JPH0197179A - Supersonic motor - Google Patents

Abstract

PURPOSE:To improve abrasion resistance and durability, by employing aluminum for a moving body and forming a porous anode oxidation film onto the surface at driven side then impregnating with lubricant. CONSTITUTION:A supersonic motor comprises a moving body 11, made of aluminum or an alloy thereof, a resilient vibration body 12 having excellent abrasion resistance and thermal expansion characteristic similar with that of a piezoelectric element 13, a piezoelectric vibration chip 13, a vibration absorbing member 16 composed of felt and a fixing table 17. A porous anode oxidation film 11a containing lubricant is formed on the surface of the moving body 11 at driven side. In the film 11a, a gamma oxidized aluminum layer 23 containing countless thin holes 24 is placed through a barrier layer 22 onto aluminum base 21, and blocks 23a are laminated through cracks 23b. Consequently, high hardness and abrasion resistance are provided to the aluminum layer 23.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an ultrasonic motor that generates traveling elastic waves in an elastic vibrating body and drives a moving body using the traveling elastic waves.

[Conventional technology]

An ultrasonic motor converts ultrasonic vibrations generated in a piezoelectric element or an electrostrictive element into mechanical vibration energy, which is used as driving energy for the motor. Such ultrasonic motors have characteristics that conventional electromagnetic motors do not have, such as low speed, high torque, high responsiveness, small size and light weight, and therefore, applied research is being actively conducted in various industrial fields. Several types of ultrasonic motor drive methods have been proposed at present. , a motor configured to generate a standing wave by the vibration of at least one piezoelectric element or electrostrictive element will be described. FIG. 4 shows the driving principle of this type of ultrasonic motor, where 1 is a moving body and 2 is an elastic vibrating body. The X-axis indicates the traveling direction of surface waves generated on the surface of the elastic vibrating body 20, and the Z-axis indicates the normal direction thereof. When the elastic vibrator 2 is vibrated by a piezoelectric element (an electrostrictive element may also be used), not shown, a surface acoustic wave is generated and propagates on the elastic vibrator 2. This elastic wave is a surface wave with longitudinal waves and transverse waves, and its mass point moves in an elliptical motion. Here, if we pay attention to the mass point A, it is performing an elliptical motion with a vertical amplitude U and a lateral amplitude W, and if the traveling direction of the surface wave is the +X direction, the elliptical motion is rotating counterclockwise. This surface wave has vertices A, A... for each wavelength, and its apex velocity is only the X component, V = 2πfu (however, f
is the frequency of vibration). Therefore, when the movable body 1 is brought into pressure contact with the elastic vibrating body 2 in the direction of the arrow P, the surface of the movable body 1 contacts only the vertices A, A, etc. It is driven in the direction of arrow N by the frictional force between them. The moving speed of the moving body 1 in the direction of the arrow N is proportional to the frequency f. Furthermore, since frictional drive is performed by pressurized contact, it depends not only on the longitudinal amplitude U but also on the lateral amplitude W. That is,
The moving speed of the moving body 1 is proportional to the size of the elliptical motion,
The greater the elliptical motion, the greater the movement speed. Therefore, the moving speed is also proportional to the voltage applied to the piezoelectric element. FIG. 5 shows the principle of generating surface waves in the elastic vibrating body 2 shown in FIG. 3a and 3b are piezoelectric elements, such as PZT, attached to the elastic vibrating body 2 at intervals that allow the most efficient acquisition of elastic waves from the resonance frequency of the elastic vibrating body 2; 3a is attached to the conductor A, and 3b is attached to the conductor B. are connected to each. Reference numeral 4 denotes a driving power supply, which supplies a voltage of V=Vosinωt. As is clear from the diagram, conductor A has ■
=■. A sine wave voltage of sinωt (where ω is the angular frequency and t is time) is applied to the conductor B through a 90° phase shifter 5, and ■=■. A voltage of 5 inches (ωt±π/2) is applied. + and - are switched depending on the moving direction of the moving body. That is, the moving direction of the moving body differs depending on whether the phase is shifted by +90° by the 90° phase shifter 5 or when the phase is not shifted by -90°. In FIG. 5, (a) to (d) show the vibration state of the elastic vibrating body 2 according to time, and (a) shows t=2nπ/ω, (
b) is t=π/2ω+2nπ/ω, (C) is t=π/ω
+2nπ/ω, (d) is the state of t=3g/2ω+2nz/ω. Although the elastic wave propagates to the right in the figure, any mass point on the surface of the elastic vibrating body 2 performs an elliptical motion in the counterclockwise direction, as described above. Therefore, the moving body (not shown) that is pressed against the surface of the elastic vibrating body 2 moves to the left. FIGS. 6 and 7 show an example of an ultrasonic motor constructed based on the above-mentioned driving principle. In the figures, 1 is a moving body (
2 is an elastic vibrating body, 3 is a piezoelectric element, 6 is a vibration absorbing member, and 7 is a mounting base. Elastic vibrator 2, piezoelectric element 3
and the vibration absorbing member 6 are integrally configured by being bonded to each other,
It is fixed to the mounting base 7. Further, the moving body 1 is brought into pressure contact with the elastic vibrating body 2 by appropriate means. In the ultrasonic motor configured as described above, when a voltage is applied to the piezoelectric element 3 to generate a traveling elastic wave on the surface of the elastic vibrating body 2, the elastic wave is brought into pressure contact with this surface via the friction body 1a. The moving body 1 is driven and rotates. The vibration absorbing member 6 is used to fix the piezoelectric element 3 and the elastic vibrating body 2 to the mounting base 7, and is made of felt or the like to prevent the influence of vibration between the piezoelectric element 3 and the elastic vibrating body 2 and the mounting base 7. Made of material that absorbs vibrations.

