JP6514079B2 - Sound generator - Google Patents

Description

  The present invention relates to, for example, a sound generator that is attached to a diaphragm to make a sound.

  There is known a piezoelectric actuator in which a laminated piezoelectric element is accommodated in a cylindrical case having a diaphragm at an end face and the diaphragm is vibrated by driving the laminated piezoelectric element (see, for example, Patent Document 1). It is also known to use an actuator as a sound generator.

Japanese Patent Application Publication No. 06-283778

  Here, in order to make the sound generator waterproof and dustproof, it is required to maintain the airtightness of the space inside the case. For example, the outer periphery of the diaphragm on the end face of the cylindrical case with a resin adhesive. A method is conceivable in which the parts are bonded all around.

  However, in the all-around bonding with a resin adhesive, since the Young's modulus of the resin adhesive is small, the sound in the middle and high frequency region is attenuated, and there is a problem that the sound pressure level may be lowered.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sound generator having a large sound pressure level in the middle and high frequency regions and an excellent sound quality.

The sound generator according to the present invention comprises a cylindrical case having an outer peripheral portion of a bottom plate attached to an end face, and a laminated piezoelectric element housed in the case and pressing the bottom plate, the outer periphery of the bottom plate The part is fixed to the end face of the case with double-sided tape and fixed with a plurality of screws, and the tightening torque by at least one of the plurality of screws is different from the tightening torque by the other screws It is characterized by

  According to the sound generator of the present invention, the sound pressure level in the middle and high frequency regions can be improved, and the sound quality can be made excellent.

(A) is a partially transparent schematic perspective view showing an example of the sound generator according to the present embodiment, (b) is a schematic vertical sectional view of the sound generator shown in (a), (c) is shown in (b) It is a bottom view of a sound generator. It is a schematic perspective view of the lamination type piezoelectric element shown in FIG. (A) is a schematic longitudinal cross-sectional view which shows the other example of the sound generator which concerns on this embodiment, (b) is a bottom view of the sound generator shown to (a). It is a bottom view which shows the other example of the sound generator which concerns on this embodiment. It is a schematic longitudinal cross-sectional view which shows an example of the speaker using the sound generator which concerns on this embodiment.

  Hereinafter, an example of a sound generator according to the present embodiment will be described in detail with reference to the drawings. Note that the present invention is not limited by the embodiments described below.

  FIG. 1 (a) is a partially transparent schematic perspective view showing an example of the sound generator according to this embodiment, FIG. 1 (b) is a schematic longitudinal sectional view of the sound generator shown in FIG. 1 (a), FIG. ) Is a bottom view of the sound generator shown in FIG. As shown in FIG. 1, the sound generator 1 of this embodiment includes a cylindrical case 21 formed by attaching the outer peripheral portion of the bottom plate 22 to the end face, and a laminated piezoelectric that is housed in the case 21 and presses the bottom plate 22. The outer peripheral portion of the bottom plate 22 is fixed to the end face of the case 21 with a double-sided tape 23 and fixed with a plurality of screws 24.

  Here, the cylindrical case 21 has a top plate portion 212 at one end (upper end) of a cylindrical cylindrical portion 211 extending in the vertical direction, and the other end (lower end) is open. It is cylindrical and has an internal space in which at least the laminated piezoelectric element 3 is accommodated. The case 21 is preferably small in deformation so as to sufficiently transmit the driving force of the laminated piezoelectric element 3 described later to the bottom plate 22. For example, metals such as stainless steel, aluminum and brass, ABS resin, polyacetal, polypropylene, It is formed of a resin such as polytetrafluoroethylene. The thickness of the cylindrical portion 211 and the top plate portion 212 is set to, for example, 2.5 mm to 10 mm. As a cross-sectional shape when the cylindrical part 211 is cut | disconnected in parallel with respect to the top-plate part 212 and a shape of the top-plate part 212, circular, an ellipse, a polygon etc. are mentioned, for example. For example, in the case of a circular shape, the force is transmitted approximately equally to the outer edge of the bottom plate 22 described later to vibrate, so that the disturbance of the frequency of the generated vibration can be reduced. Further, the outer periphery and the inner periphery may have different shapes, such as an outer periphery having a polygonal shape and an inner periphery of a space for accommodating the laminated piezoelectric element 2 having a circular shape.

