JPH02285973A - Surface traveling wave driving actuator - Google Patents

Abstract

PURPOSE:To obtain a new type actuator by employing a drive member, which makes an arched motion around a shaft, in place of a rotor. CONSTITUTION:A surface traveling wave actuator comprises an annular resilient stator 11, a body 12 for securing the stator 11, a driving member 15, and the like. The driving member 15 is provided with a semi-circular section 15a having identical curvature to that of the stator 11 and extending longer than half of the stator 11, and on arched lining material 16 in contact with the thrust face 11c is jointed to the opposite side of the central shaft 14 with respect to the center of the stator 11. Voltage having predetermined frequency is applied onto the piezoelectric board 13 in the stator 11 in order to produce surface traveling wave thus producing rotary driving force in the driving member 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a surface traveling wave drive actuator that obtains a driving force by a surface traveling wave generated on an arcuate thrust surface of an elastic body.

"Prior art and its problems" An actuator using a surface traveling wave as a driving source was published in Japanese Patent Application Laid-open No. 5
It was proposed in No. 8-148682 and is widely known as an ultrasonic motor. This ultrasonic motor has a basic structure in which a rotor, which is also annular, is brought into contact with the thrust surface of a stator made of an annular elastic member, and rotational force is applied to the rotor by generating surface traveling waves on the thrust surface of the stator. have The structure is extremely simple and thin, and especially when used in optical equipment that uses lenses, it has the advantage that since it is annular as a whole, it can be placed comfortably without forming protrusions around the lens. However, when actually mounted on a lens, various difficulties arose in the means for pressing the rotor against the stator and the structure for maintaining coaxiality between the rotor and stator, making it difficult to put it into practical use.

In addition, conventional ultrasonic motors have been considered only from the perspective of how to efficiently rotate the rotor on the stator with a strong force, and no consideration has been given to other forms of use.

``Object of the Invention'' The present invention was completed by discovering that a different actuator can be obtained by departing from the idea of an ultrasonic motor in which the rotor rotates infinitely.

That is, an object of the present invention is to obtain an actuator in which a driving member moves in an arc around an axis by a surface traveling wave generated on the thrust surface of an elastic body.

``Summary of the Invention'' The surface traveling wave actuator of the present invention uses a driving member that moves in an arc around an axis in place of the rotor in a conventional ultrasonic motor, and uses a driving member that moves in an arc around an axis, and uses a surface traveling wave that is generated on the thrust surface of the stator. It is something that is driven. That is, unless the rotation center axis of the drive member and the rotation center of the arcuate thrust surface of the stator do not coincide, the drive member cannot be rotated infinitely, but it can be made to move in an arc.

In the actuator of the present invention, the stator is provided with an arcuate thrust surface and a means for generating a surface traveling wave in the circumferential direction of the thrust surface, and the drive member includes a contact portion that contacts the thrust surface of the stator; A rotation center axis is provided at a position different from the arc center of the thrust surface, and the driving member is moved in an arc around the rotation center axis by a surface traveling wave of the thrust surface.

The motion angle of the drive member mainly depends on the amount of eccentricity between the rotation center axis of the drive member and the arc center of the thrust surface. Therefore, the actuator of the present invention can be widely used as an actuator for devices that require not rotational movement but circular arc movement at a limited angle. for example.

If the rotation center axis of the drive member is located outside the annular stator, the rotation angle of the drive member is small, but the actuator can be used as a drive source for, for example, a focusing lens group or an aperture. can get.

"Embodiments of the Invention" The present invention will be described below with reference to illustrated embodiments. Figure 1A,
FIG. 1B shows the basic form of the actuator of the present invention. For example, the annular stator 11 made of an elastic material such as phosphor bronze or stainless steel has a flange 11a for fixing 5 on a part of its periphery.
The fixed object 1 is connected through the collar 11a and
It is fixed at 2. A piezoelectric plate 13 is bonded to the back surface of the stator 11. As is well known, this piezoelectric body plate 13 has a 2M structure, and is subjected to appropriate polarization treatment and electrode arrangement, and by applying a frequency voltage with an appropriate phase difference, the piezoelectric body plate 13 is A surface traveling wave is generated on the thrust surface 11c of the stator 11 opposite to the plate 13. A drive member 15 is located on the stator 11, which is pivotally connected to a fixed object 12 by a rotation center shaft 14 located outside the stator 11. This drive member 15 has a semi-annular part 15a having the same curvature as the annular stator 11 and a length of a little more than half of the curvature, and has a thrust surface 11c on the opposite side of the rotational axis 14 with respect to the center of the stator 11. A contacting arc-shaped lining material 16 is joined. Further, the drive member 15 is formed with a drive notch 15b that is located approximately at the center of the lining material 16 and projects outward in the radial direction. The drive member 15 is given a force to move toward the stator 11 by a compression spring 17 inserted into the rotational center shaft 14, and the thrust surface 11c of the stator 11 and the lining material 16 are arranged in a circular arc where the lining material 16 exists. Contact is made with a constant contact pressure in the section. That is, the lining material 16 is attached to the thrust surface 1 provided on the drive member 15.
This is the contact part with 1c.

