joining member 18 can be composed of various known joining members such as various adhesives. In order to enhance the effect of the reinforcing member 17 that allows the diaphragm 12 to normally vibrate at a specific frequency and inhibits the diaphragm 12 from vibrating significantly large at a specific frequency, a material having a low elastic modulus is used. It is desirable to constitute the joining member 18. Further, the joining member 18 is preferably configured using a material having a smaller elastic modulus than the material constituting the joining member 19. For example, an acrylic pressure-sensitive adhesive is suitable as the bonding member 18. For example, a double-sided tape in which an acrylic pressure-sensitive adhesive layer is disposed on both sides of the base layer is also suitable as the bonding member 18.

  In the sound generator of this embodiment having such a configuration, when an electric signal is input and the piezoelectric element 15 vibrates, the vibration plate 12 vibrates thereby, and sound is generated by the vibration of the vibration plate 12.

  The acoustic generator according to the present embodiment includes a frame member 11, a diaphragm 12, a piezoelectric element 15, a connection member 13, and a reinforcing member 17. The diaphragm 12 has a surface 12 a and a surface 12 b located on the opposite side, and is disposed inside the frame member 11 with a gap from the frame member 11. The piezoelectric element 15 is provided on the surface 12 a of the diaphragm 12. The connecting member 13 is disposed so as to close a gap between the frame member 11 and the diaphragm 12 and connects the diaphragm 12 to the frame member 11 so as to vibrate. The reinforcing member 17 is partially provided on the surface 12b of the diaphragm 12 so that at least a part thereof overlaps the piezoelectric element 15 when viewed in plan, and suppresses deformation of the diaphragm 12. With such a configuration, a thin acoustic generator can be obtained. Further, with such a configuration, vibration that causes the diaphragm 12 to be displaced in the + z direction and the −z direction as a whole also occurs, so that sound with a high sound pressure at a low frequency can be generated. In addition, it is possible to suppress the vibration of the diaphragm 12 at a specific frequency and thereby generating noise.

  In the acoustic generator of the present embodiment, the piezoelectric element 15 and the reinforcing member 17 are provided at the center of the diaphragm 12. Thereby, the piezoelectric element 15 can efficiently excite the diaphragm 12, and the effect of reducing abnormal vibration of the piezoelectric element 15 by the reinforcing member 17 can be enhanced. Note that “the piezoelectric element 15 is provided at the center of the diaphragm 12” means that the deviation between the center of gravity of the piezoelectric element 15 and the center of gravity of the diaphragm 12 when viewed in plan from the + z direction. It means that it arrange | positions so that it may be 10% or less of the length of the longest part. Further, “the reinforcing member 17 is provided at the center of the diaphragm 12” means that the deviation between the center of gravity of the reinforcing member 17 and the center of gravity of the diaphragm 12 when viewed in plan from the + z direction is the reinforcing member 17. It means that it arrange | positions so that it may be 10% or less of the length of the longest part.

  Further, in the acoustic generator of the present embodiment, the piezoelectric element 15 has a shape having a length direction and a width direction. When the length direction of the piezoelectric element 15 is the first direction (+ x direction), reinforcement is performed. The length of the member 17 in the first direction (+ x direction) is shorter than the length of the piezoelectric element 15 in the first direction (+ x direction). Thereby, it can suppress that the normal vibration of the diaphragm 12 is prevented by the reinforcing member 17.

In the acoustic generator of the present embodiment, the diaphragm 12 has an elliptical shape having a length direction and a width direction, and the length direction of the diaphragm 12 is the first direction (the piezoelectric element 15 of the piezoelectric element 15). This corresponds to the length direction and the + x direction in the figure). Thereby, the diaphragm 12 can be efficiently vibrated by the piezoelectric element 15, and the occurrence of unnecessary vibration in the horizontal direction (direction parallel to the xy plane) of the diaphragm 12 can be suppressed. The ellipse in this case means not only a mathematical ellipse (a set of points where the sum of distances from two fixed points is constant) but also an oval.

  In the present embodiment, the reinforcing member 17 and the diaphragm 12 are joined via the joining member 18, and the piezoelectric element 15 and the diaphragm 12 are joined via the joining member 19. At this time, it is desirable that the joining member 18 is configured using a material having a smaller elastic modulus than the material constituting the joining member 19. As a result, the vibration of the piezoelectric element 15 can be transmitted to the diaphragm 12 without loss, and the reinforcing member 17 allows the normal vibration of the diaphragm 12 to be allowed to be suppressed, while suppressing the specifically large vibration of the piezoelectric element 15. be able to.

  In the acoustic generator of this embodiment, the periphery of the frame member 11 is fixed to another object, and an electric signal is input to the piezoelectric element 15 so that both the frame member 11 and the diaphragm 12 vibrate. When sound is generated from both the frame member 11 and the diaphragm 12, the overall sound pressure can be further increased.

