GB2332938A

GB2332938A - Torsional vibration damper

Info

Publication number: GB2332938A
Application number: GB9822339A
Authority: GB
Inventors: Bernd Peinemann
Original assignee: Mannesmann Sachs AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1997-10-14
Filing date: 1998-10-13
Publication date: 1999-07-07
Anticipated expiration: 2018-10-13
Also published as: GB9822339D0; GB2332938B; DE19745382B4; DE19745382A1; FR2769676A1; ES2190823A1; FR2769676B1; ES2190823B1

Abstract

A torsional vibration damper 10 comprises a hub 12 acting as a torque input element 12 and a pair of cover discs 22, 24 acting as an output element 20. A damping spring arrangement 36 with damping spring units 38 acts between the input and output elements. Each damping spring unit 38 comprises two or three damping springs 42, (44, 46, Fig. 2) between which is arranged an intermediate element 48, 50 which is displaceable with respect to the input element 12 and the output element 20. A first friction device 62 acts between the input element 12 and the output element 20 and a second friction device 60, 64 acts between the at least one intermediate element 50 and the input element 12 and/or the output element 20. At least one of the first and second friction devices is so designed that it generates a frictional force essentially only when a relative rotational angle between the input element 12 and the output element 20 exceeds a limit angle α G (in the range 2 - 5 degrees).

Description

1 Torsional vibration darnper 2332938 The present invention relates to a

torsional vibration damper.

A torsional vibration damper is known from DE -1-95 10 833 Al.

This document shows a clutch disc in which an input part and an output part are peripherally rotatable with respect to one another with interposition of three damping spring units. This damping spring unit comprises two springs which are connected in series and rest at their mutually adjacent ends on respective control edges of an intermediate ring. The -intermediate ring has a reaion With control edaes for the resiDective damoina springs for each of the damping spring units and is freely rotatable with respect to both the input part and the output part. A friction device which acts directly between the input part and the OUtLIDUt part is proposed for generating an adequate damping force.

A torsional vibration damper in which the damping spring units comprise two pairs of damping springs connected in series is also known from DE 35 27 458 Al. In this torsional vibration damper the two pairs of each of the damping spring units are connected in parallel with one another, so that a first spring pair of damping springs connected in series initially acts in a first torque transmission range and, when this first pair has reached its maximum range of action, the second spring pair of springs connected in series is active. In the range of action of the second pair, the respective damping springs rest with their mutually adjacent ends on an intermediate ring element formed from two individual intermediate ring parts. With this torsional vibration damper, a respective friction device is provided in the region of all components of input part, output oart and intermediate ring oartS which are rotatable with respect to one another, so each relative rotational movement 2 occurring takes place while overcoming a corresponding f--ictional moment.

An im)ortant asnect of torsional vibration dampers is that, owing to the damping springs and the friction devices adeauate uncoupling between input and output side is provided, i.e.

torsional vibrations occurring on one side are as far as possible not transmitLed to the oLher side but are dissipaLed in the torsional vibration damper. However, it should be remembered that, depending on the load state and on the operating state, for example the speed of an internal-combusEion enerIne, cruite different torsional vibration excitation occurs which demands appropriately adapted damping properties in the region of the torsional vibration damper. it is known for this purpose to use damping springs with differeni 1 t Spring constants SO the springs With a 'Lower spring constant act fIrst and the springs with a greater spring constant are compressed when a certain torque limit is exceeded. This is known, for example, frOM. the abbovedesCribed DE 35 27 458 Al.

An object of the nresent invention is tO provide a torsional vibration damper which is compact but has improved vibration damping behaviour.

According to the invention there is provided a torsional vibration damDer, in iDarticular for arrangement in -the p'ower train of a motor vehicle, comprising an input element, an out-put element which is rotatable relative to the input element around an axis of rotation, a damping spring arrangement which is arrancred in terms of action between the input el-ement and the output element and counteracts a relative rotation between input e 1 ement and Our-pu'I e I ement, wherein the dairrping spr ii ng arrangement comprises a71 least one damping spring unit with at least two damoina sorinas which are connected -1-n series in zerms of action; which damping spring unit loads one element or input 1 3 element and output element in the event of a relative rotation between input element and output element and as a function of a relative direction of rotation of input element and output element at a first damping spring unit end and loads the other element of input element and output element at a second damping sprina unit end, an intermediate element between each two damping springs of the at least one damping spring unit on which the damping springs are supported with their mutually facing ends, the intermediate element being displaceable with respect LO the inpUt element and the OUCOUt element in the event of a relative rotation between input element and output element, a first friction device which acts to generate a frictional force between input element and output element or components associated with them and a second friction device which acts between at least one intermediate element provided in each damping spring unit and the input element and/or the output element or components associated therewith in each case for generating a friCtional force, wherein at least one friction device of first and second friction device is designed to generate a frictional force essentially only when the relative rotational angle between input element and output element is greater -than a predetermined limit angle on the basis of a basic relative rotational angle.

