GB2156477A

GB2156477A - Torsional vibration damper with variable effect

Info

Publication number: GB2156477A
Application number: GB08507879A
Authority: GB
Inventors: Gerhard Tebbe
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1984-03-27
Filing date: 1985-03-26
Publication date: 1985-10-09
Also published as: DE3411221A1; GB2156477B; DE3411221C2; GB8507879D0; FR2562190A1

Abstract

A torsional vibration damper in the drive line of a motor vehicle with internal combustion engine comprises a mass 2 which is resiliently coupled to the drive line 16 through a lever arm r which is variable in dependence upon rotation rate by means of centrifugal weights 11. The natural frequency of the damper is therefore varied in a specified rotation rate range. The mass 2 may be connected to the centrifugal weights 11 and therefore to the hub 1 by rubber springs (9) instead of coil springs. <IMAGE>

Description

SPECIFICATION Annuller for damping torsional vibrations The invention relates to an annuller for damping torsional vibrations, especially in the drive line of motor vehicles with internal combustion engines, consisting inter alia of an annuller mass which is coupled by way of an elastic connection to the drive line.

It is already known from German Publication Specification 2,903,715 to couple to the fly-wheel of an internal combustion engine crank-shaft an annuller which is connected with the fly-wheel through an elastomer layer.

The disadvantage of such annullers is to be seen in that the natural frequency to the range of which the vibration-annulling effect is limited is fixed by the inertia moment and torsion spring constant. Damping does not occur at a relatively great difference from this annuller natural frequency, and in addition new natural frequencies arise.

It is the problem of the present invention to produce an annuller for damping torsional vibrations the effect of which extends to the largest possible rotation rate range, and which does not display the disadvantages of the prior art.

This problem is solved in accordance with the invention by the characteristic of the Main Claim. Due to the rotation-rate-dependent variation of the natural frequency of the annuller it becomes possible to reduce the overall vibration level within a substantially larger rotation rate range, without the occurrence of new natural frequencies.

In accordance with Claim 2 it is especially advantageous to effect the coupling of the annuller mass to the drive line preferably by way of at least one centrifugal-force-depen- dently variable lever arm. Due to this variation of the lever arm the product of lever arm and spring constant varies and thus so does the torsion spring constant which determines the natural frequency of the annuller. Thus despite constant spring constant and constant mass, the natural frequency of the annuller can be varied in dependence upon rotation rate.

In accordance with the invention the variation of the lever arm is carried out by the coupling of the annuller mass through at least one centrifugal weight which varies the distance from the axis of rotation in dependence upon rotation rate. In this case in accordance with the invention the annuller mass can be rotatably mounted but axially fixed on the hub.

Further advantageous forms of embodiment are laid down in the Sub-Claims.

The invention will next be explained in greater detail by reference to several examples of embodiment.

Individually: Figures 1 and 2 show an elevation of and a longitudinal section through an annuller with radially displaceable centrifugal weights; Figure 3 shows an elevation of an annuller in which rubber-elastic spring elements constitute both the return force for the centrifugal weights and the coupling between centrifugal weights and annuller mass; Figures 4 and 5 show an elevation of and a longitudinal section through an annuller having two different annuller masses, which are coupled with the hub through a centrifugal weight system; Figure 6 shows an elevation of an annuller with tension springs which effect both the return of the centrifugal weights and the coupling of the annuller mass;; Figures 7 to 9 show an example of embodiment of an annuller with an elevation and two sections, in which, in each case, compression springs connected in series effect both the return of the centrifugal weights and the coupling of the annuller mass; Figures 10 to 12 show a variant of an example of embodiment with modified force transmission between hub and annuller masses; Figure 13 shows the principle of the course of the curve of the angular acceleration X over the rotation rate, with comparison of two different annullers with an embodiment without annuller.

Fig. 1 shows the elevation and Fig. 2 shows the section ll-ll according to Fig. 1 of an annuller which in dependence upon rotation rate varies the lever arm between a rotating shaft and an annuller mass. The hub 1 is arranged fast in rotation on a shaft (not shown). This shaft, which is preferably the gear input shaft, rotates about the rotation axis 16. The hub 1 carries two guide arms 6 pointing diametrically in relation to one another and radially outwards, which serve for the guidance of a centrifugal weight 11 each.

