Friction material

Abstract

To provide a friction material used for a brake shoe of a drum brake for a passenger car, which continuously reduces generation of low frequency noise and provides excellent braking effectiveness and wear resistance and is manufactured by forming a friction material composition which contains no cleavage substance, 8-12 weight % of a phenolic thermosetting resin as the binder, 9-18 weight % of cashew dust as the organic friction modifier, 6-12 weight % of a rubber particle, where the total amount of the cashew dust and rubber particle is 18-25 weight %, and 4-10 weight % of the aluminum particle as the inorganic friction modifier, all relative to the total amount of the friction material composition. The friction material contains the phenolic thermosetting resin consists of a straight novolak phenolic resin and the unvulcanized nitrile rubber (NBR) particle.

Claims

1. A friction material used for a brake shoe of a drum brake for a passenger car, which is manufactured by forming a friction material composition containing a binder, an organic fiber, an inorganic friction modifier, an organic friction modifier, a pH adjuster, and an inorganic filler, wherein said friction material composition does not comprise graphite, mica, or vermiculite but comprises 8-12 weight %, relative to the total amount of the friction material composition, of a phenolic thermosetting resin as the binder, 9-18 weight %, relative to the total amount of the friction material composition, of cashew dust and 6-12 weight %, relative to the total amount of the friction material composition, of a rubber particle as the organic friction modifier, where the total amount of the cashew dust and rubber particle is 18-25 weight % relative to the total amount of the friction material composition, and 4-10 weight %, relative to the total amount of the friction material composition, of metallic aluminum particle with an average particle diameter of 50-300 m as the inorganic friction modifier.

2. The friction material according to claim 1, wherein the phenolic thermosetting resin consists of a straight novolak phenolic resin.

3. The friction material according to claim 1, wherein said friction material composition contains an unvulcanized nitrile rubber (NBR) particle as a part of the rubber particle or an entire part of the rubber particle.

4. The friction material according to claim 2, wherein said friction material composition contains an unvulcanized nitrile rubber (NBR) particle as a part of the rubber particle or an entire part of the rubber particle.

Description

EMBODIMENTS OF THE INVENTION

(1) In this invention, a phenolic resin using as a binder can be resins normally used in a friction material such as a straight novolak phenolic resin, a modified resin obtained by modifying a phenolic resin with various types of elastomers such as a nitrile rubber or an acrylic rubber or various types of oils such as cashew oil or silicone oil, an aralkyl modified phenolic resin obtained by reacting a phenolic compound, an aralkyl ether compound, and an aldehyde compound, and a thermosetting resin obtained by dispersing such as various elastomers or a fluorine-containing polymer. In this invention, one type of the above-resin alone or any combination of two or more types of the above-resins may be used.

(2) Among those resins, it is preferable to use the straight novolak phenolic resin alone, which effectively inhibits the low frequency noise.

(3) The effective inhibition of the low frequency noise may be achieved because elasticity of the cured straight novolak phenolic resin is less than the elasticity of the cured resin obtained by curing an elastomer modified phenolic resin or an elastomer dispersed phenolic resin and it is estimated that the stick slip of the friction material against the mating member, while the drum brake is acted, is less likely to occur.

(4) The cashew dust as the organic friction modifier can be obtained by curing cashew nuts shell liquid or cashew nuts shell polymer by the aldehyde compound such as furfural and formaldehyde to crush the same or can be obtained by curing cashew nuts shell liquid or cashew nuts shell polymer by a curing agent such as hexamethylenetetramine to crush the same. Here, one type of the above-crushed cashew dust alone or any combination of two or more types of the above-crushed cashew dusts may be used. The amount of the cashew dust contained therein is 9-18 weight % relative to the total amount of the friction material composition.

(5) In addition, the rubber particle as the organic friction modifier can be a vulcanized rubber powder or an unvulcanized rubber powder such as a pulverized powder of a tire tread rubber, a nitrile rubber, a styrene-butadiene rubber, a butyl rubber, an acrylic rubber, and a silicone rubber.

(6) Among the above-mentioned rubber particles, it is preferable to use the unvulcanized nitrile rubber powder because the effectiveness of inhibiting the low frequency noise can be improved by adding the unvulcanized nitrile rubber partially or as the entire rubber powder.

(7) The amount of the rubber particles is 6-12 weight % relative to the total amount of the friction material composition, and the total amount of the cashew dust and the rubber particles is 18-25 weight % relative to the total amount of the friction material composition.

(8) Aluminum particles are used as a part of the inorganic friction modifier. By adding the aluminum particles, an aluminum film/layer is formed on a friction surface of the brake drum, and the occurrence of the stick slip that is a cause of the low frequency noise can be inhibited.

(9) It is preferable to use the aluminum particles which is manufactured by an atomizing method and has an average particle diameter of 50-300 m.

(10) In this invention, the average particle diameter means 50% particle diameter by the laser diffraction particle size distribution method.

