Vibration actuator and optical device

Abstract

To provide a vibration type actuator in which generation of an abnormal sound is suppressed while downsizing is realized.SOLUTION: A vibration type actuator includes a vibration body 11 having a piezoelectric element 111 and an elastic member 112, and a contact body 30 that comes into contact with the vibration body 11. The contact body 30 has a rectangular bar shape in the longitudinal direction of which the vibration body 11 and the contact body 30 relatively move and having a width B and a thickness T which are substantially fixed in the longitudinal direction, and has, in a region that performs friction sliding with respect to the vibration body 11, first and second sections having respective R surfaces of different curvature radiuses formed on an edge portion that is extended in the longitudinal direction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a vibration actuator and an optical device. [Background technology]

[0002] Vibration actuators have features such as the ability to obtain a large thrust, the ability to perform highly accurate positioning, and excellent quietness, and are widely used, for example, to drive focus lenses and image blur correction lenses in imaging devices. In recent years, vibration actuators have also been used as drive sources for lens pan and tilt drive devices in surveillance cameras and network cameras.

[0003] A vibration actuator is a driving device in which a vibrating body and a contact body are in frictional contact with each other, and a thrust (driving force) is obtained by moving the vibrating body and the contact body relatively by exciting a specific vibration in the vibrating body. Therefore, when the vibration actuator is driven, the vibration excited in the vibrating body may cause unnecessary vibration in the contact body, and the unnecessary vibration in the contact body may cause abnormal noise. Therefore, when the vibration actuator is driven, it is desirable to prevent unnecessary vibration from being generated in the contact body.

[0004] Therefore, in order to suppress the occurrence of vibration in the contact body, vibration actuators are often designed so that the drive frequency of the vibrator does not match the resonant frequency of the contact body. However, for example, the contact body constituting a linear drive type vibration actuator often has various natural vibration modes specific to its shape in addition to typical vibrations such as out-of-plane vibration, in-plane vibration, and torsional vibration. In response to this problem, Patent Document 1 proposes a vibration actuator (vibration motor) designed so that the frequencies of all natural vibration modes of the contact body are deviated from the drive frequency by a predetermined value or more. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-67983 A Summary of the Invention [Problem to be solved by the invention]

[0006] In addition to suppressing the generation of the above-mentioned abnormal noise, there is also a strong demand for vibration actuators to be small and lightweight. In order to meet such demands, for example, when the thickness of the contact body is reduced, the resonant frequency of the natural vibration mode of the contact body generally shifts to the low frequency side, and the frequency interval between adjacent orders becomes smaller (narrower). As a result, it becomes difficult to design a system that excludes all natural vibration modes in the vicinity of the drive frequency from the drive frequency band of the vibrator, and unnecessary vibrations may be excited in the contact body under certain drive conditions, resulting in the generation of abnormal noise in the audible range.

[0007] An object of the present invention is to provide a vibration actuator that is miniaturized while suppressing the generation of abnormal noise. [Means for solving the problem]

[0008] A vibration actuator according to the present invention is a vibration actuator including a vibrating body having an electromechanical energy conversion element and an elastic member, and a contact body in contact with the vibrating body, the contact body having a longitudinal direction in which the vibrating body and the contact body move relatively, a rectangular bar shape having a substantially constant width and thickness in the longitudinal direction, and a first section and a second section in which R faces with different radii of curvature are formed on edge portions extending in the longitudinal direction in a region where the contact body makes frictional contact with the vibrating body. The radius of curvature of the first section is larger than the radius of curvature of the second section, and the first section is provided at a position that corresponds to an antinode or a node of a torsional vibration mode of the contact body. It is characterized by: Effect of the Invention

