JPH11172123A - Friction material for oscillatory wave motor, oscillatory wave motor and equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject friction material comprising a specific resin composition, used in a friction contact part of an oscillating body for forming oscillatory waves in an oscillatory wave motor and a contact body brought into friction contact with the oscillatory body and relatively moving with the oscillatory body by the oscillation and useful for the oscillatory wave motor and equipment. SOLUTION: This friction material is used in a friction contact part of an oscillatory body for forming oscillatory waves in an oscillatory wave motor, and a contact body brought into friction contact with the oscillatory body and relatively moving with the oscillatory body by the oscillation comprises a resin composition containing a heat-resistant resin (preferably a fluororesin or a polyimide resin) and mesophase pitch-based carbon fibers. The mesophase pitch-based carbon fibers are carbonaceous and preferably comprise staple fibers. The content of the mesophase pitch-based carbon fibers in the resin composition is preferably 10-30 wt.%. At least one of molybdenum disulfide and a polyimide powder is preferably contained in the resin composition.

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 and a device using the same.

[0002]

2. Description of the Related Art In general, a vibration wave motor causes a surface particle of a vibrating body to make a circular or elliptical motion, and frictionally drives a contact body pressed by the particle.

The principle outline of a vibration wave motor using a traveling vibration wave is as follows. A ring-shaped elastic body made of an elastic material such as metal whose total length is an integral multiple of a certain length λ, and two groups of multiple piezoelectric elements arranged in the circumferential direction bonded to one surface of an elastic body. Is a vibrating body (stator).

These piezoelectric elements are arranged in each group at a pitch of λ / 2 and alternately have opposite expansion and contraction polarities. Between the two groups, an odd multiple of λ / 4 is provided. They are arranged so that there is a shift. Both groups of piezoelectric elements are provided with electrode films.

If an AC voltage is applied to only one of the groups (hereinafter, referred to as the A phase), the vibrating body is arranged such that the center point of each of the A phase piezoelectric elements and points every λ / 2 therefrom are located at the antinodes. A standing wave (wavelength λ) of bending vibration is generated over the entire circumference of the elastic body such that the position, or the center point between the antinode positions, is the position of the node. When an AC voltage is applied only to the other group (hereinafter, referred to as B phase), a standing wave is generated in the same manner. The phase is shifted by λ / 4.

When alternating signals having the same frequency and having a time phase difference of 90 ° from each other are simultaneously applied to both the A and B phases, as a result of the synthesis of the resident waves of both, the elastic body vibrates in the circumferential direction. A traveling wave (wavelength λ) of bending vibration is generated, and at this time, each point of the elastic body having a thickness performs an elliptical motion.

Therefore, if a contact body (for example, a rotor as a moving body), for example, a ring-shaped contact body is brought into direct pressure contact with one surface of the vibrating body, the contact body will have a circumferential friction from the vibrating body. It is rotated and driven by the force. Actually, both the vibrating body and the contacting body are provided with friction materials at portions where they come into contact with each other, so that a frictional force is effectively generated.

A vibration wave motor based on such a principle has low-speed and high-torque motor characteristics and is suitable for high-precision rotation and high-precision positioning. The friction material used for the friction contact portion of such a vibration wave motor generally has good wear resistance,
It is desirable that the coefficient of friction is large and stable.

Conventionally, various kinds of friction materials have been proposed.
JP-A-239442 and JP-A-4-49872 disclose that a resin material containing carbon fiber is suitable for a friction material for a vibration wave motor because of its good abrasion, long durability life and stable friction coefficient. It is disclosed as a material.

[0010]

However, as the vibration wave motor is used for various applications, the performance of the vibration wave motor under various environments has been evaluated. It has been found that the wear resistance of the friction material, that is, the amount of wear of the friction material changes significantly. For this reason, it has been found that the life of the vibration wave motor greatly depends on the durability life of the friction material, and in particular, is greatly affected by the change in humidity in the use environment.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide a vibration wave motor that is stable against the influence of humidity changes in an environment of low humidity or high humidity, or in an environment with a change in humidity. An object of the present invention is to provide a friction material for vibration, a vibration wave motor and a device using the same.

[0012]

That is, the present invention relates to a vibration member which forms a vibration wave in a vibration wave motor, and a friction member which comes into frictional contact with the vibration member and moves relative to the vibration member by vibration. A friction material for a vibration wave motor, which is a friction material used for a contact portion and is made of a resin composition containing a heat-resistant resin and mesophase pitch-based carbon fibers.

