JPS62237127A - Friction material - Google Patents

Abstract

PURPOSE:To lower thermal conductivity while retaining wear-resistance and fade-resistance of the conventional semi-metallic friction material and to obtain the optimum and excellent friction material by using an inorganic binding material and reinforcing resin suitable for use as a friction material for a brake or a clutch. CONSTITUTION:A friction material is formed by 5-35% metallic fiber, 10-50% inorganic fiber or organic fiber or both of them, 0-30% organic binding material, 10-60% inorganic binding material and 10-60% filler by volume. In this material, in order to hold down the additional amount of metallic fiber which conventionally raises thermal conductivity as much as possible and reduce a decrease in heat resistance, wear-resistance, and fade-resistance due to a lowering of metallic fiber content, reinforcing fiber and inorganic binding material which has low thermal conductivity and is rich in heat-resistance are added. Accordingly, while wear-resistance and fade-resistance of the conventional semi- metallic friction material are retained, the thermal conductivity is lowered to obtain the optimum and excellent friction material for a brake or a clutch.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a friction material used in brakes and clutches of automobiles.

[Prior Art] f! has been conventionally used in brakes and clutches of automobiles, etc. ! Rubber materials have been made using asbestos fibers as a base material. In other words, conventional friction materials have reinforcing fibers of 10 to 60
It consists of asbestos fiber of % by volume, thermosetting resin of 15-40% by volume as a binder, and various metal particles, inorganic powder and organic powder as a filler, and these components are mixed, molded and polished. It was manufactured.

However, in recent years, asbestos fibers have been found to be harmful to the human body, and friction materials based on asbestos fibers have become subject to regulations regarding production and use.Therefore, there is a need to develop new friction materials to replace asbestos fibers. is an urgent need.

Recently, alternative raw materials for asbestos fibers have been sought, and semi-metallic friction materials based on metal fibers, especially steel fibers, which have good reinforcing properties and heat resistance, are easy to obtain, and are promising from a cost perspective, have been developed. It has come to be used primarily as brake pads for automobiles. This semi-metallic friction material 1? K 4 years old is made of metal components such as steel fiber and iron powder, and graphite gold as the main component, and is made of organic filler and inorganic filler, and is hardened with organic binder such as phenol resin.

[Problems to be Solved by the Invention] The above-mentioned semi-metallic friction material contains metal components with high thermal conductivity and a large amount of graphite, so it has superior wear resistance and fade resistance compared to asbestos-based friction materials. However, it has the drawback of having excessively high thermal conductivity, which causes thermal problems when used as a friction material for brakes and clutches.

For example, when used as a brake pad for a disc brake, a large amount of frictional heat is generated on the sliding surface of the brake disc and brake pad due to sudden braking from high speeds or continuous braking when dismounting, and the semi-metallic material is heated. Due to its high conductivity, this frictional heat is in turn conducted through the interior of the pad and its back plate into the hydraulic cylinder mechanism of the brake caliper. The high temperature caused by this heat conduction causes the rubber boots and rubber rings of the piston seal to deteriorate, causing brake fluid to leak. In addition, the brake fluid boils at a high temperature, causing a so-called paper lock phenomenon, which makes the brakes ineffective and extremely dangerous.

Conventionally, a method of dealing with this problem has been to install some kind of heat insulating layer between the brake pad and the brake caliper. In other words, methods include a method in which a heat barrier layer is integrally molded and installed between the semi-metallic material layer of the brake pad and the back plate, and a method in which an insulator is pasted on the back side of the back plate 1 of the pad. . However, these heat insulating layers currently rely on asbestos-based materials, which cannot be said to be preferable from the viewpoint of the asbestos regulations mentioned above. Furthermore, an increase in the cost of materials and the number of processing steps results in an increase in cost, which also poses a problem from an economic point of view.

Furthermore, in order to solve the thermal problems of semi-metallic friction materials, various proposals regarding the material composition of the friction materials have been made. In other words, the thermal conductivity of semi-metallic friction materials changes depending on the amount of metal fibers and graphite in the material composition, and if the amount of metal fibers, graphite, or both is reduced, the thermal conductivity decreases and the above-mentioned thermal conductivity decreases. However, the excellent wear resistance and fade resistance of semi-metallic friction materials are significantly impaired.

Therefore, in place of metal fibers and graphite in the material composition of semi-metallic friction materials, various alternative fibers and solid lubricants have been proposed that have strength comparable to asbestos fibers and low thermal conductivity.For example, as reinforcing fibers, Glass fibers, slag wool, ceramic fibers, carbon fibers, heat-resistant organic fibers, etc. have been proposed, and metal sulfides, polyimide resins, fluorine resins, etc. have been proposed as solid lubricants, but the above components are Both methods damage the mating disk, are expensive, are difficult to mix uniformly during the manufacturing process, and lack wear resistance and fade resistance, and are therefore impractical.

