JPH069945A - 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, containing 2 to 40% by weight of scale-like inorganic substances such as mica and kaolin, and as a binder,
A thermosetting resin that has better heat resistance than straight phenol is used. Both the scaly inorganic material and the thermosetting resin having excellent heat resistance work to suppress the occurrence of stick-slip that 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 thereof 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 in that a thermosetting resin, which is contained by weight and has a higher heat resistance than a straight phenol resin, is used as the binder.

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

In the friction material of the present invention, a thermosetting resin having a higher heat resistance than straight phenol resin is used as a binder. The thermosetting resin having heat resistance superior to that of the straight phenol resin means a resin having less strength reduction due to thermal deterioration than the straight phenol resin when heated at a predetermined temperature for a predetermined time. As such a thermosetting resin having excellent heat resistance, alkylbenzene-modified phenol resin, elastomer-modified phenol resin, amine-modified bismaleimide resin, bismaleimide-modified phenol resin, alkylbenzene cashew-modified phenol resin, silicone-modified phenol resin, boric acid-modified phenol Resin etc. can be mentioned. These thermosetting resins may be used either individually or in combination of two or more.

The content of the thermosetting resin as the binder is preferably 5 to 20% by weight based on the whole friction material. If the content of the thermosetting resin is less than 5% by weight, it is difficult to secure the strength and wear resistance of the lining, and if it is more than 20% by weight, it is difficult to secure the fade resistance. Examples of the flaky 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. If the content of the scale-like inorganic material is less than 2% by weight of the entire friction material,
The effect of reducing the static friction coefficient of the friction material cannot be sufficiently obtained. In addition, the content of the scale-like inorganic material is 40% of the whole friction material.
When the content is more than the weight%, the friction characteristics are affected such that the wear resistance of the friction material is reduced.

The carbonaceous matter added as an additive is
Natural graphite such as scaly graphite and earth graphite, and amorphous carbon such as coke, carbon black, and carbon fiber can be used. Here, it is preferable to use amorphous carbon such as coke, carbon black, or carbon fiber in order to suppress the formation of an adhered film that causes low frequency noise. These amorphous carbons are less likely to activate the sliding surface of the mating material than the graphite material, which has a large degree of crystal growth, and therefore wear components and decomposition products of the friction material adhere to the mating material surface to form a film. It can suppress that it becomes a state.
Moreover, since amorphous carbon has almost the same lubricity as graphite, it does not deteriorate the wear resistance of the friction material and does not affect the friction characteristics. Even if the graphite having a small degree of crystal growth and a large amount of amorphous carbonaceous matter is used, it is possible to obtain substantially the same effect as those of the amorphous carbon. These amorphous carbons and earth-like graphite may be used alone or in combination of two or more kinds, and may be used in combination with scaly graphite having an extremely small amount of amorphous carbonaceous matter due to crystal growth.

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.

[0013]

In the friction material of the present invention, a thermosetting resin containing a specific amount of scale-like inorganic substance and having a heat resistance superior to that of the straight phenol resin is used as a binder. This scale-like inorganic material can reduce the static friction coefficient of the friction material, and as a result, reduce the difference between the static friction coefficient and the dynamic friction coefficient of the friction material and suppress the occurrence of stick slip. Further, since thermosetting resin having excellent heat resistance is less likely to generate resin decomposition products and is suppressed from adhering to the surface of the mating material to form a film, it is possible to suppress the occurrence of stick-slip. .

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 thermosetting resin having excellent heat resistance. It is not necessary to add a large amount of scale-like inorganic substances in order to sufficiently suppress the occurrence of Therefore, it is possible to effectively suppress the generation of low-frequency noise while ensuring sufficient friction characteristics.

[0015]

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 alkylbenzene-modified phenol resin (A) as a binder, and cashew dust 5 weight%,
5% by weight of scaly graphite as carbonaceous material, copper powder (average particle size 80
μm) 20% by weight, barium sulfate 22% by weight, slaked lime 5
A mixture having a composition of wt%, mica 5 wt% and kaolin 5 wt% was uniformly mixed with a V-type blender. As cashew dust, +40 mesh: 12%, +60
Mesh: 35%, +100 mesh: 30%, and-
100 mesh: A particle having a particle size distribution of 23% and a central particle diameter of about 200 μm was used.

