GB2376050A

GB2376050A - A pre-assembled module of a friction clutch with an assembly aid and transportation restraint.

Info

Publication number: GB2376050A
Application number: GB0220566A
Authority: GB
Inventors: Roland Mueller; Marco Greubel; Erwin Ziegler; Winfried Stuermer; Frank Hirschmann
Original assignee: ZF Sachs AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1998-06-05
Filing date: 1999-06-03
Publication date: 2002-12-04
Anticipated expiration: 2019-06-03
Also published as: GB2376050B; GB0220566D0

Abstract

A pre-assembled module for a friction clutch, in particular a motor vehicle friction clutch takes the form of a casing (3) containing a diaphragm spring (2) and a pressure plate (1). As is known, the pressure plate (1) is urged with the diaphragm spring (2) to compress friction linings (6) of a clutch disc (8) interposed between the pressure plate (1) and a flywheel (7) in the fully assembled clutch. The pressure plate (1) is connected axially movably relative to the clutch casing (3) but non-rotatably to the clutch casing (3) via leaf springs (9). To prevent axial movement of the pressure plate (1) in the direction of the open side of the clutch casing (3) during transportation, a releasable transportation restraint is provided. This restraint takes the form of a bowed leaf spring element (12) with one end fixed to the pressure plate (1). The free end of the element (12) has a thickened region (13) which fits between the pressure plate (1) and the casing (3).

Description

A pre-assembled module of a friction clutch with an assembly aid and transportation restraint The invention relates to d pie-a & sernbled module for use in the assembly of a friction clutch, in particular a motor vehicle friction clutch. In such a module a pressure plate and a pressing spring are preassembled in a clutch casing. The pressure plate is connected axially movably relative to the clutch casing and non-rotatably to the clutch casing via leaf springs. To prevent axial movement of the pressure plate in the direction of the open side of the clutch casing during transportation, a releasable restraint is inserted between a catch member and the clutch casing. The catch member limits the axial displacement travel of the pressure plate, and is connected to the pressure plate and guided axially through the clutch casing.

A preassembled module of this type has been made and sold by the Applicant for a long time and is described in more detail in the following description with reference to Figures 1 to 3 of the accompanying drawings.

The preassembled module is supplied, for example, to the vehicle assembly line and is connected there, for example, to the flywheel of an internal-combustion engine after interposition of the clutch disc. The pressure plate connected to the clutch casing only via the tangential leaf springs has a considerable weight. The tangential leaf springs serve not only to connect the pressure plate non-rotatably to the clutch casing but also to lift the fitted pressure plate from the friction linings on declutching when it is released by the diaphragm spring. The tangential leaf springs are not intended to hold the pressure

plate in its position during transportation especially if it is subjected to pronounced axial vibrations. If the construction unit or module is mounted vertically prior To assembly (for example when replacing c clutch) and accidentally falls over, there is also the risk that the pressure plate will spring out in the direction of the open end of the clutch casing. During the above-mentioned axial movements there is a rlsk mat the tangential leaf springs will be overstretched and will no longer be completely operative during operation of the clutch. A transportation restraint which prevents unintentional deflection of the pressure plate is provided for this reason.

This known restraint also acts as an assembly aid when the module is screwed to the flywheel. As the diaphragm spring loads the pressure plate in the direction of the flywheel and is deflected by the complete axial travel, the pressure plate has to be pressed back against the diaphragm spring when the connecting screws are tightened. Owing to the high force of the diaphragm spring, the connecting screws can invariably be screwed into the flywheel only by a few angular degrees and it is difficult to prevent distortion of the component during assembly or excessive loading of the thread.

As the restraint limits the axial travel of the pressure plate, it does not contact the flywheel at the beginning of assembly and, as no force of the diaphragm spring has to be overcome at this moment, screwing of the module to the flywheel is simplified. With the known module, a U-shaped hoop is inserted externally as the restraint and assembly aid between the clutch casing and the catch member limiting the maximum possible axial travel (lining wear) of the pressure plate. This hoop is clamped by the force of the diaphragm spring. The thickness of the hoop

is slightly smaller than the maximum permitted axial travel of the pressure plate. If the clutch casing is screwed to the flywheel, the pressure plate has to be pressed into the clutch casing against the force of the diaphragm spring toward the end of the screw length. The catch member therefore lifts from the hoop and the hoop falls down or is removed radially outward by hand.

