GB2292783A

GB2292783A - Torsional vibration damper

Info

Publication number: GB2292783A
Application number: GB9517583A
Authority: GB
Inventors: Helmuth Weissenberger
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Sachs AG
Priority date: 1994-08-26
Filing date: 1995-08-29
Publication date: 1996-03-06
Anticipated expiration: 2015-08-29
Also published as: DE4430261C1; ES2127058B1; GB9517583D0; FR2723998A1; GB2292783B; BR9503029A; FR2723998B1; ES2127058A1

Description

2292783 1 TORSIONAL VIBRATION DAMPER The invention relates to a torsional

vibration damper and in particular a torsional vibration damper with a main damper and a preliminary damper for a clutch plate of a motor vehicle friction clutch.

GB 1 212 161 shows a clutch plate of which the torsional vibration damper comprises a main damper arrangement and a co-axial preliminary damper arrangement axially to one side of the main damper arrangement.

The main damper arrangement is a load damper, and has two disc arrangements rotatable relative to one another about the axis. The first disc arrangement comprises two side discs arranged axially spaced apart and connected together to form a unit by means of a number of circumferentially distributed rivets. The second disc arrangement comprises a central disc arranged axially between the side discs, and provided with friction linings. It is coupled to the side discs in an angularly resilient manner through first spring elements. The side discs in their turn are held by rivets on a flanged ring which is coupled through splines to a hub to rotate with it but with angular clearance. The hub is mounted on an input shaft of a gearbox of the vehicle.

The preliminary damper arrangement comprises two side discs rigidly connected together, between which there is arranged a hub disc which is rotatable relative to the side discs and is seated on the hub to rotate with it. The hub disc is connected in an angularly resilient manner to the two side discs through second spring elements dimensioned to suit idling operation. For coupling the side discs of the preliminary damper arrangement to the side discs of the main damper arrangement a retaining disc is provided axially to one side of the main damper arrangement, the retaining disc being riveted to the flanged ring of the main damper arrangement by means of the rivets. Tongues on the retaining disc connect the side discs of the preliminary damper arrangement to the main damper arrangement to rotate with it.

2 The torsional vibration damper of GB 1 212 161 requires a comparatively high outlay on assembly. Moreover, the additional retaining disc increases the clamping lengths of the rivets and restricts the maximum riveting pressure that can be used for closing the rivets, which reduces the overall strength of the riveted connection. Finally the tolerances in the region of connection of the preliminary damper arrangement and main damper arrangement are relatively large, which adversely affects the operation of the torsional vibration damper. The manner of connection of the preliminary damper arrangement to the main damper arrangement takes up a comparatively large axial space.

US 4 471 863 shows a further torsional vibration damper for a clutch plate differing from the damper of the British patent 1 212 161 chiefly in that the friction linings are connected to the two side discs held together by a number of rivets, whilst the central disc, coupled in an angularly resilient manner to the side discs through the first spring elements, is seated on the hub of the clutch plate with some angular clearance. The preliminary damper arrangement has a hub disc formed integrally on the hub and a single side disc which is rigidly connected to the central disc of the main damper arrangement through spacer pins. Such a damper has the same disadvantages as the damper of GB 1 212 161.

DE-A-43 14 856 shows a clutch plate arrangement of a double clutch with two main damper arrangements arranged axially side-by-side and coupled to a common output hub component, with a common preliminary damper arrangement. The preliminary damper arrangement is arranged axially to one side of the two main damper arrangements and has two side discs connected rigidly together to form a unit and coupled through springs in an angularly resilient manner to an intermediate disc secured to the output hub member. The side disc of the preliminary damper arrangement adjacent to the main damper arrangements carries axially projecting pegs engaging in associated holes in the main damper arrangement. Ring elements of a friction device are arranged axially 3 between the side discs. Such a preliminary damper arrangement is made up of a comparatively large number of individual components, which increases manufacturing and assembly costs.

The invention is based on solving the problem of providing a torsional vibration damper with a main damper arrangement and a preliminary damper arrangement which can be assembled with a relatively low cost.

