JP6346075B2 - Sound generator - Google Patents

Description

  The present invention relates to a sound generator that produces sound by being attached to a diaphragm, for example.

  For example, as a sound generator that produces sound by being attached to a diaphragm such as a panel, a piezoelectric element is attached to the diaphragm, and the piezoelectric element is driven to expand and contract mainly in a direction parallel to the diaphragm. An acoustic generator using a so-called d31 mode is known (see, for example, Patent Document 1).

  There is also known a piezoelectric actuator that includes a laminated piezoelectric element and expands and contracts mainly in the laminating direction (see, for example, Patent Document 2), and the piezoelectric actuator is attached to a diaphragm as an acoustic generator. A sound generator using a so-called d33 mode is conceivable in which the diaphragm is vibrated by being driven to extend and contract in a direction perpendicular to the diaphragm.

Special Table 2002-539699 Japanese Patent Laid-Open No. 06-283778

  Here, compared with the sound generator using the d31 mode, the sound generator using the d33 mode has a larger generation force of the piezoelectric element, and the sound pressure level can be improved.

  However, in the d33 mode, the sound pressure level in the low frequency band is lower than the sound pressure level in the middle frequency band and the high frequency band, and an improvement in the sound pressure level in the low frequency band is required.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an acoustic generator capable of improving the sound pressure level in the entire band including the low frequency band.

  The acoustic generator of the present invention includes a case main body having an opening and a case including a bottom plate provided so as to close the opening, and a stacked type housed in the case so as to vibrate the bottom plate of the case A piezoelectric element, and a spacer is interposed between the bottom plate and the laminated piezoelectric element, and an outer edge of a surface of the spacer that is in contact with the bottom plate when viewed from the lamination direction of the laminated piezoelectric element Is located outside the outer edge of the end face of the multilayer piezoelectric element.

  According to the acoustic generator of the present invention, the sound pressure level in the entire band including the low frequency band can be improved.

(A) is a schematic perspective transmission figure which shows an example of the sound generator of this embodiment, (b) is a schematic longitudinal cross-sectional view of the sound generator shown to (a). FIG. 2 is a schematic perspective view of the multilayer piezoelectric element shown in FIG. 1. It is a schematic longitudinal cross-sectional view which shows the other example of the acoustic generator of this embodiment. It is a schematic longitudinal cross-sectional view which shows the other example of the acoustic generator of this embodiment. It is a schematic longitudinal cross-sectional view which shows the other example of the acoustic generator of this embodiment. It is a schematic longitudinal cross-sectional view which shows the other example of the acoustic generator of this embodiment. It is a block diagram which shows an example of the sound generator using the sound generator of this embodiment.

  Hereinafter, the acoustic generator of the present embodiment will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

  FIG. 1A is a schematic perspective transparent view showing an example of the acoustic generator of the present embodiment, and FIG. 1B is a schematic longitudinal sectional view of the acoustic generator shown in FIG. The acoustic generator 1 of this embodiment shown in FIG. 1 vibrates the case 2 having a case main body 21 having an opening and a bottom plate 22 provided so as to close the opening, and the bottom plate 22 of the case 2. The multilayer piezoelectric element 3 housed in the case 2 is included, and a spacer 4 is interposed between the bottom plate 22 and the multilayer piezoelectric element 3, and the spacer 4 is viewed from the stacking direction of the multilayer piezoelectric element 3. The outer edge of the surface 41 in contact with the bottom plate is positioned outside the outer edge of the end surface (first end surface 30) of the multilayer piezoelectric element 3.

  The case body 21 shown in FIG. 1 has a top plate portion 212 at one end (upper end) of a cylindrical tube portion 211 extending in the vertical direction, and the other end (lower end) is open (a so-called bottomed tube). And has an internal space in which at least the multilayer piezoelectric element 3 and the spacer 4 are accommodated. The case body 21 (cylindrical portion 211 and top plate portion 212) is preferably one that is less deformed in order to sufficiently transmit the driving force of the laminated piezoelectric element 3 described later to the bottom plate 22, for example, stainless steel, aluminum, It is formed of a metal such as brass, a resin such as ABS resin, polyacetal, polypropylene, or polytetrafluoroethylene. The thickness of the cylindrical part 211 and the top-plate part 212 is set to 1 mm-20 mm, for example.

