JPH0463257B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a friction material for a clutch, particularly a wet friction material suitable for use in an oil solution.

[Conventional technology]

For example, the clutch that transmits the drive from the prime mover to the transmission in automobiles, construction machinery, agricultural machinery, motorboats, etc., transmits sufficient power at all times, but when starting, it provides a moderate amount of slippage, and the clutch of the transmission A function is required to cut off the power when switching. Friction type clutches are widely used as clutches that satisfy this function. Friction type clutches include dry type clutches that are used in dry conditions and wet type clutches that are used in oily liquid. The latter wet clutch is often used in the form of a multi-disc clutch as a component in planetary gear type automatic transmissions.

The friction plate of a wet type clutch has a structure in which a friction material 1 called a paper facing is attached to both sides of a core metal 2, as shown in FIG. 12 (exploded view). Friction material 1 is a base material made of cellulose with an inorganic filler such as graphite, asbestos, or ceramic, or an organic filler such as cashew dust impregnated with a thermosetting resin such as a phenolic resin or a melamine resin. . Such materials have a high coefficient of friction, are highly elastic, and are porous, so they have a good oil absorption rate, so they are currently used in large quantities as the best wet friction materials.

Friction type clutches generate frictional heat, so
In order for the above-mentioned functions to be stably performed, heat must be efficiently released from the frictional parts. In wet clutches, oil plays an important role as a heat transport medium. The heat generated on the friction surface is diffused and released throughout the system using oil as a medium. Therefore, if the amount of oil held in the friction material itself and the amount of oil flowing in and out are small, there will be no heat release and it will overheat, resulting in thermal deterioration of the friction material and oxidation and decomposition of the oil, resulting in a decline in its function as a friction material. . To prevent such a situation, grooves 3 (see FIG. 12) are provided on the surface of the friction material to allow oil to circulate. Wet friction materials provided with such grooves (groups) are disclosed in Japanese Patent Application Laid-Open No. 56-90135, or
Disclosed on pages 56-57 of NSK Bearing Journal (published by NSK Warner Co., Ltd.) No. 638 (published in 1979). As described in these documents, the grooves are formed by pressure molding or cutting.

[Problem that the invention seeks to solve]

Grooves formed by pressure molding can have a depth that is only about half the thickness of the friction material, which may be insufficient. In addition, there is a drawback that the molding surface is under high pressure and a large amount of resin is impregnated, which prevents oil from flowing in and out. On the other hand, forming grooves by cutting requires a large number of processing steps and becomes expensive. Cutting debris may adhere to the formed grooves, and fuzz may form on the edges of the grooves, which may get mixed into the oil during use and cause problems such as valve stays. In addition, the friction material sometimes chipped or partially peeled off. In general, wet friction materials obtained by providing grooves on the surface have not yet achieved sufficient performance.

If the porosity of the base material is increased throughout the wet friction material without providing grooves, it is possible to increase the amount of oil retained, improve oil permeability, and reduce seizure. However, mechanical strength decreases and delamination occurs, resulting in a friction material with poor durability. Similarly, by increasing the thickness of a friction material without grooves, it is possible to increase the amount of oil it retains, resulting in a significant improvement in terms of seizure. However, in a multi-disc clutch in an automatic transmission, a considerable number of friction materials are used in one transmission, so even a slight increase in the thickness of each friction material results in a considerable increase in overall dimensions. Therefore, it becomes inevitable that transmissions become larger and, by extension, automobiles become larger and heavier.

The present invention aims to solve the above-mentioned drawbacks and problems of conventional wet-type friction materials, and is a wet-type friction material that allows sufficient circulation of oil even without grooves and has sufficient mechanical strength even if it is thin. The aim is to provide this at a low price.

[Means for solving problems]

A wet friction material 10 according to the present invention for achieving the above object is shown in FIG. 1 (perspective view).
The base material of the wet friction material 10 contains cellulose and is impregnated with a thermosetting resin. Wet friction material 10 has a base material with a low porosity layer (high density layer, indicated by spots)
The wet friction material 10 has a layer 11 and a layer 12 with a high porosity (a layer with a low density, shown in white), and is configured such that the friction surface of the wet friction material 10 is flat.

