Vibration actuator, and optical and electronic devices having the same

Abstract

To provide a vibration type actuator which is more miniaturized than a conventional actuator while suppressing revolution of a vibrator and a contact body with a relative movement direction (a prescribed direction) as an axis in the same way as a conventional way.SOLUTION: A vibration type actuator has: a vibrator which has an elastic body and an electric-mechanical energy conversion element; a contact body which contacts with the elastic body and has a first guide formed so as to extend in a predetermined direction; a driven guide member which has a second guide formed so as to extend in the predetermined direction and is driven with the vibrator by vibration generated by voltage applied to the electric-mechanical energy conversion element; two balls which is supported by the first guide and the second guide in a rolling manner in the predetermined direction; and a base to which the contact body is fixed. The base has a third guide formed so as to extend in the predetermined direction. The guide member has a fitting projecting part fitted to the third guide.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] There are known various configurations of vibration wave motors (vibration type actuators) using electromechanical energy conversion elements such as piezoelectric elements. For example, there is a vibration wave motor having a driven body, a vibrator in which two protrusions are provided on the surface of a flat elastic body and a piezoelectric element is bonded to the back surface of the elastic body, and a pressure member for pressurizing and contacting the two protrusions with a contact body. Here, the back surface of the elastic body refers to the surface on which the protrusions described below are not formed. In the following, the driven body is also referred to as a "contact body."

[0003] In this vibration wave motor, a predetermined AC voltage (hereinafter also referred to as "driving voltage") is applied to the electromechanical energy conversion element to generate elliptical or circular motion at the tips of the two protrusions within a plane including the direction connecting the two protrusions and the protruding direction of the protrusions. As a result, the contact body receives a frictional driving force from the two protrusions (vibrators), and the vibrator and the contact body can be moved relatively (hereinafter also referred to as "relative movement") in the direction connecting the two protrusions.

[0004] In order to miniaturize the optical and electronic devices that incorporate this vibration wave motor, it is necessary to miniaturize the vibration wave motor itself. Linear motion type vibration wave motors often use a guide means consisting of a rolling ball that guides the moving body in the relative movement direction while receiving pressure, and a V-groove.

[0005] In Patent Document 1, only two rolling balls arranged side by side in the direction of relative movement are used as the rolling balls.

[0006] However, when only two rolling balls are used, the oscillator or contact body is allowed to rotate around the axis of the relative movement direction. Therefore, in Patent Document 1, a guide bar and a long hole are provided in addition to the rolling balls in order to restrict the rotation of the contact body around the axis of the relative movement direction (see paragraphs 0017 and 0036 of Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2019-140764 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the vibration wave motor disclosed in Patent Document 2, the effect of miniaturization obtained by using only two rolling balls is diminished by the increased number of parts (guide bars). The present invention has been made in consideration of such problems, and aims to provide a vibration type actuator that is smaller than conventional ones while suppressing the rotation of the vibrator and contact body around the axis of the relative movement direction (predetermined direction) as in the conventional ones. [Means for solving the problem]

[0009] In order to solve the above problems, a vibration actuator of the present invention includes a vibrator having an elastic body and an electromechanical energy conversion element, a contact body having a first guide in contact with the elastic body and extending in a predetermined direction; A second guide extending in the predetermined direction is provided, and the transducer is moved together with the transducer by vibration generated by a voltage applied to the electro-mechanical energy conversion element. , relative to the contact body in the predetermined direction A driven guide member that is driven; two balls sandwiched between the first guide and the second guide so as to be rollable in the predetermined direction; A base to which the contact body is fixed, The base is in the predetermined direction. By The driven guide member has a fitting protrusion that fits with the third guide. death, The fitting protrusion is configured to restrict rotation of the vibrator and the contact body in a rotation direction relative to the predetermined direction. It is characterized by the above. Effect of the Invention

