JP2008236908A - Vibration actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration actuator having high retainability and long service life. <P>SOLUTION: When a vibration means 3 stops its driving, a voltage is not applied from a driving circuit 5 to a deformable element 11, and the deformable element 11 has a predetermined thickness H0 without expanding or shrinking. At this time, a rotor 8 is pressurized to a stator 2 via the deformable element 11 and a reloading member 12 by an urging force of a plate spring 10. On the other hand, when the vibration means 3 is driven, a predetermined negative voltage is applied from the driving circuit 5 to the deformable element 11, the deformable element 11 shrinks to a thickness smaller than the predetermined thickness H0 and the urging force of the plate spring 10 is reduced. As a result, a reloading force of the rotor 8 to the stator 2 is reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a vibration actuator, and more particularly to a vibration actuator that rotationally drives a rotor in contact with a stator by generating ultrasonic vibration in the stator.
About.

  In recent years, vibration actuators for rotating a rotor using ultrasonic vibration have been proposed and put into practical use. In this vibration actuator, an elliptical motion or traveling wave is generated on the surface of the stator using a piezoelectric element, and the rotor is moved in a frictional force between the two by bringing the rotor into pressure contact with the stator.

  For example, in Patent Document 1, a spring is connected to a rotating shaft fixed to the rotor surface via a bearing so that a preload is applied to the rotor so that the rotor is pressed against the stator, and the rotors are overlapped with each other in that state. A vibration actuator is disclosed that rotates a rotor by applying a driving voltage to a plurality of piezoelectric element plates to generate ultrasonic vibrations in a stator. In this vibration actuator, a pre-pressure is applied to the rotor by a spring to press the rotor against the stator. Therefore, when no driving voltage is applied to the plurality of piezoelectric element plates, the rotational position of the rotor is maintained.

JP 2004-312809 A

In the vibration actuator of Patent Document 1 described above, by increasing the spring force of the spring, the preload can be increased to increase the holding force of the rotor. However, the holding force increases by increasing the preload, There is a problem that the amount of wear at the contact portion between the rotor and the stator during driving increases, and the life as a vibration actuator is shortened.
The present invention has been made to solve such problems, and an object thereof is to provide a vibration actuator having both a high holding force and a long life.

The vibration actuator according to the present invention includes a stator, a preload member, a rotor sandwiched between the stator and the preload member, preload means for applying a preload between the stator and the preload member and pressurizing the rotor to the stator. And vibration means for rotating the rotor by generating ultrasonic vibrations in the stator, the preload means includes a deformation element, and changes the preload by deforming the deformation element.
Here, the pre-pressure means a pressure that presses the rotor against the stator at least in a state where the vibration means is not driven.

  Preferably, the deformation element has a piezoelectric element.

The preload means can also be configured to include a support member that supports the preload member with respect to the stator. At this time, the deformation element may be disposed between the stator and the support member.
Moreover, the base part which supports a vibration means is further provided, and a preload means can also be comprised so that the support member which supports a preload member with respect to a base may be included. At this time, the deformation element may be disposed between the base and the support member. Further, the vibration unit may include a plurality of piezoelectric elements that generate vibrations in different directions, and the deformation element may also serve as one of the plurality of piezoelectric elements of the vibration unit.
Further, as described above, in both the case where the preload means includes a support member that supports the preload member with respect to the stator and the case where the preload means includes a support member that supports the preload member with respect to the base, the deformation element is Further, it may be disposed between the preload member and the support member.

  According to the present invention, a vibration actuator having both a high holding force and a long life can be realized.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 shows a vibration actuator according to Embodiment 1 of the present invention. This vibration actuator is an ultrasonic actuator that rotates a rotating body using ultrasonic vibration. A cylindrical vibration means 3 is sandwiched between the base 1 and the stator 2, and the base 1 and the stator 2 are connected to each other via a connecting bolt 4 passed through the vibration means 3. As a whole, it has a substantially cylindrical outer shape. Here, for convenience of explanation, the central axis of the cylindrical outer shape from the base 1 toward the stator 2 is defined as the Z axis, and the X axis is perpendicular to the Z axis and perpendicular to the Z axis and the X axis. It is assumed that the Y-axis extends respectively.

