JP2007135267A - Ultrasonic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sustain a stabilized torque even when deflection has occurred in contact between a rotor and a stator. <P>SOLUTION: In an ultrasonic motor where a rotor is driven by vibrating the oscillation piece of a stator touching the rotor by means of a piezoelectric element, each phase of the stator for generating a traveling wave is arranged on the inner circumference and the outer circumference of the piezoelectric element. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic motor, and more particularly to an ultrasonic motor that drives a rotor by vibrating a vibrating piece of a stator in contact with the rotor.

  2. Description of the Related Art Conventionally, an ultrasonic motor that can drive a rotor in contact with a stator by vibration of a piezoelectric element on the stator side without using magnetic force has been developed.

  Ultrasonic motors can be used for various purposes by devising the number of stators and the shape of the rotor. For example, disk-type and ring-type rotors are already well known. Recently, development of a spherical ultrasonic motor having a rotor as a sphere has also been advanced.

  A stator of such an ultrasonic motor is formed by, for example, polarizing a predetermined portion of a flat plate-shaped piezoelectric element in a predetermined direction to form an A phase and a B phase as piezoelectric element members. A predetermined voltage is applied to the drive electrode provided for each phase to generate a traveling wave vibration on the elastic vibrating piece on the piezoelectric element member. The rotor in contact with the stator is driven by the vibration of this vibrating piece.

  Patent Document 1 and Patent Document 2 disclose a polarization structure of a piezoelectric element member of a conventional ultrasonic motor. This structure will be described below with reference to FIG.

  FIG. 8 is a diagram showing the structure of a piezoelectric element member of a conventional ultrasonic motor, (a) is a perspective view of the piezoelectric element member of a conventional ultrasonic motor, and (b) is a dotted line. It is the perspective view seen from the back, rotated with the axis | shaft YY shown, (c) is a partially broken perspective view which fractures | ruptures and shows a part of (a).

  As shown in FIG. 8A, FIG. 8B, and FIG. 8C, the piezoelectric element member 131 of the conventional ultrasonic motor includes a flat plate-shaped piezoelectric element 136 and a predetermined one of the piezoelectric elements 136. An individual electrode 134 for causing the piezoelectric element piece to be polarized in a predetermined direction for the A phase, and an individual electrode for causing a predetermined piezoelectric element piece of the piezoelectric element 136 to be polarized in the predetermined direction for the B phase. 135, a drive electrode 138 for driving the A-phase piezoelectric element piece, a drive electrode 137 for driving the B-phase piezoelectric element piece, and a predetermined piezoelectric element piece among the piezoelectric elements 136 for vibration detection. Individual electrodes 150 for polarization in a predetermined direction, vibration detection electrodes 151 for detecting potentials generated by the piezoelectric element pieces below the individual electrodes 150 due to vibrations of the piezoelectric elements 136, and A-phase drive electrodes 138 To apply voltage to The wiring 140, the wiring 141 for applying a voltage to the driving electrode 137 of the B-phase, and a wiring 142 for detecting potential from the vibration detecting electrodes 151.

  As shown in FIGS. 8A to 8C, in the piezoelectric element member 131 of the conventional ultrasonic motor, a part of the circumferential direction of the plate-shaped annular piezoelectric element 136 is the A phase, and the other in the circumferential direction. A part is the B phase, and the A phase and the B phase are driven with the phases shifted in time to generate a traveling wave of vibration.

JP-A-5-56670 Japanese Patent Publication No. 1-17354

  However, the above-described prior art has the following problems.

  That is, in the conventional example as shown in FIGS. 8A to 8C, the A phase and the B phase divided in the circumferential direction in order to generate traveling waves are driven with the phases shifted in time. At the time of phase driving, the counter electrode side is in a free state, vibration unevenness is likely to occur on the circumference, stable torque is not generated, and in extreme cases, the rotor cannot be driven.

  Further, when the contact state between the rotor and the stator is not uniform due to disturbance or the like, there is a problem that a stable traveling wave is not formed and torque variation occurs.

  The present invention has been made in view of the above points. In an ultrasonic motor that moves a rotor by vibrating a vibrating piece of a stator in contact with the rotor by a piezoelectric element, contact between the rotor and the stator is biased. It is another object of the present invention to maintain a stable torque.

  The present invention relates to an ultrasonic motor that drives a rotor by vibrating a vibrating piece of a stator in contact with a rotor by a piezoelectric element, and each phase for generating a traveling wave of the stator is divided into an inner circumference and an outer circumference of the piezoelectric element. It is characterized by having been arranged in.

  The present invention is also characterized in that, in the invention described in claim 1, the piezoelectric element has a flat plate shape.

  In the invention according to claim 1, the rotor is a sphere.

  According to the present invention, in an ultrasonic motor that moves a rotor by vibrating a vibrating piece of a stator that is in contact with the rotor by a piezoelectric element, a stable torque is maintained even when the contact between the rotor and the stator is biased. be able to.

  In addition, the present invention is structurally resistant to vibration unevenness, forms a stable traveling wave regardless of the contact state between the rotor and the stator, and can generate a stable torque.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view schematically showing a spherical ultrasonic motor according to an embodiment of the present invention.

