JPH0710186B2 - Ultrasonic motor - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an ultrasonic motor utilizing ultrasonic vibration.

BACKGROUND OF THE INVENTION An apparatus of this type is disclosed in Japanese Patent Application Laid-Open No. 59-204476 by the present applicant. In this publication, as a factor that hinders the improvement of the efficiency of the ultrasonic motor, the difference in the resonance frequency depending on the radial position of the elastic body is mentioned, and the thickness of the elastic body 3 on which the piezoelectric body 4 is fixed is rotated as shown in FIG. This problem was solved by increasing the distance from the central axis in the radial direction. However, in this solution, since the pressure contact surface 3a between the elastic body and the rotor, which requires high surface accuracy, is not a flat shape, it is very difficult to manufacture the pressure contact surface of both the elastic body and the rotor in the same surface shape. It had a drawback.

(Object of the Invention) An object of the present invention is to solve these drawbacks and to provide an ultrasonic motor which is highly efficient and easy to manufacture.

(Summary of the Invention) The present invention provides a groove portion in a pressure contact surface of an annular elastic body to which an annular rotor is pressed in an ultrasonic motor, and the depth of the groove portion is increased in a radial direction from a rotation center axis. The technical point is to reduce the resonance frequency to minimize the difference in the resonance frequency depending on the radial position of the elastic body and improve the efficiency.

(Embodiment) FIGS. 1 (A) and 1 (B) show an embodiment of the present invention, wherein FIG. 1 (A) is a perspective view of a stator, and FIG. 1 (B) is the stator. FIG. In FIG. 1, a piezoelectric body 2 that excites the elastic body is fixed to an annular elastic body 1, and the elastic body 1 and the piezoelectric body 2 constitute a stator. A rotor (not shown) is brought into pressure contact with the pressure contact surface 1a of the elastic body 1 of the stator, and an ultrasonic motor is constituted by the stator and the rotor. A surface wave (traveling wave) is generated by being excited by the piezoelectric body 2 on the pressure contact surface 1a of the elastic body 1 of the stator against which the rotor (not shown) is pressure contacted, and the rotor is driven by the surface wave. The pressure contact surface 1a of the elastic body 1 is provided with grooves 1b around the entire circumference at a predetermined pitch (FIG. 1 (A) simplifies the drawing and shows only a part of the grooves provided around the circumference. The other part is shown using a chain double-dashed line). The depth of the groove portion 1b from the pressure contact surface 1a is shown in FIG. 1 (B).
As shown in (4), it is reduced as it moves away from the rotation center axis OO ′ in the radial direction. As disclosed in Japanese Patent Application Laid-Open No. 59-204476, the traveling wave generated in the elastic body 1 of the stator changes in angular velocity depending on the radial position of the pressure contact surface 1a of the elastic body 1. The depth of the groove portion 1b formed in the elastic body 1 is formed such that the depth of the groove is reduced as the radial position increases, so that it does not change depending on the position. In the elastic body 1, the wavelength of the traveling wave becomes longer as the diameter increases, but the rigidity increases as the diameter increases by changing the depth of the groove depending on the diameter position. The difference in resonance frequency can be minimized. Moreover, since the pressure contact surface 1a with the rotor is a flat surface, high surface accuracy (flatness and surface roughness in this case) can be easily realized by lapping or the like. Since the configuration of the groove portion 1a changes variously depending on the material, shape, and the like of the elastic body 1, when determining the depth of the groove portion 1a, for example, the optimum depth should be selected by obtaining it by structural analysis and realization. do it.

Further, an improved example of this embodiment will be described. By forming a groove in the pressure contact surface of the stator as disclosed in Japanese Patent Application Laid-Open No. 59-204480 filed by the present applicant, deposits and the like generated by pressure contact between the stator and the rotor are eliminated and durability It can also be applied to ultrasonic motors that have been improved. That is, in this ultrasonic motor, the groove portion is provided on the entire pressure-contact surface of the stator as in the above-described embodiment, so that the adhered matters and the like that are pressure-contacted by the pressure contact between the stator and the rotor are removed. You may make it comprise a groove part.

In the embodiment, in the structure of the groove portion 1b of the pressure contact surface 1a of the stator, that is, in the arrangement of the distance between the groove portions and the depth and width of the groove portion, the vibration that is the drive source of the ultrasonic motor is changed. It can be easily compounded or made into a single normal vibration. For example, in order to make an ultrasonic motor using compound resonance, it suffices to configure a large number of grooves at equal intervals in the stator. In order to make an ultrasonic motor using a single vibration, the groove portions may be formed in the stator at equal intervals so that the rigidity of the convex portions between the groove portions is increased.

(Effect of the invention) As described above, according to the present invention, the groove portion is provided on the pressure contact surface of the elastic body against which the rotor is pressure contacted, and the depth of the groove portion is reduced as the distance from the rotation center axis is increased in the radial direction, By minimizing the difference in the resonance frequency depending on the radial position of the elastic body, it is possible to obtain a high drive efficiency without imposing a difficult processing method on the pressure contact surface with the rotor.

[Brief description of drawings]

FIG. 1 (A) is a perspective view of an embodiment of an ultrasonic motor according to the present invention, and FIG. 1 (B) is a sectional view of the ultrasonic motor. FIG. 2 is a sectional view of a conventional ultrasonic motor. (Explanation of the symbols of the main parts) 1,3 …… Elastic body, 2,4 …… Piezoelectric body 1a …… Pressing contact surface, 1b …… Groove

Claims (1)

[Claims] 1. An ultrasonic motor comprising a ring-shaped elastic body, a piezoelectric body for exciting the elastic body, and a ring-shaped rotor pressed against the elastic body, wherein the ring-shaped rotor is pressed against the ring-shaped rotor. An ultrasonic motor characterized in that a groove portion is provided on a pressure contact surface of an elastic body, and a depth of the groove portion is reduced as the depth of the groove portion is increased in a radial direction from a rotation center axis.