JPH05247233A - Friction material - Google Patents

Abstract

PURPOSE:To provide a friction material excellent in wear resistance. CONSTITUTION:The title material comprises a base fiber and a binder, the base fiber being a fiber bundle partially comprising carbon fibers with an elastic modulus of 6,000kgf/mm<2> or less or a string formed by combining a fiber bundle of carbon fibers with an elastic modulus of 6,000kgf/mm<2> or less and that of carbon fibers with a tensile strength of 200kgf/mm<2> or more. The string, impregnated with a phenolic resin or rubber binder, is wound. The resultant string is rolled in the spiral form and molded by heating into a clutch facing. The friction material contributes to weight reduction, and improvements in wear resistance and burst strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material used for clutch facings, brake pads and the like.

[0002]

2. Description of the Related Art In automobiles and the like, as a component of a clutch disc for connecting and disconnecting power between an engine and a transmission,
Clutch facings are used. For this cladding facing, a base fiber made of inorganic fibers such as asbestos, glass fibers, carbon fibers or a composite of heat resistant organic fibers such as polyamide fibers with the inorganic fibers, and a thermosetting resin serving as a binder. There is known a resin mold type in which a rubber material, a vulcanizing agent, a friction modifier, etc. are mixed, filled in a molding die, and heated and pressed to form. Further, the above-mentioned base material fibers made into a felt shape, a mat shape, or a woven cloth shape are impregnated with a binder mixed solution of a thermosetting resin, a rubber material, a vulcanizing agent, a friction modifier, etc. There is also known a woven system that is formed by cutting into pieces, laminating them into a desired circular shape, and then applying heat and pressure. In addition, a semi-mold type one in which the above-mentioned base fiber is formed into a string shape, impregnated with a mixed solution containing a binder, rolled up in a spiral shape or a thermoid shape, formed into a desired shape, and heated and pressed. Is also known.

[0003]

However, since the adverse effects of asbestos on the human body have become known, the use of asbestos has been restricted and glass fibers and carbon fibers have become the mainstream as the base fibers. There is. Further, in recent years, with the increase in output of automobiles, performances such as weight reduction and improvement of friction and wear characteristics are required for clutch facings.

Here, in order to reduce the weight of the clutch facing, it is advantageous to use carbon fiber having a smaller specific gravity than glass fiber as the base fiber. Since this carbon fiber has a self-lubricating action, it is also advantageous for improving wear characteristics. However, conventional clutch facings using carbon fibers as the base fibers have not been able to be said to sufficiently satisfy the required friction and wear characteristics.
In particular, there is a problem that durability is poor due to lack of wear resistance and replacement frequency is high. Further, when carbon fiber is used as the base fiber, there are problems such as variations in friction coefficient and reduction in breaking strength (burst strength).

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a friction material excellent in wear resistance and improved in burst strength by using carbon fiber which is advantageous for weight reduction. ..

[0006]

The friction material of the present invention has a modulus of elasticity of 6000 kgf / m as at least a part of the base fiber.
It is characterized by using carbon fibers of m ² or less. Further, the friction material of the present invention uses a string obtained by twisting and twisting at least a part of the base fiber, which is a carbon fiber having an elastic modulus of 6000 kgf / mm ² or less and a carbon fiber having a tensile strength of 200 kgf / mm ² or more. Characterize.

[0007]

In the friction material of the present invention, carbon fiber having an elastic modulus of 6000 kgf / mm ² or less is used at least in part as the base fiber, and the abrasion resistance is improved. It is considered that this is because when the elastic modulus of the carbon fiber is small, the elongation becomes large as shown in FIG. That is, when the elongation is high, the carbon fibers themselves are less likely to crack, and the carbon fibers are prevented from being detached from the friction surface. As a result, it is considered that the wear resistance of the clutch facing is improved. The self-lubricating action of the carbon fiber itself also contributes to the improvement of wear resistance. Furthermore, if the elastic modulus of the carbon fiber is low, the graphitization rate of the carbon fiber is also low, which is also expected to contribute to the improvement of wear resistance.

