Method for producing a friction element

Abstract

The invention relates to a method for producing a friction element (1) according to which a friction lining is applied onto a support element (2), which friction lining comprises at least one resin (5) and friction-modifying particles (6) and/or fibers (7), wherein the friction-modifying particles (6) and/or fibers (7) are mixed with the at least one resin (5) prior to application onto the support element (2).

Claims

1. A method for producing a friction element according to which a friction lining is applied onto at least one of a first surface and a second surface of a support element, which friction lining comprises a resin layer comprising at least one resin, friction-modifying particles and particle-sized fibers, wherein the proportion of resin is between 20 wt.-% and 70 wt.-% and the total proportion of friction-modifying particles and particle-sized fibers is between 30 wt.-% and 80 wt.-%, wherein the friction-modifying particles and particle-sized fibers are mixed with the at least one resin prior to application onto the support element, the mixing creating a homogeneous distribution of the friction-modifying particles and particle-sized fibers in the at least one resin, and wherein the resin layer forms a friction surface, wherein the friction lining is joined directly to the support element, or wherein the resin layer of the friction lining is applied onto an intermediate resin-infiltrated fiber layer on said support element, wherein said intermediate resin-infiltrated fiber layer is infiltrated with a resin which is identical with the resin of the resin layer with the friction-modifying particles and particle-sized fibers.

2. The method as claimed in claim 1, wherein a fiber fleece is used as the intermediate resin-infiltrated fiber layer.

3. The method as claimed in claim 2, wherein a fiber fleece made of synthetic fibers is used.

4. The method as claimed in claim 3, wherein a fiber fleece is used which consists of fibers with a length selected from a range with a lower limit of 100 m and an upper limit of 100 mm.

5. The method as claimed in claim 1, wherein the particle-sized fibers have a length selected from a range with a lower limit of 20 m and an upper limit of 400 m.

6. The method as claimed in claim 1, wherein friction-modifying particles are used, which have a diameter of between 0.1 m and 80 m.

7. The method as claimed in claim 1, wherein the mixture of friction-modifying particles and particle-sized fibers with resin is applied onto the intermediate resin-infiltrated resin layer, which prior to the application of the mixture of friction-modifying particles and particle-sized fibers with resin is applied onto the support element.

8. A friction element comprising: a support element having a first surface and a second surface, and a friction lining on at least one of the first and second surfaces, wherein the friction lining comprises a resin layer comprising at least one resin, friction-modifying particles and particle-sized fibers, wherein the proportion of resin is between 20 wt.-% and 70 wt.-% and the total proportion of friction-modifying particles and particle-sized fibers is between 30 wt.-% and 80 wt.-%, wherein the friction-modifying particles and particle-sized fibers are mixed with the resin, creating a homogeneous distribution of the friction-modifying particles and particle-sized fibers in the resin layer, and wherein the resin layer forms a friction surface, wherein the friction lining is joined directly to the support element, or wherein the resin layer of the friction lining is applied onto an intermediate resin-infiltrated fiber layer on said support element, wherein said intermediate resin-infiltrated fiber layer is infiltrated with a resin which is identical with the resin of the resin layer with the friction-modifying particles and particle-sized fibers.

9. The friction element as claimed in claim 8, wherein the friction element also contains reinforcement particles in a proportion of between 2 wt.-% and 8 wt.-%.

10. The friction element as claimed in claim 9, wherein the reinforcement particles are selected from a group consisting of ZrSiO.sub.4 silicates, SiC silicates, SiO.sub.2 silicates, and Al.sub.2O.sub.3 silicates.

11. The friction element as claimed in claim 8, wherein the friction-modifying particles have a particle size of between 0.1 m and 80 m.

12. The friction element as claimed in claim 9, wherein the reinforcement particles have a particle size of between 0.1 m and 80 m.

13. The friction element as claimed in claim 8, wherein the particle-sized fibers have a length of between 20 m and 400 m.

14. The friction element as claimed in claim 8, wherein the intermediate resin-infiltrated fiber layer is a fiber fleece.

15. The friction element as claimed in claim 14, wherein the fiber fleece is made of acrylic fibers or aramid fibers.

16. The friction element as claimed in claim 8, wherein the intermediate resin-infiltrated fiber layer comprises fibers with a length of between 100 m and 100 mm.

