JP3403100B2 - Manufacturing method of friction material used for vibration wave motor - Google Patents

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 method for manufacturing the friction material, and a vibration wave motor and equipment using the friction material.

[0002]

2. Description of the Related Art Generally, 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 by the circular or elliptical motion.

The principle outline of a vibration wave motor using progressive vibration waves is as follows. One in which two or more piezoelectric elements arranged in the circumferential direction are bonded to one surface of an elastic body formed in a ring shape from an elastic material such as metal whose total length is an integral multiple of a certain length λ Is a vibrating body (stator).

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

When an AC voltage is applied to only one of the groups (hereinafter referred to as the A phase), the vibrating body has an antinode at the center point of each piezoelectric element of the A phase and every λ / 2 point from the center point. A standing wave (wavelength λ) of bending vibration is generated over the entire circumference of the elastic body such that the center point between the positions and the position of the antinode is the node position.

Further, when an AC voltage is applied only to another group (hereinafter referred to as the B phase), a standing wave is generated in the same manner, but the antinodes and the positions of the nodes are different from those of the A phase. The phase is shifted by λ / 4 in terms of position.

When alternating signals having the same frequency and a temporal phase difference of 90 ° are simultaneously applied to both the A and B phases, the standing waves of the both are combined, and as a result, the elastic body moves in the circumferential direction. A traveling wave (wavelength λ) of the oscillating bending vibration is generated, and at this time, each point on the surface of the elastic body having a thickness makes an elliptic motion.

Therefore, if a ring-shaped contact body (for example, a rotor as a moving body) is directly brought into pressure contact with one surface of the vibrating body, the contact body is rubbed in the circumferential direction from the vibrating body. It receives force and is driven to rotate.

[0009]

A wide variety of materials have been proposed in the past as friction materials for vibration wave motors. As a material having the above-mentioned characteristics, for example, Japanese Patent Application Laid-Open No. HEI-1 is proposed.
As disclosed in JP-A-129781 and JP-A-1-206880, a composite material such as a fluororesin and a reinforced fiber or a polymer material has good wear resistance and is suitable for a vibration wave motor because of its long life and stability of 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 (press molding method) is generally known. This is a compression molding method in which fluororesin powder and other material powders are uniformly mixed, filled in a mold, and molded by pressing.After that, this molded body is baked at a temperature not lower than the melting point of fluororesin and solidified. A fluororesin composite material that is a fired body is used.

However, the rod-shaped fluororesin composite material to which carbon fiber is added, which has been prepared as described above, is cut (sliced) to form a round sheet having a thickness of about 0.5 mm, which is used for a vibration wave motor. When used as a friction material and observed how it wears, as the friction material gradually wears over the entire friction surface during driving of the vibration wave motor, fibrous carbon falls off in the form of fibers, and the friction material wears rapidly. It turned out to increase to.

Further, the friction material prepared by cutting such a bar material has an orientation in which most carbon fibers lie parallel to the cutting surface (slice surface), that is, lying down. It was also found as a result of the observation that it has. When this sliced material is used as a friction material, the frictional contact portion between the vibrating body and the contact body, that is, the frictional surface, coincides with the cut surface (slice surface) of the round bar in order to adhere to the ring-shaped metal part.
As a result, it was confirmed that the carbon fibers in the fluororesin were oriented in a lying state and, as described above, the fibers were easily slipped out and abrasion was increased.

Originally, the fluororesin has a small property of reacting with other materials and adhering to it, and the carbon fiber is, so to speak, mechanically embedded in the fluororesin. It was also found that carbon or carbon fiber with an extremely short length can easily fall out even by cutting it from a round bar, and it is also particularly remarkable when the fluororesin is porous or has a low specific gravity. Came.

An object of the present invention is to solve the above-mentioned problem of rapid and large amount of wear. By using a fluororesin composite material produced by a compression molding method as a friction material for a vibration wave motor, wear resistance is improved. A large amount of inexpensive and highly reliable friction material is provided at low cost.

[0015]

[0016]

That is, the present invention relates to friction between a vibrating body that forms vibration of a vibration wave motor and a contact body that is pressed against the vibrating body and comes into contact with the vibrating body to move relative to the vibrating body. In a method of manufacturing a friction material used for a contact surface , a fluororesin composite material is obtained by firing a molded body containing a fluororesin as a main component, which is obtained by compression molding fluororesin powder and a fibrous material.
After generating the
It is characterized in that it is carved from the part into a sheet shape
It is a thing.

