JPWO2009066467A1 - Vibration actuator and imaging device - Google Patents

Abstract

A vibration actuator having a rotor driven by a traveling wave. A rotor having a cylindrical driven surface formed around a rotating shaft, a stator having a driving surface formed coaxially with the rotating shaft and in contact with the driven surface, and a plurality of regions obtained by dividing the driving surface in the circumferential direction And a drive unit that generates a traveling wave traveling in the circumferential direction on the driving surface by displacing in a radial direction with mutually different phases, and the traveling wave generated in the stator by the driving unit rotates the rotor around the rotation axis. In the vibration actuator, the driving surface may transmit the driving force in contact with the driven surface at a plurality of locations symmetrical to the rotation axis.

Description

The present invention relates to a vibration actuator and an imaging apparatus. More specifically, the present invention relates to a vibration actuator having an electromechanical conversion unit formed using an electromechanical conversion element, and an imaging device including the vibration actuator. This application is related to the following Japanese application. For designated countries where incorporation by reference of documents is permitted, the contents described in the following application are incorporated into this application by reference and made a part of this application.
Japanese Patent Application No. 2007-302286 Filing Date November 21, 2007

  The vibration actuator converts the vibration generated by the drive unit into a specific motion or the like and transmits it to the outside. The drive unit includes a piezoelectric element or the like, and generates vibrations when a drive voltage that periodically changes is applied.

  Patent Document 1 describes an ultrasonic motor including an electromechanical conversion unit in which a plurality of piezoelectric elements polarized in different directions are stacked. This ultrasonic motor generates a circular motion at the tip of a round bar by applying drive voltages having different phases to a plurality of piezoelectric elements.

Patent Document 2 describes a vibration wave driving device including a piezoelectric element having a plurality of polygonal electrode films. This vibration wave driving device generates a circular motion in the rotor by applying a driving voltage to each of the electrode films.
Japanese Patent Laid-Open No. 03-289375 JP 2006-179578 A

  However, the vibration actuators described in Patent Document 1 and Patent Document 2 have a structure in which a circular rod or rotor that moves circularly and a piezoelectric element are stacked in the axial direction. For this reason, the thickness of a member accumulates and the dimension of an axial direction becomes long.

  In order to solve the above problems, as a first aspect of the present invention, a rotor having a cylindrical driven surface formed around a rotation shaft, and a driving surface formed coaxially with the rotation shaft and in contact with the driven surface And a drive unit for generating a traveling wave traveling in the circumferential direction on the drive surface by displacing a plurality of regions obtained by dividing the drive surface in the circumferential direction in a radial direction with mutually different phases. A vibration actuator is provided in which traveling waves generated in the stator rotate the rotor about a rotation axis.

  In the vibration actuator, the driving surface may transmit the driving force in contact with the driven surface at a plurality of locations symmetrical to the rotation axis.

  Further, in the vibration actuator, the stator has a hollow cylindrical driving surface coaxial with the driven surface, and the rotor is arranged on the inner side of the stator so that the driven surface contacts the driving surface from the inner side. Good.

  Further, in the vibration actuator, the rotor may include an elastic member that causes a deformation that expands the diameter and presses the driven surface against the driving surface when pressurized in the direction of the rotation axis.

  Furthermore, in the vibration actuator, the rotor may include a disc spring that is inserted around the rotation axis.

  Still further, in the vibration actuator, the rotor may include a pair of disc springs that are inserted about the rotation axis and are arranged to face each other so that the peripheral edges are in contact with each other.

  Furthermore, in the vibration actuator, the drive unit may include an electromechanical conversion element that is disposed on the back surface of the drive surface and expands and contracts in the circumferential direction.

  Still further, in the above vibration actuator, the stator is in contact with the peripheral edge of the disc spring by extending from the end of the disc in a direction parallel to the rotational axis, and in the direction perpendicular to the rotational axis. The disc spring may be spaced apart from the disc portion.

  Further, as a second aspect of the present invention, the above-described vibration actuator, an optical member, a lens barrel that houses the optical member, and a lens unit that is provided inside the lens barrel and has a vibration actuator that drives the optical member. And an imaging unit that captures an image formed by the lens unit, and a control unit that controls the vibration actuator and the imaging unit.

  The above summary of the present invention does not enumerate all necessary features of the present invention. Further, a sub-combination of these feature groups can be an invention.

