JPH08120095A - Friction material for brake and its preparation - Google Patents

Abstract

PURPOSE: To obtain a friction material for a brake which has excellent fundamental properties as a frictional material, such as mechanical properties and braking properties, and, at the same time, is less likely to squeak during braking by dispersing a particular porous particulate molding in a friction material. CONSTITUTION: A friction material for a brake is prepd. by molding a mixture of a fibrous material with a friction regulator using a thermosetting synthetic resin as a binder. A refined ceramic fiber having a fiber length of 5 to 70μm and an average fiber length of 50 to 150μm and a filler are molded, as a part of the friction regulator, using the binder. The porous particulate molding having an average particle diameter of 0.1 to 5mm and a bulk density of 0.2 to 2.0g/cm<3> is dispersed in the friction material while keeping the porosity. This friction material is prepd. by thermoforming under pressure. The ceramic fiber is most pref. an aluminosilicate fiber. Fillers usable herein include barium sulfate, clastonite, cashew dust, and carbon powder. The binder may be a sol binder, an org. binder or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material in a braking device for various vehicles and industrial machines and a method for manufacturing the friction material.

[0002]

2. Description of the Related Art Conventionally, various friction materials have been used as a friction material constituting a braking device used in automobiles and other vehicles and industrial machines. Generally, inorganic materials such as asbestos and ceramic fibers are used. Fibers, heat-resistant organic fibers, metal fibers and other fibrous materials are used as a base material, and a mixture of these materials with friction modifiers and other additives is used as a thermosetting material such as phenol resin. It is a product obtained by thermocompression molding using a synthetic resin as a binder.

In addition to the friction coefficient and its temperature characteristics, which are directly related to braking ability, friction materials include wear resistance, mechanical strength, aggressiveness to mating metal materials, and "squeal" during braking.
Many characteristics such as the above become problems depending on the application, but these characteristics are adjusted by devising a combination of the above-mentioned molding materials.

Regarding the prevention of squeal during braking, it is known that fine pores should be introduced into the friction material. As an effective means therefor, a method of reducing the amount of binder used, a fiber of the base material There have been proposed methods such as using long fibers as a quality material, blending a porous material such as vermiculite, and reducing a filling amount of the material during molding.

However, these conventional methods for preventing squeal have a problem that the strength and wear resistance of the friction material are significantly reduced. Further, since a porous material such as vermiculite has low heat resistance, there is a problem in that when it is filled, the characteristics of the friction material at high temperatures, particularly the wear resistance, deteriorates.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved friction material having excellent basic properties required for a friction material, such as mechanical strength and braking characteristics, and having less squeal during braking, and a method for producing the same. To provide.

[0007]

DISCLOSURE OF THE INVENTION The friction material for a braking device provided by the present invention is a friction material for a braking device in which a mixture of a fibrous material and a friction modifier is molded using a thermosetting synthetic resin as a binder. In, as part of the friction modifier,
Fiber length 5 to 700 μm, average fiber length 50 to 150 μm, finely divided ceramic fibers and filler are molded using a binder, average particle diameter 0.1 to 5 mm, bulk density 0.2 to
It is characterized in that 2.0 g / cm ³ of the porous granular molding is dispersed in the friction material while maintaining its porosity.

The present invention also provides a method for producing the above friction material, that is, a fiber length of 5 to 700 μm and an average fiber length of 50 to 15
Rubbing a porous granular molded product having an average particle size of 0.1 to 5 mm and a bulk density of 0.2 to 2.0 g / cm ³ which is obtained by molding 0 μm finely divided ceramic fibers and a filler using a binder. It is intended to provide a method for manufacturing a friction material for a braking device, which is characterized in that the friction material manufacturing raw materials blended as a part of the adjusting material are mixed and hot pressed.

In the friction material according to the present invention, each of the above-mentioned porous granular moldings dispersed in the friction material while maintaining the porosity is unevenly distributed at a high density in the range of about 0.1 to 5 mm in diameter. A group of fine pores is introduced. As a result, a large number of fine pores scattered in the friction material prevent the friction material from squeaking, but since it is supported by the fine ceramic fibers, it does not adversely affect the strength and braking characteristics of the friction material.

The method of manufacturing the friction material according to the present invention will be described in detail below. In order to manufacture the friction material of the present invention, a porous granular molded product made of finely divided ceramic fibers and a filler is used as a kind of friction modifier, and a method of manufacturing this material will be described first.

The starting ceramic fiber is not particularly limited, but the aluminosilicate fiber is most preferable because it is inexpensive and easily available, is preferable in physical properties, and is easily granulated. Other suitable ceramic fibers include rock wool, alumina fibers, carbon fibers and the like.
In addition, although ceramic fibers which are usually easily available have a length of several millimeters or more, it is necessary to use a wet or dry pulverizer to refine the ceramic fibers into a suitable length for producing the above-mentioned granular molded product. Just process it.

