KR20240027753A - Single layer dry friction lining - Google Patents

Abstract

The invention provides a composition comprising: 45 to 55% by weight, based on the total weight of the lining, of fine reactive substances based on thermosets, rubbers and lubricating fillers; and fiber-based materials including glass fibers, organic fibers and metal fibers, wherein the lining has an organic friction lining of 0.05 to 0.25, preferably 0.1 to 0.2. The metal fibers are copper fibers present in an amount of 1 to 10% by weight, preferably 5 to 10% by weight, based on the total weight of the lining.

Description

Single layer dry friction lining

The present invention relates to a single-layer try friction lining for clutch devices in automobiles. Therefore, the friction lining according to the invention can be used in particular in dry transmissions, such as double dry clutches, clutches for manual transmissions or robotized gearboxes (AMTs). You can.

Typically dry-operated automotive clutches comprise a friction disc bearing on each side a friction lining optionally fixed to a common support. The support body is fixed to a ribbed hub that engages the input shaft of the gearbox. A torsion damper is usually inserted between the support of the friction lining and the ribbed hub. Additionally, a progressiveness device is usually disposed between the two friction linings.

In use, the friction disc is firstly placed between a reaction plate connected directly or indirectly to the crankshaft of the car, and secondly, the pressure plate of the clutch mechanism is placed between a cover and a cover connected to the reaction plate. It includes an annular diaphragm, which can be axially displaced relative to the cover in a limited manner, axially thrusting a pressure plate that is rotatably connected to the cover.

In the engaged position, the lining of the friction disk is clamped between the reaction plate and the pressure plate so that the rotational torque of the thermal engine is transmitted to the gearbox input shaft.

The friction lining must be able to transmit the engine's torque to the gearbox and vice versa. For this purpose, the lining must have good mechanical resistance and good thermal resistance under various radial, axial and circumferential stresses, with or without shear of the material under load and with or without thermal stress, i.e. thermal damage. It must have mechanical resistance even after wearing and not lose its friction (no skidding) ability at high temperatures. Additionally, the friction lining must have a relatively high and uniform friction coefficient over its surface in order to transmit engine torque to the gearbox. The friction lining must also have good resistance to wear, i.e. the coefficient of friction must remain substantially constant throughout the service life of the clutch (at least after the initial running-in phase). The thickness of the friction lining must not change excessively during the service life of the clutch.

Additionally, because the friction material is a composite material, it wears out during the cycle passing at a given speed at the interface with the counter-material made of cast iron. For materials that do not contain asbestos, the abrasive effect of glass fibers on cast iron is known. This aggressiveness can lead to vibrations that make engagement uncomfortable. This is especially important in the case of double dry clutch friction linings, which therefore require friction materials with a high level of comfort, taking into account the automatic control of the gearbox. This level of comfort must be stable over the long term, i.e. throughout the life of the clutch material. In double clutches, the friction material must have thermal stability at higher temperatures since there is thermal safety controlled by the gearbox control software.

It is known in the prior art to use mixtures of glass fibers, organic fibers and copper fibers in friction linings. Document EP0183335 discloses, for example, compositions of this type. However, it has been found that formulations of this type do not make it possible to obtain friction clutches with satisfactory mechanical strength.

The purpose of the present invention is to propose a friction lining that can solve the problems described above.

For this purpose, the subject matter of the invention is 45 to 55% by weight, based on the total weight of the lining, of reactive substances based on thermosets, rubbers and lubricating fillers; and fiber-based materials including glass fibers, organic fibers and metal fibers, wherein the lining has a friction lining of 0.05 to 0.25, preferably It has a weight ratio between organic fibers and glass fibers of 0.1 to 0.2, and the metal fibers are copper fibers present at 1 to 10% by weight, preferably 5 to 10% by weight, based on the total weight of the lining.

Thus, the friction lining according to the invention makes it possible to obtain improved thermal, mechanical and comfortable performance levels thanks to the specific weight ratio between organic and glass fibers, associated with a specific amount of copper fibers.

Therefore, this type of association results in heat resistance during use, especially mechanical resistance after thermal abuse, improvement in the level of friction and stabilization of a comfortable level after wear and limitation of the aggressiveness of the material relative to the opposing material.

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

The present invention and its advantages will be readily understood through the following description and embodiments.