This mixture is pressed to preform 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) As a binder, an alkylbenzene-modified phenol
Elastomer-modified pheno instead of knoll resin (A)
In the same manner as in Example 1 except that the resin (B) is used.
Then, a friction material was obtained.

Example 3 As a binder, 4% by weight of a straight phenol resin (D) and 4% by weight of an amine-modified bismaleimide (C) were used instead of 8% by weight of an alkylbenzene-modified phenol resin (A). A friction material was obtained in the same manner as in Example 1 above. Example 4 A friction material was obtained in the same manner as in Example 1 except that earth graphite was used as the carbonaceous material instead of scaly graphite.

Example 5 A friction material was obtained in the same manner as in Example 1 except that carbon black was used instead of scaly graphite as the carbonaceous material. (Comparative Example) A friction material was obtained in the same manner as in Example 1 except that the straight phenol resin (D) was used as the binder instead of the alkylbenzene-modified phenol resin (A).

(Measurement of Low Frequency Noise Occurrence Rate) The low frequency noise occurrence rate was examined for the friction materials of Examples 1 to 5 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.

[0020]

[Table 1] The friction materials of Examples 1 to 5 each containing 5% by weight of mica and kaolin as scale-like inorganic substances and using a thermosetting resin having excellent heat resistance as a binder all had a low frequency noise occurrence rate of 10%. It was up to 25%, which was a significant reduction compared to the comparative example. From this, it can be seen that the use of a thermosetting resin having excellent heat resistance can significantly suppress the generation of low frequency noise.

Further, as can be seen by comparing Examples 1 and 4 and 5, amorphous carbon such as earth graphite, coke, carbon black and carbon fiber is used rather than scaly graphite as the carbonaceous material. In this way, the generation of low frequency noise can be suppressed more effectively. (Evaluation of Heat Resistance of Thermosetting Resin) The alkylbenzene-modified phenol resin (A) used in Example 1 above, the amine-modified bismaleimide resin (C) used in Example 3 above,
Heat resistance was evaluated for other thermosetting resins having excellent heat resistance, that is, silicone-modified phenol resin, straight phenol resin used in Comparative Examples, and acrylic rubber-modified phenol resin.

A mixture having the composition of 10% by weight of each resin, 10% by weight of glass fiber, 5% by weight of aramid fiber, 10% by weight of graphite, and 65% by weight of barium sulfate was uniformly mixed with a V-type blender. This mixture was pressurized and preformed, then 200 kg / cm ² at 160 ° C. in a mold.
Each sample was thermoformed at a pressure of 10 minutes and heat treated at 200 ° C. for 5 hours.

The bending strength at room temperature and the bending strength after heating at 350 ° C. for 1 hour, 2 hours, 4 hours, and 8 hours were measured for each of the above test materials. The results are shown in Table 2. In Table 2, the numerical value in parentheses indicates the strength after each heating time when the strength at room temperature is 100.

[0024]

[Table 2] As is clear from Table 2, the alkylbenzene-modified phenol resin, the amine-modified bismaleimide resin, and the silicone-modified phenol resin have a significantly smaller decrease in strength after heating with respect to room temperature strength, as compared with the straight phenol resin and the acrylic rubber-modified phenol resin. .

The alkylbenzene-modified phenol resin, amine-modified bismaleimide resin and silicone-modified phenol resin have strengths after heating at 350 ° C. for 4 hours.
It is 30 or more when the strength at room temperature is 100, and these thermosetting resins can be preferably used in the present invention.

Claims (1)

[Claims] 1. A friction material formed by molding a mixture of a fibrous base material, a binder and an additive, which contains 2 to 40% by weight of a scale-like inorganic material, and the binder has a higher heat resistance than a straight phenol resin. A friction material characterized by using a thermosetting resin having excellent properties.