Vibration wave driving apparatus and manufacturing method of vibration body

A vibration wave driving apparatus according to the present invention includes a vibrator having at least a vibration body formed with a projecting portion having spring characteristics and an electro-mechanical energy conversion element, the vibration wave driving apparatus using motion of the projecting portion to drive a driven body in contact with the projecting portion, wherein the vibration body includes a base portion and the projecting portion, the projecting portion includes two wall portions formed in parallel to a direction orthogonal to a drive direction of the driven body extending in an out-of-plane direction with respect to the base portion and two wall portions formed in parallel to the drive direction of the driven body extending in an out-of-plane direction with respect to the base portion and a contact portion including a contact surface with the driven body formed by connecting the wall portions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vibration wave driving apparatus and a manufacturing method of a vibration body therefor, and more particularly, to a vibration body serving as a constituent part of a linear ultrasonic motor and a manufacturing method of the vibration body.

2. Description of the Related Art

In the past, a vibration wave driving apparatus (linear ultrasonic motor) as described in Japanese Patent Application Laid-Open No. 2004-304887 has been suggested as a linear ultrasonic motor for linearly driving the driven body. Principle of driving such linear ultrasonic motor will be described with reference toFIGS. 7A to 7C. As shown in an external perspective view illustrating a linear ultrasonic motor inFIG. 7A, a linear ultrasonic motor510includes a vibrator501, a slider506, and a pressing member (not illustrated) for pressing the vibrator against the slider. The vibrator501includes an electro-mechanical energy conversion element505, which is typically a piezoelectric element, and a vibration body that is bonded to one side of the electro-mechanical energy conversion element505so as to be integrated with the electro-mechanical energy conversion element505. The vibration body includes a base portion502, which is formed in a rectangular shape, and two projecting portions503and504, which protrude from the upper surface of the base portion.

In an ultrasonic motor, a voltage having a specific frequency is applied to a piezoelectric element so as to excite a plurality of desired vibration modes, and these vibration modes are superimposed, thereby causing a driving vibration. In the case of the motor illustrated inFIG. 7A, two bending vibration modes are excited in the vibrator501illustrated inFIGS. 7B and 7C. Each of the two bending vibration modes is a bending vibration mode in an out-of-plane direction of the vibrator501, which has a plate-like shape. One of the vibration modes is a second-order bending vibration mode (Mode-A) in the longitudinal direction of the vibrator501, and the other of the vibration modes is a first-order bending vibration mode (Mode-B) in the width direction of the vibrator501. The shape of the vibrator501is designed so that the resonant frequencies of the two vibration modes are the same or close to each other. The projecting portions503and504are each disposed in the vicinity of a node of the vibration in Mode-A. Due to the vibration in Mode-A, end surfaces503-1and504-1of the projecting portions each perform a pendulum motion around a pivot, which is a node of the vibration, and thereby perform a reciprocating motion in the X direction. The projecting portions503and504are each disposed in the vicinity of an antinode of the vibration in Mode-B. Due to the vibration in Mode-B, end surfaces503-1and504-1of the projecting portions each perform a reciprocating motion in the Z direction.

The vibrations in the two vibration modes (Mode-A and Mode-B) are excited simultaneously so that the phase difference between the two vibration modes is about ±π/2, and superimposed, whereby the end surfaces503-1and504-1of the projecting portions each perform an elliptical motion in the XZ plane. Due to the elliptical motions, the slider506, which is in pressed into contact, can be driven in one direction. At this time, the projecting portions503and504of the vibrator501and the slider506intermittently come into contact with each other with the drive frequency of the vibrator501(which is several tens of kHz or higher). Therefore, appropriate contact is not achieved unless either of them have appropriate spring characteristics. The projecting portions503and504also function to amplify the vibration in the X direction as described above.

For the above reason, in order to fulfill these two functions, low-noise driving is realized by giving spring characteristics to the slider side when the configuration of the vibrator described in Japanese Patent Application Laid-Open No. 2004-304887 is made although this is not shown in Japanese Patent Application Laid-Open No. 2004-304887. On the other hand, Japanese Patent Application Laid-Open No. 2008-125147 suggests a vibration actuator in which spring characteristics are given to the projecting portions503and504and the projecting portions503and504are made into appropriate shapes as illustrated inFIGS. 8A to 8C, so that low-noise driving is realized.

