JPS61196773A - Piezoelectric motor using rollers - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

[Conventional technology]

In conventional piezoelectric motors, a moving torque is usually applied to the moving element by directly pressing the sliding surface of the moving element onto the end face of the stator which is undergoing ultrasonic vibration. At this time, the movable element moves in one direction every cycle in accordance with the amplitude of the ultrasonic wave on the order of microns.

In other words, the contact points with the stator move in one direction every half cycle of ultrasonic vibration, and in the next half cycle, those contact points move away from the mover, move in the opposite direction, and return to their original state. ,
At this time, the movement of the moving child stops. In other words, the mover repeats intermittent motion in synchronization with the ultrasonic vibrations, so it vines.

Therefore, the contact points must move and separate at the same time, but because the vibration period of the stator end face is the same but the amplitude is not uniform, some contact points tend to move quickly and strongly, while other points move slowly and slowly. Since they can only move very slowly, they brake each other, causing wear and tear, and sometimes even making a loud squeak.

[Means for solving problems]

This invention solves the above-mentioned drawbacks of the prior art.
In piezoelectric motors, the mover is directly crimped onto the stator, and the mover can be moved in a desired direction by ultrasonic vibrations generated on the end face of the stator. This objective has been achieved using a pressure-torque motor that uses rollers on the child end face and the opposing face tIJ+ of the mover.

Incidentally, in a previous application, the present inventor proposed a structure in which a rotor, that is, a roller is interposed on the circumferential surface of a cylindrical stator in which a standing wave having a wave number n of 2 or more in a torsional bending mode is generated to move a moving element. A piezoelectric motor was proposed. In this case, the antinode of the standing wave vibration is formed at the location where the circumference of the cylindrical stator is divided into 2n equal parts, and each antinode has the maximum amplitude, and the adjacent antinode vibrates in opposite phase to each other, so this occurs. Since the moving torques are also opposite to each other and cancel each other out, the moving element cannot be moved even if it is directly applied to the circumferential 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.

Embodiment 1 An embodiment of a pressure section motor using inventively rubbing rollers is shown in FIG. In the embodiment of FIG. 1, ball bearings 8 and 8' are placed as rollers between the stator end face of the conventional piezoelectric motor shown in FIGS.
This is a mechanism that transmits the generated rotational torque to the rotor 6 by being crimped onto the end face of the rotor. By adopting a structure in which this roller is interposed, wear on the sliding surfaces between the rotor 6 and the stator can be significantly reduced.

Prior to describing the embodiment shown in FIG. 1, a conventional example shown in FIG. 3 will be described in order to facilitate understanding of the present invention. Although there are various types and structures of conventional piezoelectric motors, they have a common feature: the rotor 26 is crimped to the stator, and the mechanism uses ultrasonic vibrations generated on the crimped surface to apply moving torque to the rotor. The structure is such that the mover is crimped onto the stator. In other words, since moving torque is caused by sliding due to ultrasonic vibration, friction between the mover and stator is essential to transmit large moving torque to the load, and large pressure force is required to increase friction. shall be.

Therefore, it is easy to understand the erroneous idea that the sliding surfaces of piezoelectric motors are destined to wear out.

It is well known that when an object is moved, it is generally better to use rollers to move the object than to move the object by moving it, as this results in less friction and wear. Naturally, it seems better to use rollers for piezoelectric motors as well. However, using rollers greatly reduces friction, which also has the disadvantage of not being able to transmit large amounts of torque. Therefore, in order to choose the most rational means, it is necessary to consider the mechanism of wear on the sliding surfaces of piezoelectric motors. The point of the present invention lies in this point, and we will first correct the above-mentioned erroneous way of thinking regarding the sliding mechanism of the piezoelectric motor, and clarify that the basis of this invention is not a simple idea of simply using rollers. Let me explain.

As a representative example of a conventional piezoelectric motor, the operation of a cantilever-shaped ultrasonic motor shown in FIG. 3 will be described. This piezoelectric motor has donut-shaped thickness vibrators (c) and (b) made of piezoelectric ceramics, which are connected to paper bolt holes in a support disk (21) with a single beam by means of disk-shaped metal washers (n, 25). It is constructed in one piece by tightening.

The piezoelectric vibrator and the piezoelectric vibrator both have electrodes and are polarized, so the same polarity surfaces should be placed opposite each other and the lead wire 2
It is overlapped and tightened with the terminal plates marked 3' and 24'. When a sinusoidal voltage is applied between the lead wires n' and Sae', it is converted into mechanical vibration by the piezoelectric vibrator,
Ultrasonic vibrations are generated. This vibration is a vertical vibration along the length of the bolt (9), but a bending vibration is excited in the support plate of the cantilever beam 21 via the bolt (g). The reason why bending vibration occurs in the support plate is because grooves are cut in the bottom surface of the support plate where the bolt holes are located. In other words, the bottom of the support disk has wide parallel shallow grooves left in crescent shapes at only two places along the circumference, and when it is tightened with Pol) 30, the crescents become supporting points, and Pol) 30 Due to the longitudinal vibration acting on the disk, the disk performs a bending motion with respect to the two supports.

