JPH01110067A - Supersonic motor - Google Patents

Abstract

PURPOSE:To stabilize a starting operation and to improve long term reliability, by forming a friction member from plastic material containing organic fibers, fluorocarbon resin and matrix resin. CONSTITUTION:A supersonic motor comprises a piezoelectric member 1 and a moving body 3, where a metallic vibration body 2 is adhered onto the surface of the piezoelectric member 1 while a friction member 4 composed of organic fibers, fluorocarbon resin power and matrix resin is secured to the moving body 3. The vibration body 2 and the friction member 4 are pressure contacted through tightening force. Upon application of high frequency electric field having resonant frequency onto the piezoelectric member 1, supersonic traveling wave is produced in the piezoelectric member 1 and the vibration body 2, and the friction member 4 contacting with the surface of the vibration body is driven integrally with the moving body 3 through friction force with respect to the vibration body 2. When power is not inputted, holding torque (braking force) corresponding to a product of pressing force functioning between the vibration body 2 and the friction member and 4 friction coefficient is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an ultrasonic motor that is driven using ultrasonic vibrations produced by a piezoelectric body.

Conventional technology Generally, an ultrasonic motor has a configuration in which a vibrating body to which a piezoelectric body is fixed is brought into pressure contact with a moving body. It generates a traveling wave of ultrasonic vibration as shown in the figure, and also drives the moving body by the frictional force with the moving body.

In FIG. 3, 1 is a piezoelectric body, and a vibrating body 2 is adhesively fixed to the surface of the piezoelectric body. Moreover, 3 is a moving body, and a friction material 4 is integrated therein. With this configuration, when an electrical input is applied to the piezoelectric body 1, ultrasonic vibrations (traveling waves in the direction of the wave) are generated in the piezoelectric body 1 and the vibrating body 2, and each mass point of the vibrating body 2 forms an ellipse like B. Movement occurs. Here, each wave crest of the traveling wave has the property of moving in the opposite direction to the traveling wave direction M, and each trough of the traveling wave has the property of moving in the same direction as the traveling wave direction M.

Therefore, an object (friction material 4
The moving body 3) contacts only the top of the wave crest, and is driven in the C direction by the frictional force with the vibrating body 2.

The amplitude of this traveling wave is generally about 10 μm at maximum.

Generally, the vibrating body and the moving body are in pressurized contact, and in order to obtain a larger motor output, the pressure between the photographing body and the moving body is increased, and the coefficient of friction between the vibrating body and the moving body is increased. is necessary. However, if the pressurizing force is too strong, the friction material tends to wear out easily, and the vibration of the vibrating body tends to be suppressed. Composite resins made of inorganic fibers and resins are also used as materials for friction materials.

Problems to be Solved by the Invention However, when a composite resin made of inorganic fibers and resin is used as a friction material as in the conventional example described above, as the driving time of the ultrasonic motor passes, the friction between the vibrating body and the moving body increases. A lot of abrasion powder is generated on both the vibrating body and the moving body, and the abrasion powder adheres to the contact surfaces of the vibrating body and the moving body, so the coefficient of friction between the two changes over time, and the brake torque (
There was a problem in that the frictional force between the vibrating body and the moving body (when no electricity was being input to the motor) also changed over time0.Also, due to the influence of abrasion powder adhering to the vibrating body, the vibration force of the vibrating body There was a problem in that the optimum resonance frequency fluctuated over time, making it impossible to obtain stable motor drive.

The present invention is intended to solve the above-mentioned conventional problems, and an object of the present invention is to provide an ultrasonic motor that can always provide stable driving.

Means for Solving the Problems In order to achieve the above object, the ultrasonic motor of the present invention has the following features:
It has a structure in which at least the organic fiber and the fluorocarbon tree are fixed to one side.

