Friction lining.

p0001The invention relates to a friction lining for a device for torque transmission, in particular a friction clutch, synchronization element or brake, on a support body attachable to form a friction surface and transmits the torque to a mating surface, wherein the friction lining is composed of at least two different porous layers , of which one is fixed on the carrier body and a porous, consisting of a cellulosic base with synthetic fibers and filler pad for a likewise porous, fixed on its friction layer is fabricated from duroplastverbundenen fibers.

p0002It is known in devices for transmitting torque in which the torque is transmitted by the friction between aneinandergepreßten surfaces, at least to provide one of these friction surfaces with a friction coating to increase the friction force between the two surfaces. A distinction is made between dry running and wet running friction pairings. The dry-running friction pairings can be produced at relatively low cost, but are subject to a relatively high wear, so that they are applied only if lower demands are placed on the torque transmission or the friction surfaces only briefly slide on each other with each actuation. The wet-running friction pairings are cooled by contrast fluid or lubricant, so that they are far more resistant.

p0003Such a wet-running friction lining is known from DE-OS 27 44 994, which describes a synchronizer for a transmission synchronization with tooth clutches, whose friction lining is composed of organic-based formed friction material, ie a so-called paper covering which is bonded to the friction surface. The paper covering is formed of a material such as cellulose fibers, asbestos fibers, mineral fibers and metal fibers and filling materials, which is impregnated with synthetic resin.

p0004It is particularly in synchronizing devices for motor vehicle transmissions known to apply to the friction surface of a unison ring of metal friction linings made of ceramic material, and on the basis of different metals or metal alloys friction linings made, especially friction linings titanate and molybdenum-based, which are usually sprayed. However, friction materials of this type are relatively expensive to manufacture and do not always satisfactory friction on.

p0005In EP 0162393 B1, a synchronizing ring is described whose friction surface is provided with a separately prefabricated friction body, which is formed of a support plate with a sprinkled on this, then sintered and then compressed by pressing Streusinterreibbelag. This friction body separately produced is then applied to the friction surface of the base body made of metal and fixed to, for example welded. This known friction lining includes using a corresponding powder mixture for the production of the sintered lining large resistance and also useful frictional properties. However, the required for the production expenditure is also relatively large, because initially produced the friction body separately manufactured, then moved into the correct shape and must be mounted on the friction surface.

p0006Another friction ring for clutches or brakes is finally known from DE-OS 36 09 879 known from the friction surfaces at least one is provided with a manufactured by sintering friction lining. The friction lining, however, is itself sintered directly on the friction surface of the support body so that a separate manufacturing of the friction body and the application to the friction surface by means of a separate carrier sheet is removed. The scatter-sintered friction lining is first applied as in the preparation of the known flat friction discs on an annular, flat supporting body which is subsequently formed as a full ring with one or more besinterten friction surfaces by thermoforming cylindrical or conical, and then calibrated and finally compressed. In order for the manufacture of a friction ring with Streusinterreibbelag is substantially simplified, the advantages of a friction lining produced by sintering, in particular the high resistance to high stresses, however, remain fully intact.

p0007Overall, the known wet-running friction linings made of a homogeneous friction material applied directly to the support element, for example glued, welded, sprayed or sintered. As a result forcibly that the active components of the friction material must be distributed homogeneously over the entire friction lining, in particular over its entire thickness to ensure that the amount effective for friction components always also on the frictional force transmitted to the counter-face surface of the friction lining available. In a highly effective friction lining with great resilience, however, the active components are expensive, such as carbon / carbon compound material or aramid fibers. Since relatively large amount of expensive friction material is needed to produce such a friction lining, this is also relatively expensive. produced on paper or cork linings, however, are cheaper but also have only a lower power. Also friction linings of sintered metal are cheaper.

p0008The invention has the object of providing a friction lining was the initially defined execution to improve so that he take advantage of the synthetic fibers, namely very high heat resistance and low static and dynamic Reibwertverhältnis, with the advantages of the sintered metal coating, namely reliability, low cost and less wear pooled.

