JPH0646869B2 - Linear elastic wave motor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an acoustic wave motor in which a driving force is obtained by vibrating a piezoelectric element.

SUMMARY OF THE INVENTION The present invention provides at least one electrode on one surface of an inner peripheral surface and an outer peripheral surface of a cylindrical piezoelectric element, and a plurality of electrodes on the other surface. By applying a plurality of phases of alternating voltage to the electrode of, the member is pressed against a part of the outer peripheral surface of the vibrating unit configured to generate an elastic wave traveling in the circumferential direction. Is a linear elastic wave motor in which and are relatively moved. According to this motor, a uniform traveling wave can be generated, and the structure is simple and miniaturization can be achieved.

[Conventional technology]

By the applicant, Japanese Patent Application Nos. 58-21206 and 5
No. 8-150072 and the like propose an elastic wave motor in which a vibration force of a piezoelectric element is utilized to obtain a rotational force. This acoustic wave motor has a plurality of piezoelectric elements arranged on one surface perpendicular to the axial direction of the ring-shaped elastic body,
A ring-shaped or disk-shaped rotating body is pressed against the opposite surface, the plurality of piezoelectric elements are divided into two groups, and a driving voltage having a phase difference of 90 ° is applied to each group of piezoelectric elements. Thus, an elastic wave traveling in the circumferential direction is generated in the ring-shaped elastic body, and the elastic body is driven to rotate by the elastic wave.

In such an elastic wave motor, a linear elastic wave motor is realized by forming the ring-shaped elastic body into an elliptical shape having a straight line portion and pressing the moving body against the straight line portion.

Further, as a linear elastic wave motor having a simple structure, for example, a moving body is pressed against a rod-shaped body having an end portion and a traveling wave is generated in the rod-shaped body, whereby the moving body can be linearly moved. Conceivable.

As an elastic wave motor according to the present invention, Japanese Patent Application No. 60-
No. 162275 has been proposed.

[Problems to be solved by the invention]

In the case where the ring-shaped elastic body is formed in an elliptical shape, the curvature greatly changes between the straight line portion and the semicircular portion of the elliptical elastic body, and therefore the shape of the wave generated in both portions is different. Waves are scattered and reflected, and a uniform traveling wave cannot be obtained.

Further, in the case of using the rod-shaped body, a wave is reflected at the end of the rod-shaped body, and a standing wave is generated by the reflected wave and the traveling wave. Therefore, a mechanism for preventing the reflection of waves is required, and the structure of the motor is complicated and large.

In addition, in the case of using the above elliptical elastic body and the case of using the above rod-shaped body, the distance from the semi-circular portion changes in the case of the elliptical elastic body in accordance with the movement of the moving body. Vary in distance from the edge. That is, since the distance from the portion where the moving body is in pressure contact changes, the influence on the wave changes, and it is very difficult for the moving body to always receive a constant traveling wave.

[Means for solving problems]

In the present invention, at least one electrode is provided on one surface of the inner peripheral surface and the outer peripheral surface of the cylindrical piezoelectric element, and a plurality of electrodes are provided on the other surface of the cylindrical piezoelectric element. A vibrating part adapted to apply an alternating voltage having a phase difference of 1., a member that comes into contact with a part of the outer peripheral surface of the vibrating part, and a means for bringing the vibrating part and the member into pressure contact.

[Action]

Since the vibrating portion that generates the traveling wave is formed in a circular shape, the moving body always receives a uniform pressure contact force regardless of the position of the moving body, so that the moving body can be fed constantly. .

〔Example〕

In FIG. 1 and FIG. 2, most of the cylindrical vibrating portion 2 having the structure shown in FIG. 3 is embedded inside the holding member 1 and a part of the outer peripheral surface is exposed to the outside. It is held in a state. A shaft body 3 is coaxially inserted into the vibrating portion 1, and the shaft body 3 is fixed to the holding portion 1. An elastic body 4 made of semi-cylindrical rubber or the like is interposed between the shaft body 3 and the inner peripheral surface of the vibrating portion 2 to pressurize and fix the vibrating portion 2.

A movable body 5 is provided so as to be movable in the directions of arrows a and b in contact with the exposed portion of the vibrating portion 2. In addition, the pair of guide rollers 6 and 7 press the moving body 5,
The moving body 5 is pressed against the vibrating portion 2. The moving body 5 has a structure in which an elastic body 8 made of rubber containing asbestos and a metal plate 9 are laminated, and the elastic body 8 is in contact with the vibrating portion 2. The moving body 5 may be moved along a guide rod or the like without depending on the guide rollers 6 and 7.

As shown in FIG. 3, the vibrating portion 2 has one electrode 11 provided on the outer peripheral surface of a cylindrical piezoelectric element 10 having a length l and four electrodes 12 ₁ to 12 _{1 on} the inner peripheral surface. 12 ₄ in which is made provided.

The cylindrical piezoelectric element 10 used is polarized in a direction from the inner side to the outer side as shown by an arrow c. The electrodes 12 _{1 to} 12 ₄ have a total circumferential length of ₄ of the piezoelectric element 10.
It is arranged to divide equally.

FIG. 4 shows an embodiment of the drive circuit for the vibrating section 2.

