JPH09136972A - Friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a friction material which, when used as the friction material of the brake of an automobile, does not produce any foreign sound when the automobile is started or stopped by specifying the rate of the area covered by a non-opened ceramic fiber having a specified size to the shearing area of the friction member. SOLUTION: A non-opened ceramic fiber (here after referred to as ceramic fiber) being in a lumpy state in which fibers made of the same material or having the same composition exist continuously and having a minimum size of 2mm or above and a maximum size of 7mm or below is allowed to occupy 1-40%, desirably 5-30wt.% of the area of the shearing surface (the sliding surface or the surface obtained by laterally cutting the friction member). A ceramic fiber having a small amount of fibers having size outside the range of 2-7mm may be used if it can give a molding in which the sizes of all the fibers fall within the range of 2-7mm. The ceramic fiber is made of a mixture comprising at least one member selected from among alumina, zirconia, silica, etc., and is used in an amount of 0.3-15wt.% based on the total composition. A fibrous material other than the ceramic fiber, a binder, a friction modifier and additives are also used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material suitable for braking automobiles, railway vehicles, various industrial machines and the like.

[0002]

2. Description of the Related Art Friction materials are used for braking automobiles, railway vehicles, various industrial machines and the like. Conventionally, as the friction material, as shown in JP-A-64-87930 and JP-A-2-117985, a semi-metallic friction material having steel fibers as a main constituent fiber has been mainly used. As the automobile industry shifts to lighter weight and higher quality, problems such as abnormal noise when starting and stopping an automatic vehicle, insufficient braking force at low temperatures, and wheel dirt due to abrasion powder have come up. . The abnormal noise generated here has a speed of 3
It is the noise (sound pressure of 70 dB or more) that accompanies braking of the friction material that appears in the process of decelerating from 0 km / h, and the frequency is about 100 (Hz), which is a sound in a region where passengers feel uncomfortable.

In order to solve these problems, non-steel friction materials using non-ferrous metal fibers such as copper fibers and brass fibers, organic fibers such as aramid fibers, and inorganic fibers such as ceramic fibers as an alternative to steel fibers. The transition of has come at a rapid pace. However, even in the non-steel friction material, an abnormal noise is generated due to the braking of the friction material similar to the above, and it is still unsolved. In the prior art, in order to prevent the generation of this abnormal noise, rubber-modified resin or powdered rubber was compounded in the binder to improve the flexibility of the friction material, but the binder itself is given flexibility. Stay in
It has not been possible to sufficiently prevent the generation of abnormal noise due to braking of the friction material.

[0004]

SUMMARY OF THE INVENTION The present invention provides a friction material which prevents the generation of abnormal noise when the vehicle starts or stops.

[0005]

The present invention has a minimum dimension of two.
The present invention relates to a friction material in which non-disintegrated ceramic fibers having a maximum dimension of 7 mm or more and 7 mm or less occupy 1 to 40 area% with respect to a shear surface of a friction member.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, non-cottoning ceramic fiber (hereinafter referred to as ceramic fiber) means a lump state in which fibers of the same material or the same composition are continuously present. The sheared surface of the friction member means a sliding surface of the friction member or a surface obtained by cutting the friction member in the lateral direction (sliding direction).

The ceramic fiber in the present invention having a minimum dimension of 2 mm or more and a maximum dimension of 7 mm or less is 1 to 40 area%, preferably 5 to 30 area%, and more preferably 10% with respect to the sheared surface of the friction member. It is necessary to occupy up to 20 area%, and if the occupancy rate is less than 1 area%, it is not possible to efficiently remove the resin liquefaction, which is considered to be the cause of abnormal noise generated at the friction interface during braking. Therefore, the problem of noise generation cannot be solved, and when it exceeds 40% by area, the strength of the friction material is significantly reduced.

