JP2001164238A - Friction material composition and friction material using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction material composition that has a stabilized friction coefficient and can suppress the noise emission and provide a friction material that has stabilized friction coefficient and can suppress the noise emission. SOLUTION: The objective friction material composition includes 2-36 wt.% of hydrogen-embrittlement metallic fibers with a hydrogen embrittlement of 5-30% in the composition and the composition is compression-molded with heat to give the objective friction material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material composition suitable for a friction material such as a disc brake pad and a brake lining used for braking automobiles, railway vehicles, various industrial machines and the like, and a friction material composition. Related to friction material.

[0002]

2. Description of the Related Art Friction materials such as disc brake pads and brake linings are used in automobiles, railway vehicles, various industrial machines and the like for braking. Conventionally, as this friction material, Japanese Patent Application Laid-Open No.
As shown in Japanese Patent Publication No. 117985, semi-metallic friction materials mainly composed of steel fibers were mainly used, but automatic vehicles have been started in line with the shift to lighter and higher-grade automobile industries. Problems such as generation of abnormal noise at the time of stoppage and stoppage, insufficient braking force at low temperatures, and wheel contamination due to abrasion powder have come up. The abnormal noise generated here has a speed of 30 km /
This is noise (sound pressure of 70 dB or more) associated with braking of the friction material that appears in the process of decelerating from about time, and is a sound of a frequency of about 100 (Hz) in a region where a passenger feels uncomfortable.

[0003] In order to solve these problems, non-ferrous metal fibers such as copper fiber and brass fiber are used instead of steel fiber.
The transition to organic and inorganic fibers such as aramid fibers and ceramic fibers, and non-steel friction materials using abrasives of inorganic materials in order to obtain a stable friction coefficient (μ ≧ 0.38) has rapidly progressed. .

In the prior art, the friction coefficient has been stabilized by the above-mentioned inorganic material abrasive, but the abrasive attacks the metal (rotor) of the mating material, and in the process, squeal noise and abnormal noise occur. And other disadvantages such as the occurrence of noise. At present, a friction material having a stable friction coefficient and completely suppressing generation of noise has not been obtained by using a grinding agent mainly composed of an organic material including an inorganic material.

[0005]

The first and second aspects of the present invention provide a friction material composition suitable for a friction material having a stable friction coefficient and capable of suppressing generation of noise. It is. The invention described in claim 3 provides a friction material having a stable friction coefficient and capable of suppressing generation of noise.

[0006]

According to the present invention, a hydrogen-brittle metal fiber having a hydrogen brittleness of 5 to 30% is contained in the total composition in an amount of 2 to 36%.
The present invention relates to a friction material composition containing 0.1% by weight. In addition, the present invention provides a hydrogen-brittle metal fiber having a diameter of 50 to 100 μm,
The present invention relates to the friction material composition having a length of 1 to 50 mm.
Further, the present invention relates to a friction material obtained by heating and pressing the above friction material composition.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a hydrogen-brittle metal fiber means that hydrogen starts to penetrate from the surface of a metal fiber to be used and collects in a void, and the void is mechanically cracked, thereby forming a micro crack. This means that brittle fracture (hydrogen-induced cracking) starts when this is sufficiently grown, and a metal fiber that easily causes such brittle fracture is defined as a hydrogen-brittle metal fiber in the present invention.

The content of hydrogen-brittle metal fibers is in the range of 2 to 36% by weight, preferably 5 to 33% by weight, more preferably 8 to 30% by weight and less than 2% by weight in the total composition. And a stable friction coefficient (μ ≧ 0.38) cannot be obtained. On the other hand, if it exceeds 36% by weight, the generation of noise cannot be suppressed.

[0009] Hydrogen brittle metal fibers include Zr, Hf,
It is preferable to use metal fibers such as Ti. The hydrogen embrittlement rate in the hydrogen embrittlement metal fiber is in the range of 5 to 30%, preferably in the range of 10 to 25%, more preferably 13 to 2%.
If it is less than 5%, the metal fiber is too hard to suppress the generation of noise. On the other hand, if it exceeds 30%, a stable friction coefficient (μ ≧ 0.38) cannot be obtained.

