Friction element

(42) Date of commencement of the patent: 15.12.1995 (45) Date of issue: 25. 7.1996

5/28 (56) Documentation:

DE 2808174A

DATABASE WPIL, AN 93-029308 (73)

HOERBIGER & CO D-86956 SCHONGAU (DE).

(72) Inventor:

KEARSEY AtüREW SCHONGAU (DE).

(54) REIBBELAG (57) It is a friction lining (5) for a liquid or

Lubricant cooled device for torque transmission, in particular friction clutch, synchronizing element or brake described, which is fixed to form a friction surface (6) on a support body (2) and the torque aut transmits a counter surface. In order to improve the friction lining (5) and cheaper it is made up of at least two different layers, u.zw. at least one porous support (11, 11 ') fastened on the carrier body (2), which is composed of a composite material of a cellulose base with synthetic fibers and filling material, and a porous friction coating (12) fixed to the support (11, 1T) made of thermoset-bonded synthetic fibers, preferably of carbon.

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The invention relates to a friction lining for a device for transmitting torque, in particular friction clutch, Synchronization element or brake, which can be fastened on a carrier body to form a friction surface and transmits the torque to a counter surface, wherein the friction lining consists of at least two different, porous layers is built up, one of which is fixed to the carrier body and a porous, consists of a cellulosic base made of synthetic fibers and filler material and another of an equally porous friction layer, made of thermoset bonded fibers and attached to the backing.

It is known, in torque transmitting devices in which the torque is transmitted by the friction between abutting surfaces, to provide at least one of these friction surfaces with a friction lining to increase the frictional 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 with relatively little effort, but are subject to relatively high wear, so that they are only used when lower demands are placed on the torque transmission or the friction surfaces only briefly slide on each actuation. The wet-running friction pairings, however, are cooled by liquid or lubricant, so that they are far more resistant.

Such a wet-running friction lining is known from DE-OS 27 44 994, which describes a synchronizing ring for a gear synchronization in toothed couplings, the friction lining of formed on an organic basis friction material, ie from a so-called paper coating, which is adhered to the friction surface. The paper coating is made of a material such as cellulose fibers, asbestos fibers, mineral and metal fibers and fillers impregnated with synthetic resin.

Furthermore, it is known in particular in synchronizers for motor vehicle transmission, applied to the friction surface of a constant velocity ring made of metal friction linings of ceramic material, and based on various metals or metal alloys friction linings, in particular friction linings titanate and molybdenum based, which are usually sprayed. However, friction linings of this type are relatively expensive to produce and do not always have satisfactory friction properties.

In EP 0 162 393 B1, a synchronizing ring is described, the friction surface of which is provided with a separately prefabricated friction body, which is formed from a carrier sheet with sprinkled on this, then sintered and then compacted by pressing Streusinterreibbelag. This separately manufactured friction body is then applied to the friction surface of the base body made of metal and attached thereto, for example welded. This known friction lining has great resistance and useful frictional properties when using a corresponding powder mixture for the production of the sintered lining. However, the effort required for the production is here also relatively large, because first made the separately manufactured friction body, then brought into the correct shape and must be fixed to the friction surface.

Another friction ring for clutches or brakes is finally known from DE-OS 36 09 879, is provided by the friction surfaces at least one with a friction lining produced by sintering. However, the friction lining is directly sintered on the friction surface of the carrier body itself, so that a separate production of the friction body and the application to the friction surface by means of a separate carrier plate omitted. The lattice sintered friction lining is first applied to an annular, flat support body as in the production of the known planar friction lamina, which is then formed as a full ring with one or more sintered friction surfaces by deep drawing cylindrical or conical and then calibrated and final compression. Thus, the production of a friction ring with Streusinterreibbelag is much easier, the advantages of a friction lining produced by sintering, in particular the high resistance to high stresses, however, remain fully intact.