17. The friction element as claimed in claim 8, wherein the proportion of particle-sized fibers is selected from a range of 2 wt.-% to 15 wt.-%, and the friction-modifying particles are formed by a mixture of carbon, kieselgur having a honeycomb structure and diatomaceous earth having a bulbous structure in a total proportion of 28 wt.-% to 65 wt.-%.

18. The friction element as claimed in claim 8, wherein the proportion of diatomaceous earth having a bulbous structure to kieselgur having a honeycomb structure is between 0.5:1 and 1:1.

19. A friction element comprising: a support element having a first surface and a second surface, and a friction lining on at least one of the first and second surfaces, wherein the friction lining comprises a resin layer comprising at least one resin, friction-modifying particles and particle-sized fibers, wherein the proportion of resin is between 20 wt.-% and 70 wt.-% and the total proportion of friction-modifying particles and particle-sized fibers is between 30 wt.-% and 80 wt.-%, wherein the friction-modifying particles and particle-sized fibers are mixed with the resin, creating a homogeneous distribution of the friction-modifying particles and particle-sized fibers in the resin layer, wherein the proportion of particle-sized fibers is selected from a range of 2 wt.-% to 15 wt.-%, and the friction-modifying particles are formed by a mixture of carbon, kieselgur having a honeycomb structure and diatomaceous earth having a bulbous structure in a total proportion of 28 wt.-% to 65 wt.-%, and wherein the resin layer forms a friction surface, wherein the friction lining is joined directly to the support element, or wherein the resin layer of the friction lining is applied onto an intermediate resin-infiltrated fiber layer on said support element, wherein said intermediate resin-infiltrated fiber layer is infiltrated with a resin which is identical with the resin of the resin layer with the friction-modifying particles and particle-sized fibers.

20. The friction element as claimed in claim 19, wherein the carbon is a mixture of graphite, pyrolytic carbon and activated carbon.

21. The friction element as claimed in claim 20, wherein the proportion of graphite is between 10 wt.-% and 30 wt.-%.

22. The friction element as claimed in claim 20, wherein the proportion of pyrolytic carbon is between 15 wt.-% and 35 wt.-%.

23. The friction element as claimed in claim 20, wherein the proportion of activated carbon is between 5 wt.-% and 15 wt.-%.

24. The friction element as claimed in claim 19, wherein the proportion of kieselgur having a honeycomb structure is between 2 wt.-% and 7 wt.-%.

25. The friction element as claimed in claim 19, wherein the proportion of diatomaceous earth having a bulbous structure is between 5 wt.-% and 15 wt.-%.

26. The friction element as claimed in claim 19, wherein the friction lining also contains reinforcement particles in a proportion of between 2 wt.-% and 8 wt.-%.

27. The friction element as claimed in claim 19, wherein the friction-modifying particles have a particle size of between 0.1 m and 80 m.

28. The friction element as claimed in claim 19, wherein the proportion of diatomaceous earth having a bulbous structure to kieselgur having a honeycomb structure is between 0.5:1 and 1:1.

Description

(1) For a better understanding of the invention the latter is explained in more detail with reference to the following figures.

(2) In a schematically simplified view:

(3) FIG. 1 shows part of a friction element in cross section;

(4) FIG. 2 shows part of a friction element of an embodiment variant in cross section;

(5) FIG. 3 shows part of a friction element of a different embodiment variant in cross section;

(6) FIG. 4 shows the abrasion resistance of different friction linings;

(7) FIG. 5 shows a diagram of the behavior of the coefficient of friction of the friction linings according to FIG. 4 over time;

(8) FIG. 6 shows a graphic representation of the production costs of the friction linings according to FIG. 4.

(9) First of all, it should be noted that in the variously described exemplary embodiments the same parts have been given the same reference numerals and the same component names, whereby the disclosures contained throughout the entire description can be applied to the same parts with the same reference numerals and same component names. Also details relating to position used in the description, such as e.g. top, bottom, side etc. relate to the currently described and represented figure and in case of a change in position should be adjusted to the new position.

(10) All of the details relating to value ranges given in the present description are defined such that the latter include the respective end range between the lower or upper limits of two part ranges, e.g. the range 1 to 10, in particular 3 to 8, is defined to include the end ranges 1 to 3, 1 to 8, 3 to 10 and 8 to 10.

