GB2194021A - Vibration damper device - Google Patents

Abstract

A divided-flywheel device for damping torsional vibrations, for example between an engine and a drive-line has two flywheel elements (3,4) capable of relative angular movement against the action of arcuate springs (45) in a toroidal passage containing a viscous damping medium. The passage is defined by two pressed sheet metal parts (31) and (32) bonded together by welding to form one flywheel element (3) with an inner flange member (41) therebetween and fixed to the other flywheel element (4). <IMAGE>

Description

SPECIFICATION Vibration damper device The invention relates to a vibration damper device, more especially a divided flywheel suitable for mounting between an engine and a drive member, having at least two components or fiywheel elements mounted rotatably relative to each other and drivably interconnected by means of springs, of which elements one is connected or is connectable to the engine and the other to the drive member, respectively, said device having a chamber which is at least partly filled with a viscuous medium and which accomodates at least a portion of the springs.

Devices of this kind have already been proposed but that, owing to their construction features, proved to be relatively expensive in terms of fabrication and assembly.

The task underlaying the present invention was one of providing a device of the kind mentioned at the outset, which could be manufactured in a particularly simple and rational manner at moderate cost. Another aim was to achieve a faultless sealing of the chamber filled with the viscuous medium. Furthermore, it was intended to extend the service life of such a device and avoid wear. Yet another object of the invention was to improve the operational and functional characteristics relative to the hitherto known devices of the kind mentioned at the outset.

According to the invention, this is achieved by arranging the chamber in a housing constituted by at least two shells bonded together by welding. By this manner of joining the housing parts, an optimum tightness of the chamber can be achieved to prevent escape of the viscous medium. Such a joining of the housing shells or housing halves is particularly advantageous when the latter consist of pressed sheet metal parts. It can be particularly expeditious when the housing shells, in the region of their external circumference, have zones which are welded to each other.

Such regions may be constituted by the front or abutting surfaces of the shells which face each other and which can be butt-welded to each other.

For bonding together the shells or housing halves, advantageously such welding processes are applicable in which those regions of the housing parts which are to be welded together are heated by a high-amperage, lowvoltage alternating current to the welding temperature and then bonded together by pressing these parts against each other. Welding processes advantageously suitable for this purpose are so-called pressure welding, resistance-welding or impulse-discharge welding.

The welding current can be applied in pulsed or intermitent manner. For the execution of such welds it can be particularly advantageous to have the housing parts to be welded together consisting of low-carbon steel, at least in In the region of the welds.

In order to avoid the occurrence of an inadmissible local overheating in the components during the welding together of the housing parts, or an undesirable joining of some components in contact with these and movable relative thereto, prior to welding, it is expedient to provide an electrical insulation at least between those components which, prior to welding, are in contact with the housing parts and are movable relative thereto, and the shells. The insulation can be advantageously applied, at least in the contact region of the housing parts, with the components accomodated or fitted into the housing, such as flange bodies, helical springs, inserts, spring cups or other movable components. Here, it can be particularly advantageous when at least one of the sheet metal shells is provided with an insulator coating in these contact regions.

It can also prove to be expedient to provide with an insulator coating at least some of those components which, prior to welding, are in contact with at least one of the shells, for example hub flange, springs, spring cups, at least in the regions of contact of the latter components with the shells or housing parts.

A further possibility of avoiding an inadmissible localised overheating or even a localised welding together consists in producing a portion of those components which, during welding, are in contact with a least one of the housing shells, such as spring cups, for example, from an electrically non-conductive material.

The electrical insulation of at least individual parts of the device can be carried out in a simple manner by phosphate treatment. However, coatings of varnish, ceramics and synthetic plastic materials are. also suitable. In some applications, a layer of fatty substance between the corresponding parts. may be sufficient.

In selecting the insulator coatings, care must be taken that these are compatible with the lubricants in the damper or chamber. It can be advantageous when the sheet metal parts, the flange bodies and the washers or spring cups are insulated by phosphate treatment, whilst the helical springs are varnish-coated.

In order to ensure a precise positioning of the two housing shells after the welding process, it can be advantageous to provide between these axial stops which are or become effective during the welding together of the housing shells.