The specific gravity of the fluororesin composite material is the theoretical specific gravity.
It is preferable to perform compression molding so that it is 80% or more of
Yes. Further, the fluororesin composite material is cylindrical or columnar,
It is preferable to cut the outer periphery into a sheet by cutting.
Good The fibrous material has a length of 50 μm to 350 μm.
It is preferable that the carbon fiber is μm. Also, the sea
Fibers contained in the friction material formed by carving into a shape
Material is oriented approximately perpendicular to the friction contact surface
Is preferred.

[0018]

[0019]

[0020]

[0021]

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a vibrating body forming the vibration of the vibration wave motor, in contact with the vibration pressurized to the vibrating body
In the method of manufacturing a friction material used for the frictional contact surface between the vibrating body and the contact body that moves relative to the vibrating body , the main component is the fluororesin obtained by compression molding the fluororesin powder and the fibrous material .
After firing the molded product to produce a fluororesin composite,
Fluorine resin composite material is turned into a sheet from the outer periphery by machining
It is characterized by shaving and molding.
The use of friction material can eliminate the occurrence of a large amount of wear.
Wear.

[0022]

Further, the friction material of the present invention is constituted by adding a fibrous material containing a fluororesin as a main component, and the fibers are oriented substantially perpendicular to the friction contact surface (friction surface). It is a friction material having a specific gravity of 80% or more with respect to the specific gravity, and by using the friction material, a large amount of abrasion can be eliminated, and the length of the fiber is 50 μm to 35 μm.
If a carbon fiber having a diameter of 0 μm and a diameter of several μm to 20 μm is used,
Its wear-preventing effect is great, and it is stable and has little wear as a friction material for a vibration wave motor.

The present invention will be described below with reference to the drawings.
FIG. 1 is a sectional view showing an embodiment of a vibration wave motor of the present invention. In the figure, reference numeral 1 is a vibrating body, and on one end face of a ring-shaped metallic elastic body 3 made of stainless steel, two groups of piezoelectric elements 4 each having a ring shape and polarized as described above are provided on a heat-resistant epoxy resin system. The metal elastic body 3 was bonded with an adhesive, and the friction material 5 was similarly bonded to the other end surface of the metal elastic body 3.

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 body 6 is a support body 8 via a rubber ring 7.
Mounted on the output shaft 12 by means of 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 contact each other to form a friction sliding surface, and the leaf spring 16 for pressurization applies a total pressure of 5 kgf in the axial direction. ing. Reference numeral 9 is a bearing, 13 is a plate for fixing the vibrating body, 14 and 15 are pressurizing 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-shaped friction material 5 has a circumferential step 5
a is provided by machining. Also, the friction material 5 of FIG.
And 6a, the width a of the contact portion (friction surface) is 0.8 mm, and the diameter b of the contact portion (sliding surface) is 30 mm.

When an alternating voltage having a frequency unique to the vibrating body 1 is applied to the two groups of piezoelectric elements 4 which are polarized in the thickness direction alternately, the vibrating body 1 resonates and progressive vibration occurs in the circumferential direction. A wave is generated and a frictional force acts on the friction material 6a via the friction material 5, and the moving body 2 is rotationally driven.

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 side, a normal friction material can be used for the other side. Usual friction materials include aluminum-silicon alloy, hardened, tough, and hardly worn, hardened steel, ceramics, cemented carbide, etc. In this embodiment, a fluororesin composite material is used as the friction material 5. In addition, ceramics (alumina) was used as the friction material 6a.

[0029]

EXAMPLES Examples will be described below in comparison with conventional examples to clarify the details of the present invention.

Example 1 A friction material was prepared as follows. Fluorine resin powder (polytetrafluoroethylene: PTFE, manufactured by Daikin Industries, Ltd., trade name: Polyflon M12) in 80% by weight of carbon fiber (short fiber: chip fiber, diameter of about 13 μm,
Length about 110 μm, manufactured by Osaka Gas Co., Ltd., trade name SG-24
9) After uniformly mixing 20% by weight with a hexshell mixer, the mixture was filled in a cylindrical mold and the pressure was 500 kg / c.
uniformly pressed by a press at m ^2, and compression molded, the outer diameter 2
A cylindrical molded body having 0 cm, an inner diameter of 5 cm and a length of 12 cm was prepared. Then, it baked at the temperature of 380 degreeC for 3 hours, and the baked body was obtained.