  The sound generator of this embodiment can be manufactured as follows, for example. First, a binder, a dispersant, a plasticizer, and a solvent are added to the powder of the piezoelectric material and stirred to prepare a slurry. As the piezoelectric material, any of lead-based and non-lead-based materials can be used. Next, the obtained slurry is formed into a sheet shape to produce a green sheet. A conductor paste is printed on the green sheet to form a conductor pattern to be an internal electrode, and the green sheet on which the conductor pattern is formed is laminated to produce a laminated molded body.

  Next, this laminated molded body is degreased, fired, and cut into a predetermined size to obtain a laminated body. And the outer peripheral part of a laminated body is processed as needed. Next, a conductor paste is printed on the surface of the laminate in the laminating direction to form a conductor pattern to be a surface electrode, and the conductor paste is printed on both sides in the length direction of the laminate to be a conductor to be a side electrode. Form a pattern. And the structure used as the piezoelectric element 15 can be obtained by baking an electrode at predetermined temperature. Thereafter, in order to impart piezoelectricity to the piezoelectric element 15, a DC voltage is applied through the surface electrode or the side electrode to polarize the piezoelectric layer of the piezoelectric element 15. In this way, the piezoelectric element 15 can be obtained.

  Next, the frame member 11, the diaphragm 12, the connection member 13, and the reinforcing member 17 processed into a predetermined shape are prepared, and the joint portions are joined together with the piezoelectric element 15 with an adhesive or the like. In this way, the sound generator of this embodiment can be obtained.

(Second Embodiment)
FIG. 4 is a diagram illustrating a configuration of an electronic device 50 according to the second embodiment of the present invention. As shown in FIG. 4, the electronic device 50 of the present embodiment includes a speaker 30, a housing 40, an electronic circuit 60, a key input unit 50c, a microphone input unit 50d, a display unit 50e, and an antenna 50f. have.

  The electronic circuit 60 includes a control circuit 50a and a communication circuit 50b. The electronic circuit 60 is connected to the speaker 30 and has a function of outputting an audio signal to the speaker 30. The control circuit 50 a is a control unit of the electronic device 50. The communication circuit 50b transmits and receives data through the antenna 50f based on the control of the control circuit 50a.

The key input unit 50c is an input device of the electronic device 50 and accepts a key input operation by an operator. The microphone input unit 50d is also an input device of the electronic device 50, and accepts a voice input operation by an operator. The display unit 50e is a display output device of the electronic device 50, and outputs display information based on the control of the control circuit 50a.

  The speaker 30 is configured by the sound generator of the first embodiment described above. The speaker 30 functions as a sound output device in the electronic device 50, and generates sound (including sound outside the audible frequency band) based on the sound signal input from the electronic circuit 60. Note that the speaker 30 is connected to the control circuit 50a of the electronic circuit 60, and generates a sound upon application of a voltage controlled by the control circuit 50a.

  The housing 40 has a function of accommodating and protecting the electronic circuit 60 and the like. The speaker 30, the key input unit 50c, the microphone input unit 50d, the display unit 50e, and the antenna 50f are attached and fixed to the housing 40. The housing 40 includes the speaker 30, the key input unit 50c, and the microphone input unit. 50d, functioning as a support member that supports the display unit 50e and the antenna 50f. In FIG. 4, the speaker 30, the electronic circuit 60, the key input unit 50 c, the microphone input unit 50 d, and the display unit 50 e are housed in the housing 40, but the present invention is not limited to this. It is not a thing. The speaker 30, the electronic circuit 60, the key input unit 50c, the microphone input unit 50d, the display unit 50e, and the like may be exposed on the surface of the electronic device 50. Such a casing 40 can be formed using various materials having rigidity sufficient to support the speaker 30 and the like, and can be formed using materials such as wood, synthetic resin, and metal, for example. .

  Since the electronic device 50 of the present embodiment generates sound using the speaker 30 configured by the sound generator of the first embodiment described above, the sound having a high sound pressure at a low frequency and a reduced noise. Can be generated.

  The electronic device 50 only needs to include at least the speaker 30 and the electronic circuit 60. The electronic device 50 does not have to include all of the speaker 30, the casing 40, the electronic circuit 60, the key input unit 50c, the microphone input unit 50d, the display unit 50e, and the antenna 50f. Other components may be included. The electronic circuit 60 is not limited to the electronic circuit 60 having the above-described configuration, and may be an electronic circuit having another configuration. The speaker 30 is not limited to the sound generator of the first embodiment described above, and may be another form of sound generator having the same configuration.

  Further, the electronic device on which the speaker 30 is mounted is not limited to a mobile terminal such as a mobile phone or a tablet terminal. In various electronic devices having a function of generating sound, the speaker 30 using the sound generator as in the first embodiment described above can be used as a sound generator. For example, in flat-screen TVs and car audio devices, of course, in the electronic devices such as vacuum cleaners, washing machines, refrigerators, and microwave ovens having a function of generating sound and sound, sound generation as in the first embodiment described above is possible. The speaker 30 composed of a container can be used as a sound generator.

