GB2329444A

GB2329444A - Torsional vibration damper having coaxial springs with differing torsional stresses or spring forces.

Info

Publication number: GB2329444A
Application number: GB9815043A
Authority: GB
Inventors: Bernhard Schierling; Bernd Forster; Hilmar Goebel; Jurgen Kleifges
Original assignee: Mannesmann Sachs AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1997-07-12
Filing date: 1998-07-10
Publication date: 1999-03-24
Anticipated expiration: 2018-07-10
Also published as: GB9815043D0; FR2765933B1; GB2329444B; ES2142764A1; ES2142764B1; FR2765933A1; DE19730001A1

Abstract

A torsional vibration damper has an input member 1 connected to an output member 3 via coaxially arranged springs 22, 24. The torsional stress, or spring force, of each radially outermost spring 22 is less than or equal to the radially inner spring 24 that it encloses. Each spring assembly may be supported by end caps 17 and sliding shoes 29, or within a guide path (35, Figure 2).

Description

2329444 1 TORSIONAL VIBRATION DAMPER The present invention relates to a

torsional vibration or oscillation damper.

DE 41 28 868 AI discloses a torsional vibration damper with a input transmission member and an output transmission member coaxial to one another. The output member is able to be deflected by rotation relative to the input member. The input and output members are connected together by way of damping means more particularly with energy storage devices in the form of torsion springs. The torsion springs can be acted upon by control members provided on the transmission members. Figure 1 shows by way of example a control member extending radially outwards from a hub disc, which control member acts by way of spring cups on a pair of torsion springs, which are in turn again connected by way of sliding shoes to other torsion springs. The spring cups as well as the sliding shoes form sliding members which possess projections extending respectively in the direction of adjacent sliding members in the peripheral direction. The projections extend radially outwards towards and are active both as radial supports for the torsion springs as well as stops for limiting the spring compression. To promote a good sliding ability, the spring cups and the sliding shoes may be provided at least on their radial outer side with an addition of'Teflon'. Synthetic material reinforced with glass fibres or carbon fibres can be adopted as the basic material. These spring cups and sliding shoes control the torsion springs. According to Figure 2 of this publication two springs can fit radially one in the other, 2 In torsional oscillation dampers of this type, the radially outermost torsion spring, which should transmit the highest torques, will usually be adjusted so that the torsional stress in its turns comes as close as possible to a predetermined load limit. A second torsion spring located radially within this torsion spring is likewise adjusted so that it comes close to this limit value. However on account of its smaller turn diameter, the torque able to be transmitted by this torsion spring is generally lower than in the case of the outer torsion spring.

As soon as the torsion spring is deformed upon the introduction of a relative movement between the transmission members, it withdraws from its position shown in Figure 1 relative to the spring cup and sliding shoe and comes to bear with its regions located within the respective radial support, as regards respectively the last turns, against this radial support. The turn region of the torsion spring remaining respectively between two of these radial supports on the other hand experiences a deflection radially outwards, caused by centrifugal force. As the compression of the torsion spring increases, the turn adjacent to the free end of the associated radial support in the compression direction comes to bear against this radial support. Thus, the force introduced, bringing about the deformation of the torsion spring, cannot be transmitted by this turn which is prevented from a further movement by the radial support any longer to the turns remaining radially within the radial support. Due to this effect the deformation travel of the torsion spring is shortened by the proportion of the last-mentioned turns. Furihermore, the adjacent turns on one side of this blocked turn clinging to the radial support, can move closer towards each other than is specified by the dimension of the radial supports in the peripheral direction.

3 Due to this, these adjacent turns can be subjected to a load which exceeds the predetermined limit value and, particularly if the turns even move with each other as a block, this can lead to breaking ofthe torsion spring. This problem is again consequently increased if according to Figure 2, located radially within the torsion spring is a further 0 torsion spring, which under the effect of centrifugal force is supported radially on the outer Z> torsion spring and thus increases the total spring mass relevant to the centrifugal force.