Further, the present invention relates to a vibration wave motor having a vibrating body for generating vibration, and a contact body which comes into frictional contact with the vibrating body and moves relatively to the vibrating body by vibration.
A vibration wave motor characterized in that the friction material is provided on at least one friction contact portion of the vibration body or the contact body. Further, the present invention is an apparatus provided with the above-mentioned vibration wave motor as a driving source.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
A friction material for a vibration wave motor according to the present invention is used for a frictional contact portion between a vibration body that forms a vibration wave in a vibration wave motor and a contact body that makes frictional contact with the vibration body and relatively moves with the vibration body by vibration. A friction material, wherein a specific resin composition is used for the friction material.

That is, the friction material for the vibration wave motor of the present invention is characterized by using a material made of a resin composition containing a heat-resistant resin and mesophase pitch-based carbon fibers.

The friction material in the vibration wave motor of the present invention is
By using a resin material in which the type of carbon fiber contained in the material is limited to mesophase pitch-based carbon fiber, a change in the amount of wear of the friction material due to a change in humidity is minimized.

The heat-resistant resin contained in the resin composition used for the friction material of the present invention includes fluorine resin, polyimide resin, alkyd resin, polyester resin, acrylic resin, amino resin, polyamide resin, epoxy resin, phenol resin. , A urea resin, a polyurethane resin, a polyamideimide resin, a polyetherimide resin, and a silicone resin. Among these resins, a fluororesin and a polyimide resin are preferable, and a fluororesin is particularly preferable. Since these resins have high durability, heat resistance, and hydrophobicity, friction characteristics optimal for a vibration wave motor can be obtained. Also,
The durability can be improved by adding other additives, for example, organic or inorganic fibers to the heat-resistant resin. In addition, another effect can be expected from the addition of a solid lubricant by reduction.

As the mesophase pitch-based carbon fibers contained in the resin composition used in the friction material of the present invention, mesophase pitch-based carbon fibers among the pitch-based carbon fibers are used.

That is, in general, the properties of carbon fibers are greatly affected by the starting materials, and are often distinguished by the names of the starting materials. At present, acrylic fibers (polyacrylonitrile, hereafter,
PAN-based carbon fiber starting from “PAN”) and pitch-based carbon fiber produced from pitch obtained by heat-treating tar or crude oil distilled or pyrolyzed residual oil obtained during coal dry distillation by heat treatment. There are two types, the share of which is overwhelmingly PAN-based carbon fiber, but most of the commercially available inexpensive and general-purpose carbon fiber is pitch-based carbon fiber. The graphite is further classified into those that have been graphitized to be graphitic and those that have not been graphitized.

The pitch-based carbon fiber is further divided into two types. When the pitch is heated to change from a liquid phase to a solid phase, a mesophase which generates an optically anisotropic liquid crystal phase (mesophase) is generated. Carbon fibers made from pitch are called mesophase pitch-based carbon fibers, and those made from optically isotropic pitch without generating mesophase are called and distinguished from isotropic pitch-based carbon fibers. The difference between the anisotropy and the isotropicity shows a remarkable difference in the orientation and degree of the microstructure (crystallite) of the carbon material, and greatly changes the properties of the carbon fiber. In particular, in the mesophase pitch system, the microstructure of the carbon fiber has a remarkable orientation in the axial direction and its cross-sectional direction, and as a result, its mechanical properties, such as tensile modulus and compressive strength, may be increased. It is possible and is attracting attention as a material property.

However, from the mechanical properties of these carbon fibers, it is very difficult to predict general friction and wear phenomena as well as special friction and wear phenomena in vibration wave motors. By manufacturing and evaluating using a vibration wave motor and examining the difference, when the usage environment of the humidity condition of the vibration wave motor changes, mesophase pitch-based carbon fiber is the most suitable material that is not easily affected by humidity. I found something.

As a specific example of the mesophase pitch-based carbon fiber used in the present invention, carbonaceous materials are available under the trade name MC-
249, Osaka Gas Co., Ltd., and the graphitized graphite is MGII-249, Osaka Gas Co., Ltd.
Is mentioned.

In the present invention, the content of the mesophase pitch-based carbon fibers in the resin composition is usually 2 to 50% by weight, preferably 5 to 40% by weight, more preferably 10% by weight.
-30% by weight is desirable. If it is less than 2% by weight, the friction material is easily affected by humidity, and if it exceeds 50% by weight, the strength of the resin composition is undesirably reduced.

