Acoustic transducer

Abstract

To provide a sound transducer 1 with high sound pressure level and high directivity.SOLUTION: A sound transducer 1 includes a diaphragm 6 having a plurality of cutouts 60, and a piezoelectric drive unit 7 which is an example of a plurality of vibrators arranged on the diaphragm 6 and driving the diaphragm 6, and an arrangement portion 61 of the diaphragm 6, in which at least one piezoelectric drive unit 7 from among the plurality of piezoelectric drive units 7 is arranged, is formed between at least two adjacent cutouts 60 from among the plurality of cutouts 60, and supported on both sides.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an acoustic transducer. [Background technology]

[0002] US Pat. No. 5,399,433 describes an acoustic transducer with actuators separated by a gap. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US20200178000 publication Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide an acoustic transducer that has a high sound pressure level and high directivity. [Means for solving the problem]

[0005] The acoustic transducer according to the present invention comprises: It has a four-sided periphery, The device comprises a diaphragm having a plurality of notches formed therein, and a plurality of vibrating bodies arranged on the diaphragm to drive the diaphragm, and an arrangement portion on the diaphragm in which at least one of the plurality of vibrating bodies is arranged is formed between two adjacent notches of the plurality of notches. At the same time , The center of the diaphragm and the edge of one side Supported on both sides At least four arrangement parts are provided, and the peripheral parts of two sides supporting two of the four arrangement parts are arranged on both sides of the center of the diaphragm in a first direction parallel to the surface of the diaphragm, and the peripheral parts of the other two sides supporting the other two of the four arrangement parts are arranged on both sides of the center of the diaphragm in a second direction perpendicular to the first direction. do. Effect of the Invention

[0006] According to the present invention, it is possible to provide an acoustic transducer that has a high sound pressure level and high directionality. [Brief description of the drawings]

[0007] [Figure 1] 1A and 1B are diagrams illustrating an acoustic transducer according to an embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view taken along the line AA' of FIG. [Diagram 3] 2 is a cross-sectional view taken along the line BB' of FIG. [Figure 4] FIG. 13 is a diagram illustrating a comparative example. [Diagram 5] FIG. 11 is a diagram illustrating a second comparative example. [Figure 6] 4A and 4B are diagrams illustrating the directivity of sound pressure according to the present embodiment. [Figure 7] 5 is a diagram illustrating a sound pressure level per unit power consumption according to the present embodiment. FIG. [Figure 8] 5A and 5B are diagrams illustrating the length and width of a cutout according to the embodiment. [Figure 9] 5A and 5B are diagrams illustrating the relationship between the length of a notch and a sound pressure level according to the embodiment. [Figure 10] 5A and 5B are diagrams illustrating the relationship between the width of a cutout and a sound pressure level according to the embodiment. [Figure 11] 5A and 5B are diagrams illustrating the relationship between the number of notches and sound pressure level according to the present embodiment. [Figure 12] FIG. 13 is a diagram illustrating a modified example of the present embodiment. [Figure 13] FIG. 11 is a diagram illustrating a second modified example of the present embodiment. [Figure 14] FIG. 11 is a diagram illustrating a third modified example of the present embodiment. [Figure 15] 13 is a diagram illustrating the relationship between the angle of the notch and the sound pressure level according to the third modified example. FIG. [Figure 16] FIG. 11 is a diagram illustrating a fourth modified example of the present embodiment. [Figure 17] FIG. 11 is a diagram illustrating a fifth modified example of the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] FIG. 1 is a diagram illustrating an acoustic transducer according to an embodiment of the present invention.

[0009] The acoustic transducer 1 includes a square diaphragm 6 having a plurality of notches 60 formed therein, and a plurality of piezoelectric drivers 7 disposed on the diaphragm 6 to drive the diaphragm 6. The piezoelectric drivers 7 are an example of a vibrating body.

[0010] The vibration plate 6 is made of silicon and includes a plurality of arrangement portions 61 in which the plurality of piezoelectric drive portions 7 are arranged, in a portion of the vibration plate 6 excluding the central portion 8. The plurality of notches 60 are formed in a slit shape in the portion of the vibration plate 6 excluding the central portion 8. The shape of each notch 60 is not limited to a slit shape formed continuously and discontinuously in a straight line, and may be, for example, a plurality of dot-shaped notches arranged discontinuously in a straight line.