It is an exploded perspective view of vibration actuator 100 concerning one embodiment. 2 is a longitudinal sectional view of the vibration actuator 100. FIG. FIG. 6 is a plan view showing the operation of the drive unit 160. FIG. 6 is a diagram illustrating a phase relationship of driving power supplied to a driving unit 160. FIG. 5 is a plan view for explaining the action of a stator 150 on a rotor 140. 6 is a longitudinal sectional view showing another structure of the vibration actuator 100. FIG. 6 is a longitudinal sectional view showing still another structure of the vibration actuator 100. FIG. It is a perspective view which shows the other shape of the stator 150 independently. It is a perspective view which shows the other shape of the stator 150 independently. It is a perspective view which shows the other form of the stator 150. FIG. 3 is a plan view of a stator 150. FIG. 6 is a cross-sectional view showing still another structure of the vibration actuator 100. FIG. It is a perspective view which shows the form of the stator 150 and the drive part 160. FIG. 3 is a plan view of a stator 150 and a drive unit 160. FIG. 10 is a cross-sectional view showing still another structure of the vibration actuator 100. FIG. FIG. 3 is a perspective view showing structures of a stator 150 and a drive unit 160. 2 is a schematic cross-sectional view of an imaging apparatus 400 that includes a vibration actuator 100. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Vibration actuator, 110 Rotating shaft, 111, 113 Screw groove part, 112 Nut, 115 Level difference part, 117 Locking groove, 119 Retaining part, 120 Upper case, 122 Cover part, 124 Bearing part, 130 Holding member, 132 Washer, 134 Pressing Spring, 140 Rotor, 142 Disc Spring, 141 Insertion Hole, 143 Locking Projection, 145 Driven Surface, 150 Stator, 151 Vertical Groove, 152 Drive Surface, 153 Slit, 154 Disc, 155 Thread, 156, 262 Square hole, 157 ring screw, 158, 159 notch, 160 drive part, 161, 162, 163, 164, 165, 166, 167, 168 electrode, 169 piezoelectric material plate, 170 lower case, 172 cup part, 174 shaft support Hole, 176 Anti-rotation part, 178 Support Surface, 180 gears, 182 teeth, 184 shaft hole, 400 imaging device, 410 lens unit, 420 optical member, 422 front lens, 424 compensator lens, 426 focusing lens, 428 main lens, 430 lens barrel, 440 iris unit, 450 Mount, 460 Body, 470 Penta prism, 472 Focusing screen, 480 Metering unit, 490 Eyepiece system, 492 Half mirror, 494 Finder liquid crystal, 500 Image sensor, 510 Optical filter, 520 Shutter, 530 Distance measuring unit, 540 Main mirror, 542 Sub mirror, 550 controller

  Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the claimed invention. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is an exploded perspective view of a vibration actuator 100 according to an embodiment. In the following description, for convenience of description, the direction “up” or “down” may be described in accordance with the display of the drawings. However, these descriptions do not mean that the vibration actuator 100 is used only in the illustrated direction.

  The vibration actuator 100 includes a rotation shaft 110, a nut 112, an upper case 120, a pressing member 130, a rotor 140, a stator 150, a driving unit 160, a lower case 170, and a gear 180. The gear 180 is a pinion gear having teeth 182 on the peripheral surface, and has a shaft hole 184 in the center. The vibration actuator 100 rotationally drives another gear engaged with the tooth portion 182.

  The rotating shaft 110 has a cylindrical shape as a whole, and includes screw groove portions 111 and 113, a step portion 115, a locking groove 117, and a retaining portion 119. One screw groove 111 is formed adjacent to the upper end of the rotating shaft 110. A nut 112 is screwed into the thread groove portion 111.

  The other thread groove 113 is formed in the middle in the longitudinal direction of the rotating shaft 110. A pressing member 130 is screwed into the screw groove 113. The pressing member 130 screwed into the thread groove 113 can move in the axial direction of the rotating shaft 110 by rotating.

  The step portion 115 is formed on the upper surface of the portion whose diameter is larger than the other portion of the rotation shaft, and is disposed slightly below the middle of the rotation shaft 110. Further, the locking groove 117 is formed in the axial direction over the entire length of the rotating shaft 110. The retaining portion 119 is formed in a flange shape at the lower end of the large diameter portion formed below the step portion 115.

  The upper case 120 includes a cover part 122 and a bearing part 124. The cover part 122 has a cylindrical shape whose upper end is closed by a disk. The bearing portion 124 is arranged at the center of the disk-shaped portion and pivotally supports the upper end side of the inserted rotating shaft 110.

