Vibration wave actuator

A vibration wave actuator includes a vibrator having at least an electro-mechanical energy conversion element and an elastic body to which the electro-mechanical energy conversion element is joined, with the elastic body including a contact portion formed therein, and a driven element that is in pressure contact with the contact portion of the vibrator and includes a magnetic substance. In addition, a vibrator holding portion holds the vibrator via a first elastic member having a stiffness lower than that of the vibrator, and a magnet is arranged on the vibrator holding portion such that the vibrator is placed between the driven element and the magnet.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vibratory drive apparatus, such as a vibration wave actuator, and specifically relates to a vibratory drive apparatus that is favorable for use in, e.g., a mechanism that corrects blurring due to hand movements in an optical apparatus such as a camera or binoculars, or a drive mechanism for a table.

2. Description of the Related Art

Conventionally, vibration wave actuators, which are vibratory drive apparatuses that move a driven element in contact with a plurality of vibrators in a plurality of different directions (desired directions), are known. Among such vibration wave actuators, a pressure application-type vibration wave actuator in which a magnet is employed for a driven element is known (Japanese Patent Application Laid-Open No. 2009-027769). Also, Japanese Patent Application Laid-Open No. 2007-312519 proposes a vibratory drive apparatus in which a magnetic member is arranged in a space between a vibrator and a driven element. More specifically, the vibratory drive apparatus is configured so that projection portions that project from a first surface of a vibrator and are in contact with the driven element are formed, and a magnet is arranged between the first surface of the vibrator and the driven element to attract the driven element by means of a magnetic force.FIGS. 14A and 14Billustrate the configuration of a linear vibration wave actuator described in the Japanese Patent Application Laid-Open No. 2007-312519. InFIGS. 14A and 14B, a vibrator52is supported by a holding member57via an elastic supporting member56while preventing the hindering of vibration of the vibrator52by the elastic supporting member56. Furthermore, a magnetic member65including a magnet is arranged on the holding member57and between projection portions58formed on an upper surface of the vibrator52. The magnetic member65is held in a state in which the magnetic member65is not in contact with the vibrator52and a driven element70, and generates a magnetic attraction force MF that attracts the vibrator52and the driven element70in a Z-direction. Pressure is applied by means of the magnetic attraction force.

Also, as another example of vibratory drive apparatuses driving a driven element by means of a vibrator, such as ultrasonic motors, there are ones using a vibrator obtained by integrating a vibration plate including, for example, an elastic metal member, and a piezoelectric element (electro-mechanical energy conversion element) by means of, e.g., adhesion. Among such vibrator-used vibratory drive apparatuses as described above, ones using magnetic force to generate pressure applied to a vibrator and a driven element have been proposed. U.S. Pat. No. 7,425,770 proposes a vibratory drive apparatus including a permanent magnet in at least a part of a vibrator. Also, U.S. Pat. No. 7,518,286 discloses a vibratory drive apparatus including a permanent magnet in at least a part of a driven element.

SUMMARY OF THE INVENTION

However, in the conventional vibratory drive apparatuses, the following problems are left unsolved.

For example, a vibration wave actuator configured to attract a vibrator with pressure using a driven element including a magnet, which is used in Japanese Patent Application Laid-Open No. 2009-027769, has the following problem.FIG. 15Aillustrates results of magnetic flux density calculation using a half-sized model of a rod magnet used for a driven element that is driven to move linearly in the above-described vibration wave actuator.

FIG. 15Billustrates results of magnetic flux density calculation using a half-sized model of a magnet enlarged by extending the aforementioned magnet used for the driven element in a direction perpendicular to the linear movement direction so that the magnet can move in a plurality of directions. In the Figures, a portion with a higher concentration is illustrated with a lower magnetic flux density. Directions in which vibrators (not illustrated) are driven are indicated with arrows.

FIG. 15Aindicates substantially uniform magnetic flux density distribution except an end portion of the driven element. Since the end portion in the longitudinal direction of the driven element inFIG. 15Ais parallel to the drive direction, the vibrator does not pass through (pass over) the end portion of the driven element in which the magnetic flux density is low when the vibrator is driven, and thus, no problem arises. Meanwhile, inFIG. 15B, the magnetic flux density is low in a portion in the vicinity of a center of the driven element, where the vibrator frequently passes through when the vibrator is driven. Here, passage of a vibrator means motion of a vibrator and a driven element crossing each other when the vibrator is driven.

