JP2000167946A - Friction material, and oscillatory wave motor and instrument using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction material excellent in abrasion characteristics not peeled from an adhesive surface during driving and not generating an abnormally large quantity of abrasion at an initial stage of driving. SOLUTION: A friction material is used in the frictional contact part of an oscillating member forming oscillatory waves of an oscillatory wave motor and the contact member coming into frictional contact with the oscillating member and relatively moved along with the oscillating member by oscillation. In this case, a molded body based on fluoroplastic prepared by the compression molding of a fluoroplastic powder and other additives is baked to form a baked body which is, in turn, cut into a sheet shape to form a sheet 32 and the processing modified layer 33 generated on the surface of the sheet 32 by cutting processing is removed.

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 friction material, and a device.

[0002]

2. Description of the Related Art In general, a vibration wave motor causes a circular or elliptical motion at each point on the surface of a vibrating body, and frictionally drives a contact body pressed against the point.

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 another group (hereinafter, referred to as a B phase), a standing wave is similarly generated. The phase is shifted by λ / 4 in position.

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 combination of the standing waves of the two, the elastic body is moved in the circumferential direction. A traveling wave (wavelength λ) of the vibrating bending vibration is generated, and at this time, each point on the surface of the elastic body having a thickness performs an elliptical motion.

Accordingly, 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 circumferential friction from the vibrating body. The rotation is driven by the force.

[0009]

A wide variety of friction materials for a vibration wave motor have been proposed in the past. For example, Japanese Unexamined Patent Publication No.
Composite materials such as fluororesin and reinforced fiber or polymer material as described in JP-A-1297981, JP-A-1-206880 and the like have excellent abrasion resistance and are suitable for vibration wave motors due to long-term durability and stable friction coefficient. Is disclosed as a material suitable for the friction material.

As a method for producing such a fluororesin composite material, a method utilizing a compression molding method is generally known. This involves uniformly mixing the fluororesin powder and other material powders, filling them into a mold and pressing them to produce a molded body, usually a cylinder, and then firing the molded body at the melting point of the fluororesin or higher. Thereafter, the outer peripheral surface of the fired body is cut by cutting to remove the cylindrical outer peripheral surface as if peeling the toilet paper shape, thereby obtaining a sheet-like composite material. After forming the sheet, it has been attempted to punch the sheet into an appropriate size, adhere to a vibrating body or a contact body, and use the sheet as a friction material.

However, when the above-mentioned sheet-like fluororesin composite material is used as a friction material for a vibration wave motor and the vibration wave motor is driven, an abnormally large amount of wear occurs on the surface of the friction material. A fatal problem occurred such as the adhered friction material coming off during driving of the vibration wave motor.

An object of the present invention is to solve the above-mentioned problems of the prior art, and by using a specific sheet-like fluororesin-based material produced by cutting as a friction material for a vibration wave motor, It is an object of the present invention to provide a friction material excellent in wear characteristics in which the friction material does not peel off from the bonding surface during driving and the friction material does not cause abnormally large amount of wear in the initial stage of driving.

Further, according to the present invention, stable driving is possible,
It is an object of the present invention to provide a vibration wave motor having a long life and a device using the same.

[0014]

That is, the present invention provides a vibrating body for forming a vibration wave of a vibration wave motor, and a frictional contact between the vibrating body and a contact body which is in frictional contact with the vibrating body and moves relative to the vibrating body by vibration. Is a friction material used for the part, and after sintering a molded body mainly composed of a fluororesin obtained by compression-molding a fluororesin powder and other additives into a fired body, a sheet is formed by cutting into a sheet shape. And a friction material obtained by removing a work-affected layer generated by cutting the surface of the sheet.

It is preferable that the convex surface side of the sheet curled by the cutting process is bonded to the vibrating body or the contact body. Preferably, the other additives are powders and / or fibers of an inorganic or organic material.

The present invention also provides a vibration wave motor having a vibrating body for forming a vibration wave and a contact body which makes frictional contact with the vibrating body and moves relative to the vibrating body by vibration. A vibration wave motor characterized in that at least one of the friction contact portions is provided with the friction material.

Further, the present invention is an apparatus characterized in that the above-mentioned vibration wave motor is provided as a driving source.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A friction material according to the present invention comprises a vibrating member for forming a vibration wave of a vibration wave motor, and a frictional contact portion between a vibrating member and a contact member which moves relative to the vibrating member due to vibration. A friction material to be used, after firing a molded body mainly composed of a fluororesin obtained by compression-molding a fluororesin powder and other additives to form a fired body, and cutting the sheet into a sheet to form a sheet, The method is characterized in that a damaged layer generated by cutting the surface of the sheet is removed.