In order to achieve a faultless welding together of the two housing shells, it may be expedient to have the housing shells free of any coating in the region of the welding zones. In a particularly advantageous manner, the housing or sheet-metal shells are first of all fully coated, for example with a phosphate layer and thereafter are rendered conductive in the region of the welding zones and in the region of the current-feed -appliance by removing the insulator layer previously applied to these regions. This partial removal can be carried out in a simple manner by a mechanical operation.

For the construction, the functioning and the manufacture of the device it can be particularly advantageous to provide the housing or sheetmetal shells with circumferentially extending channel-shaped recesses for the springs, and the bearing surfaces in circumferential direction for the springs are constituted by pocketshaped axial stampings which adjoin the endportions of the spring recesses and are formed in the sheet metal shells and, for precise mutual positioning during the welding process, the sheet metal shels are accomodated in the pockets. For precise positional securing of the housing shells during the welding process, these may also have special positioning means, which may, for example, be constituted by countersunk portions.

Moreover, it may prove particularly advantageous with regard to the functioning and service life of the device if the flywheel element connectable to the engine carries the chamber formed by the shells. A particularly simple structure of the device can be achieved when the shells themselves substantially constitute the flywheel-element which, for example, is connectable to the engine.

In order to achieve a faultless sealing of the chamber containing a viscous medium and to ensure a precise positioning and mounting of the two flywheel elements relative to each other, the sheet metal shell facing towards the engine carries, in a radial internal position, an axial shoulder which extends in the direction of the other flywheel element connectable to the drive member, on which shoulder the other flywheel element is accomodated so as to be rotatable over a roller bearing relative to the first flywheel element. Although it may be advantageous in some applications to form this shoulder integral with the engine-side housing shell, it can also be expedient for manufacturing purposes to produce the axial shoulder and the engine-side shell as separate parts initially, which are then subsequently joined.This joining can be effected by welding, riveting, screwing or wedging-over. To effect the axial securing of the roller bearing on the axial shoulder, a plate fastened to the front face of this shoulder can be advantageously used. The fastening of this plate to the shoulder may be effected by riveting, screwing or even by wedging-over.

With regard to the functioning of the device, more especially its damping effectiveness, it can be particularly advantageous to effect that the channel-shaped recesses for the springs, which are formed by the sheet-metal shells, are adapted to the external diameter of the springs and that the channel-shaped recesses, which form discrete annular segments are, with the exception of a small slit, sealed by a flange element which forms support regions for the springs. In order to simplify the assembly of the device, it can also be advantageous to effect that this flange element is rotationally coupled with the other flywheel element, but is not fixedly connected therewith in axial direction,-so that the device can be assembled by pushing together axially the two flywheel elements.In order to achieve a faultless loading of the springs by the flange element, the latter may advantageously have radial extensions, which project into the channel-shaped recesses.

Furthermore, it may also be advantageous to have the sheet-metal shell facing the engine carry a starter ring gear which is welded at least locally to this shell.

The invention will now be explained in more detail with reference to Figs. 1 to 3, where: Figure 1 is a sectional view of a device according to the invention, Figure 2 is a section taken along the line ll-ll of Fig. 1, and Figure 3 shows a detail of a device according to the invention, which can be employed in a form of embodiment accoring to Figs. 1 and 2.

The torque-transmitting device 1 illustrated in Figs. 1 and 2 for compensation of rotary impulses has a flywheel 2, which is divided in two flywheel-elements 3 and 4. The flywheel element 3 is fastened to the crankshaft 5 of a combustion engine, here not shown in detail, by means of assembly screws 6. The flywheel element 4 has a friction clutch coupling 7 fastened thereto. Between the spacer 8 of the friction clutch 7 and the flywheel element 4 there is provided a clutch disk 9, which is carried on the primary shaft 10 of a gearing not shown in detail. The spacer 8 is acted upon in the direction of flywheel element 4 by a plate spring 12 which is pivotably supported on the clutch cover 11. By actuation of the friction clutch 7, the flywheel-element 4 and thereby also the flywheel 2 or the combustion engine can be coupled to or uncoupled from the primary transmission shaft 10. Between the flywheel element 3 and the flywheel element 4 there is provided a damper device 13, which makes possible a relative rotation between the two flywheel elements 3 and 4.