  The lower case 170 includes a cylindrical cup portion 172 whose lower end is closed by a disk. A shaft support hole 174, a detent portion 176, and a support surface 178 are formed on the bottom surface of the cup portion 172. The shaft support hole 174 is formed through the center of the bottom surface of the cup portion 172 and supports the lower end side of the inserted rotation shaft 110.

  The support surface 178 is formed around the shaft support hole 174 and has a flat horizontal surface raised from the bottom surface of the cup portion 172. The detent portion 176 has a side surface that further protrudes from the support surface 178 and forms a quadrangular prism. In addition, the shape of the rotation prevention part 176 should just be non-circular, and is not limited to a square pillar.

  The rotor 140 includes a disc spring 142 whose center portion swells upward and a disc spring 142 whose center portion swells downward. The pair of disc springs 142 have the same shape and dimensions.

  Each of the disc springs 142 has an insertion hole 141 formed in the center, and a locking projection 143 protruding in the radial direction toward the inside of the insertion hole 141. The inner diameter of the insertion hole 141 is slightly larger than the outer diameter of the small diameter portion of the rotating shaft 110. The locking protrusion 143 has a shape complementary to the horizontal cross-sectional shape of the locking groove 117. The outer peripheral surface of the disc spring 142 is a driven surface 145 that receives a driving force from the stator 150.

  The stator 150 has a cylindrical shape whose lower end is closed by a disk-shaped disk portion 154. The disc portion 154 has a square hole 156 having a shape complementary to the anti-rotation portion 176 at the center. The inner peripheral surface of the cylindrical portion forms a drive surface 152 having an inner diameter that is substantially the same as the outer diameter of the rotor 140.

  The drive unit 160 includes a piezoelectric material plate 169 and a plurality of electrodes 161 to 168. The piezoelectric material plate 169 forms a disc having an outer diameter substantially the same as the outer diameter of the stator 150. Further, the piezoelectric material plate 169 has a square hole 156 having a shape complementary to the rotation stopper 176 at the center.

  The electrodes 161 to 168 each have a sector shape that equally divides the circular surface of the piezoelectric material plate 169 in the circumferential direction, and are arranged on one surface of the piezoelectric material plate 169 so as to be separated from each other. Although not visible in the drawing, a continuous single common electrode is formed on the entire circular surface of the piezoelectric material plate 169 opposite to the electrodes 161 to 168.

  FIG. 2 is a longitudinal sectional view showing the structure of the vibration actuator 100. The vibration actuator 100 is formed inside a housing formed by combining the lower case 170 and the upper case 120. Inside the housing, a drive unit 160, a stator 150, a rotor 140, and a pressing member 130 arranged in order from the bottom are arranged along the rotation shaft 110 inserted through the center.

  The rotating shaft 110 is pivotally supported from the cover portion 122 via a bearing portion 124. A nut 112 is screwed onto the upper end of the rotating shaft 110 to prevent the bearing shaft 124 from falling off. Further, the retaining portion 119 comes into contact with the lower surface of the lower case 170 and restrains the upward displacement of the rotating shaft 110. The gear 180 is attached to the lower end of the rotating shaft 110 protruding downward from the lower case 170 and rotates together with the rotating shaft 110.

  The driving unit 160 and the stator 150 are fitted with respective square holes 262 and 156 with respect to the rotation preventing unit 176 around the rotating shaft 110. Accordingly, the driving unit 160 and the stator 150 do not rotate with respect to the lower case 170. Since the drive unit 160 is orthogonal to the rotation shaft 110, the region defined on the piezoelectric material plate 169 by the electrodes 161 to 168 is arranged in the circumferential direction in a plane perpendicular to the rotation shaft 110.

  The stator 150 is arranged coaxially with the rotary shaft 110 such that the drive surface 152 extends upward with respect to the disc portion 154. The stator 150 has a disc portion 154 disposed in a plane perpendicular to the rotation shaft 110, and a drive that extends from the end of the disc portion 154 in a direction parallel to the rotation shaft 110 and contacts the peripheral edge of the disc spring 142. A cylindrical portion having a surface 152 on the inner surface. As a result, a continuous cylindrical driving surface 152 facing the rotation shaft 110 is formed. The drive unit 160 and the stator 150 are bonded and integrated with each other. Therefore, when the drive unit 160 is deformed, the stator 150 is also deformed.

  The rotor 140 has a disc spring 142. A pair of disc springs 142 are arranged face to face so that their peripheral edges are in contact with each other. As a result, the forces in the direction parallel to the rotating shaft 110 acting on the disc spring 142 cancel each other, and the peripheral edge of the disc spring 142 reliably contacts the drive surface 152.

