JPS61277386A - Ultrasonic wave motor - Google Patents

Abstract

PURPOSE:To prevent heat from being generated and improve the efficiency of a motor, by reversing the polarization of piezoelectric units set at the position confronting a nodal circle, at the angle of 180 deg. in the direction of the thickness. CONSTITUTION:The surface of the first disc piezoelectric transducer 1 is provided with eight divided electrodes 1a and 1b, and is polarized in different polarities electrode by electrode. The second piezoelectric transducer 2 is also formed in the same way, and both transducers are put together so that the electrode transition of the second piezoelectric transducer 2 may be positioned near the center of the electrode of the first piezoelectric transducer 1. An elastic unit 3 forming a stator by fitting the transducers is provided with the projection 3a of an oscillation-transmitting member and with a central shaft 5, and a rotor 14 is fitted to organize an ultrasonic wave motor. In this case, the polarization of the sections of electrodes 1b outside the nodal circle of the transducers 1, 2 is reversed at the angle of 180 deg.. As the result, the point of the rotor 14 in contact with the stator is positioned near the peak of the positive-directional displacement section of the flexible oscillation of the stator, and mechanical displacement is enlarged and thrust can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a motor that generates driving force using an electro-mechanical transducer such as a piezoelectric body.

2. Description of the Related Art A conventional motor using an electro-mechanical transducer such as a piezoelectric material has a configuration as shown in FIG. was.

That is, it includes a stator formed by stacking two circular piezoelectric vibrators 1 and 2 and a circular elastic body 3 in the thickness direction, and a circular rotor that makes surface contact with the stator. It has a ring-shaped protrusion 3a for applying energy, and rotational force is obtained by applying electrical signals out of phase with each other to the piezoelectric vibrators 1 and 2.

Problems to be Solved by the Invention However, with such a structure, there is a problem in that when an electric signal of a predetermined drive frequency is applied to excite mechanical vibration, the stator generates heat, resulting in poor motor efficiency.

This is due to the following reasons.

The distribution of strain in the direction perpendicular to the plane when high-order mode flexural vibration is excited in a disc-shaped vibrator is 1gI-
However, the phase of the displacement due to deflection is reversed at the nodal circle which is approximately 6/6 radius.

Unlike the conventional example, without considering the phase relationship of vibration,
When a disc-shaped elastic body and two disc-shaped uniformly polarized piezoelectric vibrators are pasted together with the same dimensions, the area outside the approximately 6/6 radius, which corresponds to about 26 inches of the piezoelectric vibrator, is ,
An ineffective drive in the opposite direction to the effective vibration results in generation of unnecessary vibration, heat generation due to loss, and reduction in efficiency.

Therefore, the present invention aims to improve motor efficiency by preventing heat generation without exciting ineffective ultrasonic vibrations.

Means for solving the problem The polarization direction of the piezoelectric material in the vibrator is set to about 6/6 of the stator.
6. The polarization directions of the piezoelectric body within the nodal circle serving as the radius and the piezoelectric body provided at a position facing the nodal circle (outside the nodal circle) are reversed by 1800 degrees in the thickness direction.

Function: In this configuration, the ultrasonic vibration of the vibrator that becomes the stator can excite effective vibration in the same direction as the deflection in the entire region (the region where the phase is reversed is driven in that direction), which is different from the conventional method. It accounts for about 25% of the total input signal,
Since the energy consumed by being canceled out by the opposite phase effectively contributes to the forward vibration component, it is possible to obtain the same mechanical output with less than half the electrical input compared to the conventional example. Efficiency can be increased several times.

Embodiments Hereinafter, embodiments of the present invention will be described based on the accompanying drawings.

The stator of an ultrasonic motor has a structure as shown in FIG. 1, for example. The surface of the disk-shaped first piezoelectric vibrator 1 is provided with eight electrodes 1a divided into, for example, 460 areas, and eight electrodes 1b similarly divided on the outside. These electrodes 1a and 1b are made of a conductive material such as silver,
It is formed on the surfaces of the first piezoelectric vibrator 1 and the second piezoelectric vibrator 2. The electrodes (not shown) provided on the back surface are divided like the front electrodes to form full-surface electrodes. Polarization is performed so that the polarization directions of adjacent electrodes of the first piezoelectric vibrator 1 configured as described above are different from each other in the thickness direction. As a result, as shown in FIG. 1, eight sets of vibrators with 16 poles each consisting of regions having alternately positive or negative polarity are constructed. Electrode 1
After polarization, a and 1b do not need to be divided, and are connected so that a voltage can be applied all at once. The disk-shaped second piezoelectric vibrator 2 has the same structure as the first piezoelectric vibrator 1, and has 16 poles having alternately positive or negative polarity, 8. A set of transducers is configured.