SUMMARY OF THE INVENTION

However, in a configuration of a vibration actuator described in Japanese Patent Application Laid-Open No. 2008-125147, there is a limitation in increasing the speed of the motor as described below. One of methods for expanding a vibration amplitude in a feeding direction (X direction) includes increasing the height of a projecting portion. However, when the height of the projecting portion in the vibrator601described in Japanese Patent Application Laid-Open No. 2008-125147 is increased, the stiffness of the projecting portion in the feeding direction is reduced, and the driving efficiency is reduced, and moreover, in the vibration mode for push-up motion, i.e., the mode-B, satisfaction cannot be necessarily obtained when the vibration angle of the end of the projecting portion is made into a desired value. As a result, unnecessary amplitude in the Z direction is generated, which makes the contact with the slider unstable. On the other hand, the vibrator described in Japanese Patent Application Laid-Open No. 2004-304887 can achieve high speed when the height of the protruding portion is increased, but there is a problem in the cost of manufacturing. In view of the above issues, an object of the present invention is to provide a vibration wave driving apparatus that can be manufactured at a low cost and that can increase the speed, and provide a manufacturing method of a vibration body.

A vibration wave driving apparatus according to the present invention includes a vibrator having at least a vibration body formed with a projecting portion having spring characteristics and an electro-mechanical energy conversion element, and the vibration wave driving apparatus uses motion of the projecting portion to drive a driven body in contact with the projecting portion, wherein the vibration body includes a base portion and the projecting portion, the projecting portion includes two wall portions formed in parallel to a direction orthogonal to a drive direction of the driven body extending in an out-of-plane direction with respect to the base portion and two wall portions formed in parallel to the drive direction of the driven body extending in an out-of-plane direction with respect to the base portion and a contact portion including a contact surface with the driven body formed by connecting the wall portions. A manufacturing method of a vibration body according to the present invention for a vibration wave driving apparatus includes a vibrator having at least a vibration body formed with a projecting portion having spring characteristics and an electro-mechanical energy conversion element, and the vibration wave driving apparatus uses elliptical motion of the vibrator to drive a driven body in contact with the projecting portion, the manufacturing method includes preparing a member for integrally forming the projecting portion and the vibration body, and forming a plurality of slits or notches in a region of the member and forming, in a portion sandwiched by the slit or the notch, the projecting portion having two wall portions formed in parallel to a direction orthogonal to the drive direction and two wall portions formed in parallel to the drive direction, using bending processing or drawing.

The present invention can achieve a vibration wave driving apparatus that can be manufactured at a low cost and that can increase the speed, and achieve a manufacturing method of a vibration body therefor.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

A configuration of a vibration wave driving apparatus according to the present invention will be described as a first embodiment. The vibration wave driving apparatus according to the present embodiment includes a vibrator having at least a vibration body formed with projecting portions having spring characteristics and an electro-mechanical energy conversion element, and is configured such that a driven body brought into contact with the projecting portions is driven by elliptical motion of the vibrator. More specifically, as illustrated inFIG. 1, a vibrator111according to the present embodiment includes a piezoelectric element107formed in a rectangular thin plate shape and a vibration body101that is bonded to one end surface of the piezoelectric element107so as to be integrated with the piezoelectric element107. The vibration body101is provided with two projecting portions109,110in contact with a slider (not illustrated), and the slider and the vibration body101are in pressurized contact with each other via the projecting portions109,110. When an alternating voltage is applied to the piezoelectric element107, two bending vibration modes are excited in the vibrator111, and elliptical motion is excited on contact surfaces of the projecting portions109,110. As a result, the slider in pressurized contact with the projecting portions109,110receives frictional driving force, and is driven in the X direction (feeding direction).

