JP2019214732A - Friction material composition, and friction material and friction member each using the friction material composition - Google Patents

Abstract

To provide a friction material that contains no copper or has a copper content of 0.5 mass% or less and holds a sufficient friction coefficient under high-speed fading condition in which rapid braking at deceleration of 0.8 G from high speed of 200 km/h is repeated with abnormal rise of brake temperature.SOLUTION: A friction material composition is provided that includes a binding agent, an organic filler, an inorganic filler and a fiber base material, the friction material composition further contains 2-5 mass% of a steel fiber including no copper as an element or having a copper content of 0.5 mass% or less, and having a fiber length of 800 μm or more.SELECTED DRAWING: None

Description

  The present invention relates to a friction material composition suitable for a friction material such as a disc brake pad used for braking an automobile or the like, and a friction material using the friction material composition.

  In automobiles and the like, friction materials such as disc brake pads and brake linings are used for braking. The friction material plays a role of braking by rubbing with a facing material such as a disk rotor or a brake drum. Therefore, the friction material is required to have a good friction coefficient, abrasion resistance (the life of the friction material is long), strength, sound vibration (there is less occurrence of brake noise and abnormal noise), and the like. The coefficient of friction is required to be stable regardless of the vehicle speed, deceleration and brake temperature. Further, in recent years, even under severe braking conditions in which the brake temperature becomes abnormally high due to continuous high-speed (vehicle speed of 200 km / h or more) and high deceleration (0.8 G or more) braking, the reduction in the friction coefficient is small. That (high-speed fade characteristics) is required for the friction material.

  In recent years, copper used in friction materials has been scattered as brake wear powder, causing rivers, lakes, marine pollution, and the like. Copper is blended in a friction material in the form of fiber or powder, and is an effective component for maintaining a friction coefficient under high-temperature braking conditions (fade resistance) and improving wear resistance at high temperatures. Therefore, in a composition containing no copper, there has been a problem that the above-mentioned high-speed fade characteristics are extremely deteriorated.

  In the course of restricting the use of copper, as a measure for improving friction characteristics at high temperatures in a composition containing no copper, at least one kind of a titanate compound having a plurality of convex portions and a biosoluble inorganic material Friction material containing fibers (Patent Document 1), a specific amount of binder, organic fiber, metal sulfide-based lubricant, carbonaceous lubricant, titanate, mild / hard abrasive, organic friction modifier, pH A friction material containing a regulator (Patent Document 2) has been proposed.

JP 2013-076058 A JP 2014-156589 A

  Patent Documents 1 and 2 both relate to a friction material having a composition containing no copper, but all of the friction materials have a problem that the effect of improving high-speed fade characteristics at a vehicle speed of 200 km / h or more is not sufficient. The present invention has been made in view of the above circumstances, and repeats rapid braking at a deceleration of 0.8 G from a high speed of 200 km / h to maintain a sufficient friction coefficient even in a high-speed fade condition accompanied by an abnormal increase in brake temperature. That is the task. In particular, it is an object of the present invention to provide a friction material composition which does not contain copper or has a copper content of 0.5% by mass or less and which exhibits high high-speed fade characteristics, which deteriorates high-speed fade characteristics.

  The present inventors have found that by including a steel fiber having a long fiber length in a specific amount in a friction material, it is effective only for maintaining a friction coefficient under a high-speed fade condition even in a composition containing no environmentally harmful copper. And found that the wear resistance at low temperatures was good. In other words, under severe friction conditions such as high-speed fade conditions where the friction material surface is incinerated at high temperatures and shearing force is applied by friction, steel fibers with a long fiber length have a high reinforcing effect on the ash layer, As a result, it is advantageous for maintaining the friction coefficient. However, if a large amount of steel fiber having a long fiber length is added, the wear resistance at low temperature is deteriorated due to cohesive wear between the steel fiber and cast iron as a friction facing material. Therefore, by adding a steel fiber having a long fiber length in a specific addition amount range, not only a high friction coefficient is exhibited under high-speed fade conditions, but also low-temperature wear resistance is improved.

  The friction material composition of the present invention based on these findings is a friction material composition containing a binder, an organic filler, an inorganic filler and a fiber base material, and contains copper as an element in the friction material composition. It is characterized by containing no copper or not more than 0.5% by mass of copper and 2 to 5% by mass of steel fibers having a fiber length of 800 μm or more.

  In the friction material composition of the present invention, the steel fiber preferably has a fiber shape of a curl, and the steel fiber preferably has an average fiber diameter of 60 μm or more.