[0011] When a voltage is applied to the piezoelectric driver 7 along the surface direction, the piezoelectric film of the piezoelectric driver 7 contracts in the in-plane direction, and the piezoelectric driver 7 deforms in the surface direction as a unimorph with the diaphragm 6. When the voltage applied to the piezoelectric driver 7 is changed over time, the surface of the diaphragm 6 vibrates, generating pressure waves in the surrounding air, which are sensed by humans as sound.

[0012] The input voltage waveform is a voltage-converted version of the waveform of the sound to be reproduced, and sound is reproduced by inputting this voltage waveform to piezoelectric driver 7.

[0013] The same voltage waveform is applied to the plurality of piezoelectric driving units 7 arranged on the diaphragm 6, and the plurality of piezoelectric driving units 7 drive the arrangement unit 61 independently.

[0014] Although the piezoelectric driving unit 7 and the arrangement unit 61 are not arranged in the center 8 of the diaphragm, the vibration of the arrangement unit 61 driven by the piezoelectric driving unit 7 is transmitted, causing the center 8 of the diaphragm to vibrate, thereby generating a pressure wave in the surrounding air.

[0015] Each of the plurality of arrangement portions 61 is formed between at least two of the plurality of cutouts 60 adjacent to each other, and is supported at both ends by the center portion 8 of the diaphragm and the peripheral portion 9 of the diaphragm.

[0016] That is, as shown in FIG. 1(b), a notch 60 is formed at each end of the arrangement portion 61 in a first direction C parallel to the surface of the vibration plate 6, and a notch 60 is not formed at each end of the arrangement portion 61 in a second direction D parallel to the surface of the vibration plate 6 that intersects with the first direction C.

[0017] In other words, each of the multiple arrangement parts 61 is supported at both ends by the center part 8 of the diaphragm and the peripheral part 9 of the diaphragm, and at least two adjacent notches 60 among the multiple cutouts 60 are arranged on both sides of a line D connecting both ends of the arrangement part 61 that are supported at both ends. Also, each of the multiple arrangement parts 61 is divided from each other by the cutouts 60.

[0018] Fig. 2 is a cross-sectional view taken along line AA' in Fig. 1. Fig. 3 is a cross-sectional view taken along line BB' in Fig. 1.

[0019] The piezoelectric driving section 7 has a structure in which a piezoelectric material 7M is sandwiched between an upper electrode 7U and a lower electrode 7L. The diaphragm 6 is supported by being joined to a support layer 13 via a BOX layer 12. Neither the diaphragm 6 nor the support layer 13 is present in the cutout 60. As shown in FIG. 2, the arrangement section 61 is supported at both the center 8 and the peripheral edge 9 of the diaphragm.

[0020] 4 is a diagram for explaining a comparative example, in which the piezoelectric driving portion 7 is disposed over almost the entire area of ​​the diaphragm 6. In the comparative example shown in FIG.

[0021] It is known that in order to increase the sound pressure level of the sound emitted from the diaphragm 6 at a certain frequency, it is necessary to increase the vibration velocity of the surface of the diaphragm 6 that is in contact with the air at that frequency.

[0022] In the case of the comparative example shown in FIG. 4, in order to increase the vibration speed of the surface of the diaphragm 6, it is possible to increase the applied voltage or to make the diaphragm 6 thinner to decrease the bending elasticity and increase the amount of displacement. In order to increase the applied voltage, an amplifier must be inserted, but the size of the housing increases due to the circuit. Furthermore, if the diaphragm 6 is made thinner, the strength is reduced, which causes the device to break down easily both during production and use. In other words, in the comparative example shown in FIG. 4, it is difficult to increase the sound pressure level in practical use.

[0023] Fig. 5 is a diagram illustrating a second comparative example. In the second comparative example shown in Fig. 5, a notch 60 is formed in a vibration plate 6, and a plurality of piezoelectric driving parts 7 are arranged on the vibration plate 6.

[0024] In the second comparative example shown in FIG. 5, the bending elasticity of the diaphragm 6 can be reduced without reducing the strength of the diaphragm 6, so that the magnitude of the surface velocity vector of the diaphragm 6 increases and the sound pressure level generated per applied voltage improves.