The two flywheel elements 3 and 4 are mounted rotatably relative to each other by means of a bearing 15.

The flywheei element 3 forms a housing, which defines an annular chamber 30, in which the damper device is accomodated.

The flywheel element 3 having the annular chamber 30 consists essentially of two housing parts 31, 32 which are radially bonded to each other externally. The two housing parts 31, 32 are constituted by pressed sheet metal parts, which are bonded to each other on their external circumference by a weld 38.

This weld 38 seals off at the same time the annular chamber 30 in radial outward direction. For the welding together of the two pressed sheet metal parts 31, 32, advantageously a resistance butt-welding or impulse discharge welding is applied, that is, a method of welding in which the two mutually contacting regions to be welded together of the two components are heated to welding temperature by the application to said components of an alternating current of high intensity and low voltage, to be then joined by the application of pressure.

For the execution of such a welding process, the two shell-like sheet-metal 31, 32 have frontal or abutting surfaces 34, 35 which, relative to the intensity of the current applied for welding, have a definite surface area. In the region of these abutting surfaces 34, 35 the housing parts 31, 32 apply axxially against each other and are then welded together.

For precise radial positioning of the two housing parts 31, 32 during welding, housing part 31 has radially outwards a ring-shaped projection 31a, which surrounds a centering face 35a formed on the external periphery of housing part 32. For precise positioning in circumferential direction during welding, the housing parts 31, 32 have axial countersunk lodgings 65, 66. These lodgings 65, 66 can receive pins of the welding device which hold the two housing parts 31, 32 in a precise angular position relative to each other during the welding process.

Since, during the welding together of the two sheet-metal shells 31, 32, a certain axial displacement between these sheet-metal shells occur owing to weld seam formation, it can be advantageous to provide between these sheet-metal shells axial stops which become effective only during the welding process. In Fig. 1, reference 67 designates such a stop, indicated in composite lines and formed on the sheet-metal sheel 32. By using such iimiting stops 67 there is less dependence on the current intensity applied for welding which means, that it will be possible wo work with a current of higher intensity, since the axial position of the two housing parts 31, 32 is defined by the stops 67 and not by the intensity of the current and the axial pressure applied to the two housing parts 31, 32 during welding.

The output element of damper 13 is constituted by a radial flange 41, which is arranged axially between the two housing parts 31, 32.

The flange 41 is connected, with its radial internal regions, through an axial plus connection 42, to the ring-shaped plate element 27 which is fastened by means of rivets 26 to the front face of the axial shoulder 43 pointing in the direction of the engine-side housing part 31, and part of flywheel-element 4.

On its external periphery the Flange 41 has radial extensions 44, which constitute the load-bearing regions for the force accumulators, in the form of helical springs 45 of the damper 13.

The two housing parts 31, 32 form, in radial outward position, a ring-channelshaped or toroidal recess 51, into which the radial extensions 44 of flange 41 engage. The ring-channel shaped recess 51 for the force accumulators 45 is substantially constituted by the circumferentially extending axial indentations or stampings 52, 53 which are formed into the housing parts 31, 32 made of sheet metal and into which the regions of force accumulators 45 which overhang the flange 41 on both sides project axially. Radially inwards, the ringchannel shaped recess 51 sealed off by an annular region 49 of flange 41, apart from a small gap 54 on at least one side of flange 41.

As will be apparent from Fig. 1, the axial indentations 52,53 are so formed cross-sectionally, that their arcuate shape at least approximately adapts to the circumference of the cross-section of force accumulators 45. In consequence, the external regions of indentations 52,53 can form support or guide regions for the force accumulators 45, which can then find radial support in these regions, at least under the effect of centrifugal force.

For reducing wear on the radial bearing regions of the ring-channel shaped recess 51 for springs 45, there is provided in the present case a steel collar 81 of great hardness, which extends over the circumference of the ring-channel shaped recess 51 and surrounds the springs 45. In the form of embodiment here illustrated, the steel collar 81 has cylindrical form, and is lodged in a recess 82 formed by a radial indentation or a radial nest. When the device 1 rotates, the springs 45 come to bear on the steel collar 81 with their turns under the effect of the centrifugal force acting on them.