At the top of the disk, a rectangular plate-shaped beam stands upright like a cantilever with the disk as a fixed end, but the width direction of the beam is not parallel to the groove, but at a considerable angle. When the disc undergoes bending vibration, torsional vibration occurs in the beam, and both widths of the tip of the beam vibrate in opposite phases to each other as shown in Figure 4, making the frequency of the sine wave match the natural frequency of this vibration. When you do so, it becomes resonant and vibrates violently.

Since this vibration is parasitic to the vertical vibration, both width portions of the tip of the beam undergo elliptical motion in a plane in which the locus of vibration is perpendicular to the end surface. Furthermore, the direction of this elliptical motion depends on the sign of the angle of inclination between the collar and the groove, and in the basic state, the direction of motion is clockwise when the angle of inclination is positive, and counterclockwise when it is negative.

Therefore, if the rotor 26 is placed in a layer on this end face, when the elliptical vibration component is upward, the rotor will move sideways while supporting it, and when the elliptical vibration component is downward, the rotor will be supported by the pole bearing of the axle. Because of this, it is impossible to move downward along with the cantilever beam 21, but it will be left behind and separated from the end face of the cantilever beam 21. During this time, the tip of the end surface of the cantilever beam 21 moves downward, while the component moves in the opposite direction, rises upward again, returns until it touches the rotor 26, and moves forward again when it touches the rotor.

What is notable about this movement is that the contact surfaces of the rotor and stator remain stationary relative to each other. It goes without saying that moving a large load requires strong vibrations that resist the strong crimping force, but there is no place for friction. The rotor and stator surfaces are relatively stationary when in contact, and the force supporting the moving torque is static friction. Therefore, there is no way that the movable surface (even this word "sliding" is inappropriate) will wear out. This is an important point in principle of piezoelectric motors.

On the other hand, when we conducted a lifespan test, we found that even during no-load operation, the sliding surface wears unevenly in the center, sometimes even producing a squeak. This cannot happen between two objects that are stationary. The reason for this was elucidated by considering the vibration of the stator end face. The above-mentioned deadlock theory is based on the case where the vibration of the beam is uniform torsional vibration, and the first corner of the end face of the beam has a size proportional to the length of the diameter with the center as the axis, that is, a constant angle from the center. It was assumed that this would be the case, especially in the case of free vibration without a rotor attached to the tip.

However, the actually measured amplitude was complex as shown in FIG. 4 and was by no means uniform. The arrows indicate the direction and magnitude of the amplitude with the amplitude measuring point as the root. What should be noted is that the amplitudes differ even on the same circumference at the same distance from the center, and generally the amplitude tends to be larger towards the end of the arrow on the end face. The reason for this is unknown, but if this were to be elucidated and ultrasonic elliptical vibrations of uniform amplitude could be realized, there would be no wear on the holding surface.

When viewed from the rotor rotating at a constant speed, there is no wear if the contact surface with the stator is simultaneously driven with a torque that provides a constant angular velocity. Wear occurs because the angular velocity of the contact part varies from place to place, and in severe cases it even produces a squeaking sound.

We found that the distribution of angular velocity is not uniform when viewed on the same circumference, but on the same diameter it is almost uniform in proportion to the length of the diameter, and that the angular velocity differs depending on the diameter.

For this reason, to avoid wear, it is undesirable to make surface contact between the rotor and the stator, and furthermore, it is worst to make line contact in the form of a band along the circumference (concentric band form) as in the case of conventional cantilever-type piezoelectric motors. It was found that this would lead to a situation of On the other hand, as far as wear is concerned, it is believed that a line contact along the diameter would be optimal. Therefore, a structure using the present invention was created.

First, FIG. 1 will be explained as the simplest embodiment. There is a diameter of 1° and a thickness of 3° between the cantilever beam 1 and the rotor 6 of the conventional pressure-tortoise motor shown in FIG.

Equipped with 8.8I ball bearings with four inner diameters. These bearings 8,8' are supported by a shaft 9 so as to be in contact with the tip end surface of the cantilever beam along one radius, and the shaft 9 is further fixed to the shaft 7 so as not to rotate away from this radius. There is. The shaft 7 is a four-piece cap bolt that fits into the internal hollow part of the shaft 6' of the rotor 6.
The rotor 61 is supported by a bearing 8.8' press-fitted into the center of the bottom of the disc. These 70 heads of cap bolts are located inside the shaft portion 6' of the rotor 6, and a coil spring is inserted between the heads and the bearings.