  The friction material of the present invention is characterized by being formed by molding the above-mentioned friction material composition, and the friction member of the present invention comprises a friction material formed by molding the above-described friction material composition and a back metal. It is characterized by being formed using.

  According to the present invention, when it is used for a friction material such as a disc brake pad for an automobile, a composition that does not use copper, which has a particularly high environmental load, or a copper content of 0.5% by mass, even when copper is contained, Even if the composition is small, it is possible to provide a friction material composition, a friction material, and a friction member having a high friction coefficient under high-speed fade conditions and excellent low-temperature wear resistance.

  Hereinafter, the friction material composition of the present invention, a friction material using the same, and a friction member will be described in detail. The friction material composition of the present invention is a so-called non-asbestos friction material composition containing no asbestos.

[Friction material composition]
The friction material composition of the present embodiment does not contain copper, or even when copper is contained, is a small amount of 0.5% by mass or less.

(Steel fiber)
The friction material composition of the present invention contains steel fibers having a fiber length of 800 µm or more at 2 to 5% by mass. Steel fibers having a long fiber length have a high effect of reinforcing the ashed layer and are effective in maintaining the friction coefficient. The steel fiber having a fiber length of 800 μm or more preferably has a fiber length of 1000 μm or less because the reinforcing effect of the ashed layer beyond 1000 μm becomes poor. More preferably, the fiber length of the steel fiber is 3000 to 8000 μm.

  Steel fibers include straight fibers obtained by chatter vibration cutting and the like, and curled fibers obtained by cutting long fibers. While straight fibers have a straight fiber shape, curled fibers have a curved shape, and include simple arcs, undulations, spirals or spirals, and the like. . Steel fibers with a fiber length of 800 µm or more, whether straight or curled, diffuse frictional heat at the frictional interface and not only suppress uneven temperature rise, but also generate at the frictional interface. This has the effect of appropriately cleaning the organic decomposition products that occur, so that the fluctuation of the brake torque generated during braking is reduced, and it is possible to suppress and suppress the occurrence of brake vibration. However, the curled fibers are preferable because they are less likely to fall off from the friction material at the friction interface and can more effectively maintain the friction characteristics under high-speed fade conditions. Further, it is more preferable that the curled fibers include a portion having a radius of curvature of 100 μm or less, since the fixation to the friction material becomes stronger and the friction material is less likely to fall off at the friction interface. As the curled steel fiber, for example, a commercially available one such as cut wool manufactured by Nippon Steel Wool Co., Ltd. can be used.

  The average fiber diameter of the steel fibers in the friction material composition is preferably 60 μm or more from the viewpoint of maintaining the friction coefficient under high-speed fade conditions. Further, as the average fiber diameter of the steel fibers increases, the reinforcing effect of the ashed layer increases by that amount. Therefore, it is more preferable that the thickness exceeds 100 μm. On the other hand, when the thickness is excessively large, the number of steel fibers is reduced, and the reinforcing effect of the ashed layer is rather reduced. For this reason, it is preferable that the average fiber diameter of the steel fibers be 500 μm or less. The more preferable thickness of the steel fiber is 100 to 300 μm.

  The fiber length and average fiber diameter of the steel fiber can be confirmed with a microscope or the like. Regarding the fiber length and average fiber diameter of the steel fiber contained in the friction material, the friction material is heated at 800 ° C. in an air stream, and the iron fiber is observed from the remaining ash by using an electron beam microanalyzer (EPMA) or the like to observe the Fe component. Can be confirmed. Alternatively, the ash content may be separated by magnetic separation and observed by a micro soup, an electron beam micro analyzer (EPMA), or the like.

  Further, by setting the content of the steel fiber to 2 to 5% by mass, it is possible to simultaneously maintain the friction coefficient under high-speed fading conditions and improve the low-temperature wear resistance. If the content of steel fiber is less than 2% by mass, the effect of reinforcing the friction material surface under high-speed fading conditions is insufficient. And the wear resistance at low temperatures deteriorates. The content of the steel fiber in the friction material composition or the friction material can be determined, for example, by quantitatively analyzing the Fe component in an arbitrary cross section of the friction material using an electron beam microanalyzer (EPMA) or the like. In this case, when the friction material does not contain an Fe component other than the steel fiber, the quantitative analysis value is the content of the steel fiber as it is. When the friction material contains an Fe component (iron powder or the like) other than steel fiber, the total Fe amount of the steel fiber and other Fe components in the field of view of an arbitrary cross section to be observed is measured as a quantitative analysis value. However, in this case, the area ratio between the steel fiber and the Fe component other than the steel fiber in the observation field of view was measured, and the ratio of the area ratio of the steel fiber to the total area ratio of the steel fiber and the Fe component other than the steel fiber was determined. By calculating the product of the total amount of Fe analyzed quantitatively, the content of the steel fiber can be easily obtained.

