JPH069944A - Friction material - Google Patents

Abstract

(57) [Abstract] [Purpose] To suppress the generation of low-frequency noise while ensuring friction characteristics. [Structure] A friction material formed by molding a mixture of a base fiber, a binder, and an additive, and containing 2 to 40% by weight of scale-like inorganic substances such as mica and kaolin, and an amorphous carbonaceous material. Contains and. Both the scale-like inorganic substance and the amorphous carbonaceous substance work to suppress the occurrence of stick-slip which causes low frequency noise.

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 for brakes and clutch facings of automobiles, industrial vehicles and the like, and more particularly to a friction material having a reduced low frequency noise generation rate.

[0002]

2. Description of the Related Art Conventionally, as a friction material used for a vehicle brake pad or the like, a braking force is large and wear resistance is good, and a change in the braking force due to a change in temperature and pressure is small and stable. It is required that the material has high strength without being attacked by water or oil.

As a friction material relatively satisfying the above characteristics, a friction material composed of a fiber base material, a binder, a solid lubricant and organic or inorganic additives is generally used. In a brake device using such a brake pad as a friction material, high-frequency noise of about 5000 to 15000 Hz, which is said to be brake squeal due to vibration of a disc brake, and 100 to 1000 which is called glow noise or the like.
Noise such as low frequency noise of about Hz may occur.

[0004]

The low-frequency noise is generated because the wear component or decomposition product of the friction material adheres to the surface of the rotor as the mating material to form the adhered film, and the adhered film is formed. It is considered that this is because stick slip, that is, instantaneous variation of the friction coefficient between the friction material and the mating material is likely to occur.

As a means for suppressing such low frequency noise, a means for removing a deposited film by adding a large amount of an abrasive having high hardness can be considered. However, this method has a drawback in that friction characteristics are deteriorated, for example, the rotor as a mating material is significantly worn. It is considered that the stick-slip is more likely to occur as the static friction coefficient of the friction material is larger and the dynamic friction coefficient is smaller, that is, the difference between the static friction coefficient and the dynamic friction coefficient is larger. Therefore, by adding a scale-like (mica-like) inorganic substance,
A means for suppressing the occurrence of stick-slip by reducing the static friction coefficient of the friction material is also conceivable. However, even in this method, in order to sufficiently suppress the occurrence of stick-slip, it is necessary to increase the addition amount of the scale-like inorganic substance, and in this case, the friction characteristics such as the abrasion resistance of the friction material are deteriorated. There is.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a friction material in which generation of low frequency noise is suppressed while sufficiently ensuring friction characteristics.

[0007]

A friction material of the present invention for solving the above-mentioned problems is a friction material formed by molding a mixture of a fiber base material, a binder and an additive, and contains 2 to 40 scale-like inorganic substances.
It is characterized by containing wt% and amorphous carbonaceous matter. The friction material is formed by mixing a fiber base material with an additive and a binder and molding the mixture. Then, various additives are dispersed and held in the fiber base material and hardened by the binder to form an integrated molded body.

Examples of the fiber base material include organic fibers such as aramid fiber, nylon fiber, rayon fiber and phenol fiber, inorganic fibers such as glass fiber, silica fiber, alumina fiber, potassium titanate fiber and rock wool, and copper fiber. Metal fibers such as steel fibers can be used. These fibers may be used alone or in combination of two or more.

As the binder, a thermosetting resin such as phenol resin, melamine resin or epoxy resin can be used. Among them, alkylbenzene-modified phenol resin, elastomer-modified phenol resin, amine-modified bismaleimide resin, bismaleimide-modified phenol resin,
It is preferable to use a thermosetting resin having higher heat resistance than a straight phenol resin such as an alkylbenzene cashew-modified phenol resin, a silicone-modified phenol resin, or a boric acid-modified phenol resin. By using a thermosetting resin having excellent heat resistance as a binder,
It becomes difficult for a resin decomposition product to be generated, and it becomes difficult for an adherend film that causes stick-slip to be formed on the surface of the mating material.