A drawback of this simple restraint is that tolerances in the thickness of the hoop can mean that the hoop does not automatically fall out after connection of the module to the flywheel because some residual frictional forces still prevail between the catch member and the clutch casing. Deformation of the hoop can also cause it to"stick"to the clutch casing after assembly even though the catch member has lifted. If this is not detected by the fitter, the hoop is spun out by the centrifugal forces during first commissioning of the clutch and can damage or even destroy surrounding components such as, for example, the gear bell or the like. There is also a risk that the hoop will not fall out completely but will get caught somewhere in the region of the clutch. The fitter who is visually inspecting release of the restraint does not detect this and in these circumstances too, the hoop can be spun outwards owing to the centrifugal force and can cause damage later on during first operation.

Transportation restraints and assembly aids which are provided inside the clutch casing are known from EP 0 207 597 Al. For this purpose, a wire spring is riveted to the casing and its free end engages in a peripheral groove provided in the pressure plate. In the relaxed state, the wire spring contacts the clutch casing radially. To enable the restraint to come into effect,

the wire spring has to be pressed radially inward by a tool via an orifice provided in the casing, until it snaps into the pressure plate. On completion of connection of the preassembiect friction clutch to- me flywheel, me pressure plate is displaced axially toward the diaphragm spring and the wire spring disengages from the pressure plate and snaps back on to the interior of the clutch casing. A drawback of this design is that the pressure plate has to be additionally machined to provide the peripheral groove in order to have a defined contact face for the wire spring. This additional machining is time-consuming and expensive. Furthermore, it is impossible or difficult to check the state of the wire spring and it is possible that for damage to occur if the state of the wire spring is not detected promptly. If the wire spring breaks, there is the abovedescribed risk of overstretching of the tangential leaf springs or damage to the pressing face of the pressure plate.

Further transportation restraints are known from the same document. For example, a sprung hoop can be provided on the rivet which fastens the tangential leaf spring on the pressure plate, springs back in the radially inner direction in the relaxed state and projects axially through the clutch casing. To secure the pressure plate, the sprung hoop is pressed radially outward and then places itself on the clutch casing with its hooked end. The axial movement of the pressure plate in the direction of the open side of the clutch casing is therefore limited. If the pressure plate is loaded into the other axial direction during assembly, the bent end of the sprung hoop disengages from the clutch casing and springs away radially inwardly so the restraint is free. A drawback of this design is that the sprung hoop can bend open if excessively high axial

forces occur during transportation so the restraint becomes ineffective.

An object of the invention is to provide an improved module and transportation restraint.

According to the invention there is provided a pre-assembled module for use in the assembly of a friction clutch, said module comprising a pressure plate and a pressing spring in a clutch casing and leaf springs connecting the pressure plate to the clutch casing for axial movement but non-rotatable movement relative to the clutch casing the pressure plate being subjected to axial force by the spring towards an open side of the casing and a releasable transportation restraint for preventing axial movement of the pressure plate in the direction of the open side of the clutch casing, the restraint acting between an abutment region which limits the axial displacement travel of the pressure plate or is formed by it and a corresponding counterabutment region on the clutch casing, wherein the transportation restraint is held against the abutment and counter-abutment regions by frictional force or an interlocking fit and is adapted to be disengaged by spring force during assembly of the clutch or during first actuation of the clutch and the transportation restraint is formed by at least one generally Ushaped or looped spring element which is fastened on the pressure plate and has, at its free end, a thickened region adapted to be releasably engaged between the pressure plate and the clutch casing on application of a force.

The spring element is adapted to be disengaged by inherent spring force during assembly of the clutch or during first actuation of the clutch.

The spring element is bowed and this design ensures that only compressive forces act on the restraint during operation. Damage is therefore prevented-If the counter-abutment region lifts from the locking element during assembly of the module on the flywheel, the spring relaxes and pulls the element out of the range of action.

If the spring element is non-releasably connected to the pressure plate, this ensures that it cannot be spun away owing to the centrifugal forces acting on it after the restraint has been released. Damage to surrounding components is therefore effectively avoided.

