GB2156014A

GB2156014A - Friction clutch

Info

Publication number: GB2156014A
Application number: GB08507581A
Authority: GB
Inventors: Lother Huber
Original assignee: LuK Lamellen und Kupplungsbau GmbH
Current assignee: LuK Lamellen und Kupplungsbau GmbH
Priority date: 1984-03-22
Filing date: 1985-03-22
Publication date: 1985-10-02
Also published as: FR2561731A1; GB8507581D0; BE902001A; DE3410475A1

Abstract

During the reconditioning of diaphragm spring friction clutches. there is provided, between the counter-pressure plate (12) and a sheet metal pressing having parts (19, 20), at least one intermediate element (44) of thickness (45) which compensates for the material removed during reconditioning from the friction surface of the pressure plate and/or of the counter-pressure plate. Openings in the pressing provide ventilation. <IMAGE>

Description

SPECIFICATION Friction clutch The invention relates to a friction clutch, especially for motor vehicles, having a clutchcarrying disk which can be fixed to the crankshaft of an internal combustion engine, an axially movable pressure plate, a diaphragm spring provided between the latter and the clutch-carrying disk, which diaphragm spring is supported by radially outer parts thereof against the clutch-carrying disk and acts on the pressure plate by means of parts thereof which are located further inwardly, and furthermore having a counter-pressure plate which can be axially and rotationally fixed by spacing means to the clutch-carrying disk and a clutch disk provided between the counterpressure plate and the pressure plate, the spacing means being capable of being fixed to the clutch-carrying disk and engaging with a clamping action over the side of the counterpressure plate remote from the engine.

In such friction clutches, wear on the friction surfaces of the pressure plate and the counter-pressure plate occurs after a certain period of operation. Moreover, it often happens that grooves are formed in the friction surfaces of the pressure plate and the counterpressure plate, or even that, when worn out friction linings on the clutch disk are disregarded, the lining-securing rivets damage the said friction surfaces.In by far the greatest number of cases, the other component parts of the friction clutch are still completely operational, for which reason, a so-called reconditioning is usually carried out after such clutches have been dismantled, the friction surfaces of the pressure plate or of the counter-pressure plate first being re-surfaced by turning on a lathe-usually while they are in a dismantled state-and the component parts of the clutch then being reassembled.

Such reconditioned or repaired friction clutches, however, only in very few cases fulfil the requirements imposed on them in regard to wear-resistance and to the torque to be transmitted, since the diaphragm spring has a relatively small prestress after the reconditioning operation due to the amount of material removed from the pressure plate and/or counter-pressure plate.

The basic object of the present invention is to remove these disadvantages of repaired or reconditioned clutches and to enable reliable functioning and operation to be obtained in a particularly simple and economical manner.

According to the invention, this is achieved in friction clutches of the kind initially referred to in that, in order to compensate for material removed by mechanical after treatment from the friction surfaces of the pressure plate and/or of the counter-pressure plate, at least one intermediate element is provided, during the reconditioning of the friction clutches, between on the one hand those parts which engage with a clamping action over the counter-pressure plate and on the other hand the counter-pressure plate itself.By these features it is ensured that, when the overhauled or reconditioned component parts of the clutch are reassembled, the friction surfaces of the counter-pressure plate which cooperate with the friction linings on the clutch disk are displaced in the direction towards the clutchcarrying disk by a distance at least approximately equal to the thickness of material removed from the friction surfaces of the pressure plate and/or of the counter-pressure plate. Consequently, when the clutch is reassembled, the parts of the pressure plate which are acted on by the diaphragm spring once again assume at least approximately the positions which correspond to those in new clutches, so that the diaphragm spring also has at least approximately the same prestress as in a new clutch.

It may be particularly advantageous if the spacing means of such a friction clutch is constituted by a sheet metal pressing since such parts can be particularly advantageously shaped and economically produced.