Overall, the previously known wet-running friction linings consist of a homogeneous friction material, which is applied directly to the carrier element, for example glued on, welded, sprayed or sintered on. It follows necessarily that the acting components of the friction material must be distributed homogeneously over the entire friction lining, especially over its entire thickness to ensure that the components effective for the friction always present on the frictional force on the counter surface transmitting surface of the friction lining are. In a highly effective friction lining with high resistance, however, the acting components are expensive, eg Carbon / carbon compound material or aramid fibers. Since relatively much expensive friction material is necessary to produce such a friction lining, this is also relatively expensive. On the other hand, friction linings made on paper or cork are cheaper, but also have a lower performance. Even friction linings made of sintered metal are cheaper.

In DE-OS 28 08 174 A further composed of certain materials friction lining of the type mentioned is given, but which is an embodiment for a dry-running

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Clutch acts. With this friction lining, the disadvantages of the previously known friction linings to be eliminated, ie It should be possible to produce inexpensive friction linings in which short fibrous asbestos material can be used and their bursting strength or Nevertheless, the sling resistance and breaking strength are still considerably higher than the values ​​obtained with the previously known friction linings using loose asbestos fibers. In dry-running clutches occurs during the clutch actuation significant wear, which is why it is necessary to make the friction or wear layer correspondingly thick.

The invention differs from this known embodiment initially in a fundamental way in that the friction lining according to the invention is intended exclusively for a cooled by liquid or lubricant friction lining. In such cooled and lubricated friction linings is known to occur virtually no wear. This has the consequence that in such clutches of the friction lining can be made disproportionately thin, resulting in significant differences in the structure and in the composition of the friction lining.

The invention has for its object to provide a special liquid-cooled friction lining, which combines a very high heat resistance and a low static-dynamic friction coefficient with high reliability low cost and low wear.

With the invention, this object is achieved in that for a cooled by liquid or lubricant friction lining, the porous pad a weight of 200 to 1500 g / m² and the friction layer attached to the pad is made thinner than the pad and made of duroplastverbundenen synthetic fibers, such as boron, carbon, aramid, which has as many fibrils, glass, stone or ceramic, preferably made of carbon and that the friction layer has a higher porosity as the pad has.

As has been shown, wet-running friction linings, such as Paper pads, practically not worn during normal operation. During the run-in, only a setting of the lining takes place, which progresses slowly after a very long use. In any case, the production of wet-running clutches is possible, the friction lining has the same or a longer life than the transmission. It follows that the components of the friction lining which act for the friction are required only in the outermost layer of the same, which rests against the counter surface. Under this actual friction layer is sufficient a relatively cheap porous support material, whose task is merely to support the actual friction layer and to cool, namely by sucking liquid or lubricant at unloaded friction lining by dispensing the liquid or of the lubricant as soon as the friction lining is pressed under pressure against the counter surface.

The friction lining according to the invention accordingly has the advantageous properties of the previous so-called paper coverings, namely the very high heat resistance with a low static-dynamic friction coefficient, without having the disadvantage namely, the high manufacturing costs because in the inventive design, the relatively expensive components effective for the friction only in a thin layer on the surface of the friction lining, So are provided in only small amount.

On a test bench, tests were carried out under severe conditions with a friction lining provided with a four-fiber-thick (0.02 mm) friction layer. The fibers were black and the pad was white. Although a compression of 0.08 mm per coating took place during the experiment, the fibers could be seen under the microscope. These were in the same amount as before after the trial.

Other advantages of the friction lining according to the invention are that its costs are quite comparable to those of ordinary paper coverings with a homogeneous coating without expensive deposits made of synthetic fibers. The relatively expensive upper friction layer is very light and thin in the friction lining according to the invention, only the cheap bottom pad is relatively heavy and thick. Also, the manufacturing costs are not much higher than the cost of producing ordinary paper coverings. In addition, the friction lining according to the invention can work on soft (uncured) mating surfaces, eg on surfaces of steel, aluminum alloys and plastic.

In the context of the invention, further embodiments of the friction lining according to the invention are possible. Thus, the friction layer can have a weight of 10 to 120 g / m² and have a thickness of 0.02 to 0.3 mm. It has been shown that this dimensioning is expedient in order to achieve the advantages according to the invention, in particular a thin and therefore less expensive friction layer.