In the figure, the drive voltage obtained from the AC drive power supply 13 is applied to the electrode 12 ₁ through the amplifier 14, and
After being phase shifted by 90 ° by the 0 ° phase shifter 15, the amplifier 16
It applied to the electrodes 12 ₂ through. After being 180 ° phase shifted by the driving voltage further 180 ° phase shifter 17, together with the applied to the electrodes 12 ₃ via the amplifier 18, 27
After the phase is shifted by 270 ° by the 0 ° phase shifter 19, the amplifier 2
0 is applied to the electrode 12 ₄ through. The electrode 11 is grounded. According to the above, voltages having a phase shift of 90 ° are sequentially applied to the electrodes 12 _{1 to} 12 ₄ . That is, if the voltage applied to the electrode 12 ₁ is cosωt,
The electrodes 12 ₂ , 12 ₃ , and 12 ₄ have sin ωt and −cos ω, respectively.
A voltage of t, −sinωt will be applied.

As a result, the portions 10 ₁ to 10 ₄ of the length λ / 4, which are sandwiched between the electrodes 12 _{1 to} 12 ₄ and the electrode 11, of the piezoelectric element 10 are sequentially shifted by 90 ° in the radial direction. Vibration is generated, and this vibration advances in one direction along the circumferential direction.
That is, a traveling wave of wavelength λ is generated along the circumferential direction of the piezoelectric element 10. In FIGS. 1 and 2, when the vibration of the traveling wave is transmitted to the moving body 5, the moving body 6 moves in the a direction or the b direction. 1 and 2, the movable body 5 is fixed and the holding member 1
Alternatively, the vibrating section 2 held by may be moved.
Further, instead of the guide rollers 6 and 7, another vibrating section 2 may be used.

FIG. 5 shows a second embodiment of the present invention, in which parts corresponding to those in FIG. 4 are designated by the same reference numerals.

In this embodiment, the polarization direction of the piezoelectric element 10 is the direction from the inside to the outside of the portions 10 ₁ and 10 ₂ as indicated by arrows d and e in the figure, and the portions 10 ₃ and 1 are
At 0 ₄ , the direction is from the outside to the inside. At the same time, the drive voltage of the drive power supply 13 is supplied to the amplifiers 14 and 18
In addition to the electrodes ₁₂ 1, 12 ₃ as the through cos .omega.t, electrodes ₁₂ 2 a voltage of the driving voltage is 90 ° phase-shifted by 90 ° phase shifter 15 as sinωt through amplifiers 16, 20, 1
So that added to the 2 _4.

FIG. 6 shows a third embodiment of the present invention.
Ground electrodes 11 ₁ and two drive electrodes 12 ₁ , 12 ₂
Preparative provided with, and one of the ground electrode 11 ₂ inside 2
The drive electrodes 12 ₃ and 12 ₄ are provided.

In the case of the vibrating section 2, the drive voltage applied to the drive electrodes 12 _{1 to} 12 ₄ is the drive electrodes 12 ₃ , 12 ₁ , 1
2 ₂ and 12 ₄ are cosωt, −sinωt, cosωt, and −s, respectively.
A voltage of inωt is applied.

In addition to the first to third embodiments described above, the polarization direction of the piezoelectric element 10 and the phase of the voltage applied to the electrodes 12 _{1 to} 12 ₄ can be variously selected. Further, the number of electrodes 12 _{1 to} 12 ₄ is not limited to four, and a minimum of 2 to 2 × n can be used. The drive voltage requires at least two phases.

In addition to the radial vibration that contributes to the movement of the moving body 5, the piezoelectric element 10 also vibrates in the axial direction (direction of length l in FIG. 3). In order to prevent the axial vibration from affecting the movement of the moving body 6, the frequency of the radial vibration may be lower than the resonance frequency of the axial vibration. For this purpose, the length 1 of the vibrating portion 2 may be set so as to have a relationship of approximately 1 <λ / 4 with respect to one wavelength λ of the radial vibration.

〔The invention's effect〕

Since the vibrating portion 2 has a cylindrical shape as shown in FIG. 3 and is configured to generate a wave on the outer peripheral surface thereof, the curvature is constant and there is no break in the traveling direction of the wave. That is, since it is a continuous body without end portions, scattering or reflection of waves does not occur. Therefore, a uniform traveling wave can be generated. Further, since the moving body comes into pressure contact with only a specific portion on the outer peripheral surface of the vibrating portion, the influence on the wave becomes constant regardless of the relative position of the moving body and the vibrating portion. Therefore, a constant traveling feed can be performed with a constant traveling wave, and the motor structure can be made small and simple.

[Brief description of drawings]

1 to 3 show the first embodiment of the present invention.
Is a side sectional view, FIG. 2 is a perspective view, FIG. 3 is a perspective view of a vibrating portion, FIG. 4 is a drive circuit diagram, FIG. 5 is a circuit diagram showing a second embodiment of the present invention, and FIG. [FIG. 8] is a side view of a main portion showing a third embodiment of the present invention. In still code used in the drawings, 2 ...... vibrating section 5 ...... mobile 6,7 ...... guide roller 10 ...... cylindrical piezoelectric element 11 is a ...... electrode 12 ₁ to 12 ₄ ...... electrode.

Claims (1)

[Claims] 1. A cylindrical piezoelectric element is provided with at least one electrode on one surface of an inner peripheral surface and an outer peripheral surface and a plurality of electrodes on the other surface, and the plurality of electrodes are provided with predetermined electrodes. By applying an AC voltage having a phase difference of, a vibrating section that is made to generate an elastic wave traveling in the circumferential direction, a member that contacts a part of the outer peripheral surface of the vibrating section, the vibrating section and the member A linear elastic wave motor, wherein the vibrating portion and the member are moved relative to each other.