JP2008199696A - Vibration actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small vibration actuator having a simple configuration. <P>SOLUTION: A hemispherical shell-like rotor 8 is rotatably disposed so as to contact on a corner portion 7 of a stator 2, and a pre-pressuring portion 12 is supported so as to be hung down on the stator 2 by a supporting member 11. The pre-pressurizing portion 12 is inserted into the inside of the rotor 8, and abuts on an internal surface 9 of the rotor 8 by its tip member 13. The tip member 13 press-fits on the internal surface of the rotor 8 by a spring S housed in the pre-pressurizing portion 12, thereby pressurizing the rotor 8 onto the stator 2. A vibration means 3 is driven, thereby enabling the rotor 8 to rotate around each of multiple shafts. <P>COPYRIGHT: (C)2008,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.

  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 pair of springs are disposed outside the stator and the hemispherical rotor, and the rotor is pressed against the stator by the pair of springs and 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.
A pair of connecting plates are drawn outward from the rotor, respectively, and a pair of fixing plates are drawn outward from the base member of the stator, and a pair of connecting plates are respectively provided between the pair of connecting plates and the pair of fixing plates. The rotor is pressurized against the stator by arranging the springs and pulling the pair of connecting plates against the pair of fixed plates.

JP 2004-357395 A

However, the vibration actuator of Patent Document 1 has a problem in that the entire vibration actuator is increased in size because a pair of springs for pressing the rotor against the stator are disposed outside the rotor and the stator.
In addition, a pair of connecting plates for connecting between one end of the pair of springs and the rotor, and a pair of fixing plates for connecting the other end of the pair of springs and the base member of the stator are required. There is a complicated configuration.
The present invention has been made to solve such problems, and an object thereof is to provide a vibration actuator that is small in size and has a simple configuration.

  The vibration actuator according to the present invention includes a stator, a rotor having a shell shape and arranged in contact with the stator on the outer surface thereof, preload means for pressurizing the rotor against the stator, and generating ultrasonic vibration in the stator. And a preload means for abutting the inner surface of the rotor on a predetermined line of action with respect to the stator regardless of the rotation of the rotor and pressurizing the rotor against the stator along the line of action. It is what has.

Preferably, the rotor is formed in a spherical shell shape having spherical surfaces on its inner and outer surfaces.
Moreover, it is preferable that a preload part has a spherical member which can rotate around a multi-axis and contacts the inner surface of a rotor.

The preloading means may be configured to have a rotational position sensor that is disposed in the vicinity of the preloading portion and that contacts the inner surface of the rotor and detects the rotational position of the rotor by rotating as the rotor rotates.
Moreover, you may comprise so that an ultrasonic vibration may be generated also in a preload part by a vibration means.
Further, the rotor can be formed to have a uniform thickness.

  According to the present invention, a vibration actuator having a small size and a simple configuration 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 block 1 and the stator 2, and the base block 1 and the stator 2 are connected to each other via a connecting bolt 4 passed through the vibration means 3. The vibration actuator as a whole has a substantially cylindrical outer shape. Here, for convenience of explanation, the central axis of the cylindrical outer shape from the base block 1 to the stator 2 is defined as the Z axis, and the X axis is perpendicular to the Z axis and the Z axis and the X axis are Assume that the Y-axis extends vertically.
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.

  A recess 6 is formed on the upper surface of the stator 2, that is, on the surface opposite to the surface in contact with the vibration means 3 of the stator 2. An annular corner 7 positioned on the XY plane is formed at the peripheral edge of the opening end of the recess 6, and a rotor 8 as a rotating body is rotatably contacted with the corner 7. The rotor 8 has a hemispherical shell shape shown in FIG. 2, and has a concave spherical surface on the inner surface 9 and a convex spherical surface on the outer surface 10. The rotor 8 has a diameter larger than the inner diameter of the concave portion 6 of the stator 2, and is disposed so as to be in contact with the corner portion 7 of the stator 2 at its outer surface 10.

  On the top of the stator 2, a support member 11 is disposed above the rotor 8 in an arch shape. The support member 11 is fixed to the upper surface of the stator 2 at its lower end. A preloading portion 12 having a length larger than the radius of the rotor 8 is suspended and supported substantially at the center of the support member 11, and the preloading portion 12 is inserted into the rotor 8 and provided at the tip thereof. The tip member 13 is in contact with the inner surface 9 of the rotor 8. Here, the preload portion 12 is located on a predetermined line of action L with respect to the stator 2, and the tip member 13 is in contact with the inner surface of the rotor 8 on the line of action L. Here, the action line L is preferably parallel to the Z axis. A spring S is accommodated in the preloading portion 12, and the tip member 13 is pressed against the inner surface 9 of the rotor 8 by the spring S, thereby applying a pressure force in the −Z-axis direction to the rotor 8. Therefore, the preload portion 12 pressurizes the rotor 8 against the stator 2 along the action line L.

