Actuator
The actuator design with a piezoelectric vibrator and synchronized leaf spring achieves larger displacement vibrations by leveraging synchronized flexural vibrations, addressing the limitation of displacement in existing actuators.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- MURATA MFG CO LTD
- Filing Date
- 2024-11-11
- Publication Date
- 2026-05-21
AI Technical Summary
Existing actuators utilizing air resonance in chambers formed by vibration substrates and diaphragms have limited displacement amounts.
An actuator design incorporating a piezoelectric vibrator and a leaf spring, where the leaf spring is connected to the piezoelectric vibrator in specific regions and vibrates in sync, allowing for greater displacement through synchronized flexural vibrations.
The actuator achieves larger displacement vibrations compared to conventional designs, with the leaf spring's displacement being twice as large as the piezoelectric vibrator's, enhancing vibration generation capabilities.
Smart Images
Figure 2026084376000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an actuator including a piezoelectric vibrator including a piezoelectric element and a plate member.
Background Art
[0002] Patent Document 1 describes a configuration including a piezoelectric element, a vibration substrate, and a diaphragm. The vibration substrate is disposed on the piezoelectric element. The vibration substrate has a recess. The diaphragm is disposed at a position covering the recess of the vibration substrate.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] In the configuration of Patent Document 1, since the vibration due to the air resonance in the chamber formed by the vibration substrate and the diaphragm is utilized, the displacement amount of the vibration is limited.
[0005] Therefore, an object of the present invention is to provide an actuator capable of obtaining a vibration with a large displacement amount.
Means for Solving the Problems
[0006] An actuator according to an embodiment of the present invention includes a piezoelectric vibrator, a leaf spring, and a support. The piezoelectric vibrator is composed of a laminate of a plate member and a piezoelectric element, and has a first surface and a second surface facing each other. The leaf spring has a third surface connected to the first surface and a fourth surface facing the third surface. The support is formed in an annular shape having an end surface and a peripheral surface.
[0007] The leaf spring has a ring-shaped first region and a second region enclosed by the first region. The first region has a third region on the outer edge side of the leaf spring and a fourth region on the second region side. The leaf spring is connected to the support and the piezoelectric vibrator in the third region, sandwiched between the end face of the support and the first face of the piezoelectric vibrator. The leaf spring is connected to the piezoelectric vibrator in the fourth region but not to the support. The leaf spring is not connected to the piezoelectric vibrator in the second region.
[0008] In this configuration, the leaf spring vibrates in sync with the vibration of the piezoelectric vibrator. In this case, the displacement of the leaf spring is greater than the displacement of the piezoelectric vibrator. [Effects of the Invention]
[0009] This invention provides an actuator that can produce vibrations with large displacements. [Brief explanation of the drawing]
[0010] [Figure 1] Figure 1 is an exploded perspective view of an actuator according to the first embodiment of the present invention. [Figure 2] Figure 2 is an exploded perspective view of an actuator according to the first embodiment of the present invention. [Figure 3] Figures 3(A) and 3(B) are partial cross-sectional views of an actuator according to the first embodiment of the present invention. [Figure 4] Figure 4(A) is a plan view of a leaf spring according to the first embodiment of the present invention, Figure 4(B) is a perspective view of the side view of the leaf spring, Figure 4(C) is a cross-sectional view of the leaf spring, and Figure 4(D) is an enlarged cross-sectional view of the bent portion. [Figure 5] Figure 5 is a partial cross-sectional view showing an example of the vibration state of an actuator according to the first embodiment of the present invention. [Figure 6] Figure 6 is a partial cross-sectional view of an actuator according to a second embodiment of the present invention. [Figure 7] Figures 7(A) and 7(B) show the derived shapes of leaf springs. [Figure 8]Figure 8(A) is a plan view showing a derived shape of a leaf spring, and Figure 8(B) is a partial cross-sectional view thereof. [Modes for carrying out the invention]
[0011] [First Embodiment] An actuator according to the first embodiment of the present invention will be described with reference to the figures. Figures 1 and 2 are exploded perspective views of the actuator according to the first embodiment of the present invention. Figures 1 and 2 are views of each other in opposite directions in the stacking direction. Figures 3(A) and 3(B) are partial cross-sectional views of the actuator according to the first embodiment of the present invention. Figures 3(A) and 3(B) are views of the actuator from the center Po in a plan view, showing one outer edge (support) side.
