JP2601065B2 - Friction material and heat treatment method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment method for a friction material, and more particularly to a friction material suitable for improving the fade resistance of a brake pad for an automobile and a heat treatment method for the friction material. .

[0002]

2. Description of the Related Art Conventionally, a friction material formed by mixing a filler and a binder with a base material such as a metal fiber, a glass fiber, and a ceramic fiber is used for a brake pad for an automobile. I have.

In this heat treatment method for a friction material, heat treatment is performed in a non-oxidizing atmosphere at a heat treatment condition of 400 to 1000 ° C. to partially carbonize a binder of a thermosetting resin, preferably a phenol resin, By forming a thermally stable carbonaceous material that generates a small amount of decomposition products at the time of removal, the cause of the decrease in the friction coefficient of the friction material can be eliminated and the temperature can be increased. There is one in which the occurrence of a phenomenon of a decrease in braking (fade phenomenon) due to deterioration of a friction material under a high load is prevented. (See JP-A-59-113038)

[0004] By this heat treatment method, the generation of squeal during braking at low speed is reduced, and the friction characteristics at high temperatures are enhanced.

[0005]

However, when the resin mold disk brake pad is heat-treated in a non-oxidizing atmosphere, there is a problem that the metal fibers as the base material are deteriorated by heat, and the strength of the friction material is reduced. Also, when a conventional phenol resin is used, thermal degradation causes
In particular, there is a problem that the wear resistance at high speed is reduced.

The present invention has been made in view of the above problems, and aims at improving mechanical strength by adding a low concentration of oxygen to a heat treatment atmosphere and forming an oxide film as a reinforcing material around fibers. In addition, by using a heat-resistant copolymer resin of p-phenylphenol and phenol, it is possible to improve the wear resistance particularly at high speeds, and to further improve p-phenylphenol and phenol. It is an object of the present invention to provide a friction material capable of improving the resistance to fade by partially carbonizing the above copolymer resin.

[0007]

The structure of the present invention for achieving the above object will be described with reference to FIG. 1 corresponding to an embodiment. The present invention relates to p-phenylphenol (1 to 100).
Volume%) and phenol (0-99 volume%) are copolymerized with formaldehyde using an acid or alkali catalyst,
Heat-resistant condensed p-phenylphenol and phenol copolymer resin as a binder, steel fiber,
A metal fiber which is conventionally used as a friction material, such as an aluminum fiber, a copper fiber, a brass fiber, a zinc fiber, a nickel fiber, a chromium fiber, and the like. A friction material formed by mixing a filler such as graphite, barium sulfate, etc., with an oxygen concentration of 0.1 to 10%
In the low oxygen concentration field, the treatment temperature is 250 ° C or more and 125
The heat treatment is performed under a set condition of less than 0 ° C.

[0008]

According to the present invention, the friction material which has been heat-treated by the above means is prevented from decreasing in strength by reinforcing the fiber as a base material with an oxide film by an oxidation reaction, and the heat-resistant resin is p-phenyl. By using a phenolic resin as a binder, a decrease in abrasion resistance due to thermal deterioration can be prevented, and a high temperature. Stable wear coefficient under high load.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.
The copolymer resin of p-phenylphenol and phenol as a binder is prepared by copolymerizing p-phenylphenol and phenol at a molar ratio of 1: 3 with formaldehyde using an alkali ammonia catalyst. By polymerizing and condensing,
A copolymer resin of p-phenylphenol and phenol according to the present invention is obtained.

Next, the p-phenylphenol-based resin thus obtained, the steel fiber of the base material, graphite and other fillers are blended according to the volume ratio (%) shown in Table 1, and the resulting mixture is uniformly mixed. And knead it.

[0011]

[Table 1]

Next, the above-mentioned composite material is filled in a mold and compression-molded at a temperature of 150 ° C. and a pressure of 500 kg / cm ² . The formed article is subjected to after-treatment at 200 ° C. for 4 hours under predetermined conditions.
After curing, the optimal oxygen concentration set as a condition for the heat treatment of the friction material is 0.1% or more and less than 10%, more preferably 1% or more and less than 5%. The optimum treatment temperature is 250 ° C. to less than 1250 ° C., preferably 350 ° C. to less than 800 ° C., and the treatment time is less than 4 hours, more preferably 30 minutes to 2 hours.

The reason for selecting the oxygen concentration, heat treatment temperature and treatment time as the above set conditions is that when the oxygen concentration exceeds 10%, the oxidation reaction of the p-phenylphenol-based resin as a binder starts to occur, and This is because the strength of the material becomes weak, and when the oxygen concentration is 0.1% or less, the oxidation reaction on the surface of the steel fiber occurs only slightly, making it impossible to improve the strength. is there.

Further, if the processing temperature exceeds 1250 ° C., rapid decomposition occurs, so that the gas generated inside the friction material cannot escape to the outside and tends to cause swelling or cracking. This is because even if the heat treatment is performed for a long period of time, the decomposition of the p-phenylphenol-based resin as a binder occurs only slightly, making it impossible to improve the fade resistance. On the other hand, if the processing time is 4 hours or longer, the change hardly occurs even if further processing is performed.