Therefore, the purpose of the present invention is to solve the above-mentioned problems, to make use of the wear resistance and fade resistance of semi-metallic friction materials, and to reduce thermal conductivity, thereby creating a friction material that is optimal and excellent as a friction material for brakes and clutches. is to provide.

[Means for Solving the Problems] That is, the present invention uses 5 to 35% metal fibers, 10 to 50% inorganic fibers or organic fibers, 10 to 50% organic binders, 0 to 30% organic binders, and inorganic binders. The friction material is composed of 10 to 60% by volume of filler and 10 to 60% by volume of filler.

[Function] The friction material of the present invention suppresses as much as possible the amount of metal fibers added, which is a cause of increasing the thermal conductivity of conventional semi-metallic friction materials, and improves heat resistance, wear resistance, and resistance due to the reduction in metal fiber content. In order to minimize the decrease in fading properties, reinforcing fibers (organic fibers and/or inorganic fibers) with low thermal conductivity and high heat resistance and an inorganic binder are added.

The metal fibers used in the friction material of the present invention may be any of the metal fibers conventionally used in semi-metallic friction materials, such as steel fibers, stainless steel fibers, bronze fibers, etc. These fibers can be used alone or in combination of two or more. This metal fiber is used to provide durability by increasing the toughness and heat resistance of the friction material. In addition, by increasing the thermal conductivity of the friction material, a large amount of frictional heat generated on the friction sliding surface can be quickly diffused, preventing a temperature rise on the sliding surface of the friction material, and increasing the heat of the sliding part of the friction material. prevent physical and chemical deterioration,
It is used to improve wear resistance and fade resistance. However, if a large amount of metal fiber is used, thermal problems of the brake will occur as described above. The amount of metal fibers added can be selected to control thermal problems to the desired degree, but typically ranges from 5 to 35 percent by volume of the final friction material.

In the friction material of the present invention, reinforcing fibers other than metal fibers are used in combination with metal fibers in order to solve the above-mentioned thermal problem and compensate for the decrease in strength due to the reduction in metal fibers.

The reinforcing fibers are inorganic fibers or organic fibers other than asbestos fibers, or both, and have low thermal conductivity, high heat resistance, and high strength, such as glass fiber, rock wool (PMF), wollastonite, and titanic acid. potash fiber,
Aramid fibers [e.g. trade name Kevlar (manufactured by DuPont)
] etc. are preferable. The amount of addition of organic fibers and/or inorganic fibers 1 depends on the above-mentioned thermal problems, reinforcing properties, formability, amount of metal fibers added, etc.
It is 50% by volume. In addition, each of the organic fibers and inorganic fibers can be used alone, or two or more types can be used in combination.

The amount of metal fibers + organic fibers and/or inorganic fibers is usually about 15 to 60% by volume of the final friction material,
Preferably it is 20 to 40% by volume. If the total addition amount is less than 15% by volume, reinforcement of the friction material becomes insufficient, which is undesirable, and if it exceeds 60% by volume, molding becomes difficult, which is not preferred.

As mentioned above, when using automobile brakes, a large amount of frictional heat is generated when the brakes are subjected to severe use such as sudden braking from high speeds or continuous braking when exiting the vehicle. Conventional friction materials contain organic binders, such as phenolic resins, and contain a large amount of organic matter, resulting in a large amount of RIJ? ! l! Heat degrades these organic substances. If the binder deteriorates and decomposes due to heat, the bond between the friction materials becomes weaker, causing severe wear, and decomposition gas exists on the sliding surface, causing gas lubrication and reducing braking force. A decrease or fade phenomenon occurs. Conventionally, methods to prevent this have been to reduce the amount of organic binder used to reduce the source of decomposed gas, or to add thermally conductive substances such as metal components and lead to quickly remove the large amount of frictional heat generated by friction sliding. It was diffused and removed from the sliding surface to prevent abnormal temperature rises on the sliding surface. However, in this method, the thermal conductivity of the friction material itself becomes too high, causing paper lock as described above, and a satisfactory friction material cannot be obtained. In order to eliminate these drawbacks, the friction material of the present invention uses an inorganic bonding material that is strong against heat and has low thermal conductivity alone or in combination with the above-mentioned organic bonding material.