  In the present embodiment, a case of a spherical ultrasonic motor having a spherical rotor is described. However, in the ultrasonic motor according to the present invention, a flat rotor can be used regardless of the shape of the rotor.

  As shown in FIG. 1, the ultrasonic motor 1 according to the present embodiment rotates a spherical rotor 2 while being held by three stators 3 a, 3 b and 3 c provided on a frame member 4. 2 are provided on the surfaces of the stators 3a, 3b, and 3c that come into contact with the rotor 2, and the vibrating pieces 33 vibrate to generate traveling waves, whereby the rotor 2 rotates. Be made.

  FIG. 2 is a plan view of the stator 3b shown in FIG.

  As shown in FIG. 2, a large number of vibrating pieces 33 are provided on the surface of the stator 3 b that presses against the rotor 2 along the circumference of the stator 3 b. A piezoelectric element member 31 shown later in FIG. 3 is provided below these vibrating pieces 33, and the piezoelectric elements of the piezoelectric element members expand and contract by applying a voltage to vibrate the vibrating piece 33. In the ultrasonic motor 1, the rotor 2 can be rotated in an arbitrary direction by controlling this vibration.

  In the present embodiment, the structures of the stators 3a, 3b, and 3c are the same. Therefore, the stator 3b will be described below as a representative.

  3 is an exploded perspective view showing the stator 3b shown in FIG. 2 disassembled into an elastic body 30 and a piezoelectric element member 31. As shown in FIG.

  As shown in FIG. 3, the stator 3 b includes an elastic body 30 and a piezoelectric element member 31.

  As shown in FIG. 2, a large number of vibration pieces 33 are provided on the surface of the elastic body 30.

  The piezoelectric element member 31 includes a flat plate-shaped piezoelectric element 36, an individual electrode 34 for polarizing a predetermined piezoelectric element piece of the piezoelectric element 36 in a predetermined direction for the A phase, and a piezoelectric element 36. Individual electrodes 35 for causing the predetermined piezoelectric element pieces to be polarized in a predetermined direction for the B phase, drive electrodes 38 for driving the A phase piezoelectric element pieces, and driving the B phase piezoelectric element pieces. Drive electrode 37, wiring 40 for applying a voltage to the A-phase driving electrode 38, and wiring 41 for applying a voltage to the B-phase driving electrode 37.

  The individual electrode 34, the individual electrode 35, the drive electrode 37, and the drive electrode 38 are, for example, silver electrodes, and the wiring 40 and the wiring 41 are respectively connected to the driving electrode 38 and the wiring 41 to the driving electrode 37 by soldering, for example. Connected to.

  4A and 4B are views showing the structure of the piezoelectric element member 31 of the stator 3b shown in FIG. 3, wherein FIG. 4A is a perspective view of the piezoelectric element member 31, and FIG. 4B is a dotted line. It is the perspective view which rotated with the axis | shaft XX and was seen from the back, (c) is a partially broken perspective view which fractures | ruptures and shows a part of (a).

  As shown in FIG. 4A, FIG. 4B, and FIG. 4C, in the piezoelectric element member 31 of the ultrasonic motor 1 of the present embodiment, the inner side of the circumference of the plate-shaped annular piezoelectric element 36 A portion is the A phase, and the outer portion of the circumference is the B phase, and the A phase and the B phase are driven with the phases shifted in time to generate a traveling wave of vibration.

  In the piezoelectric element member 31 in the present embodiment, the A-phase and B-phase piezoelectric element pieces are formed over the entire circumference in the circumferential direction of the piezoelectric element 36, but the present invention is limited to this. The structure may be such that the A phase and the B phase are not formed in a portion in the circumferential direction.

  In the present embodiment, the surface of the piezoelectric element member 31 on which the individual electrode 34 and the individual electrode 35 are provided is in contact with the elastic body 30 as shown in FIG. 3, but the present invention is not limited to this. Instead, the surface of the piezoelectric element member 31 on which the drive electrode 37 and the drive electrode 38 are provided may be in contact with the elastic body 30.

  In the present embodiment, the drive electrode 37 and the drive electrode 38 are provided on the piezoelectric element member 31 as shown in FIG. 4B. However, the present invention is not limited to this, and FIG. One electrode that extends over both the region of the drive electrode 37 and the region of the drive electrode 38 in (b) may be provided.

  5A and 5B are diagrams showing the polarization direction of the piezoelectric element member, FIG. 5A is a plan view showing the polarization direction of the piezoelectric element member 31 of the present embodiment shown in FIG. 4A, and FIG. It is a top view which shows the polarization direction of the piezoelectric element member 131 of the prior art example shown to Fig.8 (a).

  As shown in FIG. 5A, in the piezoelectric element member 31 of the present embodiment, the inner part of the circumference is the A phase, and the piezoelectric element pieces whose polarization directions are opposite in the A phase are alternately arranged. In addition, the outer peripheral portion of the circumference is a B phase, and piezoelectric element pieces whose polarization directions are reversed in the B phase are alternately set to have an angle of 36 °. Is provided. Further, as shown in FIG. 5A, the A phase and the B phase are configured to be shifted by 18 °.