Now, the configuration of the vibration body will be described. The vibration body is formed with a base portion and a projecting portion. Further, the projecting portion includes two wall portions formed in parallel to a direction orthogonal to a drive direction of the driven body extending in an out-of-plane direction with respect to the base portion and two wall portions formed in parallel to the drive direction of the driven body extending in an out-of-plane direction with respect to the base portion. In addition, a contact portion having a contact surface with the driven body is provided, wherein the contact portion is formed by connecting these wall portions. More specifically, the vibration body101includes the base portion102and the projecting portions109,110. LikeFIG. 7Billustrated in the conventional art, these projecting portions109,110are formed in proximity to a node of a second-order bending mode (feeding mode). The projecting portions109,110include four wall portions14a,14b,14c,14d, a contact portion16, and fixing portions13a,13b,13c,13d. A surface of the contact portion16is formed with a contact surface brought into pressurized contact with the slider. The wall portions14a,14bare within the same ZY plane. In other words, the projecting portions109,110have two fixing bases in parallel to a direction (Y direction) orthogonal to the feeding direction (X direction). The higher position the contact portion16is formed, the more greatly the stiffness is reduced in the X direction, and which makes it impossible to sufficiently transmit the driving force. Accordingly, the widths of the wall portions14a,14bin the X direction are determined so that the stiffness in the X direction is increased and therefore the amount of deformation with respect to thrust force generated by the vibrator is sufficiently smaller than the vibration amplitude.

The wall portions14c,14dare formed in a direction orthogonal to the wall portions14a,14b.FIG. 6Bis a result of FEM analysis which is carried out when a vibration body and a piezoelectric element are attached with each other where the wall portions14c,14dare omitted from the present embodiment. When the vibration mode for push-up motion (Mode-B as illustrated inFIG. 7C) is excited with only the wall portions14a,14b, the contact portion16is displaced in a direction opposite to the displacement direction in the Z direction of the piezoelectric element under the contact portion16, and this cannot achieve stable driving.

FIG. 6Ais a figure illustrating the vibration mode for push-up motion obtained as a result of carrying out FEM analysis when the vibration body101and the piezoelectric element107are attached with each other according to the present embodiment. In this case, the wall portions14c,14dare provided to support the contact portion16, and therefore, when the vibration mode for push-up motion is excited, the contact portion16is displaced in the same direction as the displacement direction in the Z direction of the piezoelectric element107under the contact portion16, and this achieves stable driving. When the wall portions14c,14dare provided, the stiffness can also be increased in the X direction, and the driving force can be transmitted sufficiently.

While the configuration as illustrated inFIG. 1is maintained, spring characteristics are given to the slider, so that preferable contact state can be achieved between the vibrator111and the slider. Even when the height of the projecting portions109,110is increased to increase the speed, the driving force of the vibrator111can be transmitted efficiently to the slider because the stiffness of the projecting portions109,110in the X direction, i.e., the drive direction of the slider, is ensured by the wall portions14a,14b. As compared with a vibration body501provided with rigid projecting portions503-1,504-1as illustrated inFIG. 7A, the vibration body101according to the present embodiment is configured to have such a structure in which the projecting portions109,110have spring characteristics. Furthermore, the projecting portions109,110are configured to have such a structure that a space is provided between the base portion102and the contact portion16including the respective wall portions described above. In general, the thinner the plate thickness of the vibration body101is, the smaller the bending stiffness becomes. When the present embodiment is employed, the bending stiffness in the vibration mode for push-up motion is reduced, and as a result, electric power efficiency can be enhanced.

Subsequently, an example of manufacturing method of the vibration body101in the vibration wave driving apparatus according to the present embodiment will be hereinafter described. In the present embodiment, the vibration body is made of a stainless steel material, and in particular, the vibration body is made of SUS420J2 or SUS440C, which are wear-resistant. The projecting portions109,110are formed as separate bodies by, for example, press work from a plate material. A flat plate is used as the base portion102. After the projecting portions109,110are positioned with respect to the base portion102, the fixing portions13a,13b,13c,13dof the projecting portions109,110and the base portion102which are in contact with each other are bonded by laser welding or adhesive, whereby the vibration body101is made. According to the configuration of the present embodiment described above, the projecting portion has two wall portions in a parallel direction to the feeding direction, and has two wall portions in a direction orthogonal to the feeding direction, so that even when the height of the projecting portions is increased, the contact portion of the projecting portion can be displaced in the same direction as the piezoelectric element during the vibration mode for push-up motion. Therefore, stable contact with the slider can be achieved, and the speed of the motor can be increased.