Examples of the scale-like inorganic substance added as an additive include mica, kaolin, talc, vermiculite and the like. This scale-like inorganic substance reduces the static friction coefficient of the friction material and suppresses the occurrence of stick-slip. Content of scale-like inorganic material is 2% by weight of the whole friction material
If it is less than the above range, the effect of reducing the static friction coefficient of the friction material cannot be sufficiently obtained. Further, if the content of the scale-like inorganic material is more than 40% by weight of the entire friction material, the abrasion resistance of the friction material is deteriorated, which has an effect on the friction characteristics.

The above amorphous carbonaceous materials include amorphous carbon such as coke, carbon black and carbon fiber,
By adding earth graphite as an additive, it is contained in the friction material of the present invention. It should be noted that the earth graphite has a low degree of crystal growth and a large amount of amorphous carbonaceous matter. Amorphous carbon and earth-like graphite are less likely to activate the sliding surface of the mating material than graphite, which has a large degree of crystal growth, so suppress the formation of an adhered film that causes low frequency noise. You can Moreover, since amorphous carbon and earth-like graphite have substantially the same lubricity as graphite, they do not deteriorate the wear resistance of the friction material and do not affect the friction characteristics. These amorphous carbons and earth-like graphites can be used alone or in combination of two or more, and can also be used in combination with scaly graphite having an extremely small amount of amorphous carbonaceous material due to crystal growth.

The content of the amorphous carbonaceous material is preferably 0.5 to 15% by weight of the whole friction material. When the content of the amorphous carbonaceous material is less than 0.5% by weight, the effect of suppressing the formation of the adhered film cannot be sufficiently obtained. Also,
When the content of the amorphous carbonaceous material is more than 15% by weight, it is difficult to secure the friction coefficient. When coke, carbon black or carbon fiber is used in combination with scaly graphite, the amount of coke, carbon black or carbon fiber is preferably 10% by weight or more of the total carbonaceous material. If the amount of coke, carbon black or carbon fiber is less than 10% by weight of the total carbonaceous matter, the ratio of the amorphous carbonaceous matter in the carbonaceous matter is too small, and the formation of an adhered film that causes low frequency noise is sufficient. I can't hold back. Further, for the same reason, when the clay-like graphite is used in combination with the scale-like graphite, the clay-like graphite is contained in the carbonaceous material in an amount of 20
It is preferable that the content is at least wt%.

As additives, in addition to the above-mentioned scale-like inorganic substances and carbonaceous matter, cashew dust, copper powder, barium sulfate, slaked lime, rubber dust, barium sulfate, diatomaceous earth, dolomite, calcium carbonate, molybdenum disulfide, magnesium carbonate, Examples thereof include magnesium oxide, zirconium oxide, alumina and calcium silicate. In the friction material of the present invention, a predetermined amount of a mixture of the above-mentioned fiber base material, additives and binders is sufficiently uniformly mixed with a Banbury mixer, a Henschel mixer, a kneader or a V-type blender, and the mixture is put into a mold. It can be formed by filling and pressing to carry out preforming, heating and pressurizing the preformed body to cure the binder, and then forming by a usual method of heat treatment.

[0014]

The friction material of the present invention contains a specific amount of scale-like inorganic material and also contains amorphous carbonaceous material. This scale-like inorganic material reduces the static friction coefficient of the friction material,
As a result, the difference between the static friction coefficient and the dynamic friction coefficient of the friction material can be reduced, and the occurrence of stick slip can be suppressed. In addition, since amorphous carbonaceous matter is less likely to activate the sliding surface of the mating material than graphite-like material, which has a large degree of crystal growth, wear components and decomposition products of the friction material adhere to the mating material surface. It is possible to suppress the occurrence of stick-slip by suppressing the formation of a film.