According to the vibration wave motor of the present invention, a vibration member which forms a vibration wave in the vibration wave motor is in frictional contact with the vibration member, and a frictional contact portion (frictional contact) between the vibration member and the contact member relatively moving by vibration. As a friction material used for the surface), a fluororesin composite material containing a fluororesin as a main component and a fluororesin powder and other additives is formed into a cylindrical shape by a compression molding method, and then fired and cut to form a cylindrical outer periphery. After the surface is cut into a sheet and punched as a friction material of an appropriate size, the punched sheet is bonded to a vibrating body or contact body to make it a friction material, and it is generated by cutting the surface of the friction material By removing the work-affected layer and using it as a friction material, it becomes possible to eliminate a large amount of abnormal wear caused when the vibration wave motor is vibrated.

In addition, the friction material is bonded to the vibrating body or the contact body on the convex side of the curled (curved) sheet by cutting, so that peeling after bonding can be eliminated.

Further, the friction material to which powder and / or fiber is added in addition to the fluororesin can further improve the friction and wear characteristics of the friction material and can reduce the amount of wear.

Hereinafter, the present invention will be described with reference to the drawings.
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. A friction material 5 was similarly adhered to the other end face of the metal elastic body 3 by using an adhesive.

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 plate for fixing the vibrating body, 14 and 15 are pressurized collars, and 17 is a collar, which is fixed to the output shaft 12 by a screw 11a. 1
8 is a cover.

The sheet-like friction material 5 has a circumferential step 5.
a is provided by machining. Further, the friction material 5 shown in FIG.
The width a of the contact portion (friction surface) between the contact portions 6a and 6a is 0.8 mm, and the diameter b of the contact portion (sliding surface) is 30 mm.

When an alternating 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 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 hard and tough aluminum-silicon alloys, hardened steels, ceramics, and cemented carbides with little wear. In this embodiment, the friction material 5 is made of a fluororesin composite material. In addition, ceramics (alumina) was used for the friction material 6a.

[0027]

The present invention will be described in detail below with reference to examples.

Example 1 A friction material was manufactured as follows. 76% by weight of fluororesin powder (polytetrafluoroethylene PTFE, manufactured by Daikin Industries, trade name: Polyflon M-12); 20% by weight of carbon fiber (manufactured by Osaka Gas Co., trade name: SG-249); polyimide powder (Ube Industries, Ltd.) Made, trade name UIP-
S) A raw material powder composed of 4% by weight was uniformly mixed with a Hexchel mixer, filled in a mold, and pressed with a pressure of 5%.
Pressing uniformly at 00 kg / cm ^{2 and} compression molding, outer diameter 2
A cylindrical molded body having a length of 0 cm, an inner diameter of 5 cm, and a length of 12 cm was prepared. Then, it was fired at a temperature of 380 ° C. for 3 hours to obtain a fired body. Next, as shown in FIG. 2, while rotating the fired body 30 with a lathe, a 15 cm wide carbide cutting blade 31 is applied to the outer peripheral surface of the fired body 30 and rotated to a thickness of 0.5 mm. The sheet 32 was cut out as if peeling off the outer peripheral surface of the fired body by using a device in which the movement of the blade and the fired body in the center direction were synchronized.

Thereafter, the sheet 32 was punched in a ring shape using a punching die having a Thomson blade embedded therein and a press to obtain the friction material 5 shown in FIG.
Since the surface of the sheet is mainly made of a fluororesin before bonding, the fluororesin is chemically decomposed using a surface treatment agent to improve the adhesiveness. If such a surface treatment is not performed, the peel strength by adhesion is 1/5 to 1/1.
As weak as 10, surface treatment is indispensable for improving adhesive strength.

However, as described in the conventional example,
The friction material manufactured as described above sometimes came off partially during driving of the vibration wave motor. Then, when the cause was investigated, it turned out that there were the following problems.

That is, the sheet 32 is affected by mechanical strain and heat by the cutting, and as shown in FIG. 2, after the cutting, the sheet 32 curls in the longitudinal direction. This curl will not go away if left alone. Then, as shown in FIG.
The friction material 5 punched out from 2 is coated in advance with an epoxy-based two-liquid adhesive 33 on the bonding surface of the metal elastic body 3, the friction material 5 is placed on the bonding surface, and pressed from the upper surface of the friction material 5 by a flat plate, Although the adhesive was held and bonded until the adhesive was cured, when the curl concave surface of the friction material 5 was bonded to the bonding surface and bonded, as shown in FIG. When the sheet comes into contact with the metal elastic body 3 and the sheet is further pressed down, the outer peripheral side of the sheet hardly moves, and the inner peripheral side is directly pressed from above.
It was found that air bubbles and uneven thickness of the adhesive layer were likely to occur in the adhesive layer made of.