The rotor 8 is formed so as to have a uniform thickness. Further, the action line L is positioned so as to coincide with the central axis of the cylindrical outer shape extending from the base block 1 toward the stator 2, and the tip member 13 of the preload portion 12 is substantially at the center of the concave portion 6 of the stator 2. It arrange | positions so that it may oppose. Even if the rotor 8 rotates, the tip member 13 of the preload portion 12 is configured to abut against the inner surface 9 of the rotor 8 at a fixed position that does not change with respect to the stator 2 and pressurize the rotor 8 against the stator 2. Yes.
Further, the preload portion 12 and the support member 11 constitute the preload means of the present invention.

  As shown in FIG. 3, the first piezoelectric element section 31 has a structure in which 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 are sequentially stacked. have. 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 block 1 through insulating sheets 34 to 37 and from each other.

As shown in FIG. 4, 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.

Next, the operation of the vibration actuator according to the first embodiment will be described.
First, when an alternating 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 element plates of the first piezoelectric element portion 31. The two divided portions 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.

By driving the vibration means 3 in this way, the rotor 8 can be rotated around the three axes of X, Y, and Z, respectively.
In this vibration actuator, the preload portion 12 incorporating the spring S is supported on the stator 2 by the support member 11, and the preload portion 12 is inserted into the hemispherical rotor 8 and the tip member 13 of the rotor 8 Since the rotor 8 is pressed against the stator 2 by directly pressing the inner surface 9, the rotor is added to the stator by a pair of springs arranged outside the rotor and the stator, as in a conventional vibration actuator. As compared with the case of pressing, a vibration actuator having a small size and a simple configuration can be realized.

  The tip member 13 of the preload portion 12 is positioned on a predetermined line of action L against the stator 2 regardless of the rotation of the rotor 8 and presses the inner surface 9 of the rotor 8, and the rotor 8 has a uniform thickness. Therefore, even if the rotor 8 rotates as shown in FIG. 5, the tip member 13 adds the rotor 8 toward the stator 2 without changing the height of the tip member 13 in the longitudinal direction of the preload portion 12. It will be pressed. Therefore, the preloading portion 12 can always press the rotor 8 against the stator 2 with a uniform force regardless of the rotation of the rotor 8.

Further, since the rotor 8 having a hemispherical shell shape is used, the rotor can be reduced in weight as compared with the case where a spherical rotor is used, and the inner surface 9 of the rotor 8 is pressed by the preload portion 12. 8 can be stably pressed against the stator 2.
Further, even if the pressing force is set to be large, there is no fitting between the preloading portion 12 and the rotor 8, so that the pressing force can be increased and high torque rotation can be realized.

Note that if the vibration means 3 is driven so that elliptical vibration is also generated in the tip member 13 of the preload portion 12 via the support member 11 in the same manner as the stator 2, the rotor 8 is pressurized against the stator 2. It is possible to reduce the friction loss necessary for the process.
Further, if the tip member 13 of the preload portion 12 is vibrated in the same vibration mode as that of the stator 2 and the tip member 13 generates a driving force in the same direction as the stator 2, both the stator 2 and the preload portion 12. Thus, the rotational force is transmitted to the rotor 8 and can be rotated with high torque.

Embodiment 2. FIG.
Next, a vibration actuator according to Embodiment 2 of the present invention will be described with reference to FIG. In the second embodiment, in the vibration actuator according to the first embodiment shown in FIG. 1, a preload portion 22 having a spherical member 21 that can rotate around multiple axes is used instead of the preload portion 12. It is. The preload portion 22 is supported in a drooping manner substantially at the center of the support member 11, and the spherical member 21 is disposed so as to contact the inner surface 9 of the rotor 8. In addition, the spherical member 21 is pressed against the inner surface 9 of the rotor 8 by the spring S accommodated in the preload portion 22, and the rotor 8 is pressed against the stator 2.

Even with this configuration, a vibration actuator having a small size and a simple configuration can be realized as in the first embodiment.
In addition, in the second embodiment, the spherical member 21 of the preload portion 22 is rotated following the rotational movement of the rotor 8, so that it is possible to reduce the friction loss accompanying the rotation of the rotor 8.