[0009] According to the present invention, it is possible to realize a vibration actuator that is miniaturized and suppresses the generation of abnormal noise. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a linear drive type vibration actuator. [Diagram 2] 1A to 1C are diagrams illustrating vibration forms of typical natural vibration modes of a contact body. [Diagram 3] 2A to 2C are diagrams illustrating the structure of a contact body used in the vibration actuator according to the first embodiment. [Figure 4] 4 is a diagram for explaining a natural vibration mode of each contact body in FIG. 1 and FIG. 3. [Diagram 5] 4 is a schematic diagram showing a vibration form of a torsional vibration having three peaks in the contact body of FIG. 3. FIG. [Figure 6] 4 is a diagram showing a configuration of a modified example of the contact body of FIG. 3. [Figure 7] 7 is a diagram for explaining a change in the resonance frequency of a natural vibration mode that occurs when the contact body in FIG. 6 is used. [Figure 8] 10A to 10C are diagrams illustrating the structure of a contact body used in a vibration actuator according to a second embodiment. [Figure 9] 9A to 9C are diagrams illustrating vibration forms in a representative natural vibration mode of the contact body of FIG. 8. [Figure 10] FIG. 2 is a diagram illustrating a schematic configuration of a lens driving device. [Figure 11] FIG. 2 is an exploded perspective view showing a schematic configuration of a pan-tilt drive device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Compared to conventional vibration actuators, the vibration actuator according to the embodiments of the present invention has a significant feature in the structure of the contact body, but can be configured with no substantial differences in other configurations. Therefore, first, a well-known configuration example of a vibration actuator will be described, and then the contact body, which is a characteristic component of the vibration actuator according to the embodiments of the present invention, will be described.

[0012] 1(a) and (b) are exploded perspective views of a linear drive type vibration actuator 1, with the elements (components) constituting the vibration actuator 1 viewed from different directions in Fig. 1(a) and Fig. 1(b). Fig. 1(c) is a front view of the vibration actuator 1, and Fig. 1(d) is a side view of the vibration actuator 1.

[0013] 1(a) to (d), in order to clarify the correspondence between the figures and for the sake of convenience, an X-axis (X direction), a Y-axis (Y direction), and a Z-axis (Z direction) that are perpendicular to each other are defined as shown in the figures. The directions indicated by the X-direction, the Y-direction, and the Z-direction will be explained together with the explanation of the components of the vibration actuator 1.

[0014] The vibration type actuator 1 has a vibrating body 11, a contact body 12, a holding member 13, a pressure member 14, a guided member 15, a fixing member 16, a screw 17, and a rolling member 18. The vibrating body 11 has a rectangular plate-shaped elastic member 112 and a rectangular plate-shaped piezoelectric element 111, which is an example of an electromechanical energy conversion element. The elastic member 112 has two faces (two planes perpendicular to the Z direction) facing the thickness direction (Z direction) of the elastic member 112, on one of which the piezoelectric element 111 is bonded, and on the other face, two protrusions 112a protruding toward the contact body 12 side are formed at a predetermined interval in the X direction. In addition, held parts 112b extending outward (±X direction) are provided on both ends of the longitudinal direction (X direction) of the elastic member 112.

[0015] For example, the piezoelectric element 111 is made of a piezoelectric ceramic such as PZT (lead zirconate titanate), and the elastic member 112 is made of a metal such as stainless steel. By applying an AC voltage of a predetermined frequency to the piezoelectric element 111, it is possible to excite the vibrating body 11 to vibrate in a predetermined vibration mode, thereby generating an elliptical motion at the tip of the protrusion 112a. Note that the mechanism for generating an elliptical motion at the tip of the protrusion 112a is publicly known, and therefore a detailed description thereof will be omitted here.

[0016] The held portion 112b is adhered and fixed to the holding member 13. In this way, the vibrating body 11 is held by the holding member 13 without impeding the excitation of vibration. The pressure member 14 is, for example, a leaf spring, and presses the holding member 13 toward the contact body 12 by the reaction force of elastic deformation, thereby bringing the protrusion 112a into pressure contact with the contact body 12. The guided member 15 sandwiches the pressure member 14 between itself and the holding member 13, causing the pressure member 14 to elastically deform.

[0017] Two guide grooves 15a extending in the driving direction (X direction) of the vibration actuator 1 are formed in the guided member 15. Two guide grooves 16a extending in the X direction are formed in the fixed member 16 so as to face the two guide grooves 15a of the guided member 15 in the Z direction.

[0018] The contact body 12 has a rectangular bar shape with its longitudinal direction in the X direction and its width (length in the Y direction) perpendicular to the longitudinal direction being greater than its thickness (length in the Z direction). The longitudinal direction of the contact body 12 is the direction in which the vibrating body 11 and the contact body 12 move relative to each other, as described later.

