GB2296072A

GB2296072A - Torsional vibration damper

Info

Publication number: GB2296072A
Application number: GB9525375A
Authority: GB
Inventors: Jorg Sudau
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1994-12-13
Filing date: 1995-12-12
Publication date: 1996-06-19
Also published as: CN1131241A; ES2125775B1; GB9525375D0; FR2728040A1; ES2125775A1; DE4444200A1

Description

1 TORSIONAL VIBRATION DAMPER 2296072 The invention relates to a torsional

vibration damper of the kind comprising an input transmission element, an output transmission element, and a spring device located on at least one of the input and output transmission elements. Such torsional vibration dampers are used particularly in clutches of motor vehicles.

DE-C36 30 398 describes a two-mass flywheel by which it is possible to reduce even large torsional vibrations which are transmitted on the introduction of a torque by a drive, such as an internal combustion engine on an input transmission element of the two-mass flywheel. The reduction takes place on the transmission of the respective torsional vibration from the input transmission element to the output transmission element through a set of springs assisted by a friction device.

In contrast to a single mass flywheel the two flywheels of a twomass flywheel arrangement are relatively light so that a large primary-side mass, comprising the input drive and the primary-side flywheel is opposed solely by a smaller secondary-side flywheel on the output side, usually the gearbox side. This means that the resistance torque for the drive, which is determined by the inertia of the primary side, a reaction torque due to the effect of the springs, the friction and the inertia of the secondary flywheel, is relatively small so that it has only little effect in reducing the variations in smooth running of the drive. Variations in smooth running cause variation in torque at the front of the engine, to which auxiliary items such as a generator are connected. The variations in torque can cause damage to these auxiliary items.

2 The invention is based on solving the problem of forming a torsional vibration damper in such a way that it has a low-mass construction, but reduces variations in smooth running of the drive in the best possible manner.

According to the present invention, a torsional vibration damper of the kind set forth includes a gearing system acting between the input transmission element and the output transmission element and dividing a torque associated with a torsional vibration into partial torques, at least one of the input and output transmission elements being connected through the spring device to at least one element of the gearing system, the arrangement being such that on application of the torque associated with a torsional vibration, a corresponding differential torque formed from the sum of the partial torques deforms the spring device of which the spring constant is matched to a deformation torque corresponding to the input torque multiplied by the gear ratio of the gearing system.

The gearing system divides the torque associated with a torsional vibration into a first part which tries to accelerate the output transmission element in the same direction as the input transmission element and a second part acting in a predetermined direction. The two partial torques engage opposing ends of the spring device which has a spring constant designed for a deformation torque which results from the maximum torque capable of being introduced by the input drive, multiplied by the gear ratio of the gearing system. As the two partial torques acting on the spring device correspond in total to the input torque, and the spring constant is tuned to the larger deformation torque, the differential torque is conducted through the spring device from the gearing system element to the output transmission element without a substantial deformation of the spring device. Thus, the gearing system element and the output 3 transmission element, and, on appropriate coupling of the gearing element to the input transmission element, the two transmission elements perform only a minimal relative rotation. This almost gives the effect of an overall mass comprising the input transmission element, gearing system element and output transmission element, so that the inertia torque which opposes the variations in smooth running of the input drive is apparently increased in comparison with a torsional vibration damper in which large relative movements between the individual masses are allowed. As a result there are minimal variations in torque at the front of the engine.

Thus, the loads on the auxiliary units connected to the front on the engine can be reduced nearly as far as when a single mass flywheel is used, but without having to take into account its main disadvantage, which is the absence of filtering of very low frequency vibrations.

Preferably a flywheel is associated with each transmission element, and the gearing system element acts as an intermediate mass of which the direction of displacement from a rest position on application of a torque associated with a torsional vibration is reversed by at least one component of the gearing in opposition to the direction of the applied torque. This provides an advantageous arrangement of the gearing system, by which the element acting as an intermediate mass produces a partial torque which opposes the input torque.

Advantageously the gearing system comprises a planetary gearing system having at least one planet wheel comprising the gearing component by which an annulus acting as the intermediate mass is rotated about the axis of the planetary gearing system in a direction opposite to the direction of rotation of the input transmission element. The or each planet wheel provides in a particularly simple manner a reversal of the 4 direction of action of the annulus of the gearing system with respect to the input component, such as a sun-wheel. If the annulus is connected through a set of springs and a friction device to a planet carrier acting as the output transmission element, it can be driven in the opposite direction 5 to the input sun-wheel.

