JPS61116977A - Supersonic wave drive motor - Google Patents

Abstract

PURPOSE:To enhance the efficiency of a supersonic wave drive motor by providing a plurality of grooves on the drive surface of a supersonic vibrator, and equalizing the resonance frequency generated thereat to the resonance frequency of a base, thereby increasing the output of the motor. CONSTITUTION:A supersonic wave drive motor has a stator 1, a rotor 2, the stator 1 is supported to a stator support provided at a stator stationary base 3, and an exciter 8 bonded with a member of iron for forming a piezoelectric unit and the drive surface 6 is supported. The rotor 2 has a ring-shaped driven surface 9, and a rotational shaft 10 at the center. In this case, many grooves 11 are radially formed on the surface of the drive surface 6 of the stator 1 to increase the Q value. The groove structure is formed with a projection of thickness t2 on the base of the thickness t1 of the stator, so that the thickness t2 and the width l2 are so selected that the resonance frequency f1 determined by the thickness t2 and the width l2 and the basic frequency f2 determined by the thickness t1 and the diameter l1 of the base material become equal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention uses ultrasonic vibration as a driving source. This invention relates to an ultrasonic drive motor.

(Conventional structure and its problems) Conventionally, ultrasonic drive motors have a piezoelectric material in the stator section as a vibration excitation section, and the drive surface of the stator section is moved in the axial direction (perpendicular to the wavefront) and in the circumferential direction. The rotor is vibrated by sound waves, and the driven surface of the rotor portion is brought into contact with the driving surface to transmit the vibration to the driven surface, thereby moving the rotor portion. Such ultrasonic drive motors have a simple structure and are therefore widely used in electronic equipment, cameras, medical equipment, and the like.

However, due to its structure, this ultrasonic drive motor extracts only a portion of the vibration components of the stator portion as output motion, and therefore has a drawback of low power efficiency.

In order to increase power efficiency, it is possible to vibrate the stator with a large amplitude using less power, but in reality, due to the presence of internal losses within the solid, large-amplitude vibrations actually lead to a decrease in efficiency. .

(Objective of the Invention) An object of the present invention is to eliminate the conventional drawbacks and provide an efficient ultrasonic drive motor.

(Structure of the Invention) The ultrasonic drive motor of the present invention includes an ultrasonic vibrating body having a driving surface, and a driving surface contacting body that contacts the ultrasonic vibrating body and extracts a part of the vibration as external motion. In the ultrasonic drive motor, a plurality of grooves having a concave cross-sectional shape are provided on the drive surface of the ultrasonic vibrator, and the resonant frequency of the convex portion generated by the formation of the grooves is controlled by the ultrasonic drive motor having the drive surface. This is made equal to the resonant frequency of the basic part of the acoustic wave vibrator excluding the convex part.

(Description of Embodiment) An embodiment of the ultrasonic drive motor according to the present invention will be described based on FIGS. 1 to 6.

FIG. 1 is a perspective view of the ultrasonic drive motor, FIG. 2 is a cross-sectional view thereof, and FIG. 3 is a side view of the excitation section. In the figure, 1 is a stator part, 2 is a rotor part, and the stator part 1 has a member 7 such as iron forming a piezoelectric body 5 and a driving surface 6 on a stator support part 4 provided on a stator fixing base 3. It supports two excitation parts 8 which are bonded to each other, and the drive surface 6 has a ring shape. The rotor portion 2 has a driven surface 9 shaped like a ring, and has a rotating shaft 10 at the center.

The piezoelectric body 5 of the stator section 1 is divided into parts in the circumferential direction by a plurality of (N) electrodes, and by applying a voltage to adjacent piezoelectric bodies 5, wavy vibrations can be generated as shown in FIG. cause The vibration direction has an axial component and a circumferential component, and each part of the drive surface 6 performs an elliptical motion.

Therefore, the driven surface 9 in contact with the driving surface 6 absorbs vibrations in the axial direction and rotates due to the vibrations in the circumferential direction.