  Examples of the cross-sectional shape when the cylindrical portion 211 is cut in parallel to the top plate portion 212 and the shape of the top plate portion 212 include a circle, an ellipse, or a polygon. For example, in the case of a circular shape, a force is transmitted almost evenly to the outer edge of the bottom plate 22 to be described later to vibrate, so that the frequency disturbance of the generated vibration can be reduced.

  The length of the cylindrical portion 211 is set to, for example, 6 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 larger than the width (for example, 2 mm to 3 mm) of the laminated piezoelectric element 3 to be described later is to increase the sound pressure in the low frequency band by increasing the area of the bottom plate 22. It is.

  It should be noted that the cylindrical portion 211 or the top plate portion 212 may be deformed within a range that does not hinder the vibration of the bottom plate 22 to be described later and is sufficiently small as compared with the deformation of the bottom plate 22. For example, the thickness of the top plate portion 212 is thinner than the thickness of the tubular portion 211, the tubular portion 211 is formed in a bellows shape (bellows shape), or at least a part of the tubular portion 211 is a spring shape. It may be.

And the baseplate 22 is provided so that the opening part which is the other end (lower end) of the cylindrical part 211 of the case main body 21 may be plugged up. The bottom plate 22 is formed in, for example, a circular shape, an elliptical shape, or a polygonal shape when viewed in plan according to the shape of the cylindrical portion 211 of the case body 21. And it fixes to the opening part which is the other end (lower end) of the cylindrical part 211 of the case main body 21 by bolting, adhesion | attachment with a double-sided tape, etc. The bottom plate 22 is made of the same material as that of the case main body 21 and is made of, for example, a metal such as stainless steel, aluminum, or brass, or a resin such as ABS resin, polyacetal, polypropylene, or polytetrafluoroethylene. The bottom plate 22 is a top plate portion 212.
For example, the thickness is set to 50% or less of the thickness of the top plate 212, and is set to 0.5 mm to 2 mm, for example.

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

  In the case 2, the laminated piezoelectric element 3 is accommodated so as to vibrate the bottom plate 22. More specifically, in the multilayer piezoelectric element 3, the direction parallel to the cylindrical portion 211 and perpendicular to the main surface of the bottom plate 22 (the vertical direction in the drawing) is the same as the lamination direction of the multilayer piezoelectric element 3. It is accommodated in the case 2 so as to become. By arranging in this way, the acoustic generator 1 utilizing 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 attached with the bottom plate 22 are greatly deformed. The sound pressure level can be improved.

  As shown in FIG. 2, the stacked piezoelectric element 3 used here includes, for example, a stacked body 33 in which piezoelectric layers 31 and internal electrode layers 32 are alternately stacked, and a side surface of the stacked body 33 that is long in the stacking direction. An external electrode layer 34 that is deposited and electrically connected to an end led to one side surface of the internal electrode layer 32, and an external electrode plate that is bonded along the external electrode layer 34 by a conductive bonding material 35 36. Although not shown in the drawing, the external electrode layer 34 and the external electrode plate 36 are also provided on the side surface opposite to the one side surface on which the external electrode layer 34 and the external electrode plate 36 are provided. .

  The laminated body 33 is formed by alternately laminating the piezoelectric layers 31 and the internal electrode layers 32, and is formed in a square column shape having, for example, a length of 2 to 3 mm, a width of 2 to 3 mm, and a height of 5 to 30 mm. The end portions of 32 are alternately led out to side surfaces (opposite side surfaces) opposite to each other of the stacked body 33.

The piezoelectric layer 31 is formed of a ceramic having piezoelectric characteristics. As such a ceramic, for example, a perovskite oxide made of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ), lithium niobate (LiNbO _3). ), Lithium tantalate (LiTaO ₃ ), or the like can be used.