Furthermore, the elastic modulus of the base fiber is 6000k.
Carbon fiber with gf / mm ² or less and tensile strength of 200 kg
The strength of the base fiber is increased by using a string obtained by twisting and twisting f / mm ² or more carbon fiber. As a result, the clutch facing can increase the burst strength.
That is, a carbon fiber having an elastic modulus of 6000 kgf / mm ² or less is usually composed of spun yarn of short fibers and has a tensile strength of 10 or less.
It is often as low as 0 kgf / mm ² or less. The spun yarn composed of short fibers has a lower bulk specific gravity and more voids than the yarn composed of long fibers. Therefore, the binder is easily impregnated. Therefore, variations in the density of the friction material are reduced, and the friction coefficient can be stabilized. However, the tensile strength as a string is low because the short fibers are easily separated. Therefore, the burst strength of the clutch facing decreases. On the other hand, when long carbon fibers having a tensile strength of 200 kgf / mm ² or more are bundled to form a twisted string, the tensile strength is increased, but since the long fibers are twisted and densified, the impregnation property of the binder is insufficient. The friction coefficient is likely to be uneven.

Therefore, the elastic modulus is 6000 kgf / mm ²
The following carbon fibers and carbon fibers having a tensile strength of 200 kgf / mm ² or more are combined and twisted to improve the impregnation property of the binder and prevent uneven friction coefficient, and the tensile strength of the fiber base material itself. Also, the burst strength of the clutch facing can be improved. Further, since the carbon fiber has a smaller specific gravity than other fibers such as glass fiber, it can contribute to the weight reduction of the friction material.

[0010]

EXAMPLES The present invention will be specifically described below with reference to examples. (Example 1) As the base fiber, the tensile strength is 92 kgf.
/ Mm ² , 30 vol% of carbon fiber (diameter 13 μm, length 50 mm) having an elastic modulus of 6000 kgf / mm ² , glass fiber (diameter 6 μm, continuous long fiber) 35 vol%, and aromatic polyamide fiber (“Kevlar # 29”) Made by DuPont,
A fiber bundle obtained by bundling 35 vol% (diameter 13 μm, length 2 to 4 mm) was used. The apparent thickness of this fiber bundle is φ
It is 2.3 to 3.3 mm. The fiber bundle was twisted at an angle of 20 degrees. Three sets of this twisted fiber bundle and one brass wire were twisted together to form a string.

This string was impregnated with a phenol resin as a binder, SBR as a rubber binder, carbon black and BaSO ₄ , and then dried at 100 ° C. for 10 minutes. Then, it was spirally wound to form a perforated disc-shaped wound product. The above-mentioned rolled product is 160 ° C, 100
It was placed in a thermoforming mold set to kg / cm ² , held for 5 minutes, subjected to thermoforming, and then ground to produce the clutch facing of Example 1.

The clutch facing of this embodiment has a base fiber of 30 vol% and a phenol resin of 20 v.
ol%, SBR: 25 vol%, carbon black: 1
_{9vol%, BaSO 4: 4vol%} , brass line: 2vo
The composition is 1%. (Example 2) The same carbon fiber, glass fiber, and aromatic polyamide fiber as in Example 1 were used, and the respective compounding ratios were 50 vol% of carbon fiber and 25 vol of glass fiber.
%, And an aromatic polyamide fiber 25 vol%. A clutch facing was produced in the same manner as in Example 1 except that the fiber bundle having the different composition was used as the fiber. (Example 3) The same carbon fiber, glass fiber, and aromatic polyamide fiber as in Example 1 were used, and a fiber bundle composed of 70 vol% of carbon fiber, 15 vol% of glass fiber, and 15 vol% of aromatic polyamide fiber was prepared, respectively. .. A clutch facing was produced in the same manner as in Example 1 except that the fiber bundle having the different composition was used as the fiber. (Example 4) 100 vo of carbon fiber similar to that of Example 1 above
A clutch facing was produced in the same manner as in Example 1 except that a fiber bundle consisting of 1% was used as the fiber base material. (Comparative Example 1) 100 vol of carbon fiber having a tensile strength of 200 kgf / mm ² and an elastic modulus of 15000 kgf / mm ^2.
%, Except that a fiber bundle consisting of
A clutch facing was manufactured in the same manner as in Example 1 above. (Comparative Example 2) The same glass fiber as in Example 1 and the aromatic polyamide fiber were used, and the glass fiber 50v was used.
A clutch facing was produced in the same manner as in Example 1 except that a fiber bundle composed of ol% and 50 vol% of aromatic polyamide fiber was used as the fiber base material.

