JPS61277380A - Ultrasonic wave motor - Google Patents

Abstract

PURPOSE:To prevent heat from being generated and improve the efficiency of a motor, by forming piezoelectric transducers in a nodal circle with a radius of approx. 5/6 of that of an elastic unit. CONSTITUTION:The first disc-shaped piezoelectric transducer 1 is provided with eight divided electrodes 1a, and is polarized in different polarities electrode by electrode in the direction of the disc thickness. The second piezoelectric transducer 2 is also formed in the same way, and the electrode transition at the minimum amplitude position of the piezoelectric transducer 2 is positioned near the center of the electrode at the maximum amplitude position of the piezoelectric transducer 1, and both transducers are put together. An elastic unit 3 forming a stator by fitting the piezoelectric transducers 1, 2 is provided with the projection 4 of an oscillation-transmitting member and a central shaft 5, and a rotor 14 is fitted to organize an ultrasonic wave motor. Then, both the piezoelectric transducers 1, 2 are formed in the maximum outer diameter at a nodal circle position with a radius of approx. 5/6 considering the diameter of the elastic unit 3. As the result, by the ultrasonic wave oscillation of the both piezoelectric transducers 1, 2, effective oscillation only can be excited in the elastic unit 3, and the efficiency can be enhanced.

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 body of this kind is disclosed in, for example, Japanese Unexamined Patent Publication No. gF+59-39801 (as shown in FIG. 4). .

That is, the stator 6' is constructed by stacking two circular piezoelectric vibrators 11.2) and one circular elastic body 3 in the thickness direction.
and a circular rotor 14 in surface contact with the stator 6'.
The piezoelectric vibrator 1 has a ring-shaped protrusion 4 for applying vibrational energy to the surface of the stator 6'.
Rotating force is obtained by applying electrical signals that are out of phase with each other to / and 2/.

Problems to be Solved by the Invention However, with this type of structure, when an electric signal of a predetermined drive frequency is applied to excite mechanical vibration, the stator 6r generates heat, resulting in poor motor efficiency. . This is due to the following reasons.

W...I have plotted the distribution of longitudinal strain when a higher order mode is excited in a disc-shaped vibrator. The phase is reversed at the border. If one disk-shaped elastic body 3 and two disk-shaped piezoelectric vibrators 1/ and 2/ are laminated with the same dimensions without considering the phase relationship of vibrations, as in the conventional example, approximately 5/6 It will be the outside of the radius. The area corresponding to about 25 mm of the piezoelectric vibrator will perform an ineffective drive in the opposite direction to the effective vibration, resulting in generation of unnecessary vibration, heat generation due to loss, and reduction in efficiency. Ta.

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

Means for Solving the Problem The piezoelectric vibrator is constructed within a nodal circle having a radius of approximately 5/6 of the elastic body.

The ultrasonic vibration of the vibrator that serves as the working stator can excite only effective vibration in one elastic body (does not drive the region where the phase is reversed), so it generates approximately 25% of the total input signal so far. occupy The energy consumed to prevent vibrations caused by regions of opposite phase is no longer required, and it is now possible to obtain the same mechanical output with approximately half or less of the electrical input compared to the conventional example, which is several times more efficient. It is possible to improve efficiency to some extent.

Embodiments Below, one embodiment 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 11L are provided, which are divided into regions of 46 degrees, for example. This voltage 1& is formed on the surface of the first piezoelectric vibrator 1 using a conductive material such as silver. The electrode (not shown) provided on the back surface is divided like the front electrode. The entire surface is electroded. For each adjacent electrode of the first piezoelectric vibrator 1 configured as described above.

Polarization is performed so that the dividing directions are different from each other in the plate thickness direction. As a result, as shown in FIG.
It consists of poles and four sets of oscillators. The electrodes 1a do not need to be divided after one minute, and are connected so that voltage can be applied all at once. The disk-shaped second piezoelectric vibrator 2 also
It has the same structure as the 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. and.