(11) The friction material of this invention is made from the friction material composition further contains materials that are normally used in the friction material such as the fiber base (organic fiber), the inorganic friction modifier, the pH adjuster, and the inorganic filler in addition to the above-described phenolic thermosetting resin, the cashew dust, the rubber particles, and the aluminum particles.

(12) As the fiber base, organic fibers, that are normally used in the friction material, such as an aramid fiber, a cellulose fiber, and a polyacrylonitrile fiber may be used. The amount of the organic fiber contained in the friction material is preferably 5-10 weight % relative to the total amount of the friction material composition in order to secure the strength of the friction material.

(13) Other than the above-described aluminum particles, as the inorganic friction modifier, a particle type inorganic friction modifier such as a zirconium oxide, a magnesium oxide, a zirconium silicate, a silicon oxide, an a alumina, a y alumina, and a triiron tetroxide, a fiber type inorganic friction modifier such as a wollastonite, a sepiolite, a basalt fiber, a glass fiber, a biosoluble artificial mineral fiber, and a rock wool, and a metal particle or an alloy particle such as a copper particle, a brass particle, a bronze particle, and a zinc particle may be used. In this invention, one type of the above-inorganic friction modifier alone or any combination of two or more types of the above-inorganic friction modifier may be used.

(14) Discharging the friction powder of the copper component such as the copper particle, the brass particle, and the bronze particle gives an adverse effect on the environment, and therefore it is not preferable to add the copper component in the friction material component.

(15) The amount of the inorganic friction modifier together with the above-described aluminum particle is preferably 7-15 weight % relative to the total amount of the friction material composition.

(16) The pH adjuster such as a calcium hydroxide that is normally used in the friction material may be used. The amount of the pH adjuster contained in the friction material is preferably 3-15 weight % relative to the total amount of the friction material composition.

(17) An inorganic filler may be used as the remaining components other than the binder, the organic fiber, the organic friction modifier, the inorganic friction modifier, and the pH adjuster. As the inorganic filler, inorganic particles such as a heavy calcium carbonate, a barium sulfate, a kaolin, and a kibushi clay, which show small grindability against a cast iron that is a main material of the brake drum. In this invention, one type of the above-inorganic filler alone or any combination of two or more types of the above-inorganic filler may be used.

(18) The friction material in this invention used for the brake shoe of the drum brake utilizing for the passenger car is manufactured through a mixing step for uniformly mixing the predetermined amount of the friction material composition by a mixer, a heat press forming step for heat press forming the obtained raw friction material mixture after filling the same in a heat forming die, a heat treatment step for heating the obtained formed product to complete reactive curing of the binder, and a grinding step for forming a friction surface.

(19) If necessary, prior to the heat press forming step, a granulating step for granulating the raw friction material composition, a kneading step for kneading the raw friction material composition, and a preforming step for forming a preformed product after filling the raw friction material composition or the granulated friction material composition obtained through the granulation step and the kneaded friction material composition obtained through the kneading step in a preforming die.

EMBODIMENTS

(20) This invention is concretely explained using the embodiments and comparative examples are shown in the following sections, but this invention is not limited to the following embodiments.

Manufacturing Method for the Friction Material in the Embodiments 1-13 and Comparative Examples 1-13

(21) The friction material composition of the components shown in the TABLE 1 and TABLE 2 is mixed by a Loedige mixer for about 5 minutes and is press for 20 seconds under 10 MPa in the preforming metal die. After forming the obtained preformed product for 6 minutes at 150 centigrade of the forming temperature under 40 MPa of the forming pressure, the heat treatment (post curing) at 180 centigrade is conducted on the obtained formed product for 5 hours, and a friction surface is formed by grinding the post cured article to produce a brake lining (Embodiments 1-13 and comparative examples 1-13).

(22) TABLE-US-00001 TABLE 1 Embodiments 1 2 3 4 5 6 7 8 9 10 11 12 13 Binder Straight phenolic 10 5 10 8 12 10 10 10 10 10 10 10 10 resin NBR modified 0 5 0 0 0 0 0 0 0 0 0 0 0 phenolic resin Organic Aramid fiber 6 6 6 6 6 6 6 6 6 6 6 6 6 fiber Cellulose fiber 2 2 2 2 2 2 2 2 2 2 2 2 2 Lubricant Squamous 0 0 0 0 0 0 0 0 0 0 0 0 0 graphite Organic Cashew dust 12 12 12 12 12 11 16 12 12 9 18 13 12 friction Nitrile rubber 8 8 4 8 8 7 9 8 8 10 6 6 12 modifier (NBR) particle Tire tread 0 0 4 0 0 0 0 0 0 0 0 0 0 rubber pulverized powder Inorganic Aluminum 7 7 7 7 7 7 7 4 10 7 7 7 7 friction particle modifier Silicon oxide 2 2 2 2 2 2 2 2 2 2 2 2 2 particle Triiron tetroxide 2 2 2 2 2 2 2 2 2 2 2 2 2 particle Mica 0 0 0 0 0 0 0 0 0 0 0 0 0 Vermiculite 0 0 0 0 0 0 0 0 0 0 0 0 0 pH Calcium 10 10 10 10 10 10 10 10 10 10 10 10 10 adjuster hydroxide particle Inorganic Heavy calcium 41 41 41 43 39 43 36 44 38 42 37 42 37 filler carbonate particle Total 100 100 100 100 100 100 100 100 100 100 100 100 100

