JP3080273B2 - Wet friction material and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet friction material used for friction braking in oil, such as a clutch facing and a brake pad of an automatic transmission, and a method of manufacturing the same .

[0002]

2. Description of the Related Art A friction plate of a multi-plate clutch used in an automatic transmission of an automobile has a structure in which a hollow disk-shaped paper facing made of a paper base material is bonded to both sides of a cored bar. Then, rotation of the engine is transmitted by friction with a partner material in the oil.

As a method for producing this paper facing, as disclosed in Japanese Patent Application Laid-Open No. 62-266238, a papermaking stock solution mainly containing a fiber base material such as pulp and a filler such as cashew dust is used. Paper is formed using a round-mesh type papermaking machine or the like to form a paper base material, which is impregnated with a binder such as a phenol resin, and then heated and pressed to form. The paper facing is manufactured by cutting this into a predetermined shape.

[0004]

However, in a wet friction material manufactured by the above-described conventional manufacturing method, the friction coefficient after history becomes higher than the initial friction coefficient, and the friction coefficient changes with time. Became clear. When the friction coefficient changes over time as described above, for example, in the case of clutch facing of an automatic transmission, the shift feeling may deteriorate over time.

The present invention has been made in view of such circumstances, and has as its object to stabilize the friction coefficient over time.

[0006]

The inventor of the present application has presumed that the cause of the above-mentioned change in friction coefficient with time is that the contact area between the friction material and the mating material changes with time. When the surface of the friction material and the surface of the mating material are compared, the surface roughness of the conventional friction material is initially about one digit larger than that of the mating material, and the surface roughness becomes smaller due to the history and becomes closer to the mating material It became clear.

As a result of intensive studies, they have found that the initial and post-history friction coefficients are stabilized by bringing the initial surface roughness close to the mating material, and completed the present invention. That is, the wet friction of the present invention that solves the above problems
The material is mainly a paper-based material consisting of a fiber base material and a filler.
And a wet friction material comprising a binder impregnated in a paper base material
The fine surface of the paper
The diameter of the fine fibers that make up the fiber layer and form the fine fiber layer
Is approximately the same as the surface roughness (Rz value) of the mating material.
Sign. In addition, the method for producing a wet friction material of the present invention for producing the above-mentioned wet friction material includes a step of forming a paper base material by forming paper from a stock solution mainly containing a fiber base material and a filler; The method is characterized in that a step of coating the surface of the paper-based substrate with fibers to obtain a fiber-coated paper base, and a step of impregnating the fiber-coated paper base with a binder and subjecting the fiber-coated paper base to heat and pressure molding are sequentially performed.

[0008]

According to the method for producing a wet friction material of the present invention, first, a paper base material is formed in the same manner as in the prior art, and then fine fibers having a diameter of 2 μm or less are coated on the surface of the paper base material and impregnated with a binder. And press-mold under heat. In the friction material obtained by the conventional manufacturing method, the fiber substrate exposed on the friction surface has a diameter of 10 to 60 μm.
m, and the initial surface roughness necessarily has such a value. However, the surface roughness of the steel plate as the mating material is about Rz = 0.2 to 2 μm. This is because when the surface roughness is smaller than 0.2 μm, seizure is likely to occur, and when the surface roughness is larger than 2 μm, wear tends to occur.

Therefore, the surface roughness of the friction material is largely different from that of the mating material in the initial stage, so that the contact area is initially small and the friction coefficient is low. On the other hand, when the surface roughness decreases due to wear of the friction material over time, the contact area increases and the friction coefficient increases. Therefore, in the production method of the present invention, the surface of the paper base material is coated with fine fibers having a diameter of 2 μm or less. As a result, the fine fibers cover the large irregularities of the fiber base material, and the initial surface roughness of the obtained friction material can be 2 μm or less. Therefore, the surface roughness can be made close to the surface roughness of the counterpart material, and the initial friction coefficient increases. When the diameter of the fine fibers is larger than 2 μm, the effect of improving the initial friction coefficient is small, and the friction coefficient changes with time.