The pad preferably has a heat-resistant Duroplastanteil from 20 to 50 wt .-% of the total weight of the pad, for example phenolic modified resins (resole or novolac), epoxy resin, melamine, silicone resin, acrylic resin and the like, preferably phenolic resole resin in the amount of 28 to 36% by weight of the total weight of the backing. The thus formed pad is relatively easy to produce, relatively cheap and has a large porosity, so that they have enough liquid or

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Can absorb lubricant for cooling.

The friction layer may according to a further feature of the invention in the amount of at least 70 wt .-% of its total weight made of synthetic fibers and thermosets and have a proportion of heat-resistant thermoset, which is 25 to 60 wt .-% of the total weight of the friction layer, eg phenolic modified resins (resole or novolac), epoxy resin, melamine, silicone resin, acrylic resin, preferably phenolic resole resin in the amount of 45 to 55 wt .-% of the total weight of the friction layer. The heat-resistant thermoset of the friction layer according to the invention may contain up to 50 wt .-% filler, preferably a filler of carbon particles. As a result, a secure connection between the components of the friction layer is achieved.

According to the invention, an advantageous friction layer also results from the fact that the preferably non-woven synthetic fibers of the friction layer have a fiber length of 3 to 25 mm, preferably 6 to 15 mm, with a fiber diameter of 3 to 50 μm. The fibers are distributed and aligned over the entire thickness of the friction layer in an irregular arrangement, resulting in particularly good frictional properties.

The filler material in the base has in another embodiment of the invention an absorbent structure, preferably consists of crystalline silicate and is provided in a proportion between 2 and 20 wt .-% of the total weight of the substrate, preferably at least 10 wt .-%, wherein in the filler more than 2.5 times its own weight of oil is absorbable. The resulting high absorbency ensures effective cooling of the friction lining, even under heavy load.

Overall, the pad according to the invention has a porosity between 50 and 10%, preferably between 20 and 10% for synchronization rings and between 50 and 40% for friction plates.

It has also proven to be advantageous if, according to the invention, the porosity of the friction layer is greater than the porosity of the substrate, wherein it is preferably between 50 and 95%. Since the greatest heat load is known to occur in the region of the friction layer, it is also advantageous to have sufficient cooling in this area.

According to the invention, it is expedient to carry out the lining thickness of the substrate between 0.3 and 2.5 mm with a constant thickness of the friction layer between 0.02 and 0.3 mm. This design has proven relatively well in practice.

The friction lining according to the invention can be produced by means of paper machines known per se, it being possible to produce the individual layers, ie the friction layer and the backing consisting of one or more layers, either separately and then to join them together, or to apply the individual layers together thickened and connect during their manufacture, if the paper machine is set up for this type of production.

To connect the individual covering layers, the invention provides that the friction layer and the base can be firmly joined together by the crosslinking of the thermoset in both layers and / or by a physical layer mixture in the boundary region and / or by gluing the layers. Which of these options will be used in practice will depend on the existing conditions, in particular the available production machines and the exact composition of the individual friction layers. In any case, however, a secure connection between the individual layers is achieved.

A preferred embodiment provides that the friction layer on the pad with an adhesive layer of 0.01 to 0.05 mm thickness of high heat resistant adhesive, such as nitrile-modified phenolic resins, epoxy resin, acrylic resin, preferably a nitrile-modified phenolic resin, bonded and cured. As has been shown, a firm and durable connection is achieved in this way.

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

Further details and advantages of the invention will become apparent from the following description of exemplary embodiments which are illustrated in the drawings. In these show: 1 a provided with a friction lining according to the invention synchronization ring in a perspective view, Fig. 2 a flat clutch plate with a friction lining according to the invention on both sides also in a perspective view and the FIG. 3 to 6 different embodiments of the attached to a support body friction lining according to the invention in cross-section as greatly enlarged shown sections.