(11) FIG. 1 shows in part a cross section of a first embodiment variant of a friction element 1. Said friction element 1 consists of a support element 2, which has a friction lining 4 on one surface 3. The friction lining 4 comprises a resin 5 or resin mixture, which forms the matrix of the friction lining 4. Friction-modifying particles 6 and/or fibers 7 are embedded in the resin 5, in particular are distributed homogenously therein (according to the above explanations). Some of the friction-modifying particles 6 are arranged projecting over the friction lining surface 8, wherein also said particles 6 are surrounded by a resin layer 9 of resin 5. In other words all of the particles 6 and/or fibers 7 are embedded at least almost completely into the resin 5.

(12) As indicated by dashed lines in FIG. 1, the friction lining 4 can be joined to the support element 2 by an adhesive layer 10. However, it is also possible that the friction lining 4 is joined to the support element 2 directly via the resin 5.

(13) Although in this and also in all further embodiment variants the coating of only one surface 3 of the support element 2 with the friction lining 4 is shown, it is also possible to provide an additional surface 11 opposite said surface 3 with a friction lining 4.

(14) FIG. 2 shows in part a cross section of a different embodiment variant of the friction element 1. The latter comprises the friction lining 4 with the resin 5 or the resin mixture, the friction-modifying particles 5 and/or fibers 7 contained therein, which friction lining is arranged on the support element 2.

(15) Unlike the aforementioned embodiment variants however between the layer of resin 5 with the particles 6 and/or fibers 7 and the support element 2 an intermediate layer 12 is arranged which is joined to the two layers. Said intermediate layer 12 is preferably a fiber layer 13 with fibers 14, in particular a fleece layer, where any type of fleece can be used, for example both laid and random orientation fleeces.

(16) Said fiber layer 13 can be infiltrated at least partly with a resin or resin mixture, in particular the resin 5 of the layer with the friction-modifying particles 6 and/or fibers 7. When using two different resins for the two layers of course the compatibility of the materials should be taken into account with regard to the selection of resins.

(17) The intermediate layer 12 can also be a pure resin layer, which is used in particular as a bonding agent, wherein also in this case the same or different resins can be used for the two layers.

(18) The intermediate layer 12 can also serve the purpose that particles 6 projecting over a lower friction lining surface 15 are pushed into said intermediate layer 12 during the production of the friction element 1, in order to avoid direct contact with the support element 2, and to avoid reducing the homogeneity of the distribution of particles 6 in the resin 5 by pushing away said particles 6 in the direction of the outer friction lining surface 8 when joining together the layers of the friction element 1.

(19) In these two embodiment variants of the friction element the layer thickness 16 of the friction lining 4 is relatively large, in particular in a range of between 500 m and 1000 m, so that proportions of particles 6 can be embedded completely into the resin 5, without projecting over the friction lining surface 8.

(20) In contrast to this FIG. 3 shows an embodiment variant of the friction element 1 in which the layer thickness 16 of the resin layer in the layer of resin 5 and friction-modifying particles 6although not shown in this embodiment of the friction element 1 the fibers 7 can also be included in the resin 5is smaller than a maximum diameter 17 (according to the above explanations relating to the maximum diameter) of the particles 6, in particular can be between 100 m and 500 m. For the above reasons the intermediate layer 12, in particular the fiber layer 13 is arranged between the layer of resin 5 with the particles 6 and the support element 2 and joined to the latter. Also in this embodiment variant the particles 6 projecting partly over the friction lining surface 8 are surrounded by the resin layer 9 of resin 5, in particular completely.

(21) The friction element 1 is used for so-called wet-running applications, i.e. applications in which the friction lining 4 is wetted with a lubricant and coolant, for example in particular a synthetic oil. In principle, such friction discs are known from the prior art in a range of different geometric forms, which conform to the respective application. As this would be known by a person skilled in the art, reference is made here to the relevant literature.