[0019] A hole penetrating in the thickness direction (Z direction) is provided near the end of the contact body 12 in the longitudinal direction. The contact body 12 is fixed to the fixing member 16 by inserting a screw 17 (fastening member) into the hole formed in the contact body 12 and fastening it to the fixing member 16. A cross section of the contact body 12 cut in a plane (YZ plane) perpendicular to the longitudinal direction (X direction) is uniform in the longitudinal direction.

[0020] A spherical rolling member 18 (ball) is sandwiched between a guide groove 15a formed in the guided member 15 and a guide groove 16a formed in the fixed member 16, so that the guided member 15 is held movable only in the X direction relative to the fixed member 16.

[0021] In the vibration actuator 1, when a predetermined vibration is excited in the vibrating body 11 to cause the protrusion 112a to perform an elliptical motion in the ZX plane, a driving force that moves the vibrating body 11 and the contact body 12 relatively in the X direction is generated on the contact surface between the protrusion 112a and the contact body 12. Then, the vibrating body 11, the holding member 13, the pressure member 14, and the guided member 15 move integrally relative to the contact body 12 and the fixed member 16 in the X direction, which is the driving direction.

[0022] FIG. 2 is a diagram for explaining the vibration forms of the representative natural vibration modes of the contact body 12. FIG. 2(a) shows a schematic representation of out-of-plane bending vibration in which an amplitude occurs in the thickness direction (Z direction) of the contact body 12. FIG. 2(b) shows a schematic representation of in-plane bending vibration in which an amplitude occurs in the width direction (Y direction) of the contact body 12. FIG. 2(c) shows a schematic representation of torsional vibration in which an amplitude occurs with the longitudinal axis of the contact body 12 as the axis of rotation. Here, a resonance mode in which the resonance frequency is the smallest among the vibration forms, that is, a resonance mode having one vibration peak, is shown as a representative, but there are higher-order natural vibration modes having multiple peaks on the higher frequency side.

[0023] Next, a vibration actuator according to a first embodiment of the present invention will be described. The vibration actuator according to the first embodiment differs from the vibration actuator 1 shown in Fig. 1 in that a contact body 30 or a contact body 30A, which will be described later, is used as a component instead of the contact body 12 constituting the vibration actuator 1. Therefore, the following description will focus on the configurations of the contact bodies 30 and 30A.

[0024] 3A and 3B are diagrams illustrating the structure of a contact body 30 used in a vibration actuator according to a first embodiment of the present invention. More specifically, Fig. 3A is an external perspective view of the contact body 30. As with the contact body 12, the contact body 30 has a longitudinal direction defined as the X direction, a width direction defined as the Y direction, and a thickness direction defined as the Z direction. As with the contact body 12, the contact body 30 has a square rod shape with a substantially constant width and thickness.

[0025] At the end of the contact body 30 in the longitudinal direction (X direction), a fixing portion 32 is provided for fastening the contact body 30 to the fixing member 16 with a screw 17, and a friction portion 31 is formed between the fixing portions 32 provided at the end of the longitudinal direction. One of the front and back surfaces (a surface (XY plane) perpendicular to the Z direction) of the friction portion 31 becomes a friction sliding surface with respect to the protrusion 112a of the vibrating body 11.

[0026] The friction portion 31 has a first section and a second section in which R surfaces with different radii of curvature are formed on two edge portions on the front side (+Z side) of the four edge portions extending in the longitudinal direction. The first section is provided at approximately the center of the friction portion 31 in the longitudinal direction, and two second sections are provided so as to sandwich the first section in the longitudinal direction.

[0027] FIG. 3(b) is a YZ cross-sectional view (a view showing a cross section perpendicular to the X direction) of the contact body 30 in the first section. FIG. 3(c) is a YZ cross-sectional view of the contact body 30 in the second section. Of the four edges extending in the longitudinal direction of the contact body 30, the shapes of the two edges on the back side (-Z side) are the same between the first section and the second section. On the other hand, of the four edges extending in the longitudinal direction of the contact body 30, the two edges on the front side (+Z side) are different in that the radius of curvature of the first section is relatively larger than that of the second section. That is, the first section has an R surface with a relatively larger radius of curvature than that of the second section. The R surface can be formed by R chamfering processing such as cutting, grinding, and polishing. When the contact body 30 is molded by casting, the R surface can also be formed by a mold.

