JPS63209484A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To lengthen the life of a motor, by arranging magnets respectively face to face in the thrust direction and in the axial direction of a fixed bolster and rotation main shaft of the ultrasonic motor. CONSTITUTION:An ultrasonic motor is composed of piezoelectric elements 10 and 11, an elastic body 12, a lining material 13, a body of revolution 14, a fixed bolster 15, a rotating main shaft 16, ring-shaped magnets 17-20. In the radial direction of the rotating main shaft 16 and fixed bolster 15 on the circumference facing each other, by arranging magnets 17-18 respectively, the rotating main shaft 16 gets out of contact with the fixed bolster 15 and at the same time the axial dislocation of the rotating main shaft 16 in rotation can be prevented. In the thrust direction, to the position where the rotating main shaft 16 faces the fixed bolster 15, by arranging magnets 19-20 on each circumference, the pre-load between the body of revolution 14 and the elastic body 12 can be ensured. The contact position can thereby be reduced remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ultrasonic motor driven by traveling wave vibration energy.

[Conventional technology]

FIG. 6 is a sectional view of a conventional ultrasonic motor. In FIG. 1, 1.2 are piezoelectric elements mounted at 90° offset from each other, 3 is an elastic body, 4 is a lining material, 5 is a rotating body, and 6 7 is a ball bearing, 7 is a fixed base, and 8a is a nut. By tightening this nut 8a, an appropriate contact pressure is applied between the rotating body 5 and the elastic body 3 by a disc spring 8b. 9 is a rotation axis.

Next, the operation will be explained.

By applying alternating current voltages having a temporal phase difference of 90° to each piezoelectric element 1.2, each piezoelectric element 1.
The combination of the standing waves generated by 2 generates a traveling wave which is the driving source of the motor. This traveling wave is excited in the elastic body 3, and as a result, the rotating body 15 placed on the elastic body 3 with the lining material 4 interposed therebetween rotates in a direction opposite to the direction in which the traveling wave travels.

The ultrasonic motor operates in this way, but if the rotating body 5 is simply placed on the elastic body 3, the center axis of the elastic body 3 and the center axis of the rotating body 5 will be misaligned due to the vibration of the traveling wave. In order to prevent this, the elastic body 3 is fixed to the fixed base 7 via the piezoelectric element 1.2, and a ball bearing 6 is attached to this elastic body 3, so that the rotating body 5 and the rotating shaft 9 are integrated. This prevents the center axis of the elastic body 3 and the center axis (rotation axis) of the rotating body 5 from being misaligned.

[Problem that the invention seeks to solve]

Since the conventional ultrasonic motor is constructed as described above, the ball bearing 6 is coated with lubricating oil to ensure smooth rotation. Therefore, when an ultrasonic motor is introduced into a vacuum atmosphere, gas is generated and the degree of vacuum deteriorates. Further, if the lubricating oil applied to the ball bearing 6 is wiped off by cleaning or the like, there is a problem that the rotating body 5 will not rotate smoothly.

This invention was made to solve the above-mentioned problems, and an object thereof is to obtain an ultrasonic motor that can be used even in a vacuum atmosphere.

[Means for solving problems]

In the ultrasonic motor according to the present invention, two piezoelectric elements are mounted on a fixed base with a shift of 174 wavelengths, an elastic body is attached to the piezoelectric elements, and a rotating main shaft is loosely inserted into the central axis of the fixed base. and at least one pair of magnets are provided on the fixed base so as to face each other in the thrust direction and the radial direction so that a repulsive force acts thereon.

[Effect]

In the ultrasonic motor of the present invention, by arranging magnets on the circumferences of the rotating main shaft and the fixed base that face each other in the radial direction, contact between the rotating main shaft and the fixed base is eliminated, and the rotational main shaft during rotation is It is possible to prevent axis misalignment, and in the thrust direction, by providing magnets on the circumferences of the rotating main shaft and fixed base at opposing positions, the preload between the rotating body and the elastic body, which is important for driving the ultrasonic motor, can be reduced. This makes it possible to minimize the factors that deteriorate the degree of vacuum in the vacuum chamber, and to enable use in a vacuum atmosphere.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view showing a first embodiment of the invention, FIG. 2 is a cutaway perspective view of the fixed base shown in FIG. 1, and FIG. 3 is a perspective view showing the rotating main shaft shown in FIG. 1. .

In Figures 1 to 3, 10.11 is 174 to each other.
Piezoelectric elements installed with different wavelengths, 12 is piezoelectric element 1
0.11 is the attached elastic body, 13 is the lining material,
14 is a rotating body; 15 is a fixed base inserted into the elastic body 12; the piezoelectric element 10° 11 and the elastic body 12 are mounted on the fixed base 1 so that they do not rotate or shift in position;
It is fixed to 5. Reference numeral 16 denotes a rotating main shaft that is loosely inserted into the central axis of the fixed base 15, and the tip of the rotating main shaft 16 is fitted onto the rotating body 14. 17. 17 is a ring-shaped magnet fixed to the outer circumferential wall of the rotating main shaft 16, 18.18 is a ring-shaped magnet fixed to the inner circumferential wall of the fixed base 15; Magnets 18.degree. 18 of the fixed base 15 are provided radially opposite to the magnets 17 so as to exert repulsive forces on each other.