Thus, in a vibration wave actuator enabling driving in a plurality of directions in which a magnet is used for a driven element, a problem occurs in that the pressure is different depending on the positions or drive directions of the vibrators.

Furthermore, in the configuration in which a magnet is arranged between a driven element and a vibrator as in Japanese Patent Application Laid-Open No. 2007-312519, since the size of the magnet is restricted, the increase in the pressure is inevitably limited.

In view of the aforementioned problems, an object of the present invention is to provide a vibration wave actuator enabling enhancement of a pressure-contact force provided by magnetism between a vibrator and a driven element when a magnet is arranged on the vibrator side relative to a surface of contact between the vibrator and the driven element.

Furthermore, e.g., the ultrasonic motor according to the aforementioned conventional example in which pressure is applied to a vibrator and a driven element using a permanent magnet, the mechanism can be simplified compared to those in which pressure is applied using springs. However, in the conventional example configuration in which a magnetic force is used to generate such pressure, a pressure-application mechanism for bringing the vibrator and the driven element into pressure contact with each other has the following problems.

There are consistent demands for downsizing and high-density mounting of, e.g., electronic devices in which ultrasonic motors are included, and further downsizing is demanded for the pressure-application mechanisms of the ultrasonic motors as well. Meanwhile, an output of an ultrasonic motor, especially, a driving force provided by a vibrator to a driven element depends on the pressure applied to the vibrator and the driven element. In other words, the driving force provided by the vibrator to the driven element is conveyed to the driven element via a frictional force generated by the pressure contact with the vibrator, whereby the driven element is moved relative to the vibrator.

Accordingly, the driving force of an ultrasonic motor depends on the pressure that generates a frictional force by means of pressure contact. For the reasons described above, while downsizing and a pressure-application mechanism enabling provision of required pressure are demanded; since in general downsizing leads to a decrease in pressure, the aforementioned conventional configuration has room for further improvement. Furthermore, where magnetic force is used for generation of pressure, imbalance of the pressure may occur.

A magnetic force generates a rotational force relative to an axis parallel to the direction in which a driven element is moved relative to a vibrator. Since the attraction force increases more as the distance between the magnetic member and the object to be attracted becomes smaller, the pressure imbalance may be further increased in such case, for example, where a misalignment and/or an inclination occur depending on a mismatch of the dimensional accuracy and/or installation accuracy.

Accordingly, there is a need for those with a structure that causes no such pressure imbalance.

In view of the aforementioned problems, another object of the present invention is to provide a vibratory drive apparatus capable of downsizing a pressure-application structure while necessary pressure is provided, enabling pressure stabilization.

A vibration wave actuator, which is a vibratory drive apparatus according to the present invention, includes: a vibrator including at least an electro-mechanical energy conversion element and an elastic body to which the electro-mechanical energy conversion element is joined, the elastic body including a contact portion formed therein, the vibrator being configured to provide elliptic motion to the contact portion; and a driven element that is in pressure contact with the contact portion of the vibrator, the driven element being moved by the elliptic motion, wherein the vibration wave actuator includes a vibrator holding portion that holds the vibrator via a first elastic member having a stiffness lower than that of the vibrator; and wherein a magnet is arranged on the vibrator holding portion, the driven element includes a magnetic substance, and the contact portion of the vibrator and the driven element are brought into pressure contact with each other by an attraction force of the magnet.

Also, a vibratory drive apparatus according to the present invention includes: a vibrator including an electro-mechanical energy conversion element and a vibration plate to which the electro-mechanical energy conversion element is joined, the vibrator being configured to provide elliptic motion to a contact portion formed on the vibration plate; and a driven element that is in pressure contact with the contact portion of the vibrator, the driven element being moved relative to the vibrator by the elliptic motion, wherein at least a portion of the driven element includes a ferromagnetic substance, thereby providing a first magnetic member; wherein at least a portion of the vibrator includes a ferromagnetic substance, thereby causing the vibrator and a yoke joined to a supporting portion of the vibrator, the yoke extending in a direction of the relative movement of the driven element, to provide a second magnetic member; and wherein a permanent magnet is provided on any one of the first magnetic member and the second magnetic member, and the contact portion of the vibrator is brought into pressure contact with the driven element by an attraction force provided by magnetic forces of the first magnetic member and the second magnetic member.