According to an embodiment of the invention, the intermediate element may be constituted by a spacing ring which is arranged between the counter-pressure plate and the parts of the spacing means or of the sheet metal pressing which engage radially over the counter-pressure plate. Such a spacing ring is particularly advantageous for the reassembly operation, since only one additional part is necessary for the reconditioning of the friction clutches According to another constructional form of the invention, a plurality of intermediate elements which are distributed circumferentially may be provided between the counter-pressure plate and the spacing means or the sheet metal pressing.In friction clutches, in which the counter-pressure plate and the spacing means or the sheet metal pressing are interconnected, in the region of the parts of the spacing means which engage radially over the counter-pressure plate, by mechanical connecting elements, such as for example rivets or screws, it may be particularly advantageous if the intermediate elements are arranged in the region of fixed connection between the counter-pressure plate and the spacing means or the sheet metal pressing.

According to a further feature of the invention, it may be advantageous if the intermediate element or elements have a thickness of between 0.3 and 2 mm and preferably between 0.5 and 1 mm.

The invention will be explained in greater detail with reference to Figs. 1 to 4, in which: Figure 1 is a section on the line I-I of Fig.

2 of a friction clutch according to the inven tion, Figure 2 is an elevational view, partly cut away and with the clutch disk omitted, from the viewpoint of the arrow II of Fig. 1, Figure 3 is a section through a new friction clutch component taken on the line Ill-Ill of Fig. 2; and Figure 4 is a section corresponding to Fig.

3 of a reconditioned friction clutch component.

The friction clutch 1 consists of a clutchcarrying disk 3 affixed to a crankshaft 2 partly shown, an axially movable pressure plate 4, a diaphragm spring 5 which is provided between the latter and the clutch-carrying disk 3, is supported by radially outer parts 6 thereof against supporting regions 7 of the clutch-carrying disk 3 and, by means of parts 8 thereof which are locared radially further inward, acts on the pressure plate 4 via fulcrum parts 9. The diaphragm spring 5 is assembled in a presetressed condition and urges the friction linings 10 of the clutch disk 11 in the direction towards the counter-pressure plate 12 which is connected by spacing or gap-bridging means 13 to the clutch-carrying disk 3 so as to be axially and rotationally fixed to the latter.The gap-bridging means 1 3 consists of a sheet metal pressing which is of cap-shaped or dished form and is secured via its rim 14 to the clutch-carrying disk 3 by countersunk screws 1 5. These screws 1 5 additionally secure the toothed gear rim 1 6 which is slid or forced over the at least approximately cylindrical and axially extending part 1 7 of the metal pressing 1 3. Adjacent the axially extending part 1 7 there is a part 18, which is also cylindrical and also extends axially, the outer surface or outer diameter of which is, however, somewhat smaller than that of the part 1 7. Adjoining the axially extending part 1 8 are tongue-like parts 1 9 which engage behind the counter-pressure plate 1 2 by means of their radially inwardly extending sections 20.

The radially inwardly extending sections 20 of the tongue-like parts 1 9 form seating surfaces 21 against which the counter-pressure plate 12 is supported by contact surfaces 22.

The contact surfaces 22 are provided on axial raised parts of or projections 23 on the counter-pressure plate 1 2.

As is apparent from Figs, 1 to 3, the counter-pressure plate 1 2 is supported, after the initial assembly of the friction clutch 1, i.e. in the case of a new friction clutch 1, directly against the seating surfaces 21 of the tongue-like parts 19.

Screw-threaded connections 24 are provided for the transmission of torque between the counter-pressure plate 1 2 and the capshaped or dished gap-bridging spacing means 1 3. Such a screw-threaded connection 24 is obtained with the aid of a hexagon-sockethead screw 25 which extends through the bore 26 in the respective raidally extending section 20 and is screwed into a bore 27 in the counter-pressure plate 1 2. Between the head of a hexagon-socket-head screw 25 and a radially extending part 20 there is provided a lock washer 28 which prevents the screw 25 from becoming spontaneously unscrewed.

Such screw-threaded connections 24 ensure both a reliable rotationally fixed connection and also an axially fixed connection between the cap-shaped component 1 3 and the counter-pressure plate 1 2.