  The vibration means 3 includes flat plate-like first to third piezoelectric element portions 31 to 33 that are positioned on the XY plane and overlap each other. These first to third piezoelectric element portions 31 to 33 are electrically connected to the drive circuit 5 respectively.

  The stator 2 has a recess 6 formed on the surface opposite to the surface in contact with the vibration means 3, and an annular corner 7 positioned on the XY plane is formed on the peripheral edge of the opening end of the recess 6. ing. A substantially spherical rotor 8 having a diameter larger than the inner diameter of the recess 6 of the stator 2 is rotatably contacted with the corner portion 7.

A support member 9 is fixed on the upper surface of the stator 2 so as to be bridged in an arch shape above the rotor 8. A deforming element 11 is supported in a suspended manner via a disc spring 10 at the center of the ceiling 9 a of the support member 9, and a preload member 12 is fixed to the tip of the deforming element 11. The preloading member 12 has a concave conical surface-shaped preloading surface 13, and this preloading surface 13 is in contact with the surface of the rotor 8 near the top that is the highest point in the + Z-axis direction.
The disc spring 10 is arranged in a compressed state, and the urging force of the disc spring 10 causes the preload surface 13 of the preload member 12 to be pressed against the rotor 8 via the deformation element 11, and the rotor 8 is pressed in the −Z axial direction. The pre-pressure is given. Thereby, the rotor 8 is pressurized to the stator 2.

The deformation element 11 is electrically connected to the drive circuit 5 similarly to the first to third piezoelectric element portions 31 to 33.
The preload surface 13 of the preload member 12 is coated with a low friction material such as Teflon (registered trademark).

  As shown in FIG. 2, the deformation element 11 has a structure in which an electrode plate 11a, a piezoelectric element plate 11b, an electrode plate 11c, a piezoelectric element plate 11d, and an electrode plate 11e are sequentially stacked. Insulating sheets 14 and 15 are disposed on both surfaces of the deforming element 11, respectively, and the deforming element 11 is disposed in a state of being insulated from the disc spring 10 and the preload member 12 through the insulating sheets 14 and 15. Further, as shown in FIG. 3, the piezoelectric element plates 11b and 11d are polarized so that the whole of the piezoelectric element plates 11b and 11d expands or contracts in the Z-axis direction (thickness direction). The element plates 11d are arranged inside out.

Here, the electrode plate 11a and the electrode plate 11e disposed on both surface portions of the deformation element 11 are electrically grounded, and the electrode plate 11c disposed between the pair of piezoelectric element plates 11b and 11d. The drive circuit 5 is electrically connected.
When a positive DC voltage is applied from the drive circuit 5 to the electrode plate 11c of the deformation element 11, the piezoelectric element plates 11b and 11d extend in the Z-axis direction (thickness direction), whereas when a negative DC voltage is applied, the piezoelectric element plates 11b and 11d The element plates 11b and 11d are configured to shrink in the Z-axis direction (thickness direction).

  As shown in FIG. 4, the first piezoelectric element portion 31 in the vibration means 3 includes an electrode plate 31a, a piezoelectric element plate 31b, an electrode plate 31c, a piezoelectric element plate 31d, and an electrode plate 31e each having a disk shape. Have a structure of being sequentially stacked. Similarly, the second piezoelectric element portion 32 has a structure in which an electrode plate 32a, a piezoelectric element plate 32b, an electrode plate 32c, a piezoelectric element plate 32d, and an electrode plate 32e each having a disk shape are sequentially stacked. 3 has a structure in which an electrode plate 33a, a piezoelectric element plate 33b, an electrode plate 33c, a piezoelectric element plate 33d, and an electrode plate 33e each having a disk shape are sequentially stacked. These piezoelectric element portions 31 to 33 are arranged in a state of being insulated from the stator 2 and the base portion 1 through insulating sheets 34 to 37 and from each other.

