JPH11302632A - Friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction material adapted so that it may contain an organic fiber in an amount larger than that in a conventional friction material when it contains a pulpy organic fiber such as an aramid pulp as an organic fiber and therefore improved in cracking resistance and abrasion resistance. SOLUTION: There is provided a friction material containing a fibrous base, a binder, and a friction modifier, wherein the fibrous base is a pulpy organic fiber having a fiber length short enough to correspond to an average fiber length of 1.4 mm or below. The pulpy organic fiber can be used in conjunction with a pulpy organic fiber having a longer average fiber length. It is suitable that the pulpy organic fiber constitutes 4-26 vol.% of the entire friction material. It is desirable that the pulpy organic fiber is an aramid fiber.

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 a brake such as a disc brake or a drum brake, or a clutch, and more particularly to a friction material having improved wear resistance in a temperature range of 200 ° C. or less.

[0002]

2. Description of the Related Art Friction materials used for brakes such as disc brakes and drum brakes, clutches and the like are provided with a friction effect and a friction adjusting material for adjusting the friction performance, and a fiber base material for a reinforcing effect. And a material such as a binding material that gives strength by integrating the above substances. Among them, there are various types of fiber base materials such as metal fiber, inorganic fiber, organic fiber, etc., each of which has characteristics, and one type cannot satisfy all the requirements, so usually two or more types are combined. Has been used.

For example, organic fibers, inorganic fibers, metal fibers,
A friction material comprising a filler, a binder and the like is known (JP-A-4-234479). Various materials are known for organic fibers. Among them, organic fibers have characteristics such as good binding property with a binder,
The wear resistance in a temperature range of 0 ° C. or less is improved. Aramid pulp is the most representative type of organic fiber.

[0004]

However, when aramid pulp is used as an organic fiber, if it is used in a large amount, it cannot be defibrated in the stirring step and becomes a lump, the aramid pulp is not uniformly dispersed, and the strength is insufficient. As a result, cracks occur in the friction material and the wear resistance deteriorates. Therefore, the amount of aramid pulp used in the conventional friction material is 8 vol.
1% was the limit. An object of the present invention is to provide a friction material having improved performance when a pulp-like organic fiber such as aramid pulp is used as the organic fiber in the friction material. Further, the present invention, when using a pulp-like organic fiber such as aramid pulp as the organic fiber in the friction material, it is possible to use a larger amount of organic fiber in the friction material than conventionally used, It is intended to provide a friction material with further improved performance.

[0005]

The present invention has solved the above-mentioned problems by the following means. (1) A friction material comprising a fiber base material, a binder, and a friction modifier, wherein a pulp-like organic fiber having a short fiber length and an average fiber length of 1.4 mm or less is used as the fiber base material. Wood. (2) The friction material according to (1), wherein a pulp-like organic fiber having a long average fiber length is used together with the pulp-like organic fiber having a short average fiber length. (3) The pulp-like organic fiber is 4 to 26 v of the entire friction material.
(1) or (2) above,
The friction material according to the above. (4) The friction material according to any one of (1) to (3), wherein the pulp-like organic fiber is an aramid fiber.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is characterized in that pulp-like organic fibers having an average fiber length of 1.4 mm or less and having a short fiber length are used as the organic fibers used for the fiber base material. That is, conventionally, when a pulp-like organic fiber is used as an organic fiber as a fiber base material in a friction material, the average fiber length of the pulp-like organic fiber is 1.6 to 2.4 m.
m has been used, but this one has poor dispersibility and poor defibration state. In contrast, in the present invention, pulp-like organic fibers having an average fiber length of 1.4 mm or less are used, preferably 0.7 to 1.2 mm, and particularly preferably about 0.9 mm. When the pulp-like organic fiber having a short fiber length is used as the organic fiber as described above, the dispersibility is improved, so that the amount of the organic fiber contained in the friction material can be increased, and the amount of the organic fiber can be increased. Up to 26 vol%, preferably up to 18 vol% of the friction material can be added. The lower limit is good enough to produce the effect of the addition of the organic fiber, but in specific numbers, for example, 4 vol% can be contained.

[0007] That is, pulp-like aramid fibers ("aramid pulp") are generally used as organic fibers in the past, but since the pulp-like fibers have a strong entanglement property, the defibrated state is as described above. Although not good, when using a pulp-like organic fiber having a short fiber length as described above, the property of entanglement is weak because of the form of the fiber,
There is almost no entanglement between fibers,
In the present invention, when this pulp-like organic fiber having a short fiber length is used, the dispersion of the organic fiber is good and the defibration state is excellent. Further, a pulp-like organic fiber having a long average fiber length (1.6 to 2.4 mm) can be used in combination with the pulp-like organic fiber having a short fiber length.