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 vibration actuator of the first embodiment shown in FIG. 1 is provided with a rotational position sensor 23 that is composed of an encoder or the like and detects the rotational position of the rotor 8 in the vicinity of the preload portion 12. is there. The rotational position sensor 23 includes a rotating member 24 that is connected to an intermediate portion in the longitudinal direction of the preload portion 12 and rotates with the rotor 8 while contacting the inner surface 9 of the rotor 8. Here, the rotating member 24 is disposed so as to be rotatable around the X axis.

  With this configuration, when the rotor 8 rotates about the X axis, the rotation member 24 rotates following the rotation of the rotor 8, so that the rotation position sensor 23 rotates the rotor 8 about the X axis. The position can be detected.

Similarly, if another rotating position sensor is provided in which the rotating member is rotatably arranged around the Y axis, the rotating position of the rotor 8 around the X axis and the Y axis can be detected.
It is also possible to detect the rotational position of the rotor 8 by marking the end portion of the hemispherical rotor-shaped rotor 8 located at the equator portion, photographing the end portion of the rotor 8 with a camera, and performing image processing.

  In the second embodiment as well, the rotational position of the rotor 8 can be detected by providing such a rotational position sensor 23.

Embodiment 4 FIG.
Next, a vibration actuator according to Embodiment 4 of the present invention will be described with reference to FIG. In the fourth embodiment, the rotor 25 having a non-uniform thickness distribution is used in place of the rotor 8 having a uniform thickness in the vibration actuator of the first embodiment shown in FIG. The rotor 25 is formed to have a thickness that increases from the center to the end.

As shown in FIG. 9, when the rotor 25 rotates, the preloading portion 12 remains positioned on the predetermined line of action L with respect to the stator 2, but according to the change in the thickness of the rotor 25, By changing the height of the tip member 13 in the longitudinal direction, the force with which the spring S accommodated in the preload portion 12 presses the tip member 13 against the inner surface 26 of the rotor 25 also changes, and according to the rotation of the rotor 25. The pressure applied to the stator 2 by the rotor 25 can be changed.
Here, since the rotor 25 has a larger thickness at the end portion, the position where the tip member 13 of the preload portion 12 contacts the inner surface 26 of the rotor 25 moves to the end portion side of the rotor 25 as the rotor 25 rotates. As the force increases, the force by which the preloading portion 12 presses the rotor 25 against the stator 2 is increased, so that high-torque rotation can be realized and the holding torque at rest can be increased.

Instead of the rotor 25 described above, a rotor formed so as to have a thickness that decreases as it approaches the end from the center thereof can be used.
In the second and third embodiments described above, the rotor 25 having a non-uniform thickness distribution can be used instead of the rotor 8.

Embodiment 5. FIG.
In the vibration actuator of the first embodiment described above, a plurality of preload portions 12 can be used. For example, as shown in FIG. 10, three preloading portions 12 can be used, and these three preloading portions 12 are supported by hanging substantially at the center of the support member 11, and each abuts the rotor 8 to contact the rotor. 8 is pressed against the stator 2. Even with this configuration, the same effect as in the first embodiment can be obtained.

In the third and fourth embodiments as well, the rotors 8 and 25 can be pressed against the stator 2 using the plurality of preloading portions 12.
Further, instead of using the preloading portion 12, a plurality of preloading portions having a spherical member that can be rotated around multiple axes at the tip thereof as shown in the second embodiment can be used.

Embodiment 6 FIG.
In the vibration actuator according to the first embodiment described above, instead of the hemispherical shell-shaped rotor 8, as shown in FIG. 11, a rotor 27 having a shell shape formed of a part of a cylinder may be used. The rotor 27 is pressurized against the stator 2 by the preload portion 12 and can be rotated around one axis.

  Similarly, a rotor having a shell shape formed of a part of a cylinder can be applied to the above-described second to fifth embodiments.

  In each of the first to sixth embodiments, the preload portions 12 and 22 may be supported by members independent from the vibration system including the base block 1, the stator 2, and the vibration means 3.

  In addition, in each said embodiment, instead of the spring S, various other elastic bodies can also be used.