As shown in FIG. 5, the pair of piezoelectric element plates 31 b and 31 d of the first piezoelectric element portion 31 has portions that are divided into two in the Y-axis direction and have opposite polarities, and each has a Z-axis direction (thickness direction). The piezoelectric element plate 31b and the piezoelectric element plate 31d are disposed so as to be reversed with respect to each other.
The pair of piezoelectric element plates 32b and 32d of the second piezoelectric element portion 32 are polarized so as to be expanded or contracted in the Z-axis direction (thickness direction) as a whole without being divided into two. The element plate 32b and the piezoelectric element plate 32d are arranged inside out.
In the pair of piezoelectric element plates 33b and 33d of the third piezoelectric element portion 33, the portions divided into two in the X-axis direction have opposite polarities, and are opposite to expansion and contraction in the Z-axis direction (thickness direction), respectively. The piezoelectric element plate 33b and the piezoelectric element plate 33d are disposed so as to be reversed with respect to each other.

  An electrode plate 31a and an electrode plate 31e disposed on both surface portions of the first piezoelectric element portion 31, an electrode plate 32a and an electrode plate 32e disposed on both surface portions of the second piezoelectric element portion 32, and a third The electrode plate 33a and the electrode plate 33e disposed on both surface portions of the piezoelectric element portion 33 are electrically grounded. Further, the electrode plate 31 c disposed between the pair of piezoelectric element plates 31 b and 31 d of the first piezoelectric element portion 31 and the pair of piezoelectric element plates 32 b and 32 d of the second piezoelectric element portion 32 are disposed. The electrode plate 32 c disposed between the pair of piezoelectric element plates 33 b and 33 d of the third piezoelectric element portion 33 is electrically connected to the drive circuit 5.

  Here, when an AC voltage having a frequency close to the natural frequency of the stator 2 is applied to the vibration means 3 to the electrode plate 31 c of the first piezoelectric element portion 31, a pair of piezoelectric elements of the first piezoelectric element portion 31 is applied. The two divided portions of the plates 31b and 31d alternately expand and contract in the Z-axis direction, and generate flexural vibration in the Y-axis direction in the stator 2. Similarly, when an AC voltage is applied to the electrode plate 32c of the second piezoelectric element portion 32, the pair of piezoelectric element plates 32b and 32d of the second piezoelectric element portion 32 repeats expansion and contraction in the Z-axis direction, and the stator 2 In the Z axis direction. Further, when an AC voltage is applied to the electrode plate 33c of the third piezoelectric element portion 33, the two divided portions of the pair of piezoelectric element plates 33b and 33d of the third piezoelectric element portion 33 expand and contract in the Z-axis direction. Are alternately repeated to generate a flexural vibration in the X-axis direction in the stator 2.

Therefore, for example, when an AC voltage having a phase shifted by 90 degrees is applied from the drive circuit 5 to both the electrode plate 31c of the first piezoelectric element section 31 and the electrode plate 32c of the second piezoelectric element section 32, Y The axial flexural vibration and the vertical vibration in the Z-axis direction are combined to generate elliptical vibration in the YZ plane at the corner 7 of the stator 2 that is in contact with the rotor 8. Rotate around.
Similarly, when an AC voltage whose phase is shifted by 90 degrees is applied from the drive circuit 5 to both the electrode plate 32c of the second piezoelectric element portion 32 and the electrode plate 33c of the third piezoelectric element portion 33, the X axis Direction vibration and Z-axis longitudinal vibration are combined to generate elliptical vibration in the XZ plane at the corner 7 of the stator 2 that is in contact with the rotor 8, and the rotor 8 rotates about the Y-axis via frictional force. Rotate to.
Further, when an AC voltage having a phase shifted by 90 degrees is applied from the drive circuit 5 to both the electrode plate 31c of the first piezoelectric element portion 31 and the electrode plate 33c of the third piezoelectric element portion 33, the X-axis direction The flexural vibration in the Y-axis direction and the flexural vibration in the Y-axis direction combine to generate elliptical vibration in the XY plane at the corner 7 of the stator 2 that contacts the rotor 8, and the rotor 8 moves about the Z-axis through frictional force. Rotate.

