JP2003134854A - Friction material for vibration wave motor, vibration wave motor, and apparatus using vibration wave motor as drive source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction material for vibration wave motor which is superior in wear resistance and high in coefficient of friction, and enables stable driving. SOLUTION: The friction material is used in the frictional engagement portion of the vibrating body and/or the contact body of a vibration wave motor. The friction material is a metal, having a hardened layer on the surface thereof in contact with a mating material. An oxide film, containing Fe2 O3 , is formed on the surface of the hardened layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material for a vibration wave motor, a vibration wave motor using the same, and a device using the vibration wave motor as a drive source.

[0002]

2. Description of the Related Art Generally, in a vibration wave motor, an AC voltage is applied to a piezoelectric element as an electric-mechanical energy conversion element forming a vibrating body so that the surface particles of an elastic body such as a metal forming the vibrating body are applied. A circular or elliptical motion is excited, and the contact body that is brought into pressure contact with the circular body or the elliptical motion and the vibrating body are relatively moved by friction drive. Therefore, it is desirable to provide the vibrating body and the contact body with a large friction coefficient as a friction material in the pressure contact portion in order to efficiently take out the output of the vibration wave motor, and the abrasion of the friction material directly affects the durable life of the motor. It is desirable to use a material that is less likely to wear because it will be connected.

Therefore, various materials and composite materials have been conventionally proposed as friction materials. Among them, as those having relatively low cost and excellent wear resistance, some have been proposed in which a contact surface of a metal material is subjected to surface treatment for enhancing wear resistance. For example, Japanese Unexamined Patent Publication No. 9-65670 proposes an iron-based material in which an element other than iron is diffused on the surface and surface-hardened. Further, it has been proposed to perform steam treatment for diffusing the element and forming a film of Fe ₃ O _{4 on} the surface.

[0004]

However, in the case where the element other than iron is diffused on the surface of the iron-based material to harden the surface, which has been proposed in the above-mentioned conventional example, it is described in the above-mentioned conventional example. Fe ₃ O, which has the effect of reducing such wear
The film of ₄ was hardly formed, and there was a problem that the friction material was worn out in a short time.

Further, Fe ₃ O is formed on the surface after the element is diffused.
Even when the steam treatment for forming the film of No. ₄ was performed, the wear resistance did not improve so much, and the friction coefficient of Fe ₃ O ₄ was relatively small at about 0.3, so the efficiency of the vibration wave motor was low. It was

At the same time, when the surface roughness of the contact surface of the friction material is too large, there is a problem that severe wear occurs.

The object of the invention according to the present application is to solve the above-mentioned problems and to provide a friction material for a vibration wave motor having a long durability life, stable operation, and a relatively high friction coefficient. Another object is to provide a conventional vibration wave motor and a device using the vibration wave motor as a drive source.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned object, a first solution means of a vibration wave motor according to the present application is, as described in claim 1, a vibrating body that generates vibration and the vibration. In a vibration wave motor in which a contact body in contact with a body moves relatively, a friction material provided in a friction contact portion of at least one of the vibration body and the contact body, the friction material being provided on a contact surface with a counterpart material. The friction material for a vibration wave motor is characterized in that it is a metal having a hardened layer, and an oxide film containing Fe ₂ O ₃ is formed on the surface of the hardened layer.

In this solution, the friction material provided on the friction contact portion of at least one of the vibrating body and the contact body has a hardened layer on the contact surface with the mating material.

Therefore, the vicinity of the contact surface is less likely to be destroyed by the shear stress generated when the vibration wave motor is driven.

At the same time, a hardened layer portion can be obtained with a higher hardness and at a lower cost than by hardening the entire friction material.

Further, since an oxide film containing Fe ₂ O ₃ is formed on the surface of the hardened layer, seizure is unlikely to occur between the friction material and the mating material, and the friction coefficient is about 0.6. high.

Therefore, by forming the contact surface of the friction material as the hardened layer and forming the oxide film containing Fe ₂ O ₃ on the surface of the hardened layer, the wear resistance is high, the stability is high, and the friction coefficient is high. A friction material for a high vibration wave motor can be obtained.