[0012] Note that the black circles in each figure, which indicate points (for example, the center point), represent geometric positions and do not need to be physically visible objects. Also, in the following explanation, viewing each component of the actuator 10 in the stacking direction is referred to as a plan view of each conceptual element.
[0013] As shown in Figures 1, 2, 3(A), and 3(B), the actuator 10 comprises a piezoelectric vibrator 100, a leaf spring 40, and a support ST.
[0014] The piezoelectric vibrator 100 is composed of a laminate of piezoelectric elements 21 and 22, plate members 31 and 32, and plate members 33. The piezoelectric vibrator 100 has two opposing surfaces F101 and F102. Surface F101 corresponds to the "first surface," and surface F102 corresponds to the "second surface."
[0015] Each piezoelectric element 21 and piezoelectric element 22 is composed of a flat-plate shaped piezoelectric body and a driving electrode formed on the opposing flat surfaces of the piezoelectric body.
[0016] The plate members 31, 32, and 33 are made of flat metal. The thicknesses of the plate members 31, 32, and 33 are each constant.
[0017] In the piezoelectric vibrator 100, the plate member 32, the piezoelectric element 22, the plate member 33, the piezoelectric element 21, and the plate member 31 are laminated in this order from the surface F102 toward the surface F101. Thus, the piezoelectric vibrator 100 has a bimorph structure.
[0018] The surface of the plate member 31 on the side opposite to the side facing the piezoelectric element 21 becomes the surface F101 of the piezoelectric vibrator 100. The surface of the plate member 32 on the side opposite to the side facing the piezoelectric element 22 becomes the surface F102 of the piezoelectric vibrator 100.
[0019] FIG. 4(A) is a plan view of the leaf spring according to the first embodiment of the present invention, FIG. 4(B) is a perspective view of the side view of the leaf spring, FIG. 4(C) is a cross-sectional view of the leaf spring, and FIG. 4(D) is an enlarged cross-sectional view of the bent portion. FIG. 4(C) shows the A-A cross-section in FIG. 4(A).
[0020] As shown in FIGS. 4(A), 4(B), and 4(C), the leaf spring 40 has surfaces F401 and F402 facing each other. The surface F401 corresponds to the "fourth surface", and the surface F402 corresponds to the "third surface".
[0021] The leaf spring 40 is made of, for example, a metal plate. The thickness of the leaf spring 40 is constant throughout. The leaf spring 40 is made of a material that is more likely to bend and vibrate than the piezoelectric vibrator 100.
[0022] The leaf spring 40 has a first region 41 and a second region 42. In a plan view, the first region 41 is in an annular shape and includes the outer edge Fe40 of the leaf spring 40. In a plan view, the second region 42 is in a circular shape surrounded by the first region 41 and includes the center Po40 of the leaf spring 40.
[0023] The first region 41 has a third region 411 and a fourth region 412. The third region 411 is an annular shape with the center Po 40 as its center point in a plan view, and includes an outer edge Fe 40. The fourth region 412 is an annular shape with the center Po 40 as its center point in a plan view, and connects to the inner circumferential end of the third region 411. The first region 41 has a flat shape extending across the third region 411 and the fourth region 412.
[0024] The second region 42 comprises a fifth region 421 and a sixth region 422. The fifth region 421 is circular in shape with center Po in a plan view. The sixth region 422 is annular in shape with center Po in a plan view. The inner circumferential end of the sixth region 422 connects to the fifth region 421. The outer circumferential end of the sixth region 422 connects to the inner circumferential end of the fourth region 412 of the first region 41.