  The rotation shaft 110 is directly inserted into the insertion hole 141. The inner diameter of the insertion hole 141 is slightly larger than the outer diameter of the rotating shaft 110. Accordingly, each of the disc springs 142 is freely displaced in the axial direction with respect to the rotating shaft 110. However, since the locking protrusion 143 fits in the locking groove 117, the rotation direction about the rotation shaft 110 rotates integrally with the rotation shaft 110.

  Furthermore, the inner diameter of the insertion hole 141 is smaller than the outer diameter of the step portion 115 of the rotating shaft 110. Therefore, the lower disc spring 142 remains on the step portion 115 and does not descend. In this manner, the disc spring 142 is disposed away from the disc portion 154. As a result, a gap is generated between the rotor 140 and the stator 150 and does not hinder different deformations or displacements. Further, the disc spring 142 rotates efficiently without sliding resistance against the disc portion 154.

  The pressing member 130 is screwed into the thread groove 113 of the rotating shaft 110 and abuts the upper disc spring 142 on the lower surface. Since the pressing member 130 is displaced in the axial direction when it is rotated, the rotor 140 can be pressed from above by tightening the pressing member 130.

  When pressed down from above by the pressing member 130, the disc spring 142 receives a pressing force in a direction parallel to the rotation shaft 110 from the pressing member 130. The rotor 140 receiving the pressing force is deformed and expands in the radial direction. As a result, the driven surface 145 of the disc spring 142 is pressed toward the driving surface 152 of the stator 150. Since the rotor 140 is rotatably mounted with the rotation shaft 110 as an axis, the rotor 140 receives the traveling wave generated by the stator 150 and rotates.

  Note that the vibration actuator 100 as described above can be mounted in an inverted state with respect to the direction shown in FIG. 2 to open the stator 150 downward. Thereby, dust generated by sliding of the rotor 140 and the stator 150 can be prevented from accumulating in the cup-shaped stator 150.

  FIG. 3 is a plan view for explaining the structure and operation of the drive unit 160. When there is no potential difference between any of the electrodes 161 to 168 and the common electrode, the piezoelectric material plate 169 has a circular shape as shown in FIG.

  On the other hand, for example, when a potential difference is generated between the common electrode maintained at the ground potential and a pair of electrodes symmetric with respect to the square hole 262, for example, the electrodes 163 and 167, the electrode 163 to which a voltage is applied. , 167, the piezoelectric material plate 169 expands due to the inverse piezoelectric effect generated in the region including it. As a result, as shown in FIG. 3B, the diameter of the piezoelectric material plate 169 increases in the arrangement direction of the electrodes 163 and 167 to which a voltage is applied. Since the drive unit 160 and the stator 150 are integrated by bonding, the deformation of the drive unit 160 is reflected in the stator 150 as well.

  FIG. 4 is a diagram illustrating a waveform of the drive voltage supplied to the drive unit 160. An AC voltage having the same phase θ is applied to the electrodes 161 to 168 positioned symmetrically with respect to the square hole 262. In addition, an alternating voltage having a phase θ sequentially delayed by 90 ° is applied to the electrodes 161 to 168 adjacent to each other. As a result, the drive unit 160 expands and contracts the regions divided in the circumferential direction in the radial direction with different phases.

  FIG. 5 is a diagram for explaining the operation of the stator 150 that occurs when a drive voltage is applied and the action on the rotor 140. 5A, FIG. 5B, FIG. 5C, and FIG. 5D, the arrows written between them indicate that the state transition of the stator 150 circulates and operates periodically. Indicates to do.

  The stator 150 bonded to the driving unit 160 has elasticity. Therefore, as indicated by an arrow E in the figure, when the diameter of the drive unit 160 in a certain direction is increased, the diameter of the stator 150 is also increased in the direction of the arrow E, and the contact between the rotor 140 and the stator 150 is weakened. On the other hand, the rotor 140 and the stator 150 are in strong contact with each other at a point C that intersects the diameter perpendicular to the elongated diameter.

  Further, since the driving voltage applied to each of the electrodes 161 to 168 sequentially changes with the passage of time, a portion where the diameter of the stator 150 becomes longer is indicated in the circumferential direction of the stator 150 as indicated by an arrow M in the drawing. Moving. As a result, as shown in FIGS. 5A to 5D, traveling waves that cause radial expansion and contraction to proceed in the circumferential direction are generated in the stator 150.

  The vibration actuator 100 converts the vibration energy of the stator 150 into rotation of the rotor 140 by a frictional force. That is, at each position of the contact portion of the rotor 140 with respect to the stator 150 where the traveling wave is generated, the stator 150 microscopically generates an elliptical motion.