  Therefore, by driving the vibration means 3, the flexural vibration in the Y-axis direction by the first piezoelectric element portion 31, the longitudinal vibration in the Z-axis direction by the second piezoelectric element portion 32, and the third piezoelectric element portion 33. By generating composite vibration combining two or all of the three flexural vibrations in the X-axis direction and forming elliptical vibrations at the corners 7 of the stator 2, the rotor 8 can be freely rotated in a three-dimensional direction. It is configured to be able to.

Next, the operation of the vibration actuator according to the first embodiment will be described.
When the vibration means 3 is not driven, as shown in FIG. 1, no voltage is applied from the drive circuit 5 to the electrode plate 11c of the deformation element 11, so that the piezoelectric element plates 11b and 11d of the deformation element 11 The original thickness remains the same, and the deformation element 11 has a predetermined thickness H0. At this time, the disc spring 10 is compressed to a predetermined length, and the urging force of the disc spring 10 causes the preload surface 13 of the preload member 12 to be pressed against the rotor 8 via the deforming element 11. Is pressurized to the stator 2 by the pre-pressure F0. Thereby, a high holding force between the rotor 8 and the stator 2 can be secured, and the rotation of the rotor 8 with respect to the stator 2 is prevented by this holding force.

  On the other hand, when the vibration means 3 is driven, as shown in FIG. 6, a predetermined negative DC voltage is applied to the electrode plate 11c of the deformation element 11, and the piezoelectric element plates 11b and 11d of the deformation element 11 are moved in the Z-axis direction. By contracting in the (thickness direction), the deformation element 11 has a thickness H1 that is smaller than the predetermined thickness H0. Along with this, the disc spring 10 extends beyond a predetermined length and its urging force becomes small, and the rotor 8 is pressed against the stator 2 with a pre-pressure F1 smaller than the pre-pressure F0. Therefore, it is possible to reduce wear caused at the contact portions of the rotor 8 and the stator 2 and the rotor 8 and the preloading member 12 as the rotor 8 rotates, and a long-life vibration actuator can be realized.

Therefore, it is possible to realize a vibration actuator having both a high holding force and a long life.
In addition, since the preload for pressing the rotor 8 against the stator 2 can be reduced simply by applying a negative voltage to the deformation element 11 from the drive circuit 5 to contract the deformation element 11, the disc spring 10 is different. The preload can be easily changed without changing to another disc spring having a spring constant.

  Here, in the vibration actuator according to the first embodiment, FIG. 7 shows the preload applied to the stator 2 of the rotor 8 when the negative voltage applied to the deformation element 11 is changed. As can be seen from FIG. 7, when the absolute value of the negative voltage applied to the deformation element 11 is increased, the preload of the rotor 8 with respect to the stator 2 decreases accordingly. That is, as the absolute value of the negative voltage increases, the amount of contraction of the deformation element 11 increases, and thereby the disc spring 10 extends and the preload decreases. Therefore, by changing the value of the DC voltage applied to the deformation element 11, it is possible to expand and contract the deformation element 11 to change the preload.

  In addition, although the deformation | transformation element 11 was arrange | positioned between the preload member 12 and the disc spring 10, you may arrange | position between the ceiling part 9a of the support member 9 and the disc spring 10 instead. Also in this case, the preload of the rotor 8 against the stator 2 can be reduced by applying a predetermined negative voltage to the deformation element 11 when the vibration means 3 is driven to contract the deformation element 11 in the thickness direction. The same effect as in the first embodiment can be obtained.

