JP2005218191A - Ultrasonic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic motor increased in impetus, superior in durability and having a long life. <P>SOLUTION: The ultrasonic motor comprises a vibrating body 2 on the surface of which a progressive wave is generated by ultrasonic vibration generated by a piezoelectric body 1, and a movable body 3 that abuts on the vibrating body 2 and is driven by the progressive wave. The movable body 3 is constituted of an aluminum alloy of which the silicon content is less than 2% by mass, and the magnesium content is not less than 0.02% by mass and not more than 2% by mass, and an aluminum oxide coating formed by anodic oxidation treatment is applied on at least a friction surface among surfaces of the movable body. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ultrasonic motor.

  Conventionally, various ultrasonic motors are known. For example, Patent Document 1 discloses a moving body that is in contact with a vibrating body through a friction surface due to a progressive vibration wave generated in the vibrating body bonded to the piezoelectric body. An ultrasonic motor that frictionally drives the motor is disclosed. When a high-frequency voltage is applied to the piezoelectric body, the piezoelectric body emits ultrasonic vibration, and is excited by the ultrasonic vibration to vibrate the vibration body at the natural frequency. Since this vibration wave continuously travels through the vibrating body, the moving body that is in pressure contact with the vibrating body rotates by receiving a thrust so that the wave carries the object.

  Such a traveling wave type ultrasonic motor has a configuration in which an ultrasonic vibrating body (vibrating body) in which a piezoelectric body is mounted on a vibrating body and a moving body are in pressure contact with each other. The moving body is driven by the frictional force with the body. In the ultrasonic motor having such a mechanism, in order to improve the driving force of the moving body, it is necessary that the frictional force between the moving body and the vibrating body is large and the pressure contact force is large. .

  However, if the pressure contact force is too large, the vibration is suppressed and the driving force is reduced. In addition, when the moving body is deformed by the pressing contact force and the period of the vibration wave transmitted from the vibrating body is shifted, the driving force is greatly reduced. Therefore, since it is not appropriate to increase the pressure contact force, it is necessary to generate a large frictional force for the combination of the moving body and the vibrating body material in order to improve the driving force. However, generally, when materials having a large friction coefficient are rubbed with each other, the amount of wear increases. Therefore, if the moving body and the vibrating body are made of a material having a large friction coefficient, the life of the ultrasonic motor becomes very short.

For this reason, the moving body and the vibrating body are required to have a high friction surface, generate a large driving force, and have excellent durability and long life. In order to satisfy this requirement, in the ultrasonic motor of Patent Document 1 described above, either the moving body or the vibrating body is subjected to a hard anodizing treatment (registered trademark) by an anodizing method and the other friction surface. Is made of a super hard material made of a nickel phosphorus based alloy containing at least one of boron carbide, titanium boride, and boron nitride.
Japanese Patent Laid-Open No. 1-283072 JP-A-5-344757

However, in the ultrasonic motor of Patent Document 1, since the superhard material is harder than the anodized film, the anodized film may be worn depending on the characteristics of the anodized film that varies depending on the composition of the aluminum alloy that is the base material. was there.
Accordingly, an object of the present invention is to solve the problems of the conventional ultrasonic motor as described above, and to provide an ultrasonic motor that has a long driving life in addition to a large driving force and is less prone to wear.

  In order to solve the above problems, the present invention has the following configuration. That is, an ultrasonic motor according to claim 1 of the present invention includes a vibrating body in which a traveling wave is generated on a surface by ultrasonic vibration generated by a piezoelectric body, a movable body that contacts the vibrating body and is driven by the traveling wave, The movable body is made of an aluminum alloy having a silicon content of less than 2% by mass, and an aluminum oxide film formed by anodization on the contact portion of the surface with the vibrating body is provided. Is provided.

When the silicon content in the aluminum alloy is less than 2% by mass, an aluminum oxide film having a thick and uniform film thickness can be formed by anodizing treatment.
The ultrasonic motor according to claim 2 of the present invention is the ultrasonic motor according to claim 1, wherein the magnesium content in the aluminum alloy is 0.02 mass% or more and 2 mass% or less. Features.
If the magnesium content in the aluminum alloy is 0.02 mass% or more and 2 mass% or less, a hard aluminum oxide film can be formed by anodizing treatment.