A second solution according to the present application is that, as described in claim 2, the hardened layer has a Vickers hardness of 600 Hv or more, and the vibration wave according to claim 1. It is in the friction material for motors.

In this solution, since the hardened layer has a Vickers hardness of 600 Hv or more, it is more difficult for the fracture and deformation in the vicinity of the contact surface to occur more clearly than in the case of a hardness of less than this, and more wear resistance. Highly stable and stable friction material for vibration wave motors can be obtained.

[0016] A third solution means according to the present application is, as described in claim 3, characterized in that the metal is stainless steel, heat resistant steel or tool steel. This is in the friction material for vibration wave motors.

In this solution, since the metal is stainless steel, heat-resistant steel, or tool steel, it can be easily and easily treated by carburizing, nitriding, sulfurizing, carburizing and nitrifying, ion-implanting, and induction hardening. The hardened layer defined in claim 1 can be formed at low cost.

At the same time, an oxide film containing Fe ₂ O ₃ can be easily formed on the surface of the hardened layer at low cost.

Therefore, it is possible to easily obtain a stable friction material for a vibration wave motor with high wear resistance at low cost.

[0020] A fourth solution according to the present application is that, as described in claim 4, the hardened layer contains at least one of carbon, nitrogen, sulfur, nickel and titanium in an amount richer than that of the base material. The friction material for a vibration wave motor according to any one of claims 1 to 3.

In this solution, the hardened layer is carbon,
Since it contains at least one of nitrogen, sulfur, nickel, and titanium in abundance more than the base material, it has higher hardness than when the hardened layer contains other elements, and it has higher wear resistance and stable vibration waves. A friction material for motors can be obtained.

A fifth solution means according to the present application is that, as described in claim 5, the arithmetic mean roughness Ra of the contact surface of the friction material is 0.03.
The friction material for a vibration wave motor according to any one of claims 1 to 4, wherein the friction material has a thickness of less than or equal to μm.

In this solution, since the arithmetic mean roughness Ra of the contact surface of the friction material is 0.03 μm or less, the amount of wear powder generated on the sliding surface at the initial stage of driving the vibration wave motor is small, Therefore, sudden initial wear does not occur.

Therefore, a more stable friction material for a vibration wave motor can be obtained.

Furthermore, the present invention is a device provided with the vibration wave motor according to any one of claims 1 to 5 as a drive source.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) FIG. 1 and FIG.
2 is a sectional view of a vibration wave motor using a friction material according to the present embodiment. Reference numeral 1a denotes a ring-shaped friction material coupled to the elastic body 1 such as a metal forming the rod-shaped vibrating body, and the thickness of the center side gradually becomes thicker than the thickness of the radially outer peripheral portion. 2a
Is a cylindrical friction material coupled to the moving body 2 as a contact body. The rod-shaped vibrating body includes the piezoelectric element 3 between the elastic bodies 1 and 1 '.
The piezoelectric element has electrodes formed on both sides across the diameter portion and electrodes formed on the entire back surface, and the polarization treatment directions in both electrode regions are different from each other. Four sheets are stacked with the phase shifted by 90 degrees (electrode plates are sandwiched between piezoelectric elements).

In the present embodiment, these friction materials were manufactured by cutting the base material of aluminum alloy and pressing the base material of iron alloy. good. Further, in the case of the friction material 2a on the moving body side, the pipe may be cut.

Further, the method of connecting these friction materials to the vibrating body and the moving body was adhesion in this experiment, but press fitting or welding may be used.

The details of the driving principle of this vibration wave motor are described in Japanese Patent Application Laid-Open No. 3-117384, and the description thereof is omitted here.

In FIG. 1, reference numeral 3 denotes a piezoelectric element as an electro-mechanical energy conversion element, which receives an alternating voltage from a drive circuit (not shown) and is applied to a drive portion of an elastic body 1 which constitutes a vibrating body as a drive vibration. Generate an elliptical motion.

Reference numeral 4 is a coil spring for pressing the moving body 2 against the elastic body 1, and 5 is an output gear that rotates integrally with the moving body 2. Then, the lens in the lens barrel in which the vibration wave motor is mounted is driven via the output gear.