  Next, a specific example of the sound generator of the present invention will be described. The acoustic generator according to the first embodiment of the present invention shown in FIGS. 1 to 3 was produced and its performance was evaluated.

The piezoelectric element 15 is a piezoelectric element in which a PZT-based piezoelectric layer and an electrode layer are stacked. The shape of the piezoelectric element 15 was a rectangular plate having a length of 110 mm, a width of 45 mm, and a thickness of 0.15 mm. The frame member 11 is made of stainless steel and has a plate shape having a length of 190 mm, a width of 190 mm, and a thickness of 1 mm. In addition, an elliptical through hole 16 having a major axis of 180 mm and a minor axis of 140 mm was formed in the center of the frame member 11. The diaphragm 12 was formed using aluminum, and was an elliptical plate having a major axis of 175 mm, a minor axis of 135 mm, and a thickness of 0.3 mm. The connection member 13 was formed using a silicone foam and was an elliptical ring having a thickness of 0.5 mm. The reinforcing member 17 is made of the same PZT type piezoelectric ceramic as that of the piezoelectric element 15 and has a rectangular plate shape having a length of 55 mm, a width of 45 mm, and a thickness of 0.15 mm. As the joining member 18, a double-sided tape in which an adhesive layer made of an acrylic adhesive was formed on both surfaces of a nonwoven fabric base material was used. As the joining member 19, an epoxy adhesive was used.

  The characteristics of the produced sound generator are shown in FIG. FIG. 5 is a graph showing a change in sound pressure depending on the frequency of sound generated from the sound generator. When a sine wave having an effective value of 7.0 V is applied to the sound generator, it is 1 m away from the sound generator. It shows the sound pressure of the place. In the graph shown in FIG. 5, the horizontal axis indicates the frequency, and the vertical axis indicates the sound pressure level. In the measurement, a baffle board for preventing sound from wrapping around from the back surface of the sound generator was attached to the periphery of the frame member 11 for measurement.

  According to the graph shown in FIG. 5, a high sound pressure of about 90 dB is obtained in a low frequency range of about 100 Hz, and the change in the sound pressure is small in the range of 100 Hz to 1000 Hz, resulting in high sound quality with little distortion. It can be seen that sound is generated and noise due to abnormal vibration is not generated. This result confirms the effectiveness of the present invention.

11: Frame member 12: Diaphragm 13: Connection member 11a, 11b, 12a, 12b, 13a: Surface 15: Piezoelectric element 16: Through hole 17: Reinforcing member 18, 19: Joining member 30: Speaker 50: Electronic device 60: Electronic circuit

Claims (8)

A frame member;
A diaphragm having a first surface and a second surface located on the opposite side of the first surface, and disposed inside the frame member at a distance from the frame member;
A piezoelectric element provided on the first surface of the diaphragm;
A connecting member that is disposed so as to close a gap between the frame member and the diaphragm, and that connects the diaphragm to the frame member so as to vibrate;
It is made of a material having a larger elastic modulus than the material constituting the diaphragm , which is partially provided on the second surface of the diaphragm so that at least a part thereof overlaps the piezoelectric element when seen in a plan view. A plate-shaped reinforcing member,
Equipped with a,
The piezoelectric element has a shape having a length direction and a width direction,
When the length direction of the piezoelectric element is a first direction, the length of the reinforcing member in the first direction is shorter than the length of the piezoelectric element in the first direction,
The connecting member is made of a material that forms the frame member and a material that has a smaller elastic modulus than the material that forms the diaphragm, has an annular flat shape, and is formed on the peripheral portion of the second surface of the diaphragm. A sound generator characterized by being joined .   The acoustic generator according to claim 1, wherein a thickness of the reinforcing member is smaller than a thickness of the diaphragm.   The frame member has a plate shape having a through hole,
The said connection member is joined to the inner peripheral part adjacent to the said through-hole among the surfaces of the said frame member facing the same side as the 2nd surface of the said diaphragm. The sound generator according to claim 2. The acoustic generator according to any one of claims 1 to 3, wherein the piezoelectric element and the reinforcing member are provided in a central portion of the diaphragm. The diaphragm has an elliptical shape with a length and width directions, claims 1 to said length direction of said diaphragm, characterized in that coincides with the first direction 4. The sound generator according to any one of 4 . The acoustic generator according to any one of claims 1 to 5, wherein the diaphragm is made of a metal material, and the reinforcing member is made of a ceramic material.   The reinforcing member and the diaphragm are joined via a first joining member, the piezoelectric element and the diaphragm are joined via a second joining member, and the first joining member is The sound generator according to any one of claims 1 to 6, wherein the sound generator is configured using a material having a smaller elastic modulus than a material constituting the second joining member.   It has at least 1 speaker and the electronic circuit connected to this speaker, The said speaker is comprised using the sound generator in any one of Claim 1 thru | or 7. Electronic equipment.