CN117561383A

CN117561383A - Single layer dry friction lining

Info

Publication number: CN117561383A
Application number: CN202280045306.1A
Authority: CN
Inventors: I·阿利克斯; K·福伊尔; P·佩雷特
Original assignee: Valeo Materiaux de Friction SAS
Current assignee: Valeo Materiaux de Friction SAS
Priority date: 2021-06-29
Filing date: 2022-06-23
Publication date: 2024-02-13
Also published as: EP4363738A1; FR3124563A1; WO2023274833A1; KR20240027753A; FR3124563B1

Abstract

The invention relates to a single-layer dry friction lining for a motor vehicle clutch device, comprising-45 to 55% by weight, relative to the total weight of the lining, of a reactive material based on a thermosetting resin, a rubber and a lubricating filler, -a fibre-based material comprising glass fibres, organic fibres and metal fibres, the lining having a weight ratio between organic fibres and glass fibres of 0.05 to 0.25, preferably between 0.1 and 0.2, the metal fibres being copper fibres, the weight percentage of copper fibres being between 1 and 10%, preferably between 5 and 10%, relative to the total weight of the lining.

Description

Single layer dry friction lining

Technical Field

The present invention relates to a single layer friction lining for a motor vehicle clutch device. The friction lining according to the invention can therefore be used in particular in dry transmissions, such as double dry clutches, clutches for manual transmissions or automated gearboxes (AMTs).

Background

A typical dry-operated motor vehicle clutch includes a friction plate bearing on each face thereof friction linings fixed to an optionally common support. The support is fixed to a ribbed hub that engages the input shaft of the gearbox. Torsional dampers are typically interposed between the support of the friction lining and the ribbed hub. Furthermore, a progressive device is typically placed between two friction linings.

In use, the friction disc is placed between a reaction disc, which is firstly directly or indirectly connected to the crankshaft of the motor vehicle, and a pressure disc of a clutch mechanism comprising a cover and an annular diaphragm connected to the reaction disc, so as to axially push the pressure disc, which is rotationally connected to the cover, while being axially movable in a limited manner with respect to the cover.

In the engaged position, the linings of the friction disc are clamped between the reaction disc and the pressure disc, so that the rotational torque of the heat engine is transmitted to the gearbox input shaft.

The friction linings must be able to transfer the torque of the engine to the gearbox and vice versa. For this purpose, the lining must have good mechanical resistance under different radial, axial and circumferential stresses, with or without shearing of the material under load, with or without thermal stress, and good heat resistance, i.e. it must have mechanical resistance after being subjected to thermal damage and not lose its friction capacity (not slip) at high temperatures. Furthermore, the friction lining must have a relatively high and uniform coefficient of friction on the surface of the friction lining in order to transmit the engine torque to the gearbox. The friction lining must also have good wear resistance, i.e. its coefficient of friction must also remain substantially constant throughout the life of the clutch (at least after the initial running-in step). The thickness of the friction lining cannot vary too much during the service life of the clutch.

Furthermore, since the friction materials are composite materials, they will wear at the interface with the opposing material made of cast iron during high speed driving cycles. For asbestos-free materials, glass fibers are known to have an abrasive effect on cast iron. Such aggressiveness may lead to vibration phenomena, making the joint unpleasant. This is particularly important for dual dry clutch friction linings, which require friction materials with high comfort in view of automatic control of the gearbox. This comfort must be kept stable for a long period of time, i.e. throughout the use of the clutch material. In dual clutches, thermal safety exists, which is controlled by the transmission control software, so the friction material must be thermally stable at higher temperatures.

It is known in the art to use a mixture of glass fibers, organic fibers and copper fibers in a friction lining. Document EP0183335 discloses a composition of this type, for example. However, it has been found that this type of formulation makes it impossible to obtain friction clutches with satisfactory mechanical strength.

Disclosure of Invention

The object of the present invention is to propose a friction lining which solves the above-mentioned problems.