The pressure plate 4 is provided with projections 29 which are provided at least substantially within the radial extent of the friction linings 10 and extend through openings 30 in the clutch-carrying disk 3. An end surface 31 of the projections 29 serves as a fixing location for the leaf springs 32 which are located outside the clutch space which is delimited on the one hand by the clutchcarrying disk 3 and on the other hand by the counter-pressure plate 12, on that side of the clutch which is nearer to the crankshaft 2.

The other fixing location 33 for the leaf springs 32 is provided on the clutch-carrying disk 3 and is also on that outer side of the clutch which is nearer to the crankshaft 2.

The riveting of the leaf springs 32 to the pressure plate 4 is obtained by blind rivet connections 34. Such a blind rivet connection 34 is produced with the aid of a rivet element 35 which is composed of a hollow body 35a and an expansion-producing element 35b which projects into the stepped bore 36. For this purpose, the rivet element 35 is inserted into a bore in the respective leaf spring 32 and into a blind bore 37 which is provided with radial undercuts and is formed in an axial projection 29 on the pressure plate 4. By driving in the expansion-producing element 35b which is provided with a wedge-shaped or tapered region 35c, the hollow body 35a of the rivet element 35 is expanded radially, so that a displacement of the material thereof is produced which ensures anchorage of the rivet element 35 in the blind bore 37 in the pressure plate 4. The rivet head 38 is formed after the driving in of the expansion-producing element 35b or in the final phase of the driving in of the said element 35b.

The engagement and disengagement of the friction clutch is effected by means of a central thrust rod 39 which actuates a pressure plate 40 and thereby the diaphragm spring 5.

In order to ensure efficient ventilation and cooling of the friction clutch 1, openings 41 are provided in the region of the wall part 1 7 or 1 8 which extends at least approximately cylindrically, these openings 41 being located axially level with the friction linings 10 and circumferentially level with the tongue-like parts 19.

As a result of the relative rotation which occurs between the clutch disk 11 and other parts of the friction clutch 1 when the latter is operated, wear is produced after a given length of time on the friction linings 10 and on the friction surfaces 4a of the pressure plate 4 and on those 1 2a of the counterpressure plate 1 2. Moreover, it often happens that grooves are formed in the friction surfaces 4a and 1 2a or that, when the friction linings are worn out, the rivets by which the friction linings are secured to the clutch disk damage the friction surfaces 4a or 1 2a of the pressure or counter-pressure plates.In order to enable such clutches to be re-used, it is then necessary to machine the friction surfaces 4a, 1 2a of the pressure plate 4 and the counter-pressure plate 12, e.g. by removing a given amount 42, 43 from it by turning. Such removal of material from the friction surfaces 4a and 1 2a has the result that, when the friction clutch 1 according to Figs. 1 to 3 is reassembled, the diaphragm spring will not reassume its predetermined position, even if new friction linings 10 are used. In the examples shown, when the friction clutch is reassembled, the diaphragm spring 5 will be under reduced axial stress because of the thicknesses of material 42,43 removed from the friction surfaces 4a, 12a.As a reslt of this, the reserve of unworn material of the friction clutch is reduced, i.e. if the friction linings 10 are not completely worn out, the contact pressure exerted on the pressure plate 4 by the diaphragm spring 5 would be insufficient to prevent slipping of the clutch disk 10.

In order to ensure reliable operation of reconditioned friction clutches, according to the invention and as shown in Fig. 4 intermediate elements in the form of spacing disks 44 are provided, during the reassembly of the friction clutch 1, between the contact surfaces 22 of the counter-pressure plate 1 2 and those sections 20 of the tongue-like parts 1 9 of the sheet metal pressing which engage radially behind the said counter-pressure plate 12.