The present invention enables provision of a vibration wave actuator, which is a vibratory drive apparatus that enhances a pressure-contact force provided by magnetism between a vibrator and a driven element, enabling stabilization of a state of the contact between the vibrator and the driven element.

Also, the present invention enables provision of a vibratory drive apparatus capable of downsizing a pressure-application structure while necessary pressure is provided, enabling pressure stabilization.

DESCRIPTION OF THE EMBODIMENTS

Modes for carrying out the present invention will be described by means of the embodiments below.

An example configuration of a vibration wave actuator, to which the present invention is applied, will be described with reference toFIGS. 3A and 3B. In the vibration wave actuator, a driven element that is in contact with a plurality of vibrators is moved in a plurality of different directions. The example configuration of the present embodiment includes a plurality of vibrators, and the plurality of vibrators is arranged at positions where the directions of forces generated by elliptic motion are different. The configuration is provided so that the driven element that is in pressure contact with the vibrators via contact members of the vibrators is moved in a predetermined movement direction formed by combining the forces in different directions.

FIG. 3Ais a top view of the vibration wave actuator of the present configuration, andFIG. 3Bis a side view of the same. InFIG. 3A, a driven element4is not illustrated. The configuration inFIGS. 3A and 3Bincludes: vibrator units11(a),11(b),11(c) and11(d) each including a vibrator according to the present embodiment; the driven element4; a securing portion9that secures the vibrator units11(a),11(b),11(c) and11(d); and a plurality of balls12arranged between the driven element4and the securing portion9. The plurality of balls12are housed in a plurality of holes arranged in the securing portion9, respectively. The balls revolve in the holes with movement of the driven element4, thereby the driven element4being freely driven within the plane, and supported so as to constantly have a fixed height relative to the securing portion9. Furthermore, the vibrator units11(a),11(b),11(c) and11(d) are connected to the securing portion9via second elastic members8.

Here, for ease of description of a basic configuration of the vibrators, a configuration in which a driven element is driven in a single direction will be described.

FIG. 6is a diagram illustrating a basic configuration of a vibrator mounted in one of the vibrator units.

The details of a drive method is described in Japanese Patent Application Laid-Open No. 2004-320846, and an overview of a configuration enabling projection portions included in contact members of a vibrator to produce elliptic motion will be described herewith.

FIGS. 7A and 7Bare diagrams illustrating two bending vibration modes of the vibrator. The vibration mode inFIG. 7Arepresents one bending vibration mode (hereinafter referred to as “MODE-A”) of the two bending vibration modes. The MODE-A provides second-order bending motion in a long-side direction (arrow X direction) of a rectangular vibrator106, and the vibrator106includes three nodes parallel to a short-side direction (arrow Y direction) thereof. Here, projection portions108included in contact portions are arranged in the vicinity of positions in which nodes are formed in MODE-A vibration, and are reciprocated mainly in the arrow X direction (feed direction) in response to the MODE-A vibration.

The vibration mode illustrated inFIG. 7Brepresents the other bending vibration mode (referred to as “MODE-B”) of the two bending vibration modes. The MODE-B provides first-order bending motion in the short-side direction (arrow Y direction) of the rectangular vibrator106, and the vibrator106includes two nodes parallel to the long side direction (arrow-X direction).

Here, the nodes in the MODE-A and the nodes in the MODE-B are substantially orthogonal to each other in the X-Y plane. Furthermore, the projection portions108are arranged in the vicinity of positions in which antinodes are formed by vibrations in the MODE-B, and are reciprocated in an arrow Z direction (upthrust direction) in response to the MODE-B vibration.

The above-described MODE-A and MODE-B vibrations are generated with a predetermined phase difference, causing elliptic motion at extremities of the projection portions108to provide a driving force in the arrow X direction inFIG. 7A.

The principle of driving the vibration wave actuator according to the present embodiment in which a driven element that is in contact with a plurality of vibrators is moved in a plurality of different directions will be described.