Both piezoelectric vibrators 1 and 2 are superimposed so that the boundary between adjacent electrodes, which is the minimum amplitude position of the second piezoelectric vibrator 29, is located near the center of the electrode, which is the maximum amplitude position of the first piezoelectric vibrator 1. ing.

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 metal such as aluminum, brass, and stainless steel. Further, on the surface of the elastic body 3 serving as the stator, there are protrusions 4, which are vibration transmitting members, located in the vicinity of a position corresponding to approximately % of the diameter, for example. A shaft 5 is formed at the center.

Moreover, the first piezoelectric vibrator 1 and the second piezoelectric vibrator 2 are as follows.

Approximately 5/6 of the diameter of the elastic body 3 (for example, 40M)
A disk-shaped piezoelectric body whose maximum outer diameter is at the nodal circle position (for example, 33jljr) serving as the radius is used, and is provided only in the positive direction vibration part of the vibration in the direction of the new surface of the link cuff.

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 driving frequency determined by the stator 6 is branched, one side is directly connected to the amplifier 8K, and the other side is connected to the phase shifter 9.
input to amplifier 1° via. The phase shifter 9 has an angle of ±10° or ± used for forward or reverse rotation.
The signal is shaped with a phase shift within a range of 170°. The output signal of the oscillator 7 is directly input to the amplifier 8, and the amplified signal is passed through the lead wires 11 and 12 to the first piezoelectric actuator 1.
to be applied. As a result, the stator 6 has eight poles and four
Excitation waves of four wavelengths corresponding to the set of vibrators are generated. The second piezoelectric vibrator 2 also leads the output of the amplifier 1o m12,1
It is similarly driven by applying it through 3.

When the stator 6 is driven as described above, the apex of the vibration on the side of the stator 6 facing the rotor 14 comes into contact with the rotor 14, and the apex moves with time.
A force having a lateral component will be applied to the rotor 14. Thus, the rotor 14 repeatedly moves in position due to the lateral component according 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.

The contact position between the stator and rotor at this time is stator 6.
This is near the apex of the positive displacement portion (for example, upward direction) of the vibration in the cross-sectional direction of the link cuff.

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. 50
When V is applied, 1 in the vicinity of the protrusion 4 which is the vibration transmission member.
The maximum amplitude was approximately 8 μm. The phase turning point of the amplitude, the so-called vibration node (nodal circle), changes almost linearly from 80 to 90%, assuming the diameter is 100%, and the end has an amplitude of about 2.6 μm. It became. From these facts, in the stator 6, the deformation order of the second mode of one disk is 4.
It can be seen that it is excited by the following higher-order vibration mode. Furthermore, when the electrical signal application lead wires 11, 12, and 13 were brought out from near the vibration nodal circle, 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 5-disk-shaped bulk wave is excited by direct means to obtain a lateral component that becomes a thrust. Since the output 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 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 cross-sectional view showing an outline of an ultrasonic motor using the same stator and rotor, and its drive circuit, and FIG. This figure shows the strain distribution when the ultrasonic motor stator shown in FIGS. 1 and 2 is driven, and FIG. 4 is an exploded perspective view of the conventional ultrasonic motor. 1.2... Piezoelectric vibrator, 11L... Electrode, 3... Elastic body, 4... Protrusion, 6...
...Stator, 14...Rotor, 7...
...Oscillator, 8.10...Amplifier, 9...
...Phase shifter. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 4

Claims (2)

[Claims] (1) Equipped with a stator consisting of an elastic body and an electro-mechanical transducer, and a rotor in contact with the stator, the electro-mechanical transducer generates a vibration wave that travels in the circumferential direction, and The ultrasonic motor is characterized in that the elastic body is provided in a range where the deflection vibrations of the elastic body are in the same direction. (2) The ultrasonic motor according to claim 1, characterized in that the electro-mechanical transducer having a disk shape is provided within a nodal circle of a higher-order vibration mode of the flexural vibration of the elastic body. .