[0013]

[Table 1] (Evaluation) The clutch facings of Examples 1 to 4 and Comparative Examples 1 and 2 were mounted on a full-size dynamo tester, respectively, and the rotation speed was 4000 rpm and the inertia was 0.
08kgfms ² , test temperature: 200 ° C, number of engagements: 5
The volume wear rate was measured by operating under the condition of 00 times. The result is shown in FIG.

From the results shown in FIG. 1, the clutch facings of Examples 1 to 4 including a fiber bundle of carbon fibers having an elastic modulus of 6000 kgf / mm ² as the base fibers were compared with Comparative Examples 1 and 2. The wear rate is low and the wear resistance is excellent. Also, comparing the clutch facings of Examples 1 to 4, the elastic modulus of the base fiber is 6000 kgf / mm.
^It can be seen that the wear rate decreases as the number of carbon fiber bundles of ² increases.

Further, the elastic modulus is 6000 kgf / mm ²
Of Example 4 using the fiber bundle of carbon fiber of
Comparing with Comparative Example 1 using a fiber bundle of carbon fiber of 00 kgf / mm ² , the elastic modulus of carbon fiber is 6000 kgf.
It can be seen that the wear rate is significantly reduced if the value is less than / mm ² . It is considered that this is because when the elastic modulus of the carbon fiber is small, the elongation rate is large, and thus the carbon fiber is less likely to be cracked during the manufacturing process of twisting the fiber bundle of the carbon fiber or during the friction.

The above-mentioned Examples 1 to 4 and Comparative Examples 1 and 2
The specific gravity and burst strength of each of the clutch facings were measured. The results are shown in Table 1. From the results shown in Table 1, the clutch facings of Examples 1 to 4 and Comparative Example 1 including a fiber bundle of carbon fibers as the base fiber,
It can be seen that the specific gravity is smaller than that of the clutch facing of Comparative Example 2 in which the carbon fiber bundle is not included as the base fiber, and the larger the fiber bundle of the carbon fiber is included as the base fiber, the smaller the specific gravity is. Also, comparing the burst strength, the base fiber this time is a combination of high strength fiber bundles,
Although there is no big difference in burst strength, it can be seen that the smaller the specific gravity of the product, the more advantageous the result.

In Examples 1 to 4, the base fiber and
And has a tensile strength of 92 kgf / mm ², Modulus of elasticity is 600
0 kgf / mm²I used a carbon fiber bundle of
Strength is 5 to 100 kgf / mm², The elastic modulus is 300 ~
6000 kgf / mm²Suitable use of carbon fiber bundles
Can be The tensile strength of this carbon fiber is
Can be determined in consideration of the required burst strength
It The elastic modulus of carbon fiber depends on the fiber breakage during string processing.
The elastic modulus is small if only this point is taken into consideration.
Good enough. Also, the base fiber should be used in consideration of product strength.
In this case, it is preferable to use only long fibers as in the above example.
However, using a non-woven fabric consisting of short fibers together with long fibers
You can also do it. (Example 5) As a base fiber, the tensile strength is 360 kgf.
/ Mm², The elastic modulus is 23500 kg / mm², Elongation 1.
5% long carbon fiber (Torayca T-300 Toray Industries, Inc.
Made of 1 fiber bundle (apparent thickness of this fiber bundle is 1-2
mm) and tensile strength 80 kgf / mm², Elastic modulus
Is 4000 kgf / mm², Short carbon fiber with 2% elongation
(Donna S210 Osaka Gas Co., Ltd .; length 35 mm)
4 spun yarns (apparent thickness 1-2 mm) are twisted together
I made a string. In addition, this string is 30% by weight of carbon long fiber,
It is composed of 70% by weight of carbon short fibers. This carbon long fiber
A structural model of a string formed from fiber bundles of fibrous and short carbon fibers.
The formula is shown in FIG. Tensile strength 360kgf / mm²Charcoal
Fiber bundle A of plain filaments and elastic modulus of 4000 kgf / mm
²Fiber bundle B of spun yarn of carbon short fibers of
The string C is formed. The apparent thickness of this string
Is 2.3 mm to 3.3 mm.