In this actuator having the above configuration, when a predetermined frequency voltage is applied to the piezoelectric plate 13 of the stator 11 to generate a surface traveling wave on the thrust surface 11c of the stator 11, a rotational driving force is generated in the drive member 15. The ultrasonic motor corresponds to a case where the drive member 15 is a rotor whose rotation center is at the center of the stator 11, but in the present invention, the drive member 15 has a rotation center at a rotation center axis 14 that is different from the center of the stator 11. It is said that Therefore, the drive member 15 can perform circular arc movement around the rotation center shaft 14 and perform work through the drive notch 15b. The angle of the circular motion is based on the rotation center axis 14
Although it depends on the amount of eccentricity from the center of the stator 11, the drive member 15 rotates smoothly within a limited angular range.

The rotation angle and direction of the drive member 15 can be determined by the time of the AC voltage applied to the piezoelectric plate 13 and the phase (difference) of the frequency voltage. That is, the driving member 15 is
The piezoelectric plate 13 moves to either the left or right, which is determined by the phase difference between the AC voltages applied to the piezoelectric plate 13, by an amount proportional to the number of applied voltages. Therefore, by controlling the wave number of the AC voltage applied to the piezoelectric plate 13, it is possible to control the stop position with high resolution.
6) has high position holding ability due to frictional contact with
The dynamic characteristics when stopped are also good.

If the driving member 15 is formed into the same arc as the stator 11,
It can also be applied to optical products such as lenses. For example, the drive notch 15b can be connected to a focus adjustment lens or an aperture drive ring and used as a focus adjustment actuator or an aperture actuator.

The length of the arc section of the lining material 16 is the thrust surface 1
It is efficient to set the wavelength to approximately twice the wavelength of the surface traveling wave generated at 1c. Because by making it twice the wavelength,
This is because the lining material 16 always comes into contact with the peaks of the surface traveling waves generated on the thrust surface 11c.

2A and 2B show the thrust surface 11c of the stator 11.
This is an embodiment in which the drive member 15 is formed only in a limited portion that comes into contact with the lining material 16. That is, stator 1
1, only the thrust surface 11c portion that contacts the lining material 16 is formed thick, and the other portion is a thin portion lid.

This configuration provides the following effects.

If the thrust surface 11c, on which the drive member 15 slides, has even the slightest unevenness, smooth operation cannot be expected, and the lining material 16 is likely to wear out.
Durability decreases. Therefore, the thrust surface 11c requires lapping or bolling processing, but by reducing the angular range of the thrust surface 11c that requires this precision surface processing, it can be expected that processing time and processing costs can be reduced.

FIGS. 3A and 3B show an embodiment in which the thrust surface 11c is formed into a comb-teeth shape by a plurality of cuts made perpendicularly to the thrust surface 11c. This configuration provides the following effects.

The amplitude of the traveling wave distortion generated in the piezoelectric plate 13 is
It is transmitted from the adhesive surface side of the piezoelectric plate 13 of No. 1 to the contact surface (thrust surface 11C) side of the drive member 15, but the thrust surface 11c
If it is made into a comb-like shape, the amplitude can be expanded, the wavelength of the surface traveling wave can be expanded, and the driving member 15 can be rotated quickly.

FIG. 4 shows a thin annular elastic body if and a drive member 1.
In this embodiment, the stator 11 is constructed by joining the arc-shaped thrust surface member 11g that is in contact with the stator 5. A thrust surface 11c is formed on the thrust surface member 11g. According to this configuration, the following effects can be obtained.

Since the annular elastic body 11f only needs to efficiently generate surface traveling waves, it may have a thickness that allows it to be punched out using a press. Therefore, if the flange 11a and llb are punched out at the same time, it can be manufactured at an extremely low cost.