As the filler, barium sulfate, wollastonite, cashew dust, carbon powder, etc. can be used, and the friction characteristics of the friction material can be adjusted by selecting the type and blending ratio of these fillers. it can.

A binder is used in addition to the ceramic fiber and the filler, and preferred specific examples thereof include sol binders such as colloidal silica and colloidal alumina; ethyl silicate; organic binders such as polyvinyl alcohol and CMC. . These may be used in combination of two or more.

The above-mentioned raw materials are preferably 1 to 300 parts by weight of filler (particularly preferably 50 to 200 parts by weight) and inorganic binders 1 to 40 with respect to 100 parts by weight of ceramic fiber.
The mixture is mixed at a ratio of 5 parts by weight (as solid content) and 5 parts by weight or less of the organic binder, and the mixture is put in a well-known stirring type granulator used for granulating powder and stirred.

[0015] Usually, the raw material fibers are compressed in a package to form lumps of various sizes. When this is stirred in a granulator, the lumps are crushed and the single fibers are reassembled to form aggregates having uniform particle sizes. In this process, the filler adheres to the fiber surface by the binder. The assembled ceramic fibers are initially in a loose engagement state, but the packing density gradually increases due to the compressive stress associated with stirring. Then, when the stirring is further continued, the packing density measured in the form of the bulk density does not change so much, but a more stable aggregated state is obtained. Therefore, the stirring granulation is terminated, and the mixture is heated and dried to cure the binder. By selecting the raw material composition and stirring conditions, an average particle size of 0.1-5 mm, which is suitable as a friction modifier,
A porous granular molded product having a bulk density of 0.2 to 2.0 g / cm ³ can be obtained. If the bulk density is higher than 2.0 g / cm ³ , sufficient pores cannot be introduced into the friction material.

The "bulk density" is a value measured by the following method. Bulk Density Measuring Method: Vertically Standing Inner Diameter 150mm
Put 100 g of sample into the metal cylinder of the cylinder and open the surface of the cylinder 1 cm ²
A weight of 50 g is applied by the weight. After 5 minutes, the height of the sample is measured to determine the volume V (cm ³ ). Bulk density (g / cm ³ ) = 100 / V

Porous granular moldings are extremely stable and rarely disperse into single fibers during normal handling and use as molding materials. In the friction material manufacturing raw material mixing step, the porous granular molded product is preferably blended in an amount of about 5 to 20% by weight of the entire raw material. If it is less than 5% by weight, the compounding effect is not sufficient, while if the compounding rate exceeds 20% by weight, the strength of the friction material is significantly reduced.

The porous granular molding is used as a kind of friction modifier as described above. Therefore, in the production of the friction material according to the present invention, in addition to this, raw materials usually used in the production of general friction materials are appropriately used. That is, asbestos, aluminosilicate fiber,
Ceramic fibers such as alumina fibers; glass fibers; heat-resistant organic fibers such as polyimide fibers and aromatic polyamide fibers;
In addition to fibrous base materials such as metal fibers made of copper, brass, steel, etc., silica, graphite, molybdenum sulfide, silicon nitride, boron nitride, metal powder, barium sulfate, wollastonite, cashew dust, thermosetting synthetic resin One kind or two or more kinds of pulverized products of the cured product can be used together for the purpose of adjusting frictional characteristics and other purposes.

The thermosetting synthetic resin used as the binder is not limited, and a commonly used one such as novolac type or resol type phenol resin or modified phenol resin can be used.

If all the raw materials to be used are uniformly mixed and the obtained raw material mixture is thermocompressed into a predetermined shape by a conventional method,
The friction material of the present invention is obtained. The porous granular molding maintains its original shape without flattening or crushing by the usual thermocompression molding. In addition, the porous structure is not lost due to the binder and the like entering into the pores. Therefore, the product is one in which the porous granular molding is uniformly introduced without losing its porosity.

[0021]

[Example] Aluminosilicate fiber (commercial item, Al ₂ O
₃ 50%, SiO ₂ 50%) was treated with a dry crusher to obtain 9
5% by weight or more of the fiber length was in the range of 5 to 500 μm and an average fiber length of 50 μm was obtained. After putting this in an agitation granulator with an equal amount of barium sulfate and stirring for 1 minute, 30% by weight of colloidal silica to aluminosilicate fiber and 2% by weight of CMC were added as a solid content, and further stirred for 4 minutes. Continued. Initially, the raw material fibers formed lumps of uneven size, but the lumps were crushed as the stirring was continued, and on the other hand, they were formed into small granules with barium sulfate, and the diameter gradually increased to about 0.1 to 5 mm. Only particulate matter became visible.

The obtained granular molded product has a bulk density of 0.80 g / c.
m ³ , porosity 75.0%, average particle size 0.4 mm, 95% by weight
The above was a particle size of 1 mm or less. FIG. 1 is a scanning electron micrograph of this porous granular molding.