[0024] In addition to the above components, other additives can be added to the resin composition of the present invention, if necessary. Examples of the additive include a solid lubricant such as molybdenum trisulfide, carbon powder, and PTFE powder; a polymer material such as a polyimide powder and other highly heat-resistant material powder; and an alumina, silicon carbide and other inorganic material powder. It is preferable to add these additives because durability, stability of friction and wear, and other various properties can be improved.

According to the vibration wave motor of the present invention, there is provided a vibration wave motor comprising: a vibrating member for forming vibration; and a contact member which comes into frictional contact with the vibrating member and moves relative to the vibrating member by vibration. A friction material made of a resin composition containing the above heat-resistant resin and mesophase pitch-based carbon fiber is provided on at least one friction contact portion of the body or the contact body.

FIG. 1 is a sectional view showing an embodiment of the vibration wave motor of the present invention. In the drawing, reference numeral 1 denotes a vibrating body, and two groups of ring-shaped polarized piezoelectric elements 4 as described above are heat-resistant on an end surface of a ring-shaped metal elastic body 3 made of stainless steel. Glued with an adhesive, metal elastic body 3
A friction material 5 is similarly adhered to the other end face of.

On the other hand, a friction material 6a is provided on the friction sliding surface of the ring-shaped contact body 6 made of an aluminum alloy on the moving body 2 side. The contact member 6 is supported by a support member 8 via a rubber ring 7.
The support 8 is attached to the output shaft 12 by screws 11.
It is fixed to. Then, the friction material 5 of the vibrating body 1 and the friction material 6a of the contact body 6 come into contact with each other to form a friction sliding surface, and are pressed by a plate spring 16 for pressing with a total pressure of 5 kgf in the axial direction. ing. 9 is a bearing, 13 is a cover, 1
Reference numerals 4 and 15 denote pressurized collars, and 17 denotes a collar, which is fixed to the output shaft 12 by a screw 11a.

An example of the shape of the friction material 5 is as follows.
Is provided with a circumferential step 5a, the height C of which is 0.15 mm.
It is. The width a of the contact portion (sliding surface) between the friction materials 5 and 6a in FIG. 1 is 0.8 mm, and the diameter b of the contact portion (sliding surface) is 30 mm.

When an AC voltage having a specific frequency is applied to the vibrating body 1 to the two groups of piezoelectric elements 4 alternately polarized in the thickness direction, the vibrating body 1 resonates, and the vibrating body 1 vibrates progressively in its circumferential direction. A wave is generated, and a frictional force acts on the friction material 6a via the friction material 5, so that the moving body 2 is driven to rotate.

The friction material of the present invention may be used for both of the friction materials 5 and 6a, or may be used for either one of them. When the friction material of the present invention is used for one, a normal friction material can be used for the other. Examples of ordinary friction materials include aluminum-silicon alloys that are hard, tough, and hardly wear, hardened steel, ceramics, and cemented carbides.

As described above, in the configuration of the present invention, at least one of the contact member and the vibration member of the vibration wave motor is brought into friction contact with the friction material made of the resin composition containing the heat-resistant resin and the mesophase pitch-based carbon fiber. Since the vibration motor is made of a material, the vibration motor can be driven stably under the influence of humidity changes in the environment of low humidity and high humidity, and the environment where the humidity changes. Stabilization is also possible, and the credibility of the vibration wave motor can be further improved.

Further, the present invention can be used for various devices using a vibration wave motor provided with the above friction material as a drive source. Specific examples of devices include optical devices such as cameras,
Office equipment such as printers and copiers, power windows,
Automotive-related devices such as active suspensions.

[0033]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 A friction material was produced as follows. 80% by weight of polytetrafluoroethylene (hereinafter referred to as PTFE) resin powder
After uniformly dispersing and mixing 20% by weight of the carbon fibers (short fibers) and the graphitized carbon fibers (short fibers) shown in Table 1, the mixture was press-pressed at a pressure of 500 kg / cm ² to have a diameter of 8 c.
m, inner diameter 1cm, height 10cm, and temperature 3
It was fired at 60 ° C. for 3 hours to obtain a cylindrical fired body. The cylindrical fired body is cut by a cutting device and has a thickness of 0.5 mm.
Was produced. The sheet was stamped and used as the ring-shaped friction material 5 in FIG.

The size of the carbon fiber used was about 1 in diameter.
It is a short fiber having a length of 0 μm to 13 μm and a length of about 100 μm to 130 μm.