FIG. 5 shows a first embodiment in which the force that brings the drive member 15 into contact with the thrust surface 11c is generated by magnetic force. The stator 11 is made of a magnetic material such as iron. First, a permanent magnet I8 is bonded to the drive member 15, and a lining material 16 that contacts the thrust surface 11c is bonded thereon.

According to this configuration, the lining material 16 comes into contact with the thrust surface 11c due to the magnetic attraction force acting between the permanent magnet 18 and the stator 11, so that a good contact state is obtained, and the compression around the rotation center shaft 14 is The spring 17 becomes unnecessary. Note that the material of the stator 11 does not need to be a high-grade material such as pure iron or permalloy (although any material with residual holding power can be applied to this embodiment.

FIG. 6 shows a second embodiment using magnetic attraction. A magnetic material block 19 such as iron is fixed to the fixed object 12,
A permanent magnet 20 is fixed to the drive member 15 and faces the magnetic material block 19 with a gap therebetween.

According to this embodiment, the same effect as the embodiment shown in FIG. 5 can be obtained, and unlike the structure shown in FIG. There is a high degree of freedom from Of course, the positional relationship between the magnetic material block 19 and the permanent magnet 20 may be reversed, and the magnetic material block 19 (or permanent magnet 20)
may be installed on the stator 11.

"Effects of the Invention" As described above, the surface traveling wave actuator of the present invention can cause the drive member to move not in rotation but in an arc.

Therefore, a wide range of applications can be expected as a new type of actuator.

[Brief explanation of drawings]

1A and 18 show a first embodiment of the actuator according to the present invention. FIG. 1A is a front view, and FIG. 1B is a right side view of FIG. 1A, with a portion thereof in section. 2A and 2B are a front view and a right side view corresponding to FIGS. 1A and 18, showing another embodiment of the actuator according to the present invention. 3A and 3B show still another embodiment of the actuator according to the present invention, where FIG. 3B is a front view and FIG. 3A is a view taken in the direction of arrow A in FIG. 3B. FIG. 4 is a perspective view showing another embodiment of the stator used in the actuator according to the present invention. 5 and 6 are side views corresponding to FIG. 1B, respectively, showing still another embodiment of the present invention. llf... Annular elastic body, l1g... Thrust surface member, 12... Fixed object, 13... Piezoelectric plate, 14...
... Rotation center axis, 15... Drive member, 15a... Semi-annular part, 15b... Drive notch, 16... Lining material (contact part), 17... Compression spring, 18... Permanent magnet, 19... Magnetic material block, 20... Permanent magnet. Patent Applicant Asahi Optical Co., Ltd. Agent Kunio Miura 11... Stator, lla, 11... Tsuba, llc.
...Thrust surface, lid...Thin wall part, lie...Incision Fig. 2A Fig. 2B Fig. 6

Claims (7)

[Claims] (1) A stator made of an elastic body having an arc-shaped thrust surface and a means for generating a surface traveling wave in the circumferential direction of the thrust surface; and a contact portion that contacts the thrust surface of the stator; 1. A surface traveling wave drive actuator comprising a drive member that has a rotation center axis located at a position different from the center of the circular arc and performs circular arc motion around the rotation center axis. (2) The actuator according to claim 1, wherein the stator has a thrust surface thicker than other parts. (3) The actuator according to claim 1 or 2, wherein the thrust surface of the stator has a comb-like shape having a plurality of notches perpendicular to the thrust surface. (4) In any one of claims 1 to 3, the stator is composed of an annular elastic body having a uniform thickness and a thrust surface member that is created separately from the annular elastic body and joined to the annular elastic body. actuator. (5) In any one of claims 1 to 4, the stator is made of a magnetic material, a permanent magnet is provided on the drive member side, and the thrust surface of the stator is driven by the magnetic attraction force acting between the two. An actuator that comes into contact with a member. (6) In any one of claims 1 to 4, either one of the magnetic material and the permanent magnet is installed on the stator side, and the other of the magnetic material and the permanent magnet is disposed on the drive member side, facing each other with a space therebetween. The actuator is installed so that the thrust surface of the stator and the driving member come into contact with each other due to the magnetic attraction force that acts between them. (7) The actuator according to any one of claims 1 to 6, wherein the stator has an annular shape as a whole, and the rotation center axis of the drive member is located outside the annular stator.