JPH0640746B2 - Piezoelectric motor using rollers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field and Object of the Invention] The present invention relates to an improvement in a sliding mechanism of a piezoelectric motor, and an object thereof is to provide a piezoelectric motor having excellent wear resistance.

[Conventional technology]

In the conventional piezoelectric motor, it is usual to apply a moving torque to the moving element by directly crimping the sliding surface of the moving element to the end surface of the stator that is vibrating ultrasonically. At this time, the mover moves in one direction every cycle with the amplitude of ultrasonic waves of about micron. That is, the contact point with the stator moves in one direction for each half cycle of ultrasonic vibration, and those contact points move away from the mover in the next half cycle and move in the opposite direction to return to the original state. At this time, the movement of the mover is stopped. In other words, the mover repeats intermittent movements synchronized with ultrasonic vibrations.

Therefore, the contact points must move at the same time and move away from each other at the same time.However, because the vibration period of the stator end face is the same, the amplitude is not uniform, so that one contact point tries to move fast and large, and another point is slow and small. Not being able to move, they brake each other and cause wear, and sometimes even a loud squeaking noise is produced.

[Means for solving problems]

This invention solves the above-mentioned drawbacks of the prior art.
In a piezoelectric motor in which the moving element can be moved in a desired direction by ultrasonic vibration generated on the end surface of the moving element, the moving element is fixed as a means for generating and transmitting moving torque. The object is achieved by a piezoelectric motor characterized by using rollers between the child end surface and the facing surface of the moving element.

In the prior application, the inventor of the present invention has a structure in which the rotor, that is, the roller is interposed on the peripheral surface of the cylindrical stator in which the standing wave having the wave number n of the torsion bending mode is 2 or more is moved. A piezoelectric motor was proposed. In this case, antinodes of standing wave vibrations are formed at portions where the circumference of the cylindrical stator is equally divided into 2n, and the antinodes are generated because they have the maximum amplitude and the adjacent antinodes vibrate in mutually opposite phases. Since the moving torques cancel each other out in the opposite directions, they cannot move even if the moving element is directly pressed against the peripheral surface without using rollers. Therefore, it goes without saying that this prior application is not included in the present invention.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

Example 1 Example 1 of a piezoelectric motor using a roller according to the present invention
Shown in the figure. In the embodiment shown in FIG. 1, ball bearings 8 and 8'are placed between the stator end surface of the conventional piezoelectric motor shown in FIG. This is a mechanism for transmitting the rotating torque to the rotor 6. By adopting the structure in which the rollers are interposed, the wear of the sliding surface between the rotor 6 and the stator can be remarkably improved.

Prior to the description of the embodiment shown in FIG. 1, the conventional example shown in FIG. 3 will be described to facilitate understanding of the present invention. Although there are various types and structures of conventional piezoelectric motors, they have a common feature because they are a mechanism that crimps the rotor 26 to the stator and gives moving torque to the rotor 26 by ultrasonic vibration generated on the crimping surface. Is a structure in which the mover is crimped to the stator. That is, since the moving torque is a sliding movement due to ultrasonic vibration, friction between the mover and the stator is indispensable for transmitting a large moving torque to the load, and a large crimping force is required to increase the friction. And
Therefore, the erroneous idea that the sliding surface is destined to wear in the piezoelectric motor is easily understood.

It is well known that, when an object is moved, it is less frictional and less abraded when the object is moved than when it is rolled. Of course, it seems better to use rollers for the piezoelectric motor. However, when using rollers, friction is greatly reduced, and a large torque cannot be transmitted. Therefore, in order to select the most rational means, it is necessary to consider the mechanism of wear of the sliding surface in the piezoelectric motor. The point of the present invention lies in this point, and the above-mentioned erroneous idea regarding the sliding mechanism of the piezoelectric motor is corrected, and the basic point of the present invention is not a simple idea that only the use of rollers is necessary. Let me tell you.

As a typical example of the conventional piezoelectric motor, the operation of the cantilever ultrasonic motor shown in FIG. 3 will be described. In this piezoelectric motor, doughnut-shaped thickness oscillators 23 and 24 made of piezoelectric ceramic are bolted through disc-shaped metal washers 22 and 25.
It is integrally constructed by tightening at 30 toward the bolt hole at the bottom of the support disk 21 of the cantilever.