With the torsional vibration damper constructed in accordance with the invention, the damping behaviour can be optimally adaDted to the torsional vibrations occurrincr or exiDected various load states. If relatively low torques are to be transmitted, for example in a low load state, the damping of torsional vibrations is not necessary or is necessary on-ly to a relatively limited extent as the occurrence of greater torsional vibrations is not expected in this load range. However, if a specific load range is exceeded, which is manifested by the attainment o-J" The limit angle of the relative rotation between input part and OU-LQUt part, there is a risk that torsiona'L 4 vibrations then occurring can lead to undesirable behaviour and, in the worst case, can even damage components of the power train. However, as at additional friction device is active in tl,-,.is state torsional vibration damiDer as defined, these vibrations can be adequately attenuated so the damping can be improved over all the speed or load ranges.

vibration individual least one with the torsional behaviour it is pointed out that a frictional force acting between two components should be interpreted as the force generated by the corresponding friction device and counteracting a rotation of the components.

it is pointed out that the term "element" as used here describes not onLy individual components but also assembly units or modules consisting of several parts.

The damper may be constructed such that the first friction device produces a frictional force only when the relative rotational anal-e between the inDut element and outDu-L element is greater than the limit angle. This is particularly advantageous if the second friction device generates a frictional force with all relative rotational angles between the input element and the o-,.jtDut element. With an arrangement Of this type, L-he second device acts permanently and generates a frictional force which can be described, for example, as basic friction in the case of all relative rotational angles. This basic friction is then suiDerimposed on a frictional- Lorce which is deDendent on the rotational angle and is provided by the first friction device so weaker damping can be provided in the case of relatively small rotational angles whereas a greater discharge of energy is crenerated bv connecting a frLC-L-i-on device if greater critical relative rotational angles are achieved.

With the torsional vibration damper constructed in accordance with the invention, moreover, the second friction device can provide a first friction device range which generates a frictional force which is substantially independent of the relative rotational angle between the input element and the output element. It is also advantageous if the second friction device iDrovides a second friction device ranae which Droduces a variable frictional force as rotational angle between the element.

a function of the relative input element and the output With a particularly advantageous develolDment of the aforedescribed torsional vibration damper, the second friction device range can generate a frictional force between the intermediate element and one of the input element and the output element, preferably the output element, when the relative rotational angle between the input element and the output element is smaller than or equal to a predetermined switch angle, preferably the limit angle, and can generate a frictional a force between the intermediate element and the other res)ective element of the input element and the output element, preferably the input element when the relative rotational angle between input element and our-put element is greater than the switch angle.

consisting it is frequently desired with torsional vibration dampers to carry out damping according to whether a driving I for example, of an internal-combustion co='Led to the torsional vibration damiDer conjunct-ion with a motor vehicle friction clutch and drive shaft, operates in the pulling state, i.e. driving stal.:e, or in the pushing state, i.e. engine braking state. This is due to the fact that different torsionaL vibration states can be generated if the load is applied to the torsiona damper from various directions of introduction.

s,7stem engine Jb1v in - Doss L L_ 1 vibration To enable a 6 vibration damping characteristic to be provided as torque introduction, the at least one damping preferably comDrises at least three damping respective intermediate element a function of spring unit springs, a for supporting the damping springs being provided between the mutually acing ends of directly adjacent damping springs in each case in this case the second friction device does not act on at 'Least one of the intermediate ellements. This effect is even more noticeable if the three damping springs have different spring characteristics.

The first friction devce can comprise, for example, a first friction element which acts With friction on one of the iniDut element and the output element and is essentially freely rotatable to the limit- angle with respect to the other of the input element and the output element on the basis of the basic relative rotational angle between the input element and the output element. After the limit angle is exceeded, the friction element can be rotated with the other of the input element and the output element whi-"e generating a frictional force on the one element.

it is advantageous if the second friction device comprises a second friction element which is preferably rigidly connected to -he inter-mediate element and which the -J,-.+.e---med-Ja±e element acts frictionalIv on the other element Of the innut element and the output element and a third friction element which is arranged in terms of action between the intermediate element and ±-he friction element.

1 frictiona' efficiency can be obtained J the Particularly hIgh L - - -L.1 L. A- - -L -L 1_ r h i. e-iement is fixed on the d fric-tinn int... ediate element and acts frictionally on the first friction element.

A simple construction wir-h relatively rew components can be the third frictLon element is a biasiner sz)rincr ob ta ined L L 7 element which is supported on the first friction element and biases the intermediate element onto the other of the input element and the OUtl)Ut element.