Figure 1 shows the mechanical resistance (rpm before rupture) as a function of the weight ratio between organic and glass fibers of three friction linings.
Figure 2 shows the ability to withstand torque under harsh conditions with high load, i.e. gradient stress (hill start) caused by an empty trailer.
Figure 3 shows the change in coefficient of excitation depending on the temperature of the two friction linings.
Figure 4 shows the mechanical resistance (rpm before rupture) according to the weight ratio of organic fibers and glass fibers of three friction linings.
Figure 5 shows the ability to withstand torque under harsh conditions with high load, i.e. gradient stress (hill start) with an empty trailer.
Figure 6 shows the change in excitation coefficient according to the temperature of the three friction linings.

In the present invention, unless otherwise specified, all percentages expressed are weight percentages based on the total weight of the friction lining.

In the context of the present invention, “thermal abuse” means the description of the lining after being stressed at up to 360° C. for 3 hours. This corresponds to the temperature at which the organic binders of the friction lining can be damaged due to rupture of chemical bonds and the resistance of the material when centrifuged can be reduced.

Additionally, any interval of values specified by the expression “between a and b” means a range of values from a to b (i.e., inclusive of the strict limits of a and b).

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

Fiber-based materials include glass fibers, organic fibers, and metal fibers. These fibers are continuous threads and can provide resistance to centrifugal forces and thermal properties of the material. “Continuous fiber” means a fiber that has substantially discontinuities only at the ends of the yarn.

Advantageously, the organic fibers are selected from the group consisting of fibers of polyacrylonitrile (PAN), cellulose, aramid, hemp, linen and mixtures thereof. Preferably, the organic fibers consist of polyacrylonitrile fibers.

Advantageously, the friction lining does not comprise carbon fibres. In fact, carbon fiber is relatively expensive and its friction deteriorates at high temperatures. According to the present invention, “carbon fiber” refers to a fiber composed solely of carbon. Accordingly, carbon fibers differ from fibers containing carbon, which may be in the case of organic fibers selected from the group consisting of polyacrylonitrile (PAN), cellulose, aramid, hemp, linen fibers and mixtures thereof.

Glass fibers may have a roving type and/or texture. Fibers are referred to as roving types when they are grouped together into strands produced by sizing. Textured or volumetric fibers are derived from roving fibers by opening part of the volume through air injection. This has the effect of allowing better impregnation of the fibers towards the core with the matrix (in this case a reagent comprising resin, rubber and fillers).

Advantageously, the glass fibers are present in the friction lining in an amount of 30 to 45% by weight, preferably strictly more than 30% by weight, based on the total weight of the lining.

Advantageously, the glass fibers have a linear density of 600 to 2,500 tex. The organic fibers have a linear density of 400 to 800 tex, preferably about 600 tex. The cross-sectional area of the copper fiber is 100 to 200 μm.

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

Advantageously, the thermosetting resin is a phenolic resin, for example of the Novolak and/or melamine formaldehyde type. Preferably, resins of high molecular weight, i.e. 2,000 to 6,000 g/mol, will be used.

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

Advantageously, in the friction lining, the resin, rubber and lubricating fillers are present in an amount of 35 to 45% by weight, based on the total weight of the lining.

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

Typically, the vulcanization catalyst is sulfur or zinc oxide. Other fillers are advantageously selected from so-called “friction” fillers. For example, fillers of this type may be chosen from carbon black, barium sulfate, activated carbon, kaolin, hollow microspheres (especially made of glass) or calcium carbonate.

Advantageously, the lubricating filler consists of mineral fillers and/or graphite in an amount of 3 to 10% by weight, preferably 3 to 8% by weight, based on the total weight of the lining.

Therefore, in friction materials, the basic fibrous material is impregnated by a reactive substance, also called water-based cement. That is, the impregnating cement penetrates between the different fibers of the yarn, around the fibers, into the space around the fiber strands and/or into the core of the fibers.

Advantageously, the lubricating mineral filler consists of a sulfide of a metal, preferably selected from the group consisting of iron sulfide, copper sulfide, zinc sulfide, molybdenum bisulfide, tin sulfide, tin bisulfide and mixtures thereof.

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

Typically, graphite represents 30 to 100% by weight of the lubricating filler.

Advantageously, the lubricating fillers have different densities and the mass fraction ratio of the lubricating fillers between the least dense and the most dense fillers is between 0.6 and 4. The use of lubricating fillers with different densities balances and stabilizes the performance level of the friction materials in hot lubrication, preventing vibration phenomena that cause discomfort. This has the additional effect of providing increased friction resistance and wear to the friction material.