[Effect]

The wet friction material 10 includes a layer 1 having a low porosity as a base material.
The layer 12 maintains strength and allows oil to circulate through the layer 12 having a large porosity. Since the friction surface of the wet friction material 10 is flat, its entire surface is covered with a mating material (not shown).
come into frictional contact with.

〔Example〕

A specific example and production process of the wet friction material 10 shown in FIG. 1 will be described below.

As the cellulose, for example, linter pulp is beaten with a large amount of water. A total of 10 to 50 parts by weight, preferably 20 to 40 parts by weight of an inorganic filler and an organic filler are added to the beating solution based on 100 parts by weight of the pulp, and the mixture is thoroughly stirred and mixed. Inorganic fillers are added to improve friction performance and heat resistance, and examples include barium sulfate, kaolin, clay, calcium carbonate, silicic acid, alumina, diatomaceous earth, asbestos, graphite, and ceramic, singly or in combination. mixed and used. Organic fillers are used singly or in combination in the same way as in cashew dust. The base material of the wet friction material is made from the above-mentioned cellulose and filler.

FIG. 2 shows a schematic diagram of a circular mesh paper machine that makes paper while adding a watermark pattern using the watermark method. The beaten mixture 20 obtained as described above is placed in a papermaking tank 21. Paper is made by a conventional method using a circular mesh cylinder 22, an endless felt belt 23, and a couch roll 24. FIG. 3 is an enlarged view of the AA cross section of this portion.
A projection 22a corresponding to a watermark pattern to be inserted is provided on the surface of the cylinder 22. paper animal 25
The surface of is depressed by the protrusion 22a, and a pattern is formed in the unevenness of the thinned portion (concave portion) 25a and the thick portion (convex portion) 25b. In this state, the paper web 25 advances in the direction of the arrow and is pressed between press rolls 27a and 27b. B-B of this part
FIG. 4 shows an enlarged cross-section. The surfaces of the convex portions 25b and concave portions 25a of the paper web 25, as shown by chain lines in the figure, are pressed flat by the surface of the press roll 27b. The convex portions 25b are pressed more than the concave portions 25a, resulting in a layer 11 with a higher density of the base material and a lower porosity. The concave portions 25a are not pressed much, and the density of the base material does not change much, resulting in a layer 12 with a high porosity. In other words, the layer 12 with high porosity becomes the watermark pattern portion of the paper web 25.

A paper with a watermark pattern added in this way 2
5 is dried with a dryer roll 29, and then subjected to sizing processing with size rolls 30a and 30b,
Furthermore, it is completely dried by dryer rolls 31 and 32. Then, it is wound onto a reel 34 under tension by a tension roll 33.

After impregnating this paper material with phenolic resin,
Heat and cure to obtain wet friction material material. As shown in FIG. 5, a ring shape, which is the shape of the wet friction material, is punched out in alignment with the horizontal and vertical watermark patterns of the material 35 of the wet friction material. In this way, the wet friction material 1 having layers 11 and 12 with different porosities as shown in FIG.
0 is obtained.

Note that the impregnation with the resin may be performed after punching. It may also be carried out in the middle of the papermaking process. For example, as shown in FIG. 7, an aqueous solution 41 of phenolic resin is sprayed using a sprayer 40 provided downstream of the couch roll 25. In this way, the resin will also be heated and hardened in the subsequent drying process.

FIG. 6 shows another example of punching, in which a wet friction material material 36 is punched into a 1/4 arc 38 having protrusions 38a and depressions 38b. 4 pieces of that 1/4 arc 38,
The wet friction material 10 is obtained by combining the protrusions 38a and the depressions 38b, respectively. In this case, the material 36
Even if the watermark pattern is in one direction, the wet friction material 10 has vertical and horizontal watermark patterns. It is also possible to reduce wasted material 36 (uncut portions).

8 to 10 show various embodiments of the wet friction material 10 to which the present invention is applied. The layer 12 having a high porosity (watermark pattern) is curved (FIG. 8), unidirectional (FIG. 9), and cross-shaped (FIG. 10).
Moreover, it is not limited to these shapes, and can be made into various shapes.