[0028] The R surface in the first section is formed within a region having a length from the edge portion to ¼ or less of the width B of the contact body 30 (friction portion 31) on the front and back sides (XY plane sides), and a length from the edge portion to ½ or less of the thickness T of the contact body 30 (friction portion 31) on the side side (ZX plane side). The amount of removal by R chamfering in the first section is set to be no more than the maximum amount of removal by C chamfering expected within the aforementioned dimensional limits.

[0029] In the contact body 30, the edge portions where the first section and the second section may be provided are limited to four edge portions extending in the longitudinal direction. In the contact body 30, the R-surfaces with different radii of curvature are provided on two edge portions on the front side, but the R-surfaces with different radii of curvature may be provided on two edge portions on the back side. Also, the R-surfaces with different radii of curvature may be provided on all four edge portions extending in the longitudinal direction. In the contact body 30, the R-surface with a large radius of curvature is provided only at one edge portion, but the R-surface with a large radius of curvature is not limited to this, and may be provided at multiple positions (specifically, two to four positions). Furthermore, in the contact body 30, the radius of curvature of the R-surface in the first section is constant, but the radius of curvature of the R-surface in the first section may be changed in the longitudinal direction. There is a limit to the longitudinal length of the first section in the contact body 30, but this limit will be described later.

[0030] The fixing portion 32 is a portion for fixing the contact body 30 to the fixing member 16 with the screw 17, and is formed in a U-groove shape in the contact body 30. The contact body 30 is fixed to the fixing member 16 by passing the screw 17 through the U-groove in the thickness direction and fastening it to the fixing member 16. In the contact body 30, the fixing portion 32 and the friction portion 31 are continuous structures with the same thickness and width, but the thickness and shape of the fixing portion 32 are not limited to this. For example, the fixing portion 32 may have a different thickness and width from the friction portion 31, or a through hole may be provided instead of the U-groove shape as in the contact body 12, and further, a fixing means other than fastening with the screw 17 may be used.

[0031] Next, the technical effect of the contact body 30 having the first section will be described. Fig. 4(a) is a diagram for explaining the natural vibration mode of the contact body 12. Fig. 4(b) is a diagram for explaining the natural vibration mode of the contact body 30. In Figs. 4(a) and 4(b), the horizontal axis indicates the number of peaks in the three types of vibration forms (out-of-plane vibration, in-plane vibration, and torsional vibration) described with reference to Fig. 2, and the vertical axis indicates the resonance frequency of each natural vibration mode. Note that the reason why only the three types of vibration forms, out-of-plane vibration, in-plane vibration, and torsional vibration, are considered is that in the rod-shaped contact bodies 12 and 30 having four edges extending in the longitudinal direction, the vibration forms to be considered that appear in the low frequency band are narrowed down to these three types.

[0032] It is well known that for a beam of constant length, the resonant frequency increases as the number of vibration peaks increases, and therefore, for the contact bodies 12 and 30, the resonant frequency increases as the number of peaks increases in each of the vibration modes of out-of-plane vibration, in-plane vibration, and torsional vibration.

[0033] The contact body 12 does not have a section corresponding to the first section provided in the contact body 30. Therefore, as shown in Fig. 4(a), the resonance frequency of the vibration mode of torsional vibration (the resonance frequency with three peaks) is included in the driving frequency band of the vibrating body 11. In contrast, the contact body 30 has a first section in which an R-face with a large radius of curvature is formed, so that the resonance frequency with three peaks in the torsional vibration is shifted to the high frequency side and is outside the driving frequency band of the vibrating body 11.

[0034] 4(a) and (b), it is clear that there is almost no change in the resonant frequency of the out-of-plane vibration, and the change in the resonant frequency of the in-plane vibration is slight. Therefore, by providing the first section in the contact body, it becomes possible to selectively move the resonant frequency of the torsional vibration away from the driving frequency band of the vibrating body 11, and as a result, it becomes possible to suppress the generation of abnormal noise when the vibration actuator is driven.

