JPH08182353A - Ultrasonic motor - Google Patents

Abstract

PURPOSE: To elongate the service life of an ultrasonic motor by reducing the wear of the frictionally contacting surface of the motor and suppressing the increase of the holding torque of the motor. CONSTITUTION: In an ultrasonic motor 10 provided with an elastic body 12 which makes ultrasonic vibrations when an piezoelectric body 11 is excited and a moving body 13 which is driven by the ultrasonic vibrations made by the elastic body 12, the part of the elastic body 12 including its frictionally contacting surface with the moving body 13 is composed of a Cr-containing layer and the part of the moving body 13 including its frictionally contacting surface with the elastic body 12 is composed of an Ni-containing layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor which uses an electromechanical conversion element to generate a vibration wave in a vibrator and frictionally drives a relative motion member by the vibration wave, and more particularly to improvement of a friction contact surface. It is a thing.

[0002]

2. Description of the Related Art Conventionally, there is known an ultrasonic motor which uses an electromechanical conversion element to generate a vibration wave in a vibrator and drives the relative motion member by the vibration wave. In this type of ultrasonic motor, the oscillator and the relative motion member are in frictional contact with each other, the vibration wave generated in the oscillator is transmitted to the relative motion member, and the relative motion member is frictionally driven. Therefore, the vibrator needs to efficiently transmit the applied ultrasonic vibration to the relative motion member. Therefore, a highly elastic material such as an iron-based or stainless-based metal material is used for the vibrator.

Further, in the conventional frictional contact surface between the vibrator and the relative motion member, an alumite layer is provided on one surface,
Those having a Ni layer on the other surface are widely used.
Here, alumite is anodized aluminum with a corrosion-resistant oxide film. The oxide film is mainly made of Al ₂ O ₃ , though it depends on the treatment.
No lubricating oil or the like is used for this friction contact surface. Therefore, this frictional contact surface becomes non-hydrodynamic lubrication, that is, boundary lubrication. For this reason, the oxide film plays a role as a lubricating oil, and the oxide film greatly affects the transmission efficiency of ultrasonic vibration, that is, the function of the ultrasonic motor.

[0004]

However, in the above-described conventional ultrasonic motor, when friction driving is performed for a long time, the oxide film on the frictional contact surface deteriorates with time, and the contact surface of the vibrator and the relative motion member is changed. It will wear out. As a result, abrasion powder is generated and the holding torque is increased. And finally, the ultrasonic motor cannot be driven. When the conventional alumite layer and Ni layer were brought into frictional contact, the life in the continuous durability test was about 13 hours. Therefore, it is required to stabilize the frictional contact surface more than before and extend the life of the ultrasonic motor.

The present invention has been made in order to solve the above-mentioned problems, and reduces wear of the frictional contact surface, suppresses an increase in holding torque, and prolongs the life of the ultrasonic motor. The purpose is to plan.

[0006]

In order to achieve the above-mentioned object, the invention of claim 1 is a vibrator for generating ultrasonic vibration in an elastic body (12) by exciting an electromechanical conversion element (11). 11, 12) and a relative motion member (13) that is brought into pressure contact with the vibrator and is driven by the ultrasonic vibration, in the ultrasonic motor (10), One of the parts including the friction contact surface is C
It is an r-containing layer and the other is a Ni-containing layer. The invention of claim 2 is the ultrasonic motor according to claim 1, wherein the Cr-containing layer is a composite hard Cr layer, and the Ni-containing layer is a Ni alloy layer. The invention of claim 3 is the ultrasonic motor of claim 1 or 2, wherein the Ni-containing layer is formed by electroplating or electroless plating. The invention of claim 4 is the ultrasonic motor according to any one of claims 1 to 3, wherein the Cr-containing layer and the Ni-containing layer are
It is characterized in that the thickness is 200 μm or less.