  The ultrasonic motor according to the present invention has a long driving life in addition to a large driving force, and is less prone to wear.

An embodiment of an ultrasonic motor according to the present invention will be described in detail with reference to FIG.
The ultrasonic motor of FIG. 1 includes a vibrating body 2 to which a plurality of piezoelectric bodies 1 are bonded, and a movable body 3 that is in contact with the vibrating body 2 via a friction surface. The vibrating body 2 and the movable body 3 are annular members having substantially the same shape, and the cross section perpendicular to the circumferential direction is a rectangle. One of two parallel planes of each of the vibrating body 2 and the movable body 3 is opposed to and brought into contact as a friction surface. Yes. Then, a plurality of piezoelectric bodies 1 are attached substantially equally over the circumferential direction on a plane that is not a friction surface among two parallel planes of the vibrating body 2.

When a high frequency voltage is applied to the piezoelectric body 1, the piezoelectric body 1 emits ultrasonic vibration, and a traveling vibration wave (traveling wave) having a natural frequency is generated on the surface (friction surface) of the vibration body 2 by this ultrasonic vibration. Since this traveling wave advances the vibrating body 2 continuously, the movable body 3 that is in pressure contact with the vibrating body 2 rotates by receiving a thrust so that the wave carries the object.
The movable body 3 is made of an aluminum alloy having a silicon content of less than 2% by mass and a magnesium content of 0.02% by mass to 2% by mass, and at least a friction surface among the surfaces thereof. Is provided with an aluminum oxide film (for example, a hard aluminum oxide film formed by hard anodization) (not shown). When the silicon content satisfies the above conditions, an aluminum oxide film having a thick and uniform film thickness is formed on the surface of the aluminum alloy by anodizing treatment. If the magnesium content satisfies the above conditions, a hard aluminum oxide film is formed on the surface of the aluminum alloy by anodizing.

Here, the anodizing treatment will be described. Anodizing treatment is a treatment for electrically forming an oxide film on the surface of aluminum. Specifically, when electrolysis is performed in an aqueous solution of dilute sulfuric acid or oxalic acid using aluminum as an anode, an aluminum oxide film is formed on the surface of the aluminum according to the following formula. By such treatment, the surface of aluminum is hardened and wear resistance is improved.
2Al + 3H ₂ O → Al ₂ O ₃ + 6H ⁺ + 6e ⁻
However, there are various types of aluminum alloys from 1000 series to 7000 series due to the difference in characteristics, and the types (Si, Cu, Mg, etc.) and contents of alloy components (elements) are greatly different. Depending on the type of alloy component, there is an influence on the formation of an aluminum oxide film by anodizing.

  Since silicon has an action of suppressing oxidation, when an aluminum alloy contains a large amount of silicon, formation of an aluminum oxide film is suppressed in anodizing treatment. Furthermore, since silicon is dispersed in the form of silicon as particles in the aluminum alloy, the formation of an aluminum oxide film is suppressed in the vicinity of the silicon particles, and the film thickness tends to be nonuniform. For these reasons, an aluminum alloy containing a large amount of silicon has an insufficient wear resistance because an aluminum oxide film having a sufficient film thickness is difficult to be formed even when anodizing is performed. Therefore, when the movable body is composed of an aluminum alloy containing a large amount of silicon, the aluminum oxide coating may be worn in a short time and have a short life when contacting the vibrating body with high friction.

On the other hand, in order to improve the wear resistance of the aluminum oxide film, it is also effective to improve the hardness of the aluminum oxide film. Since an aluminum alloy containing magnesium forms a hard aluminum oxide film by anodizing treatment, a movable body having excellent durability can be obtained by forming the movable body with such an aluminum alloy.
For these reasons, it is preferable that the movable body is made of an aluminum alloy in which the silicon content is suppressed and magnesium is contained. Then, a thick and hard aluminum oxide film can be obtained, so that the durability of the movable body is improved and the ultrasonic motor has a long life.