[0035] The reason why the resonance frequency of the torsional vibration changes greatly while there is almost no change in the resonance frequency of the in-plane vibration and the out-of-plane vibration will be described with reference to FIG. 5. FIG. 5 is a schematic diagram showing the vibration form of the torsional vibration with three peaks in the contact body 30. The apex of the peak of the torsional vibration exists in the first section of the contact body 30. In this case, the mass of the peak part of the torsional vibration is reduced by the amount of the edge part removed by forming the R surface with a large radius of curvature in the first section, so that the resonance frequency becomes high. In addition, the apex of the peak in the torsional vibration with one peak also exists in the first section. Therefore, the resonance frequency of the torsional vibration with one peak also becomes high. In other words, the resonance frequency of the torsional vibration with an odd number of peaks becomes high by providing the first section with the R surface with a large radius of curvature formed in the contact body 30.

[0036] On the other hand, when the number of peaks in the torsional vibration is an even number, the node of the torsional vibration exists within the first section. In this case, since the first section is provided with an R surface with a large radius of curvature, there is no part with large distortion in the torsional vibration, and the resonant frequency where the number of peaks in the torsional vibration is an even number is low. In other words, since the first section is far from the neutral axis of the torsional vibration and has a large effect on the second moment of area, the resonant frequency is low due to the mass removed by providing an R surface with a large radius of curvature.

[0037] Next, the restriction on the length of the first section in the longitudinal direction will be described. As described above, when the first section is provided at the position of the antinode of the vibration, the effect of shifting the resonance frequency of the vibration to the higher frequency side is obtained. Therefore, the length of the first section in the longitudinal direction must be set between the nodes of the vibration of the order to be removed from the driving frequency band, that is, to a length of 1 / 2 wavelength or less. In the case of the contact body 30, it is desirable that the length of the first section in the longitudinal direction is set to a length of 1 / 2 wavelength or less of a torsional vibration with three peaks.

[0038] For out-of-plane and in-plane vibrations, the provision of the first section on the R surface with a large radius of curvature eliminates some of the areas with large distortion, and so the resonant frequency changes by the same mechanism as for torsional vibration. However, the effect on the second moment of area caused by the first section in out-of-plane and in-plane vibrations is minor.

[0039] As explained above, in the contact body 30, by providing the first section having an R surface with a large radius of curvature in the edge portion extending in the longitudinal direction, the resonance frequency of the torsional vibration can be controlled without affecting the resonance frequencies of the out-of-plane vibration and the in-plane vibration. In this way, it becomes possible to remove the resonance frequency of the torsional vibration from the driving frequency band of the vibrating body 11, thereby making it possible to suppress the generation of abnormal noise.

[0040] Next, modified examples of the contact body 30 will be described. Fig. 6(a) is a diagram for explaining the structure of the contact body 30A. Fig. 6(a) is an external perspective view of the contact body 30A. Fig. 6(b) is a YZ cross-sectional view of the contact body 30A in the first section. Fig. 6(c) is a YZ cross-sectional view of the contact body 30 in the second section.

[0041] Contact body 30A differs from contact body 30 in that a step S is provided to narrow the width in the first section, but the other configurations are the same as contact body 30. Therefore, in Fig. 6, the first section is clearly shown and the reference numerals and the like of other parts are omitted, and the following mainly describes the first section having the step S.

[0042] The first section is narrower than the second section because a step is formed on the Y-direction side surface by removing the Y-direction side surface to a certain depth. Also, in the first section, an R-surface is formed with a larger radius of curvature than the second section within the range where the step S is provided in the longitudinal direction.