  On the other hand, as shown in FIG. 5B, in the piezoelectric element member 131 of the conventional example, the left side portion in the circumferential direction is the A phase, and the piezoelectric element pieces whose polarization directions are opposite in the A phase are alternately arranged. For example, it is provided with an angle of 36 °, and the right side portion in the circumferential direction is the B phase, and the piezoelectric element pieces whose polarization directions are reversed in the B phase are alternately set at an angle of, for example, 36 °. Is provided. Further, as shown in FIG. 5B, the A phase and the B phase are configured to be shifted by 18 °, for example.

  As can be seen by comparing FIG. 5 (a) and FIG. 5 (b), in the present embodiment, each phase of the piezoelectric element is arranged in a double ring shape between the inner side and the outer side. Since the entire circumference of the stator is vibrated, a standing wave of each phase is generated uniformly, and a stable traveling wave without loss can be generated.

  FIG. 6 is a diagram showing experimental values of the impedance characteristics of the stator, (a) is a diagram showing the impedance characteristics of the stator 3b of the present embodiment shown in FIG. 2, and (b) is a diagram of FIG. 8 (a). It is a figure which shows the impedance characteristic of the stator using the piezoelectric element member 131 of the prior art example shown in FIG.

  According to the stator 3b of the present embodiment, as shown in FIG. 6A, a large resonance is shown in a certain frequency range. On the other hand, in the stator using the piezoelectric element member 131 of the conventional example, as shown in FIG. 6 (b), resonance is shown in a plurality of frequency ranges, and each is smaller than the present embodiment. is there. For this reason, according to this Embodiment, the ultrasonic motor more efficient than before can be provided.

  FIG. 7 is a diagram showing experimental values of the relationship between the force pressing the stator of the ultrasonic motor against the rotor and the torque of the ultrasonic motor.

  As shown in FIG. 7, both the ultrasonic motor of the present embodiment and the conventional ultrasonic motor increase the torque as the pressing force increases, but the ultrasonic motor of the present embodiment has a higher torque. Can be generated.

  In the above-described embodiment, an annular piezoelectric element is used as a stator. However, the present invention is not limited to this, and for example, an elliptical annular element may be used, and a traveling wave path may be looped. Any shape can be used.

  In the present embodiment, the rotor is driven in contact with the entire circumference of the traveling wave path of the stator at the same time. However, the present invention is not limited to this. When the rotor is mounted on a part of the traveling wave path and the rotor is moved along a loop of the traveling wave path (for example, when the vehicle moves on the rail, the vehicle is used as the rotor and the rail is The present invention can be applied to a traveling wave path of a stator.

1 is a perspective view schematically showing a spherical ultrasonic motor according to an embodiment of the present invention. FIG. 2 is a plan view of a stator 3b shown in FIG. FIG. 3 is an exploded perspective view showing a stator 3b shown in FIG. 2 in an exploded manner with an elastic body 30 and a piezoelectric element member 31. It is a figure which shows the structure of the piezoelectric element member 31 of the stator 3b shown in FIG. 3, (a) is a perspective view of the piezoelectric element member 31, (b) is an axis | shaft which shows (a) there with a dashed-dotted line there It is the perspective view rotated and seen from the back, (c) is a partially broken perspective view which fractures | ruptures and shows a part of (a). It is a figure which shows the polarization direction of a piezoelectric element member, (a) is a top view which shows the polarization direction of the piezoelectric element member 31 of this Embodiment shown to Fig.4 (a), (b) is FIG. It is a top view which shows the polarization direction of the piezoelectric element member 131 of the prior art example shown to a). It is a figure which shows the experimental value of the impedance characteristic of a stator, (a) is a figure which shows the impedance characteristic of the stator 3b of this Embodiment shown in FIG. 2, (b) was shown in FIG. 8 (a). It is a figure which shows the impedance characteristic of the stator using the piezoelectric element member 131 of the prior art example. It is a figure which shows the experimental value of the relationship between the force which presses the stator of an ultrasonic motor to a rotor, and the torque of the ultrasonic motor. It is a figure which shows the structure of the piezoelectric element member of the conventional ultrasonic motor, (a) is a perspective view of the piezoelectric element member of the conventional ultrasonic motor, (b) shows (a) there with a dashed-dotted line there It is the perspective view which rotated with the axis | shaft and was seen from the back, (c) is a partially broken perspective view which fractures | ruptures and shows a part of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultrasonic motor 2 Rotor 3a, 3b, 3c Stator 4 Frame member 33 Vibrating piece 34, 35 Fixed electrode 36 Piezoelectric element 37, 38 Drive electrode 40, 41 Wiring

Claims (3)

In an ultrasonic motor that drives a rotor by vibrating a vibrating piece of a stator in contact with the rotor by a piezoelectric element,
An ultrasonic motor characterized in that each phase for generating a traveling wave of the stator is arranged on an inner periphery and an outer periphery of the piezoelectric element.   The ultrasonic motor according to claim 1, wherein the piezoelectric element has a flat plate shape.   The ultrasonic motor according to claim 1, wherein the rotor is a sphere.

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