JPS61277385A - Ultrasonic wave motor - Google Patents

Abstract

PURPOSE:To obtain the flat temperature characteristic of output, by using the substance of the equal coefficient of linear expansion for the piezoelectric unit and the elastic unit organizing the stator of a motor. CONSTITUTION:Eight electrodes 1a are arranged by dividing the surface of the first disc-shaped piezoelectric transducer 1, and are polarized in different polarities in the direction of the disc thickness electrode by electrode. The second piezoelectric transducer 2 is also formed in the same way, and both piezoelectric transducers are put together so that the electrode transition of the second transducer 2 may be positioned near the center of the electrode of the first transducer 1. An elastic unit 3 forming a stator by fitting the transducers 1, 2 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 elastic unit 3 and the piezoelectric transducers 1, 2 are formed by using the substance of the equal coefficient of linear expansion. For example, for the elastic unit 3, the alloy of 42% nickel is used, and for the piezoelectric transducers 1, 2, the material of three- component system is used. As the result, the characteristic of flat temperature can be obtained.

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 structure as shown in FIG. Ta. That is, the stator is constructed by stacking two circular piezoelectric vibrators 1 and 2 and a circular elastic body 3 in the thickness direction, and a circular rotor 4 is in surface contact with the stator. The piezoelectric vibrators 1 and 2 are provided with a ring-shaped protrusion 3a for applying a rotational force to the piezoelectric vibrators 1 and 2 by applying electric signals out of phase with each other.

Problems to be Solved by the Invention However, with this type of structure, the linear expansion coefficients of the elastic body that constitutes the stator and the electro-mechanical transducer such as the piezoelectric body are different, so the temperature characteristics are poor and it does not respond well to temperature changes. There was a problem that the simulator characteristics changed. This is due to the following reasons.

Figure 3 (al) shows the change in rotational speed at each temperature from 6°C to +90''C. When laminated at a temperature of
Since the size increases by about 6% of the aluminum, the stator is used with thermal stress applied at room temperature. Furthermore, at a low temperature of about -36° C., this thermal stress increases further and the mechanical amplitude of the ultrasonic motor decreases, resulting in a decrease in the rotational speed.

Means for Solving the Problems The present invention provides that the linear expansion coefficients of the elastic body and the piezoelectric body constituting the stator exhibit approximately the same coefficient of linear expansion within a relatively low temperature range of +120°C to -35°C, which is the bonding temperature. Use substances.

Function: It eliminates the heat stress that occurs during the bonding process, and also reduces the practical temperature range of ultrasonic motors (-36°C to +90°C).
℃), the temperature characteristics are poor and the shimotor characteristics do not change due to temperature changes, making it possible to obtain substantially flat rotation characteristics.

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. On the surface of the disk-shaped first piezoelectric vibrator 1, eight electrodes 1a are provided, which are divided into regions of 46 degrees, for example. This electrode 1a is formed on the surface of the first piezoelectric vibrator 1 using a conductive material such as silver. The electrodes (not shown) provided on the back surface are divided like the front electrodes to form full-surface electrodes. Polarization is performed in each adjacent electric beam of the first piezoelectric vibrator 1 configured as described above so that the polarization directions are different from each other in the plate thickness direction.

As a result, as shown in Figure 1, 8 poles, 4
A set of oscillators is configured. After polarization, the electrodes 1a 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 includes four sets of eight poles each having alternating positive or negative polarity.

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.
Minimum amplitude level 7 of the second piezoelectric vibrator 2 -- Adjacent electrodes are superimposed so that their boundaries are located.

The first piezoelectric vibrator 1 and the second piezoelectric vibrator 2 configured as described above are attached to overlap with 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 a metal such as a 42% nickel alloy. Further, on the surface of the elastic body 3 serving as the stator, a projection 3a serving as a vibration transmitting member is formed near a position having a diameter of about H, for example, and a shaft 6 is formed at the center.

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 the drive frequency determined by the stator 6 is branched, one of which is directly sent to the amplifier 8 and the other to the phase shifter 9.
is input to the amplifier 10 via. The phase shifter 9 shapes a signal whose phase is shifted within a range of ±100 to ±170°, which is used for 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 electric vibrator 1 at a first voltage through the lead wires 11 and 12. Therefore, the stator 6 is provided with excitation waves of 4 wavelengths corresponding to 8 poles and 4 sets of oscillators, with each wavelength being a pair of regions in which the polarization directions of the first piezoelectric oscillator 1 have mutually different positive polarity or negative polarity. is generated. The second piezoelectric vibrator 2 is similarly driven by applying the output of the amplifier 10 via the lead wires 12, 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, the rotor 4 repeatedly moves in position 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.

In Fig. 3(b), the elastic body is made of, for example, 42 nickel alloy (
exlo-6) is used, and a three-component material (6) is applied to the piezoelectric ceramic.
By using X10-6), etc., the temperature characteristics of the motor rotation speed using stators configured with similar linear expansion coefficients were shown. At each temperature from -35°C to +90°C, substantially flat characteristics could be obtained.

Effects of the Invention In the ultrasonic motor according to the present invention, since the elastic body and the piezoelectric body constituting the motor stator are made of materials with the same coefficient of linear expansion, there is no thermal stress and the temperature characteristics of the ultrasonic motor output are improved. We were able to achieve almost flat characteristics.

[Brief explanation of 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, Fig. 2 is a sectional view showing an outline of an ultrasonic motor using a stator and rotor and its drive circuit, and Fig. 3 1 is a diagram showing the temperature characteristics of the ultrasonic motor shown in FIGS. 1 and 2, and FIG. 4 is an exploded perspective view of the conventional ultrasonic motor. 1.2... Piezoelectric vibrator, 1a... Electrode, 3... Elastic body, 3a... Protrusion, 4...
...Rotor, 6...Pyster, 7...
・Oscillator, 8, 10...Amplifier, 9...
・Phase shifter. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Onten (first time)

Claims (2)

[Claims] (1) A stator consisting of an elastic body and an electro-mechanical transducer, and a rotor in contact with the stator, and the elastic body and the vibrator of the stator are constructed using materials whose linear expansion coefficients are approximately the same. An ultrasonic motor characterized by: (2) The ultrasonic motor according to claim 1, wherein the electro-mechanical transducer is made of a piezoelectric material.