For the solution of this problem the invention takes as its starting point a torsional vibration damper for a clutch plate of a motor vehicle friction clutch of the kind in which the clutch plate comprises an input member rotatable about an axis and an output member rotatable relative to the input member about the axis, and the torsional vibration damper comprises a main damper arrangement coupling the output member in an angularly resilient manner to the input member by two disc arrangements rotatable relative to one another about the axis, a first disc arrangement comprising two axially spaced side discs rigidly connected together to form a unit and a second disc arrangement comprising a central disc arranged axially between the side discs and with a number of first spring elements coupling the disc arrangements in an angularly resilient manner, a preliminary damper arrangement arranged axially adjacent the main damper arrangement and coupling the output member in an angularly resilient manner to the first disc arrangement, with two preliminary damper components rotatable relative to one another about the axis, and at least one second spring element coupling the two preliminary damper components together in an angularly resilient manner, the first preliminary damper component being connected to the first disc arrangement and the second being connected to the output member, and axially inserted mechanical coupling means connecting the first preliminary damper component to the first disc arrangement with at least one axially projecting coupling projection on one of the first preliminary damper component and the first disc arrangement and a coupling recess on the other component, in which the engagement of the coupling projection 4 in the recess has substantially no circumferential clearance. Such a torsional vibration damper is hereinafter referred to as a torsional vibration damper of the kind set forth.

According to a first aspect of the invention, in a torsional vibration damper of the kind set forth the side discs of the first disc arrangement are rigidly connected by circumferentially spaced rivets, which have axially projecting rivet heads at least on the side axially adjacent to the preliminary damper arrangement, to form the coupling projections of the mechanical coupling means and the first preliminary damper component has recesses matching the rivets, and in which the heads of the rivets engage axially.

In such a damper the rivet heads of the rivets connecting the side discs of the main damper arrangement also provide the mechanical coupling of the main damper arrangement to the preliminary damper arrangement. As the rivets only have to clamp the components of the main damper arrangement they can be closed with higher riveting pressure, which improves the stability and accuracy of the riveting.

Furthermore, the axial length of the rivets can be reduced as the rivets have to clamp only components of the main damper arrangement. The direct coupling of the preliminary damper arrangement by means of the rivet heads also reduces the weight of the damper as any further attachment members are not needed. The preliminary damper arrangement can be preassembled separately from the main damper arrangement.

Preferably the side discs are substantially annular, and the rivets are arranged in the region of the inner periphery of the side discs, radially inwardly of the first spring elements. This enables the spring element of the preliminary damper arrangement to be arranged on as small a diameter as possible.

The rivet heads may have a round cross-section, which, because of riveting tolerances, and tolerances on the diameter of the rivet head and the diameter of the recesses can lead to increased contact pressures and thereby to wear. Preferably therefore the rivet heads and the recesses are provided circumferentially with diametrally opposed flattened portions which reduce the bearing pressure between the rivet heads and the recesses.

Conveniently, one of the two preliminary damper components has a respective pocket radially locating each second spring element, the pocket being bounded circumferentially on both sides by a stop for the second spring element, and the other preliminary damper component carries stop projections which project axially towards the one preliminary damper component, each second spring element being embraced by a pair of stop projections.

The first preliminary damper component may be connected axially loosely to the first disc arrangement.

The recesses in the first preliminary damper component can, when it is a plastics moulding, be produced with comparatively small tolerances with regard to the dimensions of the recesses and their spacing from one another. On the other hand conventional riveting processes lead to comparatively large tolerances in the pattern in which the rivet heads are arranged, which must be taken into account in the dimensions of the recesses and would lead to comparatively large clearances in the connecting path of the preliminary damper arrangement. A second aspect of the invention is based on solving the problem of manufacturing a torsional vibration damper of the kind set forth to permit the mechanical coupling of the preliminary damper arrangement to the main damper arrangement with relatively small tolerances.

A second aspect of the invention relates to the manufacture of a torsional vibration damper of the kind forth.

6 According to a second aspect of the invention, in a method of manufacturing a torsional vibration damper of the kind set forth, including a flanged ring projecting radially from the output member between the side discs and being connected through follower means to the output member to rotate with it with some angular play, a plurality of rivets arranged in superimposed holes in the side discs and the flanged ring to connect the side discs, each rivet having a rivet head on each axial side of the unit, the first preliminary damper component having recesses to match the adjacent rivet heads, the rivet heads and recesses comprising the mechanical coupling means, the method comprising the steps of bringing together the side discs, the flanged ring, the central disc and the first spring elements; closing the rivets by forming the rivet heads, the heads adjacent the recesses being formed by means of a one piece tool engaging all these rivet heads simultaneously; and mounting the preliminary damper arrangement by engaging the rivet heads in the recesses.

