JPH0783256A - Friction member - Google Patents

Abstract

PURPOSE:To let a mating member be lowered in frictional wear after high temperature thermal hysteresis by letting metallic sulfide and an abrasive constituent under a specified condition be included in filling agent in the friction member including fiber base material, resin binder, and filling agent. CONSTITUTION:In the friction member including fiber base material, resin binder and filling agent, the filling agent is used, which includes metallic sulfide whose Moh's hardness in an oxide type is less than 3, also includes an abrasive constituent whose Moh's hardness is equal to or more than 5, and is less than 5% by weight with respect to the whole length of the friction member. By this constitution, as metallic sulfide acting as a solid lubricant, since Moh's hardness in an oxide type is limited, even if the friction member is subjected to thermal hysteresis at high temperature such as fading, and even if metallic sulfide is oxidized so as to be changed into metallic oxide, the wear of a mating member will, never be increased remarkably. Besides, since the amount of abrasive material whose Moh's hardness is limited, is restricted, the wear of the mating member can be kept comparatively low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material used as a brake pad, a lining, a clutch facing or the like for vehicles and industrial machines, and more particularly to a friction material for reducing wear of a mating material. .

[0002]

2. Description of the Related Art Friction materials such as brake pads and linings used for vehicle disc brakes, drum brakes, etc. are heated to stop the rotation of disc rotors and brake drums and convert kinetic energy into heat energy. . Therefore, such a friction material is required to have heat resistance and wear resistance, and stable friction characteristics with a small change in friction coefficient. Therefore, in order to satisfy these various characteristics, the friction material is configured as a composite material made of many materials. That is, the friction material is composed of, in addition to the fiber base material and the resin binder, various additive materials that are dispersed and filled in the matrix of these fibers and the binder. As the additive material, solid lubricants, abrasives (abrasives), etc. are used in addition to body fillers such as barium sulfate and calcium carbonate, organic powders such as cashew dust. (Note that these additive materials are collectively referred to as a filler in the present specification.) Here, the solid lubricant improves the wear resistance of the friction material and secures the thermal stability of the friction coefficient. In general, a carbonaceous material such as graphite or coke and molybdenum disulfide, which is a metal sulfide, are used in combination. The carbonaceous material such as graphite mainly functions in a low and medium temperature range, and the metal sulfide molybdenum disulfide mainly functions in a high temperature range. Also,
The abrasive agent is generally made of a hard powder having a Mohs hardness of 5 or more, such as alumina and silica, and is used for increasing the friction coefficient by the grinding action of the hard powder. However, on the contrary, the addition of the abrasive agent also causes wear of the disc rotor, the brake drum and the like which are mating materials.

By the way, as for the fiber base material, recently, a friction material containing no asbestos has been used as the fiber base material. One of them is a so-called semi-metallic friction material in which steel fiber is used as the fiber base material instead of asbestos. However, this semi-metallic friction material causes a large amount of wear of the mating material due to the high hardness of steel, resulting in frequent problems of brake judder (vibration). For this reason, recently, fibers other than steel fibers, such as aramid fibers, have been mainly used as the fiber base material, and friction materials (low steel type, non-steel type friction materials) containing no or no steel fibers more than necessary. ) Has been developed. In such a friction material, the amount of the abrasive agent added is minimized.

[0004]

However, a low steel system containing a relatively small amount of such an abrasive,
Even if a non-steel type friction material is used, it is often found that the mating material still has large wear. The large wear of the mating member causes uneven wear and causes brake judder (vibration).

Therefore, the present inventor has investigated the cause of this problem and found that such wear does not occur similarly in the same brake using the same friction material, but is related to the use conditions thereof. In particular, it was found that it occurs after being subjected to a high temperature heat history due to a fade or the like.
When this point was further investigated, molybdenum disulfide, which was the above-mentioned metal sulfide added as a filler to the friction material, was oxidized to molybdenum oxide under high heat conditions such as fading, and its hardness Was significantly increased, and the large wear of the mating material was caused by the grinding action of the hard molybdenum oxide. Therefore, the present inventor, based on this knowledge, selects a metal sulfide that does not significantly increase in hardness even if the metal sulfide is oxidized and converted to a metal oxide as a large wear of the counterpart material. It has been found that by using it, it can be effectively prevented.

Therefore, it is an object of the present invention to provide a friction material capable of reducing a large amount of wear of a mating material even when it is subjected to a high temperature heat history due to a fade or the like.

