Piezoelectric device and tactile feedback device

Abstract

To provide a piezoelectric device and a tactile feedback device with reduced vibration noise.SOLUTION: After intensive research, we found that a vibration frequency of a piezoelectric transducer 30 of a tactile feedback device 1 can be designed to be lower than the Helmholtz resonance frequency of a housing 10, thereby reducing the vibration noise of the piezoelectric transducer 30.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to piezoelectric devices and haptic feedback devices. [Background technology]

[0002] Patent Document 1 below discloses a tactile feedback device, which is a type of piezoelectric device, comprising a piezoelectric sensor for detecting contact and a piezoelectric vibrator that generates vibration as tactile feedback when contact is detected. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-31792 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The inventors conducted extensive research on the vibration noise of piezoelectric vibrators and, as a result, discovered a new technology that can reduce vibration noise.

[0005] The present invention aims to provide a piezoelectric device and a tactile feedback device that reduce vibration noise. [Means for solving the problem]

[0006] A piezoelectric device according to one embodiment of the present invention comprises a vibrating panel, a housing body that defines a cavity between itself and the vibrating panel, a hole connecting the cavity to the outside, and a piezoelectric vibrator provided on the vibrating panel within the cavity, wherein the vibration frequency of the piezoelectric vibrator is lower than the Holmhertz resonance frequency of the housing.

[0007] After diligent research, the inventors discovered that by designing the piezoelectric transducer so that its vibration frequency is lower than the Holmhertz resonance frequency of the housing, the vibration noise of the piezoelectric transducer can be reduced.

[0008] In other forms of piezoelectric devices, the holes are provided in the vibration panel.

[0009] In other forms of piezoelectric devices, the housing has multiple holes.

[0010] Other forms of piezoelectric devices further include a diaphragm interposed between the piezoelectric vibrator and the vibrating panel.

[0011] In piezoelectric devices of other forms, the elastic modulus of the material constituting the vibration panel is lower than that of the material constituting the housing body.

[0012] In piezoelectric devices of other forms, the housing has a wall portion that extends from the edge of the hole toward the cavity.

[0013] In other forms of piezoelectric devices, the elastic modulus of the material constituting the wall is lower than that of the material constituting the vibration panel.

[0014] Other forms of haptic feedback devices include a housing having a vibrating panel, a housing body that defines a cavity between the vibrating panel and the housing, and a hole connecting the cavity to the outside, and a piezoelectric vibrator provided on the vibrating panel within the cavity and vibrating when contact with the vibrating panel is detected, wherein the vibration frequency of the piezoelectric vibrator is lower than the Holmhertz resonance frequency of the housing. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a piezoelectric device and a tactile feedback device that reduce vibration noise. [Brief explanation of the drawing]

[0016] [Figure 1]It is a schematic plan view showing a tactile feedback device according to an embodiment. [Figure 2] It is a sectional view taken along line II-II of the tactile feedback device in FIG. 1. [Figure 3] It is a graph showing the sound pressure characteristics of the tactile feedback device in FIG. 1. [Figure 4] It is a schematic plan view showing a tactile feedback device according to a comparative example. [Figure 5] It is a schematic plan view showing tactile feedback devices of different forms. [Figure 6] It is a sectional view taken along line VI-VI of the tactile feedback device in FIG. 4. [Figure 7] It is a graph showing the sound pressure characteristics of the tactile feedback device in FIG. 4.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals will be used for the same elements or elements having the same function, and redundant descriptions will be omitted.

[0018] In this embodiment, a tactile feedback device, which is a type of piezoelectric device, will be described.

[0019] The tactile feedback device 1 includes a housing 10 and a piezoelectric vibrator 30 disposed within the housing 10.

[0020] The housing 10 has a rectangular parallelepiped outer shape. As an example, the outer dimensions of the housing 10 are 190 mm in the long side × 160 mm in the short side × 50 mm in height. The housing 10 is composed of a plurality of members, and in this embodiment, it is composed of a vibration panel 20 and a housing main body 22. The vibration panel 20 is position-fixed to the housing main body 22 by, for example, screwing or bolting.