  The length of the cylindrical portion 211 is set to, for example, 5 mm to 55 mm. Moreover, the internal diameter of the cylindrical part 211 in case the cylindrical part 211 is cylindrical is set to 30 mm-50 mm, for example. Here, the reason why the inner diameter of the cylindrical portion 211 is considerably larger than the width (for example, 2 mm to 3 mm) of the laminated piezoelectric element 3 described later is that the area of the bottom plate 22 is enlarged to make the sound in the low frequency band. It is to raise the pressure.

  Although not shown, the cylindrical portion 211 or the top plate portion 212 constituting the case 21 is provided with a hole through which a lead member for connecting the laminated piezoelectric element 3 to an external circuit.

  In addition, the cylindrical portion 211 or the top plate 212 may be deformed within a range in which the deformation of the bottom plate 22 is sufficiently small without interfering with the vibration of the bottom plate 22 described later. For example, the thickness of the top plate portion 212 is thinner than the thickness of the cylindrical portion 211, the cylindrical portion 211 is formed in a bellows shape (corrugated shape), or at least a part of the cylindrical portion 211 is in a spring shape. It may be

  The outer peripheral portion of the bottom plate 22 is attached to the open end face of the cylindrical portion 211 constituting the cylindrical case 21. The bottom plate 22 is a member for receiving the vibration corresponding to the sound wave form of the laminated piezoelectric element 3 and transmitting the vibration to the diaphragm on which the sound generator 1 is installed, according to the shape of the end face of the cylindrical portion 211 For example, it is formed in a circle, an ellipse or a polygon. The bottom plate 22 is made of the same material as that of the case 21 and is made of, for example, a metal such as stainless steel, aluminum or brass, a resin such as an ABS resin, polyacetal, polypropylene or polytetrafluoroethylene. The bottom plate 22 is more easily deformed than the top plate portion 212, and is set to, for example, 50% or less of the thickness of the top plate portion 212, and is set to, for example, 0.5 mm to 2 mm.

The case 21 and the bottom plate 22 are manufactured by casting in the case of metal, injection molding in the case of resin, or the like besides cutting.

  The laminated piezoelectric element 3 is accommodated in the case 21 so as to press and vibrate the bottom plate 22. The laminated piezoelectric element 3 is a member for receiving a voltage waveform corresponding to a sound waveform and generating a vibration corresponding to a sound waveform, and is disposed between the top plate portion 211 and the bottom plate 22 to vibrate the bottom plate 22 Let More specifically, in the laminated piezoelectric element 3, the direction perpendicular to the main surface of the bottom plate 22 (vertical direction in the drawing) and the laminating direction of the laminated piezoelectric element 3 described later are in the same direction. It is housed inside. By arranging in this manner, the sound generator 1 using the so-called d33 mode can be obtained, the generation force of the laminated piezoelectric element 3 is large, and the bottom plate 22 and the diaphragm on which the bottom plate 22 is attached are largely deformed. Sound pressure level can be improved.

  As shown in FIG. 2, for example, the multilayer piezoelectric element 3 is attached to the side surface of the multilayer body 33 and the multilayer body 33 in which the piezoelectric layers 31 and the internal electrode layers 32 are alternately stacked. An external electrode layer 34 electrically connected to an end of the internal electrode layer 32 led to one side, and an external electrode plate joined by a conductive bonding material (not shown) along the external electrode layer 34 It has 35 and.

  The laminated body 33 is formed into a square pole shape of, for example, 0.5 to 10 mm in length, 0.5 to 10 mm in width, and 1 to 50 mm in height by alternately laminating the piezoelectric layers 31 and the internal electrode layers 32. The end portions of the internal electrode layers 32 are alternately led to the opposite side surfaces of the laminate 33 which are opposite to each other. The shape of the laminate 33 is not particularly limited.

The piezoelectric layer 31 is formed of a ceramic having piezoelectric characteristics, and as such a ceramic, for example, a perovskite oxide made of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ), lithium niobate (LiNbO ₃₎ And lithium tantalate (LiTaO ₃ ) can be used.

  The internal electrode layer 32 is formed by co-firing with the ceramic forming the piezoelectric layer 31, and as the forming material, for example, a conductor mainly composed of a silver-palladium alloy that can be fired at low temperature, or copper, platinum It is possible to use a conductor including

  The external electrode layer 34 is made of, for example, silver and glass, and is attached to the side surface of the laminate 33 long in the laminating direction. The external electrode layer 34 is electrically connected to the derived end of the internal electrode layer 32.