[0007]

A friction material according to the present invention is a friction material containing a fiber base material, a resin binder and a filler, and the filler is a metal having a Mohs hardness of 3 or less in an oxide form. The sulfide and the Mohs hardness of 5 or more of the abrasive component is 5% by weight or less based on the total amount of the friction material.

The Mohs hardness of various main metal sulfides and oxides of the metals are shown in the table below.

[0009]

[Table 1]

As shown in this table, some metal sulfides have a significantly increased hardness when they are oxidized and converted to oxides. For example, molybdenum disulfide has a Mohs hardness of 1.5, but when it is oxidized and converted to molybdenum oxide, its Mohs hardness increases significantly to 4. The same applies to nickel sulfide, which has a Mohs hardness of 3, but when oxidized to nickel trioxide, the Mohs hardness also rises to 6. The mating material, such as a disk rotor, is generally made of steel, and the wear of the mating material sharply increases when the Mohs hardness of these oxides is 4 or more, and as the value increases. Tend to increase cumulatively.

Therefore, in the friction material of the present invention, as the metal sulfide as the solid lubricant, one having a Mohs hardness of 3 or less in the oxide form of the metal is selected and used. Although such a metal sulfide can be used alone, it is preferably used in combination with a carbonaceous material such as graphite as in the conventional case. The addition amount thereof is generally 2 to 20% by weight based on the whole friction material.

The friction material of the present invention has a Mohs hardness of 5 in order to effectively use the above-mentioned metal sulfide.
The abrasive component in the filler as described above, that is, the abrasive agent, is 5% by weight or less of the entire friction material. That is, the abrasive agent is not used, or when it is used, it is added in an amount of 5% by weight or less based on the whole friction material. Wear of the mating material tends to increase cumulatively as the amount of the abrasive agent added increases, and addition of more than 5% by weight generally causes great wear of the mating material,
This is because the effect of using the above metal sulfide is negated. Examples of the abrasive agent include alumina, silica, titania, and silicon carbide powder, which can be used alone or in combination.

The friction material of the present invention is particularly suitable as a low steel type or non-steel type friction material for a brake, but it can be a friction material of other types or applications.

The fiber base material is aramid fiber,
Organic fibers such as novoloid fibers, nylon fibers, rayon fibers, rock wool, silicate fibers, alumina fibers,
Carbon fiber, potassium titanate fiber, inorganic fiber such as slag wool, steel fiber, stainless steel fiber,
Metal fibers such as copper fibers can be used, and these can be used alone or in combination depending on the specific type or application of the friction material.

Examples of the resin binder include thermosetting resins such as phenolic resins, epoxy resins and melamine resins, and rubbers such as SBR and NBR. These can be used alone or in combination. Can be used.

Further, as the filler, in addition to the solid lubricants, abrasives, body-filling agents such as barium sulfate, organic powders such as cashew dust, various materials related to friction, etc., may be used as appropriate. Can be used. Further, the friction material of the present invention may use various additives other than the filler as required.

Then, the friction material of the present invention can be produced by blending these materials and by thermoforming into a predetermined shape or form according to a conventional method.

[0018]

In the friction material of the present invention, as the metal sulfide that is a solid lubricant, a metal sulfide having a Mohs hardness of 3 or less in an oxide form is used. Even if the metal sulfide is oxidized and converted into a metal oxide due to the heat history of, the wear of the mating material does not significantly increase. Further, since the abrasive component having a Mohs hardness of 5 or more, that is, the abrasive agent is 5% by weight or less based on the total amount of the friction material, the wear of the mating material can be kept relatively low. Therefore, due to these, even when the friction material receives a high heat history such as a fade, large wear of the mating material can be reduced.

[0019]

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples in which the invention is applied to a disc brake pad.

(Production of Pad and Composition of Pad) Three types of brake pads (friction materials) of Examples and three types of Comparative Examples were produced by the composition shown in FIG. The mixing ratio is% by weight.

Specifically, the pad is manufactured by using a fiber base material,
The resin binder and the filler were uniformly mixed with the composition shown in FIG. 1 by a V-type blender, and the mixture was pressurized to be preformed, and then the temperature was 160 ° C. and the pressure was 400 kg / cm ² in the mold.
This was done by thermoforming for minutes and then heat-treating for 120 minutes at a temperature of 250 ° C.