[0010] In the present invention, the hydrogen embrittlement rate can be determined visually or by using a high-speed image processing apparatus S manufactured by Nippon Avionics Co., Ltd.
Using "PICCA II", the metal part (black part) and the brittle part (white part) in the metal fiber were measured separately, and determined by the formula shown in Equation 1.

[0011]

(Equation 1)

[0012] The diameter of the hydrogen-brittle metal fiber is 50-100.
It is preferable to use one having a range of μm,
It is more preferable to use one having a range of μm. If the diameter is less than 50 μm, the shape of the metal fiber tends to be unable to be maintained. On the other hand, if the thickness exceeds 100 μm, the damping characteristics due to hydrogen-induced cracking of the metal surface due to hydrogen embrittlement will not be improved, and a stable friction coefficient (μ ≧ 0.38) will not be obtained.

The length of the hydrogen-brittle metal fiber is 1 to 5
It is preferable to use one having a range of 0 mm, and 2 to 30 mm
It is more preferable to use those in the range described above. Length 1
If the diameter is less than mm, the shape of the metal fiber tends to be unable to be maintained. On the other hand, if the thickness exceeds 50 mm, the damping characteristics due to hydrogen-induced cracking of the metal surface due to hydrogen embrittlement do not improve, and a stable friction coefficient (μ ≧ 0.3
8) tends not to be obtained.

The target value of the noise in the present invention is JAS
The actual vehicle test of OC402 was performed, and the abnormal noise during the test was measured.
Times or less.

The friction material composition according to the present invention comprises, in addition to the hydrogen-brittle metal fiber, a binder, a reinforcing fiber, a lubricant, a filler,
An abrasive or the like is used, and a metal powder such as brass or bronze is used as necessary. The binder used in the present invention includes a phenol resin, an epoxy resin, a melamine resin and the like, among which it is preferable to use a phenol resin,
In particular, it is preferable to use a novolak resin, a solid ammonia resol resin, a silicon-modified phenol resin, and an acrylic rubber-modified phenol resin. In the present invention, a curing agent is added to the binder as needed. The binder is preferably contained in the entire composition in an amount of 5 to 20% by weight, more preferably 8 to 14% by weight, from the viewpoint of moldability and the like. Also. Hexamethylenetetramine, paraformaldehyde, trioxane, or the like is used as a curing agent that is added as needed, and the binder preferably contains 8 to 14% by weight, more preferably 10 to 12% by weight.

Examples of the reinforcing fibers include inorganic fibers such as glass fibers, ceramic fibers, carbon fibers, and mineral fibers; organic fibers such as aramid fibers, polyamide fibers, and polyimide fibers; copper fibers other than hydrogen-brittle metal fibers; brass fibers; Metal fibers such as fibers are used. The reinforcing fiber is preferably contained in the entire composition in an amount of 0.5 to 16% by weight, preferably 3 to 10%.
More preferably, it is contained by weight. The length of the reinforcing fiber varies depending on the material. For example, the inorganic fiber preferably has a length of 15 to 50 mm, more preferably 20 to 45 mm. The organic fibers are preferably 0.8-4 mm, more preferably 1-2 mm.
The metal fiber is preferably 1 to 5 mm, more preferably 2 to 4 mm.

As a lubricant, graphite, antimony sulfide, molybdenum sulfide, etc., as a filler, cashew dust, rubber dust, barium sulfate, calcium carbonate, magnesium carbonate, silica, etc., and as an abrasive, alumina powder, Zircon sand powder or the like is used alone or in combination of two or more. The lubricant is preferably contained in the entire composition at 2 to 8% by weight, more preferably at 3 to 6% by weight. The filler is preferably contained in the entire composition in an amount of 10 to 60% by weight, more preferably 20 to 50% by weight. The abrasive is preferably contained in the entire composition at 0.1 to 10% by weight, more preferably 0.5 to 8% by weight. Further, the metal powder optionally added is preferably contained in the entire composition in an amount of 1 to 8% by weight, more preferably 3 to 6% by weight. The usage ratio of each component constituting the friction material composition is adjusted so that the total amount thereof becomes 100% by weight.

The friction material composition according to the present invention is produced by mixing the respective components in an appropriate order, but is obtained through a predetermined process and obtains a hydrogen-brittle metal fiber having a predetermined hydrogen brittleness. Then, it is preferable that the hydrogen-brittle metal fiber and other materials are blended and mixed to produce the mixture.

