Vibration type actuator and imaging apparatus

Abstract

To provide a vibration type actuator that can prevent a reduction in drive characteristics.SOLUTION: A vibration wave motor comprises: a driving member having a vibrator that has an electrical-mechanical energy conversion element and an elastic body to which the electrical-mechanical energy conversion element is fixed, a holding member that holds the vibrator, and a guide member that guides the vibrator and holding member in a first direction; a contact body that is in contact with the vibrator; and a pressure member that applies pressure to the vibrator and contact body in a second direction intersecting the first direction. The holding member has an engaging part that engages with the guide member rotatably in a third direction as an axis intersecting the first direction and second direction, and an output part that transmits power generated through the drive of the driving member to a member to be driven. The output part has an output point. The output point is gripped by a grip member of the member to be driven to transmit the power to the member to be driven. The output point is arranged closer to the vibrator than a bottom face of the holding member.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Regarding vibration-type actuators that use electromechanical energy conversion elements such as piezoelectric elements that convert electrical energy into mechanical energy, various configurations of vibration wave motors are known. For example, a vibration wave motor is known that includes a contact 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 that pressurizes and contacts the two protrusions with the contact body. Here, the back surface of the elastic body refers to the surface on which the protrusions, described below, are not formed.

[0003] In this oscillatory wave motor, by applying a predetermined AC voltage (hereinafter also referred to as "drive voltage") to the electromechanical energy conversion element, elliptical or circular motion is generated at the tips of the two protrusions within a plane including the direction connecting the two protrusions and the direction in which the protrusions protrude. As a result, the contact body receives a frictional driving force from the two protrusions (oscillators), causing the oscillator and contact body to move relatively (hereinafter also referred to as "relative movement") in the direction connecting the two protrusions.

[0004] Vibration wave motors obtain power to drive the driven member from this relative movement. Various proposals have been made for the output section that extracts the power generated by vibration wave motors. For example, in the vibration wave motor disclosed in Patent Document 1, a connecting pin serves as a fulcrum, the point of application is the contact point between the biasing engagement member and the pin member, and a helical spring is disposed at the point of application. The two vibrators are then pressed into contact with the shaft by the biasing force of the helical spring. An output section protruding from one end of the shaft engages with the driven member, transmitting the driving force of the vibration wave motor to the driven member. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-312264 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the configuration disclosed in Patent Document 1, the pressure direction is far from the connecting pin, which serves as the fulcrum, to the point of application. When the vibration wave motor is driven in this state and a load is applied to the output section, a rotational moment acts around the fulcrum. This rotational moment can cause fluctuations in the pressure force applied to bring the protrusion of the vibrator into pressure contact with the contact body. Furthermore, the direction of the generated rotational moment reverses when the motor is driven in one direction of relative movement compared to the other, which can cause the pressure force to increase or decrease depending on the direction of relative movement. Generally, the pressure force in a vibration wave motor affects speed, driving efficiency, and quietness, and such fluctuations in pressure force can degrade the driving characteristics of the vibration wave motor.

[0007] One embodiment of the present invention has been made in view of the above problems, and one of its objects is to provide a vibration actuator that can suppress deterioration in drive characteristics. [Means for solving the problem]

[0008] Electro-mechanical energy A vibration actuator according to one embodiment of the present invention includes a driving member having a vibrator having an electro-mechanical energy conversion element and an elastic body to which the electro-mechanical energy conversion element is fixed, a holding member for holding the vibrator, and a guide member for guiding the vibrator and the holding member in a first direction; a contact body that comes into contact with the vibrator; a pressure member that applies pressure to the vibrator and the contact body in a second direction that intersects with the first direction, The holding member is an engaging portion that engages with the guide member rotatably about an axis in a third direction that intersects the first direction and the second direction; an output section that transmits power generated by driving the driving member to a driven member, the output section is disposed closer to the vibrator than the bottom surface of the holding member; [Effects of the Invention]

[0009] According to one embodiment of the present invention, it is possible to provide a vibration actuator capable of suppressing deterioration in drive characteristics. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an exploded perspective view of an example of a vibration wave motor according to a first embodiment. [Figure 2] 1 shows an example of a vibration wave motor according to a first embodiment. [Figure 3] FIG. 3 is a diagram for explaining an example of a vibration mode according to the first embodiment. [Figure 4] 4A and 4B are diagrams for explaining an example of the relationship of forces generated by a pressure member in the vibration wave motor according to the first embodiment. [Figure 5] 2 is an XZ cross-sectional view of an example of a vibration wave motor and an output transmission section according to the first embodiment. FIG. [Figure 6] FIG. 10 is a diagram for explaining an example of a relationship between forces generated when the vibration wave motor according to the first embodiment is driven. [Figure 7] 10A and 10B are diagrams illustrating an example of a vibration wave motor according to a second embodiment. [Figure 8] 10A and 10B are diagrams illustrating an example of a vibration wave motor according to a third embodiment. [Figure 9] 10 shows an example of an imaging device using a vibration wave motor according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, exemplary embodiments for carrying out the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of components described in the following embodiments are arbitrary and can be changed depending on the configuration of the device to which the present invention is applied or various conditions. In addition, the same reference numerals are used between the drawings to indicate identical or functionally similar elements.

