JPH0632573B2 - Ultrasonic motor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor driven by utilizing ultrasonic vibration of a piezoelectric body.

2. Description of the Related Art Generally, an ultrasonic motor has a structure in which a vibrating body to which a piezoelectric body is fixed and a moving body are in pressure contact with each other, and an ultrasonic wave as shown in FIG. A traveling wave of sonic vibration is generated, and the moving body is driven by the frictional force with the moving body.

In FIG. 3, reference numeral 1 is a piezoelectric body, and the vibrating body 2 is adhered and fixed to the surface thereof. Further, 3 is a moving body, in which the friction material 4 is integrated. With this configuration, when an electric input is applied to the piezoelectric body 1, ultrasonic vibration (a traveling wave in the A direction) is generated in the piezoelectric body 1 and the vibrating body 2, and an elliptic motion like B is generated at each mass point of the vibrating body 2. Occur. Here, each wave front of the traveling wave has a property of moving in the direction opposite to the traveling wave direction A, and each trough of the traveling wave has a property of moving in the same direction as the traveling wave direction A. Therefore, the object (the friction material 4 and the moving body 3) placed on the surface of the vibrating body 2 contacts only the upper portion of the wave front, 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 the maximum.

In general, the vibrating body and the moving body are in pressure contact with each other, and in order to obtain a larger motor output, it is possible to increase the pressing force between the vibrating body and the moving body and increase the friction coefficient between the vibrating body and the moving body. is necessary. However, if the applied pressure is too strong, the friction material is likely to be worn and the vibration of the vibrating body tends to be suppressed.

Metals such as iron, stainless steel, and aluminum are used as the material of the vibrating body and the moving body, and a composite resin including inorganic fibers and a resin is used as the material of the friction material.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, when a composite resin composed of an inorganic fiber and a resin is used as the friction material as in the above-mentioned conventional example, due to the friction of the vibrating body and the moving body with the elapse of the driving time of the ultrasonic motor. A large amount of wear powder is generated on both the vibrating body and the moving body, and the wear powder adheres to the contact surfaces of the vibrating body and the moving body. There is also a problem that the frictional force between the vibrating body and the moving body when no electricity is input) changes with time.

In addition, there is a problem that the optimum resonance frequency of the vibrating body part varies with time due to the influence of the abrasion powder attached to the vibrating body, and stable driving of the motor cannot be obtained.

The present invention solves 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 comprises:
A friction material made of a plastic material containing at least an organic fiber, a fluorocarbon resin and a matrix resin is fixed to at least one surface of the vibrating body facing the moving body.

Action As the friction material uses a composite plastic material in which organic fibers and fluorocarbon resin powder are bonded with a matrix resin, the wear amount of the friction material itself can be significantly reduced, and the contact partner of the friction material is worn And a stable friction coefficient can be obtained.

Embodiment One embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a piezoelectric body, on the surface of which a metallic vibrating body 2 is adhered and fixed. Reference numeral 3 denotes 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 in pressure contact with each other by the fastening force. Here, when a high frequency electric field having a resonance 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 is separated from the vibrating body. It is driven integrally with the moving body 3 by the frictional force. When no electric power is input, a holding torque, that is, a braking force, which corresponds to the product of the pressure applied between the vibrating body 2 and the friction material 4 and the friction coefficient, is generated.

As described above, by using the composite plastic friction material composed of the organic fiber, the fluorocarbon resin powder, and the matrix resin, it is possible to obtain stable friction force and brake torque during long-term driving of the ultrasonic motor. , Little change in the resonance frequency of the vibrator over time,
It will start up reproducibly and will be able to drive stably.

As the organic fibers, aromatic polyamide fibers, phenol fibers, organic polymer whiskers, polybenzimidazole fibers, ultra high molecular weight polyethylene fibers, liquid crystal plastic fibers and the like can be used. As the fluorocarbon resin powder, polymer powder such as tetrafluoroethylene and hexafluoroethylene or rubber powder can be used. As the matrix resin, polyimide, polyamideimide, epoxy resin, phenol resin, silicone resin, polyester resin, polyarylate resin, liquid crystal polymer or the like can be used. The content ratio of the organic fiber and the fluorocarbon resin powder is preferably 5 weight% or more at the same time.

As the friction material used in the present invention, in addition to the organic fiber and the fluorocarbon resin powder, other inorganic or metallic fillers may be added and contained.

Next, the present invention will be described in more detail with reference to specific examples.

Example 1 As shown in Table 1, various organic fibers, fluorocarbon resin powder, and matrix resin were uniformly dispersed, and each composite plastic friction material sheet molded to a thickness of 1 mm was used to obtain a diameter of 40 mm and a thickness of 1 mm. It is adhered to the stainless disk of No. 1 and the change over time of the dynamic friction coefficient of the friction material surface is measured. To measure the change with time of the dynamic friction coefficient, the disk to which the above friction material was adhered was rotated at a rotation speed of 30 rpm, a stainless ball with a diameter of 3 mm was brought into contact with a position 15 mm from the center, and a load of 200 g was applied to the stainless ball. The friction coefficient between the surface of the friction material and the stainless ball was measured.

