Ultrasonic motor, drive device, imaging device

Abstract

To exhibit stable drive characteristics with a simple configuration.SOLUTION: A guide mechanism 5 guides the rotation of a rotating member 3 with respect to a fixed member 4 between the fixed member 4 and the rotating member 3 in the direction of a rotating shaft 8a. A first biasing portion 6 presses a vibrator 2 against a friction surface 3a of the rotating member 3, thereby biasing the rotating member 3 and the guide mechanism 5 against the fixed member 4 in the direction of the rotating shaft 8a. Further, a second biasing portion 7 biases the rotating member 3 and the guide mechanism 5 against the fixed member 4 in the direction of the rotating shaft 8a by magnetic force.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ultrasonic motor, a driving device, and an imaging device. [Background technology]

[0002] In general, ultrasonic motors are configured so that the contact part of a vibrator, which is made by bonding a piezoelectric element and an elastic body, is in a pressure contact state with a friction member (or friction surface). When ultrasonic vibration is excited in the vibrator by applying a two-phase AC voltage to the piezoelectric element under this pressure contact state, an elliptical motion occurs in the vibrator, and the vibrator and the friction member move relatively.

[0003] There is known an ultrasonic motor that uses one of these vibrators to rotate a rotating member, which is a ring-shaped or disk-shaped friction member (Patent Documents 1, 2, and 3). In this type of ultrasonic motor, the vibrator comes into contact with a flat surface in the direction of the rotation axis of the rotating member, or a side surface perpendicular to the rotation axis.

[0004] When a rotating member is rotated using one transducer, only the portion of the rotating member that is in contact with the transducer is biased, which may cause the rotating member to wobble. Therefore, the ultrasonic motor of Patent Document 1 suppresses wobble of the rotating member in the direction of the rotation axis by biasing the surface of the rotating member opposite the transducer in the direction of the rotation axis with a biasing spring via a bearing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2006-158054 A [Patent Document 2] JP 2004-304887 A [Patent Document 3] JP 2005-073465 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the ultrasonic motor of Patent Document 1 has a large number of parts such as bearings and has a complex structure. In addition, the ultrasonic motors of Patent Documents 2 and 3 cannot suppress wobble in either the direction of the rotation axis of the rotating member or the direction perpendicular to the rotation axis. Therefore, there is room for improvement in terms of obtaining stable motor characteristics with a simple configuration.

[0007] An object of the present invention is to provide stable driving characteristics with a simple configuration. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the present invention is characterized by comprising a vibrator in which ultrasonic vibrations are excited, a rotating member having a friction surface and at least a portion which is magnetic, and which rotates about a rotation axis when the friction surface is driven by the vibrator, a fixed member which rotatably holds the rotating member, a guide mechanism which is disposed between the fixed member and the rotating member in the rotation axis direction and which guides the rotation of the rotating member relative to the fixed member, a first biasing means which biases the rotating member and the guide mechanism against the fixed member in the rotation axis direction by pressing the vibrator against the friction surface of the rotating member, and a second biasing means which biases the rotating member and the guide mechanism against the fixed member in the rotation axis direction by magnetic force. Effect of the Invention

[0009] According to the present invention, stable driving characteristics can be achieved with a simple configuration. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic vertical cross-sectional view of the imaging device. [Diagram 2] FIG. 2 is a diagram showing a vibration mode of the vibrator, illustrating elliptical vibration of the protrusion. [Diagram 3] FIG. 2 is a schematic vertical cross-sectional view of the imaging device. [Figure 4] FIG. 11 is a vertical cross-sectional view of an imaging device of a comparative example. [Diagram 5] FIG. 2 is a schematic longitudinal sectional view of the imaging device, taken along line BB. [Figure 6] FIG. 2 is a schematic vertical cross-sectional view of the imaging device. [Figure 7] FIG. 2 is a schematic longitudinal sectional view of the imaging device, taken along line CC. [Figure 8] FIG. 2 is a schematic vertical cross-sectional view of the imaging device. [Figure 9] 11A and 11B are schematic vertical cross-sectional views of imaging devices according to first and second modified examples. [Figure 10] FIG. 13 is a schematic vertical cross-sectional view of an imaging device according to a third modified example. [Figure 11] 2 is a schematic vertical cross-sectional view of a main part of the imaging device. FIG. [Figure 12] FIG. 13 is a schematic enlarged partial view showing a modified example of the ultrasonic motor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] (First embodiment) A first embodiment of the present invention will be described with reference to Figs. 1 to 4. Figs. 1(a) and (b) are schematic longitudinal sectional views of an imaging device to which an ultrasonic motor of the present embodiment is applied. Fig. 1(b) is a sectional view taken along line AA in Fig. 1(a). Note that the diagonal lines indicating the cross sections in Fig. 1(a) have been omitted.

[0013] The imaging device 1 includes a rotating camera 8 and an ultrasonic motor 16. The ultrasonic motor 16 includes a fixed member 4, a transducer 2, a rotating member 3, a first biasing section 6 (first biasing means), and a second biasing section 7 (second biasing means). In Fig. 1 to Fig. 4, the direction of the rotation axis of the rotating camera 8 (axial direction of the rotation axis 8a) is defined as the Y axis, the direction perpendicular to the rotation axis 8a and in which the transducer 2 is offset from the rotation axis 8a is defined as the X axis, and the direction perpendicular to the X axis and Y axis is defined as the Z axis.

[0014] The rotating camera 8 is rotatable around a rotation axis 8a relative to the fixed member 4. The imaging device 1 is capable of rotating the orientation of the camera unit 9 approximately 360° around the Y axis by rotating the rotating camera 8 around the rotation axis 8a relative to the fixed member 4. In Fig. 1, the camera unit 9 faces in the +Z direction. The rotating camera 8 is an imaging unit that includes an imaging element and an imaging lens, both of which are not shown.

[0015] The vibrator 2 has a diaphragm 11 and a piezoelectric element 12. The rotating member 3 has a circular ring shape with a circular hole in the center, and the rotating camera 8 fits into this hole. This allows the rotating member 3 and the rotating camera 8 to rotate integrally around a rotation axis 8a. The rotating member 3 has a friction surface 3a. The friction surface 3a is the -Y side surface of the rotating member 3. The tip of the protrusion 11a of the diaphragm 11 forms a contact point 11c (Figure 1(b)) that comes into contact with the friction surface 3a. The rotating member 3 is made of a magnetic material, and is constructed from a material that is attracted by magnetic force.

[0016] On the +Y side of the rotating member 3, a guide mechanism 5 is provided between the fixed member 4 and the rotating member 3 as a rotation guide mechanism for guiding the relative rotation of the two. The guide mechanism 5 is composed of a fixed V groove portion 13 held by the fixed member 4, a movable V groove portion 15 held by the rotating member 3, and a plurality of balls 14 (rolling members) sandwiched between the fixed V groove portion 13 and the movable V groove portion 15. Both the movable V groove portion 15 and the fixed V groove portion 13 extend in a circumferential direction centered on the rotating shaft 8a. A plurality of balls 14 (for example, six balls) are arranged in a circumferential direction centered on the rotating shaft 8a. The plurality of balls 14 are kept at a constant circumferential interval by a retainer (not shown), and adjacent balls 14 roll while keeping a relative interval between them. The fixed member 4 rotatably holds the rotating member 3 via the guide mechanism 5.

