GB2306620A

GB2306620A - Torsional vibration damper

Info

Publication number: GB2306620A
Application number: GB9621670A
Authority: GB
Inventors: Jorg Sudau
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Sachs AG
Priority date: 1995-10-18
Filing date: 1996-10-17
Publication date: 1997-05-07
Also published as: GB9621670D0; DE19538722C2; BR9605161A; DE19538722A1

Description

2306620 1 TORSIONAL VIBRATION DAMPER The invention relates to a torsional

vibration damper of the kind comprising an input-side flywheel and an output-side flywheel connected for relative rotation by gearing having at least one coupling element acting between the flywheels. Such a torsional vibration damper may be used in a motor vehicle clutch.

DE-A-42 00 174 shows a motor vehicle clutch with a torsional vibration damper of the kind set forth. The coupling elements are pivotally connected to a respective one of the flywheels and pivotally connected together, one element being a centrifugal weight and the other forming guide means. Under the effect of centrifugal force on operation of the clutch, the centrifugal weight of the coupling element is deflected radially outwards, whilst relative movements of the two flywheels with respect to one another cause a deflection of the centrifugal weight out of the position determined by centrifugal forces. In principle, with increasing speed, the inertia of the centrifugal weight against deflection from the radially outwardly directed position increases. Moreover, the faster the deflection on relative rotation of the two flywheels, the greater the effect of the inertia of the coupling elements.

In such a clutch the input-side flywheel, because of the abovemention inertia of the coupling elements which has to be overcome on relative displacement, acts as a substantially larger mass. Where the drive is an internal combustion engine, the input-side flywheel can effectively oppose variations in uniform running which arise. Because of reaction forces, this preserves the front end of the engine, in particular auxiliary components such as belt tensioners. There is however a disadvantage, because the coupling elements do not adopt any exactly 2 def ined starting position, at least without the speed of the flywheels, but can be pivoted into a position other than the radial position. The angle between the centrifugal weight and the guide links which engage them becomes more obtuse so that the major part of any sudden torque applied to one of the flywheels loads the connecting points of the two coupling elements and only a small residual part causes the necessary relative movement of the coupling elements for damping the vibrations. The advantage of minimal loading of the front end of the engine is accordingly offset by the disadvantages of an undefined starting position and an adverse effect on vibration damping especially in the two end positions of the centrifugal weights.

DE-C-36 30 398 shows a clutch in which two relatively rotatable flywheels are connected together through a set of circumferentially- extending springs. In order to achieve vibration damping this set of springs has a comparatively large spring travel and soft spring characteristics. As a result of this a sudden torque introduced at the input side will cause a substantial deflection of the input-side flywheel with respect to the output-side flywheel, accompanied by deformation of the set of springs. As a result the input-side flywheel acts with very low inertia so that variations in uniform running generated by an internal combustion engine can build up. Because of the reaction forces caused by the deflection of the input-side flywheel, this leads to a substantial loading of the front end of the engine. This can cause damage to auxiliary components over long periods of operation.

This invention is based on solving the problem of constructing a torsional vibration damper of the kind set forth so that the front end of the engine benefits and the two flywheels have an exactly defined relative position even when they are not rotating.

3 According to the present invention, in a torsional vibration damper of the kind set forth, at least one coupling element has a resilient device having one part connected to the input-side flywheel and a second part, spaced from the first part, connected to the output-side flywheel, the arrangement being such that relative angular movement of the two flywheels deforms the resilient device to produce a force opposing the relative angular movement.

The coupling elements have significant inertia against movement in particular at high speed and with relatively large acceleration on rapid relative movement of the two flywheels. This ensures that variations in uniform running originating from an internal combustion engine are opposed so that the front end of the engine benefits. At the same time, the resilient device connected to each flywheel ensures that, on the basis of the connection between the two flywheels through the coupling elements, the flywheels can also take up exactly defined starting positions relative to one another, even when there is no relative movement, and the resilient device is not deformed. As soon as the flywheels move relatively, the resilient device is deformed, the deforming force necessary being applied by the flywheels. As soon as the deforming force caused by the relative movement corresponds to the opposing force building up in the resilient device, a balance is achieved. Subsequent relief of the force enables the resilient device to return the two flywheels to their starting positions. Relative movements of the flywheels can occur in each of two opposite directions, leading to deformation of the resilient device in corresponding opposite directions.

Preferably each coupling element has a resilient device. The or each resilient device is connected at its ends to the respective flywheels, 4 to provide a compact arrangement. The connections between the ends and the flywheels preferably provide equal movements.

In a preferred embodiment the or each resilient device comprises a precurved leaf spring mounted at each end on a respective flywheel by respective mounting, the spring reducing its curvature in a first direction of relative movement of the flywheels by an increase in the circumferential spacing between the two mountings and increasing its curvature in the opposite direction of relative movement by a reduction in the circumferential spacing between the mountings. Such a spring can be made particularly compact and thanks to the pre-curving it can be extended by a reduction in the curvature or shortened by an increase in the curvature, according to the direction of the relative flywheel movement. It will be evident that because of its resilience the resilient device will return to its starting position on relief of the load. The connection of this device to the two flywheels is particularly simple, in that each end engages a respective associated mounting provided on the corresponding flywheel.