The thickened region of the spring element can be produced by bending over the free end. However, it can also be formed by a platelet or small block connected to the free end of the spring element. Such a piece-part can be welded, for example, to the spring element.

For forming the thickened region, the spring element can also have a U-shaped configuration at its free end, the two arms then being wound inwardly. The arms are preferably angled upwardly through 90".

The thickness of the thickened region preferably corresponds approximately to the maximum wear travel of the friction clutch. This effectively rules out axial movements of the pressure plate during transportation, while ensuring that the restraint can release itself automatically.

It is particularly advantageous if a plurality of spring elements are distributed uniformly round the periphery of the the pressure plate and which can preferably act as a separate restraint on each catch member.

If the spring element fastened on the pressure plate runs out in an arc in the direction of the clutch casing at its fixed end, a rolled radius can be formed at the rear end which is adapted to make perpendicular contact with the deflected tangential leaf spring. This prevents contortion or kinking of the tangential leaf spring.

To simplify assembly of the spring element or elements, a twist preventer is preferably provided at the fixed end with which the element can surround the tangential leaf spring.

The or each spring element can have a tab at its free end and the pressure plate then has a cam which engages behind the tab. This ensures that the element is secured in the radial direction even if the restraint is released. The element is thus prevented from bending open owing to the centrifugal forces when the pressure plate revolves.

The tab is preferably provided, in particular, on the thickened region and projects back in the direction of the fixed end of the element.

The invention may be understood more readily, and various other aspects and features of the invention may become apparent, from consideration of the following description.

Embodiments of the invention will now be described in more detail hereinafter, by way of examples only, and with reference to the accompanying drawings, in which: Figure 1 is an axial end view of part of a pre-assembled module of known design ; Figure 2 is a view of part of Figure 1 anct raken in i : he direction of arrow IV in Figure 1; Figure 3 is a sectional view taken along the line V-V in Figure 1; Figure 4 is a plan view of part of a pre-assembled module constructed in accordance with the invention with the transportation restraint in position ; Figure 5 is a view corresponding to Figure 4 with the transportation restraint released; Figure 6 is a plan view of part of a further pre-assembled module constructed in accordance with the invention with the transportation restraint in position; Figure 7 is a view corresponding to Figure 6 with the transportation restraint released; Figure 8 is a side elevation of a spring element usable in a module constructed in accordance with the invention ; Figure 9 is a section taken along the line XI-XI of Figure 8 ;

Figure 10 is a section taken along the line XII-XII of Figure 11; Figure 11 is a view of the spring element taken in the direction of arrow XIII in Figure 8; Figure 12 is a section taken along the line XIV-XIV of Figure 8; Figure 13 is a section taken along the line XV-XV of Figure 11; Figure 14 is an axial end view of part of a further embodiment of a module constructed in accordance with the invention; Figure 15 is a plan view of part of the module shown in Figure 14, the view being taken in the direction of the arrow XVII in Figure 14 ; Figure 16 is a view corresponding to Figure 14 but without the spring element; Figure 17 is a side elevation of a further embodiment of a spring element usable in a module constructed in accordance with the invention; Figure 18 depicts part of the spring element as viewed in the direction of the arrow XX in Figure 17; Figure 19 is a section along line XXI-XXI of Figure 17; Figure 20 is a section'along line XXII-XXII of Figure 23 : Figure 21 is a section along line XXIII-XXIII of Figure 23;

Figure 22 is a section along line XXIV-XXIV of Figure 17 and Figure 2j is a view in the direction oi the arrow XXV uf Flgule

17.