  As a result, a fixed region and a sliding region are distributed in the contact portion between the stator 150 and the rotor 140. In the fixed region, the stator 150 and the rotor 140 are displaced at the same speed. On the other hand, in the sliding region, the speeds of the stator 150 and the rotor 140 are different, and sliding loss occurs. The rotor 140 rotates according to these differences.

  In order to improve the efficiency of such rotational drive, it is required to press the rotor 140 against the stator 150 with an appropriate strength. In this respect, the vibration actuator 100 can change the amount of deformation of the disc spring 142 according to the amount of tightening of the pressing member 130 and can press against the stator 150 with an appropriate strength.

  In addition, a voltage is applied to the electrodes 161 to 168 positioned symmetrically with respect to the rotation axis 110. Therefore, the stator 150 transmits a driving force to the rotor 140 at a plurality of locations that are symmetrical with respect to the rotation shaft 110. Thereby, since the radial force acting on the rotor 140 cancels out, the rotating shaft 110 is not easily shaken.

  In the present embodiment, the piezoelectric material plate 169 is divided into eight in the circumferential direction by the electrodes 161 to 168. However, it goes without saying that the number of divisions is not limited to eight, and traveling waves can be generated if the number of divisions is three or more. However, considering that the driving force is transmitted to the rotor 140 at a position symmetric with respect to the rotating shaft 110, the number of divisions is preferably an even number.

  The piezoelectric material plate 169 can be formed of lead zirconate titanate, crystal, lithium niobate, barium titanate, lead titanate, lead metaniobate, lead zinc niobate, lead scandium niobate, etc., but is not limited thereto. It is not something. Furthermore, although a piezoelectric material is used in this embodiment, an electrostrictive material such as a PNN-PT (Pb (Ni, Nb) O3-PbTiO3) system or a PMN-PT (Pb (Mg, Nb) O3-PbTiO3) system is used. The driving unit 160 can be formed using the same.

  FIG. 6 is a cross-sectional view illustrating a modification of the vibration actuator 100 illustrated in FIGS. 1 and 2. Except for the points described below, the vibration actuator 100 has the same structure as that of the vibration actuator 100 shown in FIGS. Therefore, common elements are denoted by the same reference numerals, and redundant description is omitted.

  The vibration actuator 100 includes a pressing spring 134 instead of the pressing member 130 as a member that presses the disc spring 142 as the rotor 140. Accordingly, the disc spring 142 can be pressed without the work of screwing the pressing member 130, and a pressure can be applied to the stator 150. Therefore, the productivity of the vibration actuator 100 is improved.

  In addition, the vibration actuator 100 includes a washer 132 interposed between the presser spring 134 and the disc spring 142. As a result, the rotor 140 (the disc spring 142) can be smoothly rotated while being pressed by the holding spring 134 that is in contact with the cover portion 122 whose upper end does not rotate.

  FIG. 7 is a cross-sectional view showing the structure of a vibration actuator 100 according to another embodiment. Except for the points described below, the vibration actuator 100 has the same structure as the vibration actuator 100 shown in FIGS. 1 and 2. Therefore, common elements are denoted by the same reference numerals, and redundant description is omitted.

  The vibration actuator 100 includes a single disc spring 142 as the rotor 140. The disc spring 142 is mounted in a state of swelling upward, and is inserted through the rotating shaft 110.

  A pressing member 130 is attached directly above the disc spring 142 along the rotation shaft 110. The pressing member 130 is screwed into the screw groove 113. The pressing member 130 tightened downward pushes down the central portion of the disc spring 142. As a result, the disc spring 142 is deformed and expands in the radial direction, and the driven surface 145 is pressed against the driving surface 152.

  In the vibration actuator 100, vibration generated in the drive unit 160 when a drive voltage is supplied is transmitted to the disc spring 142 via the stator 150. As a result, the disc spring 142 rotates to rotate the rotating shaft 110 via the locking projection 143.

  Note that the edge of the disc spring 142 including the driven surface 145 is slightly bent downward. Thereby, the contact with the disc part 154 which becomes resistance about rotation of the disc spring 142 is stopped to the minimum.

  Thus, the vibration actuator 100 can be formed using the single disc spring 142. Thereby, the number of parts can be reduced, and the material cost of the vibration actuator 100 can be reduced. In addition, this contributes to downsizing of the vibration actuator 100, in particular, reduction of the axial dimension.

