JP2543055B2 - Vibration wave drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration wave driving device, and more particularly to improvement of a frictional contact portion between a vibrating body thereof and a moving body which makes pressure contact with the vibrating body.

BACKGROUND OF THE INVENTION In general, a vibration wave motor includes a ring-shaped vibrating body made of an elastic material and a rotor (moving body) having a ring-shaped surface that is in pressure contact with the surface of the vibrating body. By arranging and fixing piezoelectric elements, electrostrictive elements, etc. on the other surface of the vibrating body, and applying an AC voltage to these, a traveling wave composed of a transverse wave and a longitudinal wave traveling in the circumferential direction is generated in the vibrating body. Then, as a combination of both waves, a kind of elliptical motion is caused at each point on the surface of the vibrating body, which causes the rotor that is in pressure contact with the surface of the vibrating body to rub along the surface of the vibrating body. It is configured to drive and rotate.

In such a vibration wave motor, the moving body (rotor)
In order to make the contact state of the vibrating body with the good condition and improve the transmission efficiency of the friction driving force, as shown in FIG.
A rotor 1 having a flange portion 1-1 that comes into contact with the ring-shaped vibrating body 2 at the ring-shaped contact portion 3 is used, and good pressure contact with the vibrating body 2 is achieved by elastic deformation of the flange portion 1-1. It has been proposed (JP-A-61-224882). However, no particular consideration was given to the optimum size of the contact portion 3, and the transmission efficiency of the friction driving force was still unsatisfactory. In addition, the phenomenon that the present inventor called an adsorption phenomenon occasionally occurred. The adsorption phenomenon is a phenomenon in which the elastic deformation of the flange portion 1-1 is integrally resonated so as to be drawn into the vibration of the vibrating body 2, and when this occurs, the vibration mode of the vibrating body 2 changes and the vibration suddenly changes. It stops, and of course, the motor drive also stops.

[Object of the Invention]

SUMMARY OF THE INVENTION It is an object of the present invention to improve a contact portion between a vibrating body and a moving body in a vibration wave driving device to enhance a friction driving force transmission efficiency and prevent an occurrence of an adsorption phenomenon.

[Outline of Invention]

The vibration wave driving device of the present invention is a vibration wave driving device that generates a vibration wave and relatively rotates the vibrating body and a contact body in contact with the vibrating body by the vibrating wave. One of the contact parts of the contact body and the contact body is formed as a linear protrusion having a line width of 0.5 mm or less, and the other is formed as a plane orthogonal to the axial direction of the rotational movement. .

Example of Invention

The vibration wave motor is essentially a motor that moves by friction drive, and the driving force of the vibration wave motor is the rotor (moving body).
Depends on the product μW of the pressing force W that makes the pressure contact with the vibrating body and the dynamic friction coefficient μ between the rotor and the vibrating body. Pressure W
It is considered that the driving force is increased by increasing, but if the pressing force W is excessively increased, the vibration of the vibrating body is suppressed, and the driving force is decreased. Therefore, it is necessary to select a material having a large dynamic friction coefficient μ for the materials of the vibration body and rotor of the vibration wave motor.

By the way, it is known that frictional contact with a vibrating object is quite different from normal frictional contact without vibration. For example, Kan et al.'S paper ("Lubrication", Vol. 25, No. 4, 2
(Page 40, 1980), the coefficient of dynamic friction in the frictional contact of a vibrating object is lower than that in the absence of vibration. The present inventor paid attention to this point and conducted some experiments. The details and results of the experiment are described below.

FIG. 4 is a diagram showing the friction tester used in the experiment. The fixed side friction test material 4 and the rotating side friction test material 5 are weights 6
Are pressed by each other, and are in pressure contact with each other at the contact portion 5-1. The rotating side friction test material 5 is fixed on the rotating table 7, and the rotating table 7 is rotated by the motor 16 through the shaft 13. The fixed-side friction test material 4 is fixed to a disc 8, and a shaft 9 is attached to the disc 8. The shaft 9 is supported by a bearing 10 so that it can freely rotate and move up and down. An arm 11 is fixed to the shaft 9, and a torque measuring device 12 also serving as a rotation stopper is provided at the end of the arm 11. Now, when the rotating side friction test material 5 is forcibly rotated by the prime mover 13, the fixed side friction test material 4 also produces a rotational force due to friction. This friction torque can be measured as a friction torque by the torque measuring device 12. The dynamic friction coefficient μ between the stationary side friction test material 4 and the rotating side friction test material 5 is calculated by dividing the measured friction torque by the average radius of the contact portion 5-1 and further by the weight of the weight 6. You can

Although the above description is the same as that of a general friction tester, in this tester, the piezoelectric element is further provided on the upper surface of the fixed side friction test material 4.
The feature is that 14 is joined. Electrodes (not shown) are provided on both upper and lower surfaces of the piezoelectric element 14, and each electrode is connected to a high frequency power supply 15. That is, in this friction tester, while applying vibration to the fixed side friction test material 4,
The dynamic friction coefficient μ can be measured.