Figures 1 to 3 show a known pre-assembled module tor a conventional friction clutch. The preassembled module is composed of a clutch casing 3, a pressure plate 1 and a diaphragm spring 2 which is arranged between pressure plate 1 and the clutch casing 3. During operation of the assembled clutch, the spring 2 urges the pressure plate 1 towards friction linings 6 of a clutch disc 8 and a flywheel 7 of an internalcombustion engine not shown in detail here (cf. Figure 3). The axial displacement travel V of the pressure plate is limited by a catch sleeve 4 which is connected via a rivet 5 to the pressure plate 1 and is guided axially out of an aperture 15 provided in the casing 3. The outer end of the catch sleeve 4 has a radial flange which forms a rim having a greater diameter than the aperture IS so the flange acts as an abutment on the clutch casing 3. The extent of the travel V depends on the permitted wear of the friction linings 6. The pressure plate 1 is non-rotatably connected to the clutch casing 3 via tangential leaf springs 9 each connected at one end via a rivet 10 to the clutch casing 3 and at its other end via a rivet 11 to the pressure plate 1 and the catch sleeve 4. To prevent axial movement of the pressure plate 1 during transportation of the preassembled module, a locking component in the form of a small block or a U-shaped hoop which is somewhat flatter than the maximum permitted wear travel V is inserted between the flange of the sleeve 4 and the exterior of the clutch casing 3. This locking component blocks the path of the pressure plate 1 to the

open side of the clutch casing 3. If the clutch casing 3 is connected to the flywheel 7 by screws (not shown in detail) during assembly, the pressure plate 1 is pressed against the force of the diaphragm spring 2 in the direction of the closed side of the clutch casing 3 into its basic position and the maximum travel V is adjusted as free space between the flange of the catch sleeve 4 and the clutch casing 3. The somewhat flatter locking component between the sleeve 4 and the clutch casing 3 then falls out.

A modified transportation restraint constructed in accordance with the invention can be seen in Figures 4 and 5. The locking component of this restraint now takes the form of a spring element 12 as a leaf spring of looped or bowed configuration which is non-releasably connected to the pressure plate 1 at one end via a rivet 14. This rivet 14 fastens one of the leaf springs 9. At its free end, the element 12 is provided with a thickened region 13 which can be produced by bending back the free end or by a small block or platelet welded to the element 12. The thickened region 13 of the element 12 is inserted between the pressure plate 1 and clutch casing 3. The element 12 can be located both axially externally (in the direction of the gear bell) or axially internally (in the direction of the clutch disc). The width of the thickened region 13 corresponds approximately to the maximum permitted wear travel (V, Figure 2) but is smaller by an amount which ensures that the thickened region 13 can reliably snap between the pressure plate 1 and the clutch casing 3 when the element 12 is relaxed.

For producing the restraint, the element 12 is loaded with a force which can be applied, for example, manually and is placed with the thickened region 13 between the pressure plate 1 and

the clutch casing 3. The diaphragm spring not shown in Figures 4 and 5 then presses the pressure plate 1 toward the open end of the clutch casing 3 so the thickened region 13} s clamped between the pressure plate 1 ano he church casing 3. If me maximum displacement travel (V) is adjusted when the casing 3 is screwed to the flywheel 7, in other words the pressure plate 1 is brought into its"neutral position", the thickened region 13 automatically snaps out and the restraint and assembly aid is released (Figure S). The spring element I ? is however reliably retained by the rivet 14.

Figures 6 and-) depict another construction similar to that shown in Figures 4 and 5 where like reference numerals denote like parts.

Figures 8 to 13 show a particular constructional form of the spring element 12 more clearly. The fixed end is provided with a central hole or orifice 17 by means of which the element 12 is fastened. At the side, this rear fixed broader end is provided with a twist preventer 12b which clasps around the tangential leaf spring 9. At the outer fixed end, the element 12 is provided with a rolled edge 12a. For this purpose, the extreme tip of the element 12 is given a radius around which the leaf spring 9 can bend in its deflected position so that no materialdamaging kink is produced which would be the case if the end of the element 12 had a sharp edge. To prevent the thickened region from kinking out laterally, it is possible to punch out a U 16 at the front end of the element 12 and to wind the free arms 13', 13"which have previously been angled upwardly by 90 inwardly (cf. Figures 9, 12). Winding is carried out by bending and rolling transversely to the load direction. Two rectangular profiles which are suitably strong are formed in this way.

Figures 14 to 23 show a further embodiment of the invention. Here the spring element 120 is provided, at its free end, with a tab 18 which emerges from the thickened region 130 and projects in the direction of the end to be fixed (Figure 17). The element 120 is connected to the pressure plate 1 via the rivet 14. For restraint in transport, the thickened region 130 is placed between the pressure plate 1 and the casing 3 as shown in Figure 15. The tab 18 engages behind a cam 19 provided on the pressure plate 1 and secures the element 120 radially. Escape of the element 120 owing to the centrifugal forces acting on it during operation of the clutch is therefore avoided.