(Binder)
The binder integrates the organic filler, the inorganic filler, the fiber base material, and the like contained in the friction material composition to give strength. There is no particular limitation on the binder contained in the friction material composition of the present invention, and a thermosetting resin which is usually used as a binder of a friction material can be used.

  Examples of the thermosetting resin include phenol resins; various elastomer-dispersed phenol resins such as acrylic elastomer-dispersed phenol resins and silicone elastomer-dispersed phenol resins; acrylic-modified phenol resins, silicone-modified phenol resins, cashew-modified phenol resins, and epoxy-modified phenols. Examples include resins and various modified phenol resins such as alkylbenzene-modified phenol resins, and these can be used alone or in combination of two or more. In particular, it is preferable to use a phenolic resin, an acrylic-modified phenolic resin, a silicone-modified phenolic resin, or an alkylbenzene-modified phenolic resin in order to give good heat resistance, moldability and friction coefficient.

  The content of the binder in the friction material composition of the present invention is preferably 5 to 20% by mass, and more preferably 5 to 10% by mass. When the content of the binder is in the range of 5 to 20% by mass, the decrease in the strength of the friction material can be further suppressed, and the porosity of the friction material decreases, and the noise such as squealing due to the increase in the elastic modulus can be reduced. Vibration performance deterioration can be further suppressed.

(Organic filler)
The organic filler is included as a friction modifier for improving the sound vibration performance and wear resistance of the friction material. The organic filler contained in the friction material composition of the present invention is not particularly limited as long as it can exhibit the above-described performance, and usually, cashew dust, a rubber component, or the like, which is used as an organic filler, can be used. .

  The cashew dust may be any one that is usually used as a friction material, obtained by pulverizing hardened cashew nut shell oil.

  Examples of the rubber component include tire rubber, acrylic rubber, isoprene rubber, NBR (nitrile butadiene rubber), SBR (styrene butadiene rubber), chlorinated butyl rubber, butyl rubber, silicone rubber, and the like. Used in combination of more than one type.

  The content of the organic filler in the friction material composition of the present invention is preferably 1 to 20% by mass, more preferably 1 to 10% by mass, and more preferably 3 to 8% by mass. Particularly preferred. By setting the content of the organic filler in the range of 1 to 20% by mass, it is possible to avoid an increase in the elastic modulus of the friction material, a deterioration in sound and vibration performance such as squeal, and a deterioration in heat resistance and heat. A decrease in strength due to history can be avoided.

(Inorganic filler)
The inorganic filler is included as a friction modifier added for the purpose of improving the friction coefficient in order to avoid deterioration of the heat resistance of the friction material and to improve the wear resistance. The composition for a non-asbestos friction material of the present invention is not particularly limited as long as it is an inorganic filler usually used for a friction material.

  Examples of the inorganic filler include tin sulfide, bismuth sulfide, molybdenum disulfide, iron sulfide, antimony trisulfide, zinc sulfide, calcium hydroxide, calcium oxide, sodium carbonate, barium sulfate, coke, mica, vermiculite, and calcium sulfate. , Talc, clay, zeolite, mullite, chromite, titanium oxide, magnesium oxide, silica, dolomite, calcium carbonate, magnesium carbonate, granular or plate-like titanate, zirconium silicate, gamma alumina, manganese dioxide, zinc oxide, 43 Iron oxide, cerium oxide, zirconia, graphite and the like can be used, and these can be used alone or in combination of two or more. As the granular or plate-like titanate, potassium hexatitanate, potassium octa titanate, lithium potassium titanate, potassium magnesium titanate, sodium titanate, or the like can be used.

  The content of the inorganic filler in the friction material composition of the present invention is preferably 30 to 80% by mass, more preferably 40 to 70% by mass, and preferably 50 to 60% by mass. Particularly preferred. By setting the content of the inorganic filler in the range of 30 to 80% by mass, deterioration of heat resistance can be avoided, and this is also preferable in terms of the balance of the content of other components of the friction material.

