Friction lining composition for couplings of wind turbines and friction lining

Description

[0001] The invention relates to a friction lining or a friction lining mixture or a friction lining material, in particular for clutch linings and clutch discs of wind turbines, as well as a composite of a support body with a friction layer and the use of the composite for clutch linings.

[0002] Such friction materials are needed, for example, for brake and clutch linings, e.g., for use in wind turbines, but also in motor vehicles and rail vehicles. Furthermore, there are numerous other applications for such friction materials. Known friction material formulations generally have the following schematic structure: Metal fibers and / or powders; Functional fillers (e.g., glass fibers for reinforcement, metal oxides as friction enhancers, etc.); Solid lubricants; Organic compounds (resins, rubber, fibers, etc.)

[0003] In addition to the technical requirements for friction material development, such as the usual increase in performance, service life and operating parameters, the requirements regarding environmental protection are becoming increasingly important in friction material development.

[0004] EP 0 654 616 B1 discloses a friction lining compound for brake and clutch linings which contains tin sulfides instead of the previously used antimony sulfides to reduce the susceptibility of the friction partner to cracking. The use of tin sulfides instead of the previously used antimony sulfides in the friction lining compound is intended to reduce the surface cracking susceptibility of the friction partner that occurs under high peak temperature loads.

[0005] According to the patent document with publication number DD-208 829 B1, the use of soapstone or talc is known, with starting materials containing 79% Cu, 7% Sn, 9% soapstone.

[0006] Patent document DE-1164305 discloses a method for producing a ceramic friction element.

[0007] European patent EP 0 093 673 B1 describes an iron-based friction lining compound. In addition to 72 to 85% by weight of powdered iron, the friction lining compound comprises 3 to 14% by weight of graphite, 2 to 12% by weight of coke, 3 to 10% by weight of a low-melting-point material such as tin, and up to 3% by weight of friction-modifying additive. During the manufacture of the brake lining from this mixture, the iron and tin fuse to form an alloy, creating a matrix in which the graphite, coke, and additive are embedded in a relatively fixed position. According to this document, the ratio of iron powder to tin should be approximately 12 to 1.

[0008] Patent document CZ 278 738 B6 describes a bronze-based metal-ceramic friction material, particularly for dry friction applications, produced by powder metallurgy processes. The friction material contains 50 to 65 wt.% copper (Cu), 3 to 7 wt.% tin (Sn), 4 to 10 wt.% iron (Fe), 8 to 13 wt.% graphite (C), 4 to 6 wt.% talc (Mg 3 (Si 4 O 10) (OH) 2), and 6 to 15 wt.% zirconium silicate (ZrSiO 4).

[0009] The demands placed on couplings in wind turbines are increasing due to the ever-growing size of the turbines. Therefore, coupling discs with a higher coefficient of friction are needed, which improves torque transmission and enables smaller, and thus more cost-effective, coupling designs. It would therefore be desirable to provide a friction material and a coupling disc with a stable coefficient of friction, a lower wear rate than currently used materials, and one that does not damage the mating component during operation.

[0010] It is therefore an object of the invention to provide a friction lining mixture suitable for clutch linings of wind turbines and with which a significant increase in the performance of the friction pairing is achieved through higher and more stable frictional torques, which ultimately results in greater reliability and service life.

[0011] This problem is solved by objects having the features of claims 1 and 5.

[0012] The invention provides a friction lining material based on sintered bronze for clutch linings for wind turbines that interact with a friction partner. The friction lining material comprises a sintered bronze alloy with a copper content of 60 wt.% to 95 wt.%, preferably 80 wt.% to 95 wt.%. The sintered bronze includes metallic tin to increase the coefficient of friction with a weight fraction of 5 wt.% to 40 wt.%, preferably 10 wt.% to 30 wt.%. Talc is further embedded in the sintered bronze as a solid lubricant with a weight fraction of 2 wt.% to 15 wt.%, preferably 2.5 wt.% to 7.5 wt.%. The sum of the components amounts to 100% wt.%, wherein the talc has particle sizes between 10 µm and 1000 µm, preferably between 100 µm and 800 µm and more preferably between 200 µm and 600 µm.

[0013] The overall goal is a sintered bronze with a metal matrix of Cu: 60-95% and Sn: 5-40%, in which a solid lubricant content of talc of 2-15% is embedded. By using talc with grain sizes of 10 µm - 1000 µm, the bronze alloy can be modified to achieve a coefficient of friction between µ = 0.40 and µ = 0.65 under typical application loads and speeds. Here and in the following, the coefficient of friction µ is always understood to be the static coefficient of friction µH, as the present invention is directed towards coupling applications. The coefficient of friction µH is always specified against steel as the friction partner. Furthermore, an increase in wear resistance was achieved compared to known materials. The relatively large grain sizes of the talc allow for better distribution of the solid lubricant.