Preferably a gearing element which is not acting as an intermediate mass does not move relative to the input or output transmission element while a gearing element comprising an intermediate mass by means of the spring device is adapted to move relative to the transmission elements. This makes full use of the planetary gearing, since the spring device is arranged between the intermediate mass and one of the transmission elements, preferably the output element, so the intermediate mass can be driven with a gear ratio predetermined by the planetary gearing system with respect to the input transmission element. Conveniently the intermediate mass is driven with respect to the input transmission element with a gear ratio by which the torque required for displacing the intermediate mass from its rest position is increased in comparison with a state without the gear ratio. The gear ratio is preferably to be chosen in such a way that the intermediate mass makes necessary as large a torque as possible for moving it from its rest position, giving the impression of a large moment of inertia. Because of the gear ration the intermediate mass acts as a substantially larger mass and thereby reduces the loading on the front of the engine. Preferably the gear ratio is chosen to be greater than one.

An embodiment of the invention by way of example is illustrated in the accompanying drawing, in which:- Figure 1 shows in section a torsional vibration damper with a planetary gearing system coupled to an input transmission element.

The torsional vibration damper of Figure 1 has a first flywheel 1 acting as an input transmission element 3, a second flywheel 45 acting as an output transmission element 46, a spring device 28 and a planetary gearing system 102 arranged between the input and output transmission elements. The flywheel 1 has on its peripheral edge a toothed ring 2 for a starter pinion (not shown). A radially inner region of the flywheel 1 is attached to a hub 4, which is secured to a crankshaft, not shown, of an internal combustion engine, by means of rivets 5. The rivets 5 also secure a sun-wheel 7 of the planetary gearing 102 and a flange 8 on the hub 4. The planetary gearing 102 has two planet carriers 9 arranged on opposite sides of the sun-wheel 7, and held axially spaced by sleeves 103. The carriers 9 are pulled tightly against the ends of the sleeves 103 by rivets 21. The left hand planet carrier 9 extends radially inwards as far as the flange 8, while the right hand planet carrier has its radially inner end in engagement with one of a pair of heat shields 61 of L-shaped cross-section which protects a bearing 60 from heat. The heat shield 61 adjacent the planet carrier has its limb 62 extending radially inwards as far as the inner bearing race. This limb 62 adjacent the planet carrier 9 has a sealing function with respect to a chamber 44, which is partially filled with a pasty or viscous medium and is described in detail later.

The two planet carriers 9 are provided with a plurality of bearing members comprising needle rollers 18, arranged on a common diameter, around the sleeves 103. On each of the rollers 18 is mounted a planet wheel 20 arranged between the two planet carriers 9. The rivets 21 connect a cranked disc 22 securely to the planet carrier 9 which is further from the primary flywheel 1. A shoulder 23 formed on the disc 22 comes 6 into engagement against the limb 62 of the heat shield 61 remote from the planet carrier 9.

The planet wheels 20 mesh radially inwards with the sun-wheel 7 and radially outwards with an annulus 24 which is arranged between the two planet carriers 9 and acts as an intermediate mass 50. Outside its toothed engagement with the planet wheels 20 this annulus has recesses, not shown, formed at predetermined angular spacings from one another, in each of which there is inserted a spring device 28 which has a number of springs 30 connected together by sliding shoes 33 in a manner known from DE-A-41 28 868. Each spring device 28 abuts at one end against the annulus 24 and at the other end against the planet carriers 9, in each case through locating means, not shown. The spring constant of the spring device 28 is matched to a deformation torque corresponding to the input torque from the flywheel 1 multiplied by the gear ratio of the system 102.

The spring device 28 is arranged axially between the two planet carriers 9, which are connected together in a radially outer region, and to a flywheel 38 of the second flywheel 45. The planet carriers 9 form boundaries of the chamber 44 which is part of the flywheel 45, and contains the gear wheels 7, 20 and 24 as well as the spring device 28 and is at least partially filled with the viscous medium. Location of the gear wheels 20 and 24 in an axial direction is by the planet carrier 9. The flywheel 45 is able to receive a friction clutch or dog clutch (not shown).

The planetary gearing 102 acts as a gearing system 100 coupled back to the input transmission element 3, and the planet wheels 20 form a component 101 of the gearing system by which the direction of rotation of the annulus 24 is reversed in relation to that of the sun-wheel 7.