p0009With the invention, this object is achieved in that for a cooled by liquid or lubricant friction lining, the porous pad having a weight of 200 to 1500 g / m² and secured to the pad friction layer from duroplastverbundenen synthetic fibers, for example of boron, carbon, aramid, having as many fibril, glass, stone, or ceramic, preferably consisting of carbon, and that the friction layer has a higher porosity than the support.

p0010As has been shown to be wet-running friction materials, such as paper coatings, in normal operation practically not worn. During the running a set of coating only takes place, which progresses slowly over a long period use. In any event, the preparation of wet-running clutches is possible, the friction lining having the same or a longer life than the transmission. It follows that the forces acting on the friction of the friction components thereof only in the outermost layer, which bears against the counter surface, are required. Under this actual friction layer is a relatively inexpensive porous support material whose function is merely to support the actual friction and cool, namely, by aspiration of fluid or lubricant at the unloaded friction coating and dispensing the liquid or lubricant when the friction lining under pressure sufficient is pressed against the counter-surface.

p0011The friction lining according to the invention accordingly has the advantageous properties of the previous so-called paper coverings, namely the very high heat resistance at low static-dynamic Reibwertverhältnis without possessing their disadvantage, namely, the high manufacturing cost, because in the practice of the invention, the amount effective for the friction, relatively expensive components are therefore provided only in a thin layer on the surface of the friction lining in only a small amount.

p0012On a bench tests were carried out under severe conditions with a friction lining, which was equipped with a four-fiber-thick (0.02 mm) Friction. The fibers were black and the base was white. Although during the trial took place a compression of 0.08 mm per pad, you could see the fibers under the microscope. These were present after the test in the same amount as before.

p0013Additional advantages of the friction lining of the invention is that its costs are comparable with those of quite ordinary paper linings with a homogeneous coating without expensive deposits of synthetic fibers. The relatively expensive upper friction layer is very light and thin the friction lining of the invention, only the cheap lower pad is relatively heavy and thick. Also, the manufacturing costs are not much higher than the costs for the production of ordinary paper linings. In addition, the friction lining of the invention to soft (non-hydrogenated) may counter surfaces work, for example on surfaces of steel, aluminum alloys and plastic.

p0014In the invention, further embodiments of the friction lining according to the invention are possible. Thus, the friction layer have a weight of 10 to 120 g / m² and a thickness of 0.02 to 0.3 mm. It has been found that this dimensioning is advantageous in order to achieve the inventive advantages, especially a thin and therefore priced only little weight falling friction layer.

p0015The pad preferably has a heat-resistant Duroplastanteil from 20 to 60 wt .-% of its total weight on, eg phenolic modified resins (resol or novolak), epoxy resin, melamine, silicone resin, acrylic resin, preferably phenolic resol resin in the amount from 28 to 36 wt .-% of the total weight of the backing. The thus formed pad is relatively easy to produce, relatively inexpensive and has a high porosity, so that it can absorb sufficient liquid or lubricant for cooling.

p0016The friction layer according to a further feature of the invention to the extent of at least 70 wt .-% of their total weight made of synthetic fibers and thermoset and a proportion of heat-resistant thermosetting plastic, the weight .-% of the total weight of the friction layer is 25 to 60, for example, phenolic modified resins (resol or novolak), epoxy resin, melamine, silicone resin, acrylic resin, etc.., preferably phenolic resol resin in the amount of 45 to 55 wt .-% of the total weight of the friction layer. The heat-resistant duroplastic of the friction layer according to the invention may contain up to 50 wt .-% filler, preferably a filler of carbon particles. This achieves a secure connection between the constituents of the friction layer.

p0017An advantageous friction layer is obtained according to the invention also characterized in that the preferably non-woven synthetic fibers of the friction layer 10 to 75 wt .-% of the total weight of the friction layer make and a fiber length of 3 to 25 mm, preferably 6 to 15 mm, with a fiber diameter of 3 to 50 microns, whereby preferably carbon fibers in the amount of 50 to 60 wt .-% of the total weight of the friction layer are provided with a length of 6 to 15 mm and a fiber diameter of 7 microns. The fibers are distributed and aligned over the entire thickness of the friction layer in an irregular arrangement, resulting in particularly good frictional properties.

