JP7245604B2 - friction material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a friction material capable of achieving high performance and suppressing brake squeal.

Friction materials for brakes of bar-handle vehicles such as motorcycles and tricycles are required to have a high friction coefficient, stable friction characteristics, heat resistance, wear resistance, and reduction in brake squeal.
For example, in Patent Documents 1 to 4, friction materials using inorganic fibers and biosoluble inorganic fibers have little impact on the environment, have stable effects, improve rust removal properties, and reduce brake squeal. disclosed.

That is, Patent Document 1 discloses a friction material containing a biosoluble inorganic fiber having a Mohs hardness of 5 or more and 7 or less.
Patent Document 2 discloses a friction material containing a titanate compound and a biosoluble inorganic fiber.
Patent Document 3 discloses a friction material containing 10 to 45% by mass of a biosoluble inorganic fiber having a Mohs hardness of 6 or more based on the total friction material.
Further, Patent Document 4 discloses a friction material containing inorganic fibers having a Mohs hardness of less than 4.5.

JP 2016-132702 JP 2013-76058 Japanese Patent No. 5469805 JP 2002-275452

The biosoluble inorganic fiber has excellent efficacy stability as a friction material for brakes, and is highly suppressive of brake squeal.
However, as a result of examination by the inventor, as shown in Patent Document 3, there is a problem that if a large amount of biosoluble inorganic fiber is used, brake squeal cannot be satisfactorily suppressed during deceleration.

The friction material according to the present embodiment has been made to solve the above problems, and its object is to provide a friction material that further reduces brake squeal.

The friction material according to the present embodiment is a friction material containing an organic material containing a carbon element and inorganic fibers, wherein the total content of the organic material is 30% by mass or less of the entire friction material composition, and the The inorganic fibers include biosoluble inorganic fibers and glass fibers that are inorganic fibers with a Mohs hardness of 5 or more and 7 or less, inorganic fibers with a Mohs hardness of 5 or less, and do not contain hard inorganic powder materials with a Mohs hardness of 8 or more. The biosoluble inorganic fiber is contained in an amount of 0.5 to 5.0% by mass of the entire friction material composition, the glass fiber is contained in an amount of 3.0 to 15.0% by mass of the entire friction material composition, and 2.0 to 12.0% by mass of the total friction material composition contains inorganic fibers having a Mohs hardness of 5 or less, the organic material contains aramid fibers, rubber powder, and resin, and the biosoluble inorganic fibers are In the bulk fiber, the inorganic fiber having a Mohs hardness of 5 or less is potassium titanate, which is a plate-like fiber.

Further , the friction material according to the present embodiment can be suitably used for shoe linings for drum brakes.

According to claim 1, as inorganic fibers, biosoluble inorganic fibers and glass fibers having a Mohs hardness of 5 or more and 7 or less, and inorganic fibers having a Mohs hardness of 5 or less are added, and a hard inorganic powder material having a Mohs hardness of 8 or more is added. By not including inorganic fibers having different hardnesses, brake squeal can be reduced. Moreover, the morning effect phenomenon can be prevented by containing the glass fiber.
In addition , instead of reducing the content of the biosoluble inorganic fiber, by containing the inorganic fiber having a Mohs hardness of 5 or less, it is possible to suppress brake squeal during deceleration. Moreover, even when the friction surface is wet due to rain or the like, the reduction in effectiveness can be suppressed.
As shown in claim 2 , it can be suitably used for drum brakes that require high efficacy over a long period of time.

4 is a table showing blending ratios of various raw materials and various brake characteristics in Examples 1 to 5 and Comparative Examples 1 to 8. FIG. 4 is a graph showing changes in friction coefficient with respect to the number of braking operations when using the shoe linings of Example 1 and Comparative Example 1. FIG. 1 is a graph showing measurement of water recoverability (effectiveness change rate) when shoe linings of Example 1 and Comparative Example 1 are used.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.
As an example, the friction material according to the present embodiment is used for a shoe lining of a drum brake. As described above, the friction material according to the present embodiment is a friction material containing an organic material containing a carbon element and inorganic fibers, wherein the total content of the organic material is 30 mass of the entire friction material composition. % or less, the inorganic fibers include biosoluble inorganic fibers and glass fibers that are inorganic fibers with a Mohs hardness of 5 or more and 7 or less, and inorganic fibers with a Mohs hardness of 5 or less, and hard inorganic fibers with a Mohs hardness of 8 or more It is characterized by not containing powder material.
Also, of course, common base materials include inorganic powder materials such as calcium carbonate. Moreover, metal materials, such as aluminum powder, may also be included.