Examples of the inorganic binder used in the friction material of the present invention include silica-based, alumina-based, zirconia-based, phosphate-based, and boric acid-based hardening agents, and inorganic binders that are reactively hardened by firing. In particular, phosphate-based knots made of aluminum phosphate are most suitable. The amount of the inorganic binder added is related to the amount of the organic binder added, but is usually 10 to 60% by volume of the final friction material. If the amount of the inorganic binder added is less than 10% by volume, the bond will become weak and the heat resistance will also decrease, which is not preferable, and if it exceeds 60% by volume, the friction material will become hard and Undesirable because it becomes brittle.

Conventional organic binders can be used in the friction material of the present invention. Examples of organic binders include thermosetting resins such as phenolic resins. The amount of the organic binder added is related to the amount of the inorganic binder mentioned above, but is usually 0 to 30% by volume. If the amount of the organic binder added exceeds 30% by volume, it is not preferable because the heat resistance of the friction material decreases.

The amount of additive α of the organic binder and the inorganic binder is usually 10 to 60% by volume of the final friction material, preferably 20 to 60% by volume.
It is volume %. If this amount is less than 10% by volume, the bonding force will be weak, which is undesirable, and if it exceeds 60% by volume, it will be undesirable because it will reduce the heat resistance or make the friction material brittle.

Organic fillers and/or inorganic fillers can be used in the friction material of the present invention. For example, cashew dust, rubber dust, etc. can be used as the organic filler, and can improve brake squeal and low-temperature wear resistance, but if used in large quantities, they have the same drawbacks as the organic binder mentioned above. undesirable because of the In addition, as inorganic fillers, sulfur such as PbS, 5b2S, MoS2, SiO2, AI203, Cao, Fe20
z, oxides such as M3C, Ca(OI()2, CaC
Salts such as Oz, Ba5O, graphite, carbon black, talc, mica, etc., and metals such as Fe, Cu,
Powder particles of Zn, Sn, brass, bronze, AI, PB, or an alloy thereof can be used. The filler is used for the purpose of adjusting the coefficient of friction, reducing wear, reducing cost, etc., and two or more of the above-mentioned fillers can be used in combination depending on the purpose. The total amount of filler can be varied depending on the purpose, but is usually within the range of 10 to 60% by volume.

Is the friction material of the present invention different from conventional friction materials? ! For example, each J
g. Weigh a predetermined amount of the material mixed uniformly, put it into a mold, and press it with a heat press at a temperature of 100 to 300°C and a pressure of 100°C.
~500 kgl c volume 2, pressed for 5 to 30 minutes, then fired at 150 to 350°C for 1 to 8 hours, and then polished to a predetermined thickness. It can be manufactured at KL.

[Example] After uniformly mixing each raw material having the distribution shown in Table 1 below, a predetermined amount was weighed, put into a mold, and heated with a heat press at a temperature of 150°C and a pressure. A disk bat was molded at 300 kgl am2 for 10 minutes, then fired at 220° C. for 4 hours, and then the friction surface was polished to a predetermined thickness to produce a test sample. The formulations of the comparative products shown in Table 1 are the formulations of current typical semi-metallic friction materials.

Using the obtained test sample, a friction performance test was conducted using an inertial dynamometer according to JASOC-406. At this time, the lowest friction coefficient of the fade test, the temperature of the back surface of the pad, and the amount of friction 1f after the test were measured and are also listed in Table 1.

From Table 1, it can be seen that the back surface temperature of both invention products 1 and 2 is lowered by 35 to 60° C. compared to the comparative product, and the thermal conductivity is improved. However, since the product 2 of the present invention has a larger amount of metal fibers than the product 1 of the present invention, the back surface temperature is accordingly slightly higher. In addition, the minimum fade friction coefficient and wear amount of products 1 and 2 of the present invention are as good as, if not better than, those of the comparative product.

[Effects of the Invention] As described above, the friction material of the present invention uses an inorganic binder and reinforcing fibers (organic fibers and/or inorganic fibers) suitable for the application, so it is superior to conventional semi-metallic R friction materials. Thermal conductivity can be lowered while maintaining wear resistance and fade resistance, thereby providing the most suitable and thinnest friction material for brakes and clutches.

Special 3γ Applicant: Onoda Semen L-Co., Ltd. Same as above.
Asahi Asbestos Industries Co., Ltd. Managing Director: Teru Soga Michi (:1.
・,1

Claims (1)

[Claims] Metal fibers 5-35% by volume, inorganic fibers or organic fibers or both 10-50% by volume, organic binder 0-30%
volume%, inorganic binder 10-60 volume% and filler 10-60% by volume
Friction material consisting of 60% by volume.