To this end, the subject of the invention is a single-layer dry friction lining for a clutch device of a motor vehicle, comprising:

-45-55 wt% relative to the total weight of the lining is made of reactive materials, said materials comprising thermosetting resins, rubber and lubricating fillers;

a fiber-based material comprising glass fibers, organic fibers and metal fibers,

the weight ratio of organic fibers to glass fibers of the liner is between 0.05 and 0.25, preferably between 0.1 and 0.2,

wherein the metal fibers are copper fibers, the weight percentage of copper fibers is between 1 and 10%, preferably between 5 and 10% with respect to the total weight of the lining.

Thus, the friction lining according to the invention may achieve improved thermal, mechanical and comfort performance levels due to the specific weight ratio between the organic fibers and the glass fibers, combined with the specific amount of copper fibers.

This type of combination thus increases the heat resistance and mechanical resistance in use, in particular after thermal abuse, increases the friction level, stabilizes the comfort level after wear, and limits the aggressiveness of the material with respect to the counter material.

The subject of the invention is also a clutch device for a motor vehicle comprising a friction lining according to the invention.

The invention and its advantages will be readily understood from the following description and examples.

Drawings

Figure 1 shows the mechanical resistance (rpm before break) according to the weight ratio between the organic and glass fibers of the three friction linings.

Fig. 2 shows the ability to withstand torque under severe conditions of high load, i.e. the grade stress of an empty trailer (hill start).

Fig. 3 shows the change in the excitation coefficient as a function of the temperature of the two friction linings.

Fig. 4 shows the mechanical resistance (rpm before break) according to the weight ratio between the organic fibers and the glass fibers of the three friction linings.

Fig. 5 shows the ability to withstand torque under severe conditions of high load, i.e. the grade stress of an empty trailer (hill start).

Fig. 6 shows the development of the excitation coefficients according to the temperature of three friction linings.

Detailed Description

In the present invention, unless otherwise indicated, all percentages indicated are weight percentages relative to the total weight of the friction lining.

In the context of the present invention, "thermal abuse" refers to a liner after a stress of 360 ℃ for 3 hours. This corresponds to the temperature at which the organic binder of the friction lining may be damaged due to the breaking of chemical bonds, and the resistance of the material in centrifugation may be reduced.

Furthermore, any numerical interval specified by the expression "between a and b" refers to the numerical range from a to b (i.e., includes strict limits a and b).

The weight ratio between the organic fibers and the glass fibers of the friction lining according to the invention, i.e. the weight of the organic fibers divided by the weight of the glass fibers, is between 0.05 and 0.25, preferably between 0.1 and 0.2.

The fiber-based material includes glass fiber, organic fiber and metal fiber. The fibers are continuous strands that ensure resistance to centrifugal forces and provide thermal properties to the material. "continuous fibers" refers to fibers having discontinuities at substantially only the ends of the strands.

Advantageously, the organic fibers are selected from fibers of Polyacrylonitrile (PAN), cellulose, aramid, hemp, flax, and mixtures thereof. Preferably, the organic fibers are composed of polyacrylonitrile fibers.

Advantageously, the friction lining is free of carbon fibers. In fact, carbon fibers are relatively costly and can reduce friction at high temperatures. According to the present invention, "carbon fiber" means a fiber composed of only carbon. Thus, carbon fibers are different from fibers comprising carbon, such as in the case of organic fibers selected from the group consisting of Polyacrylonitrile (PAN), cellulose, aramid, hemp, flax fibers, and mixtures thereof.

The glass fibers may be roving type and/or textured. When fibers are gathered together in strands by sizing, they are called rovings. The deformed or volumetrically expanded fibers are obtained from the roving fibers by injecting air to open a portion of the roving fibers. This has the effect of allowing the matrix (in this case the agent contains resin, rubber and filler) to impregnate the fibres better towards the core.

Advantageously, the glass fibers are present in the friction lining in a weight percentage of 30 to 45% with respect to the total weight of the friction lining, and preferably strictly greater than 30%.

Advantageously, the glass fibers have a linear density between 600 and 2500 dtex. The organic fibers have a linear density of between 400 and 800 dtex, preferably about 600 dtex. The cross section of the copper fiber is between 100 and 200 μm.

Advantageously, the friction lining has a content of 1.7 to 1.85g/cm in a solvent such as water ³ Or hydrostatic density.