According to the invention, “mass fraction ratio between the least dense and most dense fillers” 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 least dense filler and the most dense filler located in a certain range has the effect of distributing the lubricating filler in a homogeneous composition within the reactive material.

The performance levels of lubricating fillers operating in different temperature ranges overlap. Additionally, each filler is uniformly distributed inside the reactive material. Therefore, reactive materials make it possible to provide friction materials that can balance and stably control vibrations in high-temperature lubrication.

Preferably, the mass fraction ratio of lubricating filler between the least dense filler and the most dense filler is at least 1.25, preferably at least 1.3, and preferably at most 3, preferably at most 2, preferably at most 1.8. , preferably 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 the graphite divided by the mass fraction of the mineral filler, is greater than or equal to 1 and less than or equal to 3.

Preferably, the mass fraction ratio of the lubricating filler between the graphite and the densest mineral filler, i.e. the quotient of the mass fraction of the graphite divided by the mass fraction of the densest mineral filler, is at least 0.65 and at most 1, preferably 0.8. .

According to one embodiment, the granulometry of the lubricating filler, defined by the median diameter, is greater than or equal to 5 μm and less than or equal to 30 μm. In other words, each lubricating filler, defined by its chemical composition, is composed of grains with various diameters. The central diameter of the grains is greater than 5 μm and less than 30 μm.

In fact, for the same mass composition, finer granulometry gives the friction material better wear resistance because the contact surface area between the grains and the rubber increases.

Preferably, the granulometry of the lubricating filler is 20 μm or less.

According to some embodiments, the density of the lubricating filler is at least 2 and at most 8.

According to some embodiments, the reactive material may include one or more additives, such as one or more surfactants and/or one or more thickeners.

The surfactant may be of the anionic type, for example polyphosphates of sodium, potassium or ammonium, or sulfonates of sodium, potassium or ammonium, or sulfates of sodium, potassium or ammonium. The surfactant may be of the nonionic type, for example polyacrylate or polyvinyl alcohol.

Thickeners may include cellulose or calcium silicate. Cellulose can be of the colloidal microcrystalline cellulose type.

Advantageously, the friction lining comprises (% by weight based on the total weight of the lining):

- a mixture of 27 to 42% by weight of phenolic resin with melamine/formaldehyde and NBR type rubber; 3 to 10% by weight of lubricating filler; 45 to 55% by weight of reactive material, including 1 to 10% by weight of vulcanization catalyst and other fillers;

- 5 to 10% by weight of copper fibers;

- 30 to 45% by weight of glass fibers;

- 3 to 8% by weight of polyacrylonitrile fibers.

Some examples of friction linings are shown below. Hereinafter, the composition of the lining is expressed in weight percent, where the percent is given as the weight added to the total weight of the lining. The weight ratio between polyacrylonitrile fibers and glass fibers is given as R _Mac/Mv .

Example 1: Non-RM _ac/Mv A comparative example relating to a lining outside the claimed scope (Comparative Example A1), and a ratio RM within the scope of the invention _ac/Mv Two linings with (examples B2 and B3 according to the invention)

The friction material has the composition given in Table 1 below.

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

[Table 1]

Figures 1 and 4 show the mechanical resistance (rpm before rupture) between polyacrylonitrile fibers and glass fibers as a function of weight ratio. As can be seen in Figure 1, the friction linings of B2 and B3 have improved mechanical resistance compared to A1. In fact, according to the performed tests, the friction lining according to the invention (outer diameter 240 mm, inner diameter 160 mm, thickness 3.7 mm) operates at 12,800 rpm (B3) and 13,400 rpm (B2) compared to 12,000 rpm for lining A1. It was found to rupture after being heated to 200℃. The composition of the material makes it possible to maintain this level of resistance even after being stressed at higher temperatures, especially after thermal abuse.

Figures 2 and 5 show the ability to withstand torque under harsh conditions with high load, i.e. gradient stress (hill start) caused by an empty trailer as a function of the weight ratio between polyacrylonitrile fibers and glass fibers. The context of these tests In, the friction material undergoes an energy cycle simulating a 12% hill start. The test begins with a run-in phase of 300 cycles with low surface energy (9 kJ, 100°C), followed by a run-in phase of 300 cycles until slip occurs ( i.e. coefficient of friction less than 0.2), a first test using recuperation phase), followed by a new test using y hill start cycles (each cycle lasting 60 s with a surface energy of 101 kJ). The number of hill starts is determined by the sum of (x + y). (x The higher the sum of + y), the better the lining can withstand torque in harsh conditions.