[0010] It is possible to provide a vibration type actuator that is smaller in size than conventional actuators while suppressing the rotation of the vibrator and the contact body about the axis of the relative movement direction (predetermined direction) as in conventional actuators. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is an exploded perspective view of a vibration wave motor according to a first embodiment of the present invention. [Diagram 2] 1A is a perspective view of a vibration wave motor according to a first embodiment of the present invention, FIG. 1B is a cross-sectional view taken along a YZ plane, and FIG. [Diagram 3] FIG. 2 is a vibration mode diagram in the first embodiment of the present invention. [Figure 4] 2 is a YZ cross-sectional view of the vicinity of a ball of the vibration wave motor according to the first embodiment of the present invention. FIG. [Diagram 5] 4 shows a second guide member in the first embodiment of the present invention. [Figure 6] 13A and 13B are a top view and a block diagram showing a schematic configuration of an imaging device using a vibration wave motor according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Example 1 This embodiment is an example in which the present invention is applied to a (linear type) oscillatory wave motor, and its details will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is an exploded perspective view of an oscillatory wave motor 1 in the first embodiment of the present invention, and Fig. 2 is an assembly diagram. Here, the relative movement direction (predetermined direction) of the oscillator 2 is defined as the X direction, the pressure direction as the Z direction, and the direction perpendicular to the X direction and the Z direction as the Y direction.

[0013] The elastic body 3 has a rectangular main body 3c and a plurality of (here, 2 locations x 2 = 4) extending portions 3b extending from a plurality of positions (here, 2 locations) in the X direction of the main body 3c. It can also be said that the plurality of (here, 4) extending portions 3b protrude from a plurality of positions (here, 4 locations) of the main body 3c that are different in the X direction of the main body 3c and in the direction perpendicular to the X direction and the Z direction.

[0014] A piezoelectric element 4, which is an electrical-mechanical energy conversion element, is fixed to the elastic body 3 with adhesive or the like, and a flexible printed circuit board 5 (cable) is further fixed to the piezoelectric element 4 on the side opposite the elastic body 3, forming the vibrator 2. The piezoelectric element 4 and the flexible printed circuit board 5 (cable) are fixed using an anisotropic conductive paste or anisotropic conductive film that allows electricity to flow only in the Z direction.

[0015] The elastic body 3 is preferably made of a material with low vibration damping, such as metal or ceramics. The elastic body 3 may be manufactured by forming the protrusion 3a integrally therewith by press molding or cutting, or it may be manufactured separately and then fixed by welding or adhesive. The elastic body 3 may have a plurality of protrusions 3a as in this embodiment, or may have only one protrusion.

[0016] Lead zirconate titanate is used for the piezoelectric element 4. Alternatively, lead-free piezoelectric materials such as barium titanate and bismuth sodium titanate may be used as the main component. Electrode patterns (not shown) are formed on both sides of the piezoelectric element 4, and power is supplied from a flexible printed circuit board 5 (cable).

[0017] Below the vibrator 2, there is provided a node presser 6 (hereinafter, NP), which is a holding member that applies pressure to and holds the vibrator 2. The flexible printed circuit board 5 (cable) is fixed to a flexible base 6b of the NP6 (holding member) with double-sided tape or the like. Meanwhile, above the vibrator 2, there is provided a friction member 8(), which is one of the components (part of the contact body) that make up the contact body. The pressure spring 7 (pressure member) provided between the NP6 (holding member) and the second guide member 12 (driven guide member) presses and contacts the protrusion 3a of the elastic body 3 in the Z direction. The pressure spring is a tension coil spring, but the coil shape is simply illustrated as a cylinder.

[0018] The second guide member 12 (driven guided member) is provided with an engagement portion 12b, which is engaged with NP6 (holding member), and therefore allows pressure to be applied in the Z direction while allowing them to move together in the X direction. An output is transmitted to the outside by an output transmission portion 6d provided on NP6 (holding member).

[0019] The contact body 8 is fixed to the first guide member 10 (fixed guide member), which is one of the components constituting the contact body (part of the contact body), by the adhesive force of the rubber 9, which is one of the components constituting the contact body (part of the contact body). The rubber 9 also plays a role in vibration damping, making it difficult for the vibration from the vibrator 2 to be transmitted to the first guide member 10 (fixed guide member). The contact body 8, the second guide member 10 (fixed guide member), and the rubber 9 may be fixed by adhesive or screws. The contact body 8 is made of a highly wear-resistant metal, ceramic, resin, or a composite material thereof. In particular, a material obtained by nitriding stainless steel, such as SUS420J2, is preferable from the viewpoint of wear resistance and mass production. The first guide member 10 (fixed guide member) is fixed to the base 14, which is a fixed member, by screws 13.