The synchronizer ring shown in Fig. 1 is denoted by 1 and consists of a carrier body 2 made of a mechanically strong material, preferably of a metal, of a metal alloy or a sintered body, but it may also be made of plastic. The carrier body 2 is profiled according to the respective application. In Ausführungsbeispiei he has at its outer periphery

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Driving cam 3 and an external toothing 4 on.

At its inner periphery of the support body 2 is formed as a conical surface on which a friction lining 5 is fixed, which also forms a conical friction surface 6 on the inner circumference, provided with transverse to the friction surface 6 grooves 7 for the outflow of the cooling liquid or lubricant is. About the friction surface 6, the torque is transmitted to a counter surface of a further synchronization element, not shown.

In the embodiment of FIG. 2 it is a flat clutch plate 8, which consists of a flat support body 2, which is provided on both sides with a respective friction lining 5. Each friction lining forms on its outer side a flat friction surface 6, which is provided for the outflow of the coolant with a crosswise arranged grooving 9. At the inner edge of the clutch plate 8 is an internal toothing 10 for the transmission of the torque transmitted through the clutch. The carrier body 2, which is formed as an annular disc, is also made in this embodiment of metal or plastic. The friction surfaces 6 cooperate with flat counter surfaces, which are usually formed by flat annular metal discs with external teeth for forwarding the torque.

The structure of the friction lining according to the invention is made of the in Figs. 3 to recognize 6 illustrated embodiments. The friction lining 5 consists in all embodiments of at least two layers and is mounted on a support body 2, for example glued. The Fig. 3 to 5 show embodiments in which the friction lining 5 consists of two layers, u.zw. from a porous support 11 fixed to the support body 2 and from a likewise porous friction layer 12 which is fastened to the support 11. The friction layer 12 forms on its outer side the flat, cylindrical or conical friction surface 6, which cooperates with a counter surface.

The embodiment of FIG. 6 differs from the embodiments of FIGS. 3 to 5 in that the friction lining 5 consists of three layers, u.zw. of a first pad 11, a second pad 11 'mounted thereon, and finally of the friction layer 12 with the friction surface 6 carried by the pad 11'.

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

Usually the base is made of cardboard with a weight of 300 to 1000 g / m² manufactured, wherein the weight depends on the final coating thickness. The resin content is 20 to 50 wt .-% of the total weight of the pad and is conveniently mixed or infiltrated during paper production or during a second operation with the other ingredients. The porosity of the pad is usually between about 10 and 50%. The covering thickness of the base 11 is between 0.3 and 2.5 mm.

The friction layer 12 is also porous and consists of duroplastverbundenen synthetic fibers, preferably 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 base 11 and is preferably between 50 and 95%.

Of particular importance is how the friction layer 12 is mounted on the base 11. This can be done in different ways. The friction layer 12 can be glued to the substrate 11 as a nonwoven. The amount of adhesive must be optimized so that the porosity between and within the pad 11 and the friction layer 12 is not destroyed. However, the friction layer 12 may also during paper drying, eg as a nonwoven in the film press, are pressed together with adhesive or resin binder and dried. Finally, the friction layer can be applied to the paper machine screen used during the paper-forming of the base and connected to the base. The nonwoven fabric forming the friction layer can be placed directly under the paper forming the support directly onto the wire, in which case the friction layer serves as a support for the substrate.

In the Figs. 3 to 6 different embodiments of the connection between the individual layers of the friction lining are shown. In all embodiments, the friction lining 5 is fixed by means of an adhesive layer 13 on the carrier body 2. The attachment of the friction layer 12 on the base 11 is carried out as shown in FIG. 3 by the cross-linking 14 of the thermoset in both layers, whereby a solid compound is formed, which does not interfere with the porosity between the two layers 11,12.

In the embodiment of FIG. 4, however, a physical connection 15 is provided. The two layers 11 and 12 are mixed together in the border area, which also leads to a

AT 401 255 B solid and yet porous compound leads. FIG. 5 finally shows a compound in which the friction layer 12 is connected to the pad 11 by a bond 16. In the embodiment of FIG. 6 are two bonds provided, u.zw. a bond 16 between the friction layer 12 and the underlying layer of the base 11 'and a bond 16' between the two documents 11 and 1Γ. These two bonds are such that they do not affect the porosity between the layers of the friction lining 5.