The friction material according to the present invention is obtained by inserting and filling a backing metal and a friction material composition in a mold, molding by a heat and pressure molding method, and then performing a heat treatment. The heating temperature at the time of molding is preferably 130 to 170 ° C.
0-160 degreeC is more preferable. The pressure is preferably 30 to 60 MPa, more preferably 45 to 55 MPa. The heat treatment temperature is preferably from 100 to 300C, more preferably from 150 to 250C.

[0020]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited thereto. Examples 1 to 5 and Comparative Examples 1 to 4 A Zr fiber having a diameter of 60 μm and a length of 25 mm was put into a vacuum furnace heated to 400 ° C., and hydrogen gas was gradually added to keep the pressure in the vacuum furnace at 1 Torr. After heating for a time to obtain a desired hydrogen embrittlement rate to cause brittle fracture, Table 1
The hydrogen embrittlement Zr fiber having the hydrogen embrittlement rate shown in Table 1 was obtained. The hydrogen embrittlement ratio shown in Table 1 was measured using a "high-speed image processor SPICCA II" manufactured by Nippon Avionics Co., Ltd. Was divided and measured, and it was determined by the equation shown in the above equation (1).

Next, Table 1 shows the hydrogen-brittle Zr fibers obtained above.
And other materials in the amounts shown in Table 2 were blended and uniformly mixed by a mixer to obtain a friction material composition. Thereafter, the back metal and the friction material composition are inserted and filled in the mold, and then heated and pressed at 140 ° C. and a pressure of 40 MPa for 12 minutes.
Heat treatment was performed at 00 ° C. for 5 hours to obtain a disc brake pad.

[0022]

[Table 1]

[0023]

[Table 2]

Next, a comparative test was performed on the disc brake pad according to the present invention and the disc brake pad of the comparative example. The test results are shown in Tables 3 and 4. The test conditions are as follows. Damping characteristics The primary / secondary damping ratio was determined at room temperature by the impulse hammer method, and the elastic modulus was measured. Wear resistance Caliper model: Collet type (cylinder area 28.8
cm ² ) Test conditions: Inertia ... 4 according to JASO C427
9kgm ² , initial braking speed: 60km / h, deceleration: 2.94
m / sec. ^2, braking before temperature ... 250 ℃, braking number of times ... each 100
The wear amount was measured under the condition of every 0 times.

Abnormal noise generation status and effectiveness A real car test of JASO C402 was performed on a 2000 cc automatic car (Nissan Motor Co., Ltd. model name Cedric (Y33)), and the abnormal noise during the test was measured. The occurrence rate of abnormal noise and the maximum sound pressure were determined. As for the effect, the effect as a disc brake during the test is expressed in μ value,
The amount of attack on the surface of the mating material was evaluated by the amount of grinding of the rotor. Formability The appearance of the disc brake pad was visually observed, and the occurrence of wrinkles and cracks was observed.

[0026]

[Table 3]

[0027]

[Table 4]

As shown in Tables 3 and 4, it was confirmed that the disc brake pad according to the present invention was free of wrinkles and cracks and was excellent in all characteristics. On the other hand, the disc brake pads of Comparative Examples 1 to 4 have disadvantages in the actual vehicle abnormal noise generation rate, the actual vehicle abnormal noise maximum sound pressure, and the effectiveness, and the disc brake pads of Comparative Examples 2, 3, and 4 have disadvantages in elastic modulus. And the disk brake pad of Comparative Example 2 had a defect in the amount of attack on the surface of the mating material.

[0029]

The friction material compositions according to the first and second aspects can provide a friction material having a stable friction coefficient (μ ≧ 0.38) and capable of suppressing generation of noise. The friction material according to claim 3 has a stable friction coefficient (μ ≧ 0.38) and can suppress noise generation, and is industrially extremely suitable.

Claims (3)

[Claims] 1. A friction material composition comprising 2 to 36% by weight of hydrogen-brittle metal fibers having a hydrogen brittleness ratio of 5 to 30% in the total composition. 2. The hydrogen-brittle metal fiber has a diameter of 50 to 100.
2. The friction material composition according to claim 1, which has a length of 1 to 50 mm in μm. 3. A friction material formed by heating and pressing the friction material composition according to claim 1.