The number of twists of spun yarns and cords of short fibers is 10
It was 0 times / m. This string was impregnated with a phenol resin and a binder containing SBR and carbon black as a rubber binder, and then dried at 100 ° C. for 10 minutes. Then, the string impregnated with the binder was wound in a spiral shape to form a perforated disk-shaped wound product.

The rolled product is placed in a thermoforming mold at a pressure of 100.
After holding at 160 ° C. for 5 minutes at a pressure of kgf / cm ² for molding, it was ground into a predetermined shape to produce a clutch facing. Note that the clutch facing of the present embodiment has 35% by volume of the base fiber, 20% by volume of the phenol resin, and SB
The composition is such that R is 25% by volume and carbon black is 20% by volume. (Example 6) A clutch facing was produced in the same manner as in Example 5 except that two bundles of long carbon fibers similar to those in the above-mentioned Example 5 and four spun yarns of short carbon fibers were twisted together to form a string. did. This string is composed of 40% by weight of carbon long fibers and 60% by weight of carbon short fibers. (Example 7) A clutch facing was produced in the same manner as in Example 5, except that 3 bundles of long carbon fibers similar to those of the above-mentioned Example 5 and 4 spun yarns of short carbon fibers were twisted together to form a string. .. The string is composed of 50% by weight of carbon long fiber and 50% by weight of carbon short fiber. (Example 8) Tensile strength of 90 kgf / mm ² (pitch type, manufactured by NG04C Nippon Steel Corporation), elastic modulus of 40
A clutch facing was produced in the same manner as in Example 5, except that only 4 spun yarns of carbon short fiber having a elongation of 1.8% at 00 kgf / mm ² were bundled and used as a string.

[0020]

[Table 2] Except Example 9 tensile strength of 90 kgf / mm ^2, an elastic modulus was used as the base fiber as a link by twisting the fiber bundle 4 bundle of carbon filaments of 5000 kgf / mm ^2, in the same manner as in Example 5 To produce a clutch facing. (Comparative Example 3) A fiber bundle of glass fibers (long fibers) and a fiber bundle of aromatic polyamide fibers were each 50% by volume (1 for each).
A clutch facing was produced in the same manner as in Example 5 except that a string made of a bundle of bundles was used as the base fiber. (Evaluation) The clutch facings of Examples 5, 6, 7, 8, 9 and Comparative Example 3 were mounted on a full size dynamo tester, respectively, and the rotation speed was 4000 rpm and the inertia was 0.
08kgfms ² , test temperature: 200 ° C, number of engagements: 5
The volume wear rate was measured by operating under the condition of 00 times. The result is shown in FIG.

As another test, the breaking strength (maximum breaking rotation speed) of each clutch facing at 200 ° C. was measured. Other specific gravity was also measured. The results are shown in Table 2.
From the burst strength measurement shown in Table 2, the tensile strength was 200.
Carbon long fiber of kgf / mm ² or more and elastic modulus of 6000
The burst strength is improved in Examples 5, 6, and 7 in which the base fiber composed of a string in which short carbon fibers of kgf / mm ² or less are combined is used. As the number of high-strength carbon filaments increases, the density of the string increases, and the specific gravity increases accordingly.

In Example 9, long fibers (tensile strength 90 kgf /
Only 4 mm ² ) and 4 bundles were combined to form a string and used as the base fiber, but the burst strength was quite high, but because short fibers were not used, the impregnation of the binder was poor and the density was uneven. The specific gravity was as low as 1.38. Further, in the case of the base fiber made of the string obtained by combining only four spun yarns of the short fiber of Example 8, the short fibers are easily separated from each other, and the burst strength is lower than that in the case of the combination with the long fiber. However, the wear resistance is almost at the same level as in Examples 5, 6, and 7 as shown in FIG.