  Further, instead of disposing the deformation element 11 between the ceiling portion 9a of the support member 9 and the preload member 12 in this way, as shown in FIG. 8, the deformation element 11 is interposed between the lower end portion of the support member 9 and the stator 2. The deformation element 11 may be arranged. However, in this case, as shown in FIG. 9, when the vibrating means 3 is driven, a predetermined positive DC voltage is applied to the deformation element 11 so that the deformation element 11 has a thickness larger than a predetermined thickness H0. The preload of the rotor 8 against the stator 2 is reduced by extending the distance H2 and thereby increasing the distance from the upper surface of the stator 2 to the ceiling portion 9a of the support member 9 to reduce the biasing force of the disc spring 10. Can do.

  Instead of applying a preload between the preload member 12 and the stator 2 by the biasing force of the disc spring 10, the disc spring 10 is omitted and the support member 9 is made of an elastic body. Thus, it is possible to apply a preload between the preload member 12 and the stator 2 to pressurize the rotor 8 to the stator 2.

Embodiment 2. FIG.
In the vibration actuator of the first embodiment described above, the preload member 12 is supported by the support member 9 with respect to the stator 2. However, in this second embodiment, as shown in FIG. Is supported with respect to the base portion 23 by a plurality of support members 22 made of coiled tension springs. The base portion 23 has a larger diameter than the stator 2 and the vibration means 3, and has a portion that protrudes laterally from the outer peripheral surfaces of the stator 2 and the vibration means 3. The preload member 21 is supported by the support member 22 on the upper surface of the protruding portion of the base 23. The preload member 21 is pressed against the rotor 8 by the urging force of the support member 22, and a preload in the −Z-axis direction is applied to the rotor 8. Thereby, the rotor 8 is pressurized to the stator 2.

  Further, the vibration actuator according to the second embodiment has a deformation element 24 arranged so as to be superimposed on the first to third piezoelectric element portions 31 to 33 of the vibration means 3, and the connecting bolt 4 includes these The base 23 and the stator 2 are connected through the vibration means 3 and the deformation element 24. The deformation element 24 is electrically connected to the drive circuit 5 in the same manner as the first to third piezoelectric element portions 31 to 33.

  As shown in FIG. 11, the deformation element 24 has a structure in which an electrode plate 24a, a piezoelectric element plate 24b, an electrode plate 24c, a piezoelectric element plate 24d, and an electrode plate 24e are sequentially stacked, and a third piezoelectric element portion. 33 and the base portion 23, and is insulated from the third piezoelectric element portion 33 through the insulating sheet 37 and from the base portion 23 through the insulating sheet 25.

  The deformable element 24 has the same configuration as the deformable element 11 in the first embodiment described above except that a through hole for passing the connecting bolt 4 is formed in the center thereof, and the electrode plate 24a and 24 c and 24 e correspond to the electrode plates 11 a, 11 c and 11 e of the deformation element 11, and the piezoelectric element plates 24 b and 24 d correspond to the piezoelectric element plates 11 b and 11 d of the deformation element 11. That is, when a positive DC voltage is applied from the drive circuit 5 to the electrode plate 24c of the deformation element 24, the piezoelectric element plates 24b and 24d extend in the Z-axis direction (thickness direction), while a negative DC voltage is applied. The piezoelectric element plates 24b and 24d are configured to shrink in the Z-axis direction (thickness direction).

  When the vibration means 3 is not driven, as shown in FIG. 10, no voltage is applied to the electrode plate 24c of the deformation element 24. Therefore, the piezoelectric element plates 24b and 24d of the deformation element 24 have the original thickness. The deformation element 24 has a predetermined thickness H3. At this time, the preload member 21 presses the rotor 8 toward the stator 2 by the urging force of the support member 22, whereby the rotor 8 is pressed against the stator 2.