In the two Figures the one centrifugal weight 11 is represented in its radially inner position and the other centrifugal weight 11 in its radially outer position. For the one part the hub 1 and for the other a stop 1 2 on each guide arm 6 serve as travel limitation for the two extreme positions. The two centrifugal weights 11 are connected with one another by two return springs 8 in a manner in which these return springs 8 hold the two centrifugal weights 11 in their position close to the hub below a fixed rotation rate, while above this rotation rate the centrifugal weights 11 slide outwards against the force of the return springs 8.The annuller mass 2 arranged concentrically with the rotation axis 1 6 is mounted rotatably on the hub 1 and is connected with each of the two centrifugal weights 11 through two helical springs 7 in each case. Thus these helical springs 7 constitute the coupling between the hub 1 and the annuller mass 2. In the upper halves of the two Figures a unit lever arm of r1 results from the geometry of the centrifugal weights and the arrangement of the helical springs 7, while when the centrifugal weights are in the driven-out position according to the lower halves of the Figures the effective lever arm at r2 is considerably greater.Since now the natural frequency of such an annuller is dependent firstly upon the annuller mass and also upon the torsion spring constant, and in the present case the torsion spring constant is to be regarded as the product of lever arm and spring constant, the natural frequency is varied in dependence upon rotation rate by variation of the lever arm in dependence upon the rotation rate while retaining a constant spring constant and a constant annuller mass.

The effect of this rotation-rate-dependent variation of natural frequency upon the vibration behaviour in the drive line of an internal combustion engine is represented in principle in Fig. 1 3. It should be mentioned at this point that the curve courses according to Fig.

1 3 are valid in principle for all forms of embodiment according to Figs. 1 to 1 2. In Fig. 1 3 the angular acceleration X is represented in dependence upon the rotation rate for example of the gear input shaft. The curve B with the maximum peak value of the angular acceleration and with the most distinct curve form represents the vibration behaviour of a gear input shaft without annuller. It can be seen that very high angular accelerations occur over a large rotation rate range. When an annuller with a fixed natural frequency is used, the curve A for example occurs. This has, compared with the curve B, a distinctly lower peak value of the angular acceleration, while moreover the maximum in this curve occurs at a lower rotation rate.It can further be seen that the curve A displays a rise again at higher rotation rate, which however shows lower values of the angular acceleration. It is unfavourable in this curve A that it displays its maximum approximately in the region of the idling rotation rate of the internal combustion engine. Finally the curve C shows a course of the angular acceleration in dependence upon the rotation rate in the case of an annuller the natural frequency of which is variable in dependence upon rotation rate. It can be seen clearly that over the entire rotation rate range the angular acceleration values result as substantially lower than in the curves A and B, and that the curve course is made substantially flatter in the region of its maximum.

Fig. 3 shows the view of an annuller with retracted centrifugal weights 11, in which the connection between the centrifugal weights 11 and the annuller mass 2 takes place through spring elements 9 which are produced for example from rubber mouldings.

These spring elements 9 are secured, for example vulcanised, for the one part to the annuller mass, and for the other part to the centrifugal weights 11. Due to their somewhat C-shaped configuration and due to the provision of an initial stress force it is possible in the case of this embodiment to obtain through these spring elements 9 both the return force for the centrifugal weights 11 and the cou pling of the annuller mass 2 to the hub 1 and the guide arms 6. Thus a quite especially simple form of constructions is achieved.

Figs. 4 and 5 show the section IV-IV and the section V-V respectively through an annuller in which two annuller masses 2 and 3 are arranged side by side on one common hub 1. The two annuller masses 2 and 3 are coupled to the hub 1 through a system of centrifugal weights 1 3 and a system of helical springs 7, the centrifugal weights 1 3 being mounted pivotably by means of pivot points 14 on hub arms 5. In Fig. 4 the centrifugal weight represented above is reproduced in its retracted position and the centrifugal weight represented below is reproduced in its extended position.The two centrifugal weights are connected with one another through return springs 8 and the return springs control the outward pivoting in conformity with the mass of the centrifugal weights 1 3. The helical springs 7 ensure in each case the binding of the annuller masses 2 and 3 to the centrifugal weights 1 3. In this case the lever arm r is realised when the centrifugal weights 1 3 are in the retracted condition, while the two different lever arms r2' and r2" are achieved when they are in the extended condition.