(23) TABLE-US-00002 TABLE 2 Comparative Examples 1 2 3 4 5 6 7 8 9 10 11 12 13 Binder Straight phenolic 7 13 10 10 10 10 10 10 10 10 10 10 10 resin NBR modified 0 0 0 0 0 0 0 0 0 0 0 0 0 phenolic resin Organic Aramid fiber 6 6 6 6 6 6 6 6 6 6 6 6 6 fiber Cellulose fiber 2 2 2 2 2 2 2 2 2 2 2 2 2 Lubricant Squamous 0 0 0 0 0 0 3 0 0 0 0 0 0 graphite Organic Cashew dust 12 12 10 17 12 12 12 12 12 8 19 13 12 friction Nitrile rubber 8 8 7 9 8 8 8 8 8 10 6 5 13 modifier (NBR) particle Tire tread 0 0 0 0 0 0 0 0 0 0 0 0 0 rubber pulverized powder Inorganic Aluminum 7 7 7 7 3 11 7 7 7 7 7 7 7 friction particle modifier Silicon oxide 2 2 2 2 2 2 2 2 2 2 2 2 2 particle Triiron tetroxide 2 2 2 2 2 2 2 2 2 2 2 2 2 particle Mica 0 0 0 0 0 0 0 3 0 0 0 0 0 Vermiculite 0 0 0 0 0 0 0 0 3 0 0 0 0 pH Calcium 10 10 10 10 10 10 10 10 10 10 10 10 10 adjuster hydroxide particle Inorganic Heavy calcium 44 38 44 35 45 37 38 38 38 43 36 43 36 filler carbonate particle Total 100 100 100 100 100 100 100 100 100 100 100 100 100

(24) The low frequency noise, the braking effectiveness, and the wear resistance of the brake linings according to the Embodiments 1-13 and the Comparative Examples 1-13 are evaluated. The evaluation standard is shown in TABLE 3, and the evaluation results are shown in TABLE 4 and TABLE 5.

(25) TABLE-US-00003 TABLE 3 Evaluation Items Low Frequency Low Frequency Braking Wear Noise 1 Noise {circle around (2)} Effectiveness Resistance (After Evaluating Low Frequency Noise {circle around (1)}) Evaluation Method Burnish First Fade Based on Based on Based on Recovery Test JASO C406-00 JASO C427 JASO(Japanese Based on (Passenger (Brake Lining Automobile JASO C402-99 Car-Braking And Disc Brake Standard (Passenger Device- Pad-Wear Organization) Cars- Dynamometer Test Procedure C406-00 Service Brake Test On Inertia (Passenger Car- Road Test Procedures) Dynamometer) Braking Device- Procedures) Initial Braking Initial-Brake Dynamometer Test Initial Braking Speed: Temperature: Procedures) Speed: 100 km/h 200 centigrade Initial Braking 100 km/h Speed: 60 km/h Braking Braking Deceleration: Deceleration: 4.5 m/s2 3.5 m/s2 Repetitions: 10 Initial-Brake Temperature: 60 centigrade Repetitions: 200 Low Frequency Noise Evaluation Testing Based on JASO C402-99 (Passenger Cars-Service Brake Road Test Procedures) Initial Braking Speed: 20 km/h Initial-Brake Temperature: 50 centigrade Braking Deceleration; 1.96 m/s2 Repetitions: 10 Number of Occurrence of Low Average of the Amount of Frequency Noise Second Wear of Effectiveness Fricion Testing Material at 1000 times applications Evaluation Standard 0 0.31 or more Less than 0.10 mm 1-4 0.28 or more 0.10 mm or less than 0.31 more less than 0.15 mm 5-7 0.25 or more 0.15 mm or less than 0.28 more less than 0.20 mm X 8-10 Less than 0.25 0.20 mm or more

(26) TABLE-US-00004 TABLE 4 Embodiments 1 2 3 4 5 6 7 8 9 10 11 12 13 Evaluation Low Result Frequency Noise {circle around (1)} Low Frequency Noise {circle around (2)} Braking Effectiveness Wear Resistance

(27) TABLE-US-00005 TABLE 5 Comparative Examples 1 2 3 4 5 6 7 8 9 10 11 12 13 Eval- Low x x x x uation Frequency Result Noise {circle around (1)} Low x x x x x x x Frequency Noise {circle around (2)} Braking x x x x x Effective- ness Wear x x x Resistance

INDUSTRIAL APPLICABILITY

(28) According to this invention, in the friction material used for the brake shoe of the drum brake utilizing for the passenger car, the friction material in this invention provides a great practical value as it can reduce occurrence of the low frequency noise continuously and provide the excellent braking effectiveness and wear resistance.