[0043] FIG. 7 is a diagram for explaining the change in the resonant frequency of the natural vibration mode that occurs when the contact body 30A is used in the vibration type actuator. In FIG. 7, the resonant frequency of each vibration mode in a contact body that does not have a first section (a contact body having the same structure as the contact body 12 in FIG. 1) is plotted. Here, the resonant frequency of the torsional vibration and the in-plane vibration with two peaks falls into the driving frequency band. In the explanation of FIG. 4, the influence of the R surface with a large radius of curvature on the second moment of area of ​​the in-plane vibration is minor. In contrast, in the contact body 30A, by providing the step S on the width direction side, the area with large distortion is not on one surface, so that the second moment of area of ​​the in-plane vibration mode is greatly influenced and the resonant frequency of the in-plane vibration is shifted to the low frequency side. In this way, the resonant frequency of the in-plane vibration with two peaks can be shifted to the low frequency side and moved out of the driving frequency band, as shown by the arrow in FIG. 7.

[0044] In this way, by providing the first section, it is possible to selectively remove the resonance frequencies of the torsional vibration and the in-plane vibration from the driving frequency band, and as a result, it is possible to suppress the generation of abnormal noise. In the contact body 30A, the width of the first section is made narrower than the width of the second section by providing the step S, but conversely, by making it wider, it is also possible to selectively remove the resonance frequencies of the torsional vibration and the in-plane vibration from the driving frequency band.

[0045] Next, a contact body used in a vibration actuator according to a second embodiment of the present invention will be described. The vibration actuator according to the second embodiment is a vibration actuator that performs rotational driving as described later with reference to Fig. 11, and includes a contact body having a circular ring shape. The schematic configuration of the vibration actuator according to the second embodiment will be described later with reference to Fig. 11, and here, the structure of the contact body having a circular ring shape will be described in detail.

[0046] 8(a) is an external perspective view of a contact body 60 used in a vibration actuator according to a second embodiment of the present invention. The contact body 60 is annular, and has an inner peripheral portion and an outer peripheral portion with different thicknesses. The inner peripheral portion of the contact body 60 is a portion for connecting to a rotating body (not shown), and is thinner than the outer peripheral portion. The outer peripheral portion has a width B in the radial direction and a thickness T, and either the front or back surface parallel to the radial direction (thickness direction) serves as a friction sliding surface with the vibrating body 11 (not shown).

[0047] A plurality of first sections are formed at equal intervals in the circumferential direction on the outer periphery of the contact body 60, and a second section is formed between adjacent first sections. The first section is a section in which a rounded surface with a large radius of curvature is formed on the outer peripheral edge portion, and the second section is a section in which a rounded surface with a relatively larger radius of curvature than that of the first section is formed. FIG. 8(b) is a cross-sectional view taken along the arrow AA in FIG. 8(a), and shows a cross section of the first section. In the contact body 60, the rounded surface with a large radius of curvature is provided on both the outer peripheral edge portions of the front and back sides. Note that the edge portions on which the rounded surface with a large radius of curvature may be formed are limited to the outer peripheral edge portions on the front and back sides, and are not provided on the edge portions on the inner side of the outer peripheral portion. Here, the rounded surface with a large radius of curvature is provided on both the outer peripheral edge portions on the front and back sides, but may be provided on one of the outer peripheral edge portions.

[0048] As shown in Fig. 8(b), the R surface in the first section of the contact body 60 is formed within a region that is ¼ or less of the width B from the outer peripheral edge on the front and back surfaces, and ½ or less of the thickness T from the outer peripheral edge on the outer peripheral side surface. The amount of removal by the R chamfer in the first section is set to be no more than the maximum amount of removal by the C chamfer that is assumed within the range of the dimensional restrictions mentioned above. The rest of the configuration of the first section is similar to that of the first section of the contact body 30, so a description thereof will be omitted.

[0049] 9 is a diagram for explaining the vibration form in a representative natural vibration mode of the contact body 60. Fig. 9(a) and (b) are schematic diagrams showing out-of-plane bending vibration in which an amplitude occurs in the axial direction of the contact body 60. Fig. 9(c) and (d) are schematic diagrams showing in-plane bending vibration in which an amplitude occurs in the radial direction of the contact body 60. Fig. 9(e) and (f) are schematic diagrams showing torsional vibration in which an amplitude occurs in a torsion around the circumferential axis of the contact body 60 as the axis of rotation. Here, a resonance mode having six vibration peaks is shown as a representative, but natural vibration modes with different numbers of peaks exist on both the lower frequency side and the higher frequency side.