[0017] The ball 14 is clamped between the fixed V groove portion 13 and the movable V groove portion 15 while being biased in the Y direction by the biasing forces of the first biasing portion 6 and the second biasing portion 7. This keeps the relative positions of the fixed V groove portion 13 and the movable V groove portion 15 in the Y direction and their relative positions in the radial direction around the rotation axis 8a constant. The ball 14 rolls between the fixed V groove portion 13 and the movable V groove portion 15, allowing the movable V groove portion 15 to rotate around the rotation axis 8a with respect to the fixed V groove portion 13.

[0018] The configuration and driving principle of the vibrator 2 will be described with reference to Fig. 2. Fig. 2(a) and (b) are diagrams showing the vibration mode of the vibrator 2. Fig. 2(c) is a diagram showing how the protrusion 11a vibrates elliptically.

[0019] The vibrator 2 is formed by bonding a piezoelectric element 12 and a vibration plate 11 together with an adhesive or the like. When a voltage is applied to the piezoelectric element 12, the piezoelectric element 12 expands and contracts, while the vibration plate 11 does not expand and contract. This causes bending deformation in the vibrator 2, in which the piezoelectric element 12 and the vibration plate 11 are bonded together. Then, by applying a high-frequency AC voltage to the piezoelectric element 12, ultrasonic vibrations are excited in the vibrator 2, and a high-frequency bending vibration mode can be generated.

[0020] The vibration mode of the vibrator 2 is a combination of the first and second vibration modes. As shown in FIG. 2(a), the first vibration mode is a vibration that generates a reciprocating motion M10 indicated by the arrow in the protrusion 11a of the vibrator 2, displacing the protrusion 11a mainly in the tangential direction of the friction surface 3a. In the first vibration, multiple nodes N1 are generated. In the vibrator 2, there are three nodes N1 indicated by dashed lines, and the nodes N1 at both ends of the longitudinal direction of the vibrator 2 are located near the protrusion 11a.

[0021] The second vibration mode, as shown in Fig. 2(b), generates a reciprocating motion M20 indicated by the arrow in the protrusion 11a, and displaces the protrusion 11a mainly in the direction of contacting and separating from the friction surface 3a. In the second vibration mode, multiple nodes N2 are generated. In the vibrator 2, there are two nodes N2 indicated by the dashed lines.

[0022] By generating the first vibration and the second vibration at the same frequency, an elliptical motion EM can be generated at the contact point 11c of the protrusion 11a. In the vibrator 2, a plurality of (two) protrusions 11a are provided to generate a larger driving force, but providing a plurality of protrusions is not essential. Note that the details of the method of generating the first vibration and the second vibration are publicly known, and therefore a detailed description thereof will be omitted here.

[0023] Returning to FIG. 1(a), the description of the configuration of the imaging device 1 will be continued. A first biasing portion 6 is disposed on the surface of the transducer 2 opposite to the contact point 11c. The first biasing portion 6 is formed of, for example, a compression spring. The -Y end of the first biasing portion 6 is fixed to the fixed member 4, and the +Y end presses the -Y surface of the transducer 2, thereby biasing the transducer 2 in the +Y direction. This biasing force presses the contact point 11c of the protrusion 11a of the transducer 2 against the friction surface 3a of the rotating member 3. Therefore, the first biasing portion 6 biases the rotating member 3 and the guide mechanism 5 in the +Y direction relative to the fixed member 4.

[0024] The second biasing portion 7 biases the magnetic portion of the rotating member 3 by magnetic force. The second biasing portion 7 is composed of a magnet, for example. The +Y direction end of the second biasing portion 7 is held by the fixed member 4, and the -Y direction end is arranged with a predetermined gap between it and the rotating member 3. This keeps the force with which the second biasing portion 7 magnetically attracts the rotating member 3 in the +Y direction constant. Note that it is not essential that the entire rotating member 3 is made of a magnetic material, and it is sufficient that at least the portion facing the second biasing portion 7 has magnetic properties.

[0025] The first urging section 6 and the second urging section 7 are disposed on opposite sides of the rotation axis 8a. The first urging section 6 and the second urging section 7 are disposed inside the guide mechanism 5 in the radial direction centered on the rotation axis 8a. As a result, as will be described later, even if the attitude of the imaging device 1 changes, it is possible to prevent an unfavorable rotation moment with the ball 14 as the fulcrum from acting. In addition, the second urging section 7 and the guide mechanism 5 are disposed in the direction of the rotation axis 8a (Y direction). Orthogonal toThat is, the second urging portion 7 and the guide mechanism 5 overlap when viewed from a predetermined direction (for example, the X direction) perpendicular to the Y direction. This prevents the second urging portion 7 and the guide mechanism 5 from being stacked in the Y direction and becoming large, thereby achieving a compact size in the Y direction.

[0026] Both the fixed V groove portion 13 and the movable V groove portion 15 have two slopes that form a V groove. As shown in FIG. 1(b), the line where the extensions of the two slopes of the fixed V groove portion 13 intersect is the valley line 13a. The line where the extensions of the two slopes of the movable V groove portion 15 intersect is the valley line 15a. The valley lines 13a and 15a overlap when viewed from the Y direction, and both are circular with the rotation axis 8a at their center. The multiple balls 14 are arranged at equal angles around the rotation axis 8a so that their centers coincide with the valley lines 13a and 15a. The number of balls 14 may be three or more.

[0027] The two contact points 11c of the vibrator 2 are aligned in the Z direction. The first biasing unit 6 biases the vibrator 2 in the +Y direction at a position between the two contact points 11c, so that the contact point 11c is pressed against the rotating member 3. The second biasing unit 7 is disposed on the +Y side of the rotating member 3. The second biasing unit 7 biases the rotating member 3 in the +Y direction by magnetic force.

[0028] The line connecting adjacent balls 14 is the ball connection line 14a. The first urging unit 6 and the second urging unit 7 are arranged inside the ball connection line 14a. This prevents the rotating camera 8 from falling over with any position on the ball connection line 14a of the balls 14 (or any of the balls 14) as a fulcrum due to the urging force of the first urging unit 6 or the second urging unit 7. Therefore, the wobble of the rotating member 3 is also reduced. In addition, by arranging the first urging unit 6, the vibrator 2, and the second urging unit 7 inside the guide mechanism 5, as described above, the rotating camera 8 is prevented from falling over due to the urging force of the first urging unit 6 or the second urging unit 7.

[0029] In the ultrasonic motor 16, the vibrator 2 is held by the fixed member 4, which is the fixed side, and the rotating member 3 is the movable side that rotates relative to the fixed member 4. Therefore, the first urging part 6 and the second urging part 7 do not move relative to the fixed member 4. Since the second urging part 7 is magnetic, it may become a source of magnetic noise for a magnetic sensor or an electric element. If the second urging part 7, which is magnetic, were to rotate as the ultrasonic motor 16 is driven, a wide range of magnetic noise countermeasures would be required. Therefore, in this embodiment, the second urging part 7, which is a magnetic source, is configured not to rotate relative to the fixed member 4, so that even if magnetic noise countermeasures are required, the countermeasure range can be limited, making it easy to implement the countermeasures.

[0030] Fig. 3 is a schematic cross-sectional view of the imaging device 1 arranged so that the -Y direction faces downward, as viewed from the +Z direction. Fig. 3(b) is a schematic cross-sectional view of the imaging device 1 arranged so that the -X direction faces downward, as viewed from the +Z direction. Using Figs. 3 and 4, it will be explained how the wobble of the rotating member 3 in the imaging device 1 is reduced.