[0007]

In the invention of claim 1, the Cr-containing layer and the Ni are
When the Ni-containing layer is frictionally contacted and driven, a Ni oxide film is formed on the surface of the Ni-containing layer. This Ni oxide film is
Compared with the conventional anodized oxide film, it has less wear on the frictional contact surface, has stability, and has high hardness.
Therefore, the life of the ultrasonic motor can be extended. In the invention of claim 2, the friction contact surface is composed of a composite hard Cr layer and a Ni alloy layer. Therefore, since the surface hardness is high, a large driving force can be obtained by increasing the applied pressure. In the invention of claim 3, the Ni-containing layer is formed by electroplating or electroless plating. Therefore, the Ni-containing layer can be formed at low cost. Claim 4
In the above invention, the thickness of the Ni-containing layer is 200 μm or less. Therefore, it is possible to prevent the Cr-containing layer and the Ni-containing layer from being distorted or peeled off. In addition, it can be manufactured efficiently.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an external configuration of an ultrasonic motor according to an embodiment of the present invention. This ultrasonic motor 10 includes a piezoelectric body 11, an elastic body 12, and a moving body 1.
It is composed of 3 etc. The piezoelectric body 11 is one of electromechanical conversion elements and is excited by the supply of a drive signal, and is fixed to a support body 16 such as a lens barrel of a camera via a vibration absorbing material 15 such as felt. Has been done. The elastic body 12 is made of an electrically conductive adhesive or the like to form the piezoelectric body 11.
And a progressive vibration wave is generated by exciting the piezoelectric body 11. The elastic body 12 is formed of brass or an iron alloy such as a stainless material or an Invar material. The moving body 13 is pressed against the elastic body 12 and frictionally driven by the progressive vibration wave. The flexible printed board 14 is for supplying a drive signal to the piezoelectric body 11, and is electrically connected to a predetermined electrode portion of the piezoelectric body 11.

FIG. 2 is a sectional view showing in detail the frictional contact surface between the elastic body 12 and the moving body 13. A Cr-containing layer 17 is provided on the contact surface of the elastic body 12 with the moving body 13. Further, on the contact surface of the moving body 13 with the elastic body 12,
A Ni-containing layer 18 is provided. That is, the elastic body 1
The Cr-containing layer 17 and the Ni-containing layer 18 are actually in contact with each other and the moving body 13. Here, on the frictional contact surface of the ultrasonic motor 10 of the present invention, the Cr-containing layer 17 and Ni
The reason for applying the containing layer 18 will be described below. In general,
When selecting a pair of members that make frictional contact, how quickly a severe / mild transition is caused on the contact surface (how quickly they are fitted) is extremely important. Here, the present inventor has considered that the combination of Cr and Ni can cause severe mild transition earlier than the combination of Al and Ni, which are the main components of alumite. Because Ni belongs to the d-block element,
Al belongs to the p-block element and has little similarity to Ni. On the other hand, Cr and Ni are close to each other in the periodic table, and the element amounts also show similar values, and both of them belong to the d-block element.

Further, the inventor of the present invention has found that Cr and N
When i slides, an oxide film (NiO) (NiO) is formed on the Ni side.
It has been found that oxide) is produced. By interposing this oxide film on the frictional contact surface of the ultrasonic motor 10, it acts extremely effectively, that is, it gives a frictional effect to the frictional contact surface and can reduce the friction coefficient of the frictional contact surface. I understood. Further, it has been found that the presence of this oxide film reduces the amount of wear of the frictional contact surface extremely, the holding torque hardly increases, and stable driving can be obtained. From the above, the Cr-containing layer 17 and the Ni-containing layer 18 were applied to the frictional contact surface of the ultrasonic motor 10. Next, specific examples will be described.

(First Embodiment) The elastic body 12 is made of stainless steel (SUS304). The Cr-containing layer 17 is
It was formed by applying a composite ultra-hard Cr treatment to the surface of the elastic body 12. Cr-containing layer 17 formed by this treatment
Is mainly composed of Cr, and contains C, Mg, Al, Si, Ti,
It contains Mn and Fe. The surface hardness of the Cr-containing layer 17 was about 1000 to 1600 Hv. Therefore, since the surface hardness is higher than that of the conventional one, the pressing force can be increased. As a result, the drive torque of the ultrasonic motor 10 can be increased.
The Cr-containing layer 17 had a thickness of about 40 μm and a surface roughness of 0.3 μm (Rmax). Here, if the Cr-containing layer 17 is formed to have a thickness of 200 μm or less, it is possible to prevent distortion and peeling (the same applies to the Ni-containing layer 18 described later). And
After forming the Cr-containing layer 17, the piezoelectric body 11 was bonded to the bottom surface of the elastic body 12 with an epoxy adhesive. On the other hand, the moving body 13
Was formed from Al. Then, the Ni-containing layer 18 was formed by applying electroless Ni-P plating to the surface of the moving body 13. If the Ni-containing layer 18 is formed by electroless plating or electroplating, it can be formed without increasing the cost.