[0025] Furthermore, since the area of ​​the piezoelectric driving unit 7 is smaller than that of the comparative example shown in FIG. 4, the piezoelectric driving unit 7 can be driven with less power consumption when compared at the same applied voltage and frequency.

[0026] However, in the second comparative example shown in Figure 5, the notch 60 is formed in the center of the vibration plate 6, and the arrangement portions of the vibration plate 6 in which the multiple piezoelectric driving portions 7 are each arranged are cantilever-supported only by the peripheral portion of the vibration plate 6.

[0027] In this case, the placement section where the piezoelectric driving section 7 is arranged has a long period of time in which the deformation has components other than those in the planar direction of the diaphragm 6, reducing the directionality of the generated sound pressure and reducing the sound pressure level per applied voltage at the observation point.

[0028] In contrast, in the acoustic transducer 1 of this embodiment shown in Figures 1 to 3, at least one arrangement portion 61 is formed between two adjacent notches 60, and therefore, as in the second comparative example shown in Figure 5, the bending elasticity of the arrangement portion 61 is reduced and the sound pressure level per driving power for driving the piezoelectric driving portion 7 is improved.

[0029] Furthermore, in the acoustic transducer 1 according to this embodiment, the arrangement portion 61 on which the piezoelectric driving portion 7 is arranged is supported at both ends, so that the time during which the piezoelectric driving portion 7 deforms in a direction other than the direction of the surface of the diaphragm 6 is shorter than when the piezoelectric driving portion 7 is supported at one end as in the second comparative example shown in Fig. 5, and the direction of the generated sound pressure is increased. As a result, the sound direction is not dispersed, and the sound pressure level in the normal direction to the surface of the diaphragm 6 is increased.

[0030] In the acoustic transducer 1 of this embodiment shown in Figures 1 to 3, the multiple notches 60 are arranged line-symmetrically with respect to each other and formed in the same shape, but the multiple notches 60 may be arranged asymmetrically with respect to each other or may be formed in different shapes.

[0031] Fig. 6 is a diagram illustrating the directivity of sound pressure according to this embodiment, Fig. 6(a) shows the directivity of sound pressure in the second comparative example shown in Fig. 5, and Fig. 6(b) shows the directivity of sound pressure in this embodiment.

[0032] 6(a) and 6(b), θ indicates the inclination angle with respect to the normal direction to the surface of diaphragm 6, and Φ indicates the rotation angle when the normal direction to the surface of diaphragm 6 is used as the rotation axis.

[0033] The sound pressure in the second comparative example shown in FIG. 6(a) may not be greatest when the inclination angle θ is 0 degrees, and the proportion of components other than 0 degrees when the inclination angle θ is large, so the directionality of the sound pressure cannot be said to be high.

[0034] On the other hand, the sound pressure in this embodiment shown in FIG. 6(b) is greatest for the component where the inclination angle θ is 0 degrees, and the ratio of components where the inclination angle θ is other than 0 degrees is small, so that the directionality of the sound pressure can be said to be high.

[0035] FIG. 7 is a graph for explaining the sound pressure level per unit power consumption according to the present embodiment. Graph a shows the sound pressure level per unit of power consumption in the second comparative example shown in FIG. 5, and graph b shows the sound pressure level per unit of power consumption in this embodiment.

[0036] 7, at all frequencies, the present embodiment has a higher sound pressure level per power consumption than the second comparative example. Specifically, the present embodiment can obtain the same sound pressure level with approximately 55% of the power consumption as the second comparative example.

[0037] 8 is a diagram illustrating the length and width of a cutout according to this embodiment. The length of the cutout 60 formed in a slit shape in this embodiment is L, and the width in the short side is W.

[0038] Fig. 9 is a diagram for explaining the relationship between the length of the cutout and the sound pressure level according to this embodiment. Specifically, the relationship between the length L of the cutout 60 and the sound pressure level when the width W of the cutout 60 is constant is shown. As shown in Fig. 9, it can be seen that the sound pressure level improves when the longitudinal length L of the cutout 60 is reduced.