[0031] 4(a) and (b) are longitudinal sectional views of an imaging device of a comparative example. The imaging device 101 of the comparative example differs from the imaging device 1 of the present embodiment in that it does not have the second biasing unit 7. That is, the ultrasonic motor 16 of the comparative example does not have the second biasing unit 7. The imaging device 101 shown in FIG. 4(a) is in a position where the -Y direction is slightly tilted with respect to the direction of gravity. The imaging device 101 shown in FIG. 4(b) is in a position where the -X direction is slightly tilted with respect to the direction of gravity.

[0032] In the state shown in Fig. 4(a), gravity F3 acts in the gravity direction on center of gravity 10 of rotation camera 8, including the weight of rotation member 3. Meanwhile, first biasing unit 6 biases friction surface 3a of rotation member 3 in the +Y direction with biasing force F1 at contact point 11c of transducer 2. Therefore, a clockwise rotation moment is applied to rotation member 3 and rotation camera 8 around the Z axis by biasing force F1, with ball 14 among multiple balls 14 that is closest to the +X side as the rotation fulcrum. Also, gravity F3 applies a counterclockwise rotation moment to rotation camera 8 around the Z axis, with ball 14 that is closest to the +X side as the rotation fulcrum.

[0033] Compared with gravity F3, the rotation moment due to biasing force F1 has a smaller rotation radius, so rotating camera 8 is more likely to rotate counterclockwise. When rotating camera 8 rotates counterclockwise, ball 14, which is closest to the -X side, moves away from fixed V groove portion 13 and movable V groove portion 15, creating gap D1.

[0034] As described above, the contact point 11c of the transducer 2 moves elliptically. If there is a gap D1 between the ball 14 and the fixed V-groove portion 13 and the movable V-groove portion 15, the rotating member 3 and the rotating camera 8 will wobble with the ball 14, which is located closest to the +X side, as the rotation fulcrum in conjunction with the elliptical motion of the contact point 11c. If the rotating member 3 wobbles, the friction state between the contact point 11c of the transducer 2 and the friction surface 3a of the rotating member 3 will become unstable, causing a problem that the characteristics of the ultrasonic motor 16 will become unstable.

[0035] In the state shown in Fig. 4(b), gravity F3 acts on center of gravity 10 in the gravity direction. Meanwhile, first biasing unit 6 biases friction surface 3a of rotating member 3 in the +Y direction with biasing force F1 at contact point 11c of transducer 2. Therefore, a clockwise rotational moment is applied to rotating member 3 and rotating camera 8 around the Z axis by biasing force F1, with ball 14 among multiple balls 14 that is closest to the +X side as the rotational fulcrum. Also, gravity F3 applies a counterclockwise rotational moment to rotating camera 8 around the Z axis, with ball 14 that is closest to the +X side as the rotational fulcrum.

[0036] Compared with gravity F3, the rotation moment due to biasing force F1 has a smaller rotation radius, so the rotation camera 8 is more likely to rotate counterclockwise. When the rotation camera 8 rotates counterclockwise, the ball 14 closest to the -X side moves away from the fixed V groove portion 13 and the movable V groove portion 15, creating a gap D2. This causes a problem similar to that shown in FIG. 4(a). Thus, the imaging device 101 of the comparative example had a problem in that the rotating member 3 wobbles in some positions, and the characteristics of the ultrasonic motor 16 are not stable.

[0037] In contrast, in the imaging device 1 of this embodiment, as shown in FIG. 3(a), gravity F3 acts in the gravity direction on the center of gravity 10 of the rotating camera 8, including the weight of the rotating member 3. Meanwhile, the first biasing unit 6 biases the friction surface 3a of the rotating member 3 in the +Y direction with a biasing force F1 at the contact point 11c of the transducer 2. The rotation moment acting due to gravity F3 and biasing force F1 is the same as in the comparative example. However, in this embodiment, the rotating member 3 is further biased in the +Y direction with a biasing force F2 due to the magnetic attraction force from the second biasing unit 7. The biasing force F2 applies a clockwise rotation moment around the Z axis with the ball 14 located closest to the +X side as the rotation fulcrum.

[0038] Since the direction of the rotation moment due to the biasing forces F1 and F2 is opposite to the direction of the rotation moment due to gravity F3, the rotation camera 8 becomes less likely to rotate around the Z axis compared to the comparative example (FIG. 4).

[0039] Moreover, the biasing forces F1 and F2 act on the inner side of the guide mechanism 5 in the radial direction centered on the rotation shaft 8a. The biasing forces F1 and F2 bias the rotating member 3 in the direction sandwiching the guide mechanism 5 with respect to the fixed member 4. The biasing forces F1 and F2 bias the rotating member 3 at positions on the opposite side with respect to the rotation shaft 8a. Therefore, the guide mechanism 5 is always subjected to a compressive force in the Y direction that is relatively uniform around the entire circumference.

[0040] In addition, the biasing force is prevented from concentrating on one side in the direction perpendicular to the rotation axis 8a. If the biasing parts were concentrated in the +X or -X direction, the non-biased side of the rotating member 3 would be likely to float relative to the fixed member 4 due to a change in the center of gravity 10 of the rotating camera 8 caused by a change in the attitude. From this perspective, by having the biasing forces F1 and F2 bias positions on opposite sides of the rotation axis 8a, the guide mechanism 5 can appropriately perform the guide function of the rotating member 3 even if the attitude of the imaging device 1 changes.

[0041] For these reasons, the rotating member 3 and the rotating camera 8 are unlikely to rotate with any of the balls 14 as the rotation fulcrum. This prevents gaps from being generated between any of the balls 14 and the fixed V-groove portion 13 and the movable V-groove portion 15. This prevents the rotating member 3 from wobbling. This stabilizes the friction state between the contact point 11c of the vibrator 2 and the friction surface 3a of the rotating member 3, and stabilizes the characteristics of the ultrasonic motor 16.

[0042] In particular, in the state shown in FIG. 3(a), the biasing forces F1 and F2 are applied in the +Y direction at a position sandwiching gravity F3 in the X direction, so that the characteristics of the ultrasonic motor 16 are very stable when the imaging device 1 is positioned so that the -Y direction faces downward.

[0043] 3(b), the direction of the rotation moment due to the biasing forces F1 and F2 with the ball 14 located closest to the +X side as the rotation fulcrum is opposite to the direction of the rotation moment due to gravity F3. This makes it more difficult for the rotating camera 8 to rotate around the Z axis compared to the comparative example (FIG. 4).

[0044] In addition, the positions and directions on which the biasing forces F1 and F2 act are the same as those described in Fig. 3(a). Therefore, the occurrence of wobbling of the rotating member 3 is suppressed, and the friction state between the contact point 11c of the vibrator 2 and the friction surface 3a of the rotating member 3 is stabilized, and the characteristics of the ultrasonic motor 16 can be stabilized.

[0045] According to this embodiment, the first biasing unit 6 presses the vibrator 2 against the friction surface 3a of the rotating member 3, thereby biasing the rotating member 3 and the guide mechanism 5 against the fixed member 4 in the direction of the rotation axis 8a. In addition, the second biasing unit 7 biases the rotating member 3 and the guide mechanism 5 against the fixed member 4 in the direction of the rotation axis 8a by magnetic force. This makes it possible to achieve stable driving characteristics with a simple configuration.

[0046] In particular, since the second biasing portion 7 is fixed to the fixed member 4 and magnetically attracts the magnetic portion of the rotating member 3, there is no need to use a bearing. Therefore, with a simple configuration and a small number of parts, wobble of the rotating member 3 can be reduced.

[0047] In addition, in the direction of the rotation axis 8a, the first biasing portion 6 is disposed on the friction surface 3a side (friction surface side), and the second biasing portion 7 is disposed on the opposite side of the friction surface 3a. In addition, the second biasing portion 7 and the guide mechanism 5 are arranged in the direction of the rotation axis 8a. Orthogonal to Therefore, it is possible to reduce the size in the direction of the rotation axis 8a.