[0012] Example 1 As a first embodiment of the present invention, an example in which the present invention is applied to a vibration wave motor, which is an example of a vibration-type actuator used as a linear vibration wave driving device, will be described below. The vibration wave motor according to this embodiment will be described below with reference to FIGS. 1 to 6. First, the vibration wave motor will be described in detail with reference to FIGS. 1 to 2(d). FIG. 1 is an exploded perspective view of a vibration wave motor 1 according to this embodiment, and FIGS. 2(a) to 2(d) are assembly diagrams of the vibration wave motor 1. Specifically, FIG. 2(a) is a perspective view of the vibration wave motor 1, and FIG. 2(b) is an XZ plan view of the vibration wave motor 1. Furthermore, FIG. 2(c) is an XZ cross-sectional view of the vibration wave motor 1 taken along line 2C-2C in FIG. 2(a), and FIG. 2(d) is a YZ cross-sectional view of the vibration wave motor 1 taken along line 2D-2D in FIG. 2(c). Here, the relative movement direction of the vibrator 2 is defined as the X direction, the pressure direction as the Z direction, and the direction perpendicular to the X and Z directions as the Y direction. In this specification, the terms "upper" and "lower" correspond to the upper and lower directions in the Z direction, respectively.

[0013] The oscillatory wave motor 1 includes an elastic body 3, a piezoelectric element 4, a flexible printed circuit board 5, a holding member 6, a pressure spring 7, a friction member (contact body 8), rubber 9, a first guide member 10, a second guide member 12, a screw 13, and a base 14. Hereinafter, the friction member will be referred to as the contact body 8. The elastic body 3 includes a rectangular (flat) main body 3c and a plurality of (here, two positions x two positions = four) extension portions 3b extending from a plurality of positions (here, two positions) in the X direction of the main body 3c. The plurality of extension portions 3b protrude from a plurality of different positions (here, four positions) in the X direction and the Y direction of the main body 3c.

[0014] A piezoelectric element 4, which is an electromechanical energy conversion element, is fixed to the elastic body 3 with an adhesive or the like. A flexible printed circuit board 5 is fixed to the surface of the piezoelectric element 4 opposite to the surface to which the elastic body 3 is fixed. Here, the vibrator 2 is composed of the elastic body 3, the piezoelectric element 4, and the flexible printed circuit board 5. The piezoelectric element 4 and the flexible printed circuit board 5 can be fixed using an anisotropic conductive paste or anisotropic conductive film that allows electricity to flow only in the Z direction.

[0015] Materials with low vibration damping, such as metals and ceramics, can be used as materials for the elastic body 3. Regarding the manufacture of the elastic body 3, the protrusions 3a may be integrally formed by press molding or cutting, or the protrusions 3a may be manufactured separately and then fixed to the elastic body 3 by welding or adhesive later. Furthermore, multiple protrusions 3a may be provided as in this embodiment, or only one protrusion 3a may be provided.

[0016] The piezoelectric element 4 can be made of lead zirconate titanate. Alternatively, the piezoelectric element 4 may be made primarily of a lead-free piezoelectric material such as barium titanate or bismuth sodium titanate. Electrode patterns (not shown) are formed on both sides of the piezoelectric element 4, and power is supplied from the flexible printed circuit board 5 using the electrode patterns.

[0017] The pressure mechanism according to this embodiment will now be described. A holding member 6 that applies pressure to and holds the vibrator 2 is provided below the vibrator 2, and a second guide member 12 is provided above the vibrator 2. Two pressure fulcrums 6e are provided at one end of the holding member 6 in the X direction, and two fitting portions 12b are provided on the second guide member 12 at two locations, and these fitting portions 12b are rotatable around the Y-axis direction. A pressure spring 7 is provided between a spring mounting portion 6f provided at the other end of the holding member 6 in the X direction and the second guide member 12. The pressure spring 7 is a tension coil spring. Two protrusions 6a are provided on the holding member 6 at approximately the center in the X direction between the pressure fulcrum 6e and the pressure spring 7 (spring mounting portion 6f). The tops of these two protrusions 6a provided on the surface side of the holding member 6 contact the vibrator 2.

[0018] As described above, the pressure mechanism according to this embodiment applies pressure to the vibrator 2 in the Z direction by the principle of a lever, with the pressure fulcrum 6e as the fulcrum, the spring installation portion 6f as the force point, and the protrusion 6a as the point of action. In addition, a contact body 8 is provided above the vibrator 2, and is in pressure contact with the protrusion 3a of the elastic body 3 in the Z direction due to the pressure applied to the vibrator 2 by the pressure mechanism. With this pressure mechanism, the vibrator 2, holding member 6, and second guide member 12, which serve as driving members in this embodiment, can move integrally in the X direction relative to the contact body 8.

[0019] An output section 6d is provided on the surface of the holding member 6 opposite the protrusion 6a. In this embodiment, a recess having a predetermined depth in the direction of the vibrator is provided on the bottom surface 6h of the holding member 6, and a protrusion is provided protruding from the bottom surface of the recess toward the bottom surface 6h of the holding member 6. This protrusion acts as an output section that provides driving force to the first and second gripping members 15 and 16 (see FIG. 5), which will be described later, at the gripped point. In other words, this gripped point acts as an output point 6g that actually applies driving force to the gripping members at the output section 6d. The vibration wave motor 1 can output the driving force generated by the movement of the vibrator 2 to the outside via the output section 6d of the holding member 6. In this embodiment, a pressure support point 6e is provided at one end of the holding member 6 in the X direction, and a spring installation section 6f is provided at the other end. However, these are not limited to being provided at the ends of the holding member 6 in the X direction, and may be provided at positions where they can function as a fulcrum and a force point of the principle of a lever with the protrusion 6a as the point of application. Also, the flexible printed circuit board 5 can be fixed to the flexible base 6b of the holding member 6 with double-sided tape or the like.