  FIG. 8 is a perspective view showing another shape of the stator 150 that can be used in the vibration actuator 100. The stator 150 includes a disc portion 154 having a square hole 156 at the center, and a drive surface 152 that stands up in the axial direction of the vibration actuator 100 at the edge of the disc portion 154. The drive surface 152 is arranged at equal intervals in the circumferential direction of the disc portion 154 and is divided by a large number of cuts 158 formed in the axial direction. As a result, the bending rigidity of the driving surface is reduced, and the deformation of the driving unit 160 is easily reflected in the deformation of the stator 150.

  FIG. 9 is a perspective view showing still another shape of the stator 150 that can be used in the vibration actuator 100. The stator 150 includes a disc portion 154 having a square hole 156 at the center, and a drive surface 152 that stands up in the axial direction of the vibration actuator 100 at the edge of the disc portion 154. The inner peripheral surface and the outer peripheral surface of the drive surface 152 have a large number of vertical grooves 151 formed in the axial direction at equal intervals in the circumferential direction of the disc portion 154. As a result, the bending rigidity of the driving surface is reduced, and the deformation of the driving unit 160 is easily reflected in the deformation of the stator 150.

  FIG. 10 is a perspective view showing still another form of the stator 150 that can be used in the vibration actuator 100. As illustrated, the stator 150 has a plurality of slits 153 formed in the disk portion 154.

  FIG. 11 is a plan view of the stator 150 shown in FIG. Each of the slits 153 forms an arc concentrically arranged with respect to the center of the stator 150. By providing such a slit 153, the radial rigidity of the stator 150 is reduced, and the stator 150 is easily deformed in the radial direction. Therefore, a traveling wave is efficiently generated on the drive surface 152 by the vibration generated by the disk-shaped drive unit 160.

  In the illustrated example, concentric arc-shaped slits 153 are provided in the disk portion 154 of the stator 150. However, the structure for changing the rigidity of the stator 150 is not limited to this. For example, other structures may be selected, such as forming concentric corrugations (wave-shaped corrugations) on the disk portion 154.

  FIG. 12 is a cross-sectional view showing still another structure of the vibration actuator 100. Except for the points described below, the vibration actuator 100 has the same structure as that of the vibration actuator 100 shown in FIGS. 1 and 2. Therefore, common elements are denoted by the same reference numerals, and redundant description is omitted.

  The vibration actuator 100 includes a driving unit 160 formed in an annular shape on the outer peripheral surface of the stator 150, that is, the back surface of the driving surface 152, instead of the disk-shaped driving unit 160. The annular drive unit 160 is integrally formed on the outer peripheral surface of the stator 150. When the drive unit 160 is deformed, the stator 150 is also deformed.

  FIG. 13 is a perspective view showing forms of the stator 150 and the drive unit 160 used in the vibration actuator 100 shown in FIG. The drive unit 160 formed on the outer peripheral surface of the stator 150 further includes a plurality of electrodes 161 to 168 on the outer peripheral surface.

  Such a drive unit 160 can be formed, for example, by synthesizing a piezoelectric material by a hydrothermal synthesis method using a stator as a base material. In the hydrothermal synthesis method, since the piezoelectric material layer is deposited on the entire surface of the substrate, the driving unit 160 as shown in the figure can be formed by removing unnecessary portions by machining such as cutting and polishing. The electrodes 161 to 168 can be formed, for example, by applying a conductive material paste in accordance with an electrode pattern.

  FIG. 14 is a plan view of stator 150 and drive unit 160 shown in FIG. As described above, the electrodes 161 to 168 are formed separately from each other in an area obtained by dividing the outer peripheral surface of the stator 150 into eight. By applying the drive voltage having the waveform shown in FIG. 4 to the electrodes 161 to 168, the drive surface 152 of the stator 150 is circulated similarly to the vibration actuator 100 shown in FIGS. A traveling wave is generated. Thereby, the rotor 140 can be rotated.

  In such a structure, the drive unit 160 is disposed in the immediate vicinity of the drive surface 152. Thereby, the traveling wave generated by the driving unit 160 vibrates the driving surface 152 efficiently. The driven surface 145 of the disc spring 142 is preferably in contact with the approximate center of the height of the driving surface 152. Thereby, the vibration of the drive surface 152 is stabilized.

  FIG. 15 is a cross-sectional view showing a modification of the vibration actuator 100 shown in FIGS. Except for the points described below, the vibration actuator 100 has the same structure as the vibration actuator 100 shown in FIG. Therefore, common elements are denoted by the same reference numerals, and redundant description is omitted.

  In this vibration actuator 100, the rotor 140 forms a disk. The rotor 140 has high rigidity that does not deform except inevitable vibration.