As can be seen in Figure 2, for the friction linings (B2, B3) according to the invention, the number of hill starts performed before slipping is higher than that obtained for the comparative friction lining (A1). Accordingly, the stability of the friction level due to the linings B2 and B3 is improved.

Figures 3 and 6 show the excitation coefficient (N·m·s (seconds)) according to temperature (°C). To measure the excitation coefficient, the first stage is 100 cycles (3 cycles per minute) where, during each cycle, 35 kJ of energy is supplied to the material in continuous sliding and the temperature is increased from 40 to 350°C. It is carried out as The second stage of material recovery is carried out for 100 cycles at lower energy (15 kJ) and temperature between 80 and 120°C. The two steps are repeated six times. The graph is the maximum of all excitation points measured during the first step.

Vibration is measured by the excitation coefficient. If this is a positive number, it means discomfort (vibrations felt in the passenger space during gear changes), and the more negative the coefficient, the less the material generates vibrations, which increases the comfort when changing gears in the gearbox.

As can be seen in Figure 3, lining B3 can improve comfort with a negative excitation coefficient up to 350°C, while lining A1 becomes a source of vibration when the temperature exceeds 310°C.

The wear and roughness of the cast iron counter material in the clutch in Table 2 were also measured (roughness before testing 2 μm).

[Table 2]

Therefore, the composition of B3 compared to A1 makes it possible to reduce the aggressiveness of opposing substances in the clutch, thereby increasing the durability of the system.

Example 2: Comparative example of two linings with copper levels outside the claimed range (Comparative Examples C1 and C2) and Lining B2

The friction material has the composition given in Table 3 below.

The reactive material comprising a mixture of phenolic resin with melamine/formaldehyde, NBR rubber and lubricating filler is the same in Examples B2 and C2 and is present at 45 to 55% by weight. C1 differs from B2 and C2 in the absence of lubricating fillers of reactive substances and rubber of the SBR type.

[Table 3]

As can be seen in Figure 4, friction lining B2 has improved mechanical resistance compared to C1 and C2. In fact, the tests performed show that non-inventive friction linings heated to 200° C. ruptured after reaching 10,300 rpm (C1) and 11,300 rpm (C2), compared to 13,400 rpm for lining B2.

Figure 5 shows that for materials filled with copper C2, the heat resistance of the material can be significantly improved by replacing reactive materials, but a compromise must be found between comfort, mechanical resistance and heat resistance. Compared to C1, the use of B2, which contains less copper, improves the level of heat resistance.

In fact, Figure 6 shows that lining B2 provides the best compromise in terms of comfort with a negative excitation coefficient up to 315 °C, while linings C1 and C2 are the source of vibration when the temperature exceeds 200 °C and 275 °C, respectively.

It will be understood that the foregoing description has been provided purely by way of example and does not limit the scope of the invention, and that no departure is constituted by substitution of any other equivalent for different elements.

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

Claims (9)

A single-layer dry friction lining for an automobile clutch device, comprising:
The lining is
45 to 55% by weight of reactive materials, based on the total weight of the manufactured lining, including thermosets, rubbers and lubricating fillers; and
Fiber-based materials, including glass fibers, organic fibers, and metal fibers
Includes;
wherein the lining has a weight ratio between organic fibers and glass fibers of 0.05 to 0.25, preferably 0.1 to 0.2,
wherein the metal fibers are copper fibers present in an amount of 1 to 10% by weight, preferably 5 to 10% by weight, based on the total weight of the lining.
Friction lining. According to paragraph 1,
Friction lining, wherein the organic fibers are selected from the group consisting of fibers of polyacrylonitrile, aramid, cellulose, hemp, linen and mixtures thereof. According to claim 1 or 2,
Friction lining that does not contain carbon fiber. According to any one of claims 1 to 3,
Friction lining, wherein the rubber is of the nitrile-butadiene type. According to any one of claims 1 to 4,
Friction linings where the thermosetting resin is a phenolic resin and/or melamine formaldehyde. According to any one of claims 1 to 5,
Friction lining, wherein the lubricating filler consists of 3 to 10% by weight of mineral filler and/or graphite, based on the total weight of the lining. According to clause 6,
Friction lining in which the lubricating mineral filler consists of metal sulfides. According to any one of claims 1 to 7,
Friction lining, wherein the lubricating fillers have different densities and the mass fraction ratio of the lubricating fillers between the least dense and the most dense fillers is from 0.6 to 4. A clutch device for an automobile comprising the dry friction lining according to any one of claims 1 to 8.