[0020] A rubber 9, a first guide member 10, and a second guide member 12 are provided above the contact body 8. The contact body 8 is fixed to the first guide member 10 by the adhesive force of the rubber 9. The rubber 9 also serves to damp vibrations by preventing the vibrations from the vibrator 2 from being transmitted to the first guide member 10. The first guide member 10 is fixed to a base 14, which is a fixing member, with screws 13. The contact body 8, the first guide member 10, and the rubber 9 may be fixed by adhesive or screws. The contact body 8 may be made of a highly wear-resistant metal, ceramic, resin, or a composite material thereof. In particular, nitrided stainless steel such as SUS420J2 may be used as the material for the contact body 8 from the viewpoints of wear resistance and mass productivity.

[0021] Next, the linear guide mechanism according to this embodiment will be described. The first guide member 10 and the second guide member 12 are each provided with two rolling grooves 10a, 12a, which sandwich two balls 11. When the vibration wave motor 1 is driven, the balls 11 roll in the rolling grooves 10a, 12a, allowing the vibrator 2, holding member 6, and second guide member 12 to move smoothly in the X direction. The materials for the first guide member 10 and the second guide member 12 must be hard enough to receive pressure from the rolling grooves 10a, 12a, respectively. In addition, metal, especially stainless steel, can be used from the viewpoint of workability.

[0022] The base 14 includes two fixed portions 14a, each of which includes screw holes, retaining portions, and holes for securing the first guide member 10, as well as holes for externally securing the base 14. The fixed portions 14a are also provided with a connecting portion 14b, a groove 14c, and a collision prevention portion 14d. The groove 14c is formed along the X direction in a portion of the connecting portion 14b. The groove 14c and the tilt prevention portion 12c of the second guide member 12 fit loosely, i.e., with a predetermined amount of play, thereby preventing rotation of the vibrator 2 and other components around the X axis. The collision prevention portion 14d extends from the fixed portion 14a toward the holding member 6 in the X direction and prevents the pressure support fulcrum 6e and spring installation portion 6f of the holding member 6 from colliding with the fixed portion 14a as the holding member 6 moves. The base 14 can be formed of resin for ease of processing and sliding.

[0023] Furthermore, the flexible printed circuit board 5 is fixed to the connecting portion 14b. Therefore, the base 14 also functions to accommodate the curved portion of the flexible printed circuit board 5 that moves while curving as the vibrator 2 and the holding member 6 move.

[0024] Next, the vibration modes excited in the vibrator 2 will be described using Figures 3(a) and 3(b). In this embodiment, an AC voltage is applied to the piezoelectric element 4 through the flexible printed circuit board 5 to excite standing waves (out-of-plane bending vibrations) that are out of phase with each other in the vibrator 2, and a vibration is generated that is a combination of these out-of-plane bending vibrations. Figure 3(a) shows the vibrator 2 driven in mode A, which is the first vibration mode, and Figure 3(b) shows the vibrator 2 driven in mode B, which is the second vibration mode. Note that in Figures 3(a) and 3(b), the flexible printed circuit board 5 is omitted from the illustration of the vibrator 2 to simplify the explanation.

[0025] 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 roughly 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.

[0026] By combining the vibrations of Mode A and Mode B, the two protrusions 3a perform elliptical or circular motion within 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 relative to each other. 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.

[0027] In order to efficiently drive the oscillatory wave motor 1, it is necessary to support the vibrator 2 without impeding the vibrations (displacements) of the two vibration modes excited in the vibrator 2, and for this purpose, it is desirable to support the vibrator 2 near the nodes of these two vibration modes. For this reason, two protrusions 6a are provided on the holding member 6 in order to apply pressure to and hold the common node of the two vibration modes excited in the vibrator 2. In addition, by positioning the vibrator 2 with the retaining portion 6c provided on the holding member 6, the two protrusions 6a can be brought into contact with the vibrator 2 near the nodes of the two vibration modes.

[0028] Furthermore, the protrusions 6a not only pressurize the vibrator 2 but also hold the vibrator 2 in the X and Y directions by frictional force. In this embodiment, the maximum value of the static frictional force between the protrusions 6a and the vibrator 2 is always greater than the reaction force that the vibrator 2 receives from the contact body 8 when driving the vibrator 2, so the vibrator 2 does not move relative to the holding member 6. This allows for precise driving.

[0029] In this embodiment, a notch is provided above the retaining portion 6c as shown in Fig. 2(d). For example, when the vibration wave motor 1 is subjected to a strong force, such as a drop impact, this notch collides with the first guide member 10, preventing the balls 11 from coming off the rolling grooves. In this way, the retaining portion 6c also serves as a stopper to prevent positional changes when an overload is applied to the first guide member 10.

[0030] Next, the pressure mechanism according to this embodiment will be described in more detail with reference to FIG. 4. FIG. 4(a) is an XY plan view showing only the vibrator 2 and the holding member 6, and FIG. 4(b) is a cross-sectional view of these members taken along line 4B-4B in FIG. 4(a). Note that in FIG. 4(b), the Y-direction position of line 4B-4B is shifted midway to clearly illustrate the positional relationship in the XZ plane between the output portion 6d, the pressure support point 6e, and the spring installation portion 6f. FIG. 4(b) also shows the Z-direction forces applied to the output portion 6d, the pressure support point 6e, and the spring installation portion 6f. The X-direction position of the output portion 6d is assumed to be approximately the same as the X-direction position of the protrusion 6a in contact with the vibrator 2.