19.19 is a ring-shaped magnet fixed to the back surface of the fixed base 15; 20.20 is a ring-shaped magnet fixed to the surface of the flange 16a of the rotating main shaft 16; Magnets 19 and 19 of the fixed base 15 are provided opposite to each other in the thrust direction at 20 and 20, and repulsive forces are exerted on each other.

Next, the operation will be explained.

By applying alternating current voltages with a temporal phase difference of 90° to each piezoelectric element 10.11, the standing waves generated by each piezoelectric element 10.11 are synthesized to generate a traveling wave, which is the drive source of the ultrasonic motor. Waves are generated. The traveling wave is an elastic body 12
The rotating body 1 is excited by and the lining material 13 is attached.
4 is given a rotational motion in the opposite direction to the traveling wave. and,
Magnets 19.20 for applying the necessary contact pressure between the rotating body 4 and the elastic body 12 are attached in the thrust direction of the fixed foot stand 15 and the rotating main shaft 16, so that the piezoelectric elements 10.11 The vibration energy of is efficiently transferred to the rotating body 14.
will be converted into rotational kinetic energy. Also,
In the radial direction between the fixed base 15 and the rotating main shaft 16, the rotating main shaft 16 fixed to the rotating body 14 is held so as not to come into contact with the fixed base 15, so that the axis shift of the rotating main shaft 16 is prevented and the rotating main shaft 16 is 14 to provide smooth rotational movement without eccentricity.

In the above embodiment, the magnet was shown as having a ring shape, but if the magnet attached to the fixed base 15 or the rotating main shaft 16 is ring-shaped, the other magnet is a ring-shaped magnet.
As shown in the figure, the same effect as in the above embodiment can be obtained even if the magne-cito groups 21 and 22 are arranged at arbitrary constant intervals on the circumference.

Further, in the above embodiment, the explanation has been given of a case that utilizes the repulsive force generated when magnets of the same polarity are placed opposite each other, but the present invention is not limited to this.As shown in FIG. The magnets 23 and 24 may be made to face each other, and the contact pressure between the rotating body 14 and the elastic body 12 may be obtained using attractive force, and the same effect as in the above embodiment can be obtained. In addition, it goes without saying that not only permanent magnets but also electromagnets can be used as magnets. In particular, if at least one of the opposing magnets in the thrust direction is used as an electromagnet whose magnetic force can be electrically controlled, it is possible to The preload between the rotating body 14 and the elastic body 12 can be appropriately controlled depending on the weight of the sample placed on the rotating body 14.

〔Effect of the invention〕

As described above, according to the present invention, the ultrasonic motor is configured such that the magnets are disposed so as to face the fixed base and the rotating main shaft in the thrust direction and the radial direction, respectively, so that the mechanical relationship between the rotating main shaft and the fixed base is Moreover, the contact pressure between the rotating body and the elastic body, which is essential for ultrasonic motors, can be ensured. Therefore, even when used in a vacuum atmosphere, the factors that deteriorate the degree of vacuum can be eliminated, and the contact pressure can be ensured. Since there are very few parts that are damaged, it has the effect of extending the lifespan.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing an ultrasonic motor according to a first embodiment of the present invention, FIG. 2 is a cutaway perspective view of the fixing base shown in FIG. 1, and FIG. FIG. 4 is an exploded perspective view showing a second embodiment of the invention, FIG. 5 is a vertical sectional view showing a third embodiment of the invention, and FIG. 6 is a longitudinal sectional view showing a conventional ultrasonic motor. It is a front view. 10, II is a piezoelectric element, 12 is an elastic body, 14 is a rotating body,
15 is a fixed base, 16 is a rotating main shaft, 17° 1B, 19, 2
0, 21.22, 23.24 are magnets. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. (2 others) Figure 4 Figure 5 and 5 24

Claims (1)

[Claims] By attaching two piezoelectric elements to a fixed base with a 1/4 wavelength shift from each other, attaching an elastic body to the piezoelectric elements, and applying alternating current voltages with a temporal phase shift of 90° to each of the piezoelectric elements. In an ultrasonic motor that rotates a rotary body placed on the elastic body based on vibrations of the elastic body that combine constant pressure waves generated by each piezoelectric element, a fixed base on which the piezoelectric element is attached; at least one pair of magnets are provided facing each other in the radial direction of the fixed base and the rotating main shaft, respectively, so that a rotating main shaft whose tip end is attached to the rotating body is loosely inserted concentrically into the central axis of the elastic body; At least one of the fixed base and the rotating main shaft is arranged opposite to each other in the thrust direction so as to hold the rotating body with appropriate contact pressure against the rotating body.
An ultrasonic motor characterized by being provided with a pair of magnets.