A particularly advantageous constructional development of the torsional vibration damper in accordance with the invention can be produced if one of the input element and the output element com)rises a central disc part and the other element of the inout element and the output element comprises a first cover disc arranged on a first axial side of the central disc Part and a second cover disc which is arranged on a second axial side of Lhe central disc part and is rigidly connected tO the first cover disc. Both the central disc part and the first and the second cover discs then have, in the region of the two dam-ping spring unit ends of the at least one damping spring unit in each case, control reaions to be loaded bv the associated damoing spring unit end of the at least one damping spring unit.

With a development of this type which is simple to construct, the central disc part preferably forms the other element of the input element and the output element and the first and the second cover discs together form the one element of the input element and the output element.

The delayed action of one friction device which does not act until the 'Limit angle is exceeded can be obtained, for example, in that- the first friction element acts on a part of first and second cover discs and is pressed by at least one biasing spring e'lement onto the part. The biasing spring element is supported on another part of the first and second cover discs and/or on the Jnrermediiate element.

The abillity to connect and disconnect one friction device depends on the load state in which the torsional vibration damner in accordance with the invention is o)eratina. in other f 8 words, the basic relative rotational angle can be defined such that the basic relative rotational angle between the in-out element and the output element is a neutral rotational angle which defines a neutral relative rotational position between the input element and the output element if substantially no torque is to be transmit-Led. The limit rotationaI anale is then to be measured on the basis of the neutral relative rotational angle defining the neutral relative rotational position. The basic relative rotational angle can additionally also be defined such Lhat the basic re'Lative rotationaI angle is a re'Lative rotational angle between the input element and the output element which is adjusted with a torque which is to be transmitted such that the limit angle is to be measured on the basis of the relative rotationa'i ang'Le adjusted during transmission of the specific torque.

Lt can therefore be seen thaL, on uhe basis of a relative rotational angle in a certain range of variation adjusted as a C function of the 'Load state, the friction device which can be connected does not yet act and is only connected when the range of variation becomes greater than the limit angle by the adjusted angle - measured from the adjusted angle - in order to increase the frictional work. This therefore app'Lj'-es tO the case where the angle adjusted defines a neutral relative rotational state in which no or substantially no load is transmitted via the torsional vibration damner and to L-he case where the re'Lative rotational angle defines a position deviating from the neutral position.

The invention may be understood more -readily and various other aspec---s and features of the invention may become apparent from J dera L.L L - -L -L cons - on o' -Ihe fo'L'Low-nc descrinton.

9 Embodiments of the present invention will now be described in detail hereinafter, by way of examples only, with reference to the accompanying drawings. In the drawings:

Figure 1 is a partial longitudinal section through a torsional vibration damper constructed in accordance with the invention and designed as a dual mass flywheel; Figure 2- is a part-sectional end view of the damn-ing spring arrangement of the torsional vibration damper in Figure 1 showing the pulling mode; Figure 3 is a graph showing the relative rotational angle of an Ln- LerirLediate element with resoect to other comoonents of the torsional vibration damper as a function of the rotational angle between input and output elements and Figure 4 is a schematic representation of the operation of the friction devices actLng in the torsional vibration damper in both pulling and pushing modes.

Figure 1 is a sectional view of a dual mass flywheel which is generally designated by 10 and forms the torsional vibration damiDer in the oresent invention. It is -ooin'Led out that a corresponding configuration can also be provided, for example, in the case of a clutch disc or the like.

The dual mass flywheel 10 has, as input element, a hub 1-2 which can be fastened by studs 14 on a flange, not shown, of a crankshaft of an internal-combustion engine or the like.

Radially externally, the hub 12 carries a first- mass 16 on which a starter ring gear 18 is also fixed.

- v -L -L Ihe dua'L mass flywheel l0 also comprses an output element 20 comprising a first cover disc 22 and a second cover disc 24 which are rigidly connected to one another in a radially outer region by rivets, studs or the like not shown in the drawings.

Lhe second cover disc 24 extends radially inwards and rests on an axial bearing 26 and is also guided on a radial bearing 30 with a bent portion 28 extending substantially parallel or concentrically to an axis of rotation A. The second cover disc 24 carries a second mass 32 which forms a flvwheel comoonent of a motor vehicle friction clutch partly illustrated in Eigure I and generally designated by 34. A damping spring arrangement 36 which is shown schematically in Figure 2 acts between the hub 12 and the outQut eLement 20 comprising the first and the second cover discs 22, 24. The damping spring arrangement 36 comprises two damping spring units 38, 40 which are arranged at an angular interval from one another. Each of the damping spring units 38, 40 Ln turn comprises three damping sorinas 42, 44, 46 which are connected iin ser- ies w-ir--h- one another. int-ermediate elements 48, 50 on which damping springs 42, 44, 46 immediately adjacent to one another preferably rest permanently are provided between the individual damping springs of each damping spring unit 38, 40.