Conveniently, the or each resilient device has at least one centrifugal weight associated with it, the deformation of the resilient device being controlled by the centrifugal weight in response to the rotational speed of the flywheels and the acceleration of a relative movement of the flywheels. The centrifugal weight therefore influences the operating state in which the resilient device starts its deformation and consequently opposes a variation in uniform running. The mounting of the centrifugal weight affects the operating state. If the weight projects radially inwardly, the deformation of the resilient device is delayed so that it is only effective at higher rotational speeds or at higher acceleration of the relative movement of the two flywheels. If the weight is substantially radially outwardly directed, the opposite effect is achieved. Such a centrifugal weight may be secured to the or each resilient device in the region of the respective mounting. Alternatively, it may be secured in the region between the two mountings. The centrifugal weight or weights may also be provided with at least one stop which limits the deformation of the resilient device. In this way the amount of the relative movement between the two flywheels can be restricted to the predetermined amount.

Some embodiments of the invention are illustrated, by way of example, in the accompanying drawings, in which:- is Figure 1 is a longitudinal section through a torsional vibration damper with a coupling element acting between two flywheels including a resilient device in the form of leaf spring; Figure 2 is a section on the line A-A in Figure 1; Figure 3 is like Figure 2, but with centrifugal weights attached to the ends of the leaf spring; and Figure 4 is like Figure 2, but with respective centrifugal weights attached to opposite sides of the leaf spring.

Figure 1 shows a torsional vibration damper for a motor vehicle clutch, of the kind comprising an input-side flywheel 6 and an output-side flywheel 10 connected for relative rotation by gearing 50 having a coupling element 49 acting between the flywheels 6, 10. The input-side flywheel 6 is driven from a crankshaft (not shown) of a drive such as an 6 internal combustion engine through a hub 1, while the output-side flywheel 10 is connected to a gearbox shaft (not shown).

The input-side flywheel 6 has a flywheel disc 2 located on the hub 1. The disc 2 has a toothed ring 3 at its outer periphery and carries, on an axial extension 4 which is formed in its radially outer region, an inwardly directed sealing plate 5. The plate 5, together with the hub 1, the flywheel disc 2 and the axial extension 4 form the input-side flywheel 6. An inner bearing ring of a bearing 7 is provided on the hub 1 and secured axially in a manner not shown. The outer ring of the bearing 7 carries, looking axially, at one end a shoulder 8 of the output-side flywheel 10 and at the other end a disc 12 secured to the flywheel 10 by rivets 11.

The side of the output-side flywheel 10 adjacent the input-side flywheel 6 has a ring 9, provided with a pin 14 projecting towards the flywheel disc 2 and serving to receive one end of a resilient device 16.

The other end of the device 16 engages on a further pin 17 which is secured radially further out on a ring 15 formed on the inside of the flywheel disc 2. The pins 14 and 17 form mountings 18, 19 for the resilient device 16 which is arranged on the mountings 18, 19 through bearing elements 20, 21 to provide low friction for relative movement of the device 16 on the mountings. As can be seen better in Figure 2, the resilient device 16 comprises a spring device 22 in the form of a leaf spring 23 which encloses at each end the respective pin 14, 17 as well as the bearing 20, 21 with a respective eye 24, 25. The respective free ends of the eyes 24, 25 are welded to the adjacent ends of the leaf spring 23.

In this way the eyes 24, 25 enclose the associated mountings 18, 19. The leaf spring 23 itself is pre-curved. The resilient device 16 acts as a part of a coupling element 49 of the gearing 50.

7 The operation of this torsional vibration damper is such that on the introduction of a variation in uniform running originating from the internal combustion engine and applied to the input-side flywheel 6, the flywheel 6 moves angularly relative to the output-side flywheel either in a clockwise or a counter-clockwise direction in Figure 2. If it moves clockwise, then as long as the output-side flywheel 10 is still in a state of inertia, the mounting 19 is moved circumferentially away from the mounting 18 so that the leaf spring 23 is stretched and its curvature reduced. On this deformation of the spring 23 the eye, 24 pivots clockwise about the axis of the mounting 18, and the eye 25 pivots counter-clockwise with respect to the mounting 19. Conversely, if the input-side flywheel 6 moves in a counter-clockwise direction, the mounting 19 comes circumferentially closer to the mounting 18, increasing the curvature of the spring 23 and causing a counter-clockwise pivotal movement of the eye 24 about the mounting 18 and a clockwise pivotal movement of the eye 25 about the mounting 19. These deflections of the spring 23 from its starting position shown in full lines in Figure 2 are shown in broken lines. The deflection of the leaf spring 23 in the respective direction of deformation terminates when the deflecting force introduced through the input-side flywheel 6 has reached a balance with the opposing spring force. On relief of the load on the spring 23 it returns to its starting position and accordingly the input-side flywheel 6 and the output-side flywheel 10 returns to their initial relative positions.

