WO2013104869A1

WO2013104869A1 - Method for the production of a clutch friction lining

Info

Publication number: WO2013104869A1
Application number: PCT/FR2013/050058
Authority: WO
Inventors: Loïc ADAMCZAK; Jean-Pierre Boutaud; Daniel DIJOUX; Frédéric VILLEPONTOUX; Eric LEJAMTEL
Original assignee: Valeo Materiaux De Friction
Priority date: 2012-01-12
Filing date: 2013-01-10
Publication date: 2013-07-18
Also published as: FR2985796A1; CN104185744A; KR20140111700A; JP2015507150A; FR2985796B1; DE112013000564T5

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 hole (10) that opens only at a first surface (7) of the body (6); attaching the friction body (6) to a support (5) by adhering the first surface (7) of the body (6) to the support (5); and machining a second surface (8) of the friction body (6), opposite the first surface (7), until the aforementioned hole (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 can alternately couple the motor shaft of the vehicle with 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.

A liner conventionally comprises an annular friction body composed 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 against the friction bodies.

The linings are fixed to the friction disk by rivets housed in the holes of the linings, the heads of the rivets bearing against either a countersink formed in the friction body, or against the foil.

Each rivet can be used to attach one or both pads to the friction disc. In the case where the rivets are used for fixing a single friction lining, holes located opposite the rivets must still be provided in the other lining, to allow the passage of a riveting tool.

In what follows we will focus on the case where the heads of the rivets come to bear against the foil, and not against a countersink formed in the friction body. This solution reduces congestion Axial of the assembly and is therefore particularly useful in the case of double clutches where the available axial space is limited.

In such a case, it should be ensured that the face of the foil located downhole and used to support the head of the rivet, is not covered with friction material.

Indeed, in the opposite case, the free thickness of a rivet varies from one rivet to another, which can cause a lack of parallel friction lining and generate vibrations or a phenomenon called "chatter" when the rotation of the friction disc in operation.

It is known to produce a friction lining by overmoulding or hot pressing, by placing a foil at the bottom of a fixed part of a mold, then by affixing a friction material composed of fibers, a binder and a at least one load, on the foil. The assembly is then pressed hot with the aid of a movable piston. During this operation, the friction material polymerizes to form a friction body that adheres to the foil.

As indicated above, the friction body must have holes for housing the heads of the rivets or allowing the passage of a riveting tool. The foil must also have holes, serving either the passage of the rivet rod or the passage of the riveting tool, depending on the intended fastening mode of the linings.

In a first embodiment, the holes of the friction body are made by drilling, using a drill or a milling cutter. In this case, it is a question of removing as much friction material as possible, without however damaging the foil which must serve to support the heads of the rivets.

In a second embodiment, the holes of the friction body are formed directly during the overmolding or hot pressing operation. In this case, the movable piston has protruding areas for forming said holes after hot pressing. In both cases, there is generally friction material downhole on the surfaces of the foil designed to form supports for the heads of the rivets.

In order to solve this problem, WO 201 1/009427 proposes to cover these areas of the foil with an interface layer aimed at reducing the adhesion of the friction material.

The friction material remaining downhole can then be removed by evaporation with the aid of a laser beam. The power of the laser beam is determined so that the foil is not damaged by the heat produced. Such a process is relatively long and expensive.

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 hole opening only at a first surface of the body,

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

machining a second surface of the friction body, opposite to the first surface, until said hole opens out at the second surface 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 hole passing through the friction body. The lining therefore does not include friction material down the hole, at the corresponding face of the support, intended to serve to support the head of a rivet.

The holes to be formed in the support for the passage of the rivet rods or the passage of a riveting tool can be made thereafter, by drilling, punching, or by laser cutting, for example. Alternatively, said holes of the support can be made before fixing the friction body on the support. In this case, it is necessary to properly position the support relative to the friction body before fixing.

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 produced by pressure molding in a mold comprising a fixed part comprising a first cavity and a movable piston comprising a second cavity, at least one of said cavities comprising a projecting part able to form the hole 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 to 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 surface of the friction body is machined by grinding, until said hole opens at the second surface 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 several holes, all the holes can lead at one time to the level of the friction face, in a single grinding step.

Finally, after machining the second surface of the body, any particles present in the hole 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, features and advantages of the invention will become apparent 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 shows a friction disk 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 composite material or a sheet of thin metal material, of thickness generally between 0.2 and 1 mm.

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 attachment faces 7 are for example glued on the corresponding foils 5 and each foil 5 is 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 one driving member, such as a crankshaft of a combustion engine, to a driven member, such as an input shaft of a gearbox.

As previously indicated, holes 10 are formed in the friction bodies, and serve to house the heads of the rivets.

Holes 19, 20 are further provided in the foils 5 and serve respectively to pass the rods of the rivets 9, and the passage of a not shown riveting tool, as is known per se. The holes 19 have a smaller diameter than the holes 20.

Thus, the heads of the rivets 9 bear on the foils 5, around the holes 19 serving for the passage of the rods of the rivets 9, said heads being moreover housed in the holes 10 of the friction bodies 6.

For the reasons indicated above, it is sought to achieve in a simple and inexpensive way, friction bodies 6 having holes 10 completely through the friction bodies 6, that is to say not having any friction material downhole 10, on the foils 5.

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 having holes 10 opening only at the attachment face 7 of the body 6.

More particularly, as shown in FIG. 1, the friction body 7 is made by pressure molding in a mold comprising a fixed annular portion 11 comprising a first cavity and a movable annular piston comprising a second cavity comprising cylindrical portions projection 13 able to form the holes 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 to the fixing face 7, is machined by grinding (FIG. 6) until the holes 10 open 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 friction face 8 of the friction body 6 being machined using a cutter 17. The machined material thickness 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 holes are then extracted, for example by suction.

The holes in the support and allowing the passage of the rivet rods or the passage of a riveting tool can be carried out subsequently, by drilling, punching, or by laser cutting for example. Alternatively, said holes of the support may be made before fixing the friction body on the support. In this case, it is necessary to properly position the support relative to the friction body before fixing.

Claims

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

- producing a friction body (6) having at least one hole (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 hole (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 hole (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 friction body (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.

10. 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 hole (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 hole (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.