This ensures that the dimensions of the rivet heads for engagement in the openings and also the spacing of these adjacent rivet heads, is determined by the tool and not by tolerances in the holes provided for them in the components which are to be riveted together. As the tolerances in the tool can be quite close, the close tolerances of the recesses in the first preliminary damper component can achieve comparatively close overall tolerances.

Preferably, closing heads are formed on the ends of the rivets axially remote from the preliminary damper arrangernent and setting heads are formed on the ends of the rivets adjacent to the preliminary damper arrangement by means of the tool deforming them plastically to correspond to the recesses. The plastic deformation of the setting heads cancels out dimensional and location tolerances. The holes provided for the rivets in the components of the main damper arrangement can then be made with comparatively large tolerances. Advantageously the axial 7 lengths of the setting heads are shortened and lateral flattened portions are formed on the setting heads.

A third aspect of the invention aims to simplify the preliminary damper arrangement and to provide that the torsional vibration damper can be assembled comparatively inexpensively.

According to a third aspect of the invention, in a torsional vibration damper of the kind set forth, the second preliminary damper component is arranged on the side of the first preliminary damper component axially remote from the main damper arrangement, one of the two preliminary damper components has for each second spring element a pocket radially locating the second spring element and bounded circumferentially on both sides by a stop for the second spring element, and the other of the two preliminary damper components carries stop projections projecting axially towards the one preliminary damper component, each second spring element being embraced by a pair of stop projections, and the first preliminary damper component is axially loosely connected to the first disc arrangement.

The pockets in the one preliminary damper component ensure accurate location of the second spring elements whilst the other preliminary damper component only has to provide the rotational coupling of the second spring element to the output member.

Preferably the pockets are provided in the first preliminary damper component which abuts axially against the main damper arrangement. The preliminary damper component with the pockets is preferably in the form of a moulding, such as a plastics moulding, which has the advantage that it can be made in one piece and with very close tolerances. This is of particular advantage when the pockets are provided in the first preliminary damper component, which is connected to the main damper arrangement, as then the pockets and the coupling means designed for connection to the main damper arrangement can be manufactured with 8 very close tolerances. This preliminary damper component can also be made as a metal casting. The other of the two preliminary damper components can also be in the form of a plastics moulding or a metal casting, or alternatively can be a sheet metal component, which then 5 reduces the axial space taken up by the preliminary damper arrangement.

In the first aspect of the invention the rivets connecting the side discs also connect the main damper arrangement to the preliminary damper arrangement, but in the third aspect of the invention other coupling means may be provided. Thus, preferably the first preliminary damper component engages axially against one of the side discs of the first disc arrangement, and at least one coupling projection projects axially from the adjacent side disc or the first preliminary damper component, the projection engaging in a coupling recess in the other component. Each coupling projection is preferably formed integrally with the component from which it projects. Each projection may be in the form of a tongue bent down axially from the side disc. In particular where the first preliminary damper component comprises a moulding or casting, the coupling projection comprises a projection formed on the first preliminary damper component. The coupling recesses associated with the projection can then be formed in one working step in the production of the adjacent side disc of the main damper arrangement, which is generally achieved by stamping.

Other components of the main damper arrangement can be utilised for coupling it to the preliminary damper arrangement. Where the first spring elements are arranged in windows in the central disc and the two side discs, and the first preliminary damper component engages axially against one of the side discs at least one connecting element passing through a window in the central disc may be held on the side discs and project axially beyond the side disc adjacent the first preliminary damper component, to form a coupling projection. Such a connecting element can be utilised for stiffening the main damper arrangement; however, advantageously it is a stop element limiting the relative angular movement 9 of the two disc arrangements of the main damper arrangement. Preferably it comprises a stop plate with its flat faces extending substantially circumferentially, to limit relative angular movement of the two disc arrangements.

The spring element of the preliminary damper arrangement is normally arranged on a comparatively small diameter. There is therefore only comparatively little space available in the neighbourhood of the preliminary damper arrangement for mounting a friction device. Space for mounting the friction device radially inwards of the diameter of the positions of the spring elements of the preliminary damper arrangement can be provided if a coupling recess in the first preliminary damper component for receiving the coupling projection formed by the connecting element is provided radially outwards of the mounting diameter of the second spring element. This has the advantage that the coupling connection takes place on a comparatively large diameter, thus reducing the forces to be transmitted. Space for a friction device between the two preliminary damper components is also obtained if a coupling projection is provided on the first preliminary damper component, extending away from the second preliminary damper component.