[0031] The force of the pressure spring 7 generates an upward force Rb in the Z direction on the spring mounting portion 6f. As mentioned above, the pressure fulcrum 6e is free to rotate around the Y axis relative to the fitting portion 12b, but other displacements are restricted. Therefore, if the distance in the X direction from the pressure fulcrum 6e to the protrusion 6a is x1 and the distance in the X direction from the protrusion 6a to the spring mounting portion 6f is x2, the pressure spring 7 generates a rotational moment Rb × (x1 + x2) around the pressure fulcrum 6e. If x1 and x2 are equal, the convex portion 6a receives a downward force of 2Rb in the Z direction according to the following moment balance equation (1). In other words, the vibrator 2 is pressed against the contact member 8 with a force of 2Rb. This is the pressure when the vibration wave motor 1 is stationary. P×x1=Rb×(x1+x2) From x1=x2 P=2Rb...Equation (1)

[0032] Next, the output transmission mechanism according to this embodiment will be described with reference to Figure 5. Figure 5 is an XZ cross-sectional view of the vibration wave motor 1 and output transmission unit 18 according to this embodiment. The output transmission unit 18 according to this embodiment, which is connected to a driven member, is provided with a first gripping member 15, a second gripping member 16, and a torsion spring 17. The first gripping portion 15a of the first gripping member 15 and the second gripping portion 16a of the second gripping member 16 sandwich the output unit 6d. The second gripping member 16 is fitted to the first gripping member 15 so as to be rotatable about the Y axis, and is biased by the torsion spring 17 with a predetermined force in the Y axis direction while applying a gripping force about the Y axis.

[0033] Since this gripping force is greater than the thrust generated by the vibration wave motor 1, no play occurs between the vibration wave motor 1 and the driven member connected to the output transmission unit 18, allowing for precise driving of the driven member. Furthermore, since the output unit 6d is gripped in the X direction, which is the direction of travel, stable driving can be performed without affecting the pressure force on the vibrator 2. In this embodiment, the thrust generated by the vibration wave motor 1 is transmitted to the driven member via the output transmission unit 18 at the gripping points where the gripping members 15 and 16 grip the output unit 6d.

[0034] The driving force generated by the vibrator 2 is transmitted to the contact body 8 via the convex portion 6a so as to act in the X direction. Next, referring to Fig. 6, the forces acting on the vibrator 2 and the holding member 6 when the vibration wave motor 1 is operating will be described. Fig. 6 shows the forces acting on the vibrator 2 and the holding member 6 in the same manner as Fig. 4(b), with Fig. 6(a) showing the case where the vibrator 2 moves leftward on the page, and Fig. 6(b) showing the case where the vibrator 2 moves rightward.

[0035] When the vibration wave motor 1 is driven, the convex portion 6a receives a force F2 in the X direction from the vibrator 2. The output portion 6d also receives a force from the output transmission unit 18 at the gripping point of the output transmission unit 18, which is equal to but opposite to the force generated by the vibrator 2. When the vibration moves leftward on the paper as shown in FIG. 6(a), the convex portion 6a receives a force F2 toward the left in the X direction, and the output portion 6d receives a force F1 from the output transmission unit 18 toward the right in the X direction (-F2 = F1). If the distances in the Z direction from the pressure fulcrum 6e to the points where F1 and F2 are generated are L1 and L2, respectively, the following equation for moment balance holds. Note that the signs of each parameter are defined as follows: a force toward the right in the X direction from the pressure fulcrum 6e as the center is positive, and a force toward the upward direction in the Z direction is positive. P×x1=Rb×(x1+x2)+F1×L1+F2×L2 P=Rb×(x1+x2) / x1+(F1×L1+F2×L2) / x1 Here, -F2=F1 P=Rb×(x1+x2) / x1+(L1-L2)F1 / x1...Equation (2) If x1=x2, P=2Rb+(L1-L2)F1 / x1

[0036] From equation (2), the pressure P applied to the vibrator 2 fluctuates by (L1-L2)F1 / x1. In other words, the larger L1 and L2 are, or the smaller x1 is, the greater the fluctuation in pressure P. Furthermore, when the driving direction is reversed from that shown in Figure 6(a) to that shown in Figure 6(b), the sign of F1 is reversed, and the sign of the fluctuation part of the pressure force is also reversed. For example, when the vibration moves to the left side of the page as in Figure 6(a), F1 takes a negative value, so (L1-L2)F1 / x1 becomes a positive value, and the pressure force P increases compared to when the vibrator is stationary. Conversely, when the vibration moves to the right side of the page as in Figure 6(b), F1 becomes a negative value, so (L1-L2)F1 / x1 becomes a positive value, and the pressure force P decreases.

[0037] Generally, when the applied pressure in a vibration wave motor increases, the drive speed decreases and drive efficiency tends to deteriorate. Conversely, when the applied pressure is small, the drive speed increases and drive efficiency improves, but there is a disadvantage in that abnormal noise is more likely to occur. Furthermore, if the speed differs depending on the direction of movement, there is a concern that this will affect controllability. For this reason, it is necessary to keep the fluctuations in the applied pressure in a vibration wave motor within a certain value.

[0038] In conventional oscillatory wave motors, the holding member has a generally flat plate shape, and the output section is positioned to protrude from the bottom surface of this plate. In contrast, the pressure support 6e is often provided on the side of the generally flat plate. As a result, L1 becomes significantly larger than L2, making fluctuations in the pressure force P significant for precise operation. In this embodiment, one of the objectives is to minimize fluctuations in the pressure force due to the driving direction, in consideration of the above-mentioned equation (2). Specifically, the point (output point 6g) where the actual driving force F1 is obtained from the output section 6d is located inside the holding member 6, i.e., higher in the Z direction than the surface opposite the vibrator 2 (the bottom surface of the holding member 6). This allows L1 to be sufficiently small compared to conventional oscillatory wave motors, making it possible to set it at least close to L2.