The wet type friction material 10 obtained as described above is attached to both sides of the core metal 2 (see FIG. 12) to form a friction plate of a wet type clutch.

Experiments and Results Experiments conducted to evaluate the performance of the wet friction material of the present invention and their results will be described below.

≪Prototype≫...This is a beaten mixture of 100 parts by weight of the wet friction material linter pulp of the present invention and 30 parts by weight of an inorganic filler and an organic filler. layer) density to 0.3 g/cm ³ and the density of the watermark part (layer with high porosity) to 1/2, 0.15 g/cm ³
Make paper into Watermark width 2mm, pitch 10mm. A wet friction material is made from this paper material.

<Comparison product 1>...Wet friction material is made from paper material that is made from the same raw materials as the conventional wet friction material/grooveless prototype and has the same density as the base portion of the prototype.

<Comparative product 2>...Conventional wet friction material with grooves Grooves with a width of 2 mm and a pitch of 10 mm are cut into a wet friction material made the same as Comparative product 1.

The three types of wet friction materials mentioned above were tested for durability using a SAENo.2 friction tester. This test repeatedly absorbs the energy of a rotating body rotating with inertia (friction stops the inertial rotation), and examines the cycle until the surface of the friction material burns due to the absorbed energy and turns black. be. A graph of the test results is shown in FIG. In the figure, the horizontal axis is the absorbed energy per unit area of the friction surface of the friction material (Cal/cm ² ), and the vertical axis is the cycle until it turns black due to the absorbed energy, that is, the thermal durability cycle (times).
It is. As can be seen from this graph, the thermal durability cycle of the prototype is clearly better than that of Comparative Product 1 and approximately equal to Comparative Product 2. However, with comparison product 2, there were some layers that peeled off during this test.
Some of the edges of the grooves were chipped off, and fine debris got mixed into the oil. This was not the case with the prototype.

〔Effect of the invention〕

Since the wet friction material of the present invention has a layer with high porosity, oil can circulate through the layer, cooling the friction surface sufficiently, and providing a clutch without seizure. Since the friction surface is flat, it is strong and free from the risk of layer peeling or chipping unlike conventional wet friction materials with grooves formed by cutting. There is no possibility of chips accumulating in the oil and causing problems such as valve stays. Moreover, since layers with high porosity and layers with low porosity are formed during the papermaking process, it can be made at low cost. In wet friction materials with grooves formed by pressure molding, the groove depth is limited, but in the wet friction material of the present invention, the porosity of the layer with high porosity corresponding to the grooves can be selected quite freely. In addition, the porosity of the entire base material is not increased, but because there are many layers with low porosity, mechanical strength is maintained there, and even if the thickness is reduced, the overall strength becomes strong.

As explained above, according to the present invention, it is possible to provide a wet friction material that is free from seizure and is thin but durable at a low cost.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a wet friction material to which the present invention is applied, FIG. 2 is a diagram explaining the manufacturing process of the wet friction material, FIG. B cross-sectional enlarged view, Figures 5 and 6 are diagrams explaining punching of wet friction material from raw material, Figure 7 is a partially modified view of the manufacturing process, and Figures 8 to 10 are various implementations of wet friction material. FIG. 11 is a plan view of an example, and FIG. 11 is a diagram showing the performance test results of a wet friction material. FIG. 12 is an exploded perspective view of a friction plate using a conventional wet friction material. 1, 10... Wet friction material, 2... Core metal, 11...
... Layer with low porosity, 12 ... Layer with high porosity, 20 ... Beating mixture, 21 ... Paper making tank, 22
... cylinder, 22a ... protrusion, 23 ... felt belt, 24 ... couch roll, 25 ... paper web, 25a ... recess, 25b ... protrusion, 27a,
27b...Press roll, 35, 36...Material,
41...Phenol resin solution.

Claims (1)

[Claims] 1. A wet friction material in which the base material contains at least cellulose and is impregnated with a thermosetting resin, characterized in that the base material has layers with different porosity and the friction surface is flat. wet friction material.