[0050] The vibration modes occurring in the contact body 60 are characterized in that, even if they have the same number of peaks, they have two modes, generally called SIN mode and COS mode. Of these two modes, one mode has the peak position within the first section, and the other mode has the node position within the first section. In this case, the former has a higher resonant frequency of torsional vibration because the mass at the position of the vibration peak is reduced. Conversely, the latter has a lower resonant frequency of torsional vibration because the position where the vibration distortion becomes large is removed. Therefore, a difference occurs in the resonant frequency of the SIN mode and the COS mode, which are torsional vibration modes having the same number of peaks.

[0051] It is known that in a vibration actuator that frictionally drives a ring-shaped contact body, abnormal noise occurs when a traveling wave of a specific vibration mode is excited in the contact body. In contrast, in the contact body 60, a difference occurs in the resonance frequencies of the two vibration modes, SIN mode and COS mode, which form traveling waves, so that the vibration energy from the vibrator does not lead to the generation of traveling waves, and as a result, the generation of abnormal noise can be suppressed. Note that the reason why forming an R surface with a large radius of curvature does not have a significant effect on the resonance frequencies of the out-of-plane vibration and in-plane vibration modes is the same as for the contact body 30.

[0052] In this way, in the annular contact body 60, by providing the first section in which the R surface with a large radius of curvature is formed on the outer peripheral edge, the resonance frequency of the torsional vibration can be controlled without substantially affecting the out-of-plane vibration and the in-plane vibration, and as a result, the generation of abnormal noise can be suppressed.

[0053] Next, an example of an optical device using a vibration actuator will be described. Fig. 10(a) is a diagram showing a schematic configuration of a lens driving device 40 using a vibration actuator. Fig. 10(b) is a front view of the lens driving device 40. Fig. 10(c) is a side view of the lens driving device 40.

[0054] The lens driving device 40 in Fig. 10 uses the same components as the vibration actuator 1 in Fig. 1 in terms of function, and therefore the vibration actuators are given the same reference numerals and detailed descriptions are omitted, and their configuration is simply shown in Fig. 10. The lens driving device 40 has the vibration actuator 1, an optical lens 41 (optical component), a lens holding member 42, and a guide member 43.

[0055] The optical lens 41 is, for example, a focus lens used in a lens barrel of an imaging device. The lens holding member 42 holds the optical lens 41. The guide member 43 is inserted into a hole provided in the lens holding member 42, and in this state, both ends of the guide member 43 are fixed in the lens barrel substantially parallel to the optical axis O of the optical lens 41. As a result, the optical lens 41 is guided by the guide member 43 to be movable in the optical axis direction.

[0056] The lens holding member 42 is provided with a fitting portion 42b. Furthermore, the guided member 15 of the vibration actuator 1 is provided with a fitting protrusion 15b that fits into the fitting portion 42b. The fixed member 16 is fixed to a predetermined position within the lens barrel so that the fitting protrusion 15b fits into the fitting portion 42b and the moving direction of the guided member 15 is approximately parallel to the optical axis O. Therefore, by driving the vibration actuator 1 to move the guided member 15 in the optical axis direction, the optical lens 41 can be moved in the optical axis direction.

[0057] In a lens barrel equipped with such a lens driving device 40, there is a strong demand for miniaturizing the vibration actuator in order to realize a miniaturization of the lens barrel. As described above, miniaturization of the vibration actuator may cause the resonant frequency of the natural vibration mode of the contact body to fall within the driving frequency band, which may result in the generation of abnormal noise in the audible range. To address this problem, the above-described configuration of the contact body 30 is applied to the contact body constituting the vibration actuator, thereby making it possible to reduce the thickness and size of the contact body while suppressing the generation of abnormal noise, thereby realizing the miniaturization of the vibration actuator.

[0058] 11 is an exploded perspective view of a pan-tilt driving device 50 using a vibration actuator. The imaging unit 57 supports a lens barrel 58 incorporating various optical components such as lenses and an aperture so that the lens barrel 58 can rotate about a tilt rotation axis TN. The imaging unit 57 is a driven part of the pan-tilt driving device 50, and is supported by an intermediate cover 59 so as to be rotatable integrally with the lens barrel 58 around the pan rotation axis PN. The connecting member 56 is connected to a contact body 60 by a screw 55, thereby connecting the contact body 60 and the imaging unit 57. The intermediate cover 59 is fixed to a base 54.