In the present embodiment, the vibration wave motor is used, the friction materials are changed, and some combinations of the friction materials are set. Fig. 3 shows a list of the materials used and the amount of wear after assembling them in a motor and performing a durability test.

In the durability test of FIG. 3, the surface pressure was adjusted so that the driving torque of the motor was about 0.02 N · m, and then the examination was conducted.

Friction material 1a on the vibrating body side and friction material 2a on the moving body side
Are in contact with the width (0.1 mm) of the friction material 2a on the moving body side, and since the center diameter of the friction surface is 8.6 mm, the contact area is 2.7 mm2.

On the other hand, the friction member 2a on the moving body side is pressed against the friction member 1a on the vibrating body side by the coil spring 4, and the force is 6N to 12N as a result of the above adjustment. Therefore, the surface pressure is 2.2 ~
It is 4.4 N / mm2.

In this embodiment, the rotation speed is 0.24 m.
The test was conducted under a load of 0.005 N · m with a constant value of / s.

In this embodiment, the vibrating body 1 and the friction material 1
Although a is a separate member, it is possible to integrate the two.
Further, the moving body 2 and the friction material 2a can be integrated.

The "material" to "presence or absence of Fe ₂ O ₃ coating" shown in FIG. 3 are all described for the friction material 1a.

"Hardness (Hv)" in FIG. 3 is a value obtained by preparing a cross-section sample of the friction material 1a and measuring the hardness of the hardened layer portion and the base material portion with a Vickers hardness meter.

The hardened layer contains at least one of carbon, nitrogen, sulfur, nickel and titanium in abundance more than the base material. That is, the hardness becomes higher and the abrasion resistance becomes higher than when the hardened layer contains another type of element.

With respect to the base material, except for No. 13, vacuum heat treatment was performed to obtain a hardness of about 510 Hv to 570 Hv.
About the hardened layer part, 570Hv ~ 1 by the method described later
The hardness is about 200 Hv.

"Curing method of hardening layer" of FIG. 3 is No. 1 to 11
Up to the surface hardening treatment method (No. 12 does not carry out hardening treatment).

Regarding No. 1 to 3 nitriding treatment, a mixed salt containing 40% sodium cyanate was used, and the friction material 1a was immersed in a salt bath and treated for 1 hour to form a hardened layer containing nitrogen.

Hardened layers other than these are also processed by known methods (for example, refer to Mechanical Design Vol. 44, No. 5), and then the sliding surface of the friction material 1a is paper wrap of fixed abrasive grains having a particle diameter of 0.5 μm. Then, the arithmetic average roughness Ra of the sliding surface was set to about 0.02 μm.

"Cured layer thickness" in FIG. 3 is a value obtained by measuring the cured layer thickness by making a cross-section sample after the hand wrapping described above.

"Presence or absence of Fe ₂ O ₃ coating" in FIG. 3 shows whether or not a coating containing Fe ₂ O ₃ is formed on the surface of the hardened layer. Here, the procedure when there is "Yes" is
After the above-mentioned wrapping was performed on the contact surface of the friction material 1a, the friction material 1a was put into an ordinary heater, heated to 500 ° C., and left for 5 hours. Then, when taken out from the heater, a reddish blue film was observed on the contact surface.

When this film was analyzed by X-ray photoelectron spectroscopy, Fe ₂ O ₃ was detected in all cases, and it was confirmed that an oxide film containing Fe ₂ O ₃ was formed on the sliding surface. .

The friction material 2a was set according to the specifications shown in FIG. 4, and then the above-mentioned hand wrap was carried out so that the Ra of the sliding surface was about 0.02 μm.

Here, the wear amount in FIG. 3 is shown as a wear depth (vibrating body side) and a wear height (moving body side) per relative moving distance of 50 Km between friction materials. The wear amount of 50Km is 5K under the condition that it is judged that there is no 50Km life if the wear progresses at this point and the wear progresses in direct proportion.
The wear amount at the time point m was multiplied by 10 and displayed.