InFIGS. 3A and 3B, when the driven element4is intended to be moved in the X-direction of coordinates illustrated in the Figures, a driving force in an arrow xA direction is provided to the vibrator in the vibrator unit11(a), and a driving force in an arrow xD direction is provided to the vibrator in the vibrator unit11(d). Concurrently, only the above-described MODE-B vibration is provided to the vibrator in the vibrator unit11(b) and the vibrator in the vibrator unit11(c). With the vibration, a load imposed on a surface of contact between the vibrators in the vibrator units11(b) and11(c) and the driven element4is reduced, and the driving forces from the vibrators in the vibrator units11(a) and11(d) are conveyed to the driven element4with no wastage, and the driven element4is driven in the X-direction. When the driven element4is intended to be driven in the Y direction, the MODE-B vibration may be provided to the vibrators in the vibrator units11(a) and11(d), as well as providing a driving force in an arrow xB direction to the vibrator in the vibrator unit11(b) and a driving force in an arrow xC direction to the vibrator in the vibrator unit11(c).

The driving forces of the vibrators in the vibrator units11(a) and11(d) are made to be equal to each other and are each determined as a force vector Fx, and also the driving forces of the vibrators in the vibrator units11(b) and11(c) are made to be equal to each other and are each determined as a force vector Fy. Consequently, combination of the force vectors Fx and Fy enables driving the driven element4in any direction.

Although the present embodiment employs four vibrators, the number of vibrators used for providing a vibration wave actuator that is driven in a plurality of direction as described above is not limited as long as the number is no less than two.

Next, an example configuration of a vibrator unit according to the present embodiment will be described with reference toFIGS. 1A,1B,1C and1D.FIG. 1Ais a perspective view of a vibrator unit11according to embodiment 1, which is the present embodiment.FIG. 1Bis a cross-sectional view of a vibration wave actuator according to embodiment 1, at which position the vibration wave actuator mounts a vibrator unit and11(d) a driven element4, viewed in the X-direction.FIG. 1Cis a cross-sectional view of the vibration wave actuator according to embodiment 1, at which position the vibration wave actuator mounts a vibrator unit11(d) and a driven element4, viewed in the Y direction.FIG. 1Dis a back view of the vibration wave actuator in which a magnet is not illustrated.

InFIGS. 1A,1B,1C and1D, a vibrator1is configured by joining a vibration plate2, which includes an elastic body of, e.g., a metal, and an electro-mechanical energy conversion element3such as a piezoelectric element. A driven element4includes a magnetic substance. Projection portions10, which are the above-described contact portions, are formed on the elastic body.

The vibrator1is connected to a vibrator holding portion6via first elastic members5formed by narrowing the width of parts of the vibration plate2so as to have a stiffness lower than that of the vibrator as well as to have elasticity. As a result of the vibrator1being held as described above, vibration is unlikely to be hindered. A magnet7is held by the vibrator holding portion6so that the driven element4is attracted toward the vibrator1via the vibrator1. In the present embodiment, a vibrator unit11includes at least the vibrator1, the vibrator holding portion6and the magnet7. In the vibration wave actuator according to the present embodiment, the driven element4, the vibrator1, the vibrator holding portion6and the magnet7are aligned in a pressure-application direction.

The vibrator holding portion6is connected to a securing portion9via second elastic members8. The stiffness of the first elastic members5is higher than a stiffness of the second elastic members8. Since the stiffness of the second elastic members8is lower than that of the first elastic members5, it is possible to prevent the first elastic members5from deforming when a force urging the vibrator1to incline is imposed on surfaces of the projection portions10on the vibrator1, which are in contact with the driven element4.

Only the second elastic members8elastically deform so as to rotate in the directions of arrows φx1, φx2, φy1and φy2inFIG. 1D. In other words, when the projection portions10and the driven element4are brought into pressure contact with each other, the second elastic members elastically deform so that the vibrator holding portion follows the driven element4. Here, the vibrator1and the vibrator holding portion6move integrally accompanying the elastic deformation of the second elastic member8, and thus, the contact between the vibrator1and the driven element4is stabilized. Since the state of the contact between the vibrator and the driven element largely affects the output characteristics, the above-described configuration enables suppression of a decrease in the output characteristics.