  The internal electrode layer 32 is formed by simultaneous firing with the ceramic forming the piezoelectric layer 31, and as this forming material, for example, a conductor whose main component is a silver-palladium alloy having low reactivity with a piezoelectric ceramic, or A conductor containing copper, platinum, or the like can be used.

  The external electrode layer 34 is formed by applying and baking a paste made of silver and glass, for example, and is attached to the side surface of the stacked body 33 in the stacking direction. The external electrode layer 34 is electrically connected to the end portion led out to the side surface of the internal electrode layer 32.

  The external electrode plate 36 is provided along the external electrode layer 34, and is bonded by the conductive bonding material 35. The external electrode plate 36 is made of, for example, a metal plate such as stainless steel, and may have slits or holes formed in the width direction as shown in FIG. The conductive bonding material 35 is formed by, for example, a filler such as silver being dispersed almost uniformly in a thermosetting resin such as a polyimide resin.

A lead member 38 is connected to the surface of the external electrode plate 36 via a solder 37. At the time of manufacture, the piezoelectric layer 31 constituting the stacked body 33 is polarized by applying a direct current electric field of 0.1 to 3 kV / mm to the lead member 38. In use, the laminated piezoelectric element 3 expands and contracts due to the inverse piezoelectric effect by connecting the lead member 38 to an external power source and applying a voltage.

  In addition, a spacer 4 is also accommodated inside the case 2, the laminated piezoelectric element 3 and the spacer 4 are arranged coaxially, and the spacer 4 is interposed between the bottom plate 22 and the laminated piezoelectric element 3. It is in a state. The thickness of the spacer 4 is set to 2 mm to 25 mm, for example.

  At this time, the first end face 30 (the lower end face shown in the drawing) of the multilayer piezoelectric element 3 is in contact with the spacer 4, and the second end face of the multilayer piezoelectric element 3 (the face facing the first end face), 1 is in contact with the top plate portion 212 of the case body 21. FIG. Here, the first end face 30 of the multilayer piezoelectric element 3 may be adhered to the spacer 4 with an adhesive or the like, and the second end face of the multilayer piezoelectric element 3 is adhered to the top plate portion 212 of the case body 21. It may be adhered with an agent or the like. In addition, the cylindrical portion 211 is formed so as to restrict the laminated piezoelectric element 3 and the spacer 4 from being displaced or inclined in the in-plane direction of the top plate portion 212 and the bottom plate 22 without being bonded using an adhesive. Protrusions may be provided. In addition, the spacer 4 and the bottom plate 22 may not be usually bonded, but may be bonded. In addition, the top plate part 212 and the laminated piezoelectric element 3 may not be in direct contact with each other but may be provided between them.

  Here, the spacer 4 may be made of a metal such as stainless steel, aluminum, or brass. Since the metal has a wide elastic deformation region, the reaction force of deformation can be added to the force by which the laminated piezoelectric element 3 itself presses the bottom plate 22. In addition, since the metal has a spring property, the energy at the time of deformation is not easily converted to heat, so that the pressing force is not lost and a high force can be maintained and the bottom plate can be further deformed. Therefore, the overall sound pressure level can be improved. On the other hand, the spacer 4 may be made of a resin such as ABS resin, polyacetal, polypropylene, or polytetrafluoroethylene. Since the resin has a high vibration damping rate, the difference in sound pressure level between the peak and the dip seen in the high frequency band can be reduced to contribute to improving the sound quality. The spacer 4 is manufactured by cutting, casting in the case of metal, injection molding in the case of resin, and the like, as viewed in a cross section cut in a direction perpendicular to the stacking direction of the multilayer piezoelectric element 3, for example, circular, It is formed in a quadrangle or polygon.