[0014] It is not claimed that the friction lining material is produced by sintering copper and tin as elemental powders, preferably with a dendritic grain shape, with talc as a solid lubricant. The sliding layer powder mixture can be applied to a support body of precisely defined weight and thickness. This support body is pre-sintered with the sliding layer powder in a metallurgical furnace at a defined temperature, approximately 800 °C, under a protective atmosphere, and subsequently pressed or, preferably, hot-rolled under precise temperature control and sintered. The resulting composite can be further densified by subsequent pressing or, preferably, cold rolling, thereby achieving a wear-resistant, high-density composite of support body and sliding / friction layer.

[0015] It is not claimed that the friction lining material, due to its increased tin content, exhibits a coefficient of friction between µ=0.40 and µ=0.65 with respect to steel. In principle, cast iron or ceramic can also be used as the friction partner. However, the material of the friction partner is not of paramount importance, as the friction lining material is transferred to the mating surface, forming a so-called transfer film. This film ensures that a large portion of the friction occurs as a friction pair. Due to the transfer film, which is more pronounced and uniform due to the high tin content, no damage occurs to the mating surface. The coefficient of friction should be measured according to DIN ISO 7148-2 between µ=0.40 and µ=0.65, for which a plate test rig can be used.

[0016] In one embodiment of the friction lining material, the metal matrix consists of 79 to 85 wt.%, preferably 80.55 wt.% copper and 10 to 14 wt.%, preferably 12.04 wt.% tin, wherein the alloy has a solid lubricant content of 6 to 9 wt.%, preferably 7.4 wt.% talc. This mixture has proven suitable in friction tests and advantageous compared to known friction lining materials.

[0017] In another embodiment of the friction lining material, the metal matrix consists of 79 to 88 wt.%, preferably 84.47 wt.% copper and 10 to 15 wt.%, preferably 12.62 wt.% tin, wherein the alloy has a solid lubricant content of 1.5 to 4.5 wt.%, preferably 2.9 wt.% talc. This mixture also exhibits advantageous properties in friction tests.

[0018] In another embodiment of the friction lining material, the metal matrix consists of 60 to 70 wt.%, preferably 62 to 67 wt.% copper and 30 to 40 wt.%, preferably 32 to 37 wt.% tin, wherein the alloy has a solid lubricant content of 1.5 to 4.5 wt.%, preferably 2.5 to 4 wt.% talc.

[0019] According to a further aspect of the present invention, a high-density composite is provided comprising a metallic support body from the group consisting of steel, stainless steel or copper and a sliding / friction layer of a sintered bronze layer with copper having a weight percent content of 60 wt.% - 95 wt.% and tin having a weight percent content of 5 wt.% - 40 wt.%, wherein the solid lubricant content of talc is 1.5 wt.% - 15 wt.%, wherein the talc has particle sizes between 10 µm - 1000 µm, preferably between 100 µm and 800 µm and more preferably between 200 µm and 600 µm, wherein the composite is a coupling or a coupling lining for a wind turbine or a brake lining for a wind turbine.

[0020] It is not claimed that the high-density composite comprises any of the friction lining materials described above.

[0021] In one exemplary embodiment of the composite, the friction lining material is sintered onto the support body as a sliding layer powder. The sintering process can be carried out, for example, as press sintering or, preferably, as hot pressing. In a further preferred embodiment of the composite, the friction lining material, in powder form, is sintered onto the support body using a hot rolling process.

[0022] It is not claimed that the above-described compound will be used for clutch linings with increased coefficients of friction between µ=0.40 and µ=0.65.

[0023] The present invention is illustrated below by means of exemplary representations of the present invention.

[0024] Figure 1 shows a section through a specimen with an associated scale.

[0025] Figure 1shows an etched fine section along a cross-section through a specimen, where the copper Cu and tin Sn are visible due to the etching. Figure 1 The figure below shows a light-colored support body 8. The friction material 6 is visible on the support body. Above the friction material 6, the plastic 4 is visible, in which the sample was embedded for fine grinding. The friction material has a fine-grained structure. The large, continuous black areas are formed by talc grains 12, which are embedded in the sintered bronze as a lubricant.