As a result of arranging the magnet on a side opposite to the side on which the projection portions of the vibrator are provided as described above, there is no restriction in terms of the size, in particular, the size in the magnetization direction of the magnet, and thus, a magnet having a larger attraction force can be used and a large pressure can arbitrarily be set.

InFIGS. 1A,1B,1C and1D, the size in the X-Y plane of the magnet7is smaller than the size in the X-Y plane of the driven element4, and in such state, a magnetic circuit has only a small change when the driven element4is moved in an arbitrary direction within the X-Y plane. Thus, change in attraction force due to a magnetic force can be reduced.

Furthermore, where the vibration plate (elastic body)2includes a magnetic substance, the following effect can be provided.

FIGS. 2A and 2Billustrate simulation results of magnetic flux density distributions in the configuration according to the present embodiment.FIG. 2Aillustrates a magnetic flux density distribution when the vibration plate includes no magnetic substance, andFIG. 2Billustrates a magnetic flux density distribution when the vibration plate includes a magnetic substance. InFIG. 2A, the magnetic flux between the magnet7and the driven element4are scarce and dispersed. However, inFIG. 2B, the magnetic flux between the magnet7, and the vibration plate2and the driven element4is dense, and the magnetic flux concentrates around the vibration plate2and the contact portions between the projection portions10provided on the vibration plate2and the driven element4. Accordingly, it is possible to increase the pressure. As the material of the driven element4of the present invention magnetic substance may be used. And, as the magnet7used in the invention it is desirable to use permanent magnets. In addition, it is desirable to use a ferromagnetic substance as the magnetic sub stance.

An example configuration of a vibration wave actuator according to embodiment 2 will be described with reference toFIG. 4. The overall configuration of the vibration wave actuator is generally similar to the configuration inFIGS. 3A and 3B, which have been described in embodiment 1, and thus, a description thereof will be omitted. The present embodiment will be described only in terms of differences from embodiment 1. A vibrator1is configured by joining a vibration plate2, which includes an elastic body of, e.g., a metal, and an electro-mechanical energy conversion element3. A driven element4includes a magnetic substance.

The vibrator1is connected to a vibrator holding portion6via first elastic members13formed by narrowing parts of the vibration plate2to have a stiffness lower than that of the vibrator as well as to have elasticity. As a result of holding the vibrator1as described above, vibration is unlikely to be hindered. Each first elastic member13is provided in a range of 0°<θ<180° so that the distance between the vibrator1and the vibrator holding member6is large. A magnet7is provided between the vibrator holding portion6and the vibrator1, and the magnet7is held integrally with the vibrator holding portion6so that the driven element4is attracted toward the vibrator1via the vibrator1. The driven element4, the vibrator1, the vibrator holding portion6and the magnet7are aligned in a pressure-application direction.

Furthermore, the vibrator holding portion6is connected to a securing portion9via second elastic members8. The stiffness of the first elastic members13is higher than a stiffness of the second elastic members8.

In embodiment 1, the magnet is arranged on a surface opposite to the vibrator side of the vibrator holding portion6, and thus, it is difficult to narrow the gap between the driven element4and the magnet7. Meanwhile, as a result of the magnet being arranged between the vibrator holding portion and the vibrator on the vibrator side of the vibrator holding portion as in the present embodiment, the gap between the driven element4and the magnet7can be reduced compared to embodiment 1. Accordingly, the pressure can be increased compared to embodiment 1.

An example configuration of a vibration wave actuator according to embodiment 3 will be described with reference toFIG. 5. The overall configuration of the vibration wave actuator in this embodiment is generally similar to those of embodiments 1 and 2. A description will be provided only in terms of differences from embodiments 1 and 2. The vibrator1is configured by joining a vibration plate2, which includes an elastic body of, e.g., a metal, and an electro-mechanical energy conversion element3. A driven element4includes a magnetic substance.

The vibrator1is connected to a vibrator holding magnet14, which includes a magnet, via first elastic members5formed by narrowing the width of parts of the vibration plate2to have a stiffness lower than that of the vibrator as well as to have elasticity. As a result of the vibrator1being held as described above, vibration is unlikely to be hindered.

The vibrator holding magnet14attracts the driven element4toward the vibrator1via the vibrator1. The vibrator holding magnet14is also connected to a securing portion9via second elastic members8. The stiffness of the first elastic members5is higher than a stiffness of the second elastic members8.