In the present invention, the ceramic fiber occupies a minimum size of 2 mm or more and a maximum size other than 7 mm to some extent, but it can be suppressed as small as possible by using a ceramic fiber having the above size after molding. it can. Even if the area less than 2 mm and / or more than 7 mm occupies about 5 area% of the shear surface of the friction member, the area of 2 to 7 mm ranges from 1 to 40 area% of the shear surface of the friction member. There is no problem if it is contained. However, 2
If you occupy a large amount of less than 7 mm, you can not efficiently remove the resin liquefaction, it is not possible to solve the problem of noise generation, while if you occupy a large amount of more than 7 mm, the friction member cracks during molding. , Wrinkles and the like tend to occur, and the strength of the friction material tends to remarkably decrease. As a material for the ceramic fiber, one or a mixture of two or more of alumina, zirconia, silica and the like is used. The ceramic fiber is preferably contained in the composition in an amount of 0.3 to 15% by weight.

The occupancy rate of the ceramic fiber is obtained by first reading the shear plane of the ceramic fiber with an image scanner and using the "KL / KS system" manufactured by Kurashiki Spinning Co. Continuous circle →
Continuous circle line). After conversion, the vector data can be transferred to the CAD of Hitachi Shipbuilding Information Systems Co., Ltd. via Ethernet.
Transferred to "GRADE / DRAW", the area of the closed range of the continuous circumferential line was individually tabulated on CAD, and calculated as the occupancy ratio to the shear plane.

In the friction material according to the present invention, in addition to ceramic fibers, fibrous substances other than ceramic fibers, binders, friction modifiers and the like are used. Further, various additives such as a bulking agent, a dispersant, a thickening agent, a softening agent, and a surfactant are used if necessary. As the fibrous substances other than the ceramic fibers, copper fibers, non-ferrous metal fibers such as brass fibers,
Organic fibers such as polyimide fiber, polyamide fiber, aramid fiber, phenol fiber, rock wool, glass fiber,
Inorganic fibers such as carbon fibers are used. As the binder, a thermosetting resin such as liquid cashew resin, rubber latex, melamine resin, urea resin, polyamideimide resin, polyimide resin, phenol resin or epoxy resin is used.

The friction modifier is classified into a filler, a friction increasing material and a lubricant. As the filler, powders of inorganic substances such as calcium carbonate, magnesium carbonate, barium sulfate, etc., and organic powders such as cashew dust, rubber dust, powders of various resin cured products, etc. are used. As the friction-increasing material, powders of inorganic materials such as alumina, mica, zirconia, hematite, silica and powders of metals such as iron, lead, copper and brass are used. As the lubricant, clay, talc, fluorite, graphite, antimony sulfide, iron sulfide, molybdenum sulfide, etc. are used.

The binder is 4 to 20% by weight in the total composition.
The content of the fibrous substances other than the ceramic fibers is preferably 10 to 15% by weight in the total composition, and the friction modifier is used as a filler in the entire composition. In the range of 45 to 60% by weight, the friction-increasing agent is contained in the range of 4 to 6% by weight, and the lubricant is contained in the range of 5 to 7% by weight.

In the present invention, if the friction modifier excluding the ceramic fiber, the inorganic fiber, the organic fiber, the binder, etc. and the non-ferrous metal fiber are coated with a liquid resin or liquid rubber having an adhesive property, they are mixed with other components. It is preferable because it has excellent mixability and dispersibility. In the present invention, a friction modifier and a non-ferrous metal fiber coated with a liquid resin or liquid rubber are used as a preliminary composition. The preliminary composition is preferably contained in the total composition in an amount of 70 to 95% by weight. The liquid resin or liquid rubber is preferably contained in the preliminary composition in an amount of 1 to 25% by weight. If the amount of the liquid resin or liquid rubber is small, the powder of the friction modifier is insufficiently coated, and if the amount is too large, lumps are likely to be formed during mixing with the powder, and a homogeneous product tends to not be obtained.

The liquid resin or liquid rubber is not particularly limited, but examples of the liquid resin include cashew resin,
Examples of the liquid rubber include SBR. Viscosity when using liquid resin or liquid rubber is 500-1 at 20 ℃
000 poise is preferred. If the viscosity is low, the coating will be insufficient, and if it is too high, aggregation will occur and the coating will tend to be insufficient.