  On the other hand, when the vibration means 3 is driven, as shown in FIG. 12, a predetermined negative DC voltage is applied from the drive circuit 5 to the electrode plate 24c of the deformation element 24, and the piezoelectric element plates 24b and 24d of the deformation element 24 are By contracting in the Z-axis direction (thickness direction), the deformation element 24 has a thickness H4 smaller than the predetermined thickness H3. Thereby, the height from the upper surface of the base 23 to the rotor 8 is reduced, the urging force of the support member 22 is reduced, and the pre-pressure for pressurizing the rotor 8 to the stator 2 is reduced.

  Therefore, similarly to the above-described first embodiment, it is possible to realize a vibration actuator having a long life while ensuring a high holding force.

  Note that the deformation element 24 is arranged at the interface between the third piezoelectric element portion 33 and the base portion 23, but the deformation element 24 is not limited to this, and the third of the stator 2 and the vibration means 3 is not limited thereto. The deformation element 24 may be arranged at any of a plurality of interfaces existing between the piezoelectric element portions 33. Also in this case, the preload of the rotor 8 with respect to the stator 2 can be reduced by applying a predetermined negative voltage to the deformation element 24 when the vibration means 3 is driven to contract the deformation element 24 in the thickness direction.

  Further, instead of disposing the deformation element 24 between the base portion 23 and the stator 2 as described above, as shown in FIG. 13, the deformation element 24 is disposed between the base portion 23 and the lower end portions of the support members 22. May be. However, in this case, as shown in FIG. 14, when the vibration means 3 is driven, a predetermined positive DC voltage is applied to the deformation element 24 so that the deformation element 24 has a thickness larger than a predetermined thickness H3. By extending to H5 and thereby reducing the biasing force of the support member 22, the preload of the rotor 8 on the stator 2 can be reduced.

  Further, as shown in FIG. 15, a deformation element 24 may be arranged between the preload member 21 and the upper end portion of each support member 22. By applying this positive voltage and extending the deformation element 24 in the thickness direction, the preload of the rotor 8 against the stator 2 can be reduced.

  In the first and second embodiments described above, the deformation elements 11 and 24 may be arranged in the middle of the support members 9 and 22 in the length direction.

Embodiment 3 FIG.
Next, a vibration actuator according to Embodiment 3 of the present invention will be described with reference to FIG. In the third embodiment, the second piezoelectric element portion 32 is omitted from the first to third piezoelectric element portions 31 to 33 of the vibration unit 3 in the second embodiment, and the deformation element 24 is moved in the Z-axis direction. It is also used as a piezoelectric element portion that generates the longitudinal vibration. That is, here, the first piezoelectric element portion 31 that generates flexural vibration in the X-axis direction, the third piezoelectric element portion 33 that generates flexural vibration in the Y-axis direction, and the piezoelectric element portion that generates longitudinal vibration in the Z-axis direction. The vibrating element 26 is configured by the deforming element 24. At the time of driving the vibration means 26, the drive circuit 5 is driven by applying an AC voltage to at least two of the first and third piezoelectric element portions 31 and 33 and the deformation element 24, thereby contacting the rotor 8. An elliptical motion is generated in the corner portion 7 of the stator 2 so that the rotor 8 can be arbitrarily rotated around the three axes of X, Y, and Z.

  In the vibration actuator having such a configuration, when the vibration means 26 is not driven, no voltage is applied to the electrode plate 24c of the deformation element 24 as shown in FIG. The plates 24b and 24d remain at their original thickness, and the deformation element 24 has a predetermined thickness H3. Therefore, the preload member 21 presses the rotor 8 toward the stator 2 by the urging force of the support member 22, thereby pressing the rotor 8 against the stator 2.

On the other hand, when the vibration means 26 is driven, an AC voltage is applied from the drive circuit 5 to at least two of the first and third piezoelectric element portions 31 and 33 and the deformation element 24 as shown in FIG. As a result, the rotor 8 is rotationally driven. Here, the AC voltage applied from the drive circuit 5 to the deformation element 24 is offset in the minus direction by a predetermined voltage value. From the state where the thickness H4 is smaller than the thickness H3, the expansion and contraction are repeated in the Z-axis direction, and longitudinal vibration in the Z-axis direction is generated. Even when no AC voltage is applied to the deformation element 24, a predetermined negative DC voltage is applied from the drive circuit 5 to the deformation element 24, so that the deformation element 24 is contracted to a thickness H4.
That is, when the vibration unit 26 is driven, the height from the upper surface of the base 23 to the rotor 8 is reduced due to the deformation of the deformation element 24, thereby reducing the biasing force of the support member 22, thereby reducing the preload of the rotor 8 relative to the stator 2. Pressure is reduced.