[0039] Ideally, the above-mentioned fluctuations should be zero, but in reality, the positional relationship between the convex portion 6a, the output portion 6d, the pressure fulcrum 6e, and the spring installation portion 6f is subject to design constraints and material constraints of the holding member 6. Therefore, it is desirable to keep the fluctuations below a certain value and to configure the holding member 6 under conditions that satisfy this. That is, to keep the pressure force within an appropriate range, it is preferable to set each parameter so that the following formula is satisfied. According to formula (3), the absolute value of the term for the pressure force fluctuation during driving can be kept to 10% or less of the pressure force when stationary, making it possible to perform precise drive control that is currently suitable for practical use. 0.1×(2Rb×x2 / x1)> |(L1-L2)F1 / x1|...Equation (3)

[0040] As described above, the vibration wave motor 1, which is an example of a vibration-type actuator according to this embodiment, transmits a driving force to a driven member via a gripped point gripped by a gripping member provided on an output transmission unit 18 of the driven member. The vibration wave motor 1 includes a driving member having a vibrator 2, a holding member 6, and a guide member (12), a contact body 8 in contact with the vibrator 2, and a pressure member (7). The driving member includes an electromechanical energy conversion element (4) that converts electrical energy into mechanical energy and an elastic body 3 to which the conversion element (4) is fixed. In this embodiment, a piezoelectric element 4 is used as an example of an electromechanical energy conversion element. The holding member 6 holds the vibrator 2, and a second guide member 12, which is an example of a guide member, guides the vibrator 2 and the holding member 6 in a first direction. In this embodiment, the first direction corresponds to, for example, the X direction in FIG. 1 . In this embodiment, a pressure spring 7 is used as an example of a pressure member, and the pressure spring 7 presses the vibrator 2 and the contact body 8 in a second direction intersecting the first direction. In this embodiment, the second direction corresponds to, for example, the Z direction in FIG.

[0041] The holding member 6 is provided with a pressure fulcrum 6e as an engagement portion that engages with the second guide member 12. The pressure fulcrum 6e rotatably engages with the second guide member 12 around a third direction that intersects the first and second directions. In this embodiment, the third direction corresponds to the Y direction that intersects the X and Z directions. Note that this embodiment is described assuming that the first, second, and third directions are orthogonal to each other. However, this embodiment also includes cases where the directions deviate from a strictly orthogonal state due to assembly errors or, for example, requests for compactness. The holding member 6 also includes an output unit 6d provided with an output point 6g (corresponding to the gripped point described above) that transmits power generated by driving the driving member to the driven member. In this embodiment, the output unit 6d is located closer to the vibrator than the bottom surface 6h of the holding member 6. By arranging the output unit 6d in this manner in the holding member 6, the output point 6g can be located closer to the vibrator than the bottom surface 6h of the holding member 6.

[0042] In the above-described vibration wave motor 1, the holding member 6 supports the vibrator 2 on the front side via the protrusions 6a and has a flat plate portion on the back side where the output point 6g is located. The output point 6d is provided in this flat plate portion so as to protrude from the bottom surface of a recess provided from the bottom surface 6h of the holding member 6 toward the front side toward the opening of the recess. The output point 6g is provided at a position (gripped point) where the gripping members (15, 16) of the driven member grip the output point 6d within this recess.

[0043] In the above-described vibration wave motor 1, the axis of the engaging portion (6e) acts as a fulcrum, the point (6f) where the pressure force from the pressure member (7) acts on the holding member 6 acts as a force point, and the point where the holding member 6 presses the vibrator 2 towards the contact body 8 acts as a point of action. Here, the distance in the X direction from the fulcrum to the point of action is defined as x1, the distance in the X direction from the fulcrum to the point of force is defined as x1+x2, the distance in the Z direction from the fulcrum to the output point is defined as L1, and the distance in the Z direction from the fulcrum to the point of action is defined as L2. The pressure force applied by the pressure member (7) to the point of force is defined as Rb, the thrust generated by the vibrator 2 is defined as F1, and the pressure force applied to the vibrator 2 at the point of action is defined as P. In this case, these variables are defined as 0.1×(2Rb×x2 / x1) > |(L2-L1)F1 / x1| By satisfying this condition, the fluctuation in the pressure force from the vibrator 2 to the contact body 8 depending on the driving direction can be suppressed to a level that satisfies the stopping accuracy currently required of a vibration wave motor.

[0044] In the above-described oscillatory wave motor 1, the driving member and the contact body 8 move relative to each other by combining two different standing waves generated in the vibrator 2. At this time, the vibrator 2 can be pressed toward the contact body 8 by two protrusions (6a) provided on the holding member 6 at the position of a common node of the two different standing waves in the vibrator 2. Furthermore, the output point can be located at a position that substantially overlaps these two protrusions (6a) in the X direction. Furthermore, the output point can be located at a substantially central position between these two protrusions (6a) in the Y direction.

[0045] The above-described configuration in this embodiment makes it possible to provide the output point 6g inside the holding member 6 of the vibration wave motor 1. By adopting such a structure, it is possible to suppress fluctuations in the pressure force from the vibrator 2 to the contact body 8 depending on the driving direction, and to suitably reduce changes in the driving characteristics of the vibration wave motor 1.