[0039] Fig. 10 is a diagram for explaining the relationship between the width of the notch and the sound pressure level according to this embodiment. Specifically, the relationship between the width W of the notch 60 and the sound pressure level is shown when the length L of the notch 60 is constant. As shown in Fig. 10, the relationship between the width W of the notch 60 and the sound pressure level has a minimum value, and the sound pressure level can be increased by increasing the width W of the notch 60.

[0040] Fig. 11 is a diagram for explaining the relationship between the number of notches and the sound pressure level according to this embodiment. Specifically, it shows the relationship between the number of notches 60 per side of the diaphragm 6 and the sound pressure level when the length L and width W of the notches 60 are constant. As shown in Fig. 11, the relationship between the number of notches 60 and the sound pressure level reaches a maximum at about four notches, and the sound pressure level decreases as the number of notches 60 increases.

[0041] Fig. 12 is a diagram illustrating a modified example of this embodiment. The modified example shown in Fig. 12 differs from the embodiment shown in Figs. 1 to 3 in that the piezoelectric driving units 7 are not arranged at the four corners of the diaphragm 6. This makes it possible to reduce a decrease in sound pressure level caused by the rigidity of the piezoelectric driving units 7 arranged at the four corners of the diaphragm 6, which would otherwise be caused by an improvement in the bending elasticity of the diaphragm 6.

[0042] Fig. 13 is a diagram illustrating a second modified example of the present embodiment. The second modified example shown in Fig. 13 differs from the modified example shown in Fig. 12 in that notches 60 are formed in the four corners of the diaphragm 6.

[0043] The notches 60 formed at the four corners of the vibration plate 6 may be square-shaped notches 60 adjacent to the arrangement portion 61 in which the piezoelectric driving unit 7 is arranged, as shown in Figure 13(a), or may be L-shaped notches 60 communicating with the notches 60 adjacent to the arrangement portion 61, as shown in Figure 13(b).

[0044] This can reduce the reduction in sound pressure level caused by the rigidity of the four corners of the diaphragm 6, which would otherwise be caused by the improvement in bending elasticity of the diaphragm 6.

[0045] FIG. 14 is a diagram for explaining a third modified example of this embodiment. In the third modified example shown in FIG. 14, the longitudinal direction of each of the plurality of cutouts 60 is different from that of the embodiment shown in FIGS. 1 to 3. Specifically, in the embodiment shown in FIGS. 1 to 3, the angle between the longitudinal direction of each of the plurality of cutouts 60 and the side of the diaphragm 6 is 90 degrees, but in the third modified example shown in FIG. 14, the angle θ between the longitudinal direction of each of the plurality of cutouts 60 and the side of the diaphragm 6 is other than 90 degrees. In the third modified example, the length of the cutouts 60 is increased while the area of ​​the central portion 8 of the diaphragm is not reduced, so that the sound pressure level does not decrease.

[0046] Fig. 15 is a diagram for explaining the relationship between the angle of the notch and the sound pressure level according to the third modified example. Specifically, it shows the relationship between the angle θ formed by the longitudinal direction of the notch 60 and the side of the diaphragm 6 facing inward of the diaphragm 6 and the sound pressure level when the length L and width W of the notch 60 are constant. As shown in Fig. 15, the sound pressure level decreases when the angle θ is reduced, and the effect on the sound pressure level is small when the angle θ is 90 degrees or more.

[0047] Fig. 16 is a diagram illustrating a fourth modified example of this embodiment. In the third modified example shown in Fig. 16, the shape of each of the plurality of cutouts 60 is different from that of the embodiment shown in Figs. 1 to 3. Specifically, in the embodiment shown in Figs. 1 to 3, each of the plurality of cutouts 60 is formed as a linear slit, but in the fourth modified example shown in Fig. 16, each of the plurality of cutouts 60 is formed as a curved slit.

[0048] In the fourth modified example, the area of ​​the center 8 of the diaphragm 6 without the notches 60 can be made larger than when linear slit-like notches 60 of the same length are provided, thereby improving the sound pressure level and directivity of the diaphragm 6 as a whole.

[0049] Fig. 17 is a diagram illustrating a fifth modified example of the present embodiment. The fifth modified example shown in Fig. 17 is different from the second modified example shown in Fig. 13 in that the diaphragm 6 includes a folded portion formed in a folded shape, and a plurality of arrangement portions 61 are formed on the folded portion.