Then, as shown in FIG. 3 (b), when the sheet is bonded with the convex surface of the curl of the sheet as the bonding surface, the curled sheet first hits on the inner peripheral side, and when the sheet is further pressed down, the sheet becomes It was found that defects were unlikely to occur because the adhesive gradually came into contact with the outer peripheral side while extruding excess adhesive 33 and bubbles to the outside.

In the friction material thus formed, the peeling of the friction material during driving of the motor was drastically reduced. In addition, after the friction material 5 is adhered to the metal elastic body 3, a portion other than the protrusion 5 a is formed by shaving the protrusion 5 a of the friction material 5. This facilitates discharge of abrasion powder by forming a convex shape, but a convex portion may not be provided depending on the specifications of the motor.

Further, as described in the conventional example, a large amount of abrasion of the friction material often occurred in the early stage of driving the motor. This abnormal phenomenon is caused by the fact that the wear of the normal friction material during driving of the motor is 0.05 to 0.1 / hour.
08 μm / h, but 0.3-5
This is a phenomenon in which abnormal wear progresses at a speed of 50 to 100 times as fast as μm / h, and motor performance (speed and torque) becomes unstable. Observation of the surface and cross section of the cut sheet showed that the affected layer caused by the cutting had an effect. This is because the carbon fiber on the sheet surface breaks or breaks off due to the cutting resistance due to the cutting process and the heat generated thereby, and the polyimide powder also falls off or breaks, especially the flank surface of the cutting blade in the cutting process. (Corresponding to the concave side of the curl) is severe. Further, not only the carbon fiber but also the fluororesin in the processed deteriorated layer causes surface irregularities, minute cracks, and deterioration of the fluororesin which is considered to be caused by heat.

As shown in FIG. 4, these deteriorated layers 33 are processed.
Is at least about 50 μm on the convex side of the curl and at least 100 μm on the concave side when the sheet thickness is 0.5 mm.
m. For example, after the sheet is bonded to the elastic metal body, the surface of the friction material 5 or the surface of the protrusion 5a in FIG. Evaluated by a vibration wave motor with the surface of the friction material 5 shown in FIG. 1 as a healthy friction surface by removing the affected layer by grinding with cooling using a grindstone or wrapping with a wrapping sheet. As a result, the wear was stable and the motor performance was stable from the beginning.

As can be seen from the above, from the observation of the surface and cross section of the sheet, a large amount of abrasion powder is likely to be generated in a short period of time in the early stage of operation, and a large amount of abrasion powder generated in the initial stage is used as the base layer. It is considered that the large amount of wear of the resin material will be further accelerated, and it is essential that the initial friction surface be a sound surface without a work-affected layer in order to eliminate abnormally large amounts of wear. Was done.

As described above, in order to put the material formed by molding, firing, and cutting the powder mainly composed of the fluororesin into a sheet by cutting, to be practically used as a friction material for the vibration wave motor, it is necessary to remove the above-mentioned deteriorated layer. It is.

The friction material used in the present invention contains a fluororesin as a main component, a fluororesin powder and other additives. As other additives, a powder or a powder made of a heat-resistant polymer material is preferable, for example, a polyimide resin, a polyamideimide resin, a polyetheretherketone resin, a polyphenylene sulfide resin,
Examples thereof include a silicone resin, a polyparaoxybenzoyl resin, an epoxy resin, a phenol resin, a polycarbonate resin, and a polyphenylene oxide resin. Among these resins, a polyimide resin having the highest heat resistance is preferable. These resins have high wear resistance and stable friction and wear characteristics, and are optimal as friction materials for vibration wave motors.

Further, by adding inorganic or organic fibers as a reinforcing material to the friction material in addition to the above heat-resistant polymer material, it is possible to obtain higher wear resistance and stable friction and wear characteristics. it can. Among them, carbon fibers, which are inorganic fibers, are most preferable because the friction coefficient is stable and the amount of wear is small.

In addition, the friction material used in the present invention is:
It is also preferable to add other materials, if necessary, other than the above-mentioned fluororesin and heat-resistant polymer fiber. Examples of the inorganic powder include a solid lubricant such as molybdenum sulfide powder and carbon powder, alumina powder and silicon oxide powder. When these materials are added, the properties of the friction material can be changed according to various specifications of the vibration wave motor.

