GB2210675A

GB2210675A - Torsional vibration damper with friction device dependent upon the transmitted torque

Info

Publication number: GB2210675A
Application number: GB8823164A
Authority: GB
Inventors: Andreas Foerster
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Sachs AG
Priority date: 1987-10-03
Filing date: 1988-10-03
Publication date: 1989-06-14
Also published as: GB8823164D0; FR2621371A1; DE3733544A1

Description

2210675 TORSIONAL VIBRATION DAMPER WITH FRICTION DEVICE 5EPENDENT UPON THE

TRANSMITTED TORQUE The invention relates to a torsional vibration damper, preferably for use in the transmission line of a motor vehicle. A known damper consists of an input part driven by the internal combustion engine, an output part mounted rotatably coaxially therewith, damper springs between the two parts in substantially tangential arrangement and at least one friction device the friction force of which is variable in dependence upon the transmitted torque and thus upon the amount of the relative rotation of the two parts against the force of the damper springs.

A torsional vibration damper of this construction is described for example in U.S. Patent Specification No. 1,861,251. In this known torsional vibration damper the tangentially arranged damper springs are loaded asymmetrically, so that on their loading a force component occurs in the direction of the axis of rotation of the torsional vibration damper. This force component is utilised to control an axial force loading of the friction device between the two hub parts. In this friction force control system in dependence upon the transmitted torque the asymmetric actuation of the springs is disadvantageous, leading to an additional stressing and significantly shortening the life of the springs. Furthermore the possibility of an effective attunement, that is an increase or a reduction of the axial force according to the installation case, is greatly restricted.

It is an object of the present invention to achieve a torque-dependent controlling of the friction force in a torsional vibration damper which possesses high operational reliability and is easily variable in a wide range.

According to the invention there is provided a torsional vibration damper for the transmission line of an internal combustion engine, comprising:an input damper part rotatable about a rotation axis, an output damper part rotatable about the rotation axis in relation to the input damper part; several damper springs coupling the damper parts together in a rotationally resilient manner; a friction device effective between the damper parts, the friction torque of which device is fixed by the spring force of at last one of the damper springs in dependence upon the relative rotation between the damper parts wherein the fricton device comprises at least one friction lever which is pivotably mounted with a first end on a first of the two damper parts and is connected with its second end through a first one of the damper springs with the second of the two damper parts and is in frictional abutment between its two ends on the second damper part while the friction lever and the first damper spring supported on it extend at least approximately in the circumferential direction, but have force transmission directions inclined in relation to one another.

By the arrangement of a rotatably mounted friction -I- lever and by its loading by a damper spring for the one part a controllable stressing is guaranteed for the damper spring, since the loaded lever changes its position in relation to the spring at most insubstant i ally, moreover due to the geometric arrangement and suspension of the friction lever an adaption of the achieved friction force to each utilisation case is possible to a great extent.

In this case it is readily possible to distribute several such friction levers on the circumference and to load them each by a spring.

Here the friction levers are preferably so arranged that, seen in the direction of rotation of the internal combustion engine, the friction levers are arranged in overrunning manner for the self -reinforcement of the friction force. Such an arrangement is especially advantageous since major fluctuations of moment can occur in the internal combusion engines of conventional style of construction, especially when the engine is under load. It is however also readily conceivable to install the friction levers pointing in the other direction, if the transmission line to be damped required such an arrangement. Likewise an alternating installation is conceivable.

According to a further feature of the invention the arrangement of such friction levers is effected preferably in fly-wheels having two inertia masses. Such two-mass flywheels are used to an increasing extent in internal combustion engines which deliver a high moment over very wide rotation rate ranges and therefore must especially well damp the vibration ranges which then have to be traversed.

Two-mass fly-wheels can here be equipped with two spring stages arranged in series, which are arranged radially one above the other, the radially outer being equipped in accordance with the invention with the friction faces.

Such an arrangement presents itself because in this case the accommodation of the friction faces raises no major constructional problems.

In this case the spring stage with the friction levers is fixed by end stops in such manner that compression of the springs is provided only in the pulling range. Such an arrangement brings firstly the desired highly progressive friction force rise in the case of traction loading of the internal combustion engine and for the other part a simple and secure return into the zero position, while due to the elimination of the mobility in the direction on the far side of the zero position a very simple mounting for the damper springs participating in the friction force generation is possible.

It is further proposed to load the friction lever additionally by a spring, in order to provide a torqueindependent basic load of the friction force. With such an additional spring an adaptation of the required friction force to the conditions existing in each case is easily possible to a very wide extent.