(22) The friction elements 1, for example friction discs, are used for example for single and multiple synchronizations, uncontrolled and controlled distributor gears, brakes, couplings, differential locks, torque vectoring applications, etc. In addition, the friction element 1 is arranged with an additional friction element so that during the activation of the respective device the friction element 1 enters into friction closure with the additional friction element. The number of friction elements 1 and additional friction elementswhich can possibly also be formed by the friction elements 1, are normally designed to be made of different materials than the friction elements 1is not restricted to two, but conforms to the level of friction required. For example per packet three, four, five, six, seven, eight, nine, ten to twenty etc. friction elements can be combined together to form a friction component group, i.e. for example a so-called disc packet.

(23) Torque vectoring applications are defined for example as applications in driving dynamics, in which for example speed differences of a limited slip differential by said system are increased. In this way it is possible for example to support the steering of a vehicle, in that the driving torques are distributed unevenly to the wheels. In this way a higher torque can be steered to the curve outer wheel, so that in normal driving conditions oversteering can be adjusted.

(24) In the preferred form of the invention the friction element 1 is used in single and multiple synchronizations as well as in couplings.

(25) For the production of the friction element 1 the support element 2 is prepared in a first step. The latter can either consist of a solid material or a sintered material, where in the former case the support element 2 is cut or stamped from a suitable raw material, and where also a casting method is possible in principle. In particular, the support element 2 is made of steel, aluminum or an aluminum alloy, a copper alloy, such as brass or bronze etc. In principle, all of the materials known from the prior art can be used for such support elements 2.

(26) In an additional step the mixture is produced from the resin 5 and the friction-modifying particles 6 and/or fibers, before the latter is applied onto the support element 2. In addition, the friction-modifying particles 6 and/or fibers 7 can be mixed into the melt-fluid resin and homogenized therein, for example by means of a mixing section with a mixing screw.

(27) If a resin mixture is used the resins can be mixed previously or with the particles 6 and/or fibers.

(28) This mixture can then be applied directly onto the surface 3 of the support element 1, dried, possibly pressed and hardened, possibly with an intermediate prehardening stage. The drying and hardening temperatures used in this case are suitable for the respective resin. For example, the drying temperature can be between 60 C. and 120 C., the hardening temperature between 160 C. and 350 C. and the prehardening temperature between 120 C. and 180 C. The pressing stage can be performed for example at a pressure of between 5 kN/m.sup.2 and 20 kN/m.sup.2, in particular at a temperature of the resin 5 of between 60 C. and 150 C. If necessary, as explained above the adhesive layer 10 can be applied prior to the application of the mixture with the resin 5 onto the support element 1. For example adhesives with a phenol or epoxy or polyamide-imide base can be used as the adhesives.

(29) Furthermore, it is possible that the mixture of resin 5, particles 6 and/or fibers 7 and possibly additional additives, as explained further below, in general said additives can be added to the resin 5 in all embodiment variants of the friction element 1 or friction lining 4is calendered after the mixing process and then dried, pressed and hardened again, possibly prehardened, in order to obtain in this way a flat semi-finished product, that can then be cut accordingly to fit the support element and joined to the latter.

(30) It is also possible however, that the particles 6 and/or fibers are coated with the resin 5 or the resin mixture, for example in a spraying method. This method is used in particular for the production of a friction element according to FIG. 3. In this case a granulate is formed, which can be scattered onto a resin layer, which was previously applied onto the support element 2 and is used principally as a binding layer. After the scattering the friction lining 4 can then be pressed and hardened, as explained above.

(31) In all of the variants of the method it is possible that the mixture of resin 5, particles 6 and/or fibers 7 is applied onto a fiber layer 13 prior to its application onto the support element 2, so that said fiber layer 13 in the finished friction element 1 is arranged between the resin layer and the support element 2, wherein the fiber layer 13 is soaked at least partly with the mixture of resin 5, particles 6 and/or fibers 7 and/or with resin, which is possibly applied between the friction lining 4 and the support element 2, as explained above.

(32) Thus in all of the embodiment variants of the method for producing the friction element 1 a paste-like mixture of resin 5 or the resin mixture and friction-modifying particles 6 and/or fibers 7 and possibly the additional additives is produced, which is then processed further into a friction lining 4 or into the finished friction element 1. Preferably, said paste-like mixture is applied at a viscosity of the resin selected from a range with a lower limit of 1,000 cPs, in particular 1,500 cPs, and an upper limit of 5,000 cPs, in particular 3,500 cPs, observed respectively at a temperature of 20 C. The viscosity can be adjusted on the one hand via the temperature, but on the other hand also by means of the proportion and the type of particles 6 and/or fibers 7 and possibly additional materials. It is also possible to add viscosity regulators to this mixture, for example alkoxylated alcohols, wherein their proportion in the total mixture can be between 1 wt.-% and 10 wt.-%.