When the ultrasonic motor 10 having the above structure is driven, (1) the shape of the elastic body does not change,
(2) The amount of wear on the friction contact surface is extremely small, and stable friction driving can be performed for a long time. (3) The driving torque generated by the pressurization of the elastic body 12 and the moving body 13 is large. (4) During friction driving Low noise, (5)
An advantageous effect was obtained as compared with the conventional ultrasonic motor in that stable driving with little deterioration with time can be obtained by driving for a long time. Further, when a durability test in which friction driving is continuously performed is performed, the life of the ultrasonic motor 10 of the present invention is
It was 21 hours. This is about 1.6 times the life (13 hours) of the conventional ultrasonic motor.

(Second Embodiment) In the second embodiment, the first
Only the Ni-containing layer 18 is different from the example of FIG. The Ni-containing layer 18 of the second embodiment is a composite Ni-plated moving body 1.
3 formed on the surface. The Ni-containing layer 18 formed by the composite Ni plating includes Ni, P, and P.
It contains TFE (polytetrafluoroethylene). Also in the ultrasonic motor 10 having the above configuration, the same effect as that of the first embodiment was obtained.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment,
The following various modifications are possible without departing from the gist of the invention. (1) In the embodiment, the Cr-containing layer 17 is formed on the elastic body 12 side and the Ni-containing layer 18 is formed on the moving body 13 side. On the contrary, the Ni-containing layer 18 is formed on the elastic body 12 side. However, the Cr-containing layer 17 may be formed on the moving body 13 side. (2) In the embodiment, the invention is applied to the rotary ultrasonic motor 10, but it can also be applied to a linear drive ultrasonic motor. (3) In the embodiment, the ultrasonic motor 10 that drives the moving body 13 by the progressive vibration wave is shown, but it can be applied to an ultrasonic motor that drives the moving body by the vibration of the torsional vibration body. (4) The present invention can also be applied to an electromechanical conversion actuator that does not use an ultrasonic region.

[0015]

According to the first aspect of the present invention, due to the action of the Ni oxide film formed on the frictional contact surface between the vibrator and the relative motion member, abrasion of the frictional contact surface is reduced and stable for a long time. By realizing the driving, the life of the ultrasonic motor can be extended. Further, since the friction coefficient of the frictional contact surface is small, noise generated during driving can be reduced. According to the invention of claim 2, the driving torque can be increased. According to the invention of claim 3, the Ni-containing layer can be formed at low cost. According to the invention of claim 4, it is possible to prevent distortion in the Cr-containing layer and the Ni-containing layer. In addition, peeling of these layers can be prevented. Furthermore, these layers can be manufactured efficiently.

[Brief description of drawings]

FIG. 1 is a perspective view showing an external configuration of an embodiment of an ultrasonic motor according to the present invention.

FIG. 2 is a cross-sectional view showing in detail a frictional contact surface between an elastic body 12 and a moving body 13.

[Explanation of symbols]

 10 Ultrasonic Motor 11 Piezoelectric Body 12 Elastic Body 13 Moving Body 14 Flexible Printed Circuit Board 15 Vibration Absorbing Material 16 Support

Claims (4)

[Claims] 1. An ultrasonic wave comprising a vibrator that generates ultrasonic vibration in an elastic body by exciting an electromechanical conversion element, and a relative motion member that is in pressure contact with the vibrator and is driven by the ultrasonic vibration. In the motor, one of a portion including a frictional contact surface between the vibrator and the relative motion member is a Cr-containing layer, and the other is a Ni-containing layer. 2. The ultrasonic motor according to claim 1, wherein the Cr-containing layer is a composite hard Cr layer, and the Ni-containing layer is a Ni alloy layer. 3. The ultrasonic motor according to claim 1, wherein the Ni-containing layer is formed by electroplating or electroless plating. 4. The ultrasonic motor according to claim 1, wherein the Cr-containing layer and the Ni-containing layer have a thickness of 200 μm.
An ultrasonic motor characterized in that the ultrasonic motor is formed with a thickness of m or less.