Second Embodiment

An example of configuration of second embodiment according to the present invention will be described with reference toFIG. 2. A vibration body201is provided with two projecting portions209,210in contact with a slider (not illustrated), and the slider and the vibration body201are in pressurized contact with each other via the projecting portions209,210. The piezoelectric element (not illustrated) is bonded to a surface opposite to the projecting portions209,210of the vibration body201like the first embodiment. When an alternating voltage is applied to the piezoelectric element, two bending vibration modes are excited in the vibrator, and elliptical motion is excited on contact surfaces of the projecting portions209,210. As a result, the slider in pressurized contact with the projecting portions209,210receives frictional driving force, and is driven in the X direction (feeding direction).

In the present embodiment, through holes are arranged in some portions of the base portion which are sandwiched between the projecting portions and the electro-mechanical energy conversion element. Further, the vibration body201includes the flat plate-like base portion202provided with the through holes21and the projecting portions209,210. LikeFIG. 7Billustrated in the conventional art, these projecting portions209,210are formed in proximity to a node of a second-order bending mode (feeding mode). In this case, the projecting portions209,210include four wall portions24a,24b,24c,24dand a contact portion26. A surface of the contact portion26is formed with a contact surface brought into pressurized contact with the slider. The wall portions24a,24bare within the same ZY plane. In other words, the projecting portions209,210have two fixing bases in parallel to a direction (Y direction) orthogonal to the feeding direction (X direction). Like the first embodiment, in the present embodiment, the widths of the wall portions24a,24bin the X direction are determined so that the stiffness in the X direction is increased and therefore the amount of deformation with respect to thrust force generated by the vibrator is sufficiently smaller than the vibration amplitude.

The wall portions24c,24dare formed in a direction orthogonal to the wall portions24a,24b. Like the first embodiment, when the vibration mode for push-up motion is excited with only the wall portions24a,24b, the contact portion26is displaced in a direction opposite to the displacement direction in the Z direction of the piezoelectric element under the contact portion26, and this cannot achieve stable driving. The wall portions24c,24dare provided to support the contact portion26, and therefore, when the vibration mode for push-up motion is excited, the contact portion26is displaced in the same direction as the displacement direction in the Z direction of the piezoelectric element under the contact portion26, and this achieves stable driving. When the wall portions24c,24dare provided, the stiffness can also be increased in the X direction, and the driving force can be transmitted sufficiently.

While the configuration as illustrated inFIG. 2is maintained, spring characteristics are given to the slider, so that preferable contact state can be achieved between the vibrator and the slider. As compared with the vibration body501provided with the rigid projecting portions503-1,504-1as illustrated inFIG. 7A, the vibration body201according to the present embodiment is configured to have such a structure in which the projecting portions209,210have spring characteristics. Furthermore, the projecting portions209,210are configured to have such a structure that a space is provided between the piezoelectric element and the contact portion26including the respective wall portions described above. In general, the thinner the plate thickness of the vibration body is, the smaller the bending stiffness becomes. When the present embodiment is employed, the bending stiffness in the vibration mode for push-up motion is reduced, and as a result, electric power efficiency can be enhanced.

Subsequently, an example of manufacturing method of the vibration body201in the vibration wave driving apparatus according to the present embodiment will be hereinafter described. In the present embodiment, the vibration body is made of a stainless steel material, and in particular, the vibration body is made of SUS420J2 or SUS440C, which are wear-resistant. In general, the projecting portions209,210and the base portion202are integrally formed from a flat plate member. The projecting portions209,210are made of a flat plate by drawing.