The friction material according to the present invention is prepared by first applying a preliminary composition containing a ceramic fiber, an inorganic fiber, an organic fiber, a friction modifier excluding a binder, and a non-ferrous metal fiber to a liquid resin or liquid rubber having an adhesive property. After coating with, the minimum dimension after compression molding is 2 mm or more and the maximum dimension is 7 mm or less in an amount of 1 to 40 area% with respect to the shear surface of the friction member, ceramic fibers, other inorganic fibers, and organic fibers. , Adding a binder and the like, mixing at a low speed of about 200 rpm for a short time of about 5 minutes, and then inserting the back metal and the mixture into a mold,
It is obtained by heating, press-molding, heat-treating and cooling if necessary, and polishing the surface.

[0016]

EXAMPLES Examples will be described below, but the present invention is not limited thereto. The following materials were used in this example. A: Inorganic fiber: manufactured by Toshiba Monoflux Co., Ltd., ceramic fiber (a mixture fiber of alumina, zirconia, and silica),
Product name RFC1000-ST, dimensions (minimum 5 mm, maximum 5
5mm lump) B ... Liquid cashew resin: Hitachi Chemical Co., Ltd., not for sale,
Viscosity at 20 ° C 780 Poise C ... Silica powder: Elchem Japan Co., Ltd., Microsilica D ... Thermosetting resin: Hitachi Chemical Co., Ltd., phenol resin, trade name HP491 E ... Aramid fiber: Toray Co., Ltd. Made, Kevlar fiber F ... Barium sulfate: Sakai Chemical Industry Co., Ltd., BCG ... Cashew dust: Cashew Co., Ltd., friction dust, trade name H101 H ... Metal fiber: Tokyo Seiko Co., Ltd., copper fiber I ... Graphite: manufactured by Nippon Graphite Industry Co., Ltd., graphite, maximum particle size 400 μm, average particle size 150 μm

Examples 1 to 3 and Comparative Examples 1 and 2 First, the amount of B material (amount as solid content) shown in Table 1 was diluted with water to B: water = 1: 2 (weight ratio) to obtain a viscosity. Was made to be 670 poise at 20 ° C., and materials C, F, G, H and I were added thereto in amounts shown in Table 1 and uniformly mixed with a mixer to obtain a preliminary composition. Then, it was dried at 80 ° C. for 60 minutes to remove water. Next, the mixture is mixed with other materials A in the amounts shown in Table 1,
The friction material composition was obtained by putting the mixture in a mixer together with D and E and uniformly mixing for a short time at a low speed rotation of 200 rpm × 5 minutes. The obtained friction material composition was a homogeneous composition without material separation. After that, insert the back metal and the friction material composition into the mold, heat and pressure mold for 12 minutes under the conditions of temperature 140 ° C. and pressure 40 MPa, heat-treat at 200 ° C. for 5 hours, and after cooling, polish the surface. Got a disc brake pad.

[0018]

[Table 1]

Next, a 5 mm portion from the tip of the friction member of each disc brake pad obtained above is cut laterally, and the cut surface (shear surface) is 2 mm or more with respect to the shear surface using an optical microscope. The occupancy of the ceramic fiber having the maximum dimension of 7 mm or less was investigated. Table 2 shows the results.

Regarding each of the disc brake pads obtained above, 2000cc of an actual vehicle (manufactured by Nissan Motor Co., Ltd., Cedric (Y2)) according to the test method according to JASO C402.
An automatic vehicle test) was conducted to measure abnormal noise during the test, and the occurrence rate and maximum sound pressure were determined. Regarding the efficacy, the efficacy as a disc brake during the test is μ
The surface attack amount of the mating material was evaluated by the grinding amount of the rotor.
The disc brake pad of Comparative Example 2 was destroyed during the test, and therefore it was not possible to evaluate each characteristic.

[0021]

[Table 2]

As shown in Table 2, in the disc brake pads of the examples, the sound pressure (abnormal sound) generation rate of 70 dB or more was 0%, and the maximum sound pressure was 68 dB. (Rotor) It was confirmed that the amount of surface attack was excellent.

[0023]

INDUSTRIAL APPLICABILITY The friction material according to the present invention can prevent the generation of abnormal noise when the vehicle starts or stops or suppress it as much as possible without roughening the surface of the mating material. It is a material.

Claims (1)

[Claims] 1. A friction material comprising non-cotton ceramic fibers having a minimum dimension of 2 mm or more and a maximum dimension of 7 mm or less, occupying 1 to 40 area% with respect to a shear surface of a friction member.