For the loading of the force accumulators 45, peripheral stops 55, 55a are located in the indentations 52,53 on both sides of extension 44. In the example of embodiment here illustrated, the peripheral stops 55,55a have-as viewed in circumferential direction-the same extension as the radial extensions 44 of flange 41. As will be apparent from Fig. 2, between the extensions 44 and the ends of springs 45 facing them intermediate parts in the form of spring cups 59 are provided, the circumference of which is adapted to the cross-section of the ring-channel like recess 51.

Radially inside the ring-channel shaped recess 51, the the housing parts 31,32 have regions 60,61 pointing towards each other and forming circular ring-shaped surfaces, between which an annular aperture 62 for the flange 41 is provided.

In the example of embodiment here shown, the width of this circular aperture 62 is only slightly greater than that of the regions of flange 41 lodged in it, so that on at least one side of flange 41 a small gap 54 is present.

As can be gathered from Fig. 2, there are provided, as viewed along the circumference of the device, four springs 45, each of which extends at least approximately over 82 degrees of the circumference. The springs thus extend over at least approximately 90% of the circumference of the device 1.

To reduce the stresses in springs 45 when compressed and to facilitate the assembly, the springs 45 are bent prior to assembly at least approximately to the radius at which they are to be mounted.

The ring-shaped chamber 30 is supplied with a viscous medium or a lubricant. The viscous medium is intended to fill at least the ring-channel shaped recesses 51 when the device 1 is in rotation.

As apparent from Fig. 2, the flange 41 has a median recess 71, the contour of which forms radial profiles 72, which are in engagement with counter-profiles 73 provided on the external circumference of the ring-shaped plate element 27 which is connected to flywheel element 4. The counter-profiles 73 are formed by radial projections which engage into correspondingly adapted indentations 72a of the flange 41. In the region of the radial projections 73, rivets 26 are also provided, which fasten the component 27 to flywheei-element 4. The profiles 72 and counter-profiles 73 forming the axial plug-connection 42 enable a faultless alignment of the flange 41 between the two housing parts 31, 32, so that the play 54 present between the circular ringshaped aperture 62 and the flange 41 can be kept very small.

The plug-connection 42 also make it possible to expand the axial tolerances between the various bearing- and abutting surfaces of the components.

For sealing the ring-shaped chamber 30 there is provided a seal 74 between the radially internal region of housing part 32 and the flywheel element 4; The seal 74 comprises a circular ring shaped, axially resilient gasket 75, which is coated with a syhthetic plastic material and is axially tensioned in radial outward direction between a ring-shaped region 32a of housing part 32 and an annular disk 80 fastened to housing part 32 by means of rivets 32b.

The ring-shaped region 32a of housing part 32 extends radially inwards from the external diameter of the resilient gasket 75, while between the ring-shaped region 32 and the gasket 75 a radial space 32c is formed. In this radially inwards open radial space 32c may find accomodation the small quantities of viscous medium which may leak between the inner region of gasket 75 and the counter seal reagions 76b and, at higher speeds of revolution-owing to the centrifugal force-can be forced back again between the ring-shaped region 32a and the gasket 75 into the ringshaped chamber 30. The contact zones between the inner regions of gasket 75 and counter-seal regions 76b are provided in the axial extension region of radial space 32c.

On the inner region of housing part 32 an axial indent or an axial step 91 is formed, the radially external enveloping surface of which axially overhangs the external regions of gasket 75.

The housing part 31 facing towards the engine carries internally an axial shoulder 20, which carries the roller bearing 16 which secures the mounting of the two flywheel elements 3 and 4 relative to each other. The pressed sheet metal part 31 is centred on a seat 20b of shoulder 20, and is supported axially on a radial surface 20c of shoulder 20, provided in continuation of seat 20b.

The joint between the pressed sheet metal part or housing part 31 and the axial shoulder 20 can be established by screw joint, riveting, welding or wedging.

The assembly of the two flywheel elements 3 and 4 is carried out by mounting, in the first instance, the roller bearing 16 on flywheel element 4 and the gasket 75 on flywheel element 3. By slipping the roller bearing 16 on seat 20a of shoulder 20 the plug-connection 42 is established and the gasket 75 is axially tensioned by bearing against the counterseal regions 76b provided on flywheel element 4.