As described above, in the friction material of the present invention, the occurrence of stick-slip can be suppressed by the action of both the scale-like inorganic substance and the amorphous carbonaceous material. It is not necessary to add a large amount of scale-like inorganic material in order to sufficiently suppress it. For this reason,
It is possible to effectively suppress the generation of low-frequency noise while ensuring sufficient friction characteristics.

[0016]

EXAMPLES The present invention will be specifically described below with reference to examples. In this embodiment, the present invention is applied to a brake pad. (Example 1) As shown in Table 1, 5% by weight of aramid fiber, 10% by weight of potassium titanate whisker, 10% by weight of rock wool, 8% by weight of phenol resin as a binder,
5% by weight of cashew dust, carbonaceous earth graphite (A)
A mixture having a composition of 5% by weight, 20% by weight of copper powder (average particle size 80 μm), 22% by weight of barium sulfate, 5% by weight of slaked lime, 5% by weight of mica, and 5% by weight of kaolin was uniformly mixed with a V-type blender. . As cashew dust,
+40 mesh: 12%, +60 mesh: 35%, +
100 mesh: 30%, and -100 mesh: 23
% Particle size distribution and average particle size of about 200 μm were used.

This mixture was pressed and preformed and then gold
400kg / cm at 160 ℃ in mold ²Pressure for 10 minutes
Thermoform and heat treat for 120 minutes at 250 ° C
It was used as an abrasive. (Example 2) Instead of earth-like graphite (A) as a carbonaceous material
Same as Example 1 except that coke (B) is used
Then, a friction material was obtained.

(Example 3) A friction material was obtained in the same manner as in Example 1 except that carbon black (C) was used as the carbonaceous material instead of the earth-like graphite (A). (Example 4) A friction material was obtained in the same manner as in Example 1 except that carbon fiber (D) was used as the carbonaceous material instead of the earth-like graphite (A).

(Example 5) The above-mentioned Example 1 except that 3% by weight of scaly graphite (E) and 2% by weight of coke (B) were used as the carbonaceous material in place of 5% by weight of the earth-like graphite (A). A friction material was obtained in the same manner as in. (Example 6) A friction material was obtained in the same manner as in Example 1 except that an alkylbenzene-modified phenol resin was used as the binder instead of the phenol resin.

Example 7 A friction material was obtained in the same manner as in Example 3 except that an alkylbenzene-modified phenol resin was used as the binder instead of the phenol resin. (Comparative Example) As a carbonaceous material, a friction material was obtained in the same manner as in Example 1 except that scaly graphite (E) was used instead of the earth graphite (A).

(Measurement of Low Frequency Noise Occurrence Rate) The low frequency noise occurrence rate was examined for the friction materials of Examples 1 to 7 and the comparative friction material. This is the vehicle speed: 20-100km
/ H, temperature: 40 to 250 ° C., deceleration measured at 0.1 to 0.8 G (number of low frequency noise occurrences / number of braking times) ×
It was calculated by the formula of 100. The results are shown in Table 1.

[0022]

[Table 1] Each of the friction materials of Examples 1 to 7 containing 5% by weight of mica and kaolin as scale-like inorganic substances and containing an amorphous carbonaceous material had a low noise occurrence rate of 10 to 20%. Significantly reduced compared to the one. From this, it is understood that the generation of low noise is significantly suppressed by the action of the amorphous carbonaceous material.

Further, as can be seen by comparing Example 1 with Examples 2 to 4, rather than using the clay-like graphite (A) as the carbonaceous material, coke (B), carbon black (C) or carbon fiber (D) was used. It is possible to more effectively suppress the generation of low noise by using amorphous carbon such as).
Further, as can be seen by comparing Example 1 and Example 6 and Example 3 and Example 7, it is preferable to use a thermosetting resin having excellent heat resistance such as an alkylbenzene-modified phenol resin as a binder. Therefore, the generation of low noise can be suppressed more effectively.

Claims (1)

[Claims] 1. A friction material formed by molding a mixture of a fiber base material, a binder and an additive, containing 2 to 40% by weight of a scale-like inorganic material and an amorphous carbonaceous material. Friction material characterized by