Further, the judgment of FIG. 3 is based on the conventional example of 30 μm corresponding to the alumite film thickness, and the friction material 1a and the friction material 1a are compared.
The wear amount of the larger one of 2a is in the range of 11μm to 30μm, it is acceptable as “△”, the one in the range of 4μm to 10μm is good as “○”, 3μm or less is excellent as “◎”, and 30μ
Those that were larger than m were marked as "X".

Next, the test results will be described.

As shown in FIG. 3, when the judgment is Δ to ⊚, the hardness of the hardened layer is 630 Hv or more, and the oxide film containing Fe ₂ O ₃ is formed on the surface of the hardened layer. This is the case.

In particular, when the hardness of the hardened layer portion is 800 Hv or more, all judgments are ◯ to ⊚.

Compared with this, even when the hardness of the hardened layer is 1180 or more as in Samples No. 3 and No. 7, it is
If there was no oxide film containing Fe ₂ O ₃ on the surface, severe vibration occurred and the vibration wave motor stopped.

Even when an oxide film containing Fe ₂ O ₃ is formed on the sliding surface as in Sample No. 12, when the hardened layer does not exist and the hardness of this portion is 550 Hv, it is relatively soft. After all, severe wear occurred.

When the sliding surface of No. 12 was observed with a microscope,
It was confirmed that the oxide film on the surface was completely destroyed by friction.

At the same time, it was confirmed that the base material portion under the oxide film was deformed due to unevenness.

It is considered that these indicate that the base material having no hardened layer was deformed and the oxide film was broken, whereby the base material metal was brought into direct contact with the mating material, resulting in severe wear. To be

Next, sample No. 13 is a comparative example, and even if a hardened layer of about 570 Hv was formed on the sliding surface with alumite, destructive wear occurred.

Further, although not shown in FIG. 3, sample No. 1
In the same sample as ~ 2, a rough sample in which only Ra was about 0.040 μm was also prepared and the durability test was performed.

All the results are 100 μ per relative moving distance of 50 km.
It became severely worn over m.

(Second Embodiment) Next, a test conducted to examine a range in which the hardness of the hardened portion of the friction material and the arithmetic mean roughness Ra of the sliding surface give good wear resistance is shown in FIG. And Fig. 6
Shown in.

FIG. 5 shows the test results of the hardness of the hardened part.

In this test, as the material of the friction material 1a, three kinds of martensitic stainless steel SUS440C, martensitic heat resistant steel SUH3 and carbon tool steel SK3 were used.

Here, the friction material 1a is first induction-hardened to form a hardened layer having a hardness of 900 Hv and a thickness of about 100 μm on the surface, and then the tempering temperature is set to 150 ° C. to 600 ° C. in vacuum.
Hardness of each cured layer is 900H by shaking at ℃
Five samples of v to 550 Hv were prepared for each material.

Separately from this, a nitriding treatment was performed on the friction material 1a to prepare one sample for each material having a hardened layer having a hardness of 1200 Hv and a thickness of about 30 μm formed on the surface.

A durability test was carried out using these,
The test conditions such as the pressure contact force, the method of forming the film containing Fe ₂ O ₃ and the specifications of the sample are as shown in the sample No. 3 of FIG.
It is the same as 1, 2, and 4, and three kinds of materials correspond to each graph line in FIG. 5, respectively.

The wear amount is an average value on both the vibrating body side and the moving body side.

As shown in FIG. 5, the result shows that the hardness of the hardened layer is 600 Hv.
In all the above cases, good results with a wear amount of 30 μm or less were obtained.

Therefore, it was confirmed that when the hardness is 600 Hv or more, the above-mentioned hardened layer portion is not deformed when the motor is driven, and the wear resistance is significantly improved.

FIG. 6 shows the test results of Ra on the sliding surface.

In this test, the test conditions such as the pressure contact force between the vibrating body and the moving body, the method for forming the film containing Fe ₂ O ₃ and the specifications of the samples are the same as those of Sample Nos. 1, 2, and 4 of FIG. 3 except Ra. They are the same, and three types of materials correspond to the graph lines in FIG. 6, respectively.