Since the friction material is a composite plastic material in which organic fibers and fluorocarbon resin powder are combined with a matrix resin, the amount of wear of the friction material itself can be significantly reduced, and the friction material does not wear out the material it comes in contact with. There is no
It is possible to obtain a stable coefficient of friction.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

In FIG. 1, it is a 1Fi piezoelectric body, and a metal vibrating body 2 is adhesively fixed to the surface thereof. 3 is a moving body, and a friction material 4 made of organic fibers, fluorocarbon resin powder, and matrix resin is fixed to the moving body 3. Also,
The vibrating body 2 and the friction material 4 are brought into pressure contact by a fastening force. Here, when a high shield wave electric field with a resonant frequency is applied to the piezoelectric body 1, a traveling wave of ultrasonic vibration is generated in the piezoelectric body 1 and the vibrating body 2, and the friction material 4 in contact with the vibrating body surface vibrates. It is driven together with the moving body 3 by the frictional force with the body. Further, when no electric power is input, a holding torque, that is, a braking force corresponding to the product of the pressing force acting between the vibrating body 2 and the friction material 4 and the friction coefficient is generated.

As described above, by using a composite plastic friction material made of organic fibers, fluorocarbon resin powder, and matrix resin, it is possible to obtain stable friction force and brake torque during long-term drive of an ultrasonic motor. At the same time, there is little change in the resonant frequency of the vibrating body over time, and it is possible to start up with good reproducibility and drive stably.0 Organic fibers include aromatic polyamide fibers, phenolic fibers, organic polymer whiskers, and polybenzimidazole fibers. , ultra-high molecular weight polyethylene fiber, liquid crystal plastic fiber, etc. can be used. As the fluorocarbon resin powder, powders of polymers and rubbers such as tetrafluoroethylene and hexafluoroethylene can be used. Matrix resins include polyimide, polyamideimide, and epoxy resin.

Phenolic resin, silicone resin, polyester resin,
Polyarylate resin, liquid crystal polymer, etc. can be used.

It is desirable that the content of the organic fiber and the fluorocarbon resin powder is 6% by weight or more, respectively.

In addition to the organic fibers and fluorocarbon resin powder, the friction material used in the present invention can also contain other inorganic or metal fillers.Next, the present invention will be explained by specific examples. , will be explained in more detail.

Example 1 Various organic fibers, 70% carbon resin powder, and matrix resin as shown in Table 1 were uniformly dispersed, and each composite plastic friction material sheet was molded to a thickness of 1-1 mm, with a diameter of 40111 mm. 11111 to measure the change over time in the coefficient of dynamic friction on the surface of the friction material. To measure the change over time in the coefficient of dynamic friction, the disk to which the above friction material is bonded is rotated at a rotational speed of 3 degrees rpm, a stainless steel ball with a diameter of 3 wm is brought into contact with the disk at a distance of 15 m from the center, and a load of 20 of is applied to the stainless steel ball. The coefficient of friction between the surface of the friction material and the stainless steel ball was measured when

Table 2 shows the change over time in the coefficient of dynamic friction when each friction material is used, and Tables 1 and 2 also show a comparison of the material composition and friction coefficient of the friction material that does not contain fluorocarbon resin powder.

As is clear from Tables 1 and 2, both the organic fiber tofluorocarbon resin powder and matrix resin composite plastic friction materials have large friction coefficients of 0.2 or more, and the friction coefficients change over time. Almost no changes were observed.

On the other hand, in the case of friction materials that do not contain fluorocarbon resin powder (Comparative Examples F and G), the coefficient of friction fluctuated greatly over time. Furthermore, in the case of a friction material that does not contain organic fibers (Comparative Example H), there is almost no change in the friction coefficient over time, but the friction coefficient is very small.

Example 2 Using each of the friction materials M to H used in Example 1,
A disk-type ultrasonic motor as shown in FIG. 3 was constructed. In FIG. 3, 1 is a piezoelectric body, and a vibrating body 2 made of stainless steel is adhesively fixed to the surface of the piezoelectric body. Reference numeral 3 denotes a moving body made of stainless steel, to which each friction material sheet 4 of Example 1 is fixed.