The intermediate elements 48, 50 are peripherally displaceable about the axis of rotation A with respect to the hub 12 and the output element 20. For example, the intermediate elements 48, 50 can be individual intermediate shoes auided on corresponding sliding faces. However, the intermediate elements 48, 48 of the two damping spring units 38, common ring element 49 or Lements 50, 50 of the two similarly held together by a the intermediate elements 48, rotation and the intermediate toaether round the axis of Figure 2 damping also shows that the spring unit 38 are preferably held together by ring segments and the intermediate damping spring units 38, 40 are ring element 51. in other words, 48 rotaie together during relative elements 50, 50 accordingly rot-ate rotat Lcn A. The -111UStration in damping springs 42, 44, 46 of each have different spring characT-eristics, i.e. spring constans. in the illustrated embodiment, the damping spring 44 which is arranged in each case in the centre of each damping spring unit 38, 40 has a lower spring constant than the two externally arranged damping springs 42, 46 which, for example, have the same spring constant.

it is also mentioned here that the illustration in Figure 2 shows on'Lv one o)erating state, namely a pulling State, in which a torque is transmitted to the power train by a crankshaft and vLa the hub 12. In this State, the hub 12 acts with a control region 52, for example a control edge 52, on one end 54 of each dampiner spring unit 38, 40 and presses via the dam.Dina s13rinas 42, 44, 46 with interposition of the intermediate elements 48, on a corresponding control region 56 on the output- e-Lemeni. 1 20, for example corresponding control edges 56 which are -provided on the first and on the second cover disc part 2,2, 24.

in other words, each damping spring unit 38 presses on the output element 20 with its opposite end 58 in the pulling state.

in the reverse state, i.e. in the pushing state, in which a motor braking effect is employed and a torque is introduced from the power train in the direction of the motor, the arrangement is such that the hub 12 presses with a control region associated with the damping spring 46 on this spring 46 and the damping spring units 38, 40 would rest with their dam- pina si)rinas 42 on a corresponding control region of the output element 20, i.e. the first and second cover discs 22, 24. In other words, the direction of torque introduction would be opposed to that shown in Figure 2.

it can also be seen in Figure 1 that, as described hereinafter, friction devices are provided by means of which, in the event- of torsionall vibrations, the relative rotation between various components With respect to one another, which is converted in-LO frictional work, can be dissipated. Thus, a friction element 60 is provided between the intermediate element 50, i.e. either the region with which the intermediate elerneni: or the intermediate elements 50 project between the damping so--irlcl 44, 46 arid/or 12 annular region which connects the two illustrated intermediate elements SO, 50, and an axial end face of the hub 12. The friction element 60 can be fixed, for example, on the intermediate element 50 which can also comprise the ring portLon 51 for the purposes of the following description, and can act frictionally on the hub 12 during relative rotation between -her friction element n"-e-,mediate elemenland hub 12. A furt 62 which can be, for exami)le, annular in design, rests on cover disc 22. Between the friction element 62 and intermediate element 50 there acts a biasing spring 64,

Lhe the for example a spring washer 64 or the like, which presses the intermediate element 50 acrainst the hub 12 with interposition of the friction element 60 and at the same time presses the friction eiement- 62 against the cover disc 22. Therefore, the biasing spring 64 forms a further friction element. For examiDle, the biasing spring 64 can be fixed on the intermediate element 50 so, during relative rotation between the intermediate element SO and the output element 20, the friction element 62 acts frictionally on the output element 20, which slides on this element 62 while generating a frictional force.

The friction element 62 comprises at least one peripherally extending project-ion 66 which engages in a complementary recess 68 in the hub 12. Although not shown in Figure i, the recess 68 has a peripherally elongated configuration so the friction element 62 can move peripherally freely in the respectively associated recess 68 with its projection or its projections 66 in a snecific rotational angular range. Figure 1 also shows that the -projections 68 are 'Loaded by a further biasing spring 70 which presses them, and therefore the entire friczion element 62 in the direction of the first cover disc 22. As the f irst and second cover discs 22, 24 are rigidly connected to one another, a closed force f low is -orovided bv the suDDort of the biasing spring -70 on the second cover disc 24. The second biasing sp-ring 70 could be omitted as the first biasing spring 1 64 already generates a biasing force pressing the friction element 62 against the output element 20.

it is pointed out here that, owing to the biasing action of the first biasing spring 64, the entire output element 22 is pressed ax'lallv to the Left with resDect to the hub L2 in the illustration shown in Figure 1, so the second cover disc 24 rests appropriately on the axial bearing 26.

Before the mode of operation of the above-described friction elements is described hereinafter, the siDring characterLS-LiC Of a r-orsional vibration damper, as shown in Figure 2, i.e. a torsional vibration damper with three springs per damping spring unit 38, 40 and one spring having a different spring constant from the other two springs will be described With reference to Figure 3.