  The inner periphery of the rotor 140 is fastened by the pressing member 130 and fixed to the rotating shaft 110. Thereby, the rotor 140 and the rotating shaft 110 rotate integrally. The outer peripheral surface of the rotor 140 abuts on a driving surface 152 formed on the inner peripheral surface of the stator 150 as a driven surface 145.

  The stator 150 has a drive unit 160 on the outer peripheral surface that contacts the back surface of the drive surface 152. Further, the drive surface 152 extends upward, and the outer peripheral surface thereof has a taper shape whose diameter decreases as it goes upward. Further, a thread 155 is disposed on the outer peripheral surface of the extended portion of the drive surface 152. Furthermore, the stator 150 has a ring screw 157 that is screwed into the screw thread 155.

  16 is a perspective view showing the structure of the stator 150 and the drive unit 160 used in the vibration actuator shown in FIG. As shown in the drawing, a plurality of cuts 159 formed in a direction parallel to the rotation shaft 110 are disposed in the extended portion of the drive surface 152.

  As a result, when the ring screw 157 is tightened, a tightening force is generated in a direction in which the inner diameter of the drive surface 152 decreases. Therefore, in the vibration actuator 100 shown in FIG. 15, the pressure applied to the contact portion between the stator 150 and the rotor 140 can be adjusted by adjusting the ring screw 157.

  The driving unit 160 includes a plurality of electrodes 161 to 168 on the outer peripheral surface. The electrodes 161 to 168 are formed by dividing the outer peripheral surface of the stator 150 into eight parts. By applying the drive voltage having the waveform shown in FIG. 4 to the electrodes 161 to 168, the drive surface 152 of the stator 150 is circulated similarly to the vibration actuator 100 shown in FIGS. A traveling wave is generated. Thereby, the rotor 140 can be rotated.

  FIG. 17 is a vertical cross-sectional view schematically showing the structure of the imaging device 400 provided with the vibration actuator 100. The imaging device 400 includes a lens unit 410 and a body 460.

  The lens unit 410 is detachably attached to the body 460 via the mount 450. The lens unit 410 includes an optical member 420, a lens barrel 430 that houses the optical member 420, and the vibration actuator 100 that is provided inside the lens barrel 430 and drives the optical member 420. On the other hand, the body 460 has an optical system including a main mirror 540, a pentaprism 470, and an eyepiece system 490.

  The main mirror 540 is located between a standby position inclined on the optical path of incident light incident through the lens unit 410 and an imaging position (indicated by a dotted line in the figure) that rises while avoiding incident light. Moving. The main mirror 540 at the standby position guides most of the incident light to the pentaprism 470 disposed above. Since the pentaprism 470 emits a reflection of incident light toward the eyepiece system 490, the image on the focusing screen 472 can be viewed as a normal image from the eyepiece system 490.

  The remainder of the incident light is guided to the photometric unit 480 by the pentaprism 470. The photometric unit 480 measures the intensity and intensity distribution of incident light. A half mirror 492 that superimposes the display image formed on the finder liquid crystal 494 on the image from the focusing screen 472 is disposed between the pentaprism 470 and the eyepiece system 490.

  The main mirror 540 has a sub mirror 542 on the back surface of the incident light incident surface. The sub mirror 542 guides part of the incident light transmitted through the main mirror 540 to the distance measuring unit 530 disposed below. Thereby, when the main mirror 540 is in the standby position, the distance measuring unit 530 measures the distance to the subject. When the main mirror 540 is moved to the photographing position, the sub mirror 542 is also retracted from the optical path of the incident light.

  Further, a shutter 520, an optical filter 510, and an image sensor 500 are sequentially arranged behind the main mirror 540 with respect to incident light. When the shutter 520 is opened, the main mirror 540 moves to the shooting position immediately before, so that the incident light goes straight and enters the image sensor 500. Thereby, an image formed by incident light is converted into an electrical signal.

  On the other hand, the lens unit 410 has an optical system including a front lens 422, a compensator lens 424, a focusing lens 426, and a main lens 428, which are sequentially arranged in the lens barrel 430 from an incident end corresponding to the left side in the drawing. The optical system is accommodated in the lens barrel 430. Further, an iris unit 440 is disposed between the focusing lens 426 and the main lens 428.

  Further, the lens unit 410 includes the vibration actuator 100 inside the lens barrel 430. The vibration actuator 100 is disposed in the middle of the lens barrel 430 in the optical axis direction and below the focusing lens 426 having a relatively small diameter. As a result, the vibration actuator 100 is accommodated in the lens barrel 430 without increasing the diameter of the lens barrel 430. The vibration actuator 100 advances or retracts the focusing lens 426 in the optical axis direction via a train wheel not shown.

