FRICTION PAIR

Abstract

To provide a friction pair capable of inhibiting to form a lump of a metal on a friction surface of a disc rotor, where the friction pair is consisting of a disc brake pad having a friction material manufactured from a friction material composition containing a binder, a fiber base material, and a friction modifier, but not containing a copper component and a ferrous-based metal fiber, and a stainless steel disc rotor. To use a friction material composition containing 1-6 weight % of a trimanganese tetraoxide as a friction modifier relative to an entire amount of the friction material composition but not containing any metal fiber.

Claims

1. A friction pair being consisting of a disc brake pad having a friction material manufactured from a friction material composition comprising a binder, a fiber base material, and a friction modifier, and also not comprising a copper component and a ferrous-based metal fiber, and a stainless steel disc rotor, wherein the friction material composition comprises 1-6 weight % of a trimanganese tetraoxide relative to an entire amount of the friction material composition as an inorganic friction modifier but does not comprise any metal fiber other than a ferrous-based metal fiber.

2. The friction pair according to claim 1, wherein the friction material composition contains 1-10 weight % of a graphite relative to the entire amount of the friction material composition as a lubricant.

Description

EMBODIMENTS OF THE INVENTION

[0028] A stainless steel disc rotor shows smaller conductivity and diffusivity than a cast iron disc rotor. Also, the stainless steel shows slightly larger specific gravity but higher strength than the cast iron. Therefore, the stainless steel disc rotor needs to be thinner in order to secure the equivalent specific gravity and the strength to the cast iron disc rotor. Accordingly, a heat capacity of the disc rotor is smaller, which tends to accumulate the disc rotor heat to increase the temperature of the friction material.

[0029] Furthermore, the stainless steel is characterized to stretch to a large extent likely to cause plastic deformation. Thus, when the disc rotor temperature becomes high, there is a problem of the disc rotor surface tending to tear-off, which forms a lump of metal of the component of the disc rotor.

[0030] The lump of metal formed on the disc rotor surface can be a cause of an abnormal wear of the friction material, and therefore a technology for inhibiting to form the lump of the metal is on demand.

[0031] In consideration of the above-issue, with respect to the friction pair that is consisting of the disc brake pad including the friction material having the friction material composition containing the binder, the fiber base material, and the friction modifier but not containing the copper component and the ferrous-based metal fiber, and the stainless steel disc rotor, this invention uses the friction material composition that contains 1-6 weight % of the trimanganese tetraoxide as the friction modifier relative to the entire amount of the friction material composition but does not contain any metal fiber other than the ferrous-based metal fiber.

[0032] The trimanganese tetraoxide is reduced and changed to a manganese due to a frictional effect. This manganese operates to improve a toughness of the stainless steel, thereby hindering the tear-off of the disc rotor surface to inhibit the forming of the lump of the metal on the disc rotor friction surface.

[0033] Also, by adding 1-10 weight % of graphite, relative to the entire amount of the friction material composition, such as an artificial graphite, a natural graphite, and a graphite sheet pulverized powder in the friction material composition, the reduction of the trimanganese tetraoxide is accelerated, and an effect of suppressing formation of the lump of the metal on the disc rotor friction surface is improved.

<Friction Material Composition>

[0034] The friction material used in the friction pair of this invention is manufactured from the friction material composition containing the binder, the fiber base material, and the friction modifier in addition to the above-explained trimanganese tetraoxide and graphite.

[0035] As the binder, either one of binders that are generally used for the friction material such as a straight phenol resin, an acrylic rubber modified phenol resin, a silicone rubber modified phenol resin, a nitrile rubber (NBR) modified phenol resin, a cashew nuts shell liquid (CNSL) modified phenol resin, an aralkyl modified phenol resin (phenol aralkyl resin) obtained by reacting a phenol compound, an aralkyl ether compound and an aldehyde compound, an acrylic rubber dispersed phenol resin, a silicone rubber dispersed phenol resin, and a fluoropolymer dispersed phenol resin, or a combination of two or more of the above-identified binders may be used.

[0036] The amount of the binder contained in the friction material composition is preferably 4-9 weight % relative to the entire amount of the friction material composition, more preferably 6-8 weight % relative to the entire amount of the friction material composition.

[0037] As the fiber base material, either one of fiber base materials that are generally used for the friction material such as an aramid fiber, an acrylic fiber, a cellulose fiber, and a poly-phenylene benzbisoxazole fiber, or a combination of two or more of the above-identified fiber base materials may be used.