  The outer electrode plate 35 is provided along the outer electrode layer 34, and is bonded by a conductive bonding material. A lead member (not shown) is joined to the external electrode plate 35 and connected to an external circuit. The external electrode plate 35 is made of, for example, a metal plate such as stainless steel, and slits or holes may be formed in the width direction. The conductive bonding material is, for example, one in which a filler such as silver is dispersed almost uniformly in a thermosetting resin such as a polyimide resin.

  The configuration of the laminated piezoelectric element 3 is not particularly limited. For example, the external electrode plate 35 may not be joined.

The first end face (the lower end face shown in the figure) of the laminated piezoelectric element 3 is in contact with the bottom plate 22, and the second end face (the face facing the first end face in the laminated piezoelectric element 3 in FIG. 1) The upper surface is in contact with the top plate portion 212 of the case 21. The bottom plate 22 after assembly has the role of holding the laminated piezoelectric element 3 in addition to the function of transmitting the vibration of the laminated piezoelectric element 3 to the diaphragm 4. For example, the amount of deflection of the bottom plate 22 at the time of holding the laminated piezoelectric element 3 is set to be in the range of 1 mm to the outside of the case 21.

  Here, the first end face of the laminated piezoelectric element 3 may be adhered to the bottom plate 22 with an adhesive or the like, and the second end face of the laminated piezoelectric element 3 may be adhered to the top plate portion 212 of the case 21. It may be bonded with In addition, for example, a projection is provided on the cylindrical portion 211 so as to limit the displacement or inclining of the laminated piezoelectric element 3 in the in-plane direction of the top plate portion 212 and the bottom plate 22 without bonding using an adhesive. Alternatively, a spacer may be interposed between the cylindrical portion 211 and the laminated piezoelectric element 3. The bottom plate 22 and the laminated piezoelectric element 3 may not be in direct contact, and an elastic member such as, for example, a coil spring may be interposed therebetween. Similarly, the top plate portion 212 and the laminated piezoelectric element 3 may not be in direct contact with each other, and an intermediate member may be provided therebetween.

  The outer peripheral portion of the bottom plate 22 is fixed to the end face of the case 21 by a double-sided tape 23 and fixed by a plurality of screws 24.

  The double-sided tape 23 has a configuration including, for example, a polyethylene-based or acrylic-based substrate layer and a pressure-sensitive adhesive layer made of, for example, an acrylic pressure-sensitive adhesive, and is provided over the entire circumference to obtain internal tightness. ing. The double-sided tape 23 can be used more preferably than a resin adhesive in that the thickness and width can be kept constant. In particular, the double-sided tape 23 preferably has high sealing properties and waterproofness. The thickness of the double-sided tape 23 is, for example, 0.15 mm to 2 mm, and the width of the double-sided tape 23 is, for example, within ± 50% of the width of the end face of the case 21 (cylindrical portion 211).

  Further, the plurality of screws 24 are inserted into several places on the outer peripheral portion of the bottom plate 22 and are partially fixed firmly. The plurality of screws 24 are made of a material having a high Young's modulus, for example, a metal such as steel, stainless steel, aluminum alloy, brass or the like, and a size of, for example, M1.6 to M6 can be used. Although it depends on the length in the circumferential direction of the case 21 (cylindrical portion 211), the plurality of screws 24 are provided, for example, 2 to 8 and are provided at intervals of 45 to 180 in the circumferential direction, for example. Preferably, three to five screws 24 are provided at intervals of 72 to 120 degrees.

  If the fixing is performed only by the double-sided tape 23, the sound in the middle and high frequency regions is attenuated, and the sound pressure level may be lowered. On the other hand, if it is fixed firmly by any means other than double-sided tape 23 (for example, welding) over the entire circumference, resonance of case 21 and bottom plate 22 will overlap and the level of peak dip in medium and high frequency region will increase, and sound quality may deteriorate. There is.

  On the other hand, the airtightness of the sound generator 1 is maintained by the double-sided tape 23 provided over the entire circumference, and the case 21 and the bottom plate 22 are made partially rigid by a plurality of partially provided screws 24. By fixing, the propagation of vibration in the middle and high frequency region is improved, the sound pressure level in the middle and high frequency region can be improved, and the sound quality can be made excellent.