By attaching the fastening plate 22, which radially overlaps the inner bearing ring of roller bearing 16, to the front face of shoulder 20, the two flywheel elements 3 and 4 are axially secured relative to each other. The attachment of plate 22 can be effected by riveting. However, screws can also be used instead of rivets.

In order to avoid that during the welding of the two housing parts 31,32 to each other the components being in contact therewith-- in particular the movable components-be welded locally to the housing parts or that they undergo structural changes owing to a localised overheating, an electrical insulation is provided between these components and the sheet metal housing parts 31,32. The components particularly at risk during the welding process are especially the springs 45 located in the ring-channel shaped recesses 51, as well as the flange 41 and the spring cups 59.

The insulator coating can be applied to housing parts 31,32 and/or to the components being in contact with these, namely 45,41,59,55,55a. Heren, the insulator coating can be applied in parts, that is to say, only on the contact regios between the housing parts and the other components.

The insulation can be advantageously ef fected by phosphate treatment of the individual components. Furthermore, certain components, for example the spring cups 59 and the peripheral stops 55,55a, can be made of a nonconductive material.

It is particularly advantageous to phosphatize at least the sheet metal parts and/or the flange for the purpose of insulation. The springs 45 will be expediently varnished, but can also be phosphate-treated.

For the purpose of insulating the housing parts 31,32 from the components being in contact therewith, coatings of ceramic, synthetic plastic or fatty material can also be used. Such coatings can be applied in particular to the housing parts 31,32.

If, during the insulating process, such as phosphate treatment, the sheet metal parts 31, 32 are fully coated, it is expedient to remove the previously deposited insulator layer in the region of the welding zones and in the region of the current-feed appliances, for examples in a mechanical operation, to ensure the provision in these regions of a faultless electrical conductivity.

When selecting the insulating material, care must be taken at all times to ensure that these are compatible with the viscous medium introduced into the ring-channel shaped recess 51.

The use of a phosphate layer as insulating layer is particularly advantageous, as this layer has wear-reducing and self-lubricating qualities.

Housing part 31 further has on its external periphery a seat 39, which accomodates a starter ring gear 40. Viewed along its circumference, the starter ring gear 40 is fast with the housing part 31 at least at some points by means of a weld 40a. This is advantageous in the pressed sheet metal embodiment of housing part 31, since owing to the limited wall thickness of housing part 31, the seat 39 does not extent over the whole width of the gear ring.

As is further apparent from Fig. 1, the engine-side housing part 31 is of a greater thickness than housing part 32.

As is apparent from Fig. 3, the circumferential stops 55,55a according to Fig. 1 can be replaced with lodgings stamped in the pressed sheet metal parts 31,32, such as the pockets 55c,55d. These pockets 55c,55d can be advantageously employed for the positioning of the two housing parts 31,32 as these are welded together. For this purpose, corresponding projections must be provided on the welding tool, which are adapted to the pockets 55c,55d. Further, these projections can constitute the electrodes for applying the required welding current to housing parts 31, 32. Moreover, the axial pressure required for the welding can also be applied by way of these projections to the housing parts 31,32.

It is here particularly expedient when these projecions of the welding tool are so arranged, that they assume a predetermined spacing throughout the welding process, which also ensures that, after welding, the two housing parts 31,32 assume a defined axial position relative to each other. This is important with regard to the springs 45 located in the ring-channel shaped recess 51 and, in particular, with regard to the definite clearance to be maintained between the two regions 60,61 and the flange 41 located in between, which clearance influences the hydraulic or viscous damping generated by the device.

The mode of functioning of the device according to Figs. 1 and 2 will now be described in the following.