[0048] Moreover, the first urging portion 6 and the second urging portion 7 are disposed inside the guide mechanism 5 in the radial direction centered on the rotating shaft 8a. Therefore, the first urging portion 6 and the second urging portion 7 urge the inner position of the guide mechanism 5 in the same direction. Moreover, the first urging portion 6 and the second urging portion 7 are disposed on opposite sides of the rotating shaft 8a. This makes it possible to prevent the rotating member 3 from falling with any position of the guide mechanism 5 or any ball 14 as a fulcrum. Since the wobble of the rotating member 3 can be reduced, stable motor characteristics can be obtained with a simple configuration.

[0049] Furthermore, since the second biasing portion 7, which is a magnetic source, does not rotate relative to the fixed member 4, countermeasures against magnetic noise are easily implemented.

[0050] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to Fig. 5 and Fig. 6. Fig. 5(a) is a schematic longitudinal sectional view of an imaging device to which an ultrasonic motor of this embodiment is applied. Fig. 5(b) is a sectional view taken along line BB in Fig. 5(a). In Fig. 5 and Fig. 6, the same reference numerals are used for the same components as those in the first embodiment.

[0051] The ultrasonic motor 16 of this embodiment has a fixed member 4, a vibrator 2, a rotating member 3, a first biasing portion 6, a second biasing portion 7, a first guide mechanism 21, and a second guide mechanism 5. The rotating member 3 and the rotating camera 8 rotate integrally around a rotation axis 8a.

[0052] The fixing member 4 has a second curved surface portion 4b and a second flat surface portion 4a. The second curved surface portion 4b is a circumferential surface centered on the rotation axis 8a. The second flat surface portion 4a is a surface that is parallel to the XY direction and faces the +Y direction.

[0053] The rotating member 3 has a friction surface 3a, a magnetic portion 3b, a first flat portion 3c, and a first curved portion 3d. The first curved portion 3d faces the second curved portion 4b. The first flat portion 3c faces the second flat portion 4a. The friction surface 3a is provided on the +Y side surface of the first flat portion 3c. The rotating member 3 is a magnetic body. At least a part of the rotating member 3 may be configured to have magnetism, and the magnetic portion 3b, which is the portion facing the second biasing portion 7, is a magnetic portion.

[0054] The first guide mechanism 21 is disposed between the rotating member 3 and the fixed member 4 in the radial direction centered on the rotating shaft 8a. The second guide mechanism 5 is disposed between the rotating member 3 and the fixed member 4 in the direction of the rotating shaft 8a.

[0055] The second guide mechanism 5 is arranged in a different position from the guide mechanism 5 described in the first embodiment, but has a similar configuration. The second fixed V groove portion 13 of the second guide mechanism 5 is held by the second flat surface portion 4a of the fixed member 4. The second movable V groove portion 15 of the second guide mechanism 5 is held by the first flat surface portion 3c of the rotating member 3. A plurality of balls 14 are sandwiched between the second fixed V groove portion 13 and the second movable V groove portion 15.

[0056] The first fixed V groove portion 18 of the first guide mechanism 21 is held by the second curved surface portion 4b of the fixed member 4. The first movable V groove portion 20 of the first guide mechanism 21 is held by the first curved surface portion 3d of the rotating member 3. A plurality of balls 19 are sandwiched between the first fixed V groove portion 18 and the first movable V groove portion 20.

[0057] The multiple balls 19 are kept at constant circumferential intervals by a retainer (not shown), and adjacent balls 19 roll while maintaining a relative interval between them. This keeps the relative positions of the first fixed V-groove portion 18 and the first movable V-groove portion 20 constant in the X direction with respect to the rotation shaft 8a. The fixed member 4 rotatably holds the rotating member 3 via the first guide mechanism 21 and the second guide mechanism 5.

[0058] As shown in FIG. 5(b), the line where the extensions of the two slopes of the first movable V groove portion 20 intersect is the valley line 20a. The line where the extensions of the two slopes of the first fixed V groove portion 18 intersect is the valley line 18a. The valley lines 20a and 18a are both circular with the rotation axis 8a at their center. The center position of the ball 19 is between the valley lines 18a and 20a. The multiple balls 19 are arranged so as to be aligned at equal angles around the rotation axis 8a. The number of balls 19 may be three or more.

[0059] In this embodiment as well, the first urging portion 6 and the second urging portion 7 are disposed on opposite sides of the rotation shaft 8a. The first urging portion 6 and the second urging portion 7 have the same configuration as those in the first embodiment, but their positions are different. The first urging portion 6 is disposed between the first flat surface portion 3c and the fixed member 4 on the +Y side of the first flat surface portion 3c of the rotating member 3.

[0060] The +Y end of the first biasing portion 6 is fixed to the fixed member 4, and the -Y end presses the +Y surface of the vibrator 2, thereby biasing the vibrator 2 in the -Y direction. This biasing force presses the contact point 11c of the vibrator 2 against the friction surface 3a of the rotating member 3. Therefore, the first biasing portion 6 biases the rotating member 3 and the second movable V-groove portion 15 in the -Y direction, that is, against the second flat surface portion 4a of the fixed member 4. The ball 14 is sandwiched between the second fixed V-groove portion 13 and the second movable V-groove portion 15 in a state where it is biased in the Y direction by the biasing force from the first biasing portion 6.

[0061] The second biasing part 7 biases the rotating member 3 in the +X direction by magnetic force. First, the second biasing part 7 is disposed between the magnetic part 3b of the rotating member 3 and the second curved surface part 4b of the fixed member 4 in the X direction. The second biasing part 7 magnetically attracts the magnetic part (magnetic part 3b) of the rotating member 3. The +X side end of the second biasing part 7 is held by the fixed member 4, and the -X side end of the second biasing part 7 is disposed with a predetermined gap from the rotating member 3. This keeps the force of magnetic attraction of the second biasing part 7 to the rotating member 3 constant. The ball 19 is sandwiched between the first fixed V groove part 18 and the first movable V groove part 20 by the second biasing part 7 while being biased in the X direction.

[0062] The action of the urging forces exerted by the first urging portion 6 and the second urging portion 7 will be described with reference to Fig. 6(a). Fig. 6(a) is a schematic vertical cross-sectional view of the imaging device 1 according to the present embodiment.

[0063] The force applied by the first biasing unit 6 to bias the rotating member 3 in the -Y direction relative to the fixed member 4 is defined as biasing force F1. The force applied by the second biasing unit 7 to bias the rotating member 3 in the +X direction relative to the fixed member 4 is defined as biasing force F2. The central positions of the balls 14, 19 in the direction of the rotation axis 8a are defined as central positions 14a, 19a, respectively. The region from central position 14a to central position 19a in the direction of the rotation axis 8a is defined as region D3.

[0064] The second urging portion 7 is disposed at a position in the +Y direction from the first guide mechanism 21 and at a position in the -Y direction from the second guide mechanism 5. That is, the second urging portion 7 is disposed between the first guide mechanism 21 and the second guide mechanism 5 in the direction of the rotation axis 8a. Strictly speaking, the +X direction end of the second urging portion 7 is held by the second curved surface portion 4b of the fixed member 4 within the range of the region D3 in the direction of the rotation axis 8a. Thereby, the second urging portion 7 assists the first urging portion 6 in urging the rotating member 3. This will be described below.