In principle the same problem exists for the radially inner torsion spiiing, in that its turns are pressed under high surface pressure against the inner diameter of the radially outer torsion spring. However, due to the low weight of the radially inner torsion spring, the deflection caused by centrifugal force is reduced. Furthermore, both torsion springs are generally located in a grease chamber filled at least partly with a viscous medium, so that in the case of steel to steel contact of the torsion springs, a relatively small frictional value occurs. The situation is different in the case of the outer torsion spring, if the spring cup or the sliding shoe, with which it has frictional contact respectively, consist of synthetic material, which for reasons of strength contains glass or carbon fibres, which due to wear arrive on the surface. The result is an increased braking or blocking action.

DE 40 18 321 AI illustrates in Figure 2 a torsional oscillation damper, which, likewise between two transmission members, comprises a damping means with energy storage devices in the form of torsion springs. Here also, two torsion springs are located radially one in the other. A guide path is provided for the radially outer torsion spring to support the sprina radially on the outside. By designing both torsion springs close to a I- 4 predetermined limit value, the highest torques can be transmitted by these torsion springs, however the problem still exists that due to centrifugal force the turns are pressed radially outwards and in particular the turns of the radially outer torsion spring in this 'case come into frictional connection with the guide path. What cannot be seen from Figure 2 is that the individual turns of such a torsion spring do not have exactly the same diameter, but fluctuate within certain diameter tolerances. Turns with relatively large diameter may be caught on the radially outer guide path, so that the turns, which are located on the side of the clinging turn remote ftom the torque introduced, can no longer be used for receiving this torque. Instead of this, a greater deformation than was structurally intended occurs for the turns in front of the clinging turn, so that an excessively high bending stress is superimposed on the torsional stress in the turns. The result of this is damage or even breakage.

It is the object of the invention to construct a damping device on a torsional oscillation damper so that damage or breaking of energy storage devices, in particular of torsion springs thereof, is avoided.

According to the invention there is provided a torsional vibration damper with an input transmission member, an output trarisrnission member to be rotationally deflected coaxially with respect to the input member, damping means composed of energy storage devices interconnected between the input and output members and associated control members connected to the transmission members wherein the energy storage devices are composed of torsion springs arranged in sets one radially within another and the torsional stress of each radially outermost torsion spring is less than the torsional stress of the radially inner torsion spring received in this outermost torsion sprint,' In another aspect the invention provides a torsional vibration damper with an input transmission member, an output transmission member to be rotationally deflected with respect to the input member and damping means composed of energy storage devices interconnected between the input and output members and associated control members connected to the transmission members wherein the energy storage devices are composed of torsion springs arranged in sets radially within one another and the torque/spring force of each radially outermost torsion spring is less than or equal to the torque/spring force of at least one radially inner torsion spring received in this outermost torsion spring.

As already mentioned at the beginning, all the torsion springs lying radially one in the other can be adjusted so that the torsional stress thereof approaches a certain limit value.

However, according to the invention, the torsional stress of the radially outermost torsion spring is reduced, whereas the torsional stress of the torsion spring located radially therein remains the same or, for an at least partial compensation of the loss of torque which can be transnutted, caused by the reduction of torsional stress on the radially outermost torsion spring, is even slightly increased. Due to this, the aforedescribed problem, according to which a spring turn clings to a spning-guide member, such as for example a sliding member or a guide path, the radially outermost torsion spring can always be compressed even more derably than structurally intended and due to this the bending stress occurring in the consi 0 turns is higher than desired. However, in the case of a reduction of the torsional stress in 7 6 the turns, this will no longer lead to a breakage of the torsion spring, since its initial load is already reduced with respect to a torsion spring with a higher torsional stress. On the other hand, in the case of the radially inner torsion spring, despite the constantly high or even higher torsional stress, no breakage is to be expected, since on account of a lower specific weight, and the possibility of being supported against the radially outer torsion spring, the former spring is subject to a lower bending stress than the radially outer torsion spring.