[Problems to be solved by the invention]

As explained above, an ultrasonic motor works between a moving body and an elastic vibrating body (the driving force is transmitted by frictional force), so the characteristics of the material of the frictional contact surface of the ultrasonic motor It greatly affects mechanical output performance and service life.The characteristics required of the materials that make up both of these are as follows: (1) A large coefficient of friction and the ability to efficiently convert vibration energy into rotational energy. (2) It has excellent abrasion resistance and does not abrade the mating material it comes in contact with (elastic vibrating body or moving body). (3) Can be precisely machined and is thermally and chemically stable. (4) Stable operation can be maintained over a long period of time with little change over time.Therefore, in conventional ultrasonic motors, it has been proposed that the driving part of the elastic vibrator be provided with a wear-resistant lining. There are also examples where the body is made of metal and the driven part of the moving body is made of hard rubber. In either case, the idea is to increase the frictional force and increase durability. However, However, it is not easy to achieve both of these objectives, and further improvements are required.
It is an object of the present invention to provide an ultrasonic motor that has significantly improved durability by being configured to have a stable and large coefficient of friction.

[Means to solve the problem]

The present invention provides an ultrasonic motor that drives the moving body by bringing the moving body into pressure contact with an elastic vibrating body and generating traveling elastic waves on the surface of the elastic vibrating body. Using this alloy, an anodic oxidation porous film is formed on the driven side surface, and the anodic oxidation porous film is impregnated with lubricating oil.

[For use]

According to this invention, the gamma-type aluminum oxide forming the upper layer of the anodized porous coating is hard and has high wear resistance, and acts to increase the frictional force between the moving body and the elastic vibrating body. To efficiently convert vibration energy into rotational energy. Furthermore, the oil impregnated into the porous portion acts as a lubricant, minimizing wear on the mating material, the elastic vibrator. Furthermore, since aluminum or its alloy, which is lightweight among metals, can be used as the moving body, loss of driving force is reduced, and a more efficient ultrasonic motor can be obtained.