Further features of the torsional vibration damper may be used in either the first or third aspects of the invention. For stability, a flanged ring projects radially from the output member between the side discs, and is coupled through follower means to the output member, the rivets passing through the side discs and the flanged ring. The follower means preferably couple the first disc arrangement to the output member for rotation with it, but with a predetermined amount of angular play. The angular play restricts the working range of the preliminary damper arrangement so that the preliminary damper arrangement is bridged or bypassed in the working range of the main damper arrangement.

In a preferred embodiment, the main damper arrangement and the second preliminary damper component are each independently located in both axial directions on the output member and the main damper arrangement and the second preliminary damper component locate the first preliminary damper component axially between them. This has the advantage that axial forces exerted on the input member in operation can be taken by the main damper arrangement and passed directly into the output member. Axial displacement forces do not appreciably affect the operation of the preliminary damper arrangement, but at the same time easy assembly is assured. This applies in particular when the first preliminary damper component is connected axially loosely to the rivet heads.

Some embodiments of the aspects of the invention by way of example are illustrated in the accompanying drawings, in which- Figure 1 is a partially cut-away axial partial elevation of a clutch plate for a motor vehicle friction clutch with a torsional vibration damper according to the first aspect of the invention; Figure 2 is an axial longitudinal section through one half of the clutch plate looking along a line II-II in Figure 1; Figure 3 is an axial longitudinal section through one half of the clutch plate looking along a line III-III in Figure 1; Figure 4 is an axial view of a preliminary damper component of the torsional vibration damper of Figure 1; Figure 5 is a section through the preliminary damper component looking along a line V-V in Figure 4; Figure 6 is a diagrammatic illustration of a rivet used for assembling the torsional vibration damper; 11 Figure 7 is a plan view of a tool for use in closing the rivet of Figure 6; and Figures 8 to 10 are partially cut-away axial partial views of modifications of a clutch plate with a torsional vibration damper according to the third aspect of the invention.

The clutch plate illustrated in Figures I to 3 is for a motor vehicle friction clutch. It has a substantially sleeve-shaped hub 3 concentric with an axis of rotation 1 and having on its inner surface a set of splines 5 for connecting to an input shaft, not shown, of a vehicle gearbox. A torsional vibration damper indicated generally at 7 connects a follower disc 11, provided axially on both sides with friction linings 9, concentrically and in an angularly resilient manner to the hub 3. The follower disc 11 with its friction linings 9 forms an input member of the torsional vibration damper 7 whilst the hub 3 serves as the output member.

The torsional vibration damper 7, as can best be seen in Figure 2, comprises a main damper arrangement 13 designed for operation under load, and a preliminary damper arrangement 15 axially adjacent to the main damper 13 and of dimensions suitable for idling operation.

The main damper arrangement 13 will be described first. It has a first disc arrangement of two substantially annular side discs 17 arranged axially spaced apart and rigidly connected together near their inner peripheries to form a unit by means of a number of circumferential ly distributed rivets 19. The rivets 19 pass through the side discs 17 and through a flanged ring 21 which is arranged axially between them and determines the spacing between the side discs 17. As can best be seen in Figure 1, the ring 21 has on its inner periphery a set of internal splines 25 engaging external splines 23 on the hub 3. The splines 23, 25 have a degree of angular clearance determining the working range of the preliminary damper 15 but after this clearance has been taken up they connect the flanged ring 21 and thus the side discs 17 to the hub 3 to 12 rotate with it. A second disc arrangement comprises a central disc 27 mounted rotatably on the flanged ring 21 between the side discs 17. The follower disc 11 is secured to the outer periphery of the disc 27 which is connected in an angularly resilient manner to the side discs 17 through a number of circumferentially distributed helical coil compression springs 29. The springs 29 are seated in superimposed windows 31 in the central disc 27 and windows 33 in the side discs 17. On rotation of the central disc 27 relative to the side discs 17 they are put under load through their ends engaging directly the periphery of the window.