In embodiment 1, it is difficult to reduce the size in the thickness direction because the vibrator holding portion and the magnet are formed by separate components. However, with the configuration of the present embodiment, the magnet and the vibrator holding portion are integrated, enabling thickness reduction compared to embodiment 1.

In other aspects of the vibratory drive apparatus according to the present invention, a yoke for collecting magnetic lines of force of a magnet to efficiently use an attraction force the magnet has is made to extend in a direction of relative movement of a driven element. Then, a supporting portion for a vibrator, which is formed in the vibrator, and the yoke are joined.

As a result of the yoke being arranged along the driven element as described above, a magnetic force can be generated between the yoke and the driven element. Furthermore, at least parts of a vibration plate included in the vibrator include a ferromagnetic substance, and such parts can also generate magnetic pressure to attract the driven element.

Furthermore, as a result of employing a configuration in which only contact portions of the vibrator, which are in contact with the driven element, include a ferromagnetic substance, a magnetic attraction force can easily be generated because of the contact with the driven element, and the contact portions directly generate pressure, enabling suppression of a rotational force relative to an axis parallel to the relative movement direction. Furthermore, as a result of employing a configuration in which the supporting portion formed in the vibrator is made to extend in the direction of the relative movement of the driven element to join the supporting portion to a yoke, the vibrator can be held and secured by the yoke.

As a result of employing a configuration in which a joint portion between the supporting portion formed in the vibrator and the yoke is made to have a width narrower than the width of the driven element, the yoke can generate a large attraction force at the joint portion. The attraction force can be made to be close to the contact portions, enabling suppression of generation of a rotational force relative to the axis parallel to the relative movement direction of the driven element.

As embodiment 4, an example configuration of an ultrasonic motor (vibratory drive apparatus), to which the present invention is applied, will be described with reference toFIG. 8. An ultrasonic motor210, which is a vibratory drive apparatus according to the present embodiment, mainly includes a vibrator201, and a driven element206held by the vibrator201in such a manner that the driven element206is in pressure contact with the vibrator201. The vibrator201includes a piezoelectric element (electro-mechanical energy conversion element)213, and a vibration plate211including an elastic body, to which the piezoelectric element213is joined. On the vibration plate211, contact portions212, which are in contact with the driven element, are provided. The driven element206includes an iron-based metal, which is a ferromagnetic substance, and portions of the driven element206that are in contact with the vibrator201have been subjected to processing for enhancing abrasion resistance, such as nickel plating. The driven element206acts as a first magnetic member.

Furthermore, a yoke203for collecting magnetic lines of force is provided. The yoke203can be joined to supporting portions211-2(seeFIG. 10A) formed in the vibrator201. Furthermore, a planar surface of a magnet member204is connected to a planar surface of the yoke203, and the aforementioned components from the vibrator201to the magnetic member204are held and secured by a holding member205. In addition to the aforementioned components, the ultrasonic motor includes, e.g., a flexible substrate (not illustrated) that provides electric connection between the vibrator201and the outside, and a guide member (not illustrated) for the driven element206.

In order to make the ultrasonic motor210operate, an alternate voltage is applied to the piezoelectric element213to excite the vibrator201to enter two out-of-plane bending modes.FIGS. 9A and 9Billustrate shapes of a vibration portion211-1in the vibration modes used in this case. MODE-C illustrated inFIG. 9Ais a first-order out-of-plane bending mode in which two nodes appear in the vibration portion211-1in parallel to an X-direction in the Figure. With the MODE-C vibration, contact portions are excited to have a vibration amplitude for displacement in a Z-axis direction (direction perpendicular to the vibration plate211). MODE-D illustrated inFIG. 9Bis a second-order out-of-plane bending mode in which three nodes appear in the vibration portion211-1substantially in parallel to a Y direction in the Figure. With the MODE-D vibration, the contact portions are excited to have a vibration amplitude for displacement in an X-axis direction (direction parallel to the vibration plate211).

Combination of these two modes enables production of elliptic motion on the surfaces of the contact portions212. The elliptic motion makes the driven element206, which is in pressure contact with the contact portions212, move relative to the vibrator.