[0025] The leaf spring 40 has a shape in which the second region 42 protrudes toward the surface F401 side than the first region 41. More specifically, the second region 42 has a tapered shape in which the surfaces F401 and F402 of the fifth region 421 are parallel to the surfaces F401 and F402 of the first region 41, and the sixth region 422 has a slope that is not 90° when viewed from the side.
[0026] To express this in another way using Figure 4(D), at the connection between the fourth region 412 and the sixth region 422, the bending angle on the surface F402 side is greater than 90° and less than 180°. At the connection between the sixth region 422 and the fifth region 421, the bending angle on the surface F402 side is greater than 180° and less than 270°. The fourth region 412, the sixth region 422, and the fifth region 421 are connected in such a way that these conditions are satisfied.
[0027] As shown in Figures 3(A) and 3(B), the leaf spring 40 with this configuration is positioned on the piezoelectric vibrator 100 such that its surface F402 is adjacent to the surface F101 of the piezoelectric vibrator 100. The outer edge Fe40 of the leaf spring 40 is positioned approximately at the same location as the outer edge of the piezoelectric vibrator 100.
[0028] The surface F402 of the first region 41 of the leaf spring 40 is joined to the surface F101 of the outer edge of the piezoelectric vibrator 100. This joining may be done by adhesive. However, if adhesive is used, it is preferable that the adhesive has a high elastic modulus, in other words, that the stress on the piezoelectric vibrator 100 is transmitted to the leaf spring 40 with low loss.
[0029] Since the leaf spring 40 has the structure described above, the second region 42 of the leaf spring 40 is spaced apart from the surface F101 of the piezoelectric vibrator 100.
[0030] In this case, in a plan view (viewed in the stacking direction), the center Po 41 of the leaf spring 40 coincides with the center Po of the piezoelectric vibrator 100. This coincidence includes within the range of manufacturing tolerances.
[0031] The support ST is made of a highly rigid material such as metal. The support ST has an annular shape when viewed from above. The support ST has a circular inner surface FiST and an outer surface FeST when viewed from above. The inner surface FiST is the inner surface of the annular shape, and the outer surface FeST is the outer surface of the annular shape. The support ST has an end surface FST1 at one end in the thickness direction, which is an annular plane. The support ST has an end surface FST2 at the other end in the thickness direction, which is an annular plane.
[0032] The end face FST2 of the support ST is connected to the surface F401 of the third region 411 of the leaf spring 40. This connection is a physical connection, achieved by joining, bonding, etc. However, if bonding is used, it is preferable to use an adhesive with a high elastic modulus, in other words, an adhesive that can fix the piezoelectric vibrator 100 and the leaf spring 40 so that they do not vibrate substantially in the portion that overlaps with the support ST in a plan view.
[0033] The fourth region 412 of the leaf spring 40 is not connected to the support ST.
[0034] Figure 5 is a partial cross-sectional view showing an example of the vibration state of an actuator according to the first embodiment of the present invention. Figure 5 shows the same parts as in Figures 3(A) and 3(B). In Figure 5, 100DFL indicates the state in which the displacement of the piezoelectric vibrator 100 is at its minimum (0), and 100MX indicates the state in which the displacement of the piezoelectric vibrator 100 is at its maximum. 40DFL indicates the state in which the displacement of the leaf spring 40 is at its minimum (0), and 40MX indicates the state in which the displacement of the leaf spring 40 is at its maximum.
[0035] In this configuration, when a drive signal of a predetermined frequency is applied to the piezoelectric vibrator 100, the piezoelectric elements 21 and 22 of the piezoelectric vibrator 100 deform, and stress due to this deformation is applied to the plate members 31, 32, and 33. The outer edge REo100 of the piezoelectric vibrator 100 is fixed to the support ST via the third region 411 of the leaf spring 40. As a result, the piezoelectric vibrator 100 bends and vibrates with the inner circumferential end of the outer edge REo100 (the end that overlaps with the inner circumferential surface FiST1 of the support ST in a plan view) as the fixed end. The point of maximum amplitude of this bending vibration is the center Po of the piezoelectric vibrator 100. In addition, in this configuration, the frequency of the drive signal is made to approximately match the resonance frequency of the piezoelectric vibrator 100. As a result, the piezoelectric vibrator 100 performs a first-order resonance bending vibration.