During a rotation of the flywheel element 4 relative to flywheel element 3 from the rest position shown in Fig. 2, the flange 41 is driven by way of the plug connection 42, so that the springs 45 are compressed between the circumferential stops 55,55a and the radial projections 44. In the course of a relative rotation between the two flywheel elements 3 and 4, a frictional damping is generated by friction of the springs 45 against the surfaces of indentations 52,53, and this damping increases in magnitude as the speed of rotation increases. Moreover, a damping is generated by the turbulence or displacement of the viscous or pastous medium contained in the ringshaped chamber 30.In particular, the viscous medium present in the practically closed ringchannel shaped recess 51 generates a hydraulic or viscous damping, since the spring cups 59 in the ring-channel shaped recess exert a piston-like effect. During a compression of springs 45, the spring cups 59, acted on by projections 44, are displaced in the direction of the cups bearing against the circumferential stops 55,55a, so that the viscous medium present in the springs is displaced substantially through the gap 54, which acts in the manner of a throttle. A further portion of the viscous medium is displaced between the spring cups 59 and the wall portions of the ring-channel shaped recess 51. The initially inwards-displaced viscous medium, owing to the centifugal force acting thereon, again distributes itself uniformly over the circumference.

As the tension of springs 45 is released, the viscous medium present on that side of the spring cups 59 which faces away from spring 45 is pressed in a similar manner past the spring cups and through the gap 54 and, owing to the centrifugal force acting on it, again refills the springs 45. The damping generated by the viscous medium is dependent of the centrifugal force acting on the medium which means, that the damping increases as the speed of revolution rises.

By the provision of axial recesses or identations in at least some of the cups and by appropriate dimensioning of the gap 54 or of the external circumference of the cups, the damping generated by the viscous medium can be varied or adapted to each individual application. Moreover, the viscous or hydraulic damping can be adjusted by providing only some of the springs 45 with cups 59.

The invention is not limited to the form of embodiment herein described and illustrated, but also comprises variants having several springs stages. Thus, for example, as viewed in circumferential direction, at least some of the projections 44 may have a different extent than the circumferential stops 55,55a associated with them. It is therefore possible to have projections 44 with greater or even smaller angular proportions than the circumferential stops 55,55a associated with them. Furthermore, an additional damper with force accumulators can be arranged radially inside the damper 13, which damper can then be connected parallel or in series with damper 13.

Claims (33)

1. Vibration damper device, more especially a divided flywheel suitable for mounting between an engine and a drive member, having at least two component or flywheel elements rotatable relative to each other and drivably interconnected by means of springs, of which elements one is connected or is connectable to the engine and the other to the drive member, respectively, said device having a chamber which is at least partly filled with a viscous medium and which accomodates at least a portion of the springs, characterised in that the chamber (30) is arranged in a housing constituted by at least two shells (31,32) bonded to each other by welding.

2. Device according to Claim 1, characterised in that the shells (31,32) are formed of sheet metal.

3. Device according to Claim 1 or 2, characterised in that the shells (31,32) are welded to each other in the region of their outer circumference (at 38).

4. Device according to one of Claims 1 or 3, characterised in that both shells have a frontal region or an abutting surface (34,35) which are butt welded to each other.

5. Device according to one of Claims 1 to 4, characterised in that the two sheet metal shells (31,32) are bonded to each other by a pulse resistance weld (38).

6. Device according to one of claims 1 to 4, characterised in that the two sheet metal shells (31.32) are bonded together by a resistance butt weld (38).

7. Device according to one of Claims 1 to 4, characterised in that the two sheet metal shells (31,32) are bonded together by an impulse discharge weld (38).

8. Device according to one of Claims 1 to 7, characterised in that the abutting surfaces (34,35) of the two sheet metal shells (31, 32), heated to welding temperature, are joined together under pressure.

9. Device according to one of Claims 1 to 8, characterised in that an electrical insulation is provided between those components (41,45,59) of the device which, prior to welding, are in contact with and are movable relative to the shells (31, 32) and the shells (31, 32) themselves.

10. Device according to one of Claims 1 to 9, characterised in that at least one of the sheet metal shells (31, 32), located in a region of contact with the parts accomodated or fitted in the housing, such as hub flange (41), torsion springs (45), spring cups (59) or other movable parts, is provided with an insulator coating.

11. Device according to at least one of the preceding Claims, characterised in that at least some of the components, such as hub flange (41), torsion springs (45), spring cups (59) which, prior to welding, are in contact with at least one of the shells (31, 32), are provided with an insulator coating.