At high speeds of rotation of the flywheels 6 and 10 an effect resulting from the action of centrifugal force is superimposed on the previously described deflection of the leaf spring 23. Moreover, the rate of displacement of the input-side flywheel 6 with respect to the output- side flywheel 10 and thereby the rate of deflection of the leaf spring 23 8 also influences operation. In general, the higher the rate of deformation of the spring 23 the more noticeable its inertia behaviour becomes. In the present example, because of the pre-curving of the leaf spring 23, the action of the centrifugal force and also the inertia resistance to deformation, the spring behaviour on tension operation of the torsional vibration damper is different from that on compression operation, the one kind of operation being present for example when input-side torques are introduced and the other when torques are introduced from the output side.

Figure 3 shows the torsional vibration damper already described in relation to Figures 1 and 2, but with the addition of centrifugal weights 28, 30. The weight 28 engages over the eye 24 and the weight 30 engages over the eye 25, the respective engagement being secured by a welded connection to the associated eye 24, 25. The centrifugal weights 28, 30 are directed radially outwards and at high rotational speeds of the flywheels 6, 10 they cause a pivotal movement of the eye 24 in a counter clockwise direction and of the eye 25 in a clockwise direction. In this way the curvature of the leaf spring 23 is increased, so that it pulls the two mountings 18, 19 further together. As a result, in comparison to the situation without centrifugal weights 28, 30 in which the spring 23 becomes operative on torsional vibration, small variations in uniform running introduced through the input-side flywheel 6 cause a deformation and therefore damps out relative movement between the flywheels 6 and 10 more softly. In another arrangement of the centrifugal weights 28, 30 (not shown) in which these project substantially radially inwards, the tendency can be reversed so that the spring 23 only experiences a deflection with larger variations in uniform running.

9 The left hand weight 28 in Figure 3 has an opening 32 for the leaf spring 23. The edges of the opening 32 on each side of the spring 23 act as stops 33, 34 for the spring. The amount of deflection of the spring 23 in both directions is limited by these stops.

Figure 4 shows an embodiment which is similar to that of Figure 3, but has the centrifugal weights secured in a different place. In Figure 4, the centrifugal weights 35, 36 are secured to the leaf spring 23 in a region between the mountings 18, 19. The weights 35, 26 are not directed radially with respect to the axis of rotation of the flywheels 6, 10 so that they exert a torque acting in a counter-clockwise direction, causing an increase in curvature of the spring 23. Selecting a different point of attachment of the weights 35, 36 to the spring 23 can reverse the direction of action of this torque, so that the deflection behaviour of the spring 23 can be influenced in the opposite direction. It is also possible to omit one of these weights 35, 36 and thereby influence the deflection behaviour of the spring 23 in the associated direction.

Claims

1. A torsional vibration damper of the kind set forth, in which at least one coupling element has a resilient device having one part connected to the input-side flywheel and a second part, spaced from the first part, connected to the output-side flywheel, the arrangement being such that relative angular movement of the two flywheels deforms the resilient device to produce a force opposing the relative angular movement.

2. A torsional vibration damper as claimed in claim 1, in which each coupling element has a resilient device.

3. A torsional vibration damper as claimed in claim 1 or claim 2, in which the or each resilient device is connected at its ends to the respective flywheel.

4. A torsional vibration damper as claimed in any preceding claim, in which the or each resilient device comprises a pre-curved leaf spring mounted at each end on a respective flywheel by a respective mounting, the spring reducing its curvature in a first direction of relative movement of the flywheels by an increase in the circumferential spacing between the two mountings and increasing its curvature in the opposite direction of relative movement by a reduction in the circumferential spacing between the mounting.

5. A torsional vibration damper as claimed in any preceding claim, in which the or each resilient device has at least one centrifugal weight associated with it, the deformation of the resilient device being controlled 11 by the centrifugal weight in response to the rotational speed of the flywheels and the acceleration of a relative movement of the flywheels.

6. A torsional vibration damper as claimed in claim 4 and claim 5, in which at least one centrifugal weight is secured at each end of the or each resilient device in the region of the respective mounting.

7. A torsional vibration damper as claimed in claim 6, in which at least one of the centrifugal weights is provided with at least one stop which limits the deformation of the resilient device.

8. A torsional vibration damper as claimed in claim 4 and claim 5, in which at least one centrifugal weight is secured to the or each resilient device in the region between the two mountings.

9. A torsional vibration damper of the kind set forth substantially as described herein with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.

10. A torsional vibration damper of the kind set forth substantially as described herein with reference to and as illustrated in Figure 3 of the accompanying drawings.

11. A torsional vibration damper of the kind set forth substantially as described herein with reference to and as illustrated in Figure 4 of the accompanying drawings.