The invention will next be explained in greater detail by reference to an example of embodiment. Individually: - FIGURE 1 shows the elevation E - F from Figure 2 and FIGURE 2 shows the section A - B from Figure 1 of a two-mass fly-wheel with friction levers for torque-dependent friction force generation; FIGURE 3 shows a partial section C - D according to Figure 1 through a friction lever; FIGURE 4 shows the representation of principle of the action of the torsional vibration damper device corresponding to the two-mass fly-wheel of Figures 1 to 3.

Figure 1 shows the elevation E - F according to Figure 2, which reproduces the section A - B according to Figure 1. A two-mass fly-wheel is illustrated, consisting of a flywheel 1 which is firmly connected with the crank-shaft of an internal combustion engine (not shown), a fly-wheel 2 which transmits the torque delivered by the internal combustion engine further to a conventional clutch and/or a gearing and a torsional vibration damper arranged therebetween. All the parts here rotate about the common axis 3 of rotation. The fly-wheel 2 has an axially directed collar 9 in the region of its internal circumference, with which collar it is mounted. by means of a bearing 4, rotatably on the neck 5 of the fly-wheel 1. The bearing 4 is held axially on the flywheel 2 by a circlip 8 and on the neck 5 by a circlip 7 and a washer 6 secured by screws (not shown). The torsional vibration damper is arranged between the two f ly-wheels 1 and 2. It comprises two sets of damper springs 13 and 23, which are arranged radially one above the other. In Figure 1 only the windows 14 in the hub disc 12 for the damper springs 13 are represented. The hub disc 12 is connected fast in rotation but axially displaceably with the fly-wheel 2 through a toothing 10. 11. The hub disc 12 carries the windows 14 for the damper springs 13. On both sides of the hub disc 12 there are arranged cover plates 18 and 19 which likewise comprise windows for the damper springs 13. The two cover plates are firmly connected with one another radially outside the hub disc 12, with interposition of a hub ring 17. The connection takes place through rivets 20. The maximum possible angle of rotation between the cover plates 18 and 19 for the one part and the hub disc 12 for the other part, against the force of the torsion springs 13, is limited by a toothing 15, 16, which is provided between the external circumference of the hub disc 12 and the internal circumference of the hub ring 17. The hub ring 17 comprises a plurality of circumferentially distributed, radially outwardly protruding eyes 21 which are represented, as well as in Figure 1, in Figure 3 too according to the section C - D. In the region of these eyes 21 there is rotatably mounted in each case the one end of a friction lever 26, namely about the rotation axis 28. represented by a rivet 29. Starting in each case from an eye 21, each friction lever 26 extends contrarily of the direction of the arrow F according to Figure 11 approximately in the circumferential direction. and comprises at its other end a reception part for a damper spring 23. The other end of the damper spring 23, which is arranged likewise approximately in the circumferential direction, but with force transmission direction 23a extending with inclination in relation to the force transmission direction 26a of the friction lever 26, is supported on a spring holder 22, which is connected fast with the first fly-wheel through a fastening rivet 24. Each friction lever 26 comprises a friction lining 27 of cylinder segment form in the region between the rotation axis 28 and the end facing the torsion spring 23, which lining 27 rests on a cylindrical inner wall 25 of the fly-wheel 1. When the two-mass fly- wheel is in the unloaded position according to Figure 1, each eye 21 of the hub ring 17 lies on the spring holder 22, namely on the side opposite to the damper spring 23, forming an end stop 31. Furthermore in Figure 1 a spring 30 is arranged between the hub ring 17 and the friction lever 26 and if necessary can ensure a certain basic load in the friction device.

The function of the torsional vibration damper in the two-mass fly-wheel as represented is now as follows: - When the entire system is loaded with a torque by the internal combustion engine in pulling operation a torque is transmitted according to the arrow F from the fly-wheel 1 into the fly-wheel 2. Thus a relative rotation takes place according to the level of the torque between the two flywheels. This torque loads the damper springs 23 through the spring holders 22 and compresses them to a specific extent. In accordance with this compression the friction levers 26 are charged with a torque which effects an appropriate force rise between the friction lining 27 and the inner wall 25. In accordance with this force rise a corresponding friction force is built up between the two parts. The friction damping, which rises highly progressively in accordance with the torque to be transmitted, effectively damps the vibrations in the transmission line of the motor vehicle. the following advantages becoming effective: - 1. The friction force generation is highly progressive by reason of the self-reinforcing arrangement of the friction levers - andthus comes into action relatively softly, without the occurrence of abutment noises or similar negative effects; 2. the selected arrangement renders possible a satisfactory return into the rest position as represented according to Figure 1, since in the case of a relative movement contrarily of the arrow F, that is on transition from pulling into pushing operation or in the case of greatly reduced torque transmission - the friction force exerts a releasing effect upon the friction lever.

This satisfactory return is readily achieved when the moment generated by the spring is greater than the diminishing friction moment of the friction lever.