(33) As friction-modifying particles 6 in particular particles 6 are used, which are selected from a group comprising or consisting of SiO.sub.2, TiO.sub.2, WO.sub.2, Al.sub.2O.sub.3, ZrO.sub.2, carbon, Celit, diatomaceous earth, carbon-nanotubes, rubber particles, CNSL (Cashew Nut Shell Liquid), as well as mixtures thereof. The term friction-modifying is defined such that said particles are used to increase the coefficient of friction, for stability of the coefficient of friction, and to increase the adhesion of oil additives to the surface of the lining etc.

(34) As the fibers 7 in addition to paper fibers any fibers 7 can be used, for example cotton fibers. Preferably however, synthetic fibers 7 are used, in particular acrylic fibers, carbon fibers, nitrile fibers, glass fibers or aramid fibers. Also mixtures of different fiber materials can be used, for example a mixture of acrylic and aramid fibers.

(35) The total proportion of friction-modifying particles 6 and/or fibers 7without the fibers 14 of the possibly provided fiber layer 13in the friction lining 4 is selected from a range with a lower limit of 30 wt.-%, in particular 40 wt.-%, and an upper limit of 80 wt.-%, in particular 70 wt.-%. The total proportion of resin 5without the possible additional resin layeron the friction lining 4 is selected from a range with a lower limit of 20 wt.-%, in particular 30 wt.-%, and an upper limit of 70 wt.-%, in particular 60 wt-%.

(36) In cases where a mixture of friction-modifying particles 6 and fibers 7 is used, the proportion of friction-modifying particles 6 is selected from a range with a lower limit of 25 wt.-%, in particular 28 wt.-%, and an upper limit of 65 wt.-%, in particular 60 wt.-% and the proportion of fibers 7 is selected from a range with a lower limit of 2 wt.-%, in particular 5 wt.-%, and an upper limit of 15 wt.-%, in particular 10 wt.-%.

(37) In a particular embodiment a mixture of carbon, Celit and diatomaceous earth is used for the friction-modifying particles 6 in a total proportion of 28 wt.-% to 65 wt.-%. As the carbon graphite, pyrolytic carbon, activated carbon and kieselgur calcined with graphite can be used.

(38) Preferably, the proportion of carbon consists of the mixture of graphite, pyrolytic carbon and activated carbon, wherein particularly preferably the proportion of graphite on the friction lining 4 is between 10 wt.-%, in particular 15 wt.-% and 30 wt.-%, in particular 25 wt.-%, and/or the proportion of pyrolytic carbon on the friction lining 4 is between 15 wt.-%, in particular 18.5 wt.-%, and 35 wt.-%, in particular 28 wt.-%, and/or the proportion of activated carbon on the friction lining 4 is between 5 wt.-%, in particular 7 wt.-%, and 15 wt.-%, in particular 12 wt.-%.

(39) Preferably, the proportion of graphite to pyrolytic carbon to activated carbon is between 1:2:0.3 and 1:1:0.5.

(40) The proportion of Celit in the friction lining 4 is between 2 wt.-%, in particular 3 wt-%, and 7 wt.-%, in particular 6 wt.-%.

(41) The proportion of diatomaceous earth on the friction lining 4 is between 5 wt.-%, in particular 7 wt.-%, and 15 wt.-%, in particular 10 wt.-%. Preferably, the diatomaceous earth is calcined prior to use, in order to reduce the proportion of organic material.

(42) Preferably, the proportion of diatomaceous earth to Celit is between 0.5:1 and 1:1.

(43) In all of the embodiment variants as the resin 5 or resin mixture preferably a resin is used, which is selected from a group comprising or consisting of phenolic resins, melamine resins, amide resins, amide-imide resins, epoxy resins, silicone resins.

(44) The friction lining 4 can also contain hard particles in a proportion of between 2 wt.-% and 8 wt.-%. Preferably, said hard particles are selected from a group consisting or comprising ZrSiO.sub.4, SiC, SiO.sub.2, Al.sub.2O.sub.3, or generally silicates, in particular island silicates.

