JPH06185556A - Manufacture of wet type friction material - Google Patents

Abstract

PURPOSE:To perform easy and reliable manufacture of a wet type friction material prevented from the occurrence of a judder at the initial stage of a use. CONSTITUTION:0.1-2wt.% PTFE powder with a grain size of 10mum or less is adhered on the surface of a paper base material and thereafter impregnated with a binder for thermoforming. Since a friction surface is fixed in a state to be smoothed by means of PTFE having high lubricity, a stable friction factor is provided from an initial stage and a judder is also prevented from occurring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a wet friction material used for clutch facing of an automatic transmission of an automobile.

[0002]

2. Description of the Related Art The clutch facing of an automatic transmission is
It is called a wet friction material because it is used in oil. This wet friction material includes fiber base materials selected from various organic and inorganic fibers such as pulp, aromatic polyamide fibers and glass fibers, calcium carbonate, silica, barium sulfate,
It is made of a mixed material in which an inorganic filler such as diatomaceous earth is mixed with a friction modifier such as cashew dust or graphite.

To produce a wet friction material from this mixed material, for example, as disclosed in Japanese Unexamined Patent Publication No. 62-266238, first, the mixed material is dispersed in water, and then a round-net papermaking machine or a Fourdrinier machine is used. A paper-making base material is obtained by making paper with a type paper making machine or the like. Phenolic resin, melamine resin,
A friction material having a predetermined thickness is manufactured by impregnating a thermosetting resin such as an epoxy resin and compressing while heating.

In addition, the improvement of fuel efficiency of automobiles has become an important issue in recent years from the viewpoint of environmental problems and effective utilization of resources. Therefore, weight reduction is also considered for automatic transmissions, and it has been found that it is effective to adopt a lockup system that transmits power directly or slightly by friction torque of wet friction material without passing through a torque converter. ing.

[0005]

However, if the conventional wet friction material manufactured as described above is used as it is in the lockup system, a vibration phenomenon called judder tends to occur at the initial stage of use. It is considered that this is because the so-called "hit" between the friction material and the mating material is bad at the beginning of use. It is considered that, as the friction material is used, smoothing progresses following the shape of the mating material and the "hit" is stabilized, so that judder is less likely to occur. Further, at the initial stage of use, the "hit" may be poor, which may cause a shift delay due to insufficient friction torque, or the shift feeling may change with use.

In order to deal with this problem, it is effective to perform a step of rubbing the surface of the wet friction material in the assembly line to give a so-called "hit". However, in the lapping process, there is a problem in terms of man-hours that the tact time is long, and defective products such as a burn may occur during the lapping, resulting in a large loss. The present invention has been made in view of such circumstances, and an object of the present invention is to have a smooth friction surface from the initial stage of use, and to prevent fluctuations in the judder and the shift feeling due to stable and smooth friction.

[0007]

In the method for producing a wet friction material of the present invention which solves the above problems, a paper material base material is formed by papermaking from a mixed material containing a base fiber, an inorganic filler and a friction modifier. And a step of adhering polytetrafluoroethylene (PTFE) powder having a particle size of 10 μm or less to the surface of the paper base material in an amount of 0.1 to 2% by weight with respect to the paper base.
It is characterized in that the step of impregnating the paper base material to which the FE powder is adhered with the binder resin and heat-molding is sequentially performed.

If the particle size of the PTFE powder is larger than 10 μm, the smoothness is adversely affected, so the particle size is set to 10 μm or less. If the particle size of the PTFE powder is smaller than 1 μm, it will be difficult for the smoothing effect to be obtained because it will not easily remain on the surface of the PTFE powder as it will enter or flow down inside the paper substrate during the step of adhering to the paper substrate. It is desirable to do. Further, if the amount of the PTFE powder adhered is less than 0.1% by weight, the smoothing effect cannot be obtained, and if it exceeds 2% by weight, the friction coefficient is significantly lowered, which is not preferable.

[0009]

In the wet friction material manufacturing method of the present invention, the PTFE powder is attached to the surface of the paper base material. At this time, the PTFE powder is preferentially filled in the recesses on the surface of the paper base material, and the surface becomes smooth. Then, in the impregnation step of the binding resin, the binding resin is impregnated between the PTFE powders, and the PTFE powder is integrally bound with the paper base material in the heat molding step, so that the smooth state is fixed.

When the obtained wet friction material is used,
Since the friction surface is in a smooth state from the beginning of use, the contact area with the mating material is large from the beginning and the "hit" is good. Also, due to the high lubricating effect of PTFE, it is well compatible with the mating material. Therefore, the occurrence of judder is prevented in the initial stage of use, and a stable shift feeling is obtained.

[0011]

EXAMPLES The present invention will be specifically described below with reference to examples. (Example 1) 35 parts by weight of cellulose fiber, 15 parts by weight of synthetic fiber (aromatic polyamide fiber), 20 parts by weight of diatomaceous earth as an inorganic filler, and 10 parts by weight of cashew dust as a friction modifier are mixed into water. The material was dispersed and paper-made by a round-net paper-making machine to form a paper base material.