Thereafter, as shown in FIG. 2, while rotating the fired body 30 by a lathe, a carbide blade 21 having a width of 15 cm is applied to the outer peripheral surface of the fired body so that the thickness becomes 0.5 mm.
Cutting was performed using an apparatus in which the rotation of the fired body and the movement of the blade toward the center of the fired body were synchronized, and the sheet 32 was cut from the outer peripheral surface of the fired body as if peeling with a cutting blade.
The sheet 32 was curled (bent) due to the stress and heat generated by the cutting process and formed into a band shape.

Next, the sheet 32 is punched in a ring shape and bonded to the metal elastic body 3 in order to obtain the friction material 5 of FIG. 1 by using a punching die having a Thomson blade embedded therein and a press. The convex portion 5a of the friction material 5 was formed by machining.
The vibration wave motor provided with the friction material 5 is actually driven,
The evaluation was performed under a load of 300 g · cm and a rotation speed of 300 rpm. The amount of wear of the friction material 5 per 100 hours with 10 vibration wave motors was 5 to 8 μm / 100H.

The amount of wear was obtained by measuring the height of the convex portion 5a in advance, re-measured after evaluation, and taking the difference as the amount of wear. Moreover, the friction material 6a was scarcely worn.

Comparative Example 1 The same raw materials as in Example 1 were mixed in the same manner and then charged in a cylindrical mold different from that of Example 1, and the pressure was 500 k.
Pressurized uniformly at g / cm ² for compression molding, diameter 60m
A molded body of a round bar having a diameter of m, an inner diameter of 10 mm and a length of 12 cm was produced, and then fired under the same conditions as in Example 1 to obtain a fired body.

Then, the obtained round bar is attached to a lathe, and while being rotated, the round bar is cut (sliced) while being cut off in a radial direction with a cemented carbide knife-shaped blade to form a thin disc shape with a thickness of 0.5 mm. After obtaining the material of (1), the same punching and pressing as in Example 1 were used to punch and bond in a ring shape to obtain the friction material 5, and the convex portion 5a of the friction material 5 was scraped as in Example 1. I put it out. The vibration wave motor provided with the friction material 5 was evaluated under the same conditions. The wear amount of the friction material 5 per 100 hours of the 10 vibration wave motors was 22 to 35 μm / 100H.

The above Example 1 and Comparative Example 1 will be described. The difference in the amount of wear between Example 1 and Comparative Example 1 is considered to be due to the difference in the orientation of the carbon fibers contained in the fluororesin composite material with respect to the worn surface, as described above. In fact
When the behavior of the carbon fibers on the friction surface was examined with a microscope over time during the evaluation, it was found that in Example 1, the carbon fibers were oriented substantially perpendicular to the friction surface, and the carbon fibers were removed or moved due to friction. Is limited to a very small number of chips or a short length, whereas in Comparative Example 1, about half of the carbon fibers are parallel to the friction surface, and a relatively long number of 10 μm to 100 μm. It was also confirmed that the carbon fibers of a certain extent were moved so as to be swept away in the moving direction of the contact body (rotor), and in the worst case, the carbon fibers had completely fallen out. Since the molding and firing were performed under the same conditions and the specific gravities were both about 2.0, it is clear that the density of the materials is the same and the movement of the carbon fibers depends on the orientation of the carbon fibers.

Here, the reason why the orientation of the carbon fibers occurs will be described in more detail with reference to FIGS. 3 and 4. Figure 3
In, the mixed powder 33 in which the carbon fiber is mixed with the fluororesin powder is put into the cylindrical mold 34, and the two punches 3
5a and 35b are pressed from above and below (both shafts) (a single shaft press may be used, but in order to bring the molded body closer to a uniform density), and compression molding is performed. (See FIG. 3A) Here, a metal core 36 is provided on the mold 34. The molded body 37 obtained by pressing has a hollow cylindrical shape. (See Fig. 3 (b))

Usually, since the fluororesin powder has a low bulk density, the height b of the compact 37 obtained by compression molding is ⅓ to ⅕ of the height a of the mixed powder filled in the mold. Become. In other words, during the compression process, the fluororesin powder is gradually and largely compressed in the axial direction, and while the carbon fiber also moves and rotates, it is in a position more stable until it is finally compressed, that is, the compression of the press. Line up in a direction perpendicular to the direction.