  When viewed from the stacking direction of the multilayer piezoelectric element 3, the outer edge of the surface 41 on the side in contact with the bottom plate of the spacer 4 is positioned outside the outer edge of the end surface (first end surface 30) of the multilayer piezoelectric element 3. Yes. The outer diameter of the cross section when the spacer 4 is cylindrical is longer than the width of the multilayer piezoelectric element 3 and shorter than the inner diameter of the cylindrical portion 211, and is set to 5 mm to 45 mm, for example.

  The laminated piezoelectric element 3 does not directly contact the bottom plate 22 and the force due to the expansion / contraction of the laminated piezoelectric element 3 is not directly transmitted to the bottom plate 22, but the force due to the expansion / contraction of the laminated piezoelectric element 3 via the spacer 4 having the above structure. By being transmitted to the bottom plate 22, the area of the area where the bottom plate 22 is pushed increases. Accordingly, the vibration wavelength of the bottom plate 22 becomes longer, and the sound pressure level in the entire band including the sound pressure level in the low frequency band can be improved. Further, the difference in sound pressure level between the peak and the dip seen in the high frequency band can be reduced, and the effect of improving the sound quality can be obtained.

  Here, as shown in FIGS. 3 to 5, the outer edge of the surface of the spacer 4 on the side in contact with the bottom plate 22 is the surface of the surface on the side in contact with the multilayer piezoelectric element 3 when viewed from the stacking direction of the multilayer piezoelectric element 3. The structure located outside an outer edge may be sufficient. When the spacer 4 has a circular cross section, the inner diameter of the outer edge of the surface in contact with the laminated piezoelectric element 3 is set to, for example, 50 to 80% of the inner diameter of the outer edge of the surface in contact with the bottom plate 22. .

According to this configuration, since the driving force of the multilayer piezoelectric element 3 is transmitted well toward the bottom plate 22, the bottom plate 22 can be effectively deformed. Further, since the side of the spacer 4 that contacts the bottom plate 22 is wider than the side that contacts the stacked piezoelectric element 3, the vicinity of the outer edge of the side that contacts the bottom plate 22 is deformed along the deformation of the bottom plate 22 and follows. . Further, when the bottom plate 22 is greatly deformed, the contact portion of the spacer 4 with the bottom plate 22 near the outer edge on the side in contact with the bottom plate 22 changes from line contact to surface contact, and the contact area increases. By these, the sound pressure level difference between the peak and the dip seen in the high frequency band can be further reduced. In addition, the increase in the contact area makes it easy for the driving force of the laminated piezoelectric element 3 to be transmitted to the bottom plate 22, and the sound pressure level in the entire band including the sound pressure level in the low frequency band can be improved.

  Further, as shown in FIGS. 4 and 5, when viewed from the stacking direction of the multilayer piezoelectric element 3, the outer edge of the surface of the spacer 4 on the side in contact with the multilayer piezoelectric element 3 is the end face of the multilayer piezoelectric element 3 (first surface). Further, the outer edge of the surface of the spacer 4 on the side in contact with the bottom plate 22 may be positioned on the outer side of the outer surface of the surface on the side of contact with the laminated piezoelectric element 3. 4 shows a shape in which the cross-sectional area of the spacer 4 gradually increases from the surface in contact with the laminated piezoelectric element 3 toward the surface in contact with the bottom plate 22 (for example, a truncated cone shape such as a truncated cone and a truncated pyramid). FIG. 5 shows a shape in which the cross-sectional area of the spacer gradually increases from the surface in contact with the laminated piezoelectric element 3 toward the surface in contact with the bottom plate 22 (for example, a convex disk, a rectangular plate, etc.). Shape).

  The outer edge of the surface of the spacer 4 on the side in contact with the laminated piezoelectric element 3 is positioned outside the outer edge of the end face (first end face 30) of the laminated piezoelectric element 3, so that the laminated piezoelectric element in the spacer 4 is provided. Compared to the configuration in which the outer edge of the surface in contact with 3 is located inside the outer edge of the end face (first end face 30) of the multilayer piezoelectric element 3, the end face (first end face) of the multilayer piezoelectric element 3 30), the driving force of the laminated piezoelectric element 3 can be reliably transmitted to the spacer 4. Further, the partial stress load caused by the spacer 4 partially hitting the end face (first end face 30) of the multilayer piezoelectric element 3 is eliminated, and the long-term reliability against damage to the multilayer piezoelectric element 3 is improved. .