Third Embodiment

An example of configuration of a third embodiment according to the present invention will be described with reference toFIGS. 3A-3B,4A-4B. The vibration body301is provided with two projecting portions309,310in contact with a slider (not illustrated), and the slider and the vibration body301are in pressurized contact with each other via the projecting portions309,310. The piezoelectric element (not illustrated) is bonded to a surface opposite to the projecting portions309,310of the vibration body301like the first embodiment. When an alternating voltage is applied to the piezoelectric element, two bending vibration modes are excited in the vibrator, and elliptical motion is excited on contact surfaces of the projecting portions309,310. As a result, the slider in pressurized contact with the projecting portions309,310receives frictional driving force, and is driven in the X direction (feeding direction). The vibration body301includes projecting portions309,310and a flat plate-like base portion302divided into a plurality of parts. More specifically, a through hole31is provided under the contact portion36of the vibration body301, and a plurality of notch portions32are provided so that the base portion302is divided into a plurality of parts when the projecting portions309,310are removed. End portions of the base portion in parallel to the X direction are separated by the notch portions32, but there is no notch portion at end portions of the base portion in parallel to the Y direction. LikeFIG. 7Billustrated in the conventional art, these projecting portions309,310are formed in proximity to a node of a second-order bending mode (feeding mode). The projecting portions309,310include four wall portions34a,34b,34c,34dand a contact portion36. A surface of the contact portion36is formed with a contact surface brought into pressurized contact with the slider.

The wall portions34a,34bare within the same ZY plane. In other words, the projecting portions309,310have two fixing bases in parallel to a direction (Y direction) orthogonal to the feeding direction (X direction). Like the first embodiment, in the present embodiment, the widths of the wall portions34a,34bin the X direction are determined so that the stiffness in the X direction is increased and therefore the amount of deformation with respect to thrust force generated by the vibrator is sufficiently smaller than the vibration amplitude. The wall portions34c,34dare formed in a direction orthogonal to the wall portions34a,34b. Like the first embodiment, when the vibration mode for push-up motion is excited with only the wall portions34a,34b, the contact portion36is displaced in a direction opposite to the displacement direction in the Z direction of the piezoelectric element under the contact portion36, and this cannot achieve stable driving. The wall portions34c,34dare provided to support the contact portion36, and therefore, when the vibration mode for push-up motion is excited, the contact portion36is displaced in the same direction as the displacement direction in the Z direction of the piezoelectric element under the contact portion36, and this achieves stable driving. By providing the wall portions34c,34d, the stiffness can also be increased in the X direction, and the driving force can be transmitted sufficiently.

As compared with the vibration body501provided with the rigid projecting portions503-1,504-1as illustrated inFIG. 7A, the vibration body301according to the present embodiment is configured to have such a structure in which the projecting portions309,310have spring characteristics. Furthermore, the projecting portions309,310are configured to have such a structure that a space is provided between the piezoelectric element and the contact portion36including the respective wall portions described above. In general, the thinner the plate thickness of the vibration body is, the smaller the bending stiffness becomes. When the present embodiment is employed, the bending stiffness in the vibration mode for push-up motion is reduced, and as a result, electric power efficiency can be enhanced. While the configuration as illustrated inFIG. 2is maintained, spring characteristics are given to the slider, so that preferable contact state can be achieved between the vibrator and the slider.