【Example】

Hereinafter, the present invention will be explained in detail based on the drawings. In FIG. 1, 11 is a moving body made of pure aluminum or its alloy, lla is an anodized porous coating containing lubricating oil formed on the driven side surface of this moving body 11, and 12 is a resistant material such as metal or hard plastic. An elastic vibrating body made of a material with excellent abrasion resistance and having almost the same thermal expansion characteristics as a piezoelectric element, 13 a piezoelectric element, 16 a vibration absorbing member made of felt or the like, and 17 a mounting base. FIG. 2 is a partially enlarged perspective view showing the cross-sectional structure of the anodized porous coating 11a in FIG. 1. As shown in FIG. 2, the anodized porous coating 11a has a gamma-type aluminum oxide layer 23 containing countless pores 24 on an aluminum base 21 with a barrier layer 22 interposed therebetween. As shown in the cross-sectional view in FIG. 3, the gamma-type aluminum oxide layer 23 is in a state in which massive blocks 23a are stacked with cracks 23b interposed therebetween. The properties of such an anodized porous coating 11 vary slightly depending on the type of acid electrolyte and the anodizing conditions, but can be controlled with high precision within the following range. Barrier layer thickness: 10~500 gamma aluminum oxide layer thickness: 0.5"~100
μm Pore diameter: 100 to 3000 people Area ratio of pores per unit area: 4.5 to 38% The above gamma type aluminum oxide is the same as alumina oxide, which is known as structural ceramics, so it is hard and wear-resistant. It is wear resistant and has excellent corrosion resistance. However, when used in this state, the mating material is abraded due to its hardness, which deteriorates the durability of the ultrasonic motor. It was found that this problem could be overcome by impregnating the porous portion with lubricating oil, leading to the completion of the present invention. The porous portion can be impregnated with oil by immersion in lubricating oil heated to around 100° C. under normal pressure. By this treatment, the lubricating oil permeates not only the pores 24 but also the cracks 23b, so that the amount of oil necessary for lubrication can be preserved. The impregnated oil oozes out onto the surface of the movable body 11 by a kind of pumping action caused by sliding between the movable body 11 and the elastic vibrating body 12 only when the movable body 11 rotates, and performs a lubricating effect. When the movable body 11 stops, the oil on the surface is absorbed into the original oil-bearing pores by capillary action, so that it does not contaminate the surrounding area. Therefore, the lubrication effect can be achieved without external oil supply. In the above embodiments, the present invention was applied to a rotary type motor, but it is of course applicable to a linear type motor.

【Effect of the invention】

The ultrasonic motor of the present invention uses aluminum or its alloy for the moving body, has an anodic oxidation porous coating formed on the driven side surface, and impregnates this anodized porous coating with lubricating oil, so that (1) The increased hardness of the driven portion of the movable body and the lubricating effect of the impregnated oil improve the wear resistance of the movable body and the elastic vibrating body, thereby improving the durability of the ultrasonic motor. (2) The efficiency of the ultrasonic motor is improved because the moving body is lighter and the conversion of vibrational energy into rotational energy is improved. (3) It is easy to maintain the dimensional accuracy of the moving body, and the characteristics of the ultrasonic motor are stable. (4) Various materials can be selected for the elastic vibrator. You can obtain effects such as

[Brief explanation of the drawing]

FIG. 1 is an assembled sectional view of an embodiment of the present invention, FIG. 2 is a partially enlarged perspective view showing the structure of an anodic oxidation porous coating of aluminum, and FIG. 3 is a partially enlarged sectional view of the porous portion in FIG. 2. Figure 4 is an explanatory diagram explaining the principle of an ultrasonic motor, Figure 5
The figure is an explanatory diagram illustrating the principle of surface wave generation of the elastic vibrator in Figure 4, Figure 6 is an exploded perspective view showing the configuration of a conventional ultrasonic motor, and Figure 7 is an assembled cross-sectional view of Figure 6. be. 11: Moving body, 11a: Anodized porous film, 12: Elastic vibrating body, 13: Piezoelectric element, 16: Vibration absorbing member, 17:
Mounting base. Figure 1 Figure 4 Figure 2/1 Figure 3 Figure 5 Figure 6/ Country 7

Claims (1)

[Claims] 1) In an ultrasonic motor that drives the moving body by bringing the moving body into pressure contact with an elastic vibrating body and generating traveling elastic waves on the surface of the elastic vibrating body, the moving body is made of aluminum or an alloy thereof. 1. An ultrasonic motor characterized in that an anodized porous coating is formed on the driven side surface of the ultrasonic motor, and the anodized porous coating is impregnated with lubricating oil.