[0046] In the linear oscillatory wave motor of the present invention, the method of generating elliptical or circular motion on the contact surface is not limited to the above. For example, vibrations in bending vibration modes different from those described above may be combined, or a longitudinal vibration mode that expands and contracts the elastic body 3 in the longitudinal direction may be combined with a bending vibration mode. Any driving method may be used as long as it generates elliptical and circular motion on the contact surface by combining a vibration mode that displaces the contact surface in the movement direction of the contact body 8 with a vibration mode that displaces the contact surface in the pressure direction and has a common node for pressure and retention.

[0047] Example 2 In the first embodiment, in order to reduce fluctuations in the pressure force P, attention is focused only on the output point of the driving force, and the output point is located closer to the vibrator 2 than the bottom surface of the holding member 6. In contrast, the present embodiment shows an example of another configuration for reducing fluctuations in the pressure force. Note that the vibration wave motor according to this embodiment has substantially the same structural elements as the vibration wave motor 1 illustrated in the first embodiment, with the exception of the holding member 26, and therefore detailed description thereof will be omitted here.

[0048] Figures 7(a) and 7(b) show the vibrator 2 and holding member 26 according to this embodiment in the same format as Figures 4(a) and 4(b). Specifically, Figure 7(a) is an XY plan view of the vibrator 2 and holding member 26 according to this embodiment, and Figure 7(b) is a cross-sectional view taken along line 7A-7A in Figure 7(a). Figure 7(c) is a perspective view of the holding member 26.

[0049] In this embodiment, the position of the pressure fulcrum 26e in the Z direction is made to coincide with the contact point (protrusion 26a) between the vibrator 2 and the holding member 26, i.e., the point where F2 occurs. Specifically, in the flat-plate arrangement of the pressure fulcrum 6e in Example 1, a portion is provided that protrudes from the flat-plate portion toward the contact body 8, and the pressure fulcrum 26e is provided at this position. This makes it possible to arrange the position of the pressure fulcrum 26e and the position of the top of the protrusion 26a on the same XY plane. This makes it possible to make L2 approximately zero, and by substituting L2 = 0 into the above-mentioned equation (2), the pressure P is given by the following equation (4). P=2Rb+L1×F1 / x1...Equation (4)

[0050] Because the fluctuation is L1 × F1 / x1, simply setting L2 to 0 increases L1 by that amount, leaving the fluctuation unchanged. Therefore, it is necessary to simultaneously reduce the contact point between the output section 26d and the output transmission section (not shown), i.e., the distance L1 in the Z direction between the output point of F1 and the pressure support point 6e. In this embodiment, as shown in FIG. 7(c), a hole is provided around the periphery of the output section 26d, penetrating from the bottom to the surface of the holding member 26. This hole allows a gripping member (not shown) to grip the output section 26d at a position closer to the surface of the holding member 26. This allows the position of the output point 26g on the output section 26d to be closer to the vibrator 2, thereby reducing L1.

[0051] As described above, in the vibration wave motor 1 according to this embodiment, the holding member 26 has a flat plate portion that supports the vibrator 2 on the surface side via the protrusions 26a and the like. The output portion 26d is provided in this flat plate portion so as to be located inside a through hole that extends from the bottom surface 26h of the holding member 26 toward the surface side. In this embodiment, using this configuration makes it possible to position the output portion 26d closer to the vibrator than the bottom surface 26h of the holding member 26. The output point 26g is provided so as to correspond to a position (gripped point) where the gripping members (15, 16) of the driven member grip the output portion inside the through hole. By providing the gripped point inside the through hole, the output point 26g can be located closer to the surface of the holding member 26, and the output point 26g can be positioned closer to the protrusions 26a in the Z direction.

[0052] Furthermore, the engaging portion of this embodiment is provided on the holding member 26 so as to protrude in the Z direction from a plane defined by the X and Y directions and the point (the top of the convex portion 26a) at which the holding member 26 presses the vibrator 2 toward the contact body 8 or the output portion 26d. By adopting this arrangement, the distance L2 in the Z direction from the engaging portion (26e) to the point (the convex portion 26a) at which the holding member 26 presses the vibrator 2 toward the contact body 8 can be made substantially zero. By arranging the output point 26g and the engaging portion (26e) as in this embodiment, L2 can be made substantially zero, and L1 can be made significantly smaller than in the conventional configuration. This suppresses fluctuations in the pressure force from the vibrator 2 to the contact body 8 depending on the driving direction, thereby suitably reducing changes in the driving characteristics of the vibration wave motor 1.

[0053] Example 3 In the first and second embodiments described above, the output portions 6d and 26d of the holding members 6 and 26 are provided in recesses formed in the bottom surface or in holes penetrating from the bottom surface to the surface, so that the output point of the driving force is closer to the vibrator. In contrast, this embodiment shows another example of a configuration that reduces fluctuations in the pressing force. Since the vibration wave motor according to this embodiment has substantially the same structural elements as the vibration wave motor 1 illustrated in the first embodiment, except for the holding member 36, detailed description thereof will be omitted here.

[0054] Figures 8(a) and 8(b) show the vibrator 2 and holding member 36 according to this embodiment in the same format as Figures 4(a) and 4(b). Specifically, Figure 8(a) is an XY plan view of the vibrator 2 and holding member 36 according to this embodiment, and Figure 8(b) is a cross-sectional view taken along line 8B-8B in Figure 8(a). Figure 8(c) is a perspective view of the holding member 36.