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

Embodiments of the invention will now be described, by way of examples only, with reference to the accompanying drawings, wherein; Figure 1 is a partial view of a torsional oscillation damper constructed in accordance with the invention in which the torsion springs are supported by way of spring cups and sliding shoes; Figure 2 is a view corresponding to Figure 1, in which a guide path serves to support and guide the torsion springs. and Figure 3 shows two torsion springs located radially one in the other under the action of load and centrifueral force.

7 Figure 1 shows a torsional oscillation damper in the form of a dual mass flywheel, which comprises a first flywheel mass acting as input transmission member 1 and a second flywheel mass 3 coaxially rotatable with the member 1 and acting as the output transrnlission member 3. The members 1, 3 are connected together with the aid of damping means 6.

The construction of such a torsional oscillation damper is given essentially in the aforementioned publication DE 41 28 868 AI.

To receive this damping means 6, an annular space 7 is formed in the transmission member 1 at the output side, into which projects a control member 9 provided on the radially outer side of a hub disc 5 associated with the transmission member 3 at the output side. Seen in the peripheral direction, a pair of spring cups 17 are in abutment on both sides with this control member 9, and only one of the spring cups 17 is illustrated in Figure 1.

The latter comprises a peripheral support 10 for one end of a radially outer torsion spring 22 and a second torsion spring 24 located therein. The radially outer torsion spring 22 is held on its last turns 25 facing the spring cup 17 by a radial support 19 of this spring cup 17. The peripheral free end 20 of this radial support 19 is directed towards a sliding shoe 29. A peripheral support 10 of -the shoe 29 supports the respective other ends of the torsion springs 22 and 24. In the same way as the spring cups 17, the shoe 29 is active as a sliding member 30. The last turns 25, 26 at this end of the torsion springs 22, 24 are surrounded by a radial support 3 1 of the sliding shoe 29, this radial support J3 1 being directed towards the adjacent spring cup 17. Provided that the torsion springs 22, 24 are not extremely compressed, a gap 34 remains between the free end 33 of the radial support 31 and the free end 20 of the radial support 19, which gap, in the same way as the remaining, annular space 8 7, is filled at least partly with viscous medium and accordingly is part of a grease chamber 11. The two torsion springs 22, 24 form an energy storage device 27. The latter is connected by way of the sliding shoe 29 to a further energy storage device 27, the sliding shoe 29 comprising a radial support 32 on its side facing a further sliding shoe 29. After a number of such energy storage devices 27, which can be predetern-lined, this damping means 6 is supported in a manner which is not shown against a further control member, which is provided on the input transmission member 1. In this way, torsional vibrations which are introduced are transmitted by the damping means 6 from one of the transmission members 131 respectively to the other 3.

In Figure 1, the torsion springs 22, 24 are shown in the load-free state without rotary movement of the members 1, 3. Under load, the individual turns 25, 26 of the springs 22, 24 are moved closer together (Figure 3), whereas due to centrifilgal force, at the same time the torsion springs 22, 24 are bent radially outwards both in the region of the radial support 19 of the spring cup 17 as well as in the region of the radial support 31 of the sliding shoe 29. The springs 22, 24 come to bear respectively against the radial inner sides 40, 41 of the supports 19, 3 1, whereas in the gap 34 the springs 22, 24 project outwardly of the radial region of the radial supports 19, 3 1. Where the torque is introduced in counterclockwise direction according to Figure 1 by the control member 9, the spring cup 17 moves in the direction of the adjacent sliding shoe 29. The spring turns 25, 26 adjacent to the end 33 of the radial support 31, located in the gap 34, which in Figures 2 and 3 is provided with the reference numeral 28, will come to bear against the free end 3) 3 of the radial support 3 1.