In the above embodiment, in order to confirm the effect of maintaining the strength by the oxygen concentration, specific examples thereof include an oxygen concentration of 0% to 10%, a heat treatment temperature of 400 ° C., and a treatment time of 1 hour.
The characteristics of the friction pad subjected to the time treatment were examined. There is a relationship as shown in FIG. 1 between the oxygen concentration and the bending strength. As is clear from FIG. 1, the friction pad treated in the oxygen concentration range of 1% to 10% has a higher bending strength than the friction pad treated in the non-oxidizing atmosphere (oxygen concentration 0%), and has a low oxygen concentration. The strength improvement by the heat treatment effect in the field was sufficiently demonstrated.

Further, in order to confirm the effect of improving the wear resistance of the friction material by using the p-phenylphenol-based resin, as a specific example, a heat treatment temperature of 400 ° C. and a treatment time of 1% in a 5% oxygen concentration field. About the wear resistance of the friction pad that has been treated for a long time, a full-scale dynamometer
It was examined by the amount of wear after braking 1000 times at 100 km / h and 100 ° C. using a motor. Table 2 shows the test results.

[0017]

[Table 2]

As is clear from Table 2, when a general phenol resin is used, the resin is thermally degraded by high-temperature heat treatment, and the amount of wear is more than twice that of a friction pad that has been subjected to conventional heat treatment. It can be seen that the abrasion resistance is reduced. However, by using p-phenylphenol-based resin, which is a heat-resistant resin, as a binder, not only thermal degradation due to high-temperature heat treatment is reduced, but also p-phenylphenol-based resin carbonized by high-temperature heat treatment. The skeleton is strengthened,
It can be seen that the amount of abrasion is improved to half or less of the conventional heat treatment.

Further, in order to confirm the effect of improving the fade resistance, as a specific example, the characteristics of a disk brake pad which has been subjected to a heat treatment temperature of 400 ° C. and a treatment time of 1 hour in a 5% oxygen concentration field. I checked.

The coefficient of friction when the heat-treated disk brake pad is continuously braked for 35 seconds based on JASOC 406 (1982) is as shown by the curve in FIG. A is a specific example subjected to the above heat treatment conditions, B is a conventional example of a normal heat treated product,
Heat treatment was performed at 00 ° C. for 4 hours. Curve A shows a stable wear coefficient for the initial wear (the number of braking times n is 10 or less) at 0.43, and shows a remarkable difference compared to the curve B. The example of curve A fully demonstrates the fade resistance due to the heat treatment effect.

[0021]

As is apparent from the above description, according to the present invention, the steel is formed by forming an oxide film on the surface of the steel fibers in the friction pad by changing the atmosphere to low oxygen during the heat treatment of the friction agent. Abrasion resistance of the friction pad is improved by using a copolymer resin of p-phenylphenol and phenol, which are heat-resistant resins, as a binder.
In addition, the thermal decomposition of the binder at a high temperature is previously carbonized by heat treatment, whereby the fade resistance can be improved.

Further, the present invention stabilizes the friction coefficient of the friction material at a high temperature and suppresses the ignition phenomenon caused by the pyrolysis gas generated at the time of braking without lowering the friction coefficient against sudden braking from a high speed. Can be. Further, it has a secondary effect of preventing squeal during braking.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a relationship between bending strength and oxygen concentration in a heat treatment atmosphere of a friction material of the present invention.

FIG. 2 is a characteristic comparison diagram showing a relationship between a braking coefficient and a friction coefficient of a friction material in an embodiment of the present invention and a conventional example.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Takuji Ito 1500 Oji Ogawa, Shimodate City, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd. Industrial Co., Ltd.

Claims (5)

(57) [Claims] A friction material containing p-phenylphenol and phenol as a binder, a metal fiber as a base material, graphite, metal powder and an inorganic filler is subjected to a hot pressing method. In the manufacturing method of friction material formed by hot pressing
The friction material is heat-treated in a low oxygen concentration field having an oxygen concentration of 0.1% to 10% under a setting condition of a temperature of 250 ° C. or more and less than 1250 ° C. and a heat treatment time of 15 minutes or more and less than 4 hours. Heat treatment method for friction material. 2. A friction material containing p-phenylphenol and phenol copolymer resin as a binder, a metal fiber as a base material, graphite, metal powder and an inorganic filler is subjected to a hot pressing method. In a friction material formed by hot pressing under pressure, the friction material has a temperature of 250 ° C. or more and less than 1250 ° C. and a heat treatment time of 1 in a low oxygen concentration field of 0.1% to 10% oxygen concentration.
A friction material, wherein heat treatment is performed under a set condition of not less than 5 minutes and less than 4 hours. 3. The friction material according to claim 1, wherein the metal fiber is a steel fiber. 4. The friction material according to claim 2, wherein the copolymer resin of p-phenylphenol and phenol is synthesized using an acid as a catalyst. 5. The friction material according to claim 2, wherein the copolymer resin of p-phenylphenol and phenol is synthesized using an alkali as a catalyst.