  Here, the tightening torque by at least one screw 24 of the plurality of screws 24 may be different from the tightening torque by the other screws 24. The tightening torque is determined by, for example, the size (nominal diameter) of the screw 24, the effective cross-sectional area, the torque coefficient, etc. The tightening torque can be made different by making these values different. The tightening torque can be measured by the return torque method or the retightening torque method.

According to such a configuration, the tension applied to the bottom plate 22 can be made different depending on the place, and the bottom plate 22 vibrates nonuniformly, so that it is difficult to resonate and the peak dip can be reduced. In addition, for example, the screw 24 of M3 size is 0 ° on the circumference
If two screws are provided at the position of 180 ° and 180 °, for example, tighten one screw 24 to 0.5 to 1.0 N · m and the other screw 24 to 1.1 to 3.0 N · m. It can be made different by setting. Also, in the case where three or more screws 24 are provided, the tightening torque of only one screw 24 may be different from the tightening torque of the other screws 24. More preferably, the tightening torques are different. It becomes difficult to resonate and the peak dip can be reduced.

  Fig.3 (a) is a schematic longitudinal cross-sectional view which shows the other example of the sound generator which concerns on this embodiment, FIG.3 (b) is a bottom view of the sound generator shown to Fig.3 (a). As shown in FIG. 3, the diameter of at least one of the plurality of screws 24 may be different from the diameter of the other screws 24. If the diameter (nominal diameter) of the screw 24 is different, the force by which the screw 24 pushes the bottom plate 22 will be different, so even with such a configuration, the tension applied to the bottom plate 22 can be made different depending on the location. Since it vibrates unevenly, it can adjust easily and can make peak dip small. For example, when two screws 24 are provided at the 0 ° position and the 180 ° position on the circumference, for example, one screw 24 has a size of M1.6 to 4 for example. , And the other screw 24 is set to the size of M3-6. When three or more screws 24 are provided, the diameter of only one screw 24 may be made different from the diameter of the other screw 24. More preferably, resonance is more difficult by making the diameters different. Peak dip can be reduced.

  FIG. 4 is a schematic longitudinal sectional view showing another example of the sound generator according to the present embodiment. As shown in FIG. 4, at least one of the intervals of the plurality of screws 24 in the circumferential direction may be different from the other intervals. Even in a configuration in which at least one of the intervals of the plurality of screws 24 is different from the other intervals, the base plate 22 has a portion to which the base plate 22 is firmly fixed unevenly, so that the base plate 22 vibrates unevenly. Therefore, it becomes difficult to resonate and the peak dip can be reduced. In the example shown in FIG. 5, three screws 24 are provided, and the distance between these three screws 24 is 60 °, 150 °, and 150 °. As in this example, in the case of three screws 24, one interval may be different from the other two intervals, but for example, all the intervals are different from each other within the range of 30 to 180 °. It is also good.

  The sound generator 1 described so far is, as shown in FIG. 5, a speaker for affixing the bottom plate 22 of the sound generator 1 to the external diaphragm 4 and vibrating the diaphragm 4 by driving the laminated piezoelectric element 3. It can be done. In addition, FIG. 5 is a schematic longitudinal cross-sectional view which shows an example of the speaker using the sound generator 1 which concerns on this embodiment. This speaker generates a vibration by the sound generator 1 and thereby generates a sound by vibrating the diaphragm 4 as an installation object. As the diaphragm 4, one made of gypsum board can be adopted.

  Specifically, the electric signal amplified by the amplifier is input to the laminated piezoelectric element 3 constituting the sound generator 1, and the diaphragm 4 vibrates. For example, an electrical signal of about 1 V is amplified to about ± 50 V and input.

  The sound generator 1 is attached to the diaphragm 4 using, for example, an adhesive or a double-sided tape. For example, the top plate or wall of the indoor equipment can be used as the diaphragm 4, and the sound generator 1 is installed on these, and the sound generator 1 vibrates the entire installed top plate or wall. Sounds and music can be generated from the roof and walls. The top plate and the wall may be gypsum board, acrylic resin, construction wood, etc., as long as they have a desired thickness to function as an acoustic generator.

  Hereinafter, specific examples of the sound generator will be described.

First, a laminate is prepared by laminating a piezoelectric layer made of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ) and an internal electrode layer made of silver palladium as a laminate type piezoelectric element, and the longitudinal direction is made by grinding. It produced in square pole shape of 2 mm, width 2 mm, and length 25 mm.