The amount of wear is an average value on both the vibrating body side and the moving body side, as in FIG.

Here, 0.5 μm to 7.0 μ is applied to the sliding surface of the friction material 1a.
Six kinds of samples having Ra = 0.015 μm to 0.040 μm were prepared by hand lapping with m fixed abrasive grains, and the above-mentioned durability test was carried out.

As shown in FIG. 6, as shown in FIG. 6, when Ra = 0.03 μm or less, good results with a wear amount of 30 μm or less were obtained in all cases.

Therefore, it was confirmed that when Ra = 0.03 μm or less, a large amount of initial wear powder does not occur when the motor is driven due to the roughened sliding surface, and the wear resistance is greatly improved.

[0077]

As described above, according to the present invention,
The friction material provided on the friction contact surface of at least one of the vibrating body or the contact body of the vibration wave motor is a metal having a hardened layer on the contact surface with the counterpart material, and the surface of the hardened layer is made of Fe.
_{Since the} oxide film containing ₂ O ₃ is formed, it is possible to obtain a friction material for a vibration wave motor that has high wear resistance, is stable, and has a high friction coefficient.

The hardened layer has a Vickers hardness of 600H.
Since it has a hardness of v or higher, wear resistance is higher and a stable friction material for vibration wave motors can be obtained.

Further, since the metal is stainless steel, heat resistant steel, or tool steel, it is possible to easily obtain a stable friction material for a vibration wave motor with high wear resistance at low cost.

Further, since the hardened layer contains at least one of carbon, nitrogen, sulfur, nickel, and titanium in abundance more than the base material, it is possible to obtain a stable friction material for a vibration wave motor having higher wear resistance. available.

Further, the arithmetic mean roughness Ra of the contact surface of the friction material is
Since it is 0.03 μm or less, a more stable friction material for vibration wave motors can be obtained.

Further, the present invention can provide an apparatus using the vibration wave motor provided with the above-mentioned friction material, which has a long durability life, low cost and excellent stability.

[Brief description of drawings]

FIG. 1 is a sectional view of a vibration wave motor showing an embodiment of the present invention.

2 is an enlarged view of the vicinity of the friction material of FIG.

FIG. 3 is a chart showing a list and determination of friction materials 1a used in the present embodiment.

FIG. 4 is a chart showing data of the friction material 2a used in the present embodiment.

FIG. 5 is a diagram showing a relationship between hardness and wear amount of a hardened layer of a friction material according to a second embodiment.

FIG. 6 Ra of the sliding surface of the friction material according to the second embodiment
Figure showing the relationship between wear and wear

[Explanation of symbols]

1 vibrating body 1a Vibration side friction material 2 moving body 2a Moving body side friction material 3 Electric-mechanical energy conversion element 4 coil spring 5 output gears

Claims (7)

[Claims] 1. A friction material used for a frictional contact portion of at least one of the vibrating body and the contacting body in a vibration wave motor in which a vibrating body that generates vibration and a contacting body that contacts the vibrating body move relative to each other. The friction material is a metal having a hardened layer on the contact surface with the mating material, and an oxide film containing Fe ₂ O ₃ is formed on the surface of the hardened layer. Friction material for motors. 2. The hardened layer has a Vickers hardness of 600 Hv.
The friction material for a vibration wave motor according to claim 1, having the above hardness. 3. The friction material for a vibration wave motor according to claim 1, wherein the metal is stainless steel, heat resistant steel, or tool steel. 4. The vibration wave according to claim 1, wherein the hardened layer contains at least one of carbon, nitrogen, sulfur, nickel and titanium in abundance more than the base material. Friction material for motors. 5. The arithmetic mean roughness Ra of the contact surface of the friction material is
The friction material for a vibration wave motor according to any one of claims 1 to 4, wherein the friction material has a thickness of 0.03 µm or less. 6. A vibrating wave motor in which a vibrating body that generates vibration and a contact body that is in contact with the vibrating body move relatively to each other. 5. A vibration wave motor using the friction material for a vibration wave motor according to any one of 5 above. 7. An apparatus using the vibration wave motor according to claim 6 as a drive source and driving a driven body.