FIG. 10Ais a plan view of the ultrasonic motor, which mainly illustrates a configuration of the vibrator201. As illustrated inFIG. 10A, the vibrator201includes a vibration plate211prepared by forming a paramagnetic substance metal material, such as aluminum, into a plate-like shape. The vibration plate211includes a substantially rectangular vibration portion211-1, connection portions211-3extending from side surfaces of the vibration portion211-1so as to face each other, and supporting portions211-2formed at end portions of the connection portions211-3. Contact portions212including a ferromagnetic substance such as an iron-based metal are secured to two positions in a planar portion of the vibration portion211-1.

A piezoelectric element213(electro-mechanical energy conversion element) is connected to another surface of the vibration portion211-1, as illustrated inFIG. 10B. The vibrator201has a shape that is substantially symmetrical in the X and Y directions illustrated inFIG. 10A. A driven element206is arranged on a surface side including the contact portions212of the vibrator201.

The positions of the vibrator201and the driven element206are determined so that the centers in the Y direction of the vibrator201and the driven element206correspond to each other when viewed in the Z direction. The vibrator201and the driven element206move in relation to each other in the X-direction. The supporting portions211-2are arranged at positions where the supporting portions211-2is overlapped by the driven element206when viewed in the Z direction. Furthermore, the supporting portions211-2each have a width narrower than that of the driven element206.

As illustrated inFIGS. 10B and 10C, the two supporting portions211-2extend from the vibration portion211-1of the vibrator in the X-direction, and yoke end portions203-2, which are opposite ends of the yoke203extending from the X-direction in the Figures, are connected to surfaces of the two supporting portion211-2opposite to a surface facing the driven element206.

The width of the yoke end portions203-2have been formed so as to be the same as or narrower than that of the supporting portions211-2. A magnetic member204is arranged in a portion of the yoke203near the piezoelectric element plate213. The magnetic member204has been subjected to processing for magnetization in the Z direction in the Figures. A holding member205extending in the Y direction in the Figures is secured to the magnetic member204. The holding member205includes a plate of phosphor-bronze, which is a paramagnetic substance, and has an elastic structure having a plate-spring shape. Opposite ends in the Y direction in the Figures of the holding member205are held by and secured to a non-illustrated frame body.

These components are included in the drive member214(seeFIG. 8) and the drive member214generates a force for movement in the X direction in the Figures relative to the driven element206. The drive member214is held by the holding member205, and the elastic structure of the holding member205provides a deformation degree of freedom mainly with reference to the Z direction and the X and Y axes in the Figures. Thus, even though a deviation from a desired positional relationship is caused between the drive member214and the driven element206, the drive member214and the driven element206are in contact with each other by means of a magnetic attraction force so as to follow each other.

In the present embodiment, the magnetic member204, the yoke203and the two contact portions212including a ferromagnetic substance in the drive member214, which have been described above, form a second magnetic member. Magnetic lines of force running from a top surface in the Y direction, that is, the vicinity of the vibrator, of magnetic member204are directed substantially in the Y direction and partially pass through the contact portions212. The magnetic lines of force pass through the driven element206, which is the first magnetic member. Furthermore, a part of the magnetic lines of force running from the magnetic member204directly pass through the driven element206. A part of the magnetic lines of force passing through the driven element206is directed to the ends extending in the X-direction of the yoke203. The magnetic lines of force passing through the yoke203return to the magnetic member204connected to the yoke203.

As a result of the magnetic lines of force running as described above, a magnetic force of the magnetic member204can effectively be used for an attraction force between the drive member214and the driven element206.

The above-described configuration of the present embodiment enables provision of an ultrasonic motor with the following configurations. A configuration in which the magnetic member204is arranged in the vicinity of the vibrator to reduce the distance between the magnetic member204and the driven element206, thereby obtaining an attraction force can be employed. Also, a configuration in which contact portions212include a ferromagnetic substance to collect magnetic forces generated from the magnetic member204into the contact portions212can be employed. Furthermore, a configuration in which the contact portions212are made into direct contact with the driven element206to effectively generate an attraction force can be employed.

Furthermore, a configuration in which the yoke203is formed so as to be connected to the supporting portions211-2and the yoke203is positioned in the vicinity of the driven element206to effectively generate an attraction force also between the driven element206and the yoke203can be employed. Furthermore, a configuration in which the yoke203and the magnetic member204are made into direct contact with each other to collect magnetic lines of force can be employed. Furthermore, a configuration in which the yoke also acts so as to hold the vibrator201, eliminating the need to provide a separate part for holding the vibrator201can be employed.