Further, the vibrating body and the moving body are adjusted and set so that the initial brake torque is 600 g·α by applying pressure from a spring. Furthermore, electrodes were arranged on the piezoelectric material so that four traveling waves were excited in the circumferential direction of the disk, and an electric field with a resonant frequency of approximately 70 KHz was applied to the moving body at an unloaded rotation speed of 50 Or
It is driven by pm.

In addition, for each motor configured with each friction material sheet, check whether or not it restarts when the power is turned off and then turned on after being driven for a predetermined period of time.

Table 3 shows the results of measuring the brake torque and resonance frequency after the power was turned off.

(Left below) As is clear from Table 3, in the case of ultrasonic motors that use friction materials such as organic fibers, fluorocarbon resin powder, and matrix resin (experiment numbers M to R), both motors Changes in brake torque over time are small. In addition, there was little change in the resonance frequency over time, and there were no problems with restartability.

Furthermore, almost no scratches or wear on the stainless steel vibrating body, which was the contacting material, was observed.

On the other hand, in the case of a motor using a friction material that does not contain fluorocarbon resin powder (experiment number F).

G) The brake torque fluctuated greatly, and the resonant frequency also fluctuated, which sometimes made it impossible for the moving object to restart.

In addition, in the case of Tanabata using a friction material that does not contain organic fibers (experiment number H), the friction coefficient was too small and the moving object did not move.

Example 3 Friction materials (thickness 1 txs) with the content ratios of organic fiber and 70 carbon resin powder as shown in Table 4
A disk-type ultrasonic motor similar to that in Example 2 was constructed using the same method as in Example 2, and the motor was driven by applying a resonant frequency electric field in the same manner as in Example 2.

In addition, for each motor that made up each friction material sheet, check whether or not it restarts when the power is turned off and on after being driven for a predetermined period of time.

Table 4 shows the results of measuring the brake torque and resonance frequency after the power was turned off.

(Left below) As is clear from Table 4, when using a friction material with a composition containing organic fibers of 6% by weight or more and fluorocarbon resin powder content of 5% by weight or more,
(Experiment numbers: L and M) The change in brake torque over time is small for both motors. In addition, there was little change in the resonance frequency over time, and there were no problems with restartability.

On the other hand, when the content of fluorocarbon resin powder was 2% by weight or less (experiment number 1.J), the brake torque changed significantly over time, and the resonance frequency also changed significantly, resulting in a loss of restartability. Ta. When containing only fluorocarbon resin powder without organic fibers (experiment number N), if the brake torque is greater than 2009-Ql and pressure is applied, the motor will not drive and large output cannot be obtained. Furthermore, the amount of wear of the friction material is large. Effects of the Invention As is clear from the above description of the embodiments, the ultrasonic motor of the present invention is characterized in that the friction material is made of at least organic fibers, fluorocarbon resin, matrix resin, and gold. Ultrasonic motors with excellent long-term reliability and stable motor startup because they can reduce wear on the ultrasonic motor and also reduce changes over time in brake torque and changes in the resonant frequency of the vibrating body over time. is obtained.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the main part of an ultrasonic motor according to one embodiment of the present invention, Fig. 2 is a partially cutaway perspective view of another embodiment, and Fig. 3 is a main part showing the principle of the ultrasonic motor. FIG. 1... Piezoelectric body, 2... Vibrating body, 3...
...Moving object, 4...Friction material.

Claims (2)

[Claims] (1) A moving object is brought into pressure contact with a vibrating body equipped with a piezoelectric material, and a friction material made of a plastic material containing at least organic fibers, fluorocarbon resin, and matrix resin is applied between the vibrating body and the moving body. An ultrasonic motor fixed to at least one opposing surface. (2) The ultrasonic motor according to claim 1, wherein the organic fibers are at least one selected from the group consisting of aromatic polyamide fibers, phenol fibers, and organic polymer whiskers.