The graph in Figure 3 shows the relative between the input element, i.e. the hub 12 element 20 on Its horizontal axis, starting position designated by zero. The vertical relative rotational angle of the intermediate respect to various components. Thus, the desianated bv A and A' in rotation or the relative rotational angle between the intermediate element 50 and the intermediate element 48. The curve B or B' illustrated by a broken line shows the relative rotation between the intermediate element 50 and the hub 12 and the line C or C' designated by a dash-dot- dash shows the relative rotation between the intermediate element 50 and the our-put elemen-- 20. Furthermore, a positive relative rotational ang Le in Figure 3 represents a rota-Lion in the pulling direction, i.e. inTr-oduct-ion of force from the hub 129 ro T-Ine damping spring 42, the damping spring 44, the damping spring 46 and then the out-put element 20, whereas a negative rotational the drawina shows rotational angle and the output from a neutral axis shows the element 50 with continuous line the relative 1 14 angle shows the pushing state, i.e. introduction of force from the output element 20 to the damping spring 42, the damping spring 44, the damping spring 46 and the hub 12.

The line A or A' will first be described hereinafter. As the relative rotation increases, the damipi-,j spring 44 is initially comoressed more markedLy owing to -the weaker or lower spring constant, whereas the damping springs 42, 46 remain almost uncompressed. in other words, the intermediate elements 50, 48 make a constant approach along the rising part of the curves A and A'. Once a oredetermined kink anale ot, representing the max imum possible compression of the damping spring 44 -i S reached, a further rotation between the intermed-i-ate element 50 a n d th e intermediate element 48 is no longer possible so the relative rotationai angle between the intermediate element 50 and the intermediate element 48 remains constant above the kink angle (x,., even when the rotational angle between the hub 12 and the output element 20 continues increasing. This does not depend on whether the operating state is a pushing or a pulling s7--ate.

The relative rotational angle between the intermediate element and the hub J12 which is reproduced by the lines B and B' will te, e.

be described next. in the pushing staL With a positive rotational angle between hub 12 and output element 20, the relative rotational angle between the hub 12 and the intermediate element 50 initially increases relatively markedly as the dam-cina scrinj 441 is comuressed to the kink anale (x., owing to its lower spring constant. Once this kink angle is reached, the damping spring 44 cannot be further compressed but rather the damping spring 42 and therefore obviously the damping snrina 46 is com)ressed when the reLative rota-Lion between the hub 12 and the output element 20 is sustained. As the compression content- of the damping spring 44 is now lacking. the 1 r relative rotational angle between the intermediate element 50 and the hub 12 varies more slowly above the kink angle ct,' as a function of the rotational angle between hub 12 and output element 2M. The characteristic is reversed in the pushing mode reproduced w-it'-n negative rotational angles. In the pushing mode, the hub 1-125 acts directly on the intermediate element 50 via the damping springs 46 so initially only a relatively smallincrease in the relative rotational angle between the hub!2_ and the intermediate element 50 occurs as the relative rotational angle between the hub 12 and the output element 20 -i S essentially generated by the damping springs 44. if the k_ink- angle aw. -1s achieved again, i.e. if the damping spring 44 is completely compressed or further compression thereof is no longer possible, the damping spring 46 contributes more markedly to the interception of the relative rotation between the hub 12 and the OUtput element 20 as the relative rotation between the hub 12 and the output element 20 is sustained, so a steeper rise in the characteristic curve exists above the kink angle et..

, a s s h o w--n b y e 11 -i n e B 1.

The 'Line C or C' represents the relative rotation between the intermediate element 50 and the output element 20. It is exactly opposed to the characteristic described hereinbefore with respect -Lo the line B or B'. This is due to the symmetrical design of each daikiDing spring unit 338, 40, as shown in Figure 2. Tn other words, in pulling mode, the output element 20 acts directly via the damping spring 46 on the intermediate element 50 so a shallow rise exists _here along 'Line C until the kinkangle a is reached again. Owing tO the result-ant complete compression of the damping spring 44, the characteristic then rises more steeply. in pushing mode, the damping spring 44 now also acts in addition to the damping srirLna 42-, bet-ween +the intermediate element 500 and- the output element 20, so there is a relatively steep rise to the kink 16 angle aK and a flatter rise after attainment of this angle along the line C' owing to the resultant compression of the damping spring 4.2.

It is pointed out thar opposing behaviour can be ach-ieved by reversing the spring characteristics between the damping spring 44 on the one hand and the damping springs 42, 46 on the other hand..Furthermore, the desired damping sprina behaviour, which is achieved by the superimposition of the various damping springs, can be adjusted by selecting three different damping springs per damp-i-ng spring unit or by providing more than three sDrinas.

The mode of operation will now be described hereinafter with respect to tn-e generation of the frictional- force with reference to Figure 4.

