WO2013104870A1

WO2013104870A1 - Method for the production of a clutch friction lining

Info

Publication number: WO2013104870A1
Application number: PCT/FR2013/050059
Authority: WO
Inventors: Loïc ADAMCZAK; Jean-Pierre Boutaud; Pascal DEGERY; Daniel DESSE
Original assignee: Valeo Materiaux De Friction
Priority date: 2012-01-12
Filing date: 2013-01-10
Publication date: 2013-07-18
Also published as: CN104136794A; JP2015507151A; FR2985795A1; DE112013000552T5; FR2985795B1; KR20140114865A; JP6158224B2

Abstract

The invention relates to a method for the production of a clutch friction lining (4), comprising the following steps consisting in: producing a friction body (6) including at least one groove (10) that opens only at a first surface of the body (6); attaching the friction body (6) to a support (5) by adhering the first surface of the body (6) to the support (5); and machining a second surface (8) of the friction body (6), opposite the first surface, until the aforementioned groove (10) opens at the second surface (8) of the friction body (6).

Description

Method of producing a clutch friction lining

The present invention relates to a method of producing a friction lining, intended to equip a friction disc of an automobile clutch, in particular a double clutch.

A double clutch allows coupling the motor shaft of the vehicle with one or the other of two coaxial input shafts of a gearbox, which can be of the robotic type.

Thus, a dual clutch allows to change gears while maintaining the transmission of a torque engine to the vehicle wheels. Indeed, the two clutches are respectively associated with even and odd gear ratios. During a gearshift, a first clutch is disengaged while the second clutch is engaged, so that the engine torque is progressively transferred from the first to the second clutch.

Each clutch comprises a mechanism comprising a diaphragm for cooperating with a pressure plate integral in rotation with the cover and the motor shaft. Each diaphragm is movable by means of a corresponding clutch abutment, between a rest position and an active position. Depending on the type of clutch, the active position of the diaphragm corresponds to a coupling or decoupling of the shafts of the engine and the gearbox and the rest position of the diaphragm corresponds to a decoupling or a coupling of these shafts. These are respectively a normally open clutch and a normally closed clutch.

The clutch stop is controlled by an actuator controlled by an electronic computer to exert a predetermined force on the diaphragm and move it over a given distance.

The pressure plate of each clutch, urged by the corresponding diaphragm, is intended to clamp a friction disk, equipped with friction linings, on a reaction plate connected to the shaft. engine. A reaction plate may be provided for each clutch. Alternatively, a single reaction plate common to both clutches, mounted between the two friction discs, is used.

The friction linings are intended to come into contact with the counter-materials of the pressure plates and the reaction plate or plates.

Each friction disk is rotatably connected to an input shaft of the gearbox and each reaction plate is rotatably connected to a flywheel connected to the drive shaft. Thus, the clamping of a friction disk between the corresponding pressure and reaction plates allows the transmission of a torque between the drive shaft and the shaft of the associated gearbox.

It is essential that only one of the clutches transmits torque. Otherwise, there is a risk of blockage in the gearbox and thus a risk of locking wheels.

A packing is conventionally composed of an annular friction body formed of a fibrous material, a binder and fillers. The friction body is fixed on a support formed by a metal ring foil, by pressing or gluing, for example.

A lining is fixed on each of the radial faces of the friction disk, the counter-materials of the pressure plate and the corresponding reaction plate bearing on the friction bodies of the linings.

In operation, the linings are subjected to high thermal and mechanical stresses. Differential thermal expansions may further appear between the friction body and the foil serving as support. This can cause detachment or bursting of the friction lining, the fragments coming off the friction lining can block one or both clutch mechanisms of the double clutch which can then transmit simultaneously a torque to the two input shafts of the gearbox, causing a blockage of the gearbox and wheels.

In order to avoid this, the patent application FR 2 927 966 proposes a friction lining whose annular body comprises a first radial wall attached to a foil and a second radial wall, opposite to the first wall, in which are provided grooves . These are obtained individually by mechanical machining or by laser machining, which is relatively long and expensive.

The grooves are such that, in case of bursting, the fragments of the friction body have relatively small dimensions and do not risk causing a blockage of one of the clutch mechanisms of the double clutch.

The grooves provided on the friction bodies also allow, in operation, to generate aeraulic forces promoting the detachment of the friction disk relative to the pressure plate and the reaction plate, in the disengagement phase. The geometries of the grooves can be adapted according to the aeraulic forces to be generated.

These grooves can also be used to more easily remove particles created by the wear of the friction body, or to improve the heat exchange so as to reduce the temperature of the friction body and / or the support.

The grooves are also generally involved in reducing the deformation of the liners and ensuring their flatness, and thus reduce the risk of premature deterioration and increase the performance of the clutch.

The studies conducted by the Applicant have revealed that, in terms of non-deformation and flatness of the lining, the grooves are generally more effective if they open outwards and opposite the support, that is to say say if they completely cross the friction body. However, the prior art does not propose any simple and inexpensive method for producing a liner free of friction material in the groove bottom, that is to say whose grooves open opposite the corresponding support.

The invention aims in particular to provide a simple, effective and economical solution to this problem.