[0020] Next, the vibration mode excited in the vibrator 2 will be described with reference to Fig. 3. In this embodiment, an AC voltage is applied to the piezoelectric element 3 through a flexible printed circuit board 5 (cable), exciting standing waves (out-of-plane bending vibrations) that are out of phase with each other in the vibrator 2, and generating a vibration that is a composite of these out-of-plane bending vibrations.

[0021] Mode A, the first vibration mode, is a primary out-of-plane bending vibration mode in which two nodes appear parallel to the X direction, which is the longitudinal direction of the vibrator 2. Vibration in mode A displaces the two protrusions 3a in the Z direction, which is the pressure direction. Mode B, the second vibration mode, is a secondary out-of-plane bending vibration mode in which three nodes appear approximately parallel to the Y direction, which is the short-side direction of the vibrator 2. Vibration in mode B displaces the two protrusions 3a in the X direction.

[0022] By combining the vibrations of these modes A and B, the two protrusions 3a perform elliptical or circular motion in the XZ plane. By bringing the contact body 8 into pressure contact with the protrusions 3a, a frictional force is generated in the X direction, generating a driving force (thrust) that moves the vibrator 2 and the contact body 8 relatively. In this embodiment, since the contact body 8 is fixed to the base 14 as described above, the vibrator 2 moves in the X direction.

[0023] In order to efficiently drive the oscillatory wave motor 1, it is necessary to support the oscillator 2 without impeding the vibration (displacement) of the two vibration modes excited in the oscillator 2, and for this purpose, it is desirable to support the vicinity of the nodes of these two vibration modes. For this reason, two contact protrusions 6a are provided on the holding portion 6c (protrusion) of the NP6 (holding member) in order to pressurize and hold the common node of the two vibration modes excited in the oscillator 2. In addition, by positioning the oscillator 2 with the positioning pin 6c (protrusion) provided on the NP6 (holding member), it is possible to bring the two contact protrusions 6a into contact with the vicinity of the nodes of the two vibration modes, respectively.

[0024] Furthermore, the contact protrusions 6a not only pressurize the vibrator 2, but also hold the vibrator 2 in the X and Y directions by frictional force. Since the maximum value of the static frictional force between the contact protrusions 6a and the vibrator 2 is always greater than the reaction force that the vibrator 2 receives when the contact body 8 is driven, the vibrator 2 does not move relative to the NP6 (holding member). This allows for precise driving.

[0025] Here, the guide mechanism of the present invention will be described with reference to FIG. 4. FIG. 4 is a YZ cross-sectional view centered on the ball 11. The first guide member 10 (fixed guide member) is provided with two rolling grooves 10a (first guides). The second guide member 12 (driven guided member) is provided with two rolling grooves 12a (second guides). The two balls 11 are sandwiched between the rolling grooves 10a (first guide) and the rolling grooves 12a (second guides) so as to be capable of rolling in a relative movement direction (predetermined direction). In this way, when the vibration wave motor 1 is driven, the balls roll in the rolling grooves (guides), so that the vibrator 2, NP6 (holding member), and the second guide member 12 (driven guided member) can move smoothly in the X direction.

[0026] The materials for the first guide member 10 (fixed guide member) and the second guide member 12 (driven guide member) need to be hard since they are subjected to pressure in their respective rolling grooves (guides), and from the viewpoint of workability, metal, especially stainless steel, is preferable. When viewed from the direction of pressure application by the pressure member 7, the center of pressure applied by the elastic body 3 (two protrusions 3a) in the contact body 8 is between the two balls. The center of pressure is the point of action of the resultant force of pressure applied to a surface.

[0027] Next, we will describe the advantages of using two balls. If the guide section is formed with a rolling groove (guide) and three balls, it will naturally be larger in the Y direction. Also, to prevent the balls from leaving the groove due to the influence of the driving reaction force from the pressure force, the two balls must be separated, but this distance is shorter with two balls than with three, so it is also possible to make the device smaller in the X direction.