[0021] The vibration panel 20 has a square, flat plate shape. For example, the dimensions of the vibration panel 20 are 160 mm square x 1 mm thick. The vibration panel 20 is made of a flexible material such as resin, and in this embodiment, it is made of polycarbonate. The elastic modulus of the material constituting the vibration panel 20 is lower than that of the material constituting the housing body 22.

[0022] The housing body 22 has a box-like shape (i.e., a bottomed rectangular cylinder) with an opening at the top. The housing body 22 has two rectangular openings 24A and 24B. In the following description, one opening will be referred to as the first opening 24A, and the other opening as the second opening 24B. The first opening 24A (hole) and the second opening 24B are separated by a partition wall 23 (wall). The partition wall 23 spans the upper part of the housing body 22 and is a portion that extends linearly in one direction in a plan view, as shown in Figure 1. In this embodiment, the housing body 22 is made of aluminum. The partition wall 23 may be integrated with the housing body 22, or it may be a separate part. If the partition wall 23 is a separate part from the housing body 22, the partition wall 23 can be made of a material having a lower elastic modulus than the elastic modulus of the constituent material of the vibration panel 20.

[0023] The first opening 24A has a rectangular shape and, in this embodiment, has opening dimensions of 148 mm × 26 mm. Therefore, if the opening area S of the first opening 24A is as shown, then in this embodiment, S = 0.0036 mm² 2 That is the case.

[0024] The second opening 24B has a rectangular shape that is almost the same as the planar shape of the vibration panel 20, and in this embodiment, it has an opening dimension of 148 mm × 151 mm. The second opening 24B is completely closed by the vibration panel 20.

[0025] The housing 10 has a cavity 50 defined between the vibration panel 20 and the housing body 22. If the volume of the cavity 50 is V0, then in this embodiment V0 = 0.0011 mm 2As shown in Figure 2, the partition wall 23 of the housing body 22 extends from the edge of the first opening 24A towards the cavity 50. In this embodiment, l = 0.001 mm, where l is the length of the partition wall 23 in the extending direction. The length l of the partition wall 23 in the extending direction represents the depth (length) of the first opening 24A.

[0026] The piezoelectric vibrator 30 has a rectangular flat plate shape, and in this embodiment, it has external dimensions of 30 mm square × 0.1 mm thick. The piezoelectric vibrator 30 is provided in the cavity 50 of the housing 10, and more specifically, it is provided on the cavity 50 side of the vibration panel 20 via a diaphragm 31. The diaphragm 31 has a rectangular flat plate shape, and in this embodiment, it has external dimensions of 80 mm long × 60 mm short × 0.25 mm thick. The diaphragm 31 is made of, for example, an iron-nickel alloy (42% Ni-Fe as an example).

[0027] The piezoelectric vibrator 30 has a configuration in which a piezoelectric layer 32 is sandwiched between a pair of electrode layers 34A and 34B in the thickness direction of the vibrating panel 20. The piezoelectric layer 32 may be a single-layer structure including a single piezoelectric material layer, or it may be a multilayer structure in which multiple piezoelectric material layers and internal electrode layers are alternately stacked.

[0028] A control unit 40 is electrically connected to the piezoelectric vibrator 30. The control unit 40 inputs a voltage signal to the piezoelectric vibrator 30, which applies a voltage between a pair of electrode layers 34A and 34B. When the piezoelectric vibrator 30 receives a voltage signal from the control unit 40, it oscillates at a predetermined vibration frequency. The control unit 40 also detects contact with the vibration panel 20 from the voltage change between the pair of electrode layers 34A and 34B of the piezoelectric vibrator 30 that occurs when the vibration panel 20 is in contact with the vibration panel 20.