[0065] 6(a) shows a state in which ball 19 of first guide mechanism 21 is closest to second biasing portion 7 in the circumferential direction. Rotating member 3 is biased in the +X direction relative to fixed member 4 via first guide mechanism 21 by biasing force F2 (magnetic force) of second biasing portion 7. A clockwise rotational moment M1 is applied to rotating member 3 around the Z axis by biasing force F2, with closest ball 19 serving as the rotation fulcrum.

[0066] The direction of the force acting on the rotating member 3 in the direction of the rotation axis 8a near the transducer 2 due to the rotation moment M1 is the -Y direction. This direction is the same as the direction of the biasing force F1 generated by the first biasing unit 6. Therefore, by matching the biasing direction of the rotation moment M1 with the direction of the biasing force F1, the biasing force F2 of the second biasing unit 7 acts in a direction that assists the biasing force F1 of the first biasing unit 6. This makes it possible to bias the rotating member 3 against the fixed member 4 with a stronger force. Therefore, the transducer 2 can be in stable contact with the rotating member 3, and the first guide mechanism 21 and the second guide mechanism 5 can appropriately perform the guide function of the rotating member 3 even if the attitude of the imaging device 1 changes.

[0067] Fig. 6(b) is a diagram showing a comparative example to the configuration of Fig. 6(a). In this comparative example, the guide function is inferior to that of the configuration of Fig. 6(a). However, if this is acceptable, this comparative example may be adopted.

[0068] In the comparative example (FIG. 6(b)), the second urging portion 7 is disposed at a position in the -Y direction relative to the second guide mechanism 5 and the first guide mechanism 21. The +X direction end of the second urging portion 7 is held by the second curved surface portion 4b of the fixed member 4 at a position outside the range of the region D3 in the direction of the rotation axis 8a and on the -Y side of the region D3.

[0069] Therefore, the rotating member 3 is subjected to a counterclockwise rotation moment M2 around the Z axis with the closest ball 19 as the rotation fulcrum by the biasing force F2. The direction of the force in the direction of the rotation axis 8a applied to the rotating member 3 near the vibrator 2 by the rotation moment M2 is the +Y direction. This direction is opposite to the direction of the biasing force F1 generated by the first biasing unit 6. Therefore, the rotation moment M2 applies a force in a direction that separates the rotating member 3 and the fixed member 4. In other words, the rotation moment M2 acts as a reaction force against the biasing force F1. Therefore, the rotating member 3 is not biased against the fixed member 4 with the desired force, and the characteristics of the ultrasonic motor 16 may be affected. Therefore, it is advantageous to adopt the configuration shown in FIG. 6(a) instead of the comparative example in terms of stabilizing the drive characteristics of the ultrasonic motor 16.

[0070] According to the present embodiment, the second biasing portion 7 biases the rotating member 3 and the first guide mechanism 21 toward the fixed member 4 in the radial direction centered on the rotating shaft 8a. The first biasing portion 6 biases the rotating member 3 and the second guide mechanism 21 toward the fixed member 4 in the direction of the rotating shaft 8a. As a result, it is possible to achieve the same effect as the first embodiment in terms of exhibiting stable drive characteristics with a simple configuration.

[0071] Furthermore, since the second biasing unit 7 is disposed between the first guide mechanism 5 and the second guide mechanism 21 in the direction of the rotation axis 8a, it can assist the biasing of the rotating member 3 by the first biasing unit 6. This allows the rotation of the rotating member 3 to be stably guided by the first guide mechanism 21 and the second guide mechanism 5. Furthermore, the vibrator 2 can stably drive the friction surface 3a.

[0072] Furthermore, the second biasing portion 7 is fixed to the fixed member 4 and magnetically attracts the magnetic portion 3b of the rotating member 3, so that the rotation of the rotating member 3 can be stabilized with a simple configuration having a small number of parts.

[0073] (Third embodiment) Next, a third embodiment of the present invention will be described with reference to Fig. 7 and Fig. 8. Fig. 7(a) is a schematic longitudinal sectional view of an imaging device to which an ultrasonic motor of this embodiment is applied. Fig. 7(b) is a sectional view taken along line CC in Fig. 7(a). In Fig. 7 and Fig. 8, the same reference numerals are used for components similar to those of the second embodiment.

[0074] In this embodiment, a configuration is adopted in which the positions at which the first urging portion 6 and the second urging portion 7 urge the rotating member 3 are reversed from those in the second embodiment.

[0075] The configuration of the second curved surface portion 4b and the second flat surface portion 4a of the fixed member 4 is the same as that of the second embodiment. The rotating member 3 has a friction surface 3a, a magnetic portion 3b, a first flat surface portion 3c, and a first curved surface portion 3d. The first curved surface portion 3d faces the second curved surface portion 4b. The first flat surface portion 3c faces the second flat surface portion 4a. The friction surface 3a is provided on the first curved surface portion 3d. The rotating member 3 is a magnetic body. At least a part of the rotating member 3 may be configured to have magnetism, and the magnetic portion 3b, which is the portion facing the second biasing portion 7, is a portion having magnetism. The configuration and arrangement of the first guide mechanism 21 and the second guide mechanism 5 are the same as those of the second embodiment.

[0076] In this embodiment, the first biasing portion 6 and the second biasing portion 7 are also disposed on opposite sides of the rotation shaft 8a. The first biasing portion 6 is disposed between the friction surface 3a of the rotating member 3 and the fixed member 4 in the X direction. The -X direction end of the first biasing portion 6 is fixed to the fixed member 4, and the +X direction end presses the -X direction surface of the vibrator 2, so that the first biasing portion 6 biases the vibrator 2 in the +X direction. By this biasing force, the first biasing portion 6 presses the contact point 11c of the vibrator 2 against the friction surface 3a of the rotating member 3, and biases the rotating member 3 and the first guide mechanism 21 in the +X direction relative to the fixed member 4. The ball 19 of the first guide mechanism 21 is sandwiched by the first biasing portion 6 between the first fixed V groove portion 18 and the first movable V groove portion 20 in a state in which it is biased in the X direction.

[0077] The second biasing portion 7 biases the rotating member 3 in the -Y direction by magnetic force. The -Y direction end of the second biasing portion 7 is held by the second flat surface portion 4a of the fixed member 4, and the +Y direction end is disposed with a predetermined gap maintained between it and the rotating member 3. This keeps the force with which the second biasing portion 7 magnetically attracts the rotating member 3 constant. The ball 14 of the second guide mechanism 5 is sandwiched between the second fixed V-groove portion 13 and the second movable V-groove portion 15 by the biasing force from the second biasing portion 7 while being biased in the Y direction.

[0078] The action of the biasing forces by the first biasing portion 6 and the second biasing portion 7 will be described with reference to Fig. 8. Fig. 8 is a schematic vertical cross-sectional view of the imaging device 1 in this embodiment. The force with which the first biasing portion 6 biases the rotating member 3 in the +X direction relative to the fixed member 4 is defined as biasing force F1. The force with which the second biasing portion 7 biases the rotating member 3 in the -Y direction relative to the fixed member 4 is defined as biasing force F2. The region between center positions 14a, 19a of the balls 14, 19 in the direction of the rotation axis 8a is defined as region D3.