As regards function no differences in principle occur compared with the embodiments in Figs. 1 to 3. However due to the arrangement of two different masses it is possible to annul two different frequencies at the same time.

The attunement can here for example be adapted to the ignition frequency and twice the ignition frequency. The embodiment according to Figs. 4 and 5 differs from the embodiments according to Figs. 1 to 3 essentially in that the centrifugal weights are arranged pivotably about a pivot point which is arranged on a hub arm, the hub arm being connected fast in rotation with the hub. In order to keep the pivot angle of the centrifugal weights small, it is advantageous to place the pivot point 14 as far as possible to the exterior.

In Fig. 6 there is reproduced the lateral elevation of an annuller which corresponds in principle to the one half of Fig. 4. By appropriate arrangement of the helical springs 7 success has been achieved here in both using these helical springs 7 as return springs for the centrifugal weights 1 3 and at the same time effecting the binding of the annuller mass 2 to the hub 1. This is rendered possible by the fact that the helical springs 7 as a result of their initial stress exert, in every position of the centrifugal weights 13, a force component upon the centrifugal weights which is directed contrarily to the centrifugal force. In this case a lever arm of magnitude r, results in the retracted condition and two different lever arms of magnitude r2' and r2" respectively result in the extended condition.

In Figs. 1 to 6 as described hitherto it is naturally also possible in place of the helical springs subjected to tension stress to provide flexure springs which at least take over the binding of the annuller mass to the hub.

Furthermore it can be advantageous, in order to avoid vibrations of the centrifugal weights, to provide damping elements which can be formed as purely mechanical friction damping or equally as hydraulic damping.

In Figs. 7 to 9 there is represented an example of embodiment of an annuller in which, as essential difference from the examples of embodiment as described above, the binding of the annuller mass to the hub and the return force for the centrifugal weights consist of a spring system in which two compression springs are arranged one behind the other. Fig. 7 shows the section VII-VII according to Fig. 8. Fig. 8 represents a section VIII-VIII according to Fig. 7 and Fig. 9 a section IX-IX likewise according to Fig. 7. In the present case the annuller mass 2 is divided into two parts and the two parts are mounted rotatably on the hub 1 with axial spacing from one another. The usual components of the annuller are arranged within the two parts of the annuller mass 2.The hub 1 is mounted fast in rotation for example on a gear input shaft (not shown) which rotates about the axis 1 6 of rotation. The two parts of the annuller mass 2 are for their part mounted rotatably on the hub 1 and firmly connected with one another. Two symmetrically arranged lever arms 5, which are firmly connected with the hub 1, extend between the two parts of the annuller mass 2. In the radially outer region of each of the hub arms 5 there is arranged a joint 30 to each of which a stirrup piece 28 is pivotably mounted. It should be mentioned at this point that in Fig. 7 only one of the centrifugal weights and spring sets is represented, the other having been omitted for the sake of simplicity; the centrifugal weight 1 3 is formed by the housing 17, the guide pin 18 and the springs 13.The stirrup piece 28 is made in somewhat U-form and extends to both sides of the hub arm 5 close to the inner sides of the two parts of the annuller mass 2. At its end opposite to the joint it engages in the eye 29 of a guide pin 18. This guide pin 18 is provided, approximately in the middle of its longitudinal extent, with a collar 1 9 on which two helical compression springs 1 5 are supported which each surround the guide pin 1 8. The two springs 1 5 and the guide pin 1 8 are surrounded by a housing 1 7 which is penetrated at its diametrical ends by the guide pin 1 8 in appropriate openings 24 and 25.The one of the two compression-stressed springs 1 5 is here supported in the interior of the housing 1 7 and the other by means of a dished spring 21 which on the one hand is penetrated by the guide pin 1 8 and on the other hand, with laterally protruding tabs, penetrates windows 26 in the two parts of the annuller mass and rests, due to the spring initial stress of the helical compression springs 15, on a rolling cam face 20 in the window 26. Furthermore the housing 1 7 is mounted pivotably about a pivot point 22 in the region of the rolling cam face 20. This pivot point, considered from the rolling cam face 20, lies in the direction of the hub 1.Due to the arrangement of this pivot point 22 in combination with the rolling cam face 20, the helical compression springs 1 5 exert a moment upon the housing 1 7 which seeks, against the centrifugal force, to pivot the housing 1 7 together with the stirrup piece 28 in the direction towards the hub 1. The housing 1 7 is produced for example from a sheet metal strip, made open laterally in relation to the two parts of the annuller mass 2 and shaped in the region of its pivot point 22 into a bearing position through which a pin 23 extends which is held in the two parts of the annuller mass 2.Thus the centrifugal weight designated generally by 1 3 consists of the housing 17, the guide pin 18, the two helical compression springs 1 5 and a proportion of the stirrup piece 28. A stop 27 is provided on the annuller mass 2 to limit the outward movement of the centrifugal weights 13.