[0036]

[Table 1]

(Note 1) In Table 1, No. Nos. 1 and 2 show the examples. 3, 4, and 5 (* marks) indicate comparative examples. (Note 2) In Table 1, sample No. As the mesophase pitch-based carbon fiber No. 1, MC-249 (trade name) manufactured by Osaka Gas Co., Ltd. was used. Sample No. For the mesophase pitch system 2 and the graphitization treatment of No. 2, MGII-249 (trade name) manufactured by Osaka Gas Co., Ltd. was used. Sample No. The isotropic pitch-based carbon fiber No. 3 used was trade name SG-249, manufactured by Osaka Gas Co., Ltd. Sample No. 4 isotropic pitch system + graphitization treatment is trade name LX
X-941, manufactured by Osaka Gas Co., Ltd. was used. Sample N
o. The polyacrylonitrile-based carbon fiber No. 5 used was a trade name, trade name MLD-300, manufactured by Toray Industries, Inc.

In Table 1, no. Nos. 1, 3, and 5 are obtained after spinning, infusibilizing or stabilizing each raw material (8 in an inert atmosphere).
No. 00-1200 ° C.), carbonized and carbonaceous fiber. 2 and 4 are 2 in an inert atmosphere
It is a fiber that has been graphitized at 000 to 3000 ° C. and has become graphitic.

As shown in FIG. 1, the friction material 5 has a circumferential step 5a provided on the friction material 5 and has a height c of 0.15.
mm. The width a of the contact portion (sliding surface) between the friction materials 5 and 6a in FIG. 1 is 0.8 mm, and the diameter b of the contact portion (sliding surface).
Is 30 mm.

The friction material 5 is fixed to the metal elastic body 3 made of stainless steel with an adhesive (an epoxy thermosetting type).
The vibration wave motor shown in FIG. 1 was manufactured by using a friction material 6a of the contact body 6 made of aluminum material made of a tungsten carbide material containing cobalt by spraying.

The evaluation of the friction material described below is a value obtained by driving the vibration wave motor continuously at a rotation speed of 300 rpm and a torque of 300 g-cm for 100 hours. The result is shown in FIG.

FIG. 2 shows a friction material made of a PTFE material containing each carbon fiber shown in Table 1 at a temperature of 40.degree.
The amount of wear of the friction material 5 after driving for 100 hours when it is changed to 95% is shown. The amount of abrasion is measured by measuring the height of the step 5a in FIG.
It is a value obtained by subtracting the height after driving from the height of.

As can be seen from FIG. The friction materials of Nos. 1 and 2 are other Nos. Change (increase) in wear at low and high humidity compared to the friction material of 3 to 5 compared to the humidity of 40 to 70%
Was very low. In addition, No. 2
Is No. Compared with No. 1, the amount of wear is large as a whole. No. No. 2 is a graphite material, and it is considered that the hardness was relatively soft and the wear was relatively large.

Example 2 In the same manner as Example 1, 1 to No. 5 and the resin material was a polyimide resin, and 88% by weight of the polyimide resin powder and carbon material 1 were used in the same manner as in Example 1.
2% by weight are uniformly dispersed and mixed,
8cm diameter at a molding pressure of 00kgf / cm ^2, an inner diameter 1c
m, temperature of 350 ° C while forming into a cylindrical shape with a height of 10cm
For 10 minutes, and the cylindrical fired body obtained was cut to produce a sheet having a thickness of 0.5 mm. The sheet was punched and used as a ring-shaped friction material 5 in FIG. 1 for a vibration wave motor, and the same evaluation as in Example 1 was performed.
The result is shown in FIG. In FIG. Nos. 1 and 2 show the examples. 3, 4, and 5 show comparative examples.

As shown in FIG. 3, the abrasion amount of the friction material is generally larger than that of the first embodiment, indicating that the polyimide resin is affected by humidity. As in the case of Example 1, the amount of wear tends to increase as compared with the case where the humidity is 40% to 70%. This suggests that the change in the amount of wear due to the influence of humidity is basically due to the difference in the type of carbon fiber. However, as for the phenomenon of friction and wear, the difference between the resin materials is shown in Examples 1 and 2. For example, the friction coefficient of the polyimide resin is about 0.4, which is larger than the friction coefficient of the fluorine resin of 0.2. Therefore, the torque of the motor is large and the performance is good, but the fluctuation of the friction coefficient of the polyimide resin is ± 0.1 and the fluctuation of the motor torque and rotation is increased compared to ± 0.03 of the fluororesin. ing.