(45) Both the friction-modifying particles 6 and the hard particles preferably have a maximum particle size of between 0.1 m, in particular 10 m, and 80 m, in particular 60 m.

(46) Preferably, the fiber fleece 13 like the fibers 7 in the resin 5 consists of synthetic fibers. Both for the fibers 7 in the resin 5 and for the fibers 14 of the fiber layer 13 fibers can be used with a length selected from a range with a lower limit of 100 m, in particular 200 m, and an upper limit of 100 mm, in particular 50 mm, wherein the fibers 7, which are added to the resin 5, preferably have a length of between 20 m and 400 m.

(47) With friction lining 4 a friction element 1 can be produced, which presents a reduction of the friction lining wear when in use in wet-running synchronizations.

(48) Table 1 shows several examples to ensure a better understanding of the friction lining 4.

(49) TABLE-US-00001 TABLE 1 Examples of compositions: Example Example 2 Example 3 1 [wt.-%] [wt.-%] [wt.-%] Graphite 15 17 15 Pyrolytic carbon 18 15 20 Celit 5 7 3 Grade B Grade A Diatomaceous 3 3 earth ZrSiO.sub.4 3 Activated carbon 5 6 5 Al.sub.2O.sub.3 6 5 5 Latex 7 7 8 ZrO.sub.2 8 7 8 Phenolic resin 25 27 23 Epoxy resin 8 6 10

(50) For comparison two friction linings were produced according to the prior art. In this case lining A had the composition 40% carbon fibers, 10% aramid fibers, 10% fillers, 40% resin and lining B had the composition of carbon tissue consisting of 70% carbon fibers and 30% resin.

(51) The friction lining 4 according to Example 1 and friction linings A and B were attached respectively to a steel disc. Then the abrasion resistance of said friction elements and the behavior of the coefficient of friction was tested. The tests were carried out under the following test conditions: p spez.[N/mm.sup.2] 3-9, v [m/s] 3-10, gyrating mass: 0.06 kgm.sup.2.

(52) A steel mating disc was used respectively. The results are shown in FIGS. 4 and 5. In FIG. 4 the abrasion is entered in [mm] on the x-axis. As shown clearly, the friction lining 4 according to the invention (bottom bar) under the same conditions suffers 50% less abrasion than friction lining A (top bar) and significantly less abrasion than friction lining B (middle bar) according to the prior art.

(53) FIG. 5 shows the frictional behavior of friction lining 4 according to Example 1 in Table 1, as well as of friction linings A and B over time, i.e. the number of shift cycles, which are entered on the x-axis. The y-axis shows the coefficient of friction cf. It can be seen clearly that the friction lining 4 according to the invention (triangles) on the one hand has a higher coefficients of friction than friction linings A (solid circles) and B (empty circles), and that on the other hand the coefficient of friction fluctuates only slightly over time, so that even after 5,000 shift cycles the friction lining 4 according to the invention still has the higher coefficient of friction.

(54) For completion FIG. 6 shows a bar chart of the costs of the friction linings, wherein the x-axis shows friction lining 4 (right bar) and friction linings A (left bar) and B (middle bar) and the y-axis shows the costs in [$/kg]. It can be seen clearly that the friction lining 4 according to the invention incurs by far the lowest production costs.

(55) The exemplary embodiments show possible embodiment variants of the friction element 1, whereby it should be noted at this point that the invention is not restricted to the embodiment variants shown in particular, but rather various different combinations of the individual embodiment variants are also possible and this variability, due to the teaching on technical procedure, lies within the ability of a person skilled in the art in this technical field

(56) Finally, as a point of formality, it should be noted that for a better understanding of the structure of the friction element 1, the latter and its components have not been represented true to scale in part and/or have been enlarged and/or reduced in size.

LIST OF REFERENCE NUMERALS

(57) 1 Friction element 2 Support element 3 Surface 4 Friction lining 5 Resin 6 Particle 7 Fiber 8 Friction lining surface 9 Resin layer 10 Adhesive layer 11 Surface 12 Intermediate layer 13 Fiber layer 14 Fiber 15 Friction lining surface 16 Layer thickness 17 Diameter