(Fiber base material)
The fiber base material has a reinforcing effect on the friction material. The friction material composition of the present invention is generally used as a fiber base material, inorganic fibers, metal fibers, organic fibers, carbon-based fibers, and the like can be used, and these may be used alone or in combination of two or more. be able to.

As the inorganic fibers, ceramic fibers, biodegradable ceramic fibers, mineral fibers, glass fibers, silicate fibers, and the like can be used, and one or a combination of two or more can be used. Among these inorganic fibers, biodegradable mineral fibers containing SiO ₂ , Al ₂ O ₃ , CaO, MgO, FeO, Na ₂ O, and the like in any combination are preferable, and as a commercially available product, LAPINUS FIBERS B.R. V-made Roxul series.

  The metal fiber is not particularly limited as long as it is generally used for a friction material, and examples thereof include metals or alloys such as aluminum, iron, cast iron, zinc, tin, titanium, nickel, magnesium, silicon, copper, and brass. Can be used. These metals or alloys may be contained in the form of powder in addition to the fiber form. However, it is preferable that copper and an alloy containing copper are not contained from the viewpoint of environmental harm.

  As the organic fibers, aramid fibers, cellulose fibers, acrylic fibers, phenol resin fibers, and the like can be used, and these can be used alone or in combination of two or more.

  As the carbon-based fiber, flame-resistant fiber, pitch-based carbon fiber, PAN-based carbon fiber, activated carbon fiber and the like can be used, and these can be used alone or in combination of two or more.

  The content of the fiber base material in the friction material composition of the present invention is preferably 5 to 40% by mass, more preferably 5 to 20% by mass, and more preferably 5 to 15% by mass in the friction material composition. Is particularly preferred. By setting the content of the fiber base material in the range of 5 to 40% by mass, an optimum porosity as a friction material can be obtained, squeak can be prevented, appropriate material strength can be obtained, and abrasion resistance can be obtained. And moldability can be improved.

[Friction material]
The friction material of the present embodiment can be produced by molding the friction material composition of the present invention by a generally used method, and is preferably produced by heat and pressure molding. In detail, for example, the friction material composition of the present invention is homogenized using a mixer such as a Reidige mixer (“Reidge” is a registered trademark), a pressure kneader, and an Eirich mixer (“Eirich” is a registered trademark). The mixture is preliminarily molded in a molding die, and the obtained preform is molded under the conditions of a molding temperature of 130 to 160 ° C., a molding pressure of 20 to 50 MPa, and a molding time of 2 to 10 minutes. It is manufactured by heat-treating the molded product at 150 to 250 ° C. for 2 to 10 hours. Further, it is manufactured by performing painting, scorch treatment, and polishing treatment as necessary.

[Friction member]
The friction member of the present embodiment uses the above-described friction material of the present embodiment as a friction material serving as a friction surface. Examples of the above-mentioned friction member include the following configurations.
(1) Configuration of only friction material.
(2) A structure including a back metal and a friction material formed of the friction material composition of the present invention to be a friction surface on the back metal.
(3) In the configuration of the above (2), between the back metal and the friction material, a primer layer for the purpose of surface modification for enhancing the bonding effect of the back metal, and for the purpose of bonding the back metal and the friction material. A structure in which an adhesive layer is further interposed.

  The back metal is usually used as a friction member for improving the mechanical strength of the friction member, and the material is metal, fiber reinforced plastic, or the like, specifically, iron, stainless steel, inorganic fiber reinforced plastic. And carbon fiber reinforced plastics. The primer layer and the adhesive layer may be those that are usually used for a friction member such as a brake shoe.

  The friction material composition of the present embodiment does not contain copper, which is an environmentally harmful substance, and has excellent friction coefficient retention under high-speed fading conditions. Therefore, the friction material composition is particularly useful as an overlay material such as a disc brake pad or a brake lining of an automobile. However, it can also be formed and used as a lining material for a friction member. Note that “upper material” is a friction material serving as a friction surface of a friction member, and “lower material” is a friction material interposed between a friction material serving as a friction surface of a friction member and a back metal. It is a layer for the purpose of improving shear strength, crack resistance and the like near the bonding portion with the back metal.