The relative angular movement between the central disc 27 and the side discs 17 is limited by plate-shaped stop elements 35 which pass axially through the windows 31 and have their ends 37 engaging in openings 39 in the two side discs 17. On each circumferential side of the ends 37 the stop elements 35 have shoulders 41 (Figure 1) which locate them axially on both sides of the side discs 17. Elach stop element 35 passes through the window 31 with some play in a circumferential direction in a stop opening 43 (Figure 1) which is formed by cutting away a radially inner part of the periphery 45 of the substantially rectangular window 31. The stop openings 43 form stop shoulders 49 spaced radially from substantially radially extending control edges 47 of the window that co-operate with the ends of the springs 29. The shoulders 49 are engaged by the stop element 35 connected to the side discs 17 to limit relative angular movement. As the stop element 35 has its flat faces extending circumferentially and passes through the window 31 in the central disc 27 radially spaced from the springs 29, the circumferential space available can be utilised in an optimum manner for the mounting of the springs 29.

Since the stop shoulders 49 are arranged spaced away from the corners 51 forming the transition from the periphery 45 to the control edges 47, mechanical stresses which act on the corners 51 are reduced.

The main damper 13 includes a friction device 53 (Figures 2 and 3) which acts in the load range on rotation of the central disc 27 relative to the side discs 17. The friction device 53 has multi-part friction rings 55 13 arranged between the central disc 27 and each side disc 17. The rings 55 are urged against the central disc 27 by an axially acting spring, in this case a plate spring 57. The plate spring 57 is arranged between one of the friction rings 55 and the side disc 17 which is adjacent to the preliminary damper 15, and it urges the friction ring 55 against the central disc 27, which is rotatably and axially movable on the flanged ring 21. The force path of the plate spring 57 is completed through the rivets 19 to the other side disc 17. As can be seen best in Figure 1 the friction rings 55 and the plate spring 57 have a number of peripherally spaced notches 59 through each of which one of the stop elements 35 projects and couples the friction rings 55 as well as the plate spring 57 to the side discs 17 to rotate with them. In this way the ring components are easier to manufacture than conventional components of this kind, which are usually provided with axially bent-over noses or the like to provide the driving connection.

The preliminary damper 15 includes a first or input component 61 coupled to the side discs 17 of the main damper 13 to rotate with them.

The component 61 is coupled to a substantially annular output or second component 65 in an angularly resilient manner through a number of circumferentially distributed helical coil compression spring 63. The output component 65 in its turn is connected to the hub 3 through a splined region 67 to rotate with it. The input component 61 comprises a plastics moulding, and has circumferentially spaced pockets 69 open towards the output component 65 to receive respective coil springs 63.

As best seen in Figure 4, each of the pockets 69 locates the associated spring 63 on both radial sides and has a control stop 71 on each circumferential side of the associated spring 63 and co-operating with its end faces. Circumferentially extending arcuate slots 73 terminate in the region of the control stops 71. The slots 73 are engaged by stop tongues 75 (Figure 3) which project axially from the output component 65. Each spring 63 is embraced by a pair of tongues 75, which also engage the end faces of the springs 63.

14 Each rivet 19 for connecting the two side discs 17 has on its end adjacent the preliminary damper 15 a setting head 77 which projects beyond the side disc 17. As can best be seen in Figure 4 and 5, each head 77 engages in a recess 79 formed in the input component 61 on the axially facing side and in a pattern matching the setting heads 77. The setting heads 77 have circumferentially opposed flattened portions 81 by which they engage in similarly circumferentially opposed flat sides 83 of the recesses 79. The flattened portions 81 in combination with the faces 83 ensure a reduction in wear of the input member 61.

The output component 65 of the preliminary damper 15 is in the form of a sheet metal pressing and, as can best be seen in Figures 2, is located axially by a staked point 85 on an axial shoulder of the splined region 67. Alternatively the output component 65 can be a plastics moulding.