The nulling state which corresponds to the right-hand part in Figure 4 between the hub 1-2 and the output element 20 is first considered agai-r here.

The dual -mass ff -1yw'-n-ee-l 1-0 is in a neutral position when there is no torcrue to be transmitted between the hub 12 and the out-out element 20. in t-his state, it- is first assul-med that the projection 66 or the projections 66 are arranged in the J long itudina 1 central region of the associated recess 68. In other words, hal-f the -oeriphera'L span of the recesses 08 defines a limit angle a,:; up to which no frictional force is generated between the hub 12 and the output element 20. Figure 4 shows the friction device Inas an entraine.' effect 'between +.-'.,e hub 1.22 and the OUtnUt element 20 and is formed from the friction element 62 and the cover disc 22. Frorr. the beginning of relative rotation, i.e. starting from the neutral position, however, th- e element 60 wh -i ch i:z fixed on th e - -- - -L 1,7 intermediate element 50 and slides on the hub 12 acts between the hub 12 and the intermediate element 50. in other words, the friction element 60 forms, together with the hub 12-, a further friction device which always acts independently of the relative rotational angle. If the limit angle (xs which -Js defined by half the peripheral span of the recesses 68 and the thickness of the projections 66 and generally lies in the range of 20 to 50 is achieved or exceeded, the projections 66 strike the associated ends of the recesses 68. This is a state in which, during further rotation between the hub 12 and the output- eleirent- 20, the friction element 622 is entrained by the hub 12 and slides w-it"-nfriction on the cover disc 22. This is reproduced in Figure 4 by the friction device 62, 22 act-ing between the hub 12 and the output element 20.

Before attainment of the limit angle a,-, the first biasing sprincr 64 is rigidly rotatable, for example, with the intermediate element 50 acts between the intermediate element 50 and the friction element 62 which is rigidly rotatable in this state -th the OUtLIDUt element 20. In other words, a further friction wL - L L L device acting beneath the limit angle is formed by the biasing spring 64 and the friction element 62 and acts between the intermediate element 50 and the output element 20.

if the limit angle (xG is now attained or exceeded and the friction element 62 is then entrained by the hub 12, the friction device formed from the biasing spring 64 and the frict- i --e on element 62 no longer acts between th -intermediate element 50 and the outiDut element 20 but now acts between the intermediate element 50 and the in - - -12. In ot ' r)er put element words, the friction device formed by the biasing spring 64 and the friction element 62 acts beneath the limit angle (x,-, between the..,-i'Leriried-La-Le element 50 and Lhe OUtOUt ele.ment 20 and acts above the limit angle c-, between the intermediate element 50 and ±he hub 12.

With each friction device, the individual frictional work defined by the product of the frictional moment which is generated in the respective friction device by the relative rotational angle between the components between the resnective friction devices act.

In the state below the limit angle, rhe frictional work iss the sum formed from the product Of the frictional- moment of the -.ion ellemenl60 on the hub -at f rict 12 and the rellative rot onal anale between hub 12 and intermediate element 50 and the 1Droduct of the frictional moment between the biasing spring 64 and the friction element 62 and the relative rotational angle between the intermediate element 50 and the outpur element 20. Above the limit angle ecG, the tOtal frictional work is the sum formed from the product of the frictional moment between the friction element 60 and the hub 12 and the relative rotational angle between the hub 12 and the intermediate element 50, the Droduct of the frictional moment between -he spring element 04 and the friction element 62 with the relative rotational angle between the intermediate element 50 and the hub 12 and the product of ±he frictional moment- between the friction eleme-± ' I. e 02 and +El. cover disc 22 and the relative rotational anale between the hub 12 and the output element 20.

ft can be seen that graduated frictional operation rakes p-Lace with the dual mass flywheel 10 in which there is an additional z frictional work comnonent when the 'Limit anale (x- is exceeded, t'-rl-- is frictional work- componenr_ being effective in C-1he evenc off particularly pronounced variations in torque. A -oarr--icu-lar advaniage of th.e to-rsionall vibration damper constructed in accordance with the invention is that the occurrence of 19 particularly pronounced variations in torque can be appropriately prevented regardless of whether the operating state is a state of relatively high or relatively low load.