Operation is as follows:- The drive of the annuller takes place through the hub 1 and the hub arms 5. These transmit the torque by way of the stirrup piece 28 to the guide pin 18. The guide pin 18 is held in a middle position by the two helical compression springs 1 5 by means of its collar 19. The one spring bears through the spring dish 21 on the rolling cam face 20 of the annuller mass and the other spring bears through the housing 1 7 and the pivot point 22 upon the pin 23 and thus likewise upon the annuller mass 2. The initial spring stress of the helical compression springs 1 5 in combination with the rolling cam face 20 effects a moment upon the housing 1 7 which is directed about the pivot point 22 in the direction towards the hub 1. The centrifugal force acts against this moment upon the parts of the centrifugal weight 1 3 and in accordance with the attunement of the mass of the centrifugal weight 1 3 and the initial spring stress of the helical compression springs 1 5 the centrifugal weights begin, as from a specific rotation rate, to lift away from the hub 1 and to apply themselves to the stops 27 at a specific rotation rate. During the outward movement of the centrifugal weights 1 3 the lever arm between the axis 1 6 of rotation and the line of action of the helical compression springs 1 5 varies. Thus the natural frequency of the annuller also varies.In this case in an advantageous manner the helical compression springs 1 5 are used both for the generation of the return force for the centrifugal weights and for the binding of the annuller mass 2 to the lever arms 5.

In Figs. 10 to 1 2 there is reproduced a variant of an annuller the differences of which from the embodiment according to Figs. 7 to 9 consist merely in that the articulation of the guide pin 1 8 to the hub arms 5 takes place directly in a slot 31. In this case the guide pin 18 engages with a peg 32 in the slot 31 of the hub arm 5, in order to be able to vary its position in relation to the rotation axis 1 6 during the pivoting movement of the centrifugal weight 1 3 without interruption of the torque connection to the hub 1. The remainder of the construction corresponds both in formation and in effect to the annuller according to Figs. 7 to 9. Thus a more detailed explanation of the manner of operation becomes superfluous.

Fig. 1 3 has already been explained in further detail in connection with Figs. 1 and 2.

Therefore the principle of the present invention is to be discussed again briefly at this point. The natural frequency of the annuller is dependent upon its mass and the torsion spring constant with which this mass is coupled to the rotating component. Since the mass can hardly be varied during operation, it is proposed to vary the torsion spring constant by varying the lever arm by centrifugal force in dependence upon rotation rate. Thus the variation of the natural frequency of the annuller occurs, with the result that the angular accelerations occurring on the shaft are markedly reduced over a large rotation rate range and the course of the curve displays considerably smaller differences between maximum and minimum.

Claims

1. Annuller for damping torsional vibrations, especially in the drive line of motor vehicles with internal combustion engines, consisting inter alia of an annuller mass which is coupled through an elastic connection to the drive line, characterised in that the natural frequency of the annuller is variable in dependence upon rotation rate.