If the tip member 13 of the preloading portion 12 and the spherical member 21 of the preloading portion 22 are each made of a low friction material such as Teflon (registered trademark), the rotors 8, 25, 27 are pressed against the stator 2. Necessary friction loss can be reduced.
Further, if the corner portion 7 of the stator 2 that is in contact with the outer surfaces of the rotors 8, 25, 27 is also made of such a low friction material, the friction loss can be further reduced.

In the first to sixth embodiments, the phase of the AC voltage applied from the drive circuit 5 to each piezoelectric element portion is shifted by 90 degrees. However, the phase is not limited to 90 degrees and may be changed. Moreover, you may change the voltage value of the alternating voltage to apply. The elliptical vibration generated in the stator 2 can be controlled by variously controlling the AC voltage.
Further, the contact between the stator 2 and the rotors 8, 25, 27 is the corner portion 7, but it 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 the above embodiment, instead of the longitudinal vibration in the Z-axis direction and the flexural vibration in the Y-axis direction or the X-axis direction, a composite vibration combining a plurality of vibrations that are not orthogonal to each other is generated to generate the rotors 8, 25, 27 can also be rotated.
Further, in the above-described embodiment, the flexural vibration in the X-axis direction, the flexural vibration in the Y-axis direction, and the vertical vibration in the Z-axis direction are generated in separate piezoelectric element units, and the combined vibration is generated by combining the vibrations. However, a single piezoelectric element portion may be polarized into a plurality of pieces, and the voltage applied to each polarization electrode may be individually controlled. That is, a composite vibration may be generated by a single piezoelectric element portion by applying a voltage obtained by synthesizing alternating voltages having different phases and amplitudes to each polarization electrode.
In each of the above embodiments, the elliptical motion is generated at the contact portion between the stator 2 and the rotors 8, 25, 27. However, the circular motion may be generated by controlling the amplitude in each axial direction. .

It is sectional drawing which shows the vibration actuator which concerns on Embodiment 1 of this invention. FIG. 3 is a perspective view showing a rotor in the first embodiment. 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 the polarization directions of three pairs of piezoelectric element plates of the piezoelectric element means used in Embodiment 1. FIG. FIG. 3 is a cross-sectional view showing an operation state of the vibration actuator according to the first embodiment. FIG. 6 is a cross-sectional view showing a vibration actuator according to a second embodiment. FIG. 6 is a cross-sectional view showing a vibration actuator according to a third embodiment. FIG. 6 is a cross-sectional view showing a vibration actuator according to a fourth embodiment. FIG. 10 is a cross-sectional view showing an operating state of the vibration actuator according to the fourth embodiment. It is a perspective view which shows the preload part and rotor in Embodiment 5. FIG. It is a perspective view which shows the preload part and rotor in Embodiment 6. FIG.

Explanation of symbols

  1 base block, 2 stator, 3 vibration means, 4 connecting bolt, 5 drive circuit, 6 recess, 7 corner, 8, 25, 27 rotor, 9, 26 inner surface, 10 outer surface, 11 support member, 12, 22 preloading portion , 13 Tip member, 21 Spherical member, 23 Rotation position sensor, 24 Rotation member, 31 First piezoelectric element part, 32 Second piezoelectric element part, 33 Third piezoelectric element part, 31a, 31c, 31e, 32a, 32c, 32e, 33a, 33c, 33e Electrode plate, 31b, 31d, 32b, 32d, 33b, 33d Piezoelectric element plate, L action line, S spring.

Claims (6)

A stator,
A rotor having a shell shape and arranged in contact with the stator on the outer surface thereof;
Preloading means for pressurizing the rotor against the stator;
Vibration means for rotating the rotor by generating ultrasonic vibrations in the stator, and the preload means is applied to the inner surface of the rotor on a predetermined line of action with respect to the stator regardless of the rotation of the rotor. A vibration actuator comprising a preload portion that contacts and pressurizes the rotor against the stator along the line of action.   The vibration actuator according to claim 1, wherein the rotor is formed in a spherical shell shape having spherical surfaces on an inner surface and an outer surface thereof.   3. The vibration actuator according to claim 1, wherein the preload portion includes a spherical member that is rotatable about multiple axes and that contacts the inner surface of the rotor.   The said preload means has a rotation position sensor which detects the rotation position of the said rotor by arrange | positioning in the vicinity of the said preload part, contacting the inner surface of the said rotor, and rotating with the rotation of the said rotor. The vibration actuator according to any one of the above.   The vibration actuator according to any one of claims 1 to 4, wherein the vibration means generates ultrasonic vibration also in the preload portion.   The vibration actuator according to claim 1, wherein the rotor has a uniform thickness.

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