This is due to the fact that, in a state of relatively high load, i.e. a relatively pronounced relative rotation between the hub 12 and the output element 20 when the limit angle a- is exceeded, the friction element 62 is initially coupled to the hub 12 and slides on the cover disc 22 while generating a - onal force. T f an almost constant relative rotational fric+. 1 angle is adjusted between hub 122 and output element 20, which angle depends on the load state, a torque vibration will be adjusted round this deflection angle. If this vibration, i.e.

the angular range of- the vibration, is smaller than twice t-n-e limit angle c,,, L.e. if only weak torcrue variations or torsional vibrations are generated in the high load state, the friction device 62, 22 is ineffective again as the projections 66 can move freely in the associated recess 68. The friction device 60, 12 which acts between the hub 12 and the intermediate element 50 a n d t"-n- e friction device 64, 62 which acts between the intermediate element 50 and the output element 20 are then effective again. Only if greater variations in torque occur after deflection to the deflection angle SO the varLaLlons round the deflection angle exceed the limit angle oiG, measured from the deflection angle as a basic relative rotational angle, the friction device 62, 22 is made effective again and the -friction device 64, 69 acts between the intermediate element 50 and the hub 12. in other words, independently of the -in-s-antaneous load state, the d arn.p i n g characteristic can always be adapted opt ima -1 1 y t 0 t-n e extent o f the -instan-Laneous",,,7 ex-istinr, torsional vibrations occurring in the power train. The changeover of the friction device 64, 62 with respect r-o its action when the limit angle a-, is exceeded is also advantageous.

in fact, if t'-n-e kiink angle (1K is not yer_ exceeded, th e intermediate element 50 will rotate more markedl_y with respecr- to the hub 12 than with respect to the output element 20 owing to the easier compressibility of the damping spring 44, as shown by the lines B and C in Figure 3. in other words, if the 4:

friction device 64, 62 acts between the hub 12 and the intermediate element 50, greater frictional work is generated with the same change in the relative rotational angle between the hub 12 and the output element 20 than if the friction device 1-, 64 Jate element SO and the output 0 Z_ 0 acted between the intermed-L _L U element 20 in this state. in other words, great variations in torque can therefore be damped to a greater extent.

The foregoing description of the pulling state accordingly applies to the pushing state. Below the limit angle cc,, the friction device 60, -112 also initially acts between t-n-e hub 12 and the - intermediate element 50 while the friction device 64, 62 acts between the intermediate element 50 and the output element d U. However, there is a difference here in that the individual frictional work generated in the friction devices is varied with respect to the pulling state. The reason for this is that, between the hub 12 and the intermediate element 50, only the damping spring 46 acts with a relatively large spring constant, i.,-. witIn the same relative rotational angle between 'nub -1-2 and output element 20, the intermediate element 50 will rotate with respect to the hub 1-2 with a smaller rotational angle than in the nullina state. The relative rotational anale between the intermediate element 50 and the output element 20 will accordingly -increase as the damping spring 44 now additionally act- with a lower spring constant between these two elements.

As the relative rotational angles between the individual components p-, aW a part -i-n the fr ic t. iona 1 work -i-n conj unct ion W 71'n e respecti v e frictional moments, as described hereinbeffore, diff ferent frictional work is generated here witIn the same relative rotational angle between hub 12 and output element 20. ii':: the limit angle a--- is exceeded, the friction 1 21 device 62, 02 again becomes effective and the friction device 64, 62 now acts between the hub 12 and the intermediate element 50. The foregoing consideration, that different frictional work is adjusted owing to the varying relative rotational conditions between hub 12 and intermediate element 50, also aonlies here.

Graduated friction damping behaviour is also generated in pushing mode so here again, independently of the load state, when relatively large variations in torque occur, they are suitably dampened, whereas only a weaker dam-ping force exists with relatively small variations in torque.

As described the limit angle c-- is generally ad-iusted so that it is much smaller than the kink angle aK. This can be seen when observing the graph in Figure 3 which shows that the kink angle a, lies in the region of about 300 In other words, in a state of relatively low load, the torsional vibration damper constructed in accordance with the invention will operate in a characteristic curve range as defined in the graph in Figure 3 between the kink angles (xK on the positive and the negative side of the horizontal axis.

However, ir relatively strong torques are to be transmitted, i.e. if the damping spring units 38, 40 are compressed to such an extent that the kink angle (x, is achieved, the foregoing remarks concerning the connection a-rid disconneCEL-Jon or changeover of the friction devices 62, 22 and 64, 62 also basicallv a-oo'Lv. The case is also considered hereinafter where, in the pulling state, the hub 12 and the output element 20 have rotated about a relative rotational angle of, for examp- le, 40' -o 7in with respect T one another, but remain almost sT-atioriar, this state. The damping spring 44 is then compressed until it is bridged and is no longer effective, and the friction element 62 has initially been entrained with the hub 1-2 and rotaued TI o r he angle of about 40' with respect to the output elern.ent 20. if 22 relatively state, the resiDect to one another in small variations in torque occur in this operating hub 12 and the output element 20 can oscillate with angular ranges smaller than twice the -limit angle without the friction device 62, 22 being -!)-is case, torque vari effective. in t I ations take place merely with compression and expansion of the damping springs 42, 46.