[0079] The first urging portion 6 is disposed at a position in the +Y direction from the first guide mechanism 21 and at a position in the -Y direction from the second guide mechanism 5. That is, the first urging portion 6 is disposed between the first guide mechanism 21 and the second guide mechanism 5 in the direction of the rotation axis 8a. Strictly speaking, the -X direction end of the first urging portion 6 is held by the fixed member 4 within the range of the region D3 in the direction of the rotation axis 8a. As a result, the first urging portion 6 assists the urging of the rotating member 3 by the second urging portion 7. That is, the positions of the first urging portion 6 and the second urging portion 7 are reversed from those in the second embodiment, but the action regarding the assist of the urging is the same as that described in the second embodiment. That is, with respect to the force applied to the rotating member 3 near the transducer 2 in the direction of the rotation axis 8a, the urging direction of the force by the rotation moment M1 and the urging direction by the urging force F2 coincide with each other. As a result, the biasing force F1 by the first biasing portion 6 acts in a direction assisting the biasing force F2 by the second biasing portion 7. This makes it possible to bias the rotating member 3 against the fixed member 4 with a stronger force.

[0080] According to the present embodiment, the first biasing portion 6 biases the rotating member 3 and the first guide mechanism 21 toward the fixed member 4 in the radial direction centered on the rotating shaft 8a. The second biasing portion 7 biases the rotating member 3 and the second guide mechanism 21 toward the fixed member 4 in the direction of the rotating shaft 8a. As a result, it is possible to achieve the same effect as the second embodiment in terms of exhibiting stable drive characteristics with a simple configuration.

[0081] Furthermore, since the first biasing unit 6 is disposed between the first guide mechanism 5 and the second guide mechanism 21 in the direction of the rotation axis 8a, it can assist the biasing of the rotating member 3 by the second biasing unit 7. This allows the rotation of the rotating member 3 to be stably guided by the first guide mechanism 21 and the second guide mechanism 5. Furthermore, the vibrator 2 can stably drive the friction surface 3a.

[0082] Furthermore, the second biasing portion 7 is fixed to the fixed member 4 and magnetically attracts the magnetic portion 3b of the rotating member 3, so that the rotation of the rotating member 3 can be stabilized with a simple configuration having a small number of parts.

[0083] In addition, in a configuration (not shown) in which the positional relationship between the first biasing portion 6 and the first guide mechanism 21 is reversed in the direction of the rotation axis 8a (a configuration corresponding to the comparative example (FIG. 6(b)) in the second embodiment), the guide function is inferior to the configuration in FIG. 7(a). However, if the inferior guide function is acceptable, the above-mentioned configuration (not shown) may be adopted.

[0084] The second and third embodiments can be expressed as follows. One of the first biasing portion 6 and the second biasing portion 7 biases the rotating member 3 and the first guide mechanism 21 toward the fixed member 4 in the radial direction about the rotation axis 8a. The other of the first biasing portion 6 and the second biasing portion 7 biases the rotating member 3 and the second guide mechanism 5 toward the fixed member 4 in the direction of the rotation axis 8a.

[0085] Next, modifications of the second and third embodiments will be described with reference to Fig. 9(a) and (b). Fig. 9(a) is a schematic vertical cross-sectional view of an imaging device 1 to which an ultrasonic motor according to a modification (first modification) of the second embodiment is applied.

[0086] The first modified example (FIG. 9(a)) differs from the configuration shown in FIG. 5(a) in that a yoke 22 is provided on the fixed member 4. The yoke 22 is arranged so as to contact the +X direction end of the second urging portion 7. The yoke 22 is held on the fixed member 4 integrally with the second urging portion 7. The yoke 22 is magnetically attracted to the second urging portion 7, i.e., magnetically coupled to the second urging portion 7. The yoke 22 has an opposing surface 22a facing the +Y direction. The opposing surface 22a is arranged with a predetermined gap maintained relative to the first flat surface portion 3c of the rotating member 3, and faces the first flat surface portion 3c.

[0087] The opposing surface 22a of the yoke 22 is magnetized by the second biasing portion 7. Therefore, a magnetic path P is formed through the magnetic portion 3b of the rotating member 3, the second biasing portion 7, and the yoke 22. Here, the magnetic path in the yoke 22 is referred to as magnetic path P1, and the magnetic path in the magnetic portion 3b is referred to as magnetic path P2.

[0088] Since the opposing surface 22a is magnetized, a biasing force F4 is generated, which biases the first flat surface portion 3c of the rotating member 3 in the -Y direction relative to the fixed member 4. Therefore, in addition to the biasing force F1 in the -Y direction by the first biasing portion 6 and the biasing force F2 in the +X direction by the second biasing portion 7, the biasing force F4 acts on the rotating member 3. The biasing force F4 biases the rotating member 3 and the second guide mechanism 5 toward the fixed member 4. The direction of the biasing force F4 is the same as the direction of the biasing force F1 in the direction of the rotation axis 8a (-Y direction). Therefore, the resultant force of the biasing forces F1 and F4 strongly biases the rotating member 3 and the second guide mechanism 5 toward the fixed member 4. Therefore, the biasing force F4 assists the biasing force F1 by the first biasing portion 6.

[0089] In this way, a magnetic path P is formed via the yoke 22 so that the biasing direction by the second biasing portion 7 is the same as the biasing direction by the first biasing portion 6. Therefore, it is possible to cause the biasing force F4 by the second biasing portion 7 to act in a direction that assists the biasing force F1 by the first biasing portion 6. This allows the first guide mechanism 21 and the second guide mechanism 5 to guide the rotation of the rotating member 3 more stably. Also, the vibrator 2 can drive the friction surface 3a more stably.

[0090] FIG. 9(b) is a schematic vertical sectional view of an imaging device to which an ultrasonic motor according to a modified example (second modified example) of the third embodiment is applied.

[0091] The second modified example (FIG. 9(b)) differs from the configuration shown in FIG. 7(a) in that a yoke 22 is provided on the fixed member 4. The yoke 22 is arranged so as to contact the -Y direction end of the second urging portion 7. The yoke 22 is magnetically attracted to the second urging portion 7, and is held on the fixed member 4 together with the second urging portion 7. The yoke 22 has an opposing surface 22a facing the +X direction. The opposing surface 22a is arranged with a predetermined gap maintained relative to the first curved surface portion 3d of the rotating member 3, and faces the first curved surface portion 3d.

[0092] The opposing surface 22a of the yoke 22 is magnetized by the second biasing portion 7. Therefore, a magnetic path P is formed through the magnetic portion 3b of the rotating member 3, the second biasing portion 7, and the yoke 22. Here, the magnetic path in the yoke 22 is referred to as magnetic path P1, and the magnetic path in the magnetic portion 3b is referred to as magnetic path P2.

[0093] Since the opposing surface 22a is magnetized, a biasing force F5 is generated, which biases the rotating member 3 in the +X direction relative to the fixed member 4. Therefore, in addition to the biasing force F1 in the +X direction by the first biasing unit 6 and the biasing force F2 in the -Y direction by the second biasing unit 7, the biasing force F5 acts on the rotating member 3. The biasing force F5 biases the rotating member 3 and the second guide mechanism 5 toward the fixed member 4. The direction of the biasing force F5 is the same as the direction of the biasing force F1 by the first biasing unit 6 (+X direction). Therefore, the combined force of the biasing forces F1 and F5 biases the rotating member 3 and the first guide mechanism 21 toward the fixed member 4. Therefore, the biasing force F5 assists the biasing force F1 by the first biasing unit 6.

[0094] In this way, a magnetic path P is formed via the yoke 22 so that the biasing direction by the second biasing portion 7 is the same as the biasing direction by the first biasing portion 6. Therefore, it is possible to cause the biasing force F5 by the second biasing portion 7 to act in a direction that assists the biasing force F1 by the first biasing portion 6. This allows the first guide mechanism 21 and the second guide mechanism 5 to guide the rotation of the rotating member 3 more stably. Also, the vibrator 2 can drive the friction surface 3a more stably.