Advantageously, the thermosetting resin is a phenolic resin, such as a novolac resin and/or a melamine formaldehyde resin. Preferably, a high molecular weight resin, i.e., 2000-6000 g/mol, is used.

Advantageously, the rubber latex is of the nitrile rubber (NBR) type and may be carboxylated or non-carboxylated.

Advantageously, in the friction lining, the resin, rubber and lubricating filler are present in an amount of 35-45% by weight relative to the total weight of the lining.

Advantageously, the reactive materials include vulcanization catalysts and other fillers in addition to resins, rubbers and lubricating fillers.

Typically, the sulfiding catalyst is sulfur or zinc oxide. The other filler is advantageously chosen from the so-called "friction" fillers. For example, this type of filler may be chosen from carbon black, barium sulphate, activated carbon, kaolin, hollow microspheres (in particular made of glass) or calcium carbonate.

Advantageously, the lubricating filler consists of mineral filler and/or graphite, in a percentage by weight of between 3% and 10%, preferably between 3% and 8%, with respect to the total weight of the lining.

Thus, in friction materials, the base fiber material is impregnated with a reactive material, which may also be referred to as aqueous cement, i.e. impregnated cement penetrates into the spaces between the different fibers of the wire, around the fibers, around the bundles of fibers and/or into the core of the fibers.

Advantageously, the lubricating mineral filler is composed of a metal sulphide, preferably selected from iron sulphide, copper sulphide, zinc sulphide, molybdenum disulphide, tin sulphide, tin disulphide and mixtures thereof.

The graphite is, for example, synthetic or natural graphite.

Typically, graphite comprises 30-100% by weight of the lubricating filler.

Advantageously, the lubricating fillers have different densities, the mass fraction ratio of the lubricating filler between the minimum density filler and the maximum density filler being between 0.6 and 4. The use of different densities of the lubricating fillers balances and stabilizes the performance levels of the friction material in thermal lubrication, thereby preventing the occurrence of uncomfortable vibration phenomena. This has the additional effect of providing friction material with friction and wear resistance.

According to the present invention, "mass fraction ratio between the least dense filler and the most dense filler" means the quotient of the mass fraction of the least dense lubricating filler divided by the mass fraction of the most dense lubricating filler. The mass fraction ratio of the lubricating filler between the minimum density filler and the maximum density filler within the specified range has the effect of distributing the lubricating filler having a uniform composition within the reactive material.

The performance levels of the lubricating fillers that function in different temperature ranges overlap. Furthermore, each filler is uniformly distributed inside the reaction material. Thus, the reactive material makes it possible to provide a friction material that can regulate vibrations in a balanced and stable manner in thermal lubrication.

Preferably, the mass fraction ratio of lubricating filler between the filler of minimum density and the filler of maximum density is equal to 1.25 or more, preferably equal to 1.3 or more, preferably equal to 3 or less, preferably equal to 2 or less, preferably equal to 1.8 or less, preferably equal to 1.6.

Preferably, the mass fraction ratio of the lubricating filler between the graphite and the mineral filler, i.e. the quotient of the mass fraction of graphite divided by the mass fraction of mineral filler, is equal to 1 or more and equal to 3 or less.

Preferably, the mass fraction ratio of the lubricating filler between the graphite and the most dense mineral filler, i.e. the quotient of the mass fraction of graphite divided by the mass fraction of the most dense mineral filler, is equal to 0.65 or more and equal to 1 or less, preferably equal to 0.8.

According to an embodiment, the particle size (defined by the median diameter) of the lubricating filler is equal to or greater than 5 μm and equal to or less than 30 μm. In other words, each lubricating filler defined by the chemical composition is composed of particles of variable diameter. The median diameter of the particles is equal to or greater than 5 μm and equal to or less than 30 μm.

In fact, for the same mass composition, a fine particle size measurement provides better wear resistance for the friction material, as the contact surface area between the particles and the rubber is increased.

Preferably, the particle size of the lubricating filler is equal to 20 μm or less.

According to some embodiments, the density of the lubricating filler is equal to or greater than 2 and equal to or less than 8.