2. Annuller according to Claim 1, characterised in that the coupling of the annuller mass (2, 3) to the drive line (4) takes place preferably by way of at least one lever arm (rut, r2, r2', r2") variable in dependence upon centrifugal force.

3. Annuller according to Claims 1 and 2, characterised in that the variation of the lever arm (r, r2, r2', r2") is effected by the coupling of the annuller mass (2, 3) through at least one centrifugal weight (11, 1 3) which varies the distance from the axis (16) of rotation in dependence upon rotation rate.

4. Annuller according to Claims 1 to 3, characterised in that spring elements (7, 9, 15) are arranged between lever arm and annuller mass (2, 3).

5. Annuller according to Claims 1 to 4, characterised in that the annuller mass (2, 3) is mounted rotatably but axially fixedly on the hub (1).

6. Annuller according to Claims 1 to 5, characterised in that the spring elements (7, 1 5) are preferably formed as helical springs.

7. Annulier according to Claims 1 to 6, characterised in that the centrifugal weights (13) are rotatably mounted on lever arms (5) with spacing from the axis (16) of rotation of the annuller.

8. Annuller according to Claims 1 to 6, characterised in that the centrifugal weights (11) are arranged displaceably on substantially radially extending guide arms (6).

9. Annuller according to Claims 1 to 8, characterised in that preferably two like centrifugal weights (11, 13) in each case with oppositely directed movement are arranged.

1 0. Annuller according to Claims 1 to 9, characterised in that each centrifugal weight (11, 13) is connected with the annulier mass (2, 3) through preferably two approximately oppositely arranged springs (7, 1 5).

11. Annuller according to Claims 1 to 10, characterised in that the springs (7, 15) for coupling the annuller mass (2, 3) to the drive line (1) are formed at the same time as return springs for the centrifugal weights.

1 2. Annuller according to Claims 1 to 11, characterised in that the centrifugal weights (13) are formed by the springs (15) and the spring guide elements (1 7, 18).

1 3. Annuller according to Claims 1 to 12, characterised in that the springs are made as helical compression springs (1 5) and installed in each case by pairs in a housing (17) one behind the other with initial stress and the force introduction takes place from the hub (1) by way of a guide pin (18) which extends concentrically within the springs (1 5), with a collar (19) on which one of the springs (1 5) bears from each side.

1 4. Annuller according to Claims 1 to 13, characterised in that the force introduction takes place from the annuller mass (2) by way of a rolling cam face (20) on which the one of the two springs (1 5) is supported through its free end and a spring dish (21).

1 5. Annuller according to Claims 1 to 14, characterised in that the supporting of the free end of the other spring (15) takes place through the housing (1 7) which surrounds both springs (15) and is pivotably mounted in the region of one of its ends by a pivot point (22) on the annuller mass (2).

1 6. Annuller according to Claims 1 to 15, characterised in that the guide pin (18) is axially displaceably mounted in the housing (17) and penetrates with both ends through corresponding openings (24, 25) of the housing (17).

1 7. Annuller according to Claims 1 to 16, characterised in that the force introduction from the hub (1) to the guide pin (18) takes place through a stirrup piece (28) which is rotatably mounted on the one hand pivotably (joint 30) on the hub arm (5) and on the other hand pivotably (eye 29) on the end of the guide pin (18) opposite to the pivot point (22) of the housing (17).

1 8. Annuller according to Claims 1 to 16, characterised in that the force introduction from the hub (1) to the guide pin (18) takes place through a slot (31) which is arranged in the hub arm (5) and in which the end of the guide pin (18) opposite to the pivot point (22) of the housing (17) engages by means of a peg (32).

19. Annuller according to Claims 1 to 18, characterised in that two different annuller masses (2, 3) for the annulment of different frequencies can be coupled at the same time through a centrifugal weight system (13).

20. Annuller for damping torsional vibrations as claimed in Claim 1, substantially as described herein with reference to and as illustrated by any one of the examples shown in the accompanying drawings.