In addition, solid lubricants such as molybdenum disulfide, polymer materials such as polyimide powder, and inorganic materials such as alumina were added to the resins of Examples 1 and 2 as a small amount of additive materials to provide durability and friction and wear. And various other properties. In particular, the material to which molybdenum disulfide or polyimide powder is added is No. 1 in FIG. 1. N in FIG.
o. 1 showed a lower wear amount.

In each of the first and second embodiments, the friction material 6a, which is a mating material of the resin material, is a hard coating, hardly generates wear, and is judged to have no influence on the evaluation. Similar results were obtained when other hard materials such as ceramics were used.

The friction material of the present invention can be used for either one of the friction material 5 and the friction material 6a. In the first and second embodiments, the friction material 5 and the friction material 6a are replaced respectively.
The friction material of the present invention may be used for the friction material 6 a of the contact body 6, and a hard coating or the like may be used for the friction material 5 of the metal elastic body 3. Further, the friction material of the present invention may be used for both the friction material 5 and the friction material 6a.

In the above embodiment, the friction material is applied to the disk-shaped vibration wave motor shown in FIG. 1. However, the friction material is provided to the rod-shaped vibration wave motor by the same method. May be formed.

FIG. 4 is a schematic diagram of a device using the vibration wave motor shown in FIG. 1 as a driving source. 23 is a large gear 23
a and a small gear 23b, and the large gear 23a meshes with the gear 20 on the vibration wave motor side. Reference numeral 24 denotes a driven member, for example, a lens barrel, and a gear 24 provided on an outer peripheral portion.
The small gear 23b of the gear 23 meshes with a and rotates by the driving force of the motor. On the other hand, an encoder slit plate 25 is attached to the gear 23, and the rotation of the gear 23 is detected by the photocoupler 26, and the rotation and stop of the motor are controlled, for example, for autofocus.

[0051]

As described above, according to the present invention, the use of the mesophase pitch-based carbon fiber as the carbon fiber contained in the resin as the friction material enables the vibration under the environment of low humidity or high humidity. In addition to being able to use the wave motor for a long period of time, the life of the vibration motor can be stabilized in an environment where there is a change in humidity, which has the effect of further increasing the reliability of the vibration wave motor. Further, the present invention can provide an apparatus using a vibration wave motor having excellent friction characteristics against the above-mentioned change in humidity.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing the relationship between the amount of wear and humidity of a friction material made of a fluororesin containing carbon fibers of Example 1 of the present invention.

FIG. 3 is a graph showing a relationship between a wear amount and a humidity of a friction material made of a polyimide resin containing carbon fibers according to a second embodiment of the present invention.

FIG. 4 is a schematic view of a device that uses the vibration wave motor shown in FIG. 1 as a driving source.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vibration body 2 Moving body 3 Metal elastic body 4 Piezoelectric element 4 5 Friction material 6 Contact body 6a Friction material 8 Support body 9 Bearing 11, 11a Screw 12 Output shaft 13 Cover 14, 15 Pressurized collar 16 Leaf spring 17 Color

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Claims (8)

[Claims] 1. A friction material used for a frictional contact portion between a vibrating body that forms a vibration wave in a vibration wave motor and a contact body that comes into frictional contact with the vibrating body and moves relatively to the vibrating body by vibration. A friction material for a vibration wave motor, comprising a resin composition containing a conductive resin and mesophase pitch-based carbon fibers. 2. The friction material for a vibration wave motor according to claim 1, wherein the mesophase pitch-based carbon fibers are carbonaceous. 3. The friction material for a vibration wave motor according to claim 1, wherein the mesophase pitch-based carbon fibers are made of short fibers. 4. The content of mesophase pitch-based carbon fibers in the resin composition is 10 to 30% by weight.
4. The friction material for a vibration wave motor according to any one of items 1 to 3. 5. The friction material for a vibration wave motor according to claim 1, wherein the heat-resistant resin is made of a fluorine resin or a polyimide resin. 6. The resin composition according to claim 1, wherein said resin composition contains at least one of molybdenum disulfide and polyimide powder.
A friction material for a vibration wave motor as described in the above. 7. A vibration wave motor having a vibrating body that forms vibration and a contact body that comes into frictional contact with the vibrating body and moves relative to the vibrating body by vibration, wherein at least one of the vibrating body and the contacting body is provided. 7. A method according to claim 1, wherein one of the friction contact portions is provided.
A vibration wave motor provided with the friction material according to any one of the above items. 8. An apparatus provided with the vibration wave motor according to claim 7 as a drive source.