According to some embodiments, the reactive material may include one or more additives, such as at least one surfactant and/or at least one thickener.

The surfactant may be anionic, for example a polyphosphate of sodium, potassium or ammonium, or a sulfonate of sodium, potassium or ammonium, or a sulfate of sodium, potassium or ammonium. The surfactant may be nonionic, such as polyacrylate or polyvinyl alcohol.

The thickener may comprise cellulose or calcium silicate. The cellulose may be of the colloidal microcrystalline cellulose type.

Advantageously, the friction lining comprises (percentages are given by weight relative to the total weight of the lining):

-45 to 55% of a reactive material comprising:

27-42% of a mixture of phenolic resin and melamine/formaldehyde and NBR-type rubber;

3% to 10% of a lubricating filler;

1-10% of sulfided catalyst and other fillers;

-5 to 10% copper fibres;

-30 to 45% glass fibers;

-3 to 8% polyacrylonitrile fiber.

Several examples of friction linings are given below. Hereinafter, the constitution of the lining is expressed in weight percent, and the percentages are given in weight added to the total weight of the lining. Weight ratio between Polyacrylonitrile and glass fiber with R _Mac/Mv And (3) representing.

_Mac/Mv Example 1 comparative examples with respect to liners, ratio R, one outside the claimed range (comparative examples _Mac/Mv Example A1) and two liners in a ratio R, within the scope of the invention (examples according to the invention, B2 and B3)

The friction material had the composition given in table 1 below.

The reactive materials comprising the mixture of phenolic resin and melamine/formaldehyde, NBR rubber, lubricating filler and friction filler are the same in the three examples and are present in 45-55% by weight.

TABLE 1

Composition of the components	Comparative example A1	Inventive example B2	Inventive example B3
				Glass fiber	28％	36％	33％
Polyacrylonitrile fiber	13％	4％	7％
				Copper fiber	7％	9％	8％
R _Mac/Mv	0.47	0.11	0.21

Figures 1 and 4 show the mechanical resistance (rpm before break) between polyacrylonitrile fiber and glass fiber according to the weight ratio. As shown in fig. 1, the friction linings of B2 and B3 have higher mechanical resistance than A1. In fact, the tests carried out showed that the friction lining according to the invention (external diameter 240mm, internal diameter 160mm, thickness 3.7 mm) bursts after reaching 12800rpm (B3) and 13400rpm (B2) after heating to 200℃in contrast to a lining A1 of 12000rpm. The composition of the material makes it possible to maintain this level of resistance after stress at higher temperatures, in particular after thermal abuse.

Figures 2 and 5 show the ability to withstand torque under severe conditions of high load, i.e. under gradient stress of an empty trailer (hill start), depending on the weight ratio between the polyacrylonitrile fiber and the glass fiber. In this test, the friction material was subjected to an energy cycle simulating a 12% hill start. The test starts with 300 run-in phases of low surface energy (9 kJ,100 ℃) followed by a first x-ramp start cycle test (each cycle lasting 60 seconds with a surface energy of 101 kJ) until slip occurs (i.e. a friction coefficient < 0.2), followed by a recovery phase of 300 cycles (9 kJ,100 ℃) followed by a new y-ramp start cycle test (each cycle lasting 60 seconds with a surface energy of 101 kJ). The number of hill starts is determined by the sum of (x+y). The higher the sum of (x+y), the greater the torque the liner can withstand under severe conditions.

As can be seen from fig. 2, with the friction lining (B2, B3) according to the invention, the number of hill starts performed before slipping is greater than that obtained with the comparative friction lining (A1). Thus, the stability of the friction level with B2 and B3 is improved.

FIGS. 3 and 6 show the excitation coefficient (N.m.s) according to temperature (. Degree. C.). To measure the excitation coefficient, the first phase is performed for 100 cycles, during which for each cycle 35kJ of energy is supplied to the continuously sliding material, the temperature increases by 40 to 350 ℃ (3 cycles per minute). The second stage of material recovery was carried out with 100 cycles of lower energy (15 kJ) and a temperature of 80-120 ℃. These two phases are repeated six times. The graph is the maximum of all excitation points measured in the first phase.