In this friction test, vibration was applied while changing the width of the contact portion 5-1 between the rotating side friction test material 5 and the fixed side friction test material 4 in various ways. Fixed side friction test material 4 has an outer diameter of 46 mm and an inner diameter of 3
Using 8 mm 4-6 brass, the friction test material 5 on the rotating side was made of aluminum (A5056), and several materials having different widths of the contact portion 5-1 were used. Further, the contact portion of both test materials was polished to a mirror surface state and tested. The weight 6 has a weight of 700 gr, and a sixth-order out-of-plane bending vibration (vibration causing bending vibration displacement in the direction perpendicular to the surface of the ring-shaped test material 4, that is, in the axial direction) is applied to the fixed-side friction test material 4 at about 43 KHz. Was generated at the resonance frequency of, and the maximum amplitude was about 0.6 μm. It should be noted that these values are selected to be substantially equal to those of the actual vibration wave motor. The results of the friction test conducted under the above conditions are shown in Table 1.

Table 1 shows the dynamic friction coefficient μ measured by changing the width of the contact portion 5-1 of the rotating side friction member 5. As is clear from the table, when no vibration is applied, μ = 0.33, which is independent of the contact width. However, when vibration is applied to the fixed side friction member 4, the state changes completely. That is, it can be seen that μ increases as the contact width increases. Especially when the contact width is 4 mm, μ =
If this contact width is applied to a vibration wave motor, the driving force will be significantly reduced. On the other hand, if the contact width is 0.5 mm or less, μ can have a value of 80% or more as compared with the case where there is no vibration, which can be considered as a substantially satisfactory value of μ.

This phenomenon is because the air film acts as a lubricant as a result of air being trapped in the contact portion due to vibration and reduces μ, and it is considered that the larger the contact width, the greater the effect.

It was also confirmed in this experiment that the above-mentioned adsorption phenomenon disappears when the contact width becomes 0.5 mm or less. The reason for this is not clear, but when the contact width becomes as small as 0.5 mm, the fixed-side friction member (vibrating side) and the rotating-side friction member (vibrated side) become structurally dissimilar, and vibration on the vibrating side occurs. It is conceivable that the vibrated side will be less likely to be pulled in.

As mentioned above, if the contact width is set to 0.5 mm or less,
The dynamic friction coefficient μ is almost the same as when there is no vibration (80% or more), and the adsorption phenomenon does not occur. Therefore, if this is applied to the frictional contact portion of the vibration wave motor, a stable vibration wave motor having a large driving force can be obtained.

FIG. 1 and FIG. 2 are views showing an embodiment of the present invention, respectively. In FIG. 1, the end portion of the rotor (moving body) 1 is narrowed to have a width.
A linear contact portion 3-1 of 0.5 mm or less is obtained. In FIG. 2, a protrusion having a small width is provided on the upper portion of the vibrating body 2 to obtain a linear contact portion 3-2 having a width of 0.5 mm or less.

If the contact width is set to 0.5 mm or less, a stable vibration wave motor with a high driving force can be reliably obtained.
New problems also arise. The reason is that if the contact width is set to 0.5 mm or less, the contact surface pressure becomes extremely large, which increases the amount of wear due to friction. This causes a reduction in the durability and life of the vibration wave motor. FIG. 3 shows an embodiment of the vibration wave motor of the present invention devised to solve this problem. In the figure, a plurality of frictional contact portions between the rotor 1 and the vibrating body 2 are provided linearly with a width of 0.5 mm or less like the contact portions 3-3, 3-4, 3-5. By doing so, the surface pressure per contact portion can be reduced, and a vibration wave motor having high durability and long life can be obtained.

〔The invention's effect〕

According to the present invention, the frictional contact portion of the vibration wave driving device has a width of 0.5 mm or less. According to the present invention, (1) it is possible to obtain a vibration wave driving device having a large driving force while preventing the dynamic friction coefficient from decreasing.

(2) The adsorption phenomenon can be prevented, the drive device does not suddenly stop, and a stable vibration wave drive device can be obtained.

If the frictional contact portion is formed into a plurality of linear lines with a width of 0.5 mm or less, in addition to the above effects (1) and (2), the surface pressure of the contact portion is reduced, wear is reduced and durability is high. It is possible to obtain a vibration wave driving device having a long life.

Also, since the mating surface that comes into contact with the linear protrusion with a line width of 0.5 mm or less is a plane that is orthogonal to the axial direction of the rotational movement, the contact position of the linear protrusion is stable and can be greatly displaced. There is no.

[Brief description of drawings]

1, 2, and 3 are side sectional views showing respectively different embodiments of the vibration wave driving device of the present invention, and FIG. 4 is a diagram showing the constitution of the friction tester used in the experiment of the present invention. FIG. 5 is a side sectional view showing a conventionally proposed vibration wave motor. 1 ... Rotor (moving body), 2 ... Vibrator 3-1,3-2,3-3,3-4,3-5 ... Contact part

Claims (2)

(57) [Claims] 1. A vibration wave drive device for generating a vibration wave and relatively rotating the vibration body and a contact body in contact with the vibration body by the vibration wave. An oscillatory wave drive device characterized in that one of the contact portions of the two is formed into a linear protrusion having a line width of 0.5 mm or less, and the other is a plane orthogonal to the axial direction of the rotational movement. 2. The vibration wave drive device according to claim 1, wherein a plurality of linear contact portions having a line width of 0.5 mm or less are provided.