Organic fibers such as aramid fibers, resins such as phenol resins, and rubber powders (NBR, SBR, etc.) can be used as organic materials containing carbon elements. Further, it may contain a lubricant such as graphite and a friction modifier such as cashew dust.
The total content of organic materials including these carbon materials should be 30 mass % or less of the entire friction material composition. As a result, the amount of carbon components transferred to the mating drum sliding surface can be suppressed, and a stable braking effect can be obtained. If the content of the organic material containing carbon fiber exceeds 30% by mass, the transfer amount to the drum sliding surface becomes too large, the coefficient of friction fluctuates, and stable efficacy cannot be obtained.

As described above, the friction material in the present embodiment includes, as inorganic fibers, biosoluble inorganic fibers and glass fibers, which are inorganic fibers having a Mohs hardness of 5 or more and 7 or less, and three types of inorganic fibers having a Mohs hardness of 5 or less. Contains fiber.
Inorganic fibers having a Mohs hardness of 5 or more and 7 or less are of two types: biosoluble inorganic fibers and glass fibers.

The biosoluble inorganic fibers are not particularly limited, but artificial bulk fibers can be preferably used. The bulk fiber has a component system of SiO ₂ --CaO--MgO, has a Mohs hardness of 5 or more and 7 or less, and has a heat resistance of 1000° C. or more.
Since the biosoluble inorganic fiber dissolves in the living body, it has little effect on the living body, is excellent in efficacy stability as a brake friction material, and is less likely to cause brake squeal among inorganic fibers.

However, as described above, when a large amount of biosoluble inorganic fiber is used, there arises a problem that brake squeal cannot be satisfactorily suppressed during deceleration.
Therefore, in the present embodiment, the content of the biosoluble inorganic fiber is reduced from that of the conventional one, and the content is preferably 0.5 to 5.0% by mass based on the total friction material composition. As a result, it was possible to reduce the brake squeal at the time of deceleration. The effect of reducing brake squeal and the effect of improving water recovery characteristics (including the effect of reducing the morning effect phenomenon) can be obtained by using the above three types of inorganic fibers in combination as inorganic fibers. obtained by

The content of biosoluble inorganic fibers with a Mohs hardness of 5 or more and 7 or less is reduced more than before, and glass fibers with a Mohs hardness of 5 or more and 7 or less (artificial glass fibers, etc.) are used in combination. The content of the glass fiber is preferably 3.0 to 15.0% of the total friction material composition in consideration of the content of the biosoluble inorganic fiber. As described above, the morning effect phenomenon can be reduced by reducing the content of the biosoluble inorganic fibers having a Mohs hardness of 5 or more and 7 or less than in the past and adding glass fibers.

As described above, the friction material according to the present embodiment includes inorganic fibers having a Mohs hardness of 5 or less as inorganic fibers. The content of inorganic fibers having a Mohs hardness of 5 or less is preferably 2.0 to 12.0 mass % of the total friction material composition.
Plate-like or whisker-like potassium titanate can be preferably used as the inorganic fiber having a Mohs hardness of 5 or less. Inorganic fibers such as magnesium titanate, lithium titanate, sodium titanate, magnesium sulfate, and calcium carbonate can also be used.

By using the above three types of inorganic fibers in combination, the inorganic fibers are easily entangled with each other and arranged in a mesh shape in the friction material. Friction materials used for brakes may form a water film due to water vapor condensed in the air, rainwater, and the like. When a water film is formed, the coefficient of friction increases and a phenomenon of increased efficacy may occur (such as the morning effect phenomenon).

In the friction material according to the present embodiment, the above three types of inorganic fibers are entangled to form a mesh, forming fine voids, thereby releasing moisture and cutting off the water film. This can prevent the morning effect phenomenon. In addition, since the attached rainwater enters between the mesh-like fibers and easily evaporates when the brake is not applied, the water recovery property is also improved.