Vibration is measured by excitation coefficients. If this is positive, this means discomfort (vibration felt by the passenger space during shifting), the more negative the coefficient, the less vibration the material produces, improving the comfort during shifting of the gearbox.

As can be seen in fig. 3, the liner B3 can improve comfort at negative excitation coefficients up to 350 c, while the liner A1 is a vibration source when the temperature exceeds 310 c.

Wear and roughness (roughness before 2 μm test) of cast iron mating materials in the clutches in table 2 were also measured.

TABLE 2

Thus, the composition of B3 relative to A1 makes it possible to reduce the aggressiveness of the resist material in the clutch and thus increase the durability of the system.

Example 2 comparative examples relate to two liners with copper content outside the scope of the claims (comparative examples C1 and C2) And a facing B2

The friction material had the composition given in table 3 below.

The reactive materials comprising the mixture of phenolic resin and melamine/formaldehyde, NBR rubber and lubricating filler are identical in examples B2 and C2 and are present in a weight percentage of 45 to 55%. C1 differs from B2 and C2 in that the reactive material is free of lubricating fillers and is free of SBR type rubber.

TABLE 3

Composition of the components	Comparative example C1	Comparative example C2	Inventive example B2
				Glass fiber	23％	23％	36％
Polyacrylonitrile fiber	5.5％	5.5％	4％
				Copper fiber	20％	20％	9％
R _Mac/Mv	0.246	0.246	0.11
				Density of material g/cc	1.91	1.91	1.78

As shown in fig. 4, the friction lining of B2 has a higher mechanical resistance than C1 and C2. In fact, the tests carried out showed that the friction lining outside the present invention bursts when heated to 200℃after reaching 10300rpm (C1) and 11300rpm (C2) compared with 13400rpm of the lining B2.

Fig. 5 shows that for materials filled with C2 copper, the replacement of the active material makes it possible to greatly increase the thermal resistance of the material, but a compromise needs to be found between comfort, mechanical resistance and thermal resistance. B2, which contains less copper than C1, achieves an improved level of thermal resistance.

In fact, fig. 6 shows that the liner B2 provides the best compromise in terms of comfort, with a negative excitation coefficient up to 315 ℃, whereas the liners C1 and C2 are sources of vibration at temperatures exceeding 200 ℃ and 275 ℃, respectively.

It will be appreciated that the foregoing description is provided by way of example only and is not limiting as to the scope of the invention, which is not to be construed as a departure from the invention by substituting different elements with any other equivalent.

Furthermore, different features, variations and/or embodiments of the invention may be associated with each other in various combinations, provided that they are not mutually incompatible or mutually exclusive.

Claims

1. A single layer dry friction lining for a motor vehicle clutch device comprising:

characterized in that the metal fibers are copper fibers, the weight percentage of which is between 1 and 10%, preferably between 5 and 10%, relative to the total weight of the lining.

2. A friction facing as set forth in claim 1 wherein said organic fibers are selected from the group consisting of polyacrylonitrile fibers, aramid fibers, cellulose fibers, hemp fibers, flax fibers and mixtures thereof.

3. A friction lining as claimed in claim 1 or claim 2 which is free of carbon fibres.

4. A friction lining as claimed in any one of the preceding claims wherein the rubber is nitrile rubber.

5. A friction lining as claimed in any one of the preceding claims wherein the thermosetting resin is a phenolic resin and/or melamine formaldehyde.

6. A friction lining as claimed in any one of the preceding claims wherein the lubricating filler is comprised of mineral filler and/or graphite in a weight percentage of between 3% and 10% relative to the total weight of the lining.

7. A friction lining as set forth in claim 6 wherein said lubricating mineral filler is comprised of a metal sulfide.

8. A friction lining as claimed in any one of the preceding claims wherein the lubricating fillers have different densities, the mass fraction ratio of lubricating filler between the minimum density filler and the maximum density filler being between 0.6 and 4.

9. Clutch device for a motor vehicle, characterized in that it comprises a dry friction lining according to any one of claims 1 to 8.