Two examples of the composition of the friction lining according to the invention are given below, which have proved successful in experiments:

Example 1:

The friction lining 5 is composed of two different layers, u.zw. from a base 11 and a friction layer 12. The friction layer consists of 20 g / m² a carbon fiber fleece having a fiber length of 3 to 12 mm. Each fiber has about 12,000 filaments each 7 μm in diameter. The carbon fiber fleece was impregnated with 48% by weight of the total weight of the friction layer of phenolic resole resin and 30 g / m² an adhesive AL 6700 from BF Goodrich, which is a nitrile-modified phenolic resin, on a base with a weight of 400 g / m² glued. The pad consists of 40% by weight of the total weight of the pad of cotton lint or cotton fibers, 15% by weight of crystalline silicate, 15% by weight of mineral fiber and 30% by weight of phenolic resole resin. The carbon fiber nonwoven fabric was made as an independent nonwoven fabric with polyvinyl alcohol as a binder and consistently impregnated with phenolic resin.

The two parts, carbon fiber friction lining 5 and base 11, were glued together during the manufacture of the lamellae or layers and compacted and glued to the carrier body 2 with the same type of adhesive that was used between the layers. This friction pad, which has a porosity of 45% has been tested and shows the results and benefits for lamination applications as described below.

Example 2:

The friction lining 5 according to the invention was produced simultaneously on a paper machine. The friction layer 12 consists of 35 g / m² Carbon fiber fleece with a fiber length of 6 to 15 mm. Each fiber has about 9000 filaments and each filament has a diameter of 30 lim. The carbon fiber nonwoven fabric was prepared on a riser former with 48% by weight of the total weight of the friction phenolic resole resin and 10% by weight nitrile modified rubber and then applied to the backing immediately prior to the dandy. The base has a weight of 500 g / m² and consists of 40% by weight of cotton lint or cotton fibers, 20% by weight of crystalline silicate, 15% by weight of mineral fibers and 25% by weight of phenolic resole resin.

The friction lining thus produced can be processed as a normal paper coating, for example punched in partial circles, which uses for synchronization rings of transmissions, or stamped in slats that can be glued onto steel beams. In particular, when this friction pad is glued and used on a 25% porosity synchronizer ring, it shows good results.

Under the conditions prevailing in the synchronization of manual transmissions of motor vehicles, the friction lining according to the invention showed the following properties:

- The dynamic coefficient of friction was u = 0.12 and the static coefficient of friction u = 0.125 μm. This low coefficient of friction results in a smooth operating feeling when switching the transmission. In synchronizers with previously known paper coverings, the static coefficient of friction is much higher, which results in a significantly poorer operating feel, and sintered linings, the dynamic coefficient of friction is lower, which also less power is expected.

- With a density change of 30%, a change in the coefficient of friction of only 5% also occurs. This is much lower than with other friction linings in which a density change of eg 10% results in a coefficient of friction change of about 10%.

- The carbon fibers used in the friction lining according to the invention are oil insensitive. When using different types of oil, there was only a change in the coefficient of friction of around 10%. By comparison, sintered metal has a coefficient of friction of around 30%.

- The carbon fibers of the friction lining according to the invention have a very open, porous structure, which allow use of the friction lining without grooving.

Coupling tests with the friction lining according to the invention have the following advantages:

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Both the dynamic and the static coefficient of friction were W = 0.08 in the case of the paper coating according to the invention, whereas the two coefficients of friction for a comparable sintered coating are at approximately u = 0.05 dynamic and u = 0.08 static.

- There was a higher performance than normal paper coverings, especially burning or charring the friction linings according to the invention not.

- For a higher energy capacity is achieved than with sintered metal and pure Kunstfaserbelägen. In addition, the coatings according to the invention have a very high heat resistance and heat capacity.

- The friction lining according to the invention generates on the cooperating counter surface only under very high energy and performance conditions so-called hotspots, ie overheated places, the permissible conditions are much higher than paper and pure carbon deposits.