[0026] An exemplary composition of a friction lining material comprises a metal matrix of 60 to 70 wt.%, preferably 62 to 67 wt.% copper and 30 to 40 wt.%, preferably 32 to 37 wt.% tin, wherein the alloy has a solid lubricant content of 1.5 to 4.5 wt.%, preferably 2.5 to 4 wt.% talc. This is a very tin-rich alloy that exhibits particularly high adhesive strength and is suitable for clutches, but less suitable as a friction lining material for brake applications.

[0027] A plate- or disc-shaped specimen was tested, subjected to an oscillating transitional motion with a stroke length between 1 and 50 mm. The sliding velocity ranged from 0.003 to 0.03 m / s. A maximum load of 400 kN was applied. The coefficient of friction was measured (primarily) at room temperature. The specimen typically has a diameter of 80 mm, and the maximum specific load is 80 MPa. Wear measurements were performed using eddy current sensors. Force measurements were carried out with two HPM U10 load cells. Temperature measurements were performed on the mating specimen.

[0028] In a first example of the friction lining material according to the invention, a metal matrix consisting of 80.55 wt.% copper and 12.04 wt.% tin was used, the alloy containing 7.4 wt.% talc as a solid lubricant. This mixture proved suitable in friction tests and advantageous compared to known friction lining materials. The coefficient of friction, according to DIN ISO 7148-2, was between µ = 0.40 and µ = 0.65, using a plate test rig as described in the preceding section. The test load was 10–40 MPa.

[0029] In a second example of the friction lining material, a metal matrix consisting of 84.47 wt.% copper and 12.62 wt.% tin was used, with the alloy containing 2.9 wt.% talc as a solid lubricant. This mixture also exhibited advantageous properties in the friction test. The coefficient of friction, according to DIN ISO 7148-2, ranged between µ = 0.40 and µ = 0.65, using a plate test rig.

Claims

1. Friction lining material based on sintered bronze for clutch linings for wind turbines cooperating with a friction partner, in which, as a solid lubricant, 2 wt.-% - 15 wt.-%, preferably 2.5 wt.-% - 7.5 wt.-% talc is embedded, characterized in that the sintered bronze or bronze alloy contains, for increasing the coefficient of friction, metallic tin in a proportion by weight of 5 wt.-% - 40 wt.-%, preferably of 10 wt.-% - 30 wt.-%, wherein the copper content in the bronze alloy is 60 wt.-% - 95 wt.-%, preferably 80 wt.-% - 95 wt.-%, wherein the sum of the constituents adds up to 100 wt.-%, characterized in that the talc has grain sizes between 10 µm and 1000 µm, preferably between 100 µm and 800 µm and more preferably between 200 µm and 600 µm.

2. Friction lining material according to claim 1, characterized in that the metal matrix consists of 79 to 85 wt.-%, preferably 80.55 wt.-% copper, and 10 - 14 wt.-%, preferably 12.04 wt.-% tin, wherein the alloy has a solid lubricant content of 6 - 9 wt.-%, preferably 7.4 wt.-% talc.

3. Friction lining material according to claim 1, characterized in that the metal matrix consists of 79 to 88 wt.-%, preferably 84.47 wt.-% copper, and 10 - 15 wt.-%, preferably 12.62 wt.-% tin, wherein the alloy has a solid lubricant content of 1.5 - 4.5 wt.-%, preferably 2.9 wt.-% talc.

4. Friction lining material according to claim 1, characterized in that the metal matrix consists of 60 to 70 wt.-%, preferably 62 to 67 wt.-% copper, and 30 - 40 wt.-%, preferably 32 to 37 wt.-% tin, wherein the alloy has a solid lubricant content of 1.5 - 4.5 wt.-%, preferably 2.5 to 4 wt.-% talc.

5. Composite of high density, made of a metallic support body selected from the group consisting of steel, stainless steel or copper, and a sliding / friction layer made of a sintered bronze layer having copper in a percentage by weight of 60 wt.-% - 95 wt.-% and tin in a percentage by weight of 5 wt.-% - 40 wt.-%, wherein the solid lubricant content of talc is 1.5 wt.-% - 15 wt.-%, characterized in that the talc has grain sizes between 10 µm and 1000 µm, preferably between 100 µm and 800 µm and more preferably between 200 µm and 600 µm, and wherein the composite is a clutch or a clutch lining for a wind turbine or a brake lining for a wind turbine.

6. Composite according to claim 5, characterized in that the sliding layer powder has been sintered onto the support body, preferably in a hot-rolling process.