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JP-7855738-B2 - Friction material compositions and related friction elements

JP7855738B2JP 7855738 B2JP7855738 B2JP 7855738B2JP-7855738-B2

Inventors

  • シン・シコーラ、アグスティン
  • トロンボット、フラビオ
  • ジェンタ、ダニエレ

Assignees

  • アイティーティー・イタリア・エス．アール．エル

Dates

Publication Date
20260508
Application Date
20230620
Priority Date
20220620

Claims (18)

  1. An asbestos-free friction material composition comprising at least one filler, at least a fibrous material selected from the group consisting of inorganic fibers, organic fibers, metal fibers, and any combination thereof, at least one binder, at least one lubricant, at least one or more abrasives, and at least first and at least second carbonaceous materials, In combination, the first carbonaceous material has a particle size distribution such that it has a D50 greater than 10 μm, - The second carbonaceous material has a particle size distribution such that it has a D50 of less than 10 μm. The at least second carbonaceous material having a D50 of less than 10 μm is selected from a filler made of carbon black. An asbestos-free friction material composition characterized by the following.
  2. The asbestos-free friction material composition according to claim 1, characterized in that at least the first carbonaceous material having a D50 greater than 10 μm is present in an amount in the range of 2 to 6% by weight of the friction material composition, calculated relative to the total weight of the friction material composition.
  3. The asbestos-free friction material composition according to claim 1, characterized in that at least the second carbonaceous material having a D50 of less than 10 μm is present in the composition in an amount ranging from 1 to 4% by weight, calculated relative to the total weight of the friction material composition.
  4. The asbestos-free friction material composition according to claim 1, characterized in that the composition ratio of the first carbonaceous material to the second carbonaceous material is in the range of 1:1 to 6:1.
  5. The asbestos-free friction material composition according to claim 1, characterized in that the at least first carbonaceous material having a D50 greater than 10 μm is selected from the group consisting of graphite, petroleum coke, dry petroleum coke, carbon black, and any mixture thereof.
  6. The asbestos-free friction material composition according to claim 5, characterized in that the at least first carbonaceous material having a D50 greater than 10 μm is graphite.
  7. The asbestos-free friction material composition according to claim 1, characterized in that the at least one fibrous material comprises an organic fiber selected from the group consisting of acrylic fibers, polyaramid fibers, aramid fibers, cellulose fibers, and any mixture thereof; and/or an inorganic or metallic fiber.
  8. The asbestos-free friction material composition according to claim 1, characterized in that the at least one lubricant comprises a sulfide-based lubricant selected from the group consisting of metal sulfides of Sn, Zn, Fe, and Mo, and mixtures thereof.
  9. The asbestos-free friction material composition according to claim 1, characterized in that the at least one or more abrasives include at least one soft abrasive selected from the group consisting of magnesia, chromite, magnetite, hematite, quartz, zinc oxide, tin oxide, barium sulfate, silicate, fluoride, and any mixture thereof, having a Mohs hardness of less than 7.
  10. The asbestos-free friction material composition according to claim 9, characterized in that the at least one or more abrasives include at least one hard abrasive having a Mohs hardness of 7 or greater, and the hard abrasive is selected from the group consisting of zirconia, alumina, corundum, silicon carbide, tungsten carbide, zirconium carbide, zirconium silicate, boron nitride, and any mixture thereof .
  11. The asbestos-free friction material composition according to claim 10 , characterized in that the composition ratio of the soft abrasive to the hard abrasive is in the range of 1:1 to 4:1.
  12. The asbestos-free friction material composition according to claim 1, characterized by not containing copper and not containing any copper alloys.
  13. The asbestos-free friction material composition according to claim 1, characterized by containing at least one metal selected from the group consisting of iron, steel, stainless steel, tin, zinc, and all alloys thereof, excluding copper and copper alloys, in the form of powder or fibers.
  14. The asbestos-free friction material composition according to claim 1, characterized in that the at least one filler is an inorganic filler selected from the group consisting of mineral fibers, glass fibers, rock wool, phyllosilicates (mica, vermiculite, talc), titanate, inorganic hydroxides of Ca, Mg, and K, and any mixture thereof.
  15. The asbestos-free friction material composition according to claim 1, characterized in that it contains the following components in a weight percentage calculated based on the total weight of the friction material composition. Abrasive: Mohs > 7, 15-35 Abrasives Mohs <7 30-60 Resin 6-10 Organic additives 4-8 Organic fibers 2-4 Lubricant 2-8 First carbonaceous component 2-6 Second carbonaceous component 1-4
  16. A friction element having a friction layer made of the friction material composition described in any one of claims 1 to 15 .
  17. The friction element according to claim 16 , characterized in that it is a brake pad or a brake shoe.
  18. A braking device comprising a member to be braked, comprising a brake disc or brake drum made of cast iron or steel, and at least one braking member comprising a brake pad or brake shoe adapted to cooperate with the member to be braked by friction, wherein the braking member is intended to cooperate with the member to be braked and has a friction layer made of a friction material composition according to any one of claims 1 to 15 .