[0050] In FIG. 17(a), the diaphragm 6 has a folded portion formed in a folded shape between square notches 60 formed at the four corners of the diaphragm 6, and a plurality of arrangement portions 61 are formed in the folded portion.

[0051] The folded portion includes an arrangement portion 61A, a connecting portion 62a, an arrangement portion 61B, a connecting portion 62b, an arrangement portion 61C, an arrangement portion 61D, a connecting portion 62c, and an arrangement portion 61E.

[0052] Arrangement section 61A has one end connected to peripheral portion 9 of the diaphragm and the other end connected to connecting portion 62a. Arrangement section 61B has one end connected to connecting portion 62a and the other end connected to connecting portion 62b. Arrangement section 61C has one end connected to peripheral portion 9 of the diaphragm and the other end connected to connecting portion 62b. Arrangement section 61D has one end connected to connecting portion 62b and the other end connected to connecting portion 62c. Arrangement section 61E has one end connected to connecting portion 62c and the other end connected to peripheral portion 9 of the diaphragm.

[0053] The connecting portion 62a connects the arrangement portions 61A and 61B to each other in a folded-back shape. The connecting portion 62b connects the arrangement portions 61B and 61C to each other in a folded-back shape, and also connects the arrangement portions 61C and 61D to each other in a folded-back shape. The connecting portion 62c connects the arrangement portions 61D and 61E to each other in a folded-back shape.

[0054] The multiple arrangement portions 61 are formed line-symmetrically on the folded portion. That is, the arrangement portions 61B and 61D are formed line-symmetrically with respect to a direction parallel to the longitudinal direction of the arrangement portion 61C, and the arrangement portions 61A and 61E are formed line-symmetrically with respect to the direction parallel to the longitudinal direction of the arrangement portion 61C.

[0055] In FIG. 17(b), the diaphragm 6 has a folded portion formed in a folded shape between L-shaped notches 60 formed at the four corners of the diaphragm 6, and a plurality of arrangement portions 61 are formed in the folded portion.

[0056] According to the fifth modified example, it is expected that the sound pressure level in the low frequency range of 20 to 1000 Hz will be improved.

[0057] ●Summary● As described above, the acoustic transducer 1 according to one embodiment of the present invention comprises a diaphragm 6 having a plurality of notches 60 formed therein, and a piezoelectric driving unit 7 which is an example of a plurality of vibrators arranged on the diaphragm 6 and drives the diaphragm 6, and an arrangement portion 61 on the diaphragm 6 in which at least one of the plurality of piezoelectric driving units 7 is arranged is formed between at least two adjacent notches 60 among the plurality of notches 60 and is supported at both ends.

[0058] This makes it possible to provide an acoustic transducer 1 with a high sound pressure level and high directivity. Specifically, since at least one arrangement portion 61 is formed between two adjacent notches 60, the bending elasticity is reduced and the sound pressure level per driving power for driving the piezoelectric driving portion 7 is improved.

[0059] In addition, since the arrangement portion 61 is supported at both ends, the time during which it deforms in a direction other than the direction of the surface of the diaphragm 6 is shorter than when it is supported at one end, and the directionality of the generated sound pressure is increased. As a result, the sound direction is not dispersed, and the sound pressure level in the normal direction to the surface of the diaphragm 6 is increased.

[0060] All of the arrangement portions 61 on the vibration plate 6 on which each of the multiple piezoelectric driving portions 7 is arranged are formed between at least two adjacent notches 60 out of the multiple notches 60 and are supported at both ends.

[0061] This makes it possible to provide an acoustic transducer 1 with high sound pressure level and high directivity in all of the multiple arrangement portions 61.

[0062] A notch 60 is formed at each end of the arrangement portion 61 in a first direction C parallel to the surface of the vibration plate 6, and a notch 60 is not formed at each end of the arrangement portion 61 in a second direction D parallel to the surface of the vibration plate 6 that intersects with the first direction C.

[0063] This makes it possible to form the arrangement portion 61 that is arranged between at least two adjacent cutouts 60 and is supported at both ends.