[0095] In the first and second modified examples, the magnetic flux of the second urging portion 7 is confined by the yoke 22 and the magnetic portion 3b in consideration of the possibility that the magnetic force of the second urging portion 7 may become a source of magnetic noise for a magnetic sensor or an electric element. However, the configuration is not limited to confining the magnetic flux by the rotating member 3 and the fixed member 4. In addition, the magnetic flux does not necessarily have to be confined.

[0096] Next, another modified example of the third embodiment will be described with reference to Fig. 10 and Fig. 11. Fig. 10 is a schematic vertical cross-sectional view of an imaging device to which an ultrasonic motor according to a modified example (third modified example) of the third embodiment is applied. The third modified example differs from the configuration shown in Fig. 7(a) in that a third biasing section 23 (third biasing means) is added.

[0097] The effect of providing the third biasing portion 23 will be described by comparing Fig. 10 with Figs. 11(a) and (b). Figs. 11(a) and (b) are schematic vertical cross-sectional views of the main parts of the imaging device 1 not provided with the third biasing portion 23, that is, the imaging device 1 in the third embodiment. Note that Figs. 10, 11(a) and (b) omit illustration of the second biasing portion 7, valley lines 13a, 15a, 18a, ball 14, etc. The movable locus 31 of the ball 19 is indicated by a dotted line.

[0098] As shown in FIG. 10, the third urging part 23 is composed of a magnet or the like, similar to the second urging part 7. The third urging part 23 attracts and urges the magnetic part of the rotating member 3 by magnetic force. The third urging part 23 is disposed between the first urging part 6 and the second urging part 7 in the circumferential direction centered on the rotating shaft 8a. The +Z direction end of the third urging part 23 is held by the fixed member 4, and the -Z direction end is disposed with a predetermined gap from the rotating member 3. This keeps the force of the third urging part 23 magnetically attracting the rotating member 3 constant. The force acting on the rotating member 3 by the third urging part 23 is defined as urging force F6. This urging force F6 acts in the +Z direction.

[0099] 11(a) and (b) show a phenomenon that may occur in the ultrasonic motor 16 in the third embodiment. As shown in FIG. 11(a), among the multiple balls 19, the angular range formed by balls 19a and 19b adjacent to each other with respect to the rotation shaft 8a as the center is defined as angular range E. As described above, the balls 19 are kept at constant intervals in the circumferential direction by a retainer (not shown), and roll while maintaining relative intervals with each other. The relative position of each ball 19 with respect to the first biasing portion 6 in the circumferential direction changes due to the rolling. FIG. 11(a) shows a state in which the first biasing portion 6 is located in angular range E.

[0100] The first biasing portion 6 biases the rotating member 3 in the +X direction relative to the fixed member 4. It is preferable that all of the balls 19 are always sandwiched between the first movable V groove portion 20 and the first fixed V groove portion 18. However, due to manufacturing variations and tolerances, the first movable V groove portion 20 and the first fixed V groove portion 18 may not contact some of the balls 19 over the entire circumference of the annular shape. For example, a gap G is generated between the first movable V groove portion 20 and the ball 19, or between the first fixed V groove portion 18 and the ball 19.

[0101] 11(a), the biasing force F1 by the first biasing portion 6 is transmitted from the rotating member 3 to the fixed member 4 via the balls 19a and 19b as component forces F19a and F19b, respectively. Therefore, the first movable V-groove portion 20 and the balls 19a and 19b, and the first fixed V-groove portion 18 and the balls 19a and 19b are in contact with each other.

[0102] The distance between the balls 19a, 19b in the circumferential direction about the rotation shaft 8a is constant. Therefore, the balls 19a, 19b come into contact with both the first movable V-groove portion 20 and the first fixed V-groove portion 18, thereby determining their radial positions about the rotation shaft 8a and their positions on the XZ plane. In other words, when the first biasing portion 6 is within the angle range E, the position of the rotation member 3 is determined by the two balls 19a, 19b with respect to the fixed member 4, and the rotation member 3 is biased without any backlash.

[0103] 11(b) shows a state in which one ball 19c of the multiple balls 19 is aligned in the X-axis direction with the first biasing portion 6. Due to the above-mentioned manufacturing variations and tolerances, a gap G may occur between the first movable V-groove portion 20 and the ball 19, or between the first fixed V-groove portion 18 and the ball 19.

[0104] In the state shown in FIG. 11(b), the biasing force F1 by the first biasing portion 6 is transmitted from the rotating member 3 to the fixed member 4 via the ball 19c. The force transmitted to the fixed member 4 through the ball 19c is called the biasing force F19c. In this state, the first movable V-groove portion 20 and the ball 19c, and the first fixed V-groove portion 18 and the ball 19c are in contact with each other. Since the rotating member 3 is biased to the fixed member 4 via only one ball 19c, the rotating member 3 can rotate slightly on the XY plane with the ball 19c as the rotation fulcrum. Therefore, a backlash corresponding to the gap G occurs in the rotation direction indicated by the arrow S. In other words, if the first biasing portion 6 is aligned with one ball 19c in the X-axis direction, the position of the rotating member 3 relative to the fixed member 4 is not determined, and a backlash corresponding to the gap G occurs.

[0105] As will be described next, according to the third modified example (FIG. 10), even in the state shown in FIG. 11(b), rattling of the rotating member 3 relative to the fixed member 4 can be suppressed.

[0106] 10, like Fig. 11(b), shows a state in which the ball 19c is aligned with the first biasing portion 6 in the X-axis direction. The first biasing portion 6 and the third biasing portion 23 bias the rotating member 3 against the fixed member 4. The direction of the rotational moment around the ball 19c due to the biasing force F6 is the same as one of the rotational directions indicated by the arrow S (counterclockwise direction).

[0107] 10, the biasing force F1 biases the rotating member 3 in the +X direction, and the biasing force F6 biases the rotating member 3 in the +Z direction. By biasing the rotating member 3 in the +Z direction, the biasing force F6 is transmitted to the fixed member 4 as a biasing force F19d via the ball 19d, and the ball 19d is sandwiched between the first movable V-groove portion 20 and the first fixed V-groove portion 18.

[0108] The biasing forces F1 and F6 are transmitted to the fixed member 4 as biasing forces F19c and F19d via the balls 19c and 19d, respectively. Therefore, the balls 19c and 19d come into contact with both the first movable V-groove portion 20 and the first fixed V-groove portion 18, thereby determining the radial position about the rotation axis 8a and determining the position on the XZ plane. Therefore, the position of the rotating member 3 is determined by the two balls 19c and 19d with respect to the fixed member 4, and the rotating member 3 is biased without any backlash.

[0109] In this way, the third urging portion 23 urges the rotating member 3 and the first guide mechanism 21 against the fixed member 4 in the radial direction centered on the rotating shaft 8a by magnetic force. The third urging portion 23 is disposed between the first urging portion 6 and the second urging portion 7 in the circumferential direction centered on the rotating shaft 8a. This suppresses wobbling of the rotating member 3 against the fixed member 4 regardless of the position of the ball 19 in the circumferential direction when the rotating member 3 rotates. Therefore, the ultrasonic motor 16 can exhibit even more stable driving characteristics.

[0110] The third modified example (FIG. 10) can also be applied to the second embodiment. That is, a third biasing portion 23 may be added to the configuration shown in FIG. 5(a). The third modified example can also be applied to the configuration shown in FIG. 9(a) and (b).

[0111] Although the present invention has been described in detail based on the preferred embodiments, the present invention is not limited to these specific embodiments, and various forms within the scope of the gist of the present invention are also included in the present invention. Parts of the above-described embodiments may be combined as appropriate.