FIG. 4 is a schematic view showing a fired body 30 obtained by firing the molded body 37. On the inner surface 38 of the fired body 30 obtained by firing the molded body 37 of FIG.
Most of them are parallel to the surface 38, that is, in a lying state (however, the axial direction of the fibers is random). Then, the outer peripheral surface of the fired body 30 is cut to form the sheet 32.
When the carbon fiber 39 is carved out, the axial direction of each carbon fiber 39 is just parallel to the thickness direction X of the sheet 32, but theoretically about half (strictly speaking, in the thickness direction of the sheet 32, To ±
It can be said that almost half of them fall within the range of 45). (See FIG. 4A) The friction material 5 is punched out from the sheet 32 thus created as shown in FIG. (See Fig. 4 (b))

As a result, approximately half of the carbon fibers 39 arranged in the direction substantially perpendicular to the friction surface of the friction material 5 (parallel to the surface of the sheet 32) finally exist in the friction material 5 (the orientation is Have). In reality, some carbon fibers may have an angle on a surface perpendicular to the compression direction of the press, but the carbon fibers appear to stand up against the friction surface of the friction material 5. About 70 to 80% can be seen.

Example 2 In Example 2, only the average length of carbon fiber was 20 μm and 50
When the friction material 5 was made under the same conditions as in Example 1 while supporting it with μm, 180 μm, 350 μm, and 450 μm, and similarly evaluated with the vibration wave motor, the relationship between the length of the carbon fiber and the friction amount is shown in FIG. It was

When the carbon fiber length is 450 μm, the friction material has many voids in the fluororesin portion. This is because the carbon fiber was long and the fluororesin powder and the carbon fiber were not mixed well, and the carbon fiber could not be uniformly dispersed, and the specific gravity was 1.6. However, the theoretical specific gravity of the mixture of fluororesin powder and carbon fiber is 2.07 (described later).

On the other hand, the carbon fiber has a length of 350 μm and a length of 1.
At 80 μm, the wear of the friction material 5 was slightly inferior to that of Example 1, but was almost good and the specific gravity was 1.9.

From these results, it is not appropriate to make the carbon fibers too long in order to improve wear resistance. On the other hand, although the specific gravity is 2.0, carbon fibers having a length of 20 μm are likely to come off, resulting in a large amount of wear, and carbon fibers having a specific gravity of 2.0 but having a length of 50 μm are also likely to come off. The amount of wear increased a little. From the above results, it is preferable that the appropriate length is about 50 μm to 350 μm.

Although the thickness of the fiber is 13 μm in this example, it was confirmed that this result is not different even if the thickness is several μm to 20 μm.

Example 3 A friction material was made from a sheet material and evaluated in the same manner as in Example 1, except that only the pressure after filling the mold was changed and the other conditions were the same. The specific gravity of the fluororesin composite material can be changed by changing the pressure during compression molding, and FIG. 6 shows the relationship between the specific gravity and the abrasion amount of the friction material by evaluation.

As can be seen from this relationship, if it is 80% or less with respect to the theoretical specific gravity, the amount of wear is large and it seems that it is not suitable as a friction material. In addition, from this result, not only the orientation of the carbon fiber described above but also the wear resistance of the friction material is related to the specific gravity, and it depends on how closely the carbon fiber is surrounded by the fluororesin and the carbon fiber is difficult to come off. It seems to indicate.

The theoretical specific gravity was calculated as follows. The true specific gravity of the fluororesin powder (2.18) and the true specific gravity of the carbon fiber (1.64), and the mixing ratio is 80:20, so the theoretical specific gravity = (2.18 × 80 + 1.64 × 20) /
It becomes 100 = 2.07 [g / cm ³ ].

In the above examples, carbon fiber was used as the fibrous material, but other fibrous materials, such as Kevlar fiber for polymer material and alumina fiber for inorganic material, have similar effects on orientation. However, carbon fiber is the most suitable for the vibration wave motor because it has the least amount of wear and the stable friction coefficient.