  Further, as shown in FIG. 6, the spacer 4 has a concave portion 41 opened on the surface in contact with the bottom plate 22, and the concave portion 41 is at least a laminated piezoelectric element when viewed from the lamination direction of the laminated piezoelectric element 3. A configuration in which the outer edge of the recess 41 is provided in a region overlapping with the end surface of the element 3 and the outer edge of the end surface (first end surface 30) of the multilayer piezoelectric element 3 may be positioned outside. Here, when the recessed part 41 is formed so that the spacer 4 has just hollowed out the cylinder, when the outer diameter is, for example, 5 mm to 45 mm, the inner diameter is set to a length of, for example, 50 to 95% of the outer shape. The thickness of the top surface is, for example, 1 mm to 20 mm, and the thickness of the side wall is, for example, 1.2 mm to 11.2 mm. In addition, although the spacer 4 shown in FIG. 6 is a shape which provided the recessed part 41 in the spacer 4 shown in FIG. 1, you may provide a recessed part in the spacer 4 of the shape shown in FIGS.

  According to this configuration, since the force due to the expansion and contraction of the laminated piezoelectric element 3 can be transmitted to the region of the bottom plate 22 outside the end face of the laminated piezoelectric element 3, the wavelength of vibration of the bottom plate 22 becomes longer, and the low frequency The sound pressure level in the entire band including the sound pressure level of the band can be improved. Further, since the region of the spacer 4 immediately below the laminated piezoelectric element 3 bends, vibrations in the high frequency band can be attenuated, and the difference in sound pressure level between the peak and the dip seen in the high frequency band can be further reduced. This can also improve the sound quality.

  As shown in FIG. 7, the acoustic generator 1 described so far attaches the bottom plate 22 of the acoustic generator 1 to the diaphragm 5 and vibrates the diaphragm 5 together with the bottom plate 22 by driving the laminated piezoelectric element 3. It can be set as a sound generator. The sound generator is configured to generate sound by generating vibration by the sound generator 1 and thereby vibrating an object to be installed.

Specifically, the electric signal amplified by the amplifier is input to the laminated piezoelectric element 3 constituting the acoustic generator 1, and the diaphragm 5 vibrates together with the bottom plate 22. For example, an electric signal of about 1V is amplified to about ± 50V and inputted.

  The sound generator 1 is attached to the diaphragm 5 using, for example, an adhesive or a double-sided tape. For example, a ceiling plate or a wall of indoor equipment can be used as the diaphragm 5, and the sound generator 1 is installed on these, and the sound generator 1 vibrates the entire installed top plate or wall. Sound and music can be generated from the top and walls. The top plate and the wall may be gypsum board, acrylic resin, construction wood, or the like, as long as it has a desired thickness that functions as a sound generator.

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

  The laminated piezoelectric element was fabricated in the shape of a square column having a length of 2 mm, a width of 2 mm, and a length of 20 mm.

  Two types of spacers with different materials were produced. The spacer (A) was made of SUS304 (tensile elastic modulus 197 GPa), and the spacer (B) was made of ABS resin (tensile elastic modulus 1.9 GPa). Both the spacer (A) and the spacer (B) were formed in a cylindrical shape with a cross-sectional diameter of 30 mm and a thickness of 10 mm.

  Two types of cases were also produced. As the case body (C), a cylindrical shape having an outer diameter of 55 mm and a height of 35 mm was provided with a cutout by cutting, and the dimensions of the cutout portion were a diameter of 35 mm and a depth of 30 mm. As the case body (D), a cylindrical shape having an outer diameter of 55 mm and a height of 25 mm was provided with a cutout by cutting, and the dimensions of the cutout portion were a diameter of 35 mm and a depth of 20 mm. Both materials were SUS304, and the thickness of the top plate was 5 mm.