[0112] In each of the above embodiments, the second biasing portion 7 is configured to magnetically attract the magnetic portion of the rotating member 3, but it may also be configured to repel the magnetic portion, as shown in FIG. 12.

[0113] 12(a), (b), and (c) are schematic partial enlarged views showing modified examples of the ultrasonic motor 16 in which the configuration of the second biasing portion is different from that in the first, second, and third embodiments, respectively.

[0114] As shown in FIG. 12(a), in the configuration shown in the first embodiment (FIG. 1(a)), a second urging portion 70 is provided instead of the second urging portion 7. The second urging portion 70 is disposed between the rotating member 3 and the fixed member 4 on the -Y side of the rotating member 3. The second urging portion 70 has magnets 71 and 72 that face each other. The magnet 71 is fixed to the surface on the -Y side of the rotating member 3, and the magnet 72 is fixed to the surface on the +Y side of the fixed member 4. The magnets 71 and 72 have the same magnetic poles (for example, N poles and N poles) facing each other, and generate a repulsive force as a magnetic force. As a result, the rotating member 3 is urged in the +Y direction.

[0115] As shown in FIG. 12(b), in the configuration shown in the second embodiment (FIG. 5(a)), a second urging portion 70 is provided instead of the second urging portion 7. The second urging portion 70 is disposed between the rotating member 3 and the fixed member 4 on the -X side of the rotating member 3. The magnet 71 is fixed to the -X side surface of the outer circumferential surface of the first curved portion 3d of the rotating member 3, and the magnet 72 is fixed to the +X side surface of the inner circumferential surface of the fixed member 4. The repulsive force between the magnet 71 and the magnet 72 urges the rotating member 3 in the +X direction.

[0116] As shown in FIG. 12(c), in the configuration shown in the second embodiment (FIG. 7(a)), a second biasing portion 70 is provided instead of the second biasing portion 7. The second biasing portion 70 is disposed between the rotating member 3 and the fixed member 4 on the +Y side of the rotating member 3. The magnet 71 is fixed to the +Y side surface of the rotating member 3, and the magnet 72 is fixed to the -Y side surface of the fixed member 4. The repulsive force between the magnets 71 and 72 biases the rotating member 3 in the -Y direction.

[0117] The driving device having a movable part (rotating member 3, etc.) that can be moved by the ultrasonic motor 16 of the present invention is not limited to an imaging device. For example, it may be a lens device that converts the rotational motion generated by the ultrasonic motor 16 into linear motion by a well-known conversion mechanism to move a lens in the optical axis direction, or a robot arm that moves an arm part by the ultrasonic motor 16. [Explanation of symbols]

[0118] 2 Transducers 4 Fixing member 3 Rotating parts 5 Guide mechanism 6 First biasing portion 7, 70 Second biasing portion 8a Rotation axis

Claims

1. A transducer in which ultrasonic vibrations are excited; a rotating member having a friction surface and at least a portion thereof being magnetic, the rotating member rotating about a rotation axis as the friction surface is driven by the oscillator; A fixed member that rotatably holds the rotating member; a guide mechanism disposed between the fixed member and the rotating member in the rotation axis direction and configured to guide rotation of the rotating member relative to the fixed member; a first biasing means for biasing the rotary member and the guide mechanism against the fixed member in the direction of the rotation axis by pressing the vibrator against the friction surface of the rotary member; and second biasing means for biasing the rotating member and the guide mechanism against the fixed member in the direction of the rotation axis by a magnetic force.

2. the first biasing means is disposed on the friction surface side of the rotating member in the rotation axis direction, 2. The ultrasonic motor according to claim 1, wherein the second biasing means is disposed on a side of the rotating member opposite to the friction surface in the direction of the rotation axis.

3. 3. The ultrasonic motor according to claim 2, wherein the second biasing means is fixed to the fixed member and biases the rotating member and the guide mechanism against the fixed member by magnetically attracting a magnetic portion of the rotating member.

4. 4. The ultrasonic motor according to claim 1, wherein the first biasing means and the second biasing means are disposed inside the guide mechanism in a radial direction about the rotation axis.

5. 5. The ultrasonic motor according to claim 1, wherein the second biasing means and the guide mechanism are arranged to overlap each other in a direction perpendicular to the direction of the rotation axis.

6. 6. The ultrasonic motor according to claim 1, wherein the first biasing means and the second biasing means do not rotate relative to the fixed member.

7. 7. The ultrasonic motor according to claim 1, wherein the first biasing means and the second biasing means are arranged on opposite sides of the rotation shaft.

8. 8. The ultrasonic motor according to claim 1, wherein the guide mechanism is composed of a V-groove portion fixed to the fixed member, a V-groove portion fixed to the rotating member, and a rolling member sandwiched between the V-groove portion fixed to the fixed member and the V-groove portion fixed to the rotating member.

9. A transducer in which ultrasonic vibrations are excited; a rotating member having a friction surface and at least a portion thereof being magnetic, the rotating member rotating about a rotation axis as the friction surface is driven by the oscillator; A fixed member that rotatably holds the rotating member; a first guide mechanism disposed between the fixed member and the rotating member in a radial direction about the rotation axis, the first guide mechanism guiding rotation of the rotating member relative to the fixed member; a second guide mechanism disposed between the fixed member and the rotating member in the rotation axis direction and configured to guide rotation of the rotating member relative to the fixed member; a first biasing means for pressing the vibrator against the friction surface of the rotating member; and a second biasing means for generating a biasing force by a magnetic force, an ultrasonic motor comprising: a first biasing means for biasing the rotating member and the first guide mechanism against the fixed member in a radial direction centered on the rotation axis; and a second biasing means for biasing the rotating member and the second guide mechanism against the fixed member in a direction of the rotation axis.

10. 10. The ultrasonic motor according to claim 9, wherein the one of the biasing means is disposed between the first guide mechanism and the second guide mechanism in the rotation axis direction.

11. 11. The ultrasonic motor according to claim 9, wherein the first biasing means and the second biasing means are arranged on opposite sides of the rotation shaft.

12. 12. The ultrasonic motor according to claim 9, wherein the second biasing means is fixed to the fixed member and magnetically attracts a magnetic portion of the rotating member.

13. a yoke magnetically coupled to the second biasing means; 13. The ultrasonic motor according to claim 9, wherein the yoke has an opposing surface that faces a magnetic portion of the rotating member, and the opposing surface magnetically attracts the magnetic portion of the rotating member, thereby biasing the rotating member in the same direction as the biasing direction of the first biasing means.

14. a third biasing means for biasing the rotating member and the first guide mechanism against the fixed member in a radial direction about the rotation axis by a magnetic force, 14. The ultrasonic motor according to claim 9, wherein the third biasing means is disposed between the first biasing means and the second biasing means in a circumferential direction about the rotation axis.

15. 15. The ultrasonic motor according to claim 9, wherein the first guide mechanism is composed of a first V-groove portion fixed to the fixed member, a second V-groove portion fixed to the rotating member, and a rolling member sandwiched between the first V-groove portion and the second V-groove portion.

16. The ultrasonic motor according to any one of claims 9 to 15, characterized in that the second guide mechanism is composed of a third V-groove portion fixed to the fixed member, a fourth V-groove portion fixed to the rotating member, and a rolling member sandwiched between the third V-groove portion and the fourth V-groove portion.

17. An ultrasonic motor according to any one of claims 1 to 16, a movable part that is movable by the ultrasonic motor.

18. An ultrasonic motor according to any one of claims 1 to 16, an imaging unit that is movable by the ultrasonic motor.

Images