The tums 25, 26 remote from the torque introduced, with respect to the tum 28, expedience 9 no further deformation and thus no longer supply part of the spring deflection force of the torsion springs 22, 24. However, the turns 25, 26 on the torque side of the turn 28, are compressed more greatly than desired up to the turn 28, so that the latter could experience undesirably high bending stresses and possibly could even act as a block. In this case, the two radial supports 19 and 31 of the spring cup 17 and sliding shoe 29 cannot be active, since despite the turns 25, 26 of the torsion springs 22, 24 being too close to each other, they are not yet in contact. According to the invention, the torsional stress in the radially outer torsion spring 22 is reduced so far that even in the case of high bending stress, the total stress in the turns 25, 26 does not exceed an admissible total amount. Due to this measure, the radially outer torsion spring 22 is protected from damage. On the other hand, the radially inner torsion spring 24 can be constructed with an unchanged high torsional stress, because the total load on this torsion spring 24 is less than that on the radially outer torsion spring 22.

In the embodiment according to Figure 2, the grease chamber 11 in the transmission member 1 at the input is enclosed by a sleeve 37 acting as a guide path 35, on which sleeve the radially outer torsion spring 22 of an energy storage device 27 is radially supported.

Since the individual turns 25 of the torsion spring 22 move within a certain tolerance range as regards their outer diameter, due to centrifugal force, a turn 28 with a relatively large outer diameter may easily become securely blocked on the guide path 3) 5 under the torque load, with the simultaneous influence of centrifugal force. Also in this case, the spring deflection on the side of the blocked turn 28 remote from the introduction of torque, would be lost for the ener storae device 27. The consequence of a spring breakage on the gy 0 0 opposite side of the turn 28, may however be prevented by reducing the torsional stress in the radially outer torsion spring 22. Also with this construction, the inner torsion spring 24 may still be constructed with unchanged torsional stress.

Due to the construction of the two torsion springs 22, 24 with different torsional stresses, both in the construction according to Figure 1 as well as in that according to Figure 2, the distance between respectively two turns 25 of the radially outer torsion spring 22 is less than between respectively two turns 26 of the radially inner torsion spring 24.

11 List of Reference Numerals 1. 3. 5. 6.

10.

13. 17 1920.

Input transmission member/flywheel mass Output transmission member/flywheel mass Hub disc Damping means Annular space 9. Control member Penipheral support Grease chamber Axis of rotation Spring cup Radial support Free end 22, 24. Torsion springs 25, 26. Spring turn 27, Energy storage device 28. Turn of spring 22 29. Sliding shoe 30. Sliding member 3 1, 3) 2. Radial supports 33. Free end Gap 34.

12 35. Guide path 37. Sleeve 40, 4 1. Radially inner faces of radial supports 13

Claims

1. A torsional vibration damper with an input transmission member, and an output transmission member able to be rotationally deflected coaxially with respect to the input member and damping means composed of energy storage devices interconnected between the input and output members and associated control members connected to the transmission members wherein the energy storage devices are composed of torsion springs (22, 24) arranged in sets one radially within another and the torsional stress of each radially outermost torsion spring (22) is less than the torsional stress of the radially inner torsion spring (24) received in this outermost torsion spring (22).

2. A torsional vibration damper with an input transmission member, an output transmission member to be rotationally deflected with respect to the input member and damping means composed of energy storage devices interconnected between the input and output members and associated control members connected to the transmission members wherein the energy storage devices are composed of torsion springs (22. 24) arranged in sets radially within one another and the torque/spring force of each radially outermost torsion spring (22) is less than or equal to the torque/sprin. force of at least one radially inner torsion spring (24) received in this outermost torsion spring (22)-

3. A damper according to Claim 1 or 2, wherein the distance between two respective turns (26) of the inner torsion spring (24) at least in the unloaded state is greater than that between two respective turns (25) of the outer torsion spring (22).

14

4. A damper according to Claim 1 or 2, wherein the torsional stress of the radially C1 outermost torsion spring (22) is reduced so far that even with increased bending stress in the turns (25), the total stress able to be tolerated by the latter without damage, is not exceeded.

5. A dual mass flywheel incorporating a torsional vibration damper or a torsional vibration damper substantially as described with reference to and as illustrated in any one or more of the Figures in the accompanying drawings.