Therefore, similarly to the above-described second embodiment, it is possible to realize a vibration actuator having a long life while ensuring a high holding force.
In addition, in the third embodiment, since the deformation element 24 is also used as a piezoelectric element portion that generates longitudinal vibration in the Z-axis direction, there is no need to provide a dedicated piezoelectric element portion that generates longitudinal vibration in the Z-axis direction. As a result, a vibration actuator having a simple structure can be realized.

  In the first to third embodiments described above, the pre-pressure during driving is reduced by applying a negative DC voltage to the deformation elements 11 and 24 only when the vibration means 3 and 26 are driven to contract the deformation elements 11 and 24. However, instead of applying a voltage to the deformation elements 11 and 24 when the vibration means 3 and 26 are driven, the deformation elements 11 and 24 are positive only when the vibration means 3 and 26 are stopped. Even if the preload when stopping driving is increased by applying a DC voltage to extend the deformation elements 11 and 24, it is possible to realize a vibration actuator having a long life while ensuring a high holding force.

In the first to third embodiments, the preload is increased by applying a positive DC voltage to the deformation elements 11 and 24 and extending the deformation elements 11 and 24 when the vibration means 3 and 26 are driven. High driving force.
Further, when the driving of the vibration means 3 and 26 is stopped, a negative DC voltage is applied to the deformation elements 11 and 24 to contract the deformation elements 11 and 24, thereby reducing the preload and reducing the holding force. .

Moreover, various other elastic bodies can be used in place of the disc spring 10 in the first embodiment and the coiled tension spring constituting the support member 22 in the second and third embodiments.
By using an elastic body having a high elastic modulus, it is possible to increase the amount of change in the preload when a DC voltage is applied to the deformation elements 11 and 24 to expand and contract.

  In the first embodiment, the rotor 8 is preloaded by the preload means including the disc spring 10 and the support member 9. In the second and third embodiments, the rotor 8 is preloaded by the preload means including the support member 22. However, the present invention is not limited to these, and various preloading means capable of applying a preload between the stator and the preload member and pressurizing the rotor to the stator can be used. Also in this case, the preload can be easily changed by configuring the preload means to include the deformation element and changing the preload by expanding and contracting the deformation element.

In the first to third embodiments, the deformation elements 11 and 24 have a pair of piezoelectric element plates 11b and 11d. However, the deformation elements 11 and 24 may have one or three or more piezoelectric element plates. In particular, if the deforming element is configured to have a large number of piezoelectric element plates, the amount of expansion and contraction when a DC voltage is applied to the deforming element increases, and the amount of change in preload can be increased. At this time, for example, a thin piezoelectric element plate can be used so that the thickness of the entire deformation element does not change.
In addition, various types of piezoelectric elements can be used instead of the plate-shaped piezoelectric elements.
Various deformation elements such as a heat deformation element can be used instead of the piezoelectric element.

Further, in each of the above-described embodiments, the contact between the stator 2 and the rotor 8 is the corner portion 7, but the present invention is not limited to this configuration. If the elliptical motion can be transmitted, the contact may be made on a flat surface, the contact may be made on a curved surface, or may not be annular.
Further, in each of the above embodiments, the elliptical motion is generated at the contact portion between the stator 2 and the rotor 8, but the circular motion may be generated by controlling the amplitude in each axial direction.