As shown in FIG. 1, common to Examples 1 to 3 and Comparative Examples 1 to 3, the fiber base material was 5% by weight of aramid fiber (aromatic polyamide fiber) and 6% by weight of copper fiber. , And 6% by weight of rock wool. This aramid fiber is specifically Kevlar fiber (manufactured by DuPont). As the resin binder, 10% by weight of phenol resin was used. Then, as a filler, 5% by weight of graphite, 8% by weight of cashew dust, 3% by weight of silica, 52% by weight of barium sulfate, and 5% by weight of various metal sulfides were blended. However, in Comparative Example 3, the content of silica was increased to 6% by weight, and the content of barium sulfate was reduced to 49% by weight.

Here, as the metal sulfide, in Example 1, zinc sulfide (Mohs hardness 3 of zinc oxide), Example 2
Is lead sulfide (lead oxide Mohs hardness 1), and in Example 3 antimony trisulfide (antimony trioxide Mohs hardness 3).
In Comparative Example 1, molybdenum disulfide (molybdenum oxide has a Mohs hardness of 4), Comparative Example 2 has nickel sulfide (Nickel trioxide has a Mohs hardness of 6), and Comparative Example 3 includes Example 1.
Zinc sulfide, respectively, was used. (For Mohs hardness, refer to the above-mentioned Table 1) (Braking test) A braking test was conducted on the disc brake pads of the examples and comparative examples obtained by these blends, and the wear of the steel disc rotor, which is the counterpart material, The quantity was measured.

The caliper model of the brake used is PD5
The rotor is 1-18V, the rotor is a ventilated type with a thickness of 18 mm, and the inertia is 3.5 kg fms ² . The braking test was performed before and after the fade test, and the amount of wear of the rotor after the braking test was measured.
The fade test was carried out by repeating the first fade and the second fade once, according to JASO-C406-82. In addition, the braking test, before and after the fade test,
It carried out on the following conditions.

Initial speed: 100 km / h Deceleration: 0.1 G Temperature: 50 ° C. Number of braking times: 2000 times The amount of wear of the rotor after this braking test is also shown in FIG.

According to this test result shown in FIG. 1, Examples 1 to 3 using a metal sulfide having a Mohs hardness of 3 or less in the oxide form as a metal sulfide were all tested after the fade test. Although the amount of rotor wear increased from that before the fade test, the amount of increase was slight and maintained at a low value before and after the fade test. On the other hand, in Comparative Examples 1 and 2 using the metal sulfide having the Mohs hardness of more than 3 in the oxide form, the rotor wear amount before the fade test was small, but after the thermal history by the fade test was received. In Fig. 2, the amount of wear of the rotor is remarkably increased. In Comparative Example 3, a relatively large amount of silica (Mohs hardness 7), which is an abrasive, was blended. In this case, although zinc sulfide was used as the metal sulfide as in Example 1, A high rotor wear amount is shown both before and after the fade test.

From these results, a metal sulfide having a Mohs hardness of 3 or less in the oxide form was used as the metal sulfide,
Further, it can be seen that the wear of the rotor can be kept low even if the friction material undergoes a heat history due to a fade or the like by relatively reducing the abrasive component in the filler.

Although the friction material of the present invention has been described mainly using the disc brake pad as an example, the present invention is not limited to this, and various types such as a lining for a drum brake or a clutch facing are provided. Can be applied to the friction material.

[0029]

As described above, the friction material of the present invention uses, as the metal sulfide that is a solid lubricant, a metal sulfide whose Mohs hardness in the oxide form is 3 or less.
Therefore, even if the friction material of the present invention undergoes a high-temperature heat history such as a fade and the metal sulfide contained therein changes to a metal oxide, the hardness thereof does not significantly increase, and therefore the mating material (rotor) Wear does not increase significantly. In addition, the friction material of the present invention contains 5% by weight or less of the abrasive agent having a Mohs hardness of 5 or more relative to the total amount of the friction material, so that the wear of the mating material can be kept relatively low.

Therefore, the friction material of the present invention can keep the wear of the mating material low throughout the entire usage period. Further, the occurrence of judder vibration due to the wear of the mating member can be advantageously reduced.

[Brief description of drawings]

FIG. 1 is a table showing compounding compositions of brake pads of Examples and Comparative Examples of the present invention and rotor wear amounts after a braking test.

Claims (1)

[Claims] 1. A friction material comprising a fiber base material, a resin binder, and a filler, wherein the filler contains a metal sulfide having a Mohs hardness of 3 or less in an oxide form, and a Mohs hardness of 5 A friction material, characterized in that the above abrasive component is 5% by weight or less based on the total amount of the friction material.