The rivets 19 may have a setting head 77 which is pre-formed including the flattened portions 81. In a preferred embodiment which takes care of particularly small manufacturing tolerances, the rivet blanks have, as indicated diagrammatically in Figure 6, a setting head 77' of which the diameter is less than or equal to the spacing between the flattened portions 81 of the closed rivet and of which the height is greater than the height of the setting head 77 in the closed rivet. On closing of the rivets 19 the setting heads 77' of all the rivets 19 which are to be closed are inserted, with their shanks inserted in the main damper 13 to be assembled, in locating guides 86 in a staking tool 87 shown in Figure 7, whilst a closing head 89 (Figures 3 and 6) is formed on the opposite end of each rivet 19. The locating guides 86 have flat faces 91 of the same shape as the flat sides 83 of the openings 79 in the input component 61 and have the same layout as the recesses 79. The setting heads 77' of the rivet blanks seated in the guides 86 are plastically deformed to correspond to the shape of the guide when the closing head 89 is formed.The staking tool 87 and the moulded input component 61 can be made with a high degree of precision. Thus, corresponding to the precision of the staking tool 87, the setting heads 77 of the rivets 19 designed for axially insertable coupling of the input member 61 to the main damper 13 can be manufactured with a high degree of precision. As it can be connected to the main damper 13 by axial plugging in, the preliminary damper 15 can be pre-assembled, which simplifies the overall assembly. Significantly, there are only components of the main damper 13 between the setting head 77 and the closing head 89 of the rivet 19, which reduces the axial space taken up by the main damper 13 and improves the quality of the riveting of the main damper 13. In particular, as none of the components of the preliminary damper 15 have to be riveted at the same time, a higher riveting pressure can be applied on closing of the rivets 19. Lastly, the openings provided in the side discs 17 and the flanged ring 21 for the passage of the rivets 19 can be made with larger tolerances as the tolerances of the setting heads 77 used for mounting the preliminary damper 15 are determined by the tolerances of the staking tool 87.

The torsional vibration damper operates as follows. Under idling conditions the main damper 13 can be regarded as an angularly stiff unit.

Angular oscillations of amplitude less than the clearance between the splines 23,25 of the hub 3 and the flanged ring 21 are handled by movements of the preliminary damper 15. When the amplitude of angular oscillation on increasing torque exceeds the clearance in the splines 23, 25 the preliminary damper 15 is bridged or bypassed and the main damper 13 moves. The friction device 53 damps the angular vibration on rotation of the central disc 27 relative to the side discs 17. Rotation of the central disc 27 relative to the side discs 17 is in its turn limited by the stop elements 35 which engage the edges 49 of the openings 43. The spacing of the edges 49 in a circumferential direction is arranged so that the springs 29 of the main damper 13 still do not reach a condition of the turns being up against one another, i.e. a "solid" condition, on maximum angular movement of the central disc 27 relative to the side discs 17.

The friction rings 55 of the friction device 53 are coupled to the side discs 17 through the stop elements 35 substantially without any 16 angular clearance so that they come into action over the entire working range of the main damper 13. The notches 59 provided in one or both friction rings 55 for the stop elements 35 could also be enlarged so that the friction rings 55 are coupled to the side discs 17 with a degree of angular clearance, so that the friction device 53 then comes into action after a delay.

Figures 8 to 10 show modified clutch plates according to the third aspect of the invention, in that the coupling of the main damper to the preliminary damper is modified. Corresponding reference numerals, including a suffix, have been applied to corresponding parts. Figures 8 to 10 each show a partial axial longitudinal section corresponding to Figure 2. The side views and sections of these clutch plates correspond substantially to Figures 1 and 3 to 5 apart from the differences explained below. The components 41 to 51, 59 and 71 to 75 are present even though not illustrated in Figures 8 to 10. Connecting rivets corresponding to the rivets 19 are not shown. The rivets could be present even when they are not utilised for connecting the preliminary damper. It will be understood that the side discs of the main damper could also be joined together in a different manner to form a unit.

In the clutch plate shown in Figure 8 the side disc 17a adjacent to the preliminary damper 15a has, radially inwards of the spring mounting diameter 93 passing through the centres of the springs 63a, several circumferentially spaced tongues 95 bent over axially towards the preliminary damper 15a. Each tongue 95 engages loosely axially in a respective opening 97 in the input component 61a of the preliminary damper 15a adjacent the side disc 17a. The openings 97 are restricted in a circumferential direction to the peripheral lengths of the tongues 95, so that the input component 61 is coupled to the tongues 95 circumferentially substantially without clearance. The input component 61 is therefore also coupled to the side discs 17a of the main damper 13a. In Figure 8 the tongues 95 are illustrated as lying in the plane of the spring 63a; it will be 17 understood that the tongues 95 could also be offset circumferentially with respect to the springs 63a.