  The case is made of SUS304 and has a cylindrical shape with an outer diameter of 50 mm and a height of 30 mm. The case has a hollowed inside by cutting. The diameter of the hollowed part (internal space) is 35 mm, depth is It was 25 mm. The thickness of the top plate was 5 mm, and the thickness of the cylindrical portion was 7.5 mm.

  The bottom plate was similarly made of SUS304, and had a disk shape with an outer diameter of 50 mm and a thickness of 1 mm.

  Using these, the sound generator used as five types of samples was produced.

  Specifically, as a comparative example, the outer periphery of the bottom plate was fixed to the end face of the case with the epoxy adhesive over the entire circumference, and a sound generator (sample 1) was produced.

  In addition, as an example, the end face of the case is a double-sided tape all around the outer periphery of the bottom plate, specifically, an acrylic that is excellent in weather resistance and chemical resistance on both sides of a flexible, tough acrylic foam substrate. A sound generator as shown in FIG. 1 is fixed with two screws with a thickness of 0.6 mm provided with a pressure-sensitive adhesive layer, and at two locations of the outer peripheral part of the bottom plate with two screws at 180 ° intervals. (Sample 2) was produced. Here, the two screws were of size M3 and screwing was performed at a tightening torque of 0.74 N · m.

  Moreover, as an example, while fixing the outer peripheral part of the bottom plate with a double-sided tape over the entire circumference like the sound generator of sample 2, two screws of size M3 are used, and the tightening torque by the screw is 1.99 N · m An acoustic generator (sample 3) was manufactured by firmly fixing two places of the outer peripheral portion of the bottom plate at 180 ° intervals. Here, one tightening torque was 0.67 N · m, and the other tightening torque was 1.99 N · m.

  Also, as an example, similarly, while fixing the outer peripheral portion of the bottom plate with double-sided tape all around, prepare three screws, two of size M3 and one of size M5. The two points of the above were firmly fixed at 120 ° intervals to produce an acoustic generator (sample 4) as shown in FIG.

  Also, as an example, similarly, while fixing the outer peripheral portion of the bottom plate with a double-sided tape over the entire circumference, three screws of size M3 are prepared, and the intervals of the plurality of screws in the circumferential direction are 144 °, 144 °, 72 The sound generator (sample 5) as shown in FIG. 4 was manufactured by firmly fixing one interval to another so as to be different from the other intervals.

  These sound generators were placed on a plaster board of 1600 mm × 900 mm and a thickness of 10 mm to form a speaker, which was attached with double-sided tape. Sound pressure characteristics were evaluated.

  The driving conditions were sine sweep, with an amplitude of ± 15 V, and the frequency was continuously changed from 100 Hz to 20 kHz. At the time of measurement, a microphone was placed under 1 m in an anechoic chamber to collect sound. The collected data were converted to sound pressure level values for each frequency and compared.

As a result of the measurement, the average sound pressure level at all frequencies (100 Hz to 20 kHz) is 67 dB for sample 1, 72 dB for sample 2, 75 dB for sample 3, 75 dB for sample 4, 75 dB for sample 5, and double-sided tape and screw The sound pressure level at medium and high frequencies was improved by fixing the bottom plate.

  The sound pressure level difference between the peak and the dip seen around 5 kHz to 10 kHz, which is the high frequency band, is 14 dB for sample 2, 10 dB for sample 3, 10 dB for sample 4 and 8 dB for sample 5, screw tightening torque It has been confirmed that the screw diameter and the spacing can be reduced.

DESCRIPTION OF SYMBOLS 1 sound generator 21 case 211 cylindrical part 212 top plate part 22 bottom plate 23 double-sided tape 24 screw 3 laminated piezoelectric element 31 piezoelectric layer 32 internal electrode layer 33 laminated body 34 external electrode layer 35 external electrode plate 4 diaphragm

Claims (3)

A cylindrical case formed by attaching an outer peripheral portion of a bottom plate to an end face, and a laminated piezoelectric element accommodated in the case and pressing the bottom plate, the outer peripheral portion of the bottom plate is an end face of the case Sound generation characterized in that it is fixed with double-sided tape and fixed with a plurality of screws, and the tightening torque by at least one of the plurality of screws is different from the tightening torque by the other screws vessel. The sound generator according to claim 1 , wherein a diameter of at least one screw of the plurality of screws is different from a diameter of another screw. The sound generator according to claim 1 or 2 , wherein at least one of the intervals of the plurality of screws in the circumferential direction is different from the other intervals.

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