Further, in the embodiment, the fluororesin composite material in which the fluororesin powder and the carbon fiber are mixed is described, but other powder may be added. For example, polyimide powder with high heat resistance, which is easily available and can be expected to improve wear resistance, and molybdenum sulfide powder, which has lubricity even in vacuum or at high temperature, can improve the properties as a wear material. Is.

In the present invention, the mixing ratio of the fluororesin powder and the fibrous material is 60 to 9 for the fluororesin powder.
It is 8% by weight, preferably 70 to 95% by weight, and the fibrous material is preferably in the range of 2 to 40% by weight, preferably 5 to 30% by weight. In this range, the amount of wear was 20 μm or less under the evaluation conditions of Example 1, which is preferable.

Further, the present invention can be used in various equipments as shown in FIG. 7 using the vibration wave motor provided with the above-mentioned friction material as a drive source.

Further, FIG. 7 is a schematic view of an apparatus using the vibration wave motor shown in FIG. 1 as a drive source. 23 is a large gear 23
A gear having a and a small gear 23b, 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 the 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, the rotation of the gear 23 is detected by the photocoupler 26, and the rotation and stop of the motor are controlled for autofocus, for example.

Specific examples of the equipment include optical equipment such as cameras, office equipment such as printers and copying machines, and automobile-related equipment such as power windows and active suspensions.

[0055]

As described above, according to the present invention, a specific gravity of 80% or more of the theoretical specific gravity of a fluororesin as a main component and a fibrous material is compression-molded into a molded body and fired. By using a fluororesin composite material with a cylindrical shape or a columnar outer peripheral part as a sheet by cutting it and using it as a friction material for a vibration wave motor, a friction material with excellent wear resistance can be produced very inexpensively and in large quantities. Can be obtained.

Further, according to the present invention, various fibrous materials and other additives can be selected quite freely, and a friction material suitable for a vibration wave motor used for various purposes can be easily prepared. It is a manufacturing method that is useful for practical application and application development of vibration wave motors.

[0057]

[Brief description of drawings]

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

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

FIG. 3 is an explanatory view showing a method of compression molding a fluororesin and a fibrous material in the present invention.

FIG. 4 is an explanatory diagram showing the principle of the orientation of the fibrous material in the present invention.

FIG. 5 is a diagram showing the relationship between the length and the amount of wear of carbon fibers according to the present invention.

FIG. 6 is a diagram showing a relationship between specific gravity and wear amount according to the present invention.

FIG. 7 is a schematic view showing a device as an application example of the vibration wave motor of the present invention.

[Explanation of symbols]

1 vibrating body 3 Metal elastic body 5 Friction material 30 fired body 31 cutting blade 32 sheets 33 Mixed powder 34 Cylindrical mold 35a, 35b punch 36 core 37 molded body 38 sides 39 carbon fiber

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-9-327183 (JP, A) JP-A 5-146176 (JP, A) JP-A 8-23687 (JP, A) JP-A 62- 209236 (JP, A) Actual development Sho 62-195391 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02N 2/00 B29D 31/00

Claims (5)

(57) [Claims] 1. A friction material used for a frictional contact surface between a vibrating body that forms vibrations of a vibration wave motor and a contact body that is pressed against the vibrating body and that moves relative to the vibrating body by the vibration. In the method, a fluororesin composite material is produced by firing a molded body containing a fluororesin as a main component obtained by compression molding a fluororesin powder and a fibrous material, and then cutting the fluororesin composite material by cutting. A method for manufacturing a friction material, characterized in that the friction material is formed by cutting out from the outer peripheral portion into a sheet shape. 2. The theoretical specific gravity of the fluororesin composite material
The compression molding should be performed so that the weight becomes 80% or more.
The method for manufacturing a friction material according to claim 1, wherein the method is for manufacturing a friction material. 3. The method for producing a friction material according to claim 1, wherein the fluororesin composite material has a cylindrical shape or a columnar shape, and an outer peripheral portion of the fluororesin composite material is cut into a sheet shape by cutting. Wherein the material of said fibrous length 50μm~
Claim, characterized in that a 350μm carbon fibers 1
4. The method for manufacturing the friction material according to any one of items 1 to 3 . 5. A friction member formed by shaving into a sheet shape.
The fibrous material contained in the friction material is
5. Any one of claims 1 to 4 in which
The method for producing the friction material according to the above paragraph.