Figure 9 shows a clutch plate in which the input component 61b of the preliminary damper 15b is coupled to the side discs 17b by means of the stop elements 35b explained in conjunction with Figures 1 to 3. The plateshaped stop elements 35b again have their flat faces extending substantially circumferentially, and have their ends 37b projecting axially towards the preliminary damper 15b beyond the side disc 17b adjacent to the preliminary damper 15b. The ends 37b engage axially in openings 99 which are provided at the outer periphery of the component 61b, radially outside the diameter 93b on which the coil springs 63b are arranged. The openings 99 couple the input component 61b circumferentially substantially without clearance but loosely in an axial direction to the stop 15 elements 35b, which in their turn are connected circumferentially substantially without clearance to the side discs 17b. The input component 61b is seated loosely on the ends 37b of the stop elements 35b but it abuts against the adjacent side disc 17b. As the rotary connection takes place radially outwards of the mounting diameter 93b there is space 20 radially inwards of the mounting diameter 93b for a friction device 101 arranged axially between the input component 61b and the output component 65b of the preliminary damper 15b, the friction device being of dimensions to suit idling operation. The friction device 101 comprises a friction ring 103 and an axially-acting ring spring 105, for example a 25 plate spring which is axially stressed between two opposing engaging faces of the input component 61b and the output component 65b together with the friction ring 103. As the ends 37b of the stop elements 35b engage the outer periphery of the input component 61b the forces acting between these parts are comparatively low.

Figure 10 shows a further modification which also leaves space radially inwards of the mounting diameter 93c for a friction device 101c between the input and output components 61c, 65c of the preliminary damper 15c. The input component 61c comprises a plastics moulding 18 with integrally formed pins 107 projecting axially towards the main damper 13c. The pins 107 engage in holes 109 in the axially adjacent side disc 17c of the main damper 13c to couple the input component 61c circumferentially substantially without clearance to this side disc 17c.

The holes 109 can be formed in the disc 17c, for example by stamping, in a single working step at the same time as other openings and bulges, in particular the windows 33c. As the pins 107 face away from the output component 65c there is space for the friction device 101c radially inwards of the mounting diameter 93c. In the friction device 101c the friction ring 103c engages the output component 65c which is made of sheet metal; however, the version of Figure 9 can also be used, in which the friction ring engages the plastics input component. It will be understood that the arrangement of Figure 10 could also be used in Figure 9.

In all the embodiments the input component of the preliminary damper is formed as a plastics moulding with integral pockets for receiving the coil springs, and the output component is the form of a sheet metal pressing. The input component, for support, lies flat against a flat region of the axially adjacent side plate of the main damper. However, in a modification (not shown), the pockets for the coil springs could be provided in the output component. Further, both the input component and the output component could be made of plastics or alternatively both components could be formed as sheet metal pressings.

Claims

19 CLAIMS

1. A torsional vibration damper of the kind set forth, in which the side discs of the first disc arrangement are rigidly connected by circumferentially spaced rivets which have axially projecting rivet heads at least on that side which is axially adjacent to the preliminary damper arrangement to form the coupling projections of the mechanical coupling means and the first preliminary damper component has recesses matching the rivets, and in which the heads of the rivets engage axially.

2. A torsional vibration damper as claimed in claim 1, in which the side discs are substantially annular and the rivets are arranged in the region of the inner periphery of the side discs radially inwardly of the first spring elements.

3. A torsional vibration damper as claimed in claim 1 or claim 2, in which the rivet heads and the recesses are provided circumferentially with diametrally opposed flattened portions.

4. A torsional vibration damper as claimed in any of claims 1 to 3, in which one of the two preliminary damper components has a respective pocket radially locating each second spring element, the pocket being bounded circumferentially on both sides by a stop for the second spring element, and the other preliminary damper component carries stop projections which project axially towards the one preliminary damper component, each second spring element being embraced by a pair of stop projections.

5. A torsional vibration damper as claimed in any preceding claim, in which the first preliminary damper component is connected axially loosely to the first disc arrangement.

6. A torsional vibration damper of the kind set forth, in which the second preliminary damper component is arranged on the side of the first preliminary damper component axially remote from the main damper arrangement, one of the two preliminary damper components has for each second spring element a pocket radially locating the second spring element and bounded circumferentially on both sides by a stop for the second spring element and the other one of the two preliminary damper components carries stop projections projecting axially towards the one preliminary damper component, each second spring element being embraced by a pair of stop projections, and the first preliminary damper component is axially loosely connected to the first disc arrangement.