Description

Cross-reference of related applications: This patent application claims priority to Italian Patent Application No. 102022000013012, filed June 20, 2022, the entire disclosure of which is incorporated herein by reference. This invention relates particularly to friction material compositions suitable for manufacturing friction layers/blocks for friction elements, such as braking elements incorporated into vehicle braking systems. The present invention also relates to related friction elements, such as brake pads or brake shoes for vehicles, made from this friction material composition and particularly suitable for electric vehicles, though not limited to them. The friction material composition of the present invention belongs to the so-called NAO ("Non-Asbestos Organic") type, and does not contain asbestos, and, without limitation, does not particularly contain copper. With the rapid development of the modern transportation industry, the number of electric vehicles is increasing day by day. Replacing combustion engines with electric engines results in significantly quieter vehicles. This is leading to greater concern about noise generated by other automotive components, such as brake pads integrated into the braking system. Consequently, brake pads used in electric vehicles require improved NVH (noise, vibration, and harshness) standards for driving comfort, while maintaining, and in some cases improving, braking performance in terms of friction stability, stiction, and corrosion resistance. At the same time, future mobility trends will pay special attention to environmental and health hazards, aiming to reduce the release of particulate matter (PM10 and PM2.5) generated by braking systems, for example. Regarding the operating noise of braking systems, it is known that this phenomenon has a complex and multi-factor origin, and that it depends on vehicle drive vibrations related to the unavoidable assembly gap between braking elements such as brake pads and shoes and their respective supports, as well as on the contact phenomenon that occurs between the sliding parts of the braking elements and the supports during braking system operation. This contact phenomenon is called "creep-grown" and produces an unpleasant, high-intensity, low-frequency noise at very low vehicle speeds. It is a classic example of self-excited braking vibration caused by the so-called "stick-slip" effect, i.e., alternating episodes of sticking or adhesion and subsequent slippage of the brake pads on the brake disc during the braking process. As a result, the coefficient of friction fluctuates continuously between static (stick phase) and dynamic (slip phase) values. Modern vehicles, such as electric vehicles, have a strong need to eliminate, or at least reduce, low-frequency noise in a simple and, especially, economical way. In fact, electric vehicles are far quieter than their internal combustion engine counterparts. In particular, unlike engine-driven vehicles, electric vehicles start up quietly due to the electric motor. Therefore, drivers and passengers are more likely to perceive the aforementioned noise, and may even find it unpleasant. Furthermore, these types of noise can affect the living environment of residents and could become a new source of noise pollution in cities. Various solutions to mitigate this phenomenon are known in the art, but they do not completely solve the problem or introduce further drawbacks. EP0959262 discloses a disc brake pad capable of removing creepgrown using a composition comprising a fibrous substrate (excluding asbestos), a binder, and a friction modifier, wherein the binder is entirely or partially made of a modified silicone resin, and in combination, the friction material composition contains 0.5 to 20 volume percent of zeolite as part of the friction modifier, and the modified silicone resin is contained in the friction material composition in an amount of 3 to 30 volume percent of the total composition. The modified silicone resin is obtained by reacting oil or silicone rubber with a novolac-type phenolic resin. This results in an expensive material and makes manufacturing difficult. Meanwhile, WO2019120648 discloses a hybrid friction lining material and a brake pad made therefrom, in which an attempt is made to combine the positive properties of a steel low-friction lining material (so-called low-steel (LS) friction lining or friction lining material) and an asbestos-free mechanical friction lining material. In a preferred embodiment, such a hybrid friction material comprises 15 to 22% by weight, particularly 17 to 20% by weight, of at least one binder; 5 to 11% by weight, of organic fibers or a mixture of organic fibers; 1 to 20% by weight, particularly 8 to 14% by weight, of at least one other organic compound; 0 or 8 to 16% by weight, of inorganic fibers or a mixture of inorganic fibers; 10 to 40% by weight, of at least one inorganic oxide; 6 to 12% by weight, of at least one inorganic sil