[0036] The leaf spring 40 is connected to the piezoelectric vibrator 100 in the fourth region 412 between the third region 411 (the part fixed to the support ST) and the second region 42. Therefore, the strain stress generated when the piezoelectric vibrator 100 vibrates is applied to the fourth region 412 of the leaf spring 40.
[0037] The stress applied to the fourth region 412 is applied to the second region 42 (sixth region 422 and fifth region 421). As a result, the leaf spring 40 vibrates in a flexural manner. The flexural vibration of the leaf spring 40 is synchronized with the flexural vibration of the piezoelectric vibrator 100. The point of maximum amplitude of the flexural vibration of the leaf spring 40 is at the center Po 40 of the leaf spring 40.
[0038] As described above, the leaf spring 40 is more prone to bending vibration than the piezoelectric vibrator 100. Therefore, the displacement of the leaf spring 40 due to vibration is greater than the displacement of the piezoelectric vibrator 100 due to vibration. For example, as shown in Figure 5, the maximum displacement DSP40 at the center Po41 of the leaf spring 40 is greater than the maximum displacement DSP100 at the center Po of the piezoelectric vibrator 100, for example, about twice as large.
[0039] Thus, the actuator 10 can generate vibrations with a larger displacement than the configuration without the leaf spring 40.
[0040] Furthermore, in the actuator 10, the sixth region 422 of the second region 42 is tapered, which allows the stress applied to the leaf spring 40 to be converted into bending vibration more effectively. As a result, the actuator 10 can generate vibrations with even larger displacements.
[0041] Furthermore, in the actuator 10, the shape, material, weight, etc. of the leaf spring 40 are configured such that the natural vibration frequency F40 of the leaf spring 40 satisfies the following range with respect to the resonant frequency F100 of the piezoelectric vibrator 100.
[0042] 0.3×F100 <F40<0.7×F100 By satisfying this range, the leaf spring 40 vibrates more effectively in response to the vibration of the piezoelectric vibrator 100. As a result, the actuator 10 can effectively generate vibrations with large displacements.
[0043] Furthermore, it is preferable that the dimensions of each component in the actuator 10 satisfy the following conditions (see, for example, Figure 3(B)).
[0044] The distance from the center of the leaf spring 40 (the position that coincides with the center Po of the piezoelectric vibrator 100 in a plan view) to the end of the second region 42 that connects to the fourth region 412 (the distance obtained by subtracting L412 from LVB in Figure 3(B)) is greater than the distance between the connection end of the fourth region 412 with the second region 42 and the connection end with the third region 411 (the length L412 of the fourth region 412).
[0045] The distance LVB from the center Po of the piezoelectric vibrator 100 to the inner circumference end of the outer edge REo100, and the length L422 of the sixth region 422 in a plan view (the distance between the connection end to the fifth region 421 and the connection end to the fourth region 412) satisfy the following relationship.
[0046] (13 / 50) × LVB ≤ L422 ≤ (21 / 50) × LVB The distance LVB from the center Po of the piezoelectric vibrator 100 to the inner end of the outer edge REo100, and the length L412 of the fourth region 412 in a plan view (the distance between the connection end to the third region 411 and the connection end to the sixth region 422) satisfy the following relationship.
[0047] (1 / 25) × LVB ≤ L412 ≤ (3 / 10) × LVB By satisfying any of these conditions, the actuator 10 can effectively generate vibrations with large displacements.
[0048] [Second Embodiment] An actuator according to a second embodiment of the present invention will be described with reference to the figures. Figure 6 is a partial cross-sectional view of the actuator according to the second embodiment of the present invention.
[0049] As shown in Figure 6, the actuator 10A according to the second embodiment differs from the actuator 10 according to the first embodiment in that it includes a piezoelectric vibrator 100A. The other components of the actuator 10A are the same as those of the actuator 10, and a description of the similar parts will be omitted.