7 The torsional vibration damper operates as follows. Application of a torque to the input flywheel 1 produces angular movement. When using an internal combustion engine as the drive torsional vibrations are superimposed on the torque. Angular movement of the flywheel 1 is transmitted to the sun-wheel 7 which drives the planet wheels 20. The torque is transmitted through the planet wheels 20 to the planet carrier 9 and thus to the output transmission element 46 without any alteration in the direction of rotation, and the torsional vibration damper provides a predetermined reduction in the torsional vibrations which are applied together with the torque. In this arrangement, as the planet carrier 9 is initially secured against rotation by its inertia, the movement of the sunwheel 7 is also converted into a rotation of the planet wheel 20 about the respective needle roller bearings 18 and then into a movement of the bearings 18 themselves and thereby of the annulus 24 about the axis 54. The torque associated with the torsional vibration is divided into a first partial torque transmitted to the planet carriers 9 through the planet wheels 20 and into a second partial torque which is transmitted to the annulus 24 acting as the intermediate mass 50. If the torque associated with the torsional vibration rotates the sun-wheel 7 in a clockwise direction in Figure 1, then the rotation of the planet wheels 20 results in a first partial torque acting in an anti-clockwise direction to move the annulus 24 from its rest position in an anti- clockwise direction, whilst the planet carriers 9 are driven by a second partial torque acting in a clockwise direction. Both partial torques cause reaction torques comprising spring-. inertia-, and friction torques with different directions, which partially compensate for one another. This produces a relatively small deformation of the springs 30 in the spring device 28 (because of the chosen spring constant) and small relative rotations between the intermediate mass 50 and the output flywheel 45 and also between the input and output flywheels. Thus, the moment of inertia for the drive, in 8 comparison with a torsional vibration damper in which the individual masses are connected together less stiffly, is apparently increased, so that vibrations in smooth running of the drive are effectively reduced.

The planetary gearing 102 is constructed so that one part of the torque associated with a torsional vibration is applied to the annulus 24 and another part to the planet carrier 9 connected to the output transmission element 36. This is achieved where the gear ratio of the planetary gearing system is greater than one. The reverse action of the annulus 24 on the sun-wheel 7 and thereby on the input transmission element 32 is accordingly high.

The advantageous gear ratio of greater than one is achieved by the connection of the spring device 28. If the spring device were connected directly between the two transmission elements 3, 46 the annulus acting as intermediate mass 50 would be driven without conversion and so part of the advantage gained by the back-coupling of the gearing system 100 to the input transmission element 3 would be lost. The spring device 28 is therefore connected between the intermediate mass 50 and the output transmission element 46 so that the torque associated with a torsional vibration is converted only after transmission through the planet wheels 20, before it is transmitted to the intermediate mass 50 and the output transmission element 46.

This torque causes a movement of the planet carrier 9 relative to the annulus 24 so that the spring device 28 (which abuts against locating means on the annulus 24 and planet carriers 9) causes deformation of the springs 30 and consequently a movement of the sliding shoes 33 along their guide track. The amount of the deformation of the spring device 28 is dependent on the gear ratio of the planetary gearing 102, and in 9 particular on the relationship of the number of teeth of the sun-wheel 7 and annulus 24.

The viscous medium in the chamber 44 in the output flywheel 45 is squeezed on movement of the planet wheels 20 between sun-wheel 7 and annulus 24 and on deformation of the spring device 28. The viscous medium is urged axially outwards in the region of the teeth where two teeth mesh, and comes to the insides of the planet carriers 9. It is then pushed radially outwards because of the rotational movement of the torsional vibration damper. Deformation of the springs 30 and the consequent movement towards each other of the sliding shoes 33 also squeezes the viscous medium towards the insides of the planet carriers 9. On increasing angular velocity of the planet carriers 9 the speed of displacement of the viscous medium is also increased, both between the teeth and also in the region of the spring device 28. However the resistance which the medium offers to this displacement is also increased. The damping generated by the medium is therefore dependent on the corresponding angular velocity with which the planet carriers 9 are moved relative to the annulus 24.

Claims

A torsional vibration damper of the kind set forth, including a gearing system acting between the input transmission element and the output transmission element and dividing torque associated with a torsional vibration into partial torques, at least one of the input and output transmission elements being connected through the spring device to at least one element of the gearing system, the arrangement being such that on application of the torque associated with a torsional vibration, a corresponding differential torque formed from the sum of the partial torques deforms the spring device of which the spring constant is matched to a deformation torque corresponding to the input torque multiplied by the gear ratio of the gearing system.
2. A torsional vibration damper as claimed in claim 1, in which a flywheel is associated with each transmission element, and the gearing system element acts as an intermediate mass of which the direction of displacement from a rest position on application of a torque associated with a torsional vibration is reversed by at least one component of the gearing in opposition to the direction of the applied torque.
3. A torsional vibration damper as claimed in claim 2, in which the gearing system comprises a planetary gearing system having at least one planet wheel comprising the gearing component by which an annulus acting as the intermediate mass is rotated about the axis of the planetary gearing system in a direction opposite to the direction of rotation of the input transmission element.
4. A torsional vibration damper as claimed in any preceding claim, in which a gearing element which is not acting as an intermediate mass does 1 not move relative to the input or output transmission element while a gearing element comprising an intermediate mass by means of the spring device is adapted to move relative to the transmission elements.

1
5. A torsional vibration damper as claimed in claim 4, in which the intermediate mass is driven with respect to the input transmission element with a gear ratio by which the torque required for displacing the intermediate mass from its rest position is increased in comparison with a state without the gear ratio.
6. A torsional vibration damper as claimed in claim 5, in which the gear ratio is greater than one.
7. A torsional vibration damper of the kind set forth substantially as described herein with reference to and as illustrated in the accompanying drawings.

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