JPH0255655B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in brake lining materials that can withstand braking at high speeds for aircraft, automobiles, electric locomotives, etc.

Conventionally, carbon fibers have been used as reinforcing materials, and carbon fibers have been used as fillers in combination with zero or a small amount of metal powder such as iron, cast iron, lead, etc., with the amount of friction and wear adjusted. Processing of a composite produced using one or more of the following as binders: so-called pyrolytic carbon produced by reaction, phenolic resin, and petroleum pitch or coal pit treated at high temperatures (for example, 1500°C). brake lining material.

When such brake lining materials are used in the brake bands of aircraft, automobiles, etc. that require braking force at high speeds, the frictional heat generated during braking causes them to become instantly (for example, 30 seconds) at high temperatures (for example, about 1000°C). In some cases, carbon-based materials such as carbon fibers are oxidized by oxygen in the air, especially in parts of the structure that are exposed to air during braking, and as a result, the brake lining material is damaged and falls off from the brake band as it loses its reinforcing function. It had some drawbacks, such as being stowed away.

The present invention aims to provide a material that protects carbon-based substances such as carbon fibers, which are oxidized in the parts of the lining material that are exposed to air during braking when the surface temperature of the brake lining material increases due to high-speed friction. It is something to do.

In other words, an oxide is formed on the friction surface under high temperature, which is a silicon compound and has a coefficient of thermal expansion almost equal to that of the carbon-based main body. Alternatively, it is preferable that a heat-resistant material with a structure close to pore-free be formed firmly with the main body, and it has been found that silicon carbide and silicon nitride are optimal as these materials. The above technical problem is attempted to be solved by coating any of these on surfaces other than the surface of the carbon fiber and the friction surface of the composite.

The coating method for silicon carbide and silicon nitride mentioned above is the so-called chemical vapor deposition method (CVD method).
In addition, physical vapor deposition methods (PVD) such as sputtering
law) should be adopted.

The brake lining agent of the present invention includes carbon fiber (reinforcing material) coated with silicon carbide or silicon nitride, carbon (filler) and pyrolytic carbon, phenolic resin, petroleum pit treated at high temperature (for example, 1500°C), or A binder consisting of one or more types of coal pitch is blended in a predetermined ratio, mixed uniformly to form a mixture, and then this mixture is supplied to a mold and heated at a predetermined pressure and temperature. Pressurized and heated to form a molded body, fired this molded body at a predetermined temperature in an air flow of N ₂ gas to form a fired body, and coating the surfaces other than the friction surfaces of this fired body with silicon carbide or silicon nitride. It is obtained by Incidentally, the carbon fiber serving as the reinforcing material is coated with silicon carbide or silicon nitride in advance by CVD method or the like. Due to its structure, composites containing carbon fibers tend to be easily oxidized at the boundary between the filler and the carbon fibers. When the carbon fiber is oxidized, it cannot function as a reinforcing material, and the overall strength decreases. Therefore, this can be prevented by coating the carbon fiber as described above.

In addition, the selection of materials for the mixture and the adjustment of the composition ratio are as follows:
A conventionally used composition may be used, and the composition ratio may be similarly adjusted to obtain the desired performance. Further, each of the above manufacturing conditions, ie, temperature, pressure, time, atmospheric gas, etc., may be appropriately determined depending on the mixed materials, the thickness of the lining material, and the usage conditions.

The brake lining material of the present invention obtained in this way has a very high sliding speed, and therefore, when used for braking under conditions where the temperature of the friction surface is very high, the brake lining material and the brake drum have a very high sliding speed. The frictional heat slightly oxidizes the silicon carbide or silicon nitride coating layer, causing only a slight plastic flow of silicon dioxide, etc., and the coating itself does not fall off from the brake lining. This is because the carbon fibers are not exposed, oxidation is prevented, and the strength of the brake lining material itself is maintained.

On the other hand, silicon carbide and silicon nitride on fibers exposed to the friction surface have a high coefficient of friction at room temperature, but under conditions of high sliding speed and high friction surface temperature, the coefficient of kinetic friction decreases to a predetermined value of 0.3 to 0.4. Can be maintained. This is based on the above-mentioned plastic flow, and the oxide film of Fe ₂ O ₃ , FeO, etc. on the drum side and the oxide film of SiO ₂ , etc. on the brake lining surface act as a kind of lubricating film, and the film serves the purpose. This is because a predetermined coefficient of kinetic friction is maintained as a result of the frictional force exhibiting a frictional force that is very different from the friction between materials.

As described above, it is clear that the braking effect of the SiC or SiN layer in the brake lining material of the present invention is comparable to that without a coating layer, and furthermore, it has the effect of being able to withstand use at high temperatures. Carbon-carbon (C-C) composites are braked by sliding surface to surface. At this time, for example, the temperature will reach about 1000℃ in 30 seconds. This causes oxidative damage to the carbon. Since the surfaces of the carbon rub against each other, the free surfaces, that is, the sides of the disk and the sides of the central shaft hole, are also oxidized. One way to prevent this is to incorporate magnesium phosphate into the disk to treat the entire disk to prevent oxidation. As mentioned above, since the entire device becomes high temperature, simply coating the free side surface with SiC or the like to prevent oxidation can overcome the drawbacks of the conventional method.

Claims (1)

[Claims] 1. In a brake lining material formed of a composite consisting of carbon fiber, carbon and one or more binders of pyrolytic carbon, phenolic resin, petroleum pitch, and coal pitch, the friction between the surface of the carbon fiber and the composite A brake lining material characterized by having a coating layer of silicon carbide or silicon nitride formed on surfaces other than the surface.