Next, as shown in Table 1, a mixture of 8 parts by weight of aramid fiber, 20 parts by weight of phenol resin, 5 parts by weight of cashew dust and barium sulfate was used with or without the above porous granular molding. Friction material by hot pressing
Nos. 1 to 7 were manufactured. The ceramic fibers used in Comparative Examples Nos. 2 to 4, which did not use the porous granular molded product, were the finely-divided ceramic fibers used in the production of the granular molded product. Numerical values in the table are parts by weight.

[0024]

[Table 1] No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 Porous granular molded product − − − − 5 10 20 Ceramic fiber − 5 10 20 − − Barium sulfate 67 62 57 47 62 57 47

The porosity and bending strength of each of the obtained friction materials were measured, and Tables 2 and 3 show the relationship between the content of the ceramic fiber and the content thereof. From these tables, it is understood that in the friction materials No. 5 to 7 containing the ceramic fiber porous granular molding, the porosity could be increased without significantly lowering the bending strength. As shown in FIG. 2, the blended porous granular molding 1 is evenly distributed in the friction material 2 as it is, and each porous granular molding 1 in the friction material is The porosity was maintained as shown in the electron micrographs (photographs of the polished surface of the friction material) of FIGS.

[0026]

[Table 2] Change in porosity (%) Ceramic fiber content 0% 5% 10% 20% Granular molding compound 3.5 3.5 4.4 4.5 5.1 Non-granulated fiber products 3.5 2.7 2.7 3.9

[0027]

[Table 3] Changes in bending strength (kgf / cm ² ) Granular molded product or ceramic fiber content 0% 5% 10% 20% Granular molded product mixture 6.7 6.3 6.3 6.2 5.7 Non-granulated fiber product 6.7 7.2 6.9 6 .9

Next, friction materials No. 6 (invention product) and N
Wear test by a wear tester for o.3 (control example)
It was performed according to JIS D4411 "Brake lining for automobiles". The generation of squeaking was also tested. The results are shown in Table 4.

[0029]

[Table 4] No. 6 (invention product) No. 3 (control example) Abrasion rate (× 10 ^-7 cm ³ / kg · m) 100 ° C. 1.6 1.5 150 ° C. 0.9 1.0 200 ℃ 1.0 1.2 250 ℃ 1.3 1.5 No squeal occurrence Yes

[0030]

As described above, according to the present invention in which a porous granular molded product composed of a ceramic fiber and a filler is blended, fine pores are introduced into the friction material without lowering the strength or wear resistance. It is possible to prevent squeaking during braking by the friction material.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph (40 × magnification) of an example of a porous granular molded product used in the present invention.

FIG. 2 is a surface view showing a distribution of a porous granular molded product in a friction material according to the present invention.

FIG. 3 is a scanning electron micrograph (magnification: 100 times) of a polished surface of a friction material showing the presence of a porous granular molded product in the friction material according to the present invention.

FIG. 4 is a scanning electron micrograph (magnification: 400 times) of a polished surface of a friction material showing the presence of a porous granular molded product in the friction material according to the present invention.

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[Procedure amendment]

[Submission date] December 14, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

[0027]

[Table 3] Changes in bending strength (kgf / mm ² ) Granular molded product or ceramic fiber content 0% 5% 10% 20% Granular molded product mixture 6.7 6.3 6.3 6.2 5.7 Non-granulated fiber product 6.7 7.2 6.9 6 .9

Claims (3)

[Claims] 1. A friction material for a braking device, wherein a mixture of a fibrous material and a friction modifier is molded by using a thermosetting synthetic resin as a binder, and as a part of the friction modifier, a fiber length of 5 to 700 μm, average An average particle diameter of 0.1 to 5 mm and a bulk density of 0.2 to 2.0 g formed by using a binder and finely divided ceramic fibers having a fiber length of 50 to 150 μm and a filler.
A friction material for a braking device, characterized in that a porous granular molded product of / cm ³ is dispersed in the friction material while maintaining its porosity. 2. An average particle diameter of 0.1, which is obtained by molding finely divided ceramic fibers having a fiber length of 5 to 700 μm and an average fiber length of 50 to 150 μm with a binder.
The braking device is characterized in that a raw material for producing a friction material, in which a porous granular molding having a bulk density of 0.2 to 2.0 g / cm ³ is mixed as a part of the friction modifier, is mixed and thermocompression-molded. For manufacturing friction materials for automobiles. 3. A finely divided ceramic fiber having a fiber length of 5 to 700 μm and an average fiber length of 50 to 150 μm, and a filler selected from the group consisting of barium sulfate, wollastonite, cashew dust and carbon powder. The average particle size formed by using the agent is 0.1 to 5 mm, and the bulk density is 0.1.
A method for producing a friction material for a braking device, which comprises mixing a raw material for producing a friction material, in which a porous granular molding of 2 to 2.0 g / cm ³ is blended as a part of a friction modifier, and mixing the mixture by thermocompression molding.