[0050] The actuator 10 includes a piezoelectric vibrator 100A. The piezoelectric vibrator 100A includes piezoelectric elements 21A and 22A. The piezoelectric elements 21A and 22A are polarized at a predetermined distance from the center of the piezoelectric body toward the outer edge.
[0051] Viewed in the direction in which the support ST, the leaf spring 40, and the piezoelectric vibrator 100 are aligned, the fourth region 412 of the leaf spring 40 is positioned at a different location from the polarization reversal position Ppr. More specifically, the fourth region 412 of the leaf spring 40 is positioned closer to the support ST than the polarization reversal position Ppr.
[0052] With this configuration, actuator 10A can generate vibrations with large displacements, similar to actuator 10.
[0053] In a plan view, it is preferable that the distance from the center Po to the fourth region 412 is between 1.2 and 1.4 times the distance from the center Po to the polarization reversal position Ppr.
[0054] (Derived shape of leaf spring) Figures 7(A) and 7(B) show derived shapes of a leaf spring. Figures 7(A) and 7(B) are cross-sectional views of the leaf spring from the center Po40 towards one outer edge (support) side in a plan view.
[0055] As shown in Figure 7(A), the leaf spring 40X1 has a second region 42X1. The second region 42X1 has a fifth region 421X1 and a sixth region 422X1.
[0056] The thickness D421X1 of the fifth region 421X1 is smaller than the thickness D41 of the first region 41 (third region 411 and fourth region 412). This is sufficient if the maximum thickness of the fifth region 421X1 is smaller than the minimum thickness of the first region 41.
[0057] The sixth region 422X1 has a thickness D41 at its connection end (one end) to the fourth region 412, and a thickness D421X1 at its connection end (the other end) to the fifth region 421X1. The thickness of the sixth region 422X1 gradually increases from one end to the other. As a result, the sixth region 422X1 has a region with a thickness smaller than the thickness D41 of the first region 41. Therefore, the second region 42X1, which is composed of the fifth region 421X1 and the sixth region 422X1, has a region with a thickness smaller than the thickness D41 of the first region 41. The average thickness of the second region 42X1 is smaller than the thickness D41 of the first region 41 (third region 411 and fourth region 412).
[0058] The aforementioned thicknesses can be measured, for example, by observing the cross-section with an optical microscope or using a micrometer. The average thickness of each region can then be calculated by measuring the thickness at multiple points within each region and averaging the measured thicknesses.
[0059] This configuration allows for a greater maximum displacement of the 40X1 leaf spring.
[0060] As shown in Figure 7(B), the leaf spring 40X2 has a second region 42X2. The second region 42X2 has a fifth region 421X2 and a sixth region 422X2.
[0061] The thickness D421X2 of the fifth region 421X2 is greater than the thickness D41 of the first region 41 (third region 411 and fourth region 412), unlike the thickness D41 of the first region 41. This can be achieved by at least satisfying the condition that the minimum thickness of the fifth region 421X2 is greater than the maximum thickness of the first region 41.
[0062] The sixth region 422X2 has a thickness D41 at its connection end (one end) to the fourth region 412, and a thickness D421X2 at its connection end (the other end) to the fifth region 421X2. The thickness of the sixth region 422X2 gradually increases from one end to the other. As a result, the sixth region 422X2 has a region with a thickness greater than the thickness D41 of the first region 41. Therefore, the second region 42X2, which is composed of the fifth region 421X1 and the sixth region 422X1, has a region with a thickness greater than the thickness D41 of the first region 41. Furthermore, the average thickness of the second region 42X1 is greater than the thickness D41 of the first region 41 (third region 411 and fourth region 412).
[0063] This configuration allows the maximum displacement of the leaf spring 40X1 to be greater than in the configuration without the leaf spring 40X1.
[0064] Figure 8(A) is a plan view showing a derived shape of a leaf spring, and Figure 8(B) is a partial cross-sectional view thereof.
[0065] As shown in Figure 8(A), the leaf spring 40X3 has a second region 42X3. The second region 42X3 has a fifth region 421 and a sixth region 422X3.