Next, suspension water containing 0.3% by weight of PTFE powder having an average particle diameter of 7 .mu.m ("Lublon powder L-5", manufactured by Daikin Industries, Ltd.) was poured onto the friction surface of the paper base material to obtain PTFE. The powder was deposited. The amount of the PTFE powder attached was 0.5% by weight based on the paper base material. And P
After drying the paper base material to which TFE powder adheres, it is impregnated with a phenol resin to a content of 20% by weight, air-dried and then placed in a mold kept at 200 ° C. to be heat-cured and wet-rubbed. A material was produced.

The surface roughness of the friction surface of the obtained wet friction material is
Maximum surface roughness (R _max ) of L = 8 mm and cutting level p =
It is expressed as a relative load length t _p % of 5 μm, and the results are shown in Table 1. The relative load length is also called a contact ratio, and the larger the value, the higher the smoothness. In addition, using a mechanical testing laboratory type friction tester, a cylinder on which the obtained friction material is pasted and a flat plate made of steel are combined to obtain an automatic transmission oil (AT
In F), the μ-v characteristic which is an index of the judder characteristic was measured. The test conditions are a surface pressure of 15 kgf / cm ² and an oil temperature of 80.
The sliding speed was stepped up to 0 to 2 m / s at 0 ° C. The results are shown in Fig. 1. (Example 2) The same as Example 1 except that the amount of the PTFE powder adhered was 1% by weight based on the paper base material. The results of surface roughness measured in the same manner as in Example 1 are shown in Table 1 and μ−
The v characteristic is shown in FIG. (Example 3) The same as Example 1 except that the amount of the PTFE powder adhered was 2% by weight based on the paper base material. The results of surface roughness measured in the same manner as in Example 1 are shown in Table 1 and μ−
The v characteristic is shown in FIG. (Comparative Example 1) The same as Example 1 except that the PTFE powder was not attached and the paper base material was used as it was. The results of surface roughness measured in the same manner as in Example 1 are shown in Table 1, and the μ-v characteristics are shown in FIG. (Comparative Example 2) The same as Example 1 except that the amount of the PTFE powder adhered was 0.05% by weight based on the paper-based substrate. Table 1 shows the results of surface roughness measured in the same manner as in Example 1.
The μ-v characteristics are shown in FIG. (Comparative Example 3) The same as Example 1 except that the amount of the PTFE powder adhered was 3% by weight with respect to the paper base material. The results of surface roughness measured in the same manner as in Example 1 are shown in Table 1 and μ−
The v characteristic is shown in FIG.

[0014]

[Table 1] (Evaluation) From Table 1, the wet friction materials obtained in each example are
It can be seen that the surface smoothness is improved as compared with the wet friction material obtained in Comparative Example 1. Further, in the wet friction material obtained in Comparative Example 2, the smoothness was not improved so much because the amount of the PTFE powder attached was small.

1 and 2, the wet friction materials obtained in the examples show a smooth positive gradient in which the friction coefficient (μ) increases as the sliding speed (v) increases, and judder is less likely to occur. I understand. However, in the wet friction materials obtained in Comparative Example 1 and Comparative Example 2, the friction coefficient is not stable and shows a negative gradient which is disadvantageous to judder. Further, in the wet friction material obtained in Comparative Example 3 in which the amount of PTFE adhered was large, μ-v
Although the characteristic shows a positive gradient, it is not suitable for practical use because the friction coefficient is significantly reduced.

That is, it is apparent that the wet friction material having high surface smoothness and less likely to cause judder can be manufactured by the manufacturing method of this embodiment.

[0017]

According to the method of manufacturing a wet friction material of the present invention, it is possible to easily and reliably manufacture a wet friction material which prevents a judder from the beginning of use and exhibits a stable shift feeling. Further, since the initial wear generated in the conventional wet friction material is reduced, the life of the friction material is extended.

Further, since PTFE is excellent in mold releasability, stains on the mold during heat molding are small. Therefore, the maintenance pitch of the mold becomes long, and the number of steps can be reduced.

[Brief description of drawings]

FIG. 1 is a μ-v chart of a wet friction material obtained in an example of the present invention.
It is a graph which shows a characteristic.

FIG. 2 μ-v of a wet friction material obtained in a comparative example of the present invention
It is a graph which shows a characteristic.

Claims (1)

[Claims] 1. A step of forming a paper base material by making a paper from a mixed material containing a base fiber, an inorganic filler and a friction modifier, and a polytetrafluorocarbon having a particle diameter of 10 μm or less on the surface of the paper base material. A step of adhering 0.1 to 2% by weight of fluoroethylene (PTFE) powder to the paper base material and a step of impregnating the paper base material to which the PTFE powder adheres with a binder resin and heat-molding are sequentially performed. A method of manufacturing a wet friction material, which is characterized by carrying out.