After fitting the tip of the cap bolt 7 into the hole at the center of the end surface of the cantilever beam 1 (see hole 21a in FIG. 4) and tightening it until the rotor 6 touches the desired diameter of the end surface of the cantilever beam 1,
Pass the anti-rotation pin through the tip of the cap bolt 7. At this time, it must be strongly pressed to the tip of the cantilever beam 1 by the force of the coil spring through the bearing 8° 8' halo taro.

In addition, 2 in the figure is a disk washer, 3 and 4 are piezoelectric thickness vibrators,
5 is a washer for the cap bolt. 3'#4' is a lead wire.

In this way, an embodiment of a piezoelectric motor using the rollers according to the present invention was completed, and when connected to a power source, it rotated smoothly and without noise, and withstood long life tests without wear. . In this case, the lifespan is the lifespan of the bearing itself, which is probably not more than 1 degree. What's more, surprisingly, a surprisingly large and strong torque output was obtained.

Embodiment 2 In Embodiment 1, a bearing was used as the simplest example, but since ordinary ball bearings have the same outer diameter, an increase in wall thickness would be inconvenient. That is, since the angular velocity of vibration at the end face of the cantilever beam is substantially uniform along the diameter, the linear velocity increases toward the outer periphery. If a thick bearing is used, since the peripheral speed is constant, there will be a discrepancy in the rotational speed between the inner and outer circumferences, causing wear. In order for the rollers arranged along the diameter to rotate at a constant speed, the diameter of the rollers must taper toward the inside of the diameter. Stripe 2 shows tapered spindle-shaped roller 1
8 and 18'.

In this figure, ll is a cantilever beam, 12 is a circle & gankin, 13° 14 is a piezoelectric thickness vibrator, 15 is a washer for a cap bolt,
16 is a rotor, 17 is a cap bolt, 18 and 18' are rollers, and 13' and 14' are lead wires.

At the tip of the cantilever beam 11, a groove with a taper that is thicker than the diameter of 18.18' is carved like a rain gutter, and the bottom surface of the rotor 160 is not horizontal, but is tapered into a cone shape. Therefore, the contact between rotor 1b and 18° 18' is sufficient to transmit a large torque. Because of the gutter-like groove at the tip of the cantilever beam 11, the rollers 18 and 18' do not protrude from the groove even if the shaft is not fixed, and the rollers 18 and 18' always roll in a state where the angular velocity of vibration is in contact with the constant tangent line. The narrow tip of roller 18.18' has a constriction, and the corresponding groove has a band-like protrusion along the roundness of the groove, and the constriction of roller 18.18' fits into this in a columnar manner. Therefore, it does not protrude in the radial direction while rolling. Note that the taper of the roller is not necessarily straight, but may be curved in order to match the linear speed. All of the above examples are representative examples in which rollers are interposed between the rotor and stator of a cantilever-shaped piezoelectric motor, but other types of rotary motors and linear motors also suffer from wear and tear due to the interposition of rollers. Needless to say, it provides smooth rotation without any creaks.

〔Effect of the invention〕

As explained above, the present invention provides a piezoelectric motor in which the mover is directly crimped onto the stator and the mover can be moved in a desired direction by ultrasonic vibrations generated on the end face of the stator. As a means for generating and transmitting the vibration, the piezoelectric motor is constructed using rollers between the end face of the stator and the facing surface of the mover, so that the mover can move smoothly at a constant speed. This is extremely practical in that it eliminates the causes of creaks and wear caused by uneven movement speeds that occur in conventional motors in which the moving element is directly crimped without intervening rollers, making it possible to create motors with smooth movement and long life. A ha-ha effect was obtained.

[Brief explanation of drawings]

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, and FIG. 3 is a front view of a conventional piezoelectric motor. FIG. 4 is an explanatory diagram showing ultrasonic torsional vibrations generated on the stator end face of the cantilevered piezoelectric motor. 1.11... Cantilever beam, 6, 16... Rotor, 8.8'. 18.18'...Koro. Agent Patent Attorney Take Kenjibe Rinabee '71 Zusai 3n Bu Sen 1 Kasumi

Claims (1)

[Claims] 1. In a piezoelectric motor in which the mover is directly crimped onto the stator and the mover can be moved in a desired direction by ultrasonic vibrations generated on the end face of the stator, the stator end face is used as a means of generating and transmitting moving torque. A piezoelectric motor that uses rollers between the opposing surfaces of the moving element and the moving element.