The proportion of the fluororesin that can be compression-molded is at least 50% by weight, preferably 70 to 90% by weight. In addition, the ratio of other additives is 50% by weight or less,
Preferably it is 2 to 10% by weight. If the amount of the additive is further increased, the material itself becomes brittle, and the strength and the like are undesirably reduced. This is because, in compression molding, the fluororesin has a role of a binder, and the lower the fluororesin, the lower the holding power to the additive. For this reason, when the ratio of the fluororesin is small (the amount of the additive is large), the thickness of the deteriorated layer formed by the cutting increases.

As described above, according to the present invention, at least one of the vibrating body and the contact body of the vibration wave motor is brought into frictional contact with the friction material, and the friction material of the sheet material prepared by compression-molding the mixed fluororesin and other additive materials. Since the deformed layer on the contact surface is removed and the convex side of the sheet curl is adhered to the vibrator or contact body, the friction material does not come off from the adhered surface during driving as a vibration wave motor, and the initial drive In addition, the friction material can be driven stably without abnormally large abrasion, the life of the vibration wave motor can be extended, and the reliability of the vibration wave motor can be further improved.

The present invention can be applied to various devices as shown in FIG. 4 using the vibration wave motor provided with the friction material as a drive source.

FIG. 4 is a schematic view 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.

Specific examples of the equipment include optical equipment such as a camera, office equipment such as a printer and a copying machine, and automobile-related equipment such as a power window and an active suspension.

[0046]

As described above, according to the present invention, after a composite material mainly composed of a fluororesin powder is compression-molded, the calcined body is cut into a sheet shape, and then a sheet material is formed. By using it as a friction material, the friction material does not peel off from the adhesive surface during driving, and the friction material does not cause abnormally large amount of wear in the initial stage of driving It can be provided at low cost.

Further, the present invention uses the above-mentioned friction material,
It is possible to provide a vibration wave motor having excellent wear characteristics, stable driving, and a long life. Further, the present invention can provide an apparatus using the vibration wave motor having the above-mentioned excellent frictional characteristics.

[Brief description of the drawings]

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

FIG. 2 is an explanatory view showing a method for producing a friction material of the present invention.

FIG. 3 is an explanatory view showing a situation in which the friction material of the present invention is bonded to a metal elastic body.

FIG. 4 is an explanatory view showing a damaged layer of the friction material of the present invention.

FIG. 5 is a schematic diagram of a device using 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 5 Friction material 8 Support body 9 Metal elastic body 11, 11a Screw 12 Output shaft 13 Plate 14, 15 Pressurized collar 16 Leaf spring 17 Color 19 Bearing 30 Fired body 31 Cutting Blade 32 sheet

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 4F213 AA16 AB16 AB19 AB25 AC04 AE08 AE10 AH04 AH05 WA04 WA15 WA22 WA53 WA65 WA90 WB01 WC01 5H680 AA00 AA12 BB03 BB16 BB17 BC01 BC04 BC05 CC02 CC06 CC07 DD01 DD02 DD15 DD23 DD27 DD27 DD73 DD82 DD87 DD88 EE03 EE12 FF04 FF08 FF12 FF13 FF14 FF20 FF26 FF33 GG11 GG14 GG15 GG20 GG21 GG25 GG27 GG42 GG43

Claims (5)

[Claims] 1. A friction material used for a frictional contact portion between a vibrating body that forms a vibration wave of a vibration wave motor and a contact body that makes frictional contact with the vibrating body and moves relative to the vibrating body by vibration. After sintering a molded body mainly composed of a fluororesin obtained by compression-molding powder and other additives into a fired body, a sheet is formed by cutting into a sheet, and the sheet is formed by cutting the surface of the sheet. A friction material obtained by removing a deteriorated layer that has been processed. 2. The friction material according to claim 1, wherein the convex side of the sheet curled by the cutting is bonded to the vibrating body or the contact body. 3. The friction material according to claim 1, wherein the other additive is powder or fiber of an inorganic or organic material and / or fiber. 4. A vibration wave motor having a vibrating body for forming an oscillating wave, and a contact body that comes into frictional contact with said vibrating body and moves relative to said vibrating body by vibration, wherein at least one of said vibrating body and said contacting body has friction. A vibration wave motor comprising a friction member according to any one of claims 1 to 3 provided in a contact portion. 5. An apparatus provided with the vibration wave motor according to claim 4 as a drive source.