For this purpose, it proposes a method of producing a clutch friction lining, characterized in that it comprises the steps of:

- producing a friction body having at least one groove opening only at a first face of the body,

fixing the friction body on a support, by adhesion of the first face of the body to the support,

machining a second face of the friction body, opposite to the first face, until said groove opens at the second face of the friction body.

In this way, at the end of the manufacturing process, the friction body is fixed on the support and comprises at least one groove opening outwards, that is to say at the level of the second face, and opening on the support, that is to say at the level of the first face. The lining therefore has no friction material at the bottom of the groove, which makes it possible to limit its deformations and to improve its flatness during operation.

Of course, the invention is not limited to the technical field of double clutches.

According to a characteristic of the invention, the friction body is in the form of an annular friction body fixed on a ring-shaped support.

Advantageously, the friction body is made by molding under pressure in a mold comprising a fixed part comprising a first impression and a movable piston comprising a second imprint, at least one of said indentations having a projecting portion adapted to form the groove during molding.

For example, the temperature inside the mold during the molding under pressure can be between 150 ° C and 250 ° C, preferably between 180 and 200 ° C. In addition, the pressure inside the mold can be increased gradually over time, this pressure being up to a maximum of between 200 and 300 bars.

The friction body may comprise at least one fibrous material, at least one binder and at least one filler.

In this case, the molding of the friction body can be carried out hot, so as to polymerize the binder, at least in part.

The friction body must, after the die casting, have sufficient strength to be fixed on the support.

By way of example, the degree of polymerization at the end of this molding operation can be between 50 and 90%, and is preferably of the order of 70%.

In addition, after molding of the friction body, the support can be affixed to the first face of the friction body and then hot pressed against said friction body, until complete polymerization of said binder and adhesion of the friction body to the support.

For example, the temperature during this step may be between 150 ° C and 250 ° C, and preferably between 180 and 200 ° C. The pressure applied to the support may be between 200 and 300 bar.

Alternatively, the friction body is fixed to the support by gluing.

In this case, the friction body can be glued to the support with a phenolic resin glue.

In order to improve the adhesion between the friction body and the support, the face of the support on which the friction body is intended to be fixed is prepared by shot blasting or chemical etching, and / or is coated with a primer. hooking. Preferably, the second face of the friction body is machined by grinding, until said groove opens at the second face of the friction body.

Machining by grinding of the entire second face of the friction body can be achieved easily, quickly, and cheaply.

In particular, when the friction body has a plurality of grooves, all the grooves can lead at one time to the level of the friction face, in a single grinding step. It is recalled that in the prior art, on the contrary, each groove is machined individually by mechanical machining or by laser machining.

Finally, after machining the second face of the body, any particles present in the groove can be extracted, for example by suction.

The invention also relates to a clutch friction lining comprising a friction body intended to be mounted on a support, said friction body comprising at least one groove devoid of material at the bottom of the groove and devoid of machining traces in the bottom and groove walls.

The groove can be obtained by the manufacturing method described above.

The invention will be better understood and other details, characteristics and advantages of the invention will appear on reading the following description given by way of non-limiting example with reference to the accompanying drawings in which:

FIG. 1 is an exploded view, in perspective, of a friction disk of the prior art,

- Figures 2 to 7 are schematic views illustrating the various steps of the method of producing a friction lining according to the invention.

FIG. 1 represents a friction disc 1 of the prior art, comprising a splined hub 2 extending along the axis A, intended to be coupled to an input shaft of a gearbox, connected to a flange 3 extending radially outwardly from the splined hub 2. Annular friction linings 4 are mounted on either side of the flange 3 at its radially outer periphery.

Each friction lining 4 comprises a support, formed by an annular foil 5, that is to say a sheet of thin metal material, of thickness generally between 0.2 and 1 mm. The support can also be a plastic or a composite.

Annular friction bodies 6 are mounted on the faces of the foils 5 which are opposed to the flange 3. These bodies 6 are conventionally composed of a fibrous material, a binder and fillers, as is known in particular from the document FR 2 941,758, in the name of the Applicant.

Each friction body 6 has a radial fixing face 7, turned on the side of the corresponding foil, and a radial friction face 8, opposite to the fixing face 7.

The fixing faces 7 are for example glued on the corresponding foils 5 and the foils 5 are fixed to the flange 3 by rivets 9.

The friction faces 8 are intended to cooperate with a pressure plate and a reaction plate of a clutch mechanism, in particular a double clutch, so as to transmit a torque of a driving member, such as a crankshaft of a combustion engine, to a driven member, such as an input shaft of a gearbox.

As indicated above, grooves 10 are formed in the friction faces 8 of the friction bodies 6. The number, the arrangement and the section of the grooves 10 can be adapted as needed.

For the reasons stated above, it is sought to provide in a simple and inexpensive manner, friction bodies 6 having grooves 10 opening on both the friction face 8 and the attachment face 7, that is, that is, grooves 10 passing through the friction bodies 6. The invention proposes for this the following method, described with reference to FIGS. 2 to 7. These figures represent only a section B (FIG. 2) of an annular lining 4.