[0028] These balls 11 and rolling grooves 10a (first rolling groove) and 12a (second rolling groove) provide freedom in the X direction while restricting the Y and Z directions, rotation around the Y axis, and rotation around the Z axis, but rotation around the X axis with ball 11 as the center point is permitted.

[0029] For this reason, in this embodiment, the rotation around the X-axis is restricted by fitting the fitting groove 14c (third guide) provided on the base 14 and the tilt regulating portion 12c (fitting protrusion) provided on the second guide member with a loose fit, that is, with a predetermined play. The base 14 is composed of two fixing portions 14a provided with screw holes and positioning pins for fixing the first guide member 10 (fixed guide member), holes for fixing the base 14 to the outside, and a connecting portion 14b connecting them. The fitting groove 14c (third guide) is formed in a part of this connecting portion 14b along the X-direction. The base 14 is made of resin from the viewpoints of workability and slidability.

[0030] In order to drive the vibration wave motor 1 smoothly, a clearance, that is, a gap, is provided between the fitting groove 14c (third guide) and the tilt regulating portion 12c (fitting protrusion). However, if this gap is too large, the vibrator 2 will tilt with respect to the contact body 8, and the motor performance will decrease. Therefore, the size of the gap in the Z direction between the fitting groove 14c (third guide) and the tilt regulating portion 12c (fitting protrusion) is set so that the angle between the surface of the contact body 8 that contacts the vibrator 2 (dashed line P in the figure) and the upper surface of the vibrator 2 (dashed line Q in the figure) does not exceed 2°. In addition, in order to reduce loss due to sliding and sliding noise, a lubricant such as grease is applied to the fitting groove 14c (third guide).

[0031] The size of the inclination regulation portion 12c (fitting protrusion) in the X direction is preferably 0.3 mm to 2.0 mm, since if it is too small, the rigidity decreases, and if it is too large, the precision required for loose fitting increases.

[0032] A flexible printed circuit board 5 (cable) is fixed to this connecting portion 14. The connecting portion 14 also functions to accommodate the curved portion of the flexible printed circuit board 5 (cable) that moves while curving as the vibration wave motor 1 is driven. Therefore, no additional space is required by providing the fitting groove 14c (third guide). Also, since the base 14 is made by resin molding, the increase in cost due to the addition of the fitting groove 14c (third guide) is negligible.

[0033] On the other hand, when the tilt regulating portion 12c (fitting convex portion) is formed by press molding when the second guide member 12 (driven guide member) is manufactured, the cost increase due to the addition of the tilt regulating portion 12c (fitting convex portion) is also negligible. As described above, the rotation around the X-axis can be regulated without reducing the effect of the merit of the miniaturization of the vibration wave motor by using two rolling balls, and without adding new parts, and it is possible to provide a small vibration wave motor with stable performance. That is, it is possible to provide a vibration type actuator that is smaller than the conventional one while suppressing the rotation of the vibrator and the contact body about the axis of the relative movement direction (predetermined direction) as in the conventional one. Note that, in the vibration wave motor of the present invention, the configuration of the contact body is not limited to the above configuration. In the above configuration, the contact body has a friction member, rubber, and a first guide member, but these may be formed integrally or separately. In addition, whether these are formed integrally or separately, if a decrease in the vibration damping effect is acceptable, the rubber may be omitted from the above configuration.

[0034] In addition, in the vibration wave motor of the present invention, the method (driving method) of generating elliptical or circular motion on the contact surface is not limited to the above method (driving method). Specifically, it is not limited to the driving method of generating elliptical and circular motion on the contact surface by combining a vibration mode that displaces the contact surface in the moving direction of the contact body and a vibration mode that displaces the contact surface in the pressure direction. For example, vibrations of bending vibration modes different from those described above may be combined. Also, vibrations of a longitudinal vibration mode that expands and contracts the elastic body in the longitudinal direction may be combined with vibrations of a bending vibration mode. In other words, any driving method may be used as long as it has a common node for pressure application and retention.