The comparative example 3 using a base fiber made of a string of fiber bundles other than carbon fiber has a low specific gravity, which is 1.68, but a low burst strength. As shown in FIG. 4, in Examples 5 to 9, the wear rate is low and is a good value. In addition, the number of long carbon fibers combined did not affect the wear rate. It is presumed that when short fibers having a low elastic modulus were used, the carbon fibers worked as a lubricant and the wear rate became low as shown in Example 9. When the string made of the fiber bundle of the glass fiber and the aromatic polyamide fiber of Comparative Example 3 is used as the base fiber, the burst strength is low and the specific gravity is high, and the wear rate is significantly high as shown in FIG.

The carbon fiber used for the spun yarn has a short fiber length of 1 to 50 mm, but some length of the fiber is unavoidable in the spinning process and the twisting process. It is not preferable because the twisted cord is densified and the impregnating property of the binder is lowered. In addition, long fibers having a filament number in the range of 1 to 12 k are usually used.

The string can be twisted with other organic, inorganic or metal fibers to change the frictional characteristics.

[0026]

[Table 3]

The carbon fiber having a tensile strength of 200 kgf / mm ² or more has an elastic modulus of 6000 as shown in Table 3.
The thermal conductivity is 10 compared to carbon fiber of less than kgf / mm ^2.
More than twice as expensive. Further, the above carbon fiber has a value 10 times or more as high as the thermal conductivity of the conventionally used glass fiber, so that there is no problem in terms of heat conduction, and in comparison with the base material made of glass fiber or brass wire. High heat conductivity is possible, and heat resistance is improved by the decrease in the friction surface temperature.

[0028]

As described in detail above, the friction material of the present invention is
Carbon fiber having an elastic modulus of 6000 kgf / mm ² or less is used as at least a part of the base fiber, which contributes to weight reduction of the friction material and improvement of wear resistance.
Further, since the carbon fiber having a high elongation rate is used, the fiber is hard to be broken at the time of string processing, and when manufacturing the clutch facing, the wound product can be formed with high productivity.

In the case of a friction material involving high speed rotation such as clutch facing, it is necessary to increase the breaking strength at high speed rotation. Therefore, the elastic modulus is 6000 kgf / m
A fiber bundle of carbon fibers of m ² or less and a tensile strength of 200 kg
The burst strength of the friction material is further improved by forming a cord in which a fiber bundle of carbon fibers of f / mm ² or more is combined and twisted. Furthermore, the bulk specific gravity of the base fiber becomes low due to the twisting of the spun yarn of the carbon fiber and the fiber bundle of the long fiber, the bulk density of the base fiber increases, the voids increase, and the binder is sufficiently impregnated into the fiber base material and the density is Uniformity leads to stabilization of the friction coefficient.

Since the carbon fiber has a lower specific gravity than other fibers such as glass fiber which constitutes the conventional base fiber, the strength can be secured by plying the carbon fiber with the other fibers such as brass wire. Since it is not necessary to use the above fibers, it is possible to contribute to the weight reduction of the friction material.

[Brief description of drawings]

FIG. 1 is a bar graph showing the wear resistance evaluation results of clutch facings according to Examples and Comparative Examples.

FIG. 2 is a diagram showing a relationship between elastic modulus and elongation of carbon fibers.

FIG. 3 is a schematic diagram illustrating a configuration of a base fiber of Example 5.

FIG. 4 is a bar graph showing the results of evaluation of wear resistance of clutch facings according to Examples 5-9 and Comparative Example 3.

[Explanation of symbols]

A carbon short fiber spun yarn, B carbon long fiber, C twisted string,

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Shimoda 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (2)

[Claims] 1. An elastic modulus as at least a part of a base fiber
6000 kgf / mm ²That the following carbon fibers were used
Characteristic friction material. 2. The elastic modulus as at least a part of the base fiber
6000 kgf / mm ²The following carbon fibers and tensile strength 2
00 kgf / mm²A twisted string of the above carbon fibers
A friction material characterized by being used.