In order to f acilitate fine tuning if necessary, it is provided that an independent basic friction load is generated by the arrangement of the spring 30 in accordance with Figure 1.

In the present case the two spring systems 13 and 23 are arranged in series and are effective together in the - G - flat part of the spring characteristic curve, and after the toothing 15, 16 is in abutment only the radially outer damper springs 23 are effective still with the correspondingly progressive friction device.

The style of the torsion damper device as described by reference to the example of a two-mass fly-wheel can readily also be used in a normal clutch disc.

In Figure 4 the principle of construction of the twomass fly-wheel is again represented with its various components. The force introduction takes place through the fly-wheel 1 to the fly-wheel 2 and causes an approach of the two parts according to the magnitude of the applied torque. If one imagines the fly-wheel 2 as being held fast, the flywheel 1 moves, in accordance with the torque delivered by the internal combustion engine. in the direction of the arrow F towards the fly-wheel 2. In that movement firstly the damper springs 13 are compressed, as far as permitted by the toothing 15, 16. After this angle of rotation is used up, the damper springs 23 are compressed and according to their compression a progressive friction force is generated by the friction levers 26 in relation to the fly-wheel 1. In operation of the internal combustion engine without load the basic position as represented in Figure 1 and Figure 4 will have been reached and in pushing operation drive of the internal combustion engine by the vehicle the flywheel 1 will move away from the fly-wheel 2 contrarily of the direction of the arrow F. In this case the stop 31 becomes effective and the stage with the damper springs 23 and the friction levers 26 becomes ineffective. Such an . LO W embodiment is relatively simple in assembly and in pushing operation the progressive friction effect is not absolutely necessary. It is however readily conceivable to make the arrangement with -the damper springs 23 and the friction levers 26 symmetrical for both directions of rotation, so that a progressive friction generation becomes effective even in pushing operation.

2

Claims

1. Torsional vibration damper for the transmission line of an internal combustion engine, comprising:an input damper part rotatable about a rotation axis, an output damper part rotatable about the rotation axis in relation to the input damper part; several damper springs coupling the damper parts together in a rotationally resilient manner; a friction device effective between the damper parts, the friction torque of which device is fixed by the spring force of at last one of the damper springs in dependence upon the relative rotation between the damper parts; wherein the friction device comprises at least one friction lever which is pivotably mounted with a first end on a first of the two damper parts and is connected with its second end through a first one of the damper springs with the second of the two damper parts and is in frictional abutment between its two ends on the second damper part, while the friction lever and the first damper spring supported on it extend at least approximately in the circumferential direction, but have force transmission directions inclined in relation to one another.

2. Torsional vibration damper according to Claim 1, wherein the friction lever is mounted on the first damper part for pivotable movement about a pivot axis parallel to the rotation axis and abuts with a friction face of cylindrical segmental form on a cylindrical inner face of the second damper part.

- 1.2 -

3. Torsional vibration damper according to Claim 1 or 2, wherein the angle of the direction of force transmission of the friction lever to'its frictional abutment face is selected so that a friction moment self-reinforcement effect results in one of the relative directions of rotation of the damper parts.

4. Torsional vibration damper according to one of Claims 1 to 3, wherein a plurality of friction levers is provided and a third damper part is provided which is rotatable about the rotation axis in relation to the first and second damper parts, which are rotationally elastically coupled with one another through a first set of the damper springs, and the third damper part is rotationally resiliently coupled with the first or the second damper part through a second set of the damper springs in series with the first set of damper springs, and the first damper springs are arranged radially above the second damper springs and each friction lever being connected with one of the first set of damper springs.

5. Torsional vibration damper according to Claim 4, wherein mutually associated end stops are provided on the first and second damper parts, which stops limit the relative movement of the first and second damper parts in the direction of relief of stress of the first set of damper springs and relief of the friction levers.

6. Torsional vibration damper according to Claim 5, characterised in that each friction lever is so arranged that on a relative rotation, caused by traction loading by the internal combustion engine, between the first and second damper parts, the compression of the first set of damper springs is increased.

7. Torsional vibration damper according to one of Claims 4 to 6, wherein the friction -levers are distributed in the circumferential direction.

8. Torsional vibration damper according to one of Claims 1 to 7, wherein one or more additional springs are provided to stress initially the or each friction lever into frictional abutment on the second damper part, for the generation of a torque-independent basic friction moment.

9. Torsional vibration damper according to one of Claims 1 to 8, and arranged in the drive path between two flywheel masses of a two-mass flywheel.

Published 1988 at The Patent Office. State House- 66.71 HIL1h 14nlbnrn Lnndem WC1R 4TP. purther copies MAY be Obtained from The Patent "'-cl