[0010] The length of the fine fibers is not particularly limited, but is preferably longer than the diameter of the fiber base material. By doing so, it efficiently covers large irregularities of the fiber base material,
The surface roughness can be reduced in a small amount and in a short time.
Furthermore, if carbon fibers are used as fine fibers, high lubricity and high thermal conductivity can be imparted, and the occurrence of stick slip can be suppressed, and burning can be prevented. When organic fibers such as linter fiber, wood fiber, acrylic fiber, and aramid fiber are used, the surface smoothness is further improved, and the occurrence of stick-slip can be further suppressed.

[0011]

The present invention will be specifically described below with reference to examples. (Example) Cellulose fiber (diameter 10
-60 μm) and aramid fiber (diameter: 12 μm), an inorganic filler (diatomaceous earth) and an organic filler (cashew dust) were added, and a papermaking stock solution was prepared with water.

In addition, as the base fiber, metal fibers such as linter fiber, rayon, acrylic fiber, wood pulp organic fiber, brass wire and the like, and inorganic fibers such as rock wool, carbon fiber, glass fiber, ceramic fiber and the like can be used. Can be used. In addition, examples of the filler include powder fillers such as graphite, barium sulfate, calcium carbonate, and clay.

Using the above stock solution for papermaking, papermaking was performed by a papermaking machine to form a paper base material having a predetermined thickness. While the paper base was still in a wet state, fine fibers composed of aramid fibers sieved to a diameter of 1 μm or less were adhered to the friction surface and coated to obtain a fiber-coated paper base. The amount of the attached fine fibers is 1 part per 100 parts of the paper base material.

After the fiber-coated paper substrate was dried by hot pressing, it was impregnated with a phenol resin as a binder and thermoformed. It was cut into a predetermined shape to obtain a friction material of this example. In addition, a thermosetting resin such as a melamine resin and an epoxy resin can be used as the binder. Comparative Example A friction material of a comparative example was formed in the same manner as in the example except that the step of coating the fine fibers was not performed. (Test) For the friction materials of Examples and Comparative Examples, the surface roughness was measured and a friction test was performed. The surface roughness was measured by a surface roughness meter, and the friction test was performed using S35 as a mating material.
A CM barrel-treated product was selected, and a SAE # 2 test was performed under the conditions shown in Table 1, and a friction coefficient (μ _d ) was measured at each joining frequency.
The results of measuring the coefficient of friction are shown graphically in FIG.

[0015]

[Table 1] (Evaluation) FIG. 1 shows that the friction material of the comparative example has a joining frequency of 20.
While the friction coefficient greatly changes from low to high at the time of the initial joining, the friction material of the example shows an almost constant friction coefficient from the beginning of joining to after the history.

The difference between the friction material of the embodiment and that of the comparative example is only the presence or absence of the coating of the fine fibers. Therefore, the coating of the fine fibers reduces the surface roughness, thereby increasing the contact area, and It is apparent that the coefficient of friction was improved and the change with time in the coefficient of friction was eliminated.

[0017]

According to the wet friction material of the present invention,
The friction coefficient is stable from the beginning of joining to after the history . And book
According to the manufacturing method of the present invention, such a wet friction material can be easily and stably manufactured.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the number of splices and the coefficient of friction.

Claims (2)

(57) [Claims] 1. A paper mainly comprising a fiber base material and a filler.
Comprising a paper base material and a binder impregnated in the paper base material.
A friction material, A fine fiber layer is formed on the surface of the paper base material that is in sliding contact with the mating material.
The diameter of the fine fibers constituting the fine fiber layer
The feature is that it is almost the same as the surface roughness (Rz value) of hand material
Wet friction material. 2. A step of forming a paper substrate by making a papermaking stock solution mainly containing a fiber substrate and a filler; and covering the surface of the paper substrate with fine fibers having a diameter of 2 μm or less. A method for producing a wet friction material, comprising sequentially performing a step of forming a paper base material, and a step of impregnating the fiber-coated paper base material with a binder and performing heating and pressure molding.