[0038] The amount of the fiber base material contained in the friction material composition is preferably 1-5 weight % relative to the entire amount of the friction material composition, more preferably 2-4 weight % relative to the entire amount of the friction material composition.

[0039] As the friction modifier, a lubricant, an inorganic friction modifier, and an organic friction modifier may be used.

[0040] As the lubricant, either one of carbon based lubricants such as an artificial graphite, a natural graphite, a graphite sheet pulverized powder, a petroleum coke, a coal coke, a resilient graphitic carbon, and a polyacrylonitrile oxide fiber pulverized powder, or metal sulfide lubricants such as a tin sulfide, a molybdenum disulfide, an iron sulfide, a bismuth sulfide, a zinc sulfide, and a composite metal sulfide, or a combination of two or more of the above-identified lubricants may be used.

[0041] The amount of the lubricant contained in the friction material composition in addition to the above mentioned graphite is preferably 10-18 weight % relative to the entire amount of the friction material composition, more preferably 11-16 weight % relative to the entire amount of the friction material composition.

[0042] As the inorganic friction modifier, other than the above-identified trimanganese tetraoxide, either one of a calcium hydroxide, a calcium carbonate, a barium sulfate, a talc, a dolomite, a zeolite, a triiron tetroxide, a calcium silicate hydrate, a magnesium oxide, a silicon dioxide, a zirconium oxide, a zirconium silicate, a γ-alumina, an α-alumina, a silicon carbide, a columnar titanate, a platy titanate, a particulate titanate, a squamous titanate, an indeterminate titanate with multiple projections, where the titanate may be such as a potassium titanate, a lithium potassium titanate, a magnesium potassium titanate, and a sodium titanate, a wollastonite, a sepiolite, a basalt fiber, a glass fiber, a biosoluble ceramic fiber, or a rock wool, or a combination of two or more of the above-identified inorganic friction modifier may be used.

[0043] The amount of the inorganic friction modifier together with the above-identified trimanganese tetraoxide contained in the friction material composition is preferably 60-82 weight % relative to the entire amount of the friction material composition, more preferably 65-76 weight % relative to the entire amount of the friction material composition.

[0044] As the organic friction modifier, either one of the organic friction modifiers that are generally used for the friction material such as a cashew dust, a tire tread rubber pulverized powder, a polytetrafluoroethylene powder, vulcanized rubbers or unvulcanized rubbers such as an acrylic rubber, an isoprene rubber, a nitrile butadiene rubber, a styrene-butadiene rubber, a butyl rubber, and a silicone rubber, or a combination of two or more of the above-identified organic friction modifiers may be used.

[0045] The amount of the organic friction modifier contained in the friction material composition is preferably 3-8 weight % relative to the entire amount of the friction material composition, more preferably 5-7 weight % relative to the entire amount of the friction material composition.

<Manufacturing Method for Disc Brake Pad>

[0046] The disc brake pad according to this invention is typically manufactured through a mixing step for uniformly mixing the predetermined amount of the friction material composition (raw friction material) by a mixer to obtain a raw friction material mixture, a heat press forming step for positioning the obtained raw friction material mixture superposed on a prewashed, surface-treated, and adhesive-coated back plate in a heat forming die to heat press the raw friction material mixture on the back plate to obtain a heat press formed article, a heating step for heating to cause a curing reaction of the heat press formed article to obtain a cured article, a coating step for coating the cured article such as by spray coating and electrostatic powder coating, a baking step for baking the coating to obtain a baked article, and a grinding step for grinding the baked article by a rotary grinder to form a friction surface.

[0047] Further, after the heat press forming step, a heat treatment step, which is a combination of the coating step and the baking step, and then the grinding step may follow respectively.

[0048] Also, as appropriate, prior to the heat press forming step, a granulating step for granulating the raw friction material mixture, a kneading step for kneading the raw friction material mixture, and a pre-forming step for forming a pre-formed article by positioning the raw friction material mixture or the granulated article obtained through the granulating step or the kneaded article obtained through the kneading step, may be performed, and a scorching step may be performed after the heat press forming step.

<Stainless Steel Disc Rotor>

[0049] As the stainless steel disc rotor, for example, a martensite type stainless steel disc rotor or a ferrite type stainless steel disc rotor may be used.

EMBODIMENTS

[0050] This invention is explained concretely using the Embodiments and the Comparative Examples of this invention in the following sections; however, this invention is not limited to the following Embodiments.