[0029] Therefore, the haptic feedback device 1, in cooperation with the control unit 40, can detect contact with the vibration panel 20, and when contact with the vibration panel 20 is detected, it can vibrate the vibration panel 20 as haptic feedback.

[0030] The inventors conducted extensive research on the vibration noise of piezoelectric vibrators and, as a result, discovered a new technology that can reduce vibration noise.

[0031] After diligent research, the inventors discovered that by designing the piezoelectric vibrator 30 of the haptic feedback device 1 so that its vibration frequency is lower than the Holmhertz resonance frequency of the housing 10, the vibration noise of the piezoelectric vibrator 30 can be reduced.

[0032] In this embodiment, the Holmhertz resonance frequency (f) of the housing 10 is determined. H ) can be calculated using the following formula.

[0033]

number

[0034] In the above formula, r is the radius when the opening is circular, and can be calculated using the square root of S / π when the opening is rectangular. In this embodiment, r in the above formula is 0.00336 mm.

[0035] From the above formula, the Holmhertz resonance frequency f of the housing 10 in this embodiment H This is approximately 442Hz.

[0036] Figure 3 is a graph showing the sound pressure characteristics of haptic feedback device 1. In the graph in Figure 3, the horizontal axis represents frequency (Hz) and the vertical axis represents sound pressure (dB). The solid line in the graph in Figure 3 shows the sound pressure characteristics of haptic feedback device 1 (example), and the dashed line in the graph in Figure 3 shows the sound pressure characteristics of the haptic feedback device for comparison (comparative example) shown in Figure 4.

[0037] Figure 4 shows a haptic feedback device 101 according to a comparative example. The haptic feedback device 101 has a configuration in which one opening provided in a housing 10 having one opening at the top is completely covered by a vibration panel 20. In the haptic feedback device 101, since there is no opening in the housing 10, Holmhertz resonance cannot occur.

[0038] The graph in Figure 3 shows that in the embodiment, the sound pressure reaches its maximum value (approximately 98 dB) near the Holmhertz resonance frequency of the housing 10 (approximately 442 Hz). Furthermore, the graph in Figure 3 shows that in the embodiment, the sound pressure decreases sharply in the frequency range lower than the Holmhertz resonance frequency of the housing 10. In particular, in the embodiment, the sound pressure is significantly lower than in the comparative example in the frequency range below 300 Hz.

[0039] As described above, the inventors have newly discovered that the vibration noise of the piezoelectric vibrator 30 can be effectively reduced by designing the piezoelectric vibrator 30 so that its vibration frequency is lower than the Holmhertz resonance frequency of the housing 10. If the haptic feedback device 101 has a noise cancellation function, the noise cancellation function can be improved by reducing the vibration noise of the piezoelectric vibrator 30. In the haptic feedback device 1, the vibration frequency of the piezoelectric vibrator 30 can be determined from the range of 100 to 400 Hz, or from the range of 100 to 290 Hz, and as an example, a frequency around 200 Hz can be adopted.

[0040] The structure of the haptic feedback device 1 is not limited to the structure described above, but may also be the structure shown in Figures 5 and 6.

[0041] In the tactile feedback device 1A shown in FIGS. 5 and 6, the housing main body portion 22 of the housing 10 has only one rectangular opening 24C. The opening 24C is completely blocked by the vibration panel 20. In the tactile feedback device 1A, the vibration panel 20 has a rectangular shape substantially the same as the opening shape of the opening 24C. The vibration panel 20 has a plurality of holes 21 penetrating in the thickness direction. Each hole 21 has a circular cross section, and its radius is, for example, 2.5 mm. The plurality of holes 21 are evenly arranged around the piezoelectric vibrator 30 in a plan view and are not arranged in the formation region of the piezoelectric vibrator 30.

[0042] Similar to the tactile feedback device 1, the tactile feedback device 1A has the holes 21 that connect the cavity 50 in the housing 10 to the outside, so that Helmholtz resonance can occur.