12. Device according to at least one of the preceding Claims, characterised in that spring cups (59) made of an electrically non-conductive material are provided.

13. Device according to at least one of the preceding Claims, characterised in that the insulation between the sheet metal shells (31,32) and at least some of the components (41,45,59) in contact therewith is formed by a phosphate layer.

14. Device according to one of Claims 1 to 13, characterised in that at least some of the components (31,32,41,45,59) are phosphatetreated.

15. Device according to at least one of the preceding Claims, characterised in that at least some of the components (31,32,41,45,59), in particular the compression springs (45), are lacquer-coated.

16. Device according to one of Claims 1 to 15, characterised in that the electrical insulator layer between the shells (31, 32) and at least some of the other components (41,49,59) is formed by a coating of at least one of the contacting components (31,32,41,45,59) with e.g. a ceramic, synthetic plastic or a fatty material.

17. Device according to at least one of the preceding Claims, characterised in that between the sheet metal shells (31,32) axial stops (67) operate, which become effective only during the welding together of shells (31, 32).

18. Device according to one of the preceding Claims, characterised in that in the region of the welding zones (34, 35), the sheet metal shells (31,32) are not coated.

19. Device according to one of the preceding Claims, characterised in that the sheet metal shells (31, 32) are rendered conductive in the region of the welding zones (34, 35) and in the region of current-feed appliance by the removal in these regions of the previously deposited insulator layer.

20. Device according to Claim 19, characterised in that the removal of the insulator layer is effected by mechanical processing.

21. Device according to at least one of the preceding Claims, characterised in that the sheet metal shells (31, 32) have circumferentially extending, channel-shaped recesses (51) for the springs (45), and the bearing surfaces in circumferential direction for the springs (45) are constituted by pocket-shaped axial stampings (55c,55d) which adjoin the end-portions of the spring recesses (51) and are formed in the sheet metal shells (31,32) and, for precise mutual positioning during the welding process, the sheet metal shells (31,32) are accomodated in the pockets (55c,55d).

22. Device according to at least one of the preceding Claims, characterised in that the sheet metal shells (31,32) have positioning means (65,66; 55c,55d) for precise location during the welding process.

23. Device according to Claim 22, characterised in that for the purposes of stable positioning the sheet metal shells (31,32) have countersunk portions (65, 66).

24. Device according to one of Claims 1 to 23, characterised in that the flywheel element (3) connectable to the engine (5) comprises the chamber (30) formed by the shells (31,32).

25. Device according to one of Claims 1 to 24, characterised in that the sheet metal shell (31) facing towards the engine (5) carries, in a radial internal position, an axial shoulder (20) which extends in the direction of the other flywheel element (4) connectable to the drive member (10), on which shoulder (20) the flywheel element (4) is accomodated so as to be rotatable over a roller bearing (16) relative to the flywheel element (3).

26. Device according to Claim 25, characterised in that the axial shoulder (20) and the engine-side shell (31) are welded to each other.

27. Device according to Claim 25, characterised in that the axial shoulder (20) and the engine-side shell (31) are riveted to each other.

28. Device according to Claim 25, characterised in that the roller bearing (16) located on the axial shoulder (20) is axially secured by means of a plate (22) fastened to the front face of said shoulder (20).

29. Device according to Claim 28, characterised in that the cover plate (22) is riveted to the axial shoulder (20).

30. Device according to one of Claims 21 to 29, characterised in that the channel-- shaped recesses (51) for the springs (45), which are formed by the sheet-metal shells (31,32) are adapted to the external diameter of the springs (45) and the channel-shaped recesses (51), which form discrete annular segments are, with the exception of a small slit, sealed by a flange element (41) which forms support regions (44) for the springs (45).

31. Device according to Claim 30, characterised in that the flange element (41) is rotationally coupled with the other flywheel element (4), but is not fixedly connected therewith in axial direction.

32. Device according to Claim 30 or 31, characterised in that the springs (45) can be supported on the radial extensions (44) formed by the flange element (41), which project into the channel-shaped recesses (51).

33. Device according to one of the preceding Claims, characterised in that the sheetmetal shell (31) facing towards the engine (5) carries a starter ring gear (40), which is welded at least locally (at 40a) to this shell (31).