[0055] In this embodiment, as in Example 2, the Z-direction position of the pressure fulcrum 36e is aligned with the contact point between the vibrator 2 and the holding member 26, i.e., the point where F2 is generated. In addition, in this embodiment, the Z-direction position of the contact point between the output unit 36d and an output transmission unit (not shown), i.e., the output point of F1, and the pressure fulcrum 36e are aligned, thereby making L1 approximately zero. Specifically, instead of the output unit 6d in Example 1, a portion protruding in the Y-direction from the flat plate-like portion on which the protrusions 36a and the like are disposed is provided, and a portion protruding toward the contact body 8 is provided on this portion, and the output unit 36d is provided at this position. By arranging the output unit 36d in this manner, rather than arranging it on the bottom surface 36h side, it is possible to arrange the output unit 36d closer to the contact body 8 than the surface of the holding member 36 while avoiding the contact body 8. With the configuration examples of Examples 1 and 2 as they are, for example, due to the thickness of the gripping portion of the gripping member in the Z-direction, the output transmission unit interferes with the vibrator 2, making it difficult to make L1 zero. However, by extending the output portion 36d in the Y direction as in this embodiment, the Z-direction position of the contact point between the output portion 36d and the output transmission portion (not shown) can also be made to coincide with the pressure support point 6e.

[0056] In this embodiment, to further prevent the generation of a moment around the Z axis, two output parts 36d are provided, each of which is gripped by an output transmission part. This allows L2 and L1 to be approximately zero. By substituting L1 = 0 and L2 = 0 into the above-mentioned equation (2), the applied pressure P is given by the following equation (5). P=2Rb...Equation (5)

[0057] That is, in the vibration wave motor according to this embodiment, there is almost no fluctuation in the pressure force P, and a constant pressure force P can be obtained regardless of the driving direction of the driving member. According to this embodiment, although there is an increase in size in the Y direction and an increase in the number of parts, it is possible to suppress fluctuations in the pressure force to almost zero.

[0058] In this embodiment, the output portion 36d is provided on the holding member 36 so as to protrude in the Z-axis direction from a plane defined by the X and Y directions and the point (top of the protrusion 36a) at which the holding member 36 presses the vibrator 2 toward the contact body 8 toward the side where the contact body 8 or the engaging portion (36e) is located. This configuration allows the output portion 36d to be positioned closer to the vibrator than the bottom surface 36h of the holding member 36. The output point 36g is provided at the protruding portion corresponding to a position where the gripping members (15, 16) of the driven member grip the output portion 36d. The output point 36g is also positioned symmetrically in the Y-axis direction from approximately the center of the two protrusions (36a). This configuration allows the output point 36g to be positioned closer to the contact body 8 than the surface of the holding member 36, thereby making the distance L1 in the Z-axis direction from the engaging portion (36e) to the output point 36g approximately zero. Therefore, it is possible to suppress fluctuations in the pressure from the vibrator 2 to the contact body 8 depending on the driving direction, and to suitably reduce changes in the driving characteristics of the oscillatory wave motor 1.

[0059] Example 4 The oscillatory wave motor can be used, for example, for driving lenses in imaging devices (optical devices, electronic devices), etc. Therefore, an example of an imaging device using an oscillatory wave motor to drive a lens arranged in a lens barrel will be described as a fourth embodiment of the present invention with reference to Figures 9(a) and 9(b).

[0060] 9(a) is a top view showing a schematic configuration of an imaging device 700. The imaging device 700 is provided with a camera body 730 equipped with an imaging element 710 and a power button 720. The imaging device 700 is also provided with a lens barrel 740 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 drivers 620 and 640. The lens barrel 740 is replaceable as an interchangeable lens, and a lens barrel 740 appropriate for the 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 drivers 620 and 640, respectively.

[0061] The vibration wave driving device 620 has the same configuration as the vibration wave motors according to Examples 1 to 3. In the vibration wave driving device 620, the drive unit and output transmission unit 18 of the vibration wave motor 1 are integrated with the second lens group 320 to move the second lens group 320 in the optical axis direction. In addition, the vibration wave driving device 640 has the same configuration as the vibration wave driving device 620, and moves the fourth lens group 340 in the optical axis direction.

[0062] 9(b) is a block diagram showing a schematic configuration of the imaging device 700. Inside the lens barrel 740, the first lens group 310, 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. Light that passes through the first lens group 310 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, outputs it, and sends it to the camera processing circuit 750.

[0063] The camera processing circuit 750 performs amplification, gamma correction, etc. 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 undergone predetermined processing in the camera processing circuit 750 is sent to the CPU 790 via the AE gate 755, AF gate 760, and 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.

[0064] 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 driving devices 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 driving device 620 moves the second lens group 320 in the optical axis direction, the vibration wave driving device 640 moves the fourth lens group 340 in the optical axis direction, and the meter 630 drives and controls the light amount adjustment unit 350.

[0065] The optical axis direction position of the second lens group 320 driven by the vibration wave driver 620 is detected by a first linear encoder 770, and the detection result is notified to a CPU 790, thereby providing feedback to the drive of the vibration wave driver 620. Similarly, the optical axis direction position of the fourth lens group 340 driven by the vibration wave driver 640 is detected by a second linear encoder 775, and the detection result is notified to a CPU 790, thereby providing feedback to the drive of the vibration wave driver 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 a CPU 790, thereby providing feedback to the drive of the meter 630.

[0066] As described above, the imaging device 700 according to this embodiment includes the vibration wave driving devices 620 and 640, the imaging element 710, and a CPU 790 that functions as an example of a control unit that controls the piezoelectric elements 4 of the vibration wave driving devices 620 and 640. The vibration wave driving devices 620 and 640 include the vibration wave motors described in Examples 1 to 3. The imaging device 700 also includes the second lens group 320 and the fourth lens group 340 as driven members.