[0059] In FIG. 11, the overall configuration of the vibration actuator 1 is not shown. The vibration actuator 1 is held by an actuator support substrate 51, which is fixed to a base 54. The two protrusions 112a of the vibration body 11 contact the surface of the contact body 60 on the -Y side. The driving force of the vibration actuator acts in the tangential direction of the contact body 60, rotating the contact body 60 around the pan rotation axis PN, and as a result, the imaging unit 57 also rotates around the pan rotation axis PN. The contact body 60 holds a scale 53 for position detection. The scale 53 is disposed on a surface facing a position detection sensor 52 fixed to the actuator support substrate 51, and the rotation angle of the contact body 60 can be obtained by the position detection sensor 52. Note that the actuator that rotates the lens barrel 58 around the tilt rotation axis TN can be an actuator equivalent to the actuator that rotates the imaging unit 57 around the pan rotation axis PN.

[0060] For the same reasons as in the lens driving device 40, the pan-tilt driving device 50 can also suppress the generation of abnormal noise and achieve a reduction in the size of the vibration actuator.

[0061] Although the present invention has been described in detail above based on the preferred embodiments, the present invention is not limited to these specific embodiments, and various forms within the scope of the gist of the present invention are also included in the present invention. Furthermore, each of the above-mentioned embodiments merely shows one embodiment of the present invention, and each embodiment can be appropriately combined. [Explanation of symbols]

[0062] 11 Vibration body 30,30A,60 Contact body 31 Friction part 40 Lens drive unit 50 Pan-tilt drive device 111 Piezoelectric element 112 Elastic member

Claims

1. a vibrating body having an electromechanical energy conversion element and an elastic member; a contact body that contacts the vibrating body, the contact body has a rectangular bar shape with a longitudinal direction corresponding to a direction in which the vibrator and the contact body move relative to each other, and a substantially constant width and thickness in the longitudinal direction; and the contact body has a first section and a second section in which R surfaces with different radii of curvature are formed on edge portions extending in the longitudinal direction in a region where the contact body makes frictional contact with the vibrator; A vibration actuator characterized in that the radius of curvature of the first section is larger than the radius of curvature of the second section, and the first section is located at a position that is an antinode or node of a torsional vibration mode of the contact body.

2. a vibrating body having an electromechanical energy conversion element and an elastic member; a contact body that contacts the vibrating body, the contact body has a circular ring shape with a radial width and an axial thickness that are each substantially constant, a surface parallel to the radial direction is a friction sliding surface with respect to the vibration body, and has a first section and a second section in which R surfaces with different radii of curvature are formed on an outer peripheral edge portion, A vibration actuator characterized in that the radius of curvature of the first section is larger than the radius of curvature of the second section, and the first section is located at a position that is an antinode or node of a torsional vibration mode of the contact body.

3. 3. The vibration actuator according to claim 1, wherein the contact body has a plurality of the first sections.

4. A vibration actuator as described in any one of claims 1 to 3, characterized in that the length of the first section in the direction in which the contact body moves relative to the vibrating body is less than or equal to half the wavelength of the torsional vibration mode of the order closest to the driving frequency band of the vibrating body.

5. 5. The vibration actuator according to claim 4, wherein the width of the first section is smaller than the width of the second section.

6. The vibration actuator according to claim 5, characterized in that in the first section, in the direction in which the contact body moves relative to the vibrating body, the length of the region in which the R-surface is formed is shorter than the length of a region having a width smaller than that of the second section.

7. A vibration actuator as described in any one of claims 1 to 6, characterized in that the R surface of the first section is formed within a region that is a length of less than 1 / 4 of the width from the edge portion on a surface parallel to the width direction, and a length of less than 1 / 2 of the thickness from the edge portion on a surface parallel to the thickness direction, in a cross section perpendicular to the direction in which the contact body moves relative to the vibrating body.

8. A vibration type actuator according to any one of claims 1 to 7, and an optical component driven by the vibration actuator.

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