Since the piezoelectric vibrators 23 and 24 both have electrodes and are polarized, they are made to face each other with the same polarity, and the lead wire 2
It is tightened by stacking with the terminal plate with 3'and 24 '. When a sinusoidal voltage is applied between the lead wires 23 'and 24', it is converted into mechanical vibration by the piezoelectric vibrator and ultrasonic vibration is generated. Although this vibration is vertical vibration along the length of the bolt 30, bending vibration is excited on the support plate of the cantilever 21 via the bolt 30. The bending vibration occurs in the support plate because the groove is formed on the bottom surface of the support plate where the bolt holes are formed. That is, the bottom surface of the support disk has a wide parallel shallow groove left in a crescent shape at only two places along the circumference, and when tightened with a bolt 30, the crescent part becomes a support point and acts on the bolt 30. Due to the vertical vibration, the disc makes a bending motion with respect to the two supporting portions.

At the top of the disc, a rectangular plate-shaped beam stands upright like a cantilever with the disc as the fixed end, but since the width direction of the beam is not parallel to the groove and forms a considerable angle, When the disk vibrates flexurally, torsional vibration occurs in the beam, and the width of both ends of the beam is
As shown in the figure, they vibrate in opposite phases, and when the frequency of the sine wave is matched with the natural frequency of this vibration, a resonance state occurs and violent vibration occurs.

Since this vibration is parasitic to the vertical vibration, both width portions at the tip of the beam have an elliptical motion in the plane where the locus of vibration is perpendicular to the end face. Moreover, the direction of this elliptical motion depends on the positive / negative of the tilt angle between the beam and the groove, and the motion direction in the basic state is clockwise when the tilt angle is positive and counterclockwise when the tilt angle is negative.

Therefore, if the rotor 26 is crimped to this end face, it moves laterally while supporting the rotor 26 when the elliptical vibration component is upward, and when the elliptical vibration component is downward, the rotor 26 is supported by the ball bearing of the axle. Therefore, they cannot be lowered together, and they are left away from the end surface of the cantilever 21. During this time, the tip of the end surface of the cantilever 21 moves downward, while the lateral component moves in the opposite direction to the previous one, rises upward again and returns until it contacts the rotor 26, and when it contacts the rotor 26, it advances again.

It should be noted in this movement that the rotor and stator contact surfaces remain stationary with respect to each other. Of course, to move a large load, strong vibration that resists a strong crimping force is required, but there is no place to rub. The surfaces of the rotor and the stator are relatively stationary when they are in contact with each other, and the force that supports the moving torque is static frictional force. Therefore, the sliding surface (even the word "sliding" is not valid) should not wear out. This is an important point in principle of the piezoelectric motor.

On the other hand, when actually performing a life test, the sliding surface is actually severely worn even at no load operation, and sometimes even a squeak noise is emitted. It is something that cannot happen between stationary objects. The reason for this has been clarified by considering the vibration of the end face of the stator. The above-mentioned static friction theory is the case where the vibration of the beam is a uniform torsional vibration, and the amplitude of the end face of the beam is proportional to the length of the diameter with the center as the axis, that is, it swings at a constant angle from the center. In particular, it was supposed that this would be the case for free vibration, especially without a rotor at the tip.

However, the measured amplitude was complicated as shown in FIG. 4 and was never uniform. The direction and magnitude of the amplitude are indicated by arrows with the measurement point of the amplitude as the root. What should be noticed is that the amplitudes are different even on the same circumference separated by the same distance from the center, and in general, the amplitude tends to increase toward the end of the arrow on the end face. The reason for this is unknown, but if this is clarified and ultrasonic elliptical vibration of uniform amplitude can be realized, the sliding surface will not be worn.

When viewed from the rotor that rotates at a constant speed, there is no wear if the contact surface with the stator is simultaneously driven with a torque that gives a constant angular velocity. The wear occurs because the angular velocity of the contact portion varies from place to place, and in severe cases, even a squeak noise occurs.

We found that the distribution of angular velocities was not uniform when viewed on the same circumference, but it was almost uniform on the same diameter in proportion to the length of the diameter, and the angular velocity varied depending on the diameter. For this reason, it is not preferable to bring the rotor into surface contact with the stator in order to avoid wear, and it is worst to make line contact in a strip shape (concentric strip shape) along the circumference like the conventional cantilever type piezoelectric motor. Was found to cause the situation. On the other hand, as far as the point of wear is concerned, it is considered that the line contact along the diameter may be optimal. Therefore, a structure using the time of the present invention was born.

First, FIG. 1 will be described as the simplest embodiment. Ball bearings 8 and 8'having a diameter of 10 mm, a thickness of 3 mm and an inner diameter of 4 mm are arranged between the cantilever 1 and the rotor 6 of the conventional piezoelectric motor shown in FIG. These bearings 8, 8 '
Is supported by a shaft 9 so as to be in contact with the tip surface of the cantilever along a diameter, and the shaft 9 is fixed to the shaft 7 so as not to turn around this diameter. The shaft 7 is a 4 mm cap bolt which passes through the inner hollow part of the shaft 6'of the rotor 6 and supports the rotor 6 by bearings 8 and 8'pressed into the center of the bottom of the disk. The head of the cap bolt 7 is in the shaft 6'of the rotor 6, and a coil spring is inserted between the head and the bearing.