The minimum amplitude position of the longitudinal amplitude in the circumferential direction of the first piezoelectric vibrator 1 or the second piezoelectric vibrator 2 is near the boundary position between adjacent electrodes, and the maximum amplitude position is near the center of each electrode. Become. Both piezoelectric vibrators 1 and 2 are placed near the center of the electrode, which is the maximum amplitude position of the first piezoelectric vibrator 1.
The first piezoelectric vibrator 1 and the second piezoelectric vibrator 2 configured as described above are overlapped so that the boundary between adjacent electrodes is located at the minimum amplitude position of the second piezoelectric vibrator 2. It is attached to overlap an elastic body 3 having a thickness equal to or about 100 times that of the piezoelectric vibrator. This elastic body 3 is formed using metal such as aluminum, brass, and stainless steel. Further, on the surface of the elastic body 3 serving as the stator, a protrusion 3a serving as a vibration transmitting member is formed in the vicinity of a position corresponding to, for example, approximately % of the diameter, and a shaft 6 is formed at the center.

Further, the electrode arrangement in the radial direction of the first piezoelectric vibrator 1 and the second piezoelectric vibrator 2 is based on the diameter of the elastic body 3 (for example, 40 W'II
), the nodal circle position is about 5/6 radius (for example, 331
111) is the maximum outer diameter. For example, it consists of a region of positive direction vibration and a plurality of regions of, for example, negative direction vibration across the nodal circle, and the directions of polarization thereof are arranged so as to be different from each other.

The structure constructed as described above is used as the stator 6 shown in FIG. As shown in FIG. 2, the output signal oscillated by the oscillator 7 at a driving frequency determined by the stator 6 is branched, one of which is sent to a direct amplifier 8, and the other to an amplifier 1° via a phase shifter 9. input. The phase shifter 9 shapes a signal whose phase is shifted within the range of ±100 to ±17oO for use in forward or reverse rotation.

The output signal of the oscillator 7 is directly input to the amplifier 8, and the amplified signal is applied to the first piezoelectric vibrator 1 through lead wires 11 and 12. As a result, the stator 6 has 8 poles in the circumferential direction, with 4 wavelengths corresponding to 4 sets of oscillators, with a pair of regions in which the polarization directions of the first piezoelectric vibrator 1 have mutually different positive polarity or negative polarity as one wavelength. An excitation wave is generated. The second piezoelectric vibrator 2 is similarly driven by applying the output of the amplifier 10 through the lead wires 12 and 13.

When the stator 6 is driven as described above, the apex of the vibration on the side of the stator 6 facing the rotor 4 comes into contact with the rotor 4, and since the apex moves with time, a force having a lateral component is applied to the rotor 4. will be added. As a result of the rotor 4 repeating positional movement due to the lateral component due to the drive frequency determined by the stator 6,
It is possible to obtain rotational motion in the range of several to several thousand revolutions per minute. At this time, the contact position between the stator and the rotor is near the apex of the displacement portion of the stator 6 in the positive direction (for example, in the upward direction) of the flexural vibration. FIG. 3 shows the results of measuring the distortion in the vertical direction when the stator 6 according to the present invention is driven by applying an electric signal, as a change in the cross-sectional direction of the stator 6' shown in a virtual image. When soV was applied, a maximum amplitude of 1.8 line type was exhibited near the protrusion 4, which is a vibration transmission member. The phase turning point of the amplitude, the so-called vibration node (nodal circle), is 80% if the diameter is 100%.
The position from ~90 inches changes almost linearly, and the amplitude at the end is about 2.6 μm. From these facts, it can be seen that the stator 6 is excited by a higher-order vibration mode in which the deformation order of the second-order mode of the disk is fourth. In addition, a lead wire 11.1 for applying an electric signal from the vicinity of the vibration nodal circle
After testing 2 and 13, there was no disconnection due to vibration fatigue.

Effects of the Invention The ultrasonic motor according to the present invention has a structure in which a disk-shaped bulk wave is excited by direct means to obtain a lateral component that becomes a thrust. Since the speed is doubled and the entire deflection in the cross-sectional direction is output, it is possible to extract the peak speed without averaging the speed. Furthermore, the heat generation is low and the motor efficiency is high.

[Brief Description of the Drawings] Fig. 1 is an exploded perspective view of the stator and rotor of an ultrasonic motor according to an embodiment of the present invention, and Fig. 2 is an outline of an ultrasonic motor using the stator and rotor and its drive circuit. FIG. 3 is a diagram showing strain distribution during driving of the ultrasonic motor stator of FIGS. 1 and 2, and FIG. 4 is an exploded perspective view of a conventional ultrasonic motor. 1.2... Piezoelectric vibrator, 1a... Electrode, 3... Bullet 20-ta, 7... Oscillator,
8,1°...Amplifier, 9...Phase shifter. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure WS2 Figure 4

Claims (2)

[Claims] (1) A stator comprising an elastic body and an electro-mechanical conversion vibrator, and a rotor in contact with the stator, wherein the electro-mechanical conversion vibrator of the stator is configured to vibrate in the positive direction and in the negative direction of the flexural vibration of the stator. Consists of multiple areas of the vibrating part,
An ultrasonic motor characterized in that the driving directions of the plurality of regions by voltages of the same polarity are different from each other. (2) The ultrasonic wave according to claim 1, characterized in that the electro-mechanical conversion vibrator of the circular stator is divided into regions inside the nodal circle and outside the nodal circle according to a higher-order vibration mode. motor.