  The bottom plate was disc-shaped and had a diameter of 55 mm and a thickness of 1 mm.

  And three samples of the sound generator were prepared (Samples 1 to 3). Sample 1 (Comparative Example) was manufactured using a laminated piezoelectric element, a case body (D), and a bottom plate, and was an acoustic generator without a spacer. Sample 2 (Example) was manufactured using a laminated piezoelectric element, a spacer (A), a case body (C), and a bottom plate. Sample 3 (Example) was manufactured using a laminated piezoelectric element, a spacer (B), a case body (C), and a bottom plate.

  The sound pressure characteristics of each of the prepared samples were compared. The driving condition was a sine sweep, the amplitude was ± 15 V, and the frequency was continuously changed from 100 Hz to 20,000 Hz. During the measurement, a microphone was installed 1 m below the anechoic chamber and collected. The collected data was converted to a sound pressure level value for each frequency and compared.

  As a result of measurement, the average sound pressure level at all frequencies (100 to 20 kHz) was 72 dB for sample 1, 78 dB for sample 2, and 79 dB for sample 3. The average sound pressure level in the low frequency band (100 Hz to 1 kHz) is 60 dB for sample 1, 67.5 dB for sample 2, and 66 dB for sample 3, and sample 2 and sample 3 with spacers are samples without spacers. A sound pressure level higher than 1 was shown. Therefore, it can be seen that the sound pressure level at a low frequency is improved by inserting the spacer of the present invention.

  In addition, the difference in sound pressure level between the peak and the dip seen in the vicinity of 3 kHz to 8 kHz, which is a high frequency band, is 16 dB for sample 2 and 11 dB for sample 3, and the spacer material is metal (SUS304) to resin (ABS resin). It was confirmed that it was reduced by changing to.

DESCRIPTION OF SYMBOLS 1 Sound generator 2 Case 21 Case main body 211 Cylindrical part 212 Top plate part 22 Bottom plate 3 Laminated piezoelectric element 31 Piezoelectric layer 32 Internal electrode layer 33 Laminated body 34 External electrode layer 35 Conductive joining material 36 External electrode plate 37 Solder 38 Lead member 4 Spacer 5 Diaphragm

Claims (6)

A case body having an opening and a case provided with a bottom plate provided so as to close the opening; and a laminated piezoelectric element housed in the case so as to vibrate the bottom plate of the case,
A spacer is interposed between the bottom plate and the multilayer piezoelectric element, and an outer edge of a surface of the spacer in contact with the bottom plate is the multilayer piezoelectric element when viewed from the stacking direction of the multilayer piezoelectric element. A sound generator, wherein the sound generator is located outside the outer edge of the end face of the sound generator.   The outer edge of the surface in contact with the bottom plate of the spacer is located outside the outer edge of the surface in contact with the stacked piezoelectric element when viewed from the stacking direction of the stacked piezoelectric element. The sound generator according to claim 1.   When viewed from the stacking direction of the multilayer piezoelectric element, the outer edge of the surface of the spacer that is in contact with the multilayer piezoelectric element is located outside the outer edge of the end surface of the multilayer piezoelectric element, and the bottom plate of the spacer The sound generator according to claim 1, wherein an outer edge of a surface in contact with the multilayer piezoelectric element is positioned outside an outer edge of a surface in contact with the multilayer piezoelectric element.   The spacer has a recess opened on a surface in contact with the bottom plate, and the recess is provided at least in a region overlapping with an end surface of the multilayer piezoelectric element when viewed from the stacking direction of the multilayer piezoelectric element. The sound generator according to any one of claims 1 to 3, wherein an outer edge of the recess is located outside an outer edge of the end face of the multilayer piezoelectric element.   The sound generator according to claim 1, wherein the spacer is made of metal.   The sound generator according to any one of claims 1 to 4, wherein the spacer is made of resin.

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