[0064] The multiple cutouts 60 are formed in an area excluding the central portion 8 of the diaphragm 6. This improves the sound pressure level and directivity of the diaphragm 6 as a whole, compared to when the cutouts 60 are provided in the central portion 8 of the diaphragm 6.

[0065] The plurality of cutouts 60 include curved slits 60C. This allows the area of ​​the center 8 of the diaphragm 6 that is free of slits to be larger than when linear slits of the same length are provided, improving the sound pressure level and directionality of the diaphragm 6 as a whole.

[0066] The diaphragm 6 includes a folded portion formed in a folded shape, and the plurality of arrangement portions 61 are formed on the folded portion. Furthermore, the plurality of arrangement portions 61 are formed line-symmetrically on the folded portion. This improves the sound pressure level in the low frequency range of 20 to 1000 Hz.

[0067] An acoustic transducer 1 according to one embodiment of the present invention includes a diaphragm 6 in which multiple notches 60 are formed, and multiple piezoelectric drive units 7 that are arranged on the diaphragm 6 and drive the diaphragm 6, an arrangement portion 61 on the diaphragm 6 in which at least one of the multiple piezoelectric drive units 7 is arranged is supported at both ends, and at least two adjacent notches 60 out of the multiple notches 60 are arranged on both sides of a line D connecting both ends of the arrangement portion 61 that are supported at both ends. This makes it possible to provide an acoustic transducer 1 with a high sound pressure level and high directionality.

[0068] 1 Acoustic transducer 6 diaphragm 7 Piezoelectric drive unit (an example of a vibrating body) 7U upper electrode 7M Piezoelectric material 7L bottom electrode 8 Center of diaphragm 9. Edge of diaphragm 12 BOX layers 13 Support layer 60 Notch 61 Placement section

Claims

1. A diaphragm having four peripheral edges and a plurality of notches formed therein; a plurality of vibrators disposed on the diaphragm to drive the diaphragm; an arrangement portion of the diaphragm in which at least one of the plurality of vibrating bodies is arranged is formed between two adjacent notches of the plurality of notches, and is supported at both ends by a center portion and the peripheral portion of one side of the diaphragm; At least four of the arrangement parts are provided, the peripheral portions of the two sides supporting two of the four arrangement portions are disposed on both sides of the center portion of the diaphragm in a first direction parallel to a surface of the diaphragm, The peripheral portions of the other two sides that respectively support the other two of the four arrangement portions are arranged on both sides of the center portion of the diaphragm in a second direction perpendicular to the first direction.

2. 2. The acoustic transducer according to claim 1, wherein all of the arrangement portions on the diaphragm in which each of the plurality of vibrating bodies is arranged are formed between two adjacent notches among the plurality of notches and are supported at both ends.

3. the notch is formed at each end of the arrangement portion in a first direction parallel to a surface of the diaphragm, 3. The acoustic transducer according to claim 1, wherein the notch is not formed on either end of the arrangement portion in a second direction parallel to the surface of the diaphragm that intersects with the first direction.

4. 4. The acoustic transducer according to claim 1, wherein the plurality of cutouts are formed in an area of ​​the diaphragm excluding a central portion thereof.

5. The acoustic transducer of claim 4 , wherein the plurality of cutouts include curved slits.

6. The diaphragm includes a folded portion formed in a folded shape, 5. The acoustic transducer according to claim 1, wherein the plurality of arrangement portions are formed on the folded portion.

7. A diaphragm having four peripheral edges and a plurality of notches formed therein; a plurality of vibrators disposed on the diaphragm to drive the diaphragm; an arrangement portion of the diaphragm in which at least one of the plurality of vibrating bodies is arranged is supported at both ends by a center portion and the peripheral portion of one side of the diaphragm; Each of two adjacent notches among the plurality of notches is disposed on both sides of a line connecting both ends of the arrangement portion that are supported at both ends, At least four of the arrangement parts are provided, the peripheral portions of the two sides supporting two of the four arrangement portions are disposed on both sides of the center portion of the diaphragm in a first direction parallel to a surface of the diaphragm, The peripheral portions of the other two sides that respectively support the other two of the four arrangement portions are arranged on both sides of the center portion of the diaphragm in a second direction perpendicular to the first direction.

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