[0035] Example 2 A vibration wave motor (vibration type actuator) can be used, for example, for driving lenses in an imaging device (optical equipment, electronic device). As an example, an imaging device (optical equipment, electronic device) that uses a vibration wave motor (vibration type actuator) to drive a lens arranged in a lens barrel will be described. Also, an imaging device (optical equipment, electronic device) that uses a vibration wave motor (vibration type actuator) to drive an imaging element arranged in a camera body will be described.

[0036] FIG. 6(a) is a top view showing a schematic configuration of an imaging device 700 (optical device, electronic device). The imaging device 700 includes a camera body 730 (optical device, electronic device) equipped with an imaging element 710 and a power button 720. The imaging device 700 also includes a lens barrel 740 (optical device, electronic device) having a first lens group (not shown), a second lens group 320, a third lens group (not shown), a fourth lens group 340, and vibration wave motors 620 and 640. The lens barrel 740 is replaceable as an interchangeable lens, and a lens barrel 740 suitable for a subject to be photographed can be attached to the camera body 730. In the imaging device 700, the second lens group 320 and the fourth lens group 340 are driven by the two vibration wave motors 620 and 640, respectively. The imaging element 710 is also driven by the vibration wave motor 650. It should be noted that only one or two of the second lens group 320, the fourth lens group 340, and the image sensor 710 may be driven.

[0037] Although the detailed configuration of the vibration wave motor 620 is not shown, the vibration wave motor 620 has a vibration wave motor (vibration type actuator) and a drive circuit for the vibration wave motor (vibration type actuator). The rotor 211 is disposed in the lens barrel 740 so that the radial direction is substantially perpendicular to the optical axis. In the vibration wave motor 620, the rotor 211 is rotated around the optical axis, and the rotation output of the contact body is converted into linear motion in the optical axis direction via a gear or the like (not shown), thereby moving the second lens group 320 in the optical axis direction. The vibration wave motor 640 has a configuration similar to that of the vibration wave motor 620, and moves the fourth lens group 340 in the optical axis direction.

[0038] 6(b) is a block diagram showing a schematic configuration of the imaging device 700. The first lens group 3a0, the second lens group 320, the third lens group 330, the fourth lens group 340, and the light amount adjustment unit 350 are arranged at predetermined positions on the optical axis inside the lens barrel 740. Light that passes through the first lens group 3a0 to the fourth lens group 340 and the light amount adjustment unit 350 forms an image on the imaging element 710. The imaging element 710 converts the optical image into an electrical signal and outputs it, and the output is sent to the camera processing circuit 750.

[0039] The camera processing circuit 750 performs amplification, gamma correction, and the like on the output signal from the image sensor 710. The camera processing circuit 750 is connected to the CPU 790 via an AE gate 755, and is also connected to the CPU 790 via an AF gate 760 and an AF signal processing circuit 765. The video signal that has been subjected to a predetermined process in the camera processing circuit 750 is sent to the CPU 790 via the AE gate 755, the AF gate 760, and the AF signal processing circuit 765. The AF signal processing circuit 765 extracts high frequency components from the video signal to generate an evaluation value signal for autofocus (AF), and supplies the generated evaluation value to the CPU 790.

[0040] The CPU 790 is a control circuit that controls the overall operation of the imaging device 700, and generates control signals for determining exposure and adjusting focus from the acquired video signal. The CPU 790 adjusts the optical axis positions of the second lens group 320, the fourth lens group 340, and the light amount adjustment unit 350 by controlling the driving of the vibration wave motors 620 and 640 and the meter 630 so as to obtain the determined exposure and an appropriate focus state. Under the control of the CPU 790, the vibration wave motor 620 moves the second lens group 320 in the optical axis direction, the vibration wave motor 640 moves the fourth lens group 340 in the optical axis direction, and the light amount adjustment unit 350 is driven and controlled by the meter 630.