[0067] With this configuration, autofocusing can be performed using the imaging device 700 and the vibration wave driving devices 620 and 640. Furthermore, by using the vibration wave driving devices 620 and 640, it is possible to suppress degradation of drive characteristics when driving the lens group and the like in the imaging device 700.

[0068] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above-described embodiments. The present invention also includes inventions that have been modified within the scope of the present invention and inventions equivalent to the present invention. Furthermore, the above-described embodiments and modifications can be combined as appropriate within the scope of the present invention. [Explanation of symbols]

[0069] 1: Vibration wave motor (vibration type actuator) 2: Vibrator 3: Elastic body 3a:Protrusion 3b: Extension part 3c: Main body 4: Piezoelectric element 5: Flexible printed circuit board 6: Holding member 6a, 26a, 36a: Convex part 6b: Flexible stand 6c: Retaining part 6d, 26d, 36d: Output section 6e, 26e, 36e: Pressure support point 6f: Spring installation section 6g,26g,36g: Output point 6h,26h,36h: Bottom 7: Pressure spring 8: Contact body 9: Rubber 10: First guide member 10a: Rolling groove 11: Ball 12: Second guide member 12a: Rolling groove 12b: Fitting part 12c: Tilt control section 13: Screw 14: Base 14a: Fixed part 14b: Connection part 14c: Groove 14d: Collision prevention part 15: First gripping member 15a: First gripping part 16: Second gripping member 16a: Second gripping part 17: Torsion spring 18: Output transmission section

Claims

1. a driving member including a vibrator having an electromechanical energy conversion element and an elastic body to which the electromechanical energy conversion element is fixed, a holding member that holds the vibrator, and a guide member that guides the vibrator and the holding member in a first direction; a contact body that comes into contact with the vibrator; a pressure member that applies pressure to the vibrator and the contact body in a second direction that intersects with the first direction, The holding member is an engaging portion that engages with the guide member rotatably about an axis in a third direction that intersects the first direction and the second direction; an output section that transmits power generated by driving the driving member to a driven member, The output portion is located closer to the vibrator than the bottom surface of the holding member.

2. the holding member has a flat plate portion that supports the vibrator on a front surface side that is the back surface of the bottom surface, 2. The vibration actuator according to claim 1, wherein the output portion is provided so as to protrude from a bottom surface of a recess provided in the flat plate portion from the bottom surface of the holding member toward the front surface.

3. the output section has an output point that transmits power generated by driving the driving member to the driven member, 3. The vibration actuator according to claim 2, wherein the output point is at a position where a gripping member of the driven member grips the output portion within the recess.

4. the holding member has a flat plate portion that supports the vibrator on a front surface side that is the back surface of the bottom surface, 2. The vibration actuator according to claim 1, wherein the output portion is provided so as to be located inside a through hole provided in the flat plate portion from the bottom surface to the front surface of the holding member.

5. the output section has an output point that transmits power generated by driving the driving member to the driven member, 5. The vibration actuator according to claim 4, wherein the output point is at a position where a gripping member of the driven member grips the output portion inside the through hole.

6. 2. The vibration actuator according to claim 1, wherein a distance L1 from the engagement portion to the output portion in the second direction is approximately zero.

7. 7. The vibration actuator according to claim 1, wherein the output portion is provided on the holding member so as to protrude in the second direction from a plane defined by the first direction, the third direction, and the point at which the holding member presses the vibrator toward the contact body toward the side where the engagement portion is located.

8. the output section has an output point that transmits power generated by driving the driving member to the driven member, 8. The vibration actuator according to claim 7, wherein the output point is at a position where a gripping member of the driven member grips the output portion in the protruding portion.

9. a shaft of the engaging portion is defined as a fulcrum, a point at which the pressure force from the pressure member acts on the holding member is defined as a force point, and a point at which the holding member presses the vibrator toward the contact body is defined as an action point, Furthermore, the distance in the first direction from the fulcrum to the point of application is defined as x1, the distance in the first direction from the fulcrum to the point of force is defined as x1+x2, the distance in the second direction from the fulcrum to the output portion is defined as L1, and the distance in the second direction from the fulcrum to the point of application is defined as L2. When the pressure applied by the pressure member to the force point is Rb, the thrust generated by the vibrator is F1, and the pressure applied to the vibrator at the action point is P, the following formula is obtained: 0.1×(2Rb×x2 / x1) > |(L2-L1)F1 / x1| The vibration actuator according to claim 1 , wherein the following conditions are satisfied:

10. 10. The vibration actuator according to claim 1, wherein a distance L2 in the second direction from the engaging portion to a point where the holding member presses the vibrator toward the contact body is approximately zero.

11. 11. A vibration actuator according to claim 1, wherein the engagement portion is provided on the holding member so as to protrude in the second direction from a plane defined by the first direction, the third direction, and the point at which the holding member presses the vibrator toward the contact body toward the side where the output portion is located.

12. 12. A vibration actuator according to claim 1, wherein the driving member and the contact body move relative to each other by combining two different standing waves generated in the vibrator, and two protrusions provided on the holding member pressurize the vibrator toward the contact body at a common node position of the two different standing waves in the vibrator.

13. The vibration actuator according to claim 12 , wherein the output portion is disposed at a position that substantially overlaps with the two protrusions in the first direction.

14. 14. The vibration actuator according to claim 1, wherein the output portion is disposed at a position substantially in the center of the two protrusions or symmetrical to the center in the third direction.

15. A vibration type actuator according to any one of claims 1 to 14, An imaging element; a control unit that controls the electromechanical energy conversion element of the vibration actuator; Equipped with The imaging device, wherein the driven member includes a lens.

Images