  In the first to third embodiments, the multi-degree-of-freedom vibration actuator has been described in which the rotor 8 is substantially spherical, and the stator 2 is vibrated by the vibration means 3 and 26 to rotate the rotor 8 around a plurality of axes. However, the present invention is not limited to this, and can also be applied to a one-degree-of-freedom vibration actuator that rotates a rotor about a single axis.

It is sectional drawing which shows the vibration actuator which concerns on Embodiment 1 of this invention. 3 is a partial cross-sectional view illustrating a configuration of a deformation element used in Embodiment 1. FIG. 3 is a perspective view showing a polarization direction of a pair of piezoelectric element plates of a deformation element used in Embodiment 1. FIG. 2 is a partial cross-sectional view showing a configuration of a vibration unit used in Embodiment 1. FIG. 3 is a perspective view showing polarization directions of three pairs of piezoelectric element plates of the vibration means used in Embodiment 1. FIG. FIG. 3 is a cross-sectional view showing when the vibration actuator according to the first embodiment is driven. It is sectional drawing which shows a mode when a voltage is applied to the deformation | transformation element in the vibration actuator of FIG. It is a graph which shows the relationship of the preload with respect to the change of the voltage applied to a deformation | transformation element. 6 is a cross-sectional view illustrating a vibration actuator according to a modification of the first embodiment. FIG. FIG. 6 is a cross-sectional view showing when the vibration actuator according to a modification of the first embodiment is driven. FIG. 6 is a cross-sectional view showing a vibration actuator according to a second embodiment. FIG. 6 is a partial cross-sectional view illustrating configurations of a vibration unit and a deformation element used in the second embodiment. FIG. 6 is a cross-sectional view showing when the vibration actuator according to the second embodiment is driven. 6 is a cross-sectional view showing a vibration actuator according to a modification of the second embodiment. FIG. FIG. 10 is a cross-sectional view showing when driving a vibration actuator according to a modification of the second embodiment. 10 is a cross-sectional view showing a vibration actuator according to another modification of the second embodiment. FIG. FIG. 6 is a cross-sectional view showing a vibration actuator according to a third embodiment. FIG. 10 is a cross-sectional view showing when the vibration actuator according to the third embodiment is driven.

Explanation of symbols

  1, 23 base, 2 stator, 3 vibration means, 4 connecting bolt, 5 drive circuit, 6 recess, 7 corner, 8 rotor, 9, 22 support member, 9a ceiling, 10 disc spring, 11, 24 deformation element, 11a, 11c, 11e, 24a, 24c, 24e, 31a, 31c, 31e, 32a, 32c, 32e, 33a, 33c, 33e Electrode plate, 11b, 11d, 31b, 31d, 32b, 32d, 33b, 33d Piezoelectric element plate , 12, 21 Preload member, 13 Preload surface, 14, 15, 25, 34 to 37 Insulating sheet, 31 First piezoelectric element section, 32 Second piezoelectric element section, 33 Third piezoelectric element section.

Claims (8)

A stator,
A preload member;
A rotor sandwiched between the stator and the preload member;
Preload means for applying a preload between the stator and the preload member to pressurize the rotor against the stator;
Vibration means for rotating the rotor by generating ultrasonic vibration in the stator, the preload means includes a deformation element, and the preload is changed by deforming the deformation element. Vibration actuator.   The vibration actuator according to claim 1, wherein the deformation element includes a piezoelectric element.   The vibration actuator according to claim 2, wherein the preload means includes a support member that supports the preload member with respect to the stator. A base for supporting the vibration means;
The vibration actuator according to claim 2, wherein the preload means includes a support member that supports the preload member with respect to the base.   The vibration actuator according to claim 3, wherein the deformation element is disposed between the preload member and the support member.   The vibration actuator according to claim 3, wherein the deformation element is disposed between the stator and the support member.   The vibration actuator according to claim 4, wherein the deformation element is disposed between the base and the support member.   The vibration according to claim 4, wherein the vibration unit includes a plurality of piezoelectric elements that generate vibrations in different directions, and the deformation element also serves as one of the plurality of piezoelectric elements of the vibration unit. Actuator.

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