Torsional vibration damper

Details Torsional vibration damper Torsional vibration damper

1997-08-05

2002-02-05

Marmor, Charles A (Department: 3681)

192 clutches and power-stop control

Elements

Clutch element resiliently carried on hub

C464S068800

Reexamination Certificate

active

06343684

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a torsional vibration damper, in particular for a clutch disk for damping torsional vibrations in the drive train of an internal combustion engine. The torsional vibration damper includes a disk-shaped first damper part, a second damper part which is rotatable about an axis with respect to the first damper part, and a torsion bar device or torsion spring device with at least one torsion spring unit.
2. Description of the Prior Art
Torsional vibration dampers of this kind are used, for example, in clutch disks in order to enable damping of torsional vibrations occurring in the power transmission path between an internal combustion engine and the driving wheels of a vehicle. A clutch disk with a known torsional vibration damper is shown in FIG.
12
. This known clutch disk
8
s
comprises a hub
10
s
which is mountable, for example, on a transmission input shaft so as to be displaceable in the longitudinal direction of the shaft, but is fixed with respect to rotation about an axis A with the transmission input shaft. A hub disk
12
s
is fixed on the hub
10
s
, e.g., by welding or the like. A driver disk
14
s is arranged in the axial direction on one side of the hub disk
12
s
. A cover plate
16
s
is arranged on the opposite side of the hub disk
12
s
and is fixed with the driver disk
14
s
by a plurality of bolt elements
18
s
. The driver disk
14
s
is connected in the radial inner region with a bearing ring
20
s
so as to be fixed with respect to rotation relative thereto. The bearing ring
20
s
is rotatably supported on the hub
10
s
. A plate spring
22
s
is arranged between the hub disk
12
s
and the cover plate
16
s
and pretensions the input part of the clutch disk
8
s
in the axial direction, which input part is formed of the driver disk
14
s
and cover plate
16
s
, so that the bearing ring
20
s
contacts the hub disk
12
s
with pretensioning, possibly with the intermediary of friction linings or the like. In a radial outer region, the driver disk
14
s
is coupled with friction linings
24
s
which can be clamped in a manner known per se between a flywheel and a contact pressure plate of a motor vehicle clutch for transmitting torque.
Circumferentially extending spring windows
26
s
,
28
s
,
30
s
are provided in the hub disk
12
s
, the driver disk
14
s
and the cover plate
16
s
. A spring
32
s
is arranged in the spring windows
26
s
,
28
s
,
30
s
. The ends of the spring
32
s
contact control edges
34
s
,
36
s
,
38
s
of the hub disk
12
s
or of the driver disk
14
s
and the cover plate
16
s
, the ends being located opposite one another in the circumferential direction. Due to the spring
32
s
, the hub disk
12
s
is pretensioned in a predetermined rest position with respect to the driver disk
14
s
and the cover plate
16
s
. When torque occurs, the spring
32
s
is compressed so that rotation can occur between the hub disk
12
s
and the driver disk
14
s
and cover plate
16
s
. The spring
32
s
cooperates with the bearing ring
20
s
which contacts the hub disk
12
s
accompanied by pretensioning in order to damp torsional vibrations in a manner known per se. In clutch disks of this type, a plurality of springs are arranged in succession in the circumferential direction in windows provided in a suitable manner, although this is not shown in FIG.
12
.
The problem in torsional vibration dampers of this kind is that the springs must have a sufficiently large spring constant on the one hand and an adequate spring length on the other hand in order to provide good and defined damping characteristics. However, if the spring length is too great, the springs tend to expand outward in their radial center regions due to their pretensioning. In so doing, they contact the respective outer rims of the spring windows in the hub disk or the driver disk and cover plate, so that the friction in the torsional vibration damper constructed in this way is appreciably increased due to this contact. Since this frictional force depends upon the extent of compression of the spring, its contribution to the friction moment provided between the hub disk and the driver disk and cover plate can be calculated only with difficulty and this frictional force should accordingly be prevented.
A torsional vibration damper with an amplitude-dependent friction moment is known from the German Patent DE 34 31 809. In this known torsional vibration damper there is also a hub disk arranged in the axial direction between a driver disk and a cover plate. Spring windows for receiving springs are again formed in the hub disk and the driver disk and cover plate. In particular, for this purpose, two springs following one another in the circumferential direction are arranged in the corresponding spring windows in the hub disk and the driver disk and the cover plate and accordingly form a torsion spring unit. The torsion spring unit constructed in this way again contacts control edges of the spring windows in the hub disk or the driver disk and the cover plate by its ends which are arranged at a distance from one another in the circumferential direction. A spring contact arm of an intermediate disk is arranged between the ends of the spring which face one another. In order to provide the amplitude-dependent friction moment in this known torsional vibration damper, a first friction device is provided, on the one hand, which acts directly between the hub disk and the driver disk and cover plate. On the other hand, a second friction device is provided which acts between the intermediate disk and the driver disk. Accordingly, one of the two springs of the torsion spring unit is bridged by the second friction arrangement depending upon the torque transmission direction.
Another problem in this known torsional vibration damper is that the torsion spring unit formed by the two springs contacts an outer edge of the spring window formed in the hub disk or the driver disk and cover plate substantially along its entire outer circumferential surface, especially due to its pretensioning. In this known torsional vibration damper, also, this leads to the disadvantage that an additional friction moment which can be calculated only with difficulty is generated in the torsional vibration damper due to the pretensioning of the torsion spring unit which accordingly occurs in the radial outward direction.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a torsional vibration damper, especially for a clutch disk for damping torsional vibrations in the drive train of an internal combustion engine, in which the occurrence of unintended friction moments is prevented.
In accordance with a first aspect of the present invention, this object is met by a torsional vibration damper, especially for a clutch disk for damping torsional vibrations in the drive train of an internal combustion engine, comprising a disk-shaped first damper part, a second damper part which is rotatable about an axis with respect to the first damper part, and a torsion spring device with at least one torsion spring unit. The at least one torsion spring unit comprises at least two springs which are arranged substantially following one another in the circumferential direction. Ends of the torsion spring unit, which are directed opposite to one another in the circumferential direction, cooperate with the first damper part and second damper part with respect to operation for damping torsional vibrations. The damper further includes at least one intermediate ring element which is rotatable about the axis with respect to the first damper part and the second damper part and with at least one spring contact arm for the at least one torsion spring unit. The spring contact arm extends substantially radially with respect to the axis and is arranged in the circumferential direction between ends of the at least two springs of the at least one torsion spring unit, which ends face one another. The at least one intermediate ri

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