[Manufacturing Method for the Friction Material According to Embodiments 1-11 and Comparative Examples 1-2]

[0051] The friction material composition shown in Table 1 is positioned in the Loedige mixer to be mixed for about 5 minutes and is pressed in a pre-forming die under 30 MPa for about 10 seconds to obtain the pre-formed article. The pre-formed article is superposed on the steel back plate, which is pre-washed, surface treated, and adhesive coated, to be heat-pressed in the heat forming die at 150 centigrade under the forming pressure of 40 MPa for about 10 minutes, then the heat treatment (postcure treatment) at 200 centigrade is performed for about 5 hours, and the grinding step is performed to form the friction surface, thereby obtaining the disc brake pad for a passenger car.

TABLE-US-00001 TABLE 1 comparative embodiments examples 1 2 3 4 5 6 7 8 9 10 11 12 13 binder straight phenol resin 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 fiber base aramid fiber 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 friction lubricant carbonaceous graphite sheet 6.0 6.0 6.0 6.0 6.0 0.5 1.0 4.0 8.0 10.0 11.0 6.0 6.0 modifier lubricants pulverized powder 5.0 5.0 5.0 5.0 5.0 10.5 10.0 7.0 3.0 1.0 1.0 5.0 5.0 petroleum coke metal sulfide zinc sulfide 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 lubricants inorganic friction zirconium oxide 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 modifier zirconium silicate 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 magnesium oxide 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 trimanganese 1.0 2.0 3.0 5.0 6.0 3.0 3.0 3.0 3.0 3.0 3.0 0.5 7.0 tetroxide lithium potassium 22.0 22.0 22.0 22.0 22.0 20.0 20.0 20.0 20.0 20.0 20.0 22.0 22.0 titanate calcium hydroxide 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 barium sulfate 24.0 23.0 22.0 20.0 19.0 24.0 24.0 24.0 24.0 24.0 23.0 24.5 18.0 organic friction cashew dust 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 modifier tire tread rubber 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 pulverized powder total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

[0052] Furthermore, test pieces of the Embodiments 1-11 and the Comparative Examples 1-2 are prepared by cutting the friction material for the disc brake pad into 25 mm×15 mm×15 mm pieces

[0053] Table 2 shows the “Testing Condition”, “Material of Mating Member”, “Evaluation Items”, and “Evaluation Standard” used to examine the formation of the lump of the metal on the disc rotor friction surface and the stability of the braking effect.

TABLE-US-00002 TABLE 2 forming a metal lump on a disc rotor friction surface stability of braking effectiveness testing condition based on JASO C406 friction based on JASO C406 friction tester (1/10 scale tester) tester (1/10 scale tester) material of the martensitic stainless steel martensitic stainless steel mating member evaluation Items existence or non-existence and size changes relative to μ level of metal lump on the surface of the of the base material × cast iron mating member after JASO-C406 at JASO-C406 friction testing friction material abrasion testing evaluation E no metal lump 0.38 with tolarence of less than ±5% Standard G metal lump (less than 0.5 mm) 0.38 with tolerance of more than ±5% but less than ±10% P metal lump (0.5 mm or 0.38 with tolerance of ±10% more but less than 1 mm) or more but less than ±15% F metal lump (1 mm or more) 0.38 with tolerance of ±15% or more

[0054] Table 3 shows the evaluation result of the respective Embodiments and Comparative Examples with respect to the formation of the lump of the metal on the disc rotor friction surface and the stability of the braking effect shown in the Table 2.

TABLE-US-00003 TABLE 3 comparative embodiments examples 1 2 3 4 5 6 7 8 9 10 11 12 13 evaluation result forming a metal lump on a disc P G E E E P G E E E E F E rotor friction surface stability of braking effectiveness E E E E P E E E E G P E F E = excellent G = good P = pass F = fail

[0055] From the Table 3, it can be seen that the friction material satisfying the conditions of this invention inhibits the formation of the lump of the disc rotor friction surface and provides the stability in the braking effect

INDUSTRIAL APPLICABILITY

[0056] With respect to the friction pair, being consisting of the disc brake pad having the friction material manufactured from the friction material composition containing the binder, the fiber base material, and the friction modifier but not containing the copper component and the ferrous-based metal fiber and the stainless steel disc rotor, this invention can provide the friction pair that inhibits the formation of the lump of the metal on the disc rotor friction surface, provides the excellent stability of the braking effect, and provides the excellent practical value.