Furthermore, a configuration in which in the drive member214, a force of attracting the driven element206is generated mainly by the contact portions212and the yoke end portions203-2, which are components concentrating in the vicinity of the center in the Y direction in FIGS.10A,10B and10C can be employed. Consequently, even when a misalignment in the Y direction occurs between the drive member214and the driven element206, generation of a moment around the X axis by a magnetic force can be suppressed.

The above-described configurations of the present embodiment enable generation of a sufficient attraction force caused by a magnetic force, that is, a sufficient pressure applied to the drive member214and the driven element206with small components. Furthermore, a biased pressure caused by a misalignment between the drive member and the driven element206can be reduced.

As embodiment 5, an example configuration of an ultrasonic motor (vibratory drive apparatus) in a mode different from that of the embodiment 4 will be described with reference toFIG. 11. A description of components similar to those in embodiment 1, which are illustrated inFIGS. 8 and 10Ato10C, will be omitted.

In the present embodiment, a vibration plate211includes an iron-based ferromagnetic metal. In the case of the present embodiment, contact portions212may be provided by subjecting the vibration plate211to press molding to form projections. Although as in embodiment 4, separate members may be secured to the vibration plate211as the contact portions212, the press molding can simplify the process and reduce the cost.

A holding member205, a yoke203and a magnetic member204are arranged in this order from a vibrator1toward the lower side in the Z direction in the Figures. Yoke end portions203-2of the yoke203, as with the one illustrated inFIG. 8, are connected to supporting portions211-2of the vibrator. In the present embodiment, in addition to the magnetic member204, the yoke203and the holding member205, the vibration plate211acts as a second magnetic member. Also, the yoke203, the vibration plate211and the contact portions212have a same magnetic polarity.

According to the present embodiment, the vibration plate211, positioned in the vicinity of the driven element206which is acting as a first magnetic member, acts as a magnetic member, enabling more effective generation of an attraction force, that is, pressure applied to a drive member214and a driven element206.

As embodiment 6, an example configuration of an ultrasonic motor (vibratory drive apparatus) in a mode in which embodiment 5 has been varied will be described with reference toFIG. 12.

In the present embodiment, a driven element206is formed by connecting a permanent magnet208and a friction member207. The friction member207is used with its hardness enhanced by subjecting a martensitic stainless steel, which is a ferromagnetic substance, to quenching. Also, here, no magnetic member is provided in a drive member214. Effects similar to those in embodiment 5 can also be provided where a permanent magnet is arranged on a first magnetic member side as in the present embodiment.

As embodiment 7, an example configuration of an ultrasonic motor (vibratory drive apparatus) in a mode that is different from that of embodiment 6, which is an variation of embodiment 5, will be described with reference toFIG. 13.

In the present embodiment, a second yoke209is arranged on an open surface of the magnet204in the mode illustrated inFIG. 11. Opposite ends of the second yoke209extend in an X-direction in the Figure and toward the vicinity of a bottom surface of a driven element206. The second yoke end portions209-2are formed so as to have a width narrower than the width of the driven element206.

As a result of employing a configuration in which a permanent magnet is arranged on a yoke (first yoke) and a second yoke extending in the direction of the relative movement of the driven element is provided on the permanent magnet arranged on the first yoke, a large pressure can be generated.

In other words, the first yoke, the permanent magnet, the second yoke and the magnetic member formed on the driven element are included in a magnetic circuit, enabling generation of a large pressure.

Arrangement of the second yoke209as in the present embodiment enables further enhancement of an attraction force, that is, pressure applied to the drive member214and the driven element206.

Furthermore, in the present embodiment, a vibration plate211may include a paramagnetic substance. As a result of the vibration plate211including a paramagnetic substance, as described in embodiment 4, even when a displacement in the Y direction occurs between a drive member214and the driven element206, generation of a moment around the X axis by a magnetic force can be suppressed.

This application claims the benefit of Japanese Patent Application Nos. 2010-109022, filed May 11, 2010, and 2010-148513, filed Jun. 30, 2010, which are hereby incorporated by reference herein in their entirety.