The method comprises a first step of producing a friction body 6 comprising at least one groove 10 opening only at the attachment face 7 of the body 6.

More particularly, as represented in FIG. 1, the friction body 7 is made by molding under pressure in a mold comprising a fixed annular portion 11 comprising a first cavity and a mobile annular piston 12 comprising a second cavity comprising at least a part protruding 13 capable of forming at least one groove 10 during molding. As in the prior art, the friction body 6 comprises at least one fibrous material, at least one binder and at least one filler.

The molding of the friction body 6 is carried out hot, so as to polymerize the binder, at least in part.

The temperature inside the mold during the molding under pressure can be between 150 ° C and 250 ° C, preferably between 180 and 200 ° C. In addition, the pressure inside the mold can be increased gradually over time, this pressure being up to a maximum of between 200 and 300 bars. The polymerization rate at the end of this molding operation can be between 50 to 90%, and is preferably of the order of 70%.

After removal of the mobile piston 12 (Figure 3), the method comprises a second step of fixing the friction body 6 on a support which, in this case, is an annular foil 5 of thickness between 0.2 and 1 mm.

For this, as shown in FIG. 4, the annular foil 5 is engaged in the fixed part 1 1 of the mold and placed on the attachment face 7 of the friction body 6. The preceding piston 12 is replaced by an annular piston 14 having a substantially flat face 15, facing the foil 5. The foil 5 is then pressed hot by the piston 14, against the friction body 6, until complete polymerization of said binder and adhesion of the friction body 6 to the foil 5.

In order to improve the adhesion, the face of the foil 5 on which the friction body 6 is intended to be fixed may be prepared by shot blasting or chemical etching, and / or may be coated with a primer, before hot pressing.

In a variant not shown, the friction body 6 is fixed to the foil 5 by gluing, using a glue based on phenolic resin.

After removal of the friction lining 4 from the mold (FIG. 5), the friction face 8 of the friction body 6, opposite the fixing face 7, is machined by grinding (FIG. 6) until the groove 10 opens out at the friction face 8 of the friction body 6 (Figure 7).

For this, the metal foil 5 is affixed to a magnetic table 16, so as to maintain in position the friction lining 4, the fastening face 8 of the friction body 6 being machined using a milling cutter 17. L The thickness of machined material is between 0.2 and 1 mm, preferably between 0.3 and 0.5 mm. The friction body 6 has, after grinding, a thickness between 1, 5 and 5 mm. Any particles of friction material present in the grooves are then extracted, for example by suction.

Although not shown in the drawings, the through holes of the rivets 9 and / or the riveting tool can be made in the same way as the grooves 10, or by drilling, if necessary.

In the embodiments that have been described, the grooves are annular. They could however have any other form, the number of grooves can also vary according to the needs.

Claims

1. A method of producing a clutch friction lining (4), characterized in that it comprises the steps of:

- producing a friction body (6) comprising at least one groove

(10) opening only at a first surface (7) of the body (6),

- fixing the friction body (6) on a support (5), by adhesion of the first surface (7) of the body (6) on the support (5),

machining a second surface (8) of the friction body (6), opposite to the first surface (7), until said groove (10) opens out at the second surface (8) of the friction body ( 6).

2. Method according to claim 1, characterized in that the friction body is in the form of an annular friction body (6), fixed on a support (5) of annular shape.

3. Method according to claim 1 or 2, characterized in that the friction body (6) is made by pressure molding in a mold having a fixed part (1 1) comprising a first cavity and a movable piston (12) comprising a second impression, at least one of said indentations having a projecting portion (13) adapted to form the groove (10) during molding.

4. Method according to claim 3, characterized in that the friction body (6) comprises at least one fibrous material, at least one binder and at least one filler.

5. Method according to claim 4, characterized in that the molding of the friction body (6) is carried out hot, so as to polymerize the binder, at least in part.

6. Method according to claim 5, characterized in that, after molding of the friction body (6), the support (5) is affixed to the first surface (7) of the friction body (6) and then pressed hot against said body of friction (6), until complete polymerization of said binder and adhesion of the friction body (6) to the support (5).

7. Method according to one of claims 1 to 6, characterized in that the friction body (6) is fixed to the support (5) by gluing.

8. Method according to claim 7, characterized in that the friction body (6) is bonded to the support (5) with a glue based on phenolic resin.

9. Method according to one of claims 1 to 8, characterized in that the face of the support (5) on which the friction body (6) is intended to be fixed is prepared by shot blasting or etching, and / or is coated with a primer.

Method according to one of claims 1 to 9, characterized in that the second surface (8) of the friction body (6) is machined by grinding (17), until said groove (10) opens at the the second surface (8) of the friction body (6).

1 1. Method according to one of claims 1 to 10, characterized in that, after machining the second surface (8) of the body (6), any particles present in the groove (10) are extracted, for example by suction.

12 - Clutch friction lining (4) comprising a friction body intended to be mounted on a support (5), said friction body comprising at least one groove (10) devoid of material at the bottom of the groove and devoid of traces machining in the bottom and walls of grooves.

13 - friction lining according to claim 12 obtained by the method according to one of claims 1 to 1 1.