JPS6043387B2 - Friction material composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a friction material composition for disc brake pads, brake linings, etc. used in automobiles and the like.

For example, disc brakes are used as control devices for automobiles and the like, but conventional disc brakes generate an unpleasant noise called brake squeal when braking.

The brake squeal phenomenon that occurs during control has recently become a serious problem, particularly in the general market, and various efforts have been made to investigate its causes and take countermeasures.

This brake squeal phenomenon is a high-frequency sound with a frequency of 2,000 to 3,000 Hz or more, but automobile brake squeal also includes a low-frequency sound of about 100 to 300 Hz, which occurs especially when automatic cars start and stop. There's a strange noise.

This low-frequency noise is caused by instantaneous fluctuations in the coefficient of friction between the mating material and the friction material at low speeds, and sometimes the vibrations are large enough to cause the vehicle body to vibrate.

Recently, it has been known that this low-frequency noise occurs very significantly in semi-metallic disc brake pads that use steel fiber as an asbestos substitute fiber.

For this reason, with the future growth in the number of automatic cars and the trend toward non-asbestos (semi-metallic), this is becoming a major problem that needs to be solved, just like general high-frequency noise. In order to solve the above-mentioned low-frequency abnormal noise using a disc pad material, which is a friction material, we investigated the fluctuation of the friction coefficient at a speed of O and about 5 rotations/hour, and found that the magnitude of the abnormal noise level and the fluctuation of the friction coefficient It was recognized that there is a correlation between the size of the width. In other words, it was found that the greater the noise level, the greater the fluctuation range of the friction coefficient.

This is presumed to be due to the stick-slip phenomenon occurring more often at the friction interface when the noise is louder. In view of the above circumstances, it is an object of the present invention to provide a friction material composition for preventing or reducing low frequency noise and vehicle body vibration.

As a result of various studies conducted by the present inventors in order to eliminate the above-mentioned drawbacks, the present inventors found that by incorporating 5 to 3 mass% of lubricant particles with a maximum particle size of 50 μm or less into a friction material composition, the friction coefficient decreased. It has been found that it is possible to obtain a friction material composition that provides a friction material for disc brake buds, brake linings, etc. that has a small fluctuation range.

The present invention relates to a friction material composition containing 5 to 3 weight percent of lubricant particles having a maximum particle size of 50 pm or less in the entire composition.

In the present invention, it is necessary that the lubricant particles have a maximum particle size of 50 μm or less; if the maximum particle size exceeds 50 μm, the variation range of the coefficient of friction becomes large and the object of the present invention cannot be achieved.

Graphite, molybdenum disulfide, etc. are used as lubricants.
These may be contained alone or in combination of two or more without any limitation.

These lubricants need to be contained in the total composition in an amount of 5 to 3% by volume; if the amount is less than 5% by volume, a sufficient effect will not be obtained, and if it exceeds 3% by volume, the coefficient of friction will decrease. 0.30
There is a drawback that the original frictional performance is impaired. The present invention will be explained below with reference to Examples.

Example 1 The ingredients shown in Table 1 were blended, mixed uniformly using a mixer, dried in an electric oven at 82.5±2.5°C for 2 hours, and then crushed to form a molded powder, and then made into a tablet. Formed, then temperature 152.5±2.5°C1 pressure 50
Hot pressure molding for 5 minutes under the condition of 0k9/Clt, and further 200
A semi-metallic disc brake pad was obtained by firing at 0C for 5 hours.

Example 2 The components shown in Table 2 were blended and the same steps as in Example 1 were carried out to obtain a semi-metallic disc brake pad.

Note that the same fine graphite as in Example 1 was used. *Maximum particle size: 10P7TL or more Example 3 The components shown in Table 3 were blended and the same steps as in Example 1 were carried out to obtain a semi-metallic disc brake pad.

The fine molybdenum disulfide used was the same as in Example 2. *Maximum particle size 10P7TL or more Comparative Example 1 Semi-metallic disc brake pads were produced using coarse graphite particles with a diameter of 0.5 to 2 gourds instead of fine particles as a lubricant, and using the same formulation and process as Example 1. I got it.

Next, the temperature of the semi-metallic disc brake pad using the friction material composition of the present invention and the conventional semi-metallic disc brake pad (comparative example 1) was 50±10.
The fluctuation range of the friction coefficient at a constant speed of 0.5 h/hour was investigated.

The results are shown in FIG. As can be seen from FIG. 1, the semi-metallic disc brake pad using the friction material composition of the present invention has a coefficient of friction variation range of 0.01 to 0.0.
It was confirmed that it was as small as 3. On the other hand, it was confirmed that conventional semi-metallic disc brake pads had a large fluctuation range of friction coefficient of 0.05 to 0.06. Also, semi-metallic disc brake pads using the friction material composition of the present invention were confirmed to have a large fluctuation range of 0.05 to 0.06. and a conventional semi-metallic disc brake pad were installed on an actual car, and a comparative test was conducted to determine the generation of low-frequency noise.

The results are shown in Table 4. In Table 4, after 500km of running-in, the initial speed is 60km/hour.
Measurements were taken after driving for 500 hours with the brake applied at a deceleration rate of 0.3y and a ratio of 2 times/1. Measurements were taken after applying the powder and leaving it as it was for 3 minutes. Test car: [1800
CC automatic vehicle, temperature is temperature of semi-metallic disc brake pad, area of semi-metallic disc brake pad is 38 d, total vehicle weight 1320 kg, brake type, collet type] In the present invention, the case where it is applied to a semi-metallic disc brake pad has been explained. However, the present invention can provide similar effects with other friction materials such as disc brake pads and brake linings.

In the present invention, since the entire composition contains 5 to 30% by volume of lubricant in the form of fine particles with a maximum particle size of 50 pm or less, the range of fluctuation in the coefficient of friction is reduced, and low-frequency noise and vehicle body vibration are completely eliminated. A friction material composition is obtained that provides disc brake pads, brake linings, etc. with no or very small disc brake pads.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between friction coefficient and time when a conventional semi-metallic disc brake pad is used, Figures 2, 3 and 4 are graphs showing the relationship between friction coefficient and time when a conventional semi-metallic disc brake pad is used. It is a graph showing the relationship between the coefficient of friction and time when a semi-metallic disc brake pad is used.

Claims (1)

[Claims] 1. A friction material composition containing 5 to 30% by weight of a lubricant in the form of fine particles having a maximum particle size of 50 μm or less in the entire composition.