The tip of the cap bolt 7 is fitted into the hole at the center of the end face of the cantilever 1 (see hole 21a in FIG. 4), and the rotor 6 is tightened until it comes in contact with the desired diameter of the end face of the cantilever 1, and then the cap bolt. Insert the rotation stop pin through the tip of 7. At this time, the bearings 8 and 8'must be strongly pressed to the tip of the cantilever 1 by the force of the coil spring through the rotor 6.

In the figure, 2 is a disk washer, 3 and 4 are piezoelectric thickness oscillators,
5 is a cap bolt washer, and 3'and 4'are lead wires.

Thus, one embodiment of the piezoelectric motor using the rollers according to the present invention was completed, and when connected to a power supply, it smoothly operated without noise, and it was extremely smooth and did not wear and withstand a long life test. . It is no exaggeration to say that the life in this case is the life of the bearing itself. Surprisingly, a surprisingly strong torque output was obtained.

Example 2 In Example 1, a bearing was used as the simplest example. However, since a normal ball bearing has the same outer diameter, it becomes inconvenient if the wall thickness increases. That is, since the angular velocity of vibration at the end surface of the cantilever is substantially uniform along the diameter, the linear velocity increases toward the outer circumference. If a thick bearing is used, the peripheral speed is constant, so that the rotational speed is deviated between the inner circumference and the outer circumference, causing wear. In order for the rollers arranged along the diameter to rotate at a constant speed, they must be tapered so that the diameter of the roller becomes smaller toward the inside of the diameter. Fig. 2 shows spindle-shaped rollers with taper
Figure 9 illustrates an embodiment using 18 and 18 '.

In this figure, 11 is a cantilever, 12 is a disk washer, 13 and 14 are piezoelectric thickness oscillators, 15 is a washer for cap bolts, 16 is a rotor, 17 is cap bolts, 18 and 18 'are rollers, 13', 14'
Is a lead wire.

At the tip of the cantilever 11, a tapered groove that is slightly thicker than the diameter of the rollers 18 and 18 'is also carved like a rain gutter, and the bottom of the rotor 16 is not horizontal but has a cone-shaped taper. Therefore, the contact with the rotor 16, 18 and 18 'is also sufficient to transmit a large torque. Because of the gutter-shaped groove at the tip of the cantilever 11, the rollers 18 and 18 'do not jump out of the groove even if the shaft is not fixed, and always roll in a state in which the angular velocity of vibration is in contact with a tangent line. , The rollers 18,18 'have a narrowed end, and the corresponding groove has a strip-shaped convex part along the roundness of the roller. Because it fits, it does not protrude in the radial direction while rolling. In addition, the taper of the roller is not always limited to a straight line, and may be a curved face in order to match the linear velocity. Each of the above examples shows a typical example in which rollers are interposed between the rotor and the stator of the cantilever piezoelectric motor.
Needless to say, in the case of other types of rotary motors and linear motors as well, intervening rollers provide smooth rotation without wear or squeaking.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY As described above, according to the present invention, the moving torque is directly applied to the stator, and in the piezoelectric motor in which the moving element can move in a desired direction by the ultrasonic vibration generated on the end surface of the stator, the moving torque is reduced. As a means for generating and transmitting, the piezoelectric motor is characterized by using rollers between the stator end surface and the facing surface of the moving element, so that the moving element can move smoothly at a constant speed. It is possible to eliminate the cause of squeak or wear due to uneven movement speed, which occurs in conventional motors that directly crimp the mover without rollers.
The practically extremely important effect of being able to make a smooth movement and a long-life motor was obtained.

[Brief description of drawings]

FIG. 1 is a front view of a piezoelectric motor according to a first embodiment of the present invention,
FIG. 2 is a front view of a piezoelectric motor according to a second embodiment of the present invention,
FIG. 3 is a front view of a conventional piezoelectric motor, and FIG. 4 is an explanatory view showing ultrasonic torsional vibration generated on the end face of a stator of a cantilever piezoelectric motor. 1, 11 ...... cantilever, 6, 16 ...... rotor, 8, 8 ', 18,
18 '... around.

Claims (1)

[Claims] 1. A means for generating and transmitting a moving torque in a piezoelectric motor in which a moving element can be moved in a desired direction by ultrasonic vibration generated on an end surface of the fixing element by directly crimping the moving element to the stator. As a piezoelectric motor, a roller is used between the end surface of the stator and the facing surface of the mover.