By extracting the rotation of the rotor section 2 to the outside, an ultrasonic drive motor using the piezoelectric body 5 is realized.

Now, as shown in FIG. 5, the driving surface 6 of the stator section 1 has a ring shape, and a large number of grooves 11 are formed radially on the surface thereof. Grooves 11 are generally provided in member 7 of stator section 1 . Generally, the grooves 11 reduce the Q value of vibration of the stator section 1.

However, by giving the groove a specific shape, the Q value can be increased without decreasing it. In other words, it is possible to increase the output of the ultrasonic drive motor.
(The resonance frequency of the vibration of the stator part used in an ultrasonic drive motor depends on the thickness of the stator part and the vibration wavelength. Therefore,
If the vibration wavelength is constant, increasing the thickness of the stator member increases the driving force. However, since the vibration width decreases,
Simply increasing the thickness of the stator member does not lead to an increase in efficiency.

Here, in order to increase efficiency without increasing power, it is effective to provide grooves in the stator section under certain conditions.

FIG. 6 shows an enlarged view of the groove structure of the stator section, which is located on the basic part of the stator section with a thickness of t.

A convex portion having a thickness t2 is provided.

The basic characteristics of the stator section are mostly determined by the basic section having a thickness of t4. Now the thickness of the base part is t, and the thickness of the convex part is t
2, the stator portion is increased by the thickness t3. However, by appropriately selecting the thickness t2 and width ρ2 of the convex portion provided on the upper part of the stator portion, it is possible to prevent the convex portion from affecting the vibration of the basic material at all.

Now, let f be the resonance frequency determined by the thickness t2 and width a2, and let f2 be the fundamental frequency determined by the thickness t8 and diameter of the basic material, then set t so that fl is equal to f2.
If you select zpax - each convex part N□J2T
Since N3... vibrates in the same phase as the vibration of the basic part, the vibration amplitude increases. The amount of increase is determined by the ratio of t21tl. If N engineering 1N2tN3...
If ....... vibrate independently of each other, then
The effect of the protrusion of thickness t2 is eliminated, but if a matched resonant frequency is selected, the thickness of t2 can be increased practically 100% without loss.

Furthermore, by changing the material of the convex part, L + tztρ2 (density).

The same effect can be obtained by appropriately selecting C2 (elastic constant).

Furthermore, instead of providing a concave groove, convex portions may be arranged on the ultrasonic vibrator basic material so that the groove is formed. Further, the width of the groove portion is preferably shorter than a half wavelength of the vibrating body, and preferably in a direction perpendicular to the wavefront.

(Effects of the Invention) As explained above, according to the present invention, it is possible to obtain an ultrasonic drive motor that is more efficient than the conventional one with the same electric power, and furthermore, the stator member is divided into two vibrating parts. This has the effect of increasing the degree of freedom in a wide range of designs.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an ultrasonic drive motor according to an embodiment of the present invention, FIG. 2 is a sectional view of the same, and FIG. 3 is a side view of the excitation part.
FIG. 4 is a side view of the same operating state, FIG. 5 is a detailed perspective view of the excitation section, and FIG. 6 is an enlarged view of a part of the stator section. 1...Stator part, 2...Rotor part, 3
... Stator fixing base, 4 ... Stator support part,
5...Piezoelectric body, 6...Drive surface, 7...
Member forming a driving surface, 8...excitation part, 9.
... Driven surface, 10 ... Rotating shaft, 11 ... Groove. Patent applicant: Matsushita Electric Industrial Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] An ultrasonic drive motor comprising an ultrasonic vibrating body having a driving surface, and a driving surface contacting body that comes into contact with the ultrasonic vibrating body and extracts a part of the vibration as external motion. A plurality of grooves each having a concave cross section are provided on the drive surface, and the resonant frequency of the convex portion generated by the formation of the grooves is adjusted to the resonance frequency of the basic portion of the ultrasonic vibrator having the drive surface excluding the convex portion. An ultrasonic drive motor characterized by having a resonance frequency equal to the resonance frequency.