[0041] The optical axis direction position of the second lens group 320 driven by the vibration wave motor 620 is detected by a first linear encoder 770, and the detection result is notified to the CPU 790, thereby feeding back the driving of the vibration wave motor 620. Similarly, the optical axis direction position of the fourth lens group 340 driven by the vibration wave motor 640 is detected by a second linear encoder 775, and the detection result is notified to the CPU 790, thereby feeding back the driving of the vibration wave motor 640. The optical axis direction position of the light amount adjustment unit 350 is detected by an aperture encoder 780, and the detection result is notified to the CPU 790, thereby feeding back the driving of the meter 630. [Explanation of symbols]

[0042] 1,620,640,650 Vibration wave motor (vibration type actuator) 2 Transducers 3 Elastic body 4. Piezoelectric element (electromechanical energy conversion element) 8 Friction member (part of the contact body) 9 Rubber (part of the contact body) 10 First guide member (fixed guide member, part of contact body) 10a Rolling groove (first guide) 11. Ball 12 second guide member (driven guide member) 12a Rolling groove (second guide) 12c Tilt control part (fitting protrusion) 14 Foundation 14c Fitting groove (third guide)

Claims

1. A vibrator having an elastic body and an electromechanical energy conversion element; a contact body having a first guide in contact with the elastic body and extending in a predetermined direction; a driven guide member having a second guide extending in the predetermined direction and driven together with the oscillator by vibration generated by a voltage applied to the electro-mechanical energy conversion element in the predetermined direction relative to the contact body; two balls sandwiched between the first guide and the second guide so as to be rollable in the predetermined direction; A base to which the contact body is fixed, the base has a third guide extending along the predetermined direction, the driven guide member has a fitting protrusion that fits into the third guide, A vibration actuator, characterized in that the fitting protrusion is configured to restrict rotation of the vibrator and the contact body in a rotational direction relative to the predetermined direction.

2. 2. The vibration actuator according to claim 1, further comprising a pressure member that pressurizes the vibrator and the driven guide member to bring the elastic body and the contact body into pressurized contact, and that pressurizes the first guide, the second guide, and the ball into pressurized contact.

3. When viewed from a pressure applying direction of the pressure applying member, the first guide and the elastic body overlap each other, 3. The vibration actuator according to claim 2, wherein when viewed from the pressure direction, the center of pressure applied by said elastic body to said contact body is between said two balls.

4. A cable for applying a voltage to the electromechanical energy conversion element, 4. The vibration actuator according to claim 2, wherein the cable and the third guide overlap when viewed from the direction of pressure application.

5. 5. The vibration actuator according to claim 1, wherein the length of the fitting protrusion in the predetermined direction is 0.3 mm or more and 2.0 mm or less.

6. 6. The vibration actuator according to claim 1, wherein the vibrator and the driven guide member are driven by an elliptical motion as the vibration generated by a voltage applied to the electro-mechanical energy conversion element.

7. 7. The vibration actuator according to claim 1, further comprising a holding member that holds the vibrator and has a contact protrusion that comes into contact with a node common to a plurality of standing waves having different phases as the vibration generated by a voltage applied to the electromechanical energy conversion element.

8. The elastic body includes a main body to which the electromechanical energy conversion element is fixed, and and a plurality of extending portions extending from a plurality of positions in the predetermined direction, the holding member has a plurality of protruding portions protruding from a plurality of positions in the predetermined direction, The vibration wave motor according to claim 7 , wherein the plurality of protrusions are in contact with the main body and are in contact with the plurality of extensions, respectively.

9. 8. The vibration actuator according to claim 7, wherein the driven guide member and the holding member are engaged with each other, so that the driven guide member is driven together with the vibrator by the vibration.

10. The contact body is A friction member that comes into contact with the elastic body; a fixed guide member having the first guide and fixed to the base; 10. The vibration actuator according to claim 1, further comprising:

11. 4. The vibration actuator according to claim 2, wherein the pressure member is a coil spring.

12. 5. The vibration actuator according to claim 4, wherein the cable is a flexible printed circuit board.

13. Lenses and A vibration actuator according to any one of claims 1 to 12, An optical device, characterized in that the lens is driven by the vibration type actuator.

14. An imaging element; A vibration actuator according to any one of claims 1 to 12, An optical device, characterized in that the imaging element is driven by the vibration type actuator.

15. The material, A vibration actuator according to any one of claims 1 to 12, An electronic device, wherein the member is driven by the vibration actuator.

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