6. A torsional vibration damper as claimed in claim 6, in which the pockets are provided in the first preliminary damper component, which abuts axially against the main damper arrangement.

8. A torsional vibration damper a claimed in claim 6 or claim 7, in which the first preliminary damper component engages axially against one of the side discs and at least one coupling projection projects axially from the adjacent side disc or the first preliminary damper component, the projection engaging in a coupling recess in the other. of these components.

9. A torsional vibration damper as claimed in claim 8, in which each coupling projection is formed integrally with the component from which it projects.

10. A torsional vibration damper as claimed in claim 8 or claim 9, in which each coupling projection comprises a tongue bent down axially from the side disc.

11. A torsional vibration damper as claimed in claim 8 or claim 9, in which the first preliminary damper component COMprises a casting or moulding and the coupling projection comprises a projection formed on the first preliminary damper component.

21 12. A torsional vibration damper as claimed in claim 6 or claim 7, in which the first spring elements are arranged in windows in the central disc and the two side discs, the first preliminary damper component engages axially against one of the side discs, and at least one connecting element passes through a window in the central disc and is held on the side discs, and projects axially beyond the side disc adjacent the first preliminary damper component to form a coupling projection.

13. A torsional vibration damper as claimed in claim 12, in which the connecting element comprises a stop plate with its flat faces extending substantially circumferentially to limit the relative angle of rotation of the two disc arrangements.

14. A torsional vibration damper as claimed in claim 12 or claim 13, in which a coupling recess in the first preliminary damper component for receiving the coupling projection formed by the connecting element is provided radially outwards of the mounting diameter of the second spring element.

15. A torsional vibration damper as claimed in any of claims 11 to 14, in which ring elements of a friction device are arranged axially between two spaced-apart opposing faces of the two preliminary damper components radially inwards of the mounting diameter of the second spring element.

16. A torsional vibration damper as claimed in any preceding claim, in which a flanged ring projects radially from the output member between the side discs, and is coupled through follower means to the output member, the rivets passing through the side discs and the flanged ring.

17. A torsional vibration damper as claimed in claim 16, in which the follower means couple the first disc arrangement to the output member for rotation with it but with a predetermined amount of angular play.

22 18. A torsional vibration damper as claimed in any, preceding claim, in which the main damper arrangement and the second preliminary damper component are each independently located in both axial directions on the output member and the main damper arrangement and the second preliminary damper component locate the first preliminary damper component axially between them.

19. A torsional vibration damper as claimed in any preceding claim, in which at least one of the two preliminary damper components comprises a casting or moulding.

20. A method of manufacturing a torsional vibration damper of the kind set forth, and including a flanged ring projecting radially from the output member between the side discs and being connected through follower means to the output member to rotate with it with some angular play, a plurality of rivets arranged in superimposed holes in the side discs and the flanged ring to connect the side discs, each rivet having a rivet head on each axial side of the unit, the first preliminary damper component having recesses to match the adjacent rivet heads, the rivet heads and recesses comprising the mechanical coupling means, the method comprising the steps of bringing together the side discs, the flanged ring, the central disc and the first spring elements; closing the rivets by forming the rivet heads, the heads adjacent the recesses being formed by means of a one piece tool engaging all these rivet heads simultaneously; and mounting the preliminary damper arrangement by engaging the rivet heads in the recesses.

21. A method as claimed in claim 20, in which closing heads are formed on the ends of the rivets axially remote from the preliminary damping arrangement and setting heads are formed on the ends of the rivets adjacent to the preliminary damping arrangement by means of the tool deforming them plastically to correspond to the recesses.

23 22. A method as claimed in claim 20, in which the axial length of the setting heads is shortened and lateral flattened portions are formed on the setting heads.

23. A torsional vibration damper of the kind set forth substantially as described herein with reference to and as illustrated in Figures 1 to 7 of the accompanying drawings.

24. A torsional vibration damper of the kind set forth substantially as described herein with reference to and as illustrated in Figure 8 of the accompanying drawings.

25. A torsional vibration damper of the kind set forth substantially as described herein with reference to and as illustrated in Figure 9 of the accompanying drawings.

26. A torsional vibration damper of the kind set forth substantially as described herein with reference to and as illustrated in Figure 10 of the accompanying drawings.

27. A method of manufacturing a torsional vibration damper of the kind set forth substantially as described herein with reference to and as illustrated in Figures 1 to 7 of the accompanying drawings.