〔Example〕
The present invention will be described more specifically with reference to the following examples.
Using a movable body made of an aluminum alloy as shown in Table 1, an ultrasonic motor having the same configuration as the ultrasonic motor of FIG. 1 described above was manufactured. Then, the movable body and the vibrator were brought into pressure contact with each other at a pressure of 70 kPa, rotated at a rotational speed of 350 min ⁻¹ , and the time (life) until the rotation became impossible was measured.

  Table 1 shows the measurement results of the lifetime. The numerical value of the lifetime in Table 1 is shown as a relative value when the lifetime of Comparative Example 4 is 1. Table 1 also shows the film thickness and Vickers hardness of the aluminum oxide coating. This film thickness was measured by cutting the anodized aluminum alloy and observing the structure of the cross section. In Table 1, the film thickness of Comparative Example 4 is shown as a relative value. .

As can be seen from Table 1, in Examples 1 to 13, since the film thickness of the aluminum oxide coating was thicker than those in Comparative Examples 1 to 4, the lifetime was remarkably excellent. And in Examples 1-13, what contained magnesium in the aluminum alloy had a longer life because the Vickers hardness of the aluminum oxide film was high.
Here, the data shown in Table 1 was graphed, and the correlation between the silicon content in the aluminum alloy and the film thickness of the aluminum oxide film was examined. The graph is shown in FIG. As described above, since the formation of the aluminum oxide film is suppressed when the silicon content is large, the film thickness is insufficient when the silicon content is 2% by mass or more, as can be seen from the graph of FIG. It has become. Further, if the silicon content is 2% by mass or more, the film thickness tends to be non-uniform. For these reasons, the silicon content in the aluminum alloy needs to be less than 2% by mass, and more preferably 1.2% by mass or less.

  Next, the data shown in Table 1 was graphed, and the correlation between the magnesium content in the aluminum alloy and the Vickers hardness of the aluminum oxide film was examined. The graph is shown in FIG. As described above, since a hard aluminum oxide film is formed on the surface of the aluminum alloy containing magnesium, as can be seen from the graph of FIG. 3, when the magnesium content is 0.02 mass% or more, the Vickers hardness is Is getting higher. Therefore, the magnesium content in the aluminum alloy is preferably 0.02% by mass or more.

However, as can be seen from the graph of FIG. 3, when the magnesium content exceeds 2% by mass, the Vickers hardness tends to decrease. Furthermore, from the viewpoint of cost, the upper limit of the magnesium content is preferably 2% by mass. Therefore, it is preferable that the magnesium content in the aluminum alloy is 0.02 mass% or more and 2 mass% or less. In Comparative Examples 1 to 4, the silicon content in the aluminum alloy exceeds 2 mass%. Since the film thickness of the aluminum oxide film was insufficient, the life was short. Even when magnesium was included and the Vickers hardness was increased as in Comparative Example 3, the film thickness of the aluminum oxide film was insufficient and non-uniform, so that the life was short.

1 is a perspective view showing an embodiment of an ultrasonic motor according to the present invention. It is a graph which shows the correlation with content of the silicon in an aluminum alloy, and the film thickness of an aluminum oxide film. It is a graph which shows the correlation with content of magnesium in an aluminum alloy, and the hardness of an aluminum oxide film.

Explanation of symbols

1 Piezoelectric body 2 Vibrating body 3 Movable body

Claims (2)

  In an ultrasonic motor comprising: a vibrating body in which a traveling wave is generated on a surface by ultrasonic vibration generated by a piezoelectric body; and a movable body that contacts the vibrating body and is driven by the traveling wave, the movable body is made of silicon. An ultrasonic motor comprising an aluminum alloy having a content of less than 2% by mass, and an aluminum oxide film formed by anodizing treatment on the surface of the aluminum alloy in contact with the vibrating body.   2. The ultrasonic motor according to claim 1, wherein the content of magnesium in the aluminum alloy is 0.02 mass% or more and 2 mass% or less.

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