p0018The filler material in the pad has in a further embodiment of the invention an absorbent structure is preferably made of crystalline silicate and is present in a proportion 2-20 wt .-% of the total weight of the backing, preferably at least 10 wt .-%, said in filler more than 2.5 times its own weight of oil is absorbable. The thus achieved great absorbency ensures effective cooling of the friction even with larger loads.

p0019Overall, the situation has according to the invention has a porosity 50-10%, preferably between 20 and 10% for synchronizing rings and occur between 50 and 40% for friction discs.

p0020Be advantageous it has also been found when the present invention, the porosity of the friction layer is greater than the porosity of the surface, where it is preferably between 50 and 95%. As the largest heat load known to occur in the area of ​​friction, it is also advantageous to have sufficient cooling in this area.

p0021According to the invention, it is expedient to carry out the lining thickness of the support from 0.3 to 2.5 mm with a constant thickness of the friction layer is from .02 to 0.3 mm. This design has proven relatively successful in practice.

p0022The friction lining according to the invention can be produced by per se known paper machine, it being possible for the individual layers, so the friction and which consists of one or more layers pad, either separately manufacture and anschlieβend to connect with each other, or else the individual layers together to thicken and during their manufacture to connect with each other when the paper machine is set up for this type of product.

p0023To connect the individual pad layers, the invention provides that the friction layer and the substrate can be connected through the networking of the present in two layers thermosetting resin and / or by physical layers blend at the limits and / or by gluing the layers firmly together. Which of these options is to apply in practice respectively, will depend on the existing circumstances, in particular the available manufacturing equipment, and the exact composition of each friction layers. In any case, a secure connection between the individual layers is achieved.

p0024A preferred embodiment provides that the friction layer bonded and cured to the substrate with an adhesive layer of 0.01 to 0.05 mm in thickness from highly heat-resistant adhesive, for example, nitrile modified phenolic resins, epoxy resin, acrylic resin, etc.., Preferably a nitrile modified phenolic resin is. Such phenolic resin is available under the trademark AL 6700 from BF Goodrich commercially. As has been shown, is reached a firm and durable connection in this way.

p0025The compound of the friction lining according to the invention with the carrier body, which can consist, for example of metal or plastic is carried out, preferably in the same manner as the connection between the individual layers of the friction lining, wherein also the same adhesive can be used.

p0026Further details and advantages of the invention will become apparent from the following description of exemplary embodiments which are illustrated in the drawings. In these: Figure 1 is a provided with a friction lining inventive synchronizing ring in a perspective view, Figure 2 is a planar clutch plate with a friction coating according to the invention on both sides also in a perspective view and Figure 3 to 6, various embodiments of the mounted on a carrier body... friction lining according to the invention in cross-section as sections represented greatly enlarged.

p0027The synchronizer ring shown in Fig. 1 is indicated by 1 and consists of a base body 2 made of a mechanically resistant material, preferably of a metal, a metal alloy or a sintered body, but it can also be made of plastic. The carrier body 2 is profiled to the respective purpose. In the exemplary embodiment, it has at its outer periphery drive cams 3 and an external toothing 4th

p0028At its inner periphery of the support body 2 is formed as a conical surface, on which a friction lining 5 is attached, of a likewise conical friction surface 6 forms at the inner circumference, which is provided with transversely across the friction surface 6 extending grooves 7 for the outflow of the cooling fluid or of the lubricant is. Via the friction surface 6, the torque is transmitted to an opposing surface of an unillustrated other synchronization element.

p0029In the embodiment of FIG. 2 is a planar clutch plate 8, which consists of a flat base body 2, which is provided on both sides with a friction lining. 5 Each friction lining forms on its outside a plane friction surface 6, which is provided for draining the coolant with an arranged crosswise grooving. 9 At the inner edge of the clutch plate 8 is an internal tooth 10 for the forwarding of the transmitted through the clutch torque. The carrier body 2, which is formed as an annular disc, there is also in this embodiment, made of metal or plastic. The friction surfaces 6 cooperate with planar mating surfaces, which are usually formed from flat annular metal discs with an external toothing for transmitting the torque.