  Here, in the middle of the optical member 420 in the optical axis direction, the diameter of the focusing lens 426 and the like decreases. Therefore, it is easy to take a space in the lens barrel and easily accommodate the vibration actuator 100. Furthermore, since the vibration actuator 100 has a small axial dimension, even the short-focus lens unit 410 having a limited space in the optical axis direction can be easily accommodated inside the lens barrel 430.

  Furthermore, the body 460 includes a control unit 550 at a position inside the body 460 and off the optical path of the optical system. The control unit 550 controls not only the operation of each part inside the body 460 but also the operation of members including the vibration actuator 100 inside the lens unit 410 by transmitting and receiving electrical signals via the mount 450.

  Accordingly, the control unit 550 controls the amount of rotation of the vibration actuator 100 based on, for example, information on the distance to the subject detected by the distance measuring unit 530 on the body 460 side, thereby forming an autofocus mechanism. Further, when the distance measuring unit 530 refers to the operation amount of the vibration actuator 100, a focus aid mechanism can be formed.

  Although the case where the focusing lens 426 is moved by the vibration actuator 100 has been illustrated, it goes without saying that the opening / closing of the iris unit 440, the variator lens of the zoom lens, and the like can be driven by the vibration actuator 100. Also in this case, the control unit 550 refers to the information of the photometry unit 480, the finder liquid crystal 494, etc., and controls the vibration actuator 100 with an electric signal to execute automatic exposure, scene mode, bracket photographing, and the like.

  The vibration actuator 100 can be suitably used for driving a focusing mechanism, a zoom mechanism, a camera shake correction mechanism, and the like in an optical system such as a photographing machine and binoculars. Moreover, the vibration actuator 100 can be advantageously used, for example, as a drive source for a precision positioning device. More specifically, an electron beam drawing device, various stages for inspection devices, a focusing mechanism for optical devices, a camera shake correction mechanism for an imaging device, a zoom drive mechanism, a movement mechanism for a cell injector for biotechnology, a movement of a nuclear magnetic resonance device It can be used for power sources such as a bed, but it goes without saying that the application is not limited thereto.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Moreover, it will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. Further, it is apparent from the scope of the claims that the embodiments added with changes or improvements can be included in the technical scope of the present invention.

Claims (9)

A rotor having a cylindrical driven surface formed around a rotation axis;
A stator having a driving surface formed coaxially with the rotating shaft and in contact with the driven surface;
A drive unit that generates a traveling wave that travels in the circumferential direction on the drive surface by displacing a plurality of regions obtained by dividing the drive surface in the circumferential direction in a radial direction with mutually different phases; A vibration actuator in which a traveling wave generated in the stator rotates the rotor around the rotation axis.   2. The vibration actuator according to claim 1, wherein the driving surface is in contact with the driven surface at a plurality of positions symmetrical to the rotation axis and transmits a driving force. The stator has a hollow cylindrical driving surface coaxial with the driven surface,
The vibration actuator according to claim 1, wherein the rotor is arranged inside the stator and causes the driven surface to contact the driving surface from the inside.   4. The vibration actuator according to claim 3, wherein the rotor includes an elastic member that deforms to expand the diameter and press the driven surface against the driving surface when pressed in the direction of the rotation shaft. 5.   The vibration actuator according to claim 4, wherein the rotor includes a disc spring inserted through the rotation shaft.   6. The vibration actuator according to claim 5, wherein the rotor includes a pair of disc springs that are inserted around the rotation shaft and are arranged to face each other so that peripheral edges thereof are in contact with each other.   The vibration actuator according to claim 1, wherein the drive unit includes an electromechanical conversion element that is disposed on a back surface of the drive surface and expands and contracts in the circumferential direction. The stator includes a disc portion disposed in a plane perpendicular to the rotation axis, and a cylindrical portion that extends from an end portion of the disc in a direction parallel to the rotation axis and contacts the periphery of the rotor. Have
The vibration actuator according to any one of claims 1 to 7, wherein the rotor is disposed apart from the disk portion. A vibration actuator according to any one of claims 1 to 8,
An optical member, a lens barrel that houses the optical member, and a lens unit that is provided inside the lens barrel and has a vibration actuator that drives the optical member;
An imaging unit that captures an image formed by the lens unit;
An imaging apparatus comprising: the vibration actuator and a control unit that controls the imaging unit.

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