[0008] As a specific composition of the friction material, as a fiber base material, the ceramic fiber content is 0 to 20 vol%, preferably 3 to 10 vol%. No metal fibers
10 to 10 vol%, preferably 2 to 5 vol%. The amount of the friction modifier is 55 to 30 vol%, preferably 52 to 34 vol%. Lubricant 5-20vol
%, Preferably 8 to 15 vol%.

In the manufacturing process of a disc pad for a disc brake, a back metal formed into a predetermined shape by a sheet metal press, subjected to a degreasing treatment and a primer treatment, and coated with an adhesive, is composed of an organic fiber, an inorganic fiber, and a metal. A fiber base material such as fiber, and a powder raw material such as an inorganic / organic filler, a friction modifier and a thermosetting resin binder are blended, and the raw material sufficiently homogenized by stirring is formed at room temperature under a predetermined pressure ( And a preforming body produced by preforming), in a thermoforming step, thermoforming at a predetermined temperature and pressure to fix both members together, perform after-curing, and finally perform a finishing treatment.

The above-mentioned organic fibers include aramid fibers and acrylic fibers, and the inorganic fibers include ceramic fibers such as potassium titanate fibers and alumina fibers, glass fibers, carbon fibers, rock wool, and the like. Examples of the metal fiber include a copper fiber and a steel fiber. Examples of the inorganic filler include scaly inorganic substances such as balm curite and mica, and particles such as barium sulfate and calcium carbonate. Examples of the organic filler include synthetic rubber and cashew resin. Examples of the thermosetting resin binder include a phenol resin (including various modified phenol resins such as straight phenol resin and rubber), a melamine resin, a polyimide resin, and a BT resin. Examples of the friction adjusting material include metal oxides such as alumina and silica, magnesia, zirconia, chromium oxide, and quartz. Examples of the solid lubricant include graphite and molybdenum disulfide.

[0011]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Ceramic fiber, copper fiber, aramid fiber, friction modifier,
As shown in Table 1, the raw materials of the lubricant and the phenolic resin were blended in four ratios of "Basic Formula 1" to "Basic Formula 4", mixed by stirring, preformed and preformed. Was prepared. In these four basic blends, the blend ratio of the aramid fibers is made to increase sequentially. Further, in making these four basic blends, the properties of the aramid fibers blended therein, as shown in Table 2,
The volume ratio between the aramid pulp having a long average fiber length and the aramid pulp having a short average fiber length is 100/0 (conventional product), 50/50 and 0 /.
Three hundred kinds of friction materials were prepared, and these were used for individual basic formulations to produce 12 kinds of friction materials.

On the other hand, a back metal is formed by a sheet metal press, degreased, treated with a primer, an adhesive is applied thereto, the preform is placed on the applied surface, and press forming and heating are performed for thermoforming. The thermoformed product was sent to a finishing step to produce a disc brake pad.

[0014]

[Table 1]

[0015]

[Table 2]

(Performance Test) Dispersibility test The raw materials of the basic composition were stirred and mixed, and the dispersibility of the aramid pulp of the stirred material was visually evaluated. The evaluation criteria are shown in Table 3. 2. Abrasion test With respect to the produced disc brake pad, the pad abrasion rate at 200 ° C. was measured using a dynamometer under the specifications of a Japanese automobile standard abrasion test passenger car. 3. Crack test 1) Pads were placed in a furnace at an ambient temperature of 400 ° C. and held for 30 seconds. 2) After taking out from the furnace, it was immediately kept in water for 30 minutes. 3) The above 1) and 2) are defined as one cycle, and this is repeated for five cycles. 4) The cracking property after 5 cycles was evaluated. The evaluation criteria are shown in Table 3. (Test Results) The test results of the above 1 to 3 are as shown in Table 2.

[0017]

[Table 3]

[0018]

According to the friction material of the present invention, the dispersibility is improved by using pulp-like organic fibers having a short average fiber length even when used in a large amount, so that the wear resistance and crack resistance are improved. You. Further, the pulp-like organic fiber having a short average fiber length exhibits its effect sufficiently even when used in combination with a conventional pulp-like organic fiber having a long average fiber length. The friction material of the present invention has improved wear resistance particularly in a temperature range of 200 ° C. or lower.

Claims (4)

[Claims] 1. A friction material comprising a fiber base material, a binder and a friction modifier, wherein the fiber base material has an average fiber length of 1.4.
A pulp-like organic fiber having a short fiber length of not more than mm is used. 2. The friction material according to claim 1, wherein a pulp-like organic fiber having a long average fiber length is used together with the pulp-like organic fiber having a short average fiber length. 3. The pulp-like organic fiber according to claim 1, wherein
The friction material according to claim 1 or 2, wherein the friction material is contained in an amount of up to 26 vol%. 4. The friction material according to claim 1, wherein the pulp-like organic fibers are aramid fibers.