The thickness 45 of the spacing disks 44 is so determined that it corresponds at least approximately to the sum of the thicknesses 42, 43 of material removed from the pressure plate 4 and from the counter-pressure plate 12. Thus, when the overhauled or reconditioned component parts of the clutch are reassembled, those friction surfaces of the reconditioned counter-pressure plate 1 2 which cooperate with the friction linings 10 of the clutch disk are axially displaced in the direction towards the clutch-carrying disk 3 by an amount at least approximately equal to the thicknesses 42, 43 of material removed from the friction surfaces 4a, 1 2a of the pressure and counter-pressure plates 4, 12.Thus, on reassembly, the fulcrum parts 9 on the pessure plate 4 which are acted on by the diaphragm spring 5 reassume in relation to the clutch-carrying disk 3 the position which corresponds at least approximately to that in new clutches. Consequently, the diaphragm spring 5, which is supported by its radially outer part 6 against the clutch-carrying disk 3, also has a prestress which is at least approximately equal to that in the clutch when new.

Thus, reliable transmission of torque to the clutch disk over the whole range of wear, as well as satisfactory disengagement and reliable operation of the reconditioned clutch are obtained.

For the transmission of torque between the counter-pressure plate 1 2 and the sheet metal pressing 13, screw connections 46 are again provided in the reconditioned friction clutch, which screw connections 46 are formed by screws 25, in the same way as the screw connections 24.

The invention is obviously not limited to the embodiment shown. Thus, for example, rivet connections or other connections which are known per se could be provided, instead of screw connections 24 or 46, between the sheet metal pressing 1 3 and the counterpressure plate 1 2.

Furthermore, it is possible to form the sheet metal pressing 1 3 in such a manner that, instead of radially inwardly projecting tonguelike parts 19, a closed circular annular part 47 is provided for supporting the counter-pressure plate 12, as shown in chain-dotted lines in Figs. 2 and 3. Also, the spacing disks 44 could be replaced by a single annular spacing ring 48 as shown in chain-dotted lines in Fig.

4. By using a single intermediate element 48, the assembly of the friction clutch 1 is substantially simplified.

The spacing disks 44 of the spacing ring 48 are formed with with bores 49 for the reception of the screws 46.

The thickness 45 of the spacing disks 44 or of the spacing ring 48 may amount to between 0.3 and 2 mm, depending on the size of the friction clutch, but for by far the greatest number of applications a thickness of between 0.5 and 1 mm. should be sufficient.

Claims

1. Friction clutch, especially for motor vehicles, having a clutch-carrying disk which can be fixed to the crankshaft of an internal combustion engine, an axially movable pressure plate, a diaphragm spring provided between the latter and the clutch-carrying disk, which diaphragm spring is supported by radially outer parts thereof against the clutchcarrying disk and acts on the pressure plate by parts thereof which are located radially further inwardly and furthermore having a counter-pressure plate which can be axially and rotationally fixed by spacing means to the clutch-carrying disk and a clutch disk provided between the counter-pressure plate and the pressure plate, the spacing means being capable of being fixed to the clutch-carrying disk and engaging with a clamping action over the side of the counter-pressure plate remote from the engine, characterised in that, in order to compensate for material (42, 43) removed by mechanical after treatment from the friction surfaces (4a, 12a) of the pressure plate (4) and/or the counter-pressure plate (12), at least one intermediate element (44) is provided, during the reconditioning of the friction clutch (1), between on the one hand the parts (19, 47) which engage with a clamping action over the counter-pressure plate (12) and on the other head the said counter-pressure plate (12).

2. Friction clutch according to claim 1, characterised in that the spacing means is a sheet metal pressing (13).

3. Friction clutch according to claim 1 or 2, characterised in that the intermediate element is costituted by a spacing ring (48) which is arranged between the counter-pressure plate (12) and the or each part (19, 47) of the spacing means (13) that engages radially over the counter-pressure plate.

4. Friction clutch according to one of claims 1 to 3, characterised in that a plurality of intermediate elements (44), which are distributed circumferentially, are provided between the counter-pressure plate (12) and the spacing means (13).

5. Friction clutch according to one of claims 1 to 4, characterised in that the intermediate element or elements (44, 48) has or have a thickness of between 0.3 and 2 mm, and advantgeously between 0.5 and 1 mm.