Figure 16 is a view similar to Figure 14 but to illustrate the design of the cam 19 on the pressure plate 1 the element 120 has been omitted.

List of reference numerals 1 pressure plate 2 diaphragm spring/presslng sprlnq 3 casing/clutch casing 4 catch member/catch sleeve 5 rivet 6 friction lininqs 7 centrifugal mass/flywheel 8 friction disc 9 tangential leaf spring/leaf spring 10 rivet 11 rivet 12 spring element 120 spring element 12a rolled edge 12b abutment/twlst preventer 13 thickened region/platelet 130 thickened region 13'arm

13"arm 13 Ty a= 14 rivet 15 aperture 16 punching 17 hole 18 tab 19 cam V travel/wear travel

Claims

Claims 1. A pre-assembled module for use in the assembly of a friction clutch, said module comprising a pressure plare (1) and a pressing spring (2) in a clutch casing (3) and leaf springs (9) connecting the pressure plate (1) to the clutch casing for axial movement but non-rotatable movement relative to the clutch casing (3) the pressure plate (1) being subjected to axial force by the spring (2) towards an open side of the casing and a releasable transportation restraint for preventing axial movement of the pressure plate (1) in the direction of the open side of the clutch casing (3), the restraint acting between an abutment region which limits the axial displacement travel of the pressure plate (1) or is formed by it and a corresponding counter-abutment region on the clutch casing (3), wherein the transportation restraint is held against the abutment and counter-abutment regions by frictional force or an interlocking fit and is adapted to be disengaged by spring force during assembly of the clutch or during first actuation of the clutch and the transportation restraint is formed by at least one generally U-shaped or looped spring element (12,120) which is fastened on the pressure plate (1) and has, at its free end, a thickened region (13,130) adapted to be releasably engaged between the pressure plate (1) and the clutch casing (3) on application of a force.
2. A module according to claim 1, wherein the thickened region (13,130) is produced by bending the free end of the spring element (12,120).

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3. A module according to claim 1, wherein the thickened region (13) is formed by a block or platelet connected to the free end of the spring element (12).
4. A module according to claim 1, 2 or 3, wherein the spring element (120) has a Lab (18) at the free ena and the pressure plate (1) has a cam (19) which engages behind the tab (180.
5. A module according to claim 4, wherein the tab (18) is provided on the tnickened region 30).
6. A module according to claim 4 or 5, wherein the tab (18) projects in the direction of the fixed end of the spring element (20).
7. A module according to any one or more of claims 1 to 6, wherein the spring element (J2, 120) is non-releasably connected to the pressure plate (1).
8.. A module according to claim 7, wherein the spring element (12, 120) is riveted at its fixed end to the pressure plate (1).
9. A module according to any one or more of the preceding claims, wherein the thickness of the thickened region (13, 130) corresponds approximately to the maximum wearing travel of the friction clutch.
10. A module according to any one or more of the preceding claims, wherein the transportation restraint is composed of a plurality of the spring elements (12, 120) distributed uniformly round the periphery of the pressure plate (1).

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11. A module according to any one or more of the preceding claims, wherein the or each spring element (12,120) at its fixed end runs out in an arc in the direction of the clutch casing (3) o form a rolled radius (12a).
12. A module according to claim 11, wherein the rolled radius (12a) is so designed that the rear end of the element (12,120) can make contact perpendicularly to deflect one of the leaf springs (9).
13. A module according to any one or more of the preceding claims, wherein the thickened region (13,130), of the spring element (12,120) has a U-shaped configuration at its free end and the two arms (13', 13") of the U are wound inwardly.
14. A module according to claim 13, wherein the arms (13', 13") are angled upwardly through 900.
15. A module according to any one or more of the preceding claims, wherein the spring element (12,120) is provided with a twist preventer (12b).
16. A pre-assemble module substantially as described herein with reference to, and as illustrated in any one or more of Figures 4 to 23 of the accompanying drawings.