Subsequently, an example of a manufacturing method of the vibration body301as illustrated inFIG. 3Ain the vibration wave driving apparatus according to the present embodiment will be hereinafter described. In the present embodiment, the vibration body is made of a stainless steel material, and in particular, the vibration body is made of SUS420J2 or SUS440C, which are wear-resistant. A flat plate having a size larger than the entire length of the vibration body301to be manufactured is prepared, and as illustrated inFIG. 3B, notch portions and slits are provided, so that the base portions adjacent to the respective wall portions of the same projecting portion are not in contact with each other. The notch portion is processed by etching or punching through press working, and thereafter, projecting bending portions39a,39b,39c,39dare processed by bending work, so that the projecting portions309,310are integrally formed from a flat plate. The processed shape is as illustrated inFIG. 3A, and a portion of the notch portion is made into a slit having a narrow width. As described above, portions of the base portion sandwiched by the slits or notches are bent and processed, so that they are formed into the projecting portions309,310. Therefore, this achieves processing substantially without changing the plate thickness of the projecting portions309,310before and after the processing. As a result, unlike, for example, drawing and molding requiring a plate with a high elongation rate, this reduces limitation on the height and the shape of the projecting portions309,310that can be manufactured. As compared with the drawing, the wall portions34a,34b,34c,34dcan be formed with a high degree of stiffness while the plate thickness of the projecting portions does not decrease greatly. When the supporting portion is integrally formed with the vibration body to support the vibrator, the supporting portion is provided in proximity to the node of vibration in order not to suppress the vibration of the vibration body. As shown in the figures illustrating the modes inFIGS. 7B and 7Caccording to the conventional example, in the feeding mode, three nodes of vibration exist at respective end portions in parallel to the XZ plane of the vibration body, and in the vibration mode for push-up motion, two nodes of vibration exist at respective end portions in parallel to the YZ plane of the vibration body. The position to which an arm portion of the supporting portion is extended from the vibration body may be a node of vibration in the feeding mode or a node of vibration in the vibration mode for push-up motion. There may be one arm portion or two arm portions which connect the vibration body and the fixing portion of the supporting portion.

In the shape as illustrated inFIG. 3A, when two arm portions39of a supporting portion303extend from two end portions of the vibration body301facing each other, the arm portions39of the supporting portion303extend as illustrated inFIG. 5Afrom portions in proximity to the node of vibration in the mode for push-up motion at the end portion of the vibration body301in parallel to the YZ plane. Accordingly, the gap between the two arm portions39of the supporting portion303is maintained before and after the bending processing, and this can prevent a portion of the supporting portion303from being bent. At this occasion, with regard to the Y direction, the size of the vibrator can be reduced, and with regard to the Y direction, limitation imposed on the size of the vibrator is reduced. When one arm portion39of the supporting portion303extends from each end portion of the vibration body301, the arm portion39of the supporting portion303can extend from the center of the end portions of the vibration body301in parallel to the XZ plane, located in proximity to the node of vibration in the feeding mode. Accordingly, the gap between the two arm portions39of the supporting portion303is maintained before and after the bending processing, and this can prevent a portion of the supporting portion303from being bent. At this occasion, with regard to the X direction, the size of the vibrator can be reduced, and with regard to the X direction, limitation imposed on the size of the vibrator is reduced.

Subsequently, another aspect of the present embodiment will be described. The shape of a vibration body as illustrated inFIG. 4Ais different from that as illustrated inFIG. 3Aof the present embodiment in that positions of a plurality of notch portions32provided on the base portion302are different, and end portions of the base portion302in parallel to the YZ plane are separated by the notch portions32but there is no notch portion at the end portions of the base portion302in parallel to the XZ plane. The shape of the vibration body as illustrated inFIG. 4Acan be processed from the shape as illustrated inFIG. 4Bby the same method as described above.

In the shape as illustrated inFIG. 4A, when two arm portions39of a supporting portion303extend from each end portion of the vibration body301, the arm portions39of the supporting portion303extend as illustrated inFIG. 5Bfrom portions in proximity to two of the three vibration nodes except the center node in the feeding mode located at the end portions of the vibration body301in parallel to the XZ plane. Accordingly, the gap between the two arm portions39of the supporting portion303is maintained before and after the bending processing, and this can prevent a portion of the supporting portion303from being bent. At this occasion, with regard to the X direction, the size of the vibrator can be reduced, and with regard to the X direction, limitation imposed on the size of the vibrator is reduced. When one arm portion39of the supporting portion303extends from each end portion of the vibration body301, the arm portion39of the supporting portion can extend from the center of the end portions of the vibration body301in parallel to the XZ plane, located in proximity to the node of vibration in the feeding mode. At this occasion, with regard to the X direction, the size of the vibrator can be reduced, and with regard to the X direction, limitation imposed on the size of the vibrator is reduced.

This application claims the benefit of Japanese Patent Application No. 2011-098231, filed Apr. 26, 2011, which is hereby incorporated by reference herein in its entirety.