Table 2 shows the changes over time in the dynamic friction coefficient when each of the friction materials was used, and Tables 1 and 2 also show the material compositions and friction coefficients of the friction materials containing no fluorocarbon resin powder.

As is clear from Table 1 and Table 2, all of the composite plastic friction materials composed of the organic fiber, the fluorocarbon resin powder and the matrix resin have a large friction coefficient of 0.2 or more, and the friction coefficient hardly changes with time. It wasn't recognized.

On the other hand, in the case of the friction material containing no fluorocarbon resin powder (Comparative Examples F and G), the friction coefficient greatly fluctuated over time. Further, in the case of the friction material containing no organic fiber (Comparative Example H), almost no change in the friction coefficient with time was observed, but the friction coefficient was very small.

Example 2 Using each of the friction materials A to H used in Example 1,
In FIG. 3, which constitutes a disc type ultrasonic motor as shown in FIG. 3, reference numeral 1 is a piezoelectric body, and a vibrating body 2 made of stainless steel is adhered and fixed to the surface thereof. Reference numeral 3 denotes a stainless steel moving body, 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 500 g · cm by pressing the spring. Further, an electrode is arranged on the piezoelectric body so that four traveling waves are excited in the circumferential direction of the disk, and
An electric field having a resonance frequency of 0 KHz is applied to drive the moving body at an unloaded speed of 500 rpm.

For each motor that made up each friction material sheet, the result of measuring the presence or absence of restart when the power was turned off and on after driving for a predetermined time, the brake torque after power off and the resonance frequency It shows in Table 3.

As is clear from Table 3, in the case of the ultrasonic motor using the friction material composed of the organic fiber, the fluorocarbon resin powder and the matrix resin (Experiment Nos. A to E), the change of the brake torque with time is small for all the motors. . Further, the change in resonance frequency with time was small, and there was no problem in restartability. Further, scarring wear of the stainless steel vibrating body as the contact partner was hardly recognized.

On the other hand, in the case of the motor using the friction material containing no fluorocarbon resin powder (Experiment Nos. F and G), the brake torque fluctuates greatly and the resonance frequency also fluctuates, which prevents the moving body from restarting. there were.

Further, in the case of the motor using the friction material (Experiment No. H) containing no organic fiber, the moving coefficient did not drive because the friction coefficient was too small.

Example 3 A disc type ultrasonic motor similar to that of Example 2 was constructed by using friction materials (thickness: 1 mm) having the content ratios of the organic fiber and the fluorocarbon resin powder as shown in Table 4, The resonance frequency electric field was applied in the same manner as in Example 2 to drive the motor.

For each motor that made up each friction material sheet, the result of measurement of the quality of restart when the power is turned off and on after driving for a predetermined time, the brake torque after power off and the resonance frequency is shown. It shows in Table 4.

As is clear from Table 4, when a friction material having a composition in which the content of the organic fiber is 5% by weight or more and the content of the fluorocarbon resin powder is 5% by weight or more (Experiment No. K, L, M), The change in brake torque over time is small for both motors. Further, the change in resonance frequency with time was small, and there was no problem in restartability.

On the other hand, when the content of the fluorocarbon resin powder is 2% by weight or less (Experiment Nos. I and J), the brake torque may change greatly with time, and the resonance frequency may also change significantly, which may prevent restartability. It was When only fluorocarbon resin powder is contained without organic fiber (Experiment No. N), if a brake torque of more than 200 g-cm is applied, the motor will not operate and a large output cannot be obtained. The wear of 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 formed of a plastic material containing at least an organic fiber, a fluorocarbon resin, and a matrix resin as a friction material, and the friction material is By fixing to at least one of the surfaces facing each other, it is possible to reduce wear of the ultrasonic motor, and to reduce the change over time of the brake torque and the change over time of the resonance frequency of the vibrating body.
An ultrasonic motor with stable motor start-up and excellent long-term reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of the main part of an ultrasonic motor according to an 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 body, 4 ... Friction material.

Claims (2)

[Claims] 1. An ultrasonic motor for driving a moving body by bringing a moving body into pressure contact with a vibrating body that generates a traveling wave by vibrating a piezoelectric body, and driving the moving body via a frictional force between the vibrating body and the moving body. In, a friction material made of a plastic material containing 5% by weight or more of organic fiber, 5% by weight or more of fluorocarbon resin, and a matrix resin was fixed to at least one surface of the vibrating body facing the moving body. Ultrasonic motor. 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.