JPS6215281A - Friction material composition - Google Patents

Abstract

PURPOSE:To provide the titled composition incorporated with specified amount of MgO powder of particle size below specific diameter, having low thermal conductivity with wear resistance equivalent to that of semimetallic pad, of high coefficient of friction even at high-speed brake, for use as disc brake pad, etc. CONSTITUTION:The objective composition can be obtained by incorporating (I) 8-12vol% of magnesium oxide powder of a maximum particle size <=250mum in (II) a friction material prepared by mutually bonding, using thermosetting resin binder, between (A) reinforcing fibrous material (pref. steel fiber, stainless fiber, Al2O3-SiO2 fiber, aromatic polyamide fiber, or pulp) (B) organic filler, (C) inorganic filler, (D) metallic powder, and (E) friction regulator.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to improvements in friction material compositions for disc brake pads, brake linings, etc. used in automobiles and the like.

Conventional technology and problems to be solved by the invention Conventionally, friction materials used in disc brake pads, brake linings, etc. include asbestos fibers, various inorganic and organic powder fillers, organic friction modifiers, and phenolic resins. It is used after adding a thermosetting resin binder such as, heat press molding, and hardening.

However, as the debate regarding the harmfulness of asbestos powder has increased in recent years, there has been an increasing need for friction materials that do not use asbestos fibers.

Fibers other than asbestos fibers include metal fibers, glass fibers, ceramic fibers, synthetic fibers, etc. Pads using steel fibers are called semi-metallic pads and are partially in practical use. This semi-metallic pad is
As stated in Japanese Patent Publication No. 411i-7258, steel fibers (including iron powder) are used in large quantities along with lubricants such as graphite (this has superior wear resistance compared to asbestos pads). Although it has excellent performance such as a high coefficient of friction, the thermal conductivity of the pad is high (4 to 5 times that of asbestos pad), and when braking is repeated, the brake fluid temperature rises rapidly, making it easy to cause paper lock. Therefore, we have taken measures such as installing a heat insulating layer on these pads.In addition, we have observed a phenomenon in the market that does not occur with conventional asbestos pads, such as ignition when braking repeatedly at high speeds. Due to these circumstances, the superiority of steel pads is gradually decreasing, and it has become necessary to develop a new type of non-asbestos friction material to replace steel pads.

The present inventors used ceramic fibers and aramid rubber without using steel fibers as much as possible.
Furthermore, by adding a small amount of silicon carbide powder, a friction material with performance equivalent to or better than conventional steel pads was obtained.

However, this new type of non-asbestos rubber was not able to achieve the target friction coefficient (0.3 or more) in an evaluation test that simulated braking on a highway.

Means for Solving the Problems In order to solve the above problems, the inventors of the present invention have conducted various studies, and as a result, they have decided to use ceramic fibers and aramid pulp as reinforcing base materials instead of using steel fibers as much as possible. By replacing it with
4~! With a thermal conductivity of about 15, it has wear resistance equivalent to semi-metallic pads, and has a high wear coefficient (0.3
It has been found that a friction material composition for disc brake pads, brake linings, etc. having the above) can be obtained.

The present invention provides reinforcing fiber materials, organic fillers, inorganic fillers,
A friction material made by bonding metal powder, friction modifier, etc. with a thermosetting resin binder, with a maximum particle size of 250 μm.
The present invention relates to a friction material composition containing 8 to 12% by volume of the following magnesium oxide powder.

The friction material composition of the present invention contains O as a reinforcing base material.

Steel fiber 5-I5 volume%, Af1203-8
5 to 5% by volume of IG ceramic fiber and 5 to 30% by volume of aromatic polyaramid pulp are used, and contain solid lubricants such as a phenolic resin binder, graphite, and antimony sulfide, and if necessary, copper powder, etc. Metal powder, organic friction modifier, barium sulfate, etc. are added.

Magnesium oxide used in the present invention must have a maximum particle size of 250 μm or less; if the particles are larger than 250 μm, the amount of pad wear and the aggressiveness of the disk (opposing material) will increase rapidly, and the stability of the friction coefficient will decrease. Significantly worsened;
The purpose of the present invention cannot be achieved.

Further, the amount added needs to be 8 to I2% by volume. If it exceeds 12% by volume, the friction coefficient will exceed 0.3 or the aggressiveness to the opponent will increase significantly, and the stability of μ will deteriorate.

If the amount is more than 8% by volume, the objective of the present invention cannot be achieved in terms of braking effectiveness at high speeds.

The present invention will be described in detail with reference to Examples below.

EXAMPLES COMPARATIVE EXAMPLES AND CONVENTIONAL EXAMPLES The components shown in Table 1 were blended and mixed uniformly using a mixer. A predetermined amount of this mixed composition was weighed, and a surface pressure of 300 kg was applied.
/c/, mold temperature IG 5° C., and molding time 7 minutes using a compression molding machine. Thereafter, heat treatment was further performed at 200° C. for 5 hours to polish the surface to obtain a disc brake pad.

The disc brake pads obtained in the Examples, Comparative Examples, and Conventional Examples shown in Table 1 and above were tested with a full-size dynamometer at the third effectiveness of test code JASOG914, 130 km/
The test was conducted using a stetocord that added high-speed efficacy tests of 180 km/H and 180 km/H after Hz. , the results are shown in Table 2.

As shown in Table 2, within the range of 8 to 12% by volume of magnesium oxide, a friction coefficient of 0.3 or more during high-speed braking could be achieved without deteriorating the aggressiveness of the disc rotor.

Table 2
/Cm" minimum value of 5 times braking.

The test was conducted using the following specifications.

On the other hand, the thermal conductivity was measured by cutting out a test piece (lo++mφ×1.2mm) from the pad assembly and using a laser flash method. The results are shown in Table 2.

Effects of the Invention According to the present invention, the thermal conductivity of the pad is approximately 1/4 that of a conventional semi-metallic pad! 75, it is possible to obtain a disc brake material having characteristics such as high-speed braking performance and wear resistance that are similar to or better than semi-metallic pads.

Claims (6)

[Claims] (1) In a friction material made by bonding a reinforcing fiber material, an organic filler, an inorganic filler, a metal powder, and a friction modifier with a thermosetting resin binder, magnesium oxide powder with a maximum particle size of 250 μm or less is added to A friction material composition characterized by containing ~12% by volume. (2) The friction material composition according to claim 1, wherein the reinforcing fiber material is made of one or more types of fibers selected from the group consisting of metal fibers, ceramic fibers, and synthetic fibers. thing. (3) The friction material composition according to claim 1, wherein the reinforcing fiber material is steel, stainless fiber, or both. (4) The friction material composition according to claim 1, wherein the reinforcing fiber material is made of Al_2O_3-SiO_2. (5) The friction material composition according to claim 1, wherein the reinforcing fiber material is aromatic polyaramid fiber or pulp. (6) SiC with a maximum particle size of 5 μm or less as one of the inorganic fillers
The friction material composition according to claim 1, characterized in that it contains 0.2 to 2.0% by volume of powder.