  Hereinafter, the friction material composition, the friction material, and the friction member of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[Examples 1-2 and Comparative Examples 1-3]
(Production of disc brake pads)
The materials were blended according to the blending ratios shown in Table 1 to obtain the friction material compositions of Examples 1 and 2 and Comparative Examples 1 to 3. The mixing ratio in the table is% by mass. As the steel fiber used in the examples and comparative examples, “3L-80” (curled, fiber length 900 to 5500 μm, average fiber diameter 106 μm) manufactured by SINOMA was used. The fiber length was measured by measuring the fiber length of 100 fibers using a microscope manufactured by Keyence Corporation. The average fiber diameter was determined by measuring the fiber diameter of 50 fibers using a microscope manufactured by Keyence Corporation, and the average value was defined as the average fiber diameter.

This friction material composition was mixed with a Lodige mixer (Mazbo Co., Ltd., trade name: Lodige mixer M20), and the obtained mixture was preformed by a molding press (Oji Machine Industry Co., Ltd.). The resulting preform was molded using a molding press (manufactured by Sanki Seiko Co., Ltd.) under the conditions of a molding temperature of 140 to 160 ° C., a molding pressure of 30 MPa, and a molding time of 5 minutes. Together with the heat and pressure molding. The obtained molded product was heat-treated at 200 ° C. for 4.5 hours, polished using a rotary polisher, and scorched at 500 ° C. to obtain disc brake pads of Examples 1-2 and Comparative Examples 1-3. Obtained. In the examples and comparative examples, disk brake pads having a back metal thickness of 6 mm, a friction material thickness of 11 mm, and a friction material projection area of 52 cm ² were produced.

(Evaluation of fast fade characteristics)
The disc brake pads of Examples 1 and 2 and Comparative Examples 1 to 3 prepared by the above method were evaluated for high-speed fade characteristics using a brake dynamo tester. In the experiment, a general pin-slide type collet caliper and a ventilated disc rotor (FC190) manufactured by Kiriu Co., Ltd. were used to evaluate the moment of inertia of the Skyline V35 manufactured by Nissan Motor Co., Ltd. After performing the fitting according to JASO C427 (initial speed 50 km / h, final speed 0 km / h, deceleration 0.3 G, brake temperature before braking 100 ° C, braking 200 times), a high-speed fade test (initial speed 200 km / h) h, final speed 80 km / h, deceleration 0.8 G, braking 10 times at 60-second intervals at a braking temperature of 100 ° C. before the first braking), and the minimum value of the friction coefficient in the high-speed fade test (one braking) (The minimum value of the average value of the average friction coefficient).

(Evaluation of wear resistance at low temperature)
The abrasion resistance was measured based on the Japan Society of Automotive Engineers Standard JASO C427, and the wear amount of a friction material equivalent to 1,000 times of braking at a brake temperature of 100 ° C., a vehicle speed of 50 km / h, and a deceleration of 0.3 G was evaluated. Abrasion was considered.

These evaluations were performed using a dynamometer at an inertia of 7 kgf · m · sec ² . Further, a ventilated disk rotor (manufactured by Kiriu Co., Ltd., material FC190) and a general pin-slide type collet type caliper were used.

  Examples 1 and 2, which did not contain copper and contained steel fibers having a fiber length of 800 µm or more in a range of 2 to 5% by mass, exhibited high-speed fade characteristics equal to or higher than Comparative Example 3 containing copper. Further, it exhibited excellent high-speed fade characteristics as compared with Comparative Example 1 which did not contain steel fibers having a fiber length of 800 μm or more. Furthermore, the amount of wear at low temperature is smaller than Comparative Example 3 in which the content of steel fibers having a fiber length of 800 μm or more exceeds 5%. As described above, Examples 1 and 2 containing steel fibers having a fiber length of 800 μm or more in the range of 2 to 5% by mass are excellent in that high-speed fade characteristics and low-temperature abrasion resistance are both achieved without containing copper. It is clear.

  Compared with conventional products, the friction material composition of the present invention is a composition that does not use copper, which has a particularly high environmental load, has a high friction coefficient under high-speed fade conditions, and has excellent wear resistance at low temperatures. The composition is suitable for friction materials and friction members such as brake pads for passenger cars.

Claims (5)

A friction material composition comprising a binder, an organic filler, an inorganic filler and a fiber base material,
The friction material composition does not contain copper as an element, or has a copper content of 0.5% by mass or less,
A friction material composition comprising 2 to 5% by mass of a steel fiber having a fiber length of 800 µm or more.   The friction material composition according to claim 1, wherein the steel fiber has a curl shape.   The friction material composition according to claim 1, wherein the steel fibers have an average fiber diameter of 60 μm or more.   A friction material obtained by molding the friction material composition according to claim 1.   A friction member formed using a friction material obtained by molding the friction material composition according to claim 1 and a back metal.