[0066] The thickness D421 of the fifth region 421 is the same as the thickness D41 of the first region 41 (third region 411 and fourth region 412). The thickness of the sixth region 422X3 is the same as the thickness D421 of the fifth region 421 and the thickness D41 of the first region 41.
[0067] Multiple through-holes TH42 are formed in the sixth region 422X3. These multiple through-holes TH42 penetrate the sixth region 422X3 from surface F401 to surface F402.
[0068] This configuration allows for a reduction in the mass and rigidity of the sixth region 422X3 compared to a configuration where the through-hole TH42 is not formed, thereby increasing the maximum displacement of the leaf spring 40X3.
[0069] Furthermore, it is preferable that the multiple through-holes TH42 are formed point-symmetrically with respect to the center Po42 in a plan view.
[0070] Furthermore, the various derived shapes mentioned above can be combined as appropriate.
[0071] In the embodiments described above, the leaf spring was shown to be made of metal. However, the leaf spring is not limited to metal. For example, even if it is not made of metal, as long as the condition is met that the natural vibration frequency of the leaf spring and the resonant frequency of the piezoelectric vibrator are approximately the same (more preferably coincide), the actuator can generate vibrations with a large displacement.
[0072] In the embodiments described above, the outer edge of the piezoelectric vibrator was shown to be circular. However, the outer edge of the piezoelectric vibrator is not limited to a circular shape. [Explanation of Symbols]
[0073] 10, 10A: Actuator 21, 21A: Piezoelectric element 22, 22A: Piezoelectric element 31, 32, 33: Plate members 40, 40X1, 40X2, 40X3: Leaf spring 41:First area 42, 42X1, 42X2, 42X3: 2nd area 100, 100A: Piezoelectric vibrator 411: Third area 412: 4th area 421, 421X1, 421X2: 5th area 422, 422X1, 422X2, 422X3: 6th area ST: Support TH42:Through hole
Claims
1. A piezoelectric vibrator is composed of a laminate of a plate member and a piezoelectric element, and has a first surface and a second surface that face each other. A leaf spring having a third surface connected to the first surface and a fourth surface facing the third surface, A support structure composed of an annular shape having an end face and a circumferential face, Equipped with, The leaf spring has a ring-shaped first region and a second region surrounded by the first region. The first region comprises a third region on the outer edge side of the leaf spring and a fourth region on the second region side. The aforementioned leaf spring is In the third region, the support and the piezoelectric vibrator are connected while being sandwiched between the end face of the support and the first surface of the piezoelectric vibrator. In the fourth region, it is connected to the first surface of the piezoelectric vibrator and not connected to the support, In the second region, the piezoelectric vibrator is not connected to the second region. Actuator.
2. The average thickness of the second region in the leaf spring is smaller than the thickness of the fourth region. The actuator according to claim 1.
3. The second region includes a fifth region containing the center of the leaf spring and a sixth region connecting the fifth region and the fourth region. The thickness of the fifth region is smaller than the average thickness of the sixth region. The actuator according to claim 2.
4. The distance from the center of the leaf spring in the second region to the connection end in the fourth region is greater than the distance between the connection end in the fourth region and the second region and the connection end in the third region. The actuator according to any one of claims 1 to 3.
5. The second region of the leaf spring has a region with a different thickness from the first region, or has a through hole. The actuator according to any one of claims 1 to 4.
6. The second region includes a fifth region containing the center of the leaf spring and a sixth region connecting the fifth region and the fourth region. The through hole is located in the sixth region. The actuator according to claim 5.
7. The piezoelectric element undergoes polarization reversal at a predetermined distance from the center of the piezoelectric element toward its outer edge. Viewed in the direction in which the support, the leaf spring, and the piezoelectric vibrator are aligned, the fourth region is positioned closer to the support than the polarization reversal position. The actuator according to any one of claims 1 to 6.
8. The aforementioned leaf spring is made of metal. The actuator according to any one of claims 1 to 7.