[0043] In the tactile feedback device 1A, S at the Helmholtz resonance frequency (f H ) of the housing 10 is the total opening area of the holes 21 (that is, 0.0036 mm 2 ), V0 is the volume of the cavity 50 (that is, 0.0011 mm 2 ), and l is the thickness of the vibration panel 20 (that is, 0.001 mm). r at the Helmholtz resonance frequency (f H ) of the housing 10 is calculated as 0.00336 mm from the square root of S / π.

[0044] The Helmholtz resonance frequency f H of the housing 10 in the tactile feedback device 1A is approximately 347 Hz.

[0045] FIG. 7 is a graph showing the sound pressure characteristics of the tactile feedback device 1A. The solid line in the graph of FIG. 7 shows the sound pressure characteristics (Example) related to the tactile feedback device 1A, and the broken line in the graph of FIG. 7 shows the sound pressure characteristics of the tactile feedback device (Comparative Example) for comparison shown in FIG. 4.

[0046] From the graph in Figure 7, it can be seen that in the embodiment, the sound pressure reaches its maximum value (approximately 94 dB) near the Holmhertz resonance frequency of the housing 10 (approximately 347 Hz). Furthermore, from the graph in Figure 7, it can be seen that in the embodiment, the sound pressure decreases sharply in the frequency range lower than the Holmhertz resonance frequency of the housing 10. In particular, in the embodiment, the sound pressure is significantly lower than in the comparative example in the frequency range lower than 300 Hz. In the haptic feedback device 1A, the vibration frequency of the piezoelectric vibrator 30 can be determined from the range of 100 to 350 Hz, or from the range of 100 to 280 Hz, and as an example, a frequency around 200 Hz can be adopted.

[0047] Although preferred embodiments of the present invention have been described above, the present invention is not necessarily limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0048] For example, the number of holes provided in the housing can be increased or decreased as appropriate. The shape of the holes (cross-sectional shape) is not limited to circles or rectangles; it may also be elliptical or polygonal. [Explanation of Symbols]

[0049] 1, 1A, 101...Haptic feedback device, 10...Housing, 20...Vibration panel, 21...Hole, 24A...First opening, 24B...Second opening, 30...Piezoelectric vibrator, 50...Cavity.

Claims

1. a housing having a diaphragm panel, a housing main body portion defining a cavity between the diaphragm panel and the housing main body portion, and a hole portion connecting the cavity to the outside; a piezoelectric vibrator provided on the diaphragm panel within the cavity; Equipped with A piezoelectric device, wherein the vibration frequency of the piezoelectric vibrator is lower than the Holmes-Hertz resonance frequency of the housing.

2. The piezoelectric device according to claim 1 , wherein the hole is provided in the diaphragm panel.

3. The piezoelectric device according to claim 1 , wherein the housing has a plurality of holes.

4. 4. The piezoelectric device according to claim 1, further comprising a vibration plate interposed between the piezoelectric vibrator and the vibration panel.

5. 5. The piezoelectric device according to claim 1, wherein the elastic modulus of the material constituting the diaphragm panel is lower than the elastic modulus of the material constituting the housing main body.

6. 6. The piezoelectric device according to claim 1, wherein the housing has a wall extending from an edge of the hole toward the cavity.

7. The piezoelectric device according to claim 6 , wherein the elastic modulus of the material forming the wall portion is lower than the elastic modulus of the material forming the diaphragm panel.

8. a housing having a diaphragm panel, a housing main body portion defining a cavity between the diaphragm panel and the housing main body portion, and a hole portion connecting the cavity to the outside; a piezoelectric vibrator provided on the diaphragm panel within the cavity, the piezoelectric vibrator vibrating when contact with the diaphragm panel is detected; Equipped with A tactile feedback device, wherein the vibration frequency of the piezoelectric vibrator is lower than the Holmeshertz resonance frequency of the housing.

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