p0030The construction of the friction lining according to the invention can be seen from the embodiments shown in FIGS. 3-6. The friction lining 5 is in all embodiments at least two layers and is mounted on a carrier body 2, for example glued. FIGS. 3 to 5 show embodiments in which the friction pad 5 is composed of two layers, u.zw. from a fixed to the carrier body 2 porous sheet 11 and also from a porous friction layer 12, which is fixed on the base eleventh The friction layer 12 is formed on its outer side, the flat, cylindrical or conical friction surface 6, which cooperates with a counter-surface.

p0031The embodiment of Fig. 6 differs from the embodiments according to Figs. 3 to 5, characterized in that the friction lining 5 is composed of three layers, u.zw. from a first sheet 11, a second pad mounted thereon, 11 'and finally out of the friction layer 12 with the friction surface 6, of the substrate 11' is worn.

p0032In all embodiments, mounted on the support body 2 pad 11 is composed of a composite material comprising a cellulosic base with synthetic fibers and filler material. It is for example, a fiber-reinforced plastic filled. Basis are cellulose fibers with additional synthetic fibers, which increase the heat resistance and stability. Fillers such as crystalline silicates are another important component which has a high absorbency, such as up to 250% of its own weight.

p0033Usually, the base made of cardboard with a weight of 300 to 1000 g / m² is prepared, wherein the weight is dependent on the final pad thickness. The resin content is 20 to 50 wt .-% of the total weight of the backing and is suitably mixed or infiltrated during paper manufacture or during a second work operation with the other constituents. The porosity of the backing is usually between about 10 and 50%. The coating thickness of the sheet 11 is between 0.3 and 2.5 mm.

p0034The friction layer 12 is likewise porous and consists of duroplastverbundenen synthetic fibers, preferably of carbon. It has a weight of about 10 to 60 g / m² and a thickness of 0.02 to 0.3 mm. The porosity of the friction layer 12 is greater than the porosity of the backing 11 and preferably is between 50 and 95%.

p0035is of particular importance as the frictional layer 12 is fixed on the substrate eleventh This can be done in various ways. The friction layer 12 may be adhered as a mat on the substrate eleventh The amount of adhesive has to be optimized so that the porosity between and within the pad 11 and the frictional layer 12 is not destroyed. The friction layer 12 may also during the paper drying, such as a fleece in the film press, pressed together, as a binder with adhesive or resin and dried. Finally, the friction layer can be applied during the paper forming the pad on the screen of the paper machine used in this case and connected to the pad. The material forming the frictional layer fleece can be placed directly on the screen below the forming the backing paper, in which case the friction layer serves as a carrier of the pad.

p0036In FIGS. 3 to 6 show various embodiments for the connection between the individual layers of the friction pad are shown. In all embodiments of the friction lining 5 is fixed by means of an adhesive layer 13 on the carrier body second The attachment of the friction layer 12 on the substrate 11 takes place according to FIG. 3 by the cross-linking of the 14 located in both layers thermosetting resin, whereby a firm connection is established which does not disturb the 11,12 porosity between the two layers.

p0037In the embodiment of Fig. 4, however, a physical connection 15 is provided. The two layers 11 and 12 are there mixed with one another in the border region, which also leads to a solid and yet porous compound. Fig. 5 shows a connection, wherein the friction layer 12 is connected to the pad 11 by a bonding sixteenth In the embodiment of FIG. 6, two bonds are provided u.zw. an adhesive bond 16 between the friction layer 12 and the underlying layer of the pad 11 'and an adhesive bond 16' between the two materials 11 and 11 '. Both these bonds are such that they do not impair the porosity between the individual layers of the friction lining. 5

p0038Below are two examples of the composition of the friction lining of the invention nor used, which have been proven in experiments:

Example 1:

p0039The friction lining 5 is composed of two different layers, u.zw. from a backing 11 and a friction layer 12. The friction layer consists of 20 g / m² of a carbon fiber nonwoven fabric having a fiber length of 3 to 12 mm. Each fiber has about 12,000 filaments with a diameter of 7 microns. The carbon fiber mat was 48 wt .-% of the total weight of the friction layer impregnated resole phenolic resin with 30 g / m² of adhesive AL 6700 from BF Goodrich, in which it is a nitrile modified phenolic resin to a backing with a weight of 400 g / m² adhered. The lower layer consists of 40 wt .-% of the total weight of the pad from Baumwollefusseln or cotton fibers, 15 wt .-% of crystalline silicate, 15 wt .-% mineral fibers and 30 wt .-% a resole phenolic resin. The carbon fiber fabric was prepared as an independent non-woven with polyvinyl alcohol as a binder and consistently impregnated with phenolic resin.

p0040The two parts, carbon fiber friction lining 5 and substrate 11 were adhered to each other during manufacture of the lamellae or layers, and compressed and bonded with the same type of adhesive that was used between the layers to the support body second This friction lining, having a porosity of 45% was tested and displays the results and advantages of slat applications, as described below.

Example 2:

p0041The friction lining according to the invention 5 was prepared at the same time on a paper machine. The friction layer 12 is made of 35 g / m² nonwoven carbon fiber having a fiber length of 6 to 15 mm. Each fiber has about 9000 filaments and each filament has a diameter of 30 microns. The carbon fiber fabric was produced on a Steigsieb Shaper with 48 wt .-% of the total weight of the friction layer resole phenolic resin and 10 wt .-% nitrile-rubber and then immediately applied to the pad before the dandy roll. The backing has a weight of 500 g / m² and consisting of 40 wt .-% Baumwollefusseln or cotton fibers, 20 wt .-% of crystalline silicate, 15 wt .-% mineral fibers and 25 wt .-% a resole phenolic resin.

p0042The friction lining thus produced can be processed as a normal paper covering, eg punched into partial circuits that used for synchronizing rings of gear units, or punched into strips that can be adhered to steel girder. If this friction lining is bonded and used on a synchronizing ring having a porosity of 25%, it shows particularly good results.

p0043Under the conditions that prevail when synchronizing transmissions of motor vehicles, the friction lining of the invention showed the following characteristics:<ul><li>The dynamic coefficient of friction was μ = 0.12, and the static friction coefficient μ = 0.125 microns. Through this small Reibwertverhältnis a smooth operational feeling arises during transmission shifting. In synchronization with devices previously known paper linings of the static coefficient of friction is much higher, which results in a much poorer operation feeling, and sintered linings, the dynamic coefficient of friction is lower, whereby less power can be expected.</li><li>At a density of 30% change also occurs a friction value of only 5%. This is much lower than other friction linings, in which a change in density of eg 10% has a coefficient of friction of about 10% resulted.</li><li>The carbon fibers used in the friction material according to the invention are oil resistant. When different types of oil merely resulted in a coefficient of friction of around 10%. In comparison, there occurs a friction value of around 30% for sintered metal.</li><li>The carbon fibers of the friction lining of the invention have a very open, porous structure that enable use of the friction lining without grooving. When coupling experiments with the friction lining of the invention</li></ul> The following advantages have shown:<ul><li>Both the dynamic and the static coefficient of friction was the paper pad μ = 0.08 according to the invention, while the two friction 0.05 = 0.08 are in a comparable sintered lining at about μ = μ dynamic and static.</li><li>It resulted in a higher efficiency than normal paper linings, burn or carbonize particular friction linings of the invention no.</li><li>For a higher energy capacity than sintered metal and pure synthetic fiber pads is achieved. Moreover coverings according to the invention have a very high heat resistance and heat capacity.</li><li>The friction lining according to the invention produced on cooperating with their mating surface only at very high energy and power conditions so-called "hot spots", ie hot spots, with the permitted conditions are much higher than in paper and pure carbon surfaces.</li></ul>