Moreover, in the present embodiment, inorganic fibers having a Mohs hardness of 5 or less and inorganic fibers having a Mohs hardness of 5 or more and 7 or less are mixed in a well-balanced manner. In this way, since the low-hardness portion and the high-hardness portion alternately exist on the surface of the friction material, the aggression to the drum sliding surface becomes moderate, thereby reducing brake squeal at low speeds. it is conceivable that.

The raw materials of the compounding ratio shown in the table of FIG. 1 were stirred and mixed to form a temporary molding. The temporarily molded friction materials were placed in a molding die, and pressurized and heat-molded by a known method to manufacture the friction materials of Examples 1-5 and Comparative Examples 1-8.
The friction materials of Examples 1 to 5 and the friction materials of Comparative Examples 1 to 8 were investigated with respect to their respective characteristics of efficacy stability (braking force and its stability), water recovery, morning effect phenomenon, and brake squeal. It is shown in the lower part of the table in FIG.

As shown in the table of FIG. 1, each of the friction materials of Examples 1 to 5 according to the present embodiment is effective in stability of efficacy (braking force and its stability), water recovery, and suppression of the morning effect phenomenon. In addition, brake squeal (especially brake squeal at low speed) could be suppressed satisfactorily.

Comparative Examples 1, 6, and 7 do not contain biosoluble inorganic fibers, and are inferior in efficacy stability and water recoverability.
The shoe lining of Comparative Example 2 did not contain biosoluble inorganic fibers, and used a relatively large amount of inorganic fibers made of potassium titanate forming plate-like fibers. The recovery performance was poor, and brake squeal could not be suppressed satisfactorily.
Comparative Example 3 shows an example in which a biosoluble inorganic fiber is used, but brake squeal cannot be suppressed when artificial slag wool is used as the inorganic fiber. In Comparative Example 4, although biosoluble inorganic fibers were used, when particulate potassium titanate was used as the inorganic fibers having a Mohs hardness of 5 or less, the water recovery property was not very good. there is As shown in Examples 1 to 5, inorganic fibers of potassium titanate in the form of plate-like fibers (flat in cross section) were excellent as inorganic fibers having a Mohs hardness of 5 or less.
Comparative Example 5 uses a larger amount of biosoluble inorganic fibers than those of Examples 2 and 4, and does not contain glass fiber, so brake squeal and morning effect phenomenon are inferior.
Comparative Example 8 had the same glass fiber content as that of Examples 1-5, but used a larger amount of biosoluble inorganic fiber than Examples 2 and 4, and thus brake squeal could not be suppressed. shows an example.

FIG. 2 is a graph showing changes in friction coefficient with respect to the number of braking operations using the shoe linings of Example 1 and Comparative Example 1. In FIG. As shown in FIG. 2, it can be seen that the shoe lining of Example 1 is excellent in efficacy stability with little change in efficacy even when the number of times of braking increases. On the other hand, it can be seen that the effectiveness of the shoe lining shown in Comparative Example 1 decreases as the number of times of braking increases.

FIG. 3 is a graph showing water recoverability (efficacy change rate) measured using the shoe linings of Example 1 and Comparative Example 1. FIG.
3 that the shoe lining of Example 1 has a smaller rate of change in efficacy (reduction rate from 100%) in the early stage of braking than the shoe lining of Comparative Example 1, and is superior in water recovery.

Claims (2)

In a friction material containing an organic material containing a carbon element and an inorganic fiber,
The total content of the organic material is 30% by mass or less of the entire friction material composition,
As the inorganic fiber,
biosoluble inorganic fibers and glass fibers, which are inorganic fibers having a Mohs hardness of 5 or more and 7 or less;
Inorganic fibers with a Mohs hardness of 5 or less,
Does not contain a hard inorganic powder material with a Mohs hardness of 8 or more,
0.5 to 5.0% by mass of the entire friction material composition containing the biosoluble inorganic fiber,
Containing 3.0 to 15.0% by mass of the glass fiber in the entire friction material composition,
2.0 to 12.0% by mass of the total friction material composition containing inorganic fibers having a Mohs hardness of 5 or less,
The organic material contains aramid fiber, rubber powder, resin,
The biosoluble inorganic fibers are bulk fibers,
The friction material, wherein the inorganic fiber having a Mohs hardness of 5 or less is a plate-like fiber of potassium titanate. The friction material according to claim 1,
A friction material characterized by being used for a shoe lining for a drum brake.

Images