The friction device 60, 12 then acts between the hub 121 and the intermediate element 50, and the friction device 62, 64 between the intermediate element 50 and the output element 20. if the Limit angle (x, is exceeded, the friction device 62, 22 is connected and 'the friction device 64, 102 is in turn effective between tne intermediate element 50 and the hub 12. However, as the damping spring 44 is no longer effective in this state, the changeover of the friction device 62, 64 to an effect between the intermediate eLement 50 and the hub 12 does not affect the frictional force to be generated during further compression of the damping springs 42, 46 as these two damping springs are compressed to the same extent owing to the identical spring constant. The same applies to the pushing mode. in this operating state, as in the above-described operating states, the respective frictional work is formed by the sum of products of he JndJ vJ dual frictional MG.Ments -F the various frict 4 on devices with the relative rotational angle between those components between which the respective friction devices act.

it is pointed out that the graph in Figure 3 shows characteristic curves of the damping spring arrangement 36 shown in Fiaure 2, which are achieved Without the oresence of friction devices. Owing to the provision of the friction devices in the torsional vibration damper constructed in accordance with the invention, in particular owing to the changeover of the friction device 64, 62 from a range of action between the intermediate element-- -9(') and the outpu-,- element 20 to a range of action between the hub _.L and the intermediate eLement U, 1 23 characteristic curves are obtained which have a further kink on attainment of the limit angle m-,. This is described hereinafter by the example of the characteristic curves B, C in Figure 3.

On the basis of the relative rotational anal-e of zero, i.e. the neutral position, only the friction device 60, 12 initially acts between the hub 12 and the intermediate element 50. The friction device 64, 62 acts similarly between the intermediate element 5 'U and the output element 20, leading to the character is t -ic curve C in Figure 3. If the friction device 64, 62 _Js now effective between the hub 12 and t-"-r)-e intermediate elemenz 50 upon attainment of the limit angle (xs, displacement of the intermedia'Le element 50 with respect to the hub 12 is made more difficult before attainment of the kink angle (xK, whereas displacement tnereof- with respect to the output element 20 is s impl -i f _Jed owing to th- e lack of friction between these components. The intermediate element 50 will rotate 'Less during further relative rotation between the hub 12 and the output element 20 witIn -respect to the hub 12 and will rotate more with respect to the output element 20. In other words, the characteristic curve B will kink and become flatter on attainment of the limit angle ciG whereas the characteristic curve C will kink and become steeper on attainment of the limit angle a-G - The same applies to the negative rotational angles which reproduce the case of pushing load.

With the torsional vibration dawper constructed in accordance with rhe the ease of storing severalintermediate 48, 50 or intermediate discs with corresponding contact for the s-or-ings is possible owing to a very simple ell ements cortions construction, so damping spring units with three and more damping springs can be provided. owing to the plurality of frictional c)os-ir--ions, i.e. the various friction devices, great frictional work can also be generated when using smaller biasing 24 spring elements. Better damOing behaviour with improved decoupling between the input and output side can be obtained by adapting the frictional force to be generated to the relative rotational angle or the variation in the relative rotational angle between input and OUtpUt elements. imiDroved orotection against damage or destruction is also provided, in particular, owing to the increase in the destroyed frictional work in the case of relative rotational angles. By appropriate choice of the spring constants of the various damping springs and the coefficients of friction of the various components which rub against one another, the torsional vibration damper can be adapted to desired operating characteristics.

it is -cointed out that various modifications are possible W_LLh the above-described embodiment, without changing the principle or the basic mode of operation. For example, as al-ready described, the damping springs 42, 46 can have different spring constants and rigidities. It is also possible to use only two damping springs per damping spring unit, in which case only a single intermediate element has to be provided. With an embodiment of this type, moreover, the same mode or operation as described hereinbefore can be obtained, but the frictional wo-rk generated for pushing and pulling mode is identical. A friction device which acts between the intermediate element 48 and the input element and/or the output element can also be provided.

The function of _input and output element can be reversed, i.e. the two cover discs 22, 24 rigidly connected to one another can a'Lso be connected tO the drive shaft, i.e. a crankshaft.

The friction element 60 could also be rigidly connected to the hub 12. Similarly, the biasing spring 64 could be rigidLy connected r 0 the friction element 62 so steell-on-steel frictional contact- is provided on the region or contaci ce.7-ween the biasing spring 64 and the intermediate e-,ement or intermediate ring 50. Similarly, the biasing spring 70 could be fixed on the projections 66 of the friction element 62, so frictional contact would be created between the biasing spring 70 and the second cover disc 24 in the form of steel-on-steel friction. The functions of the intermediate discs 50, 48 can be exchanged so the operating characteristics are exchanged with respect to pushing and pulling mode.

accordingly End stops are preferably provided for the respective damping springs so the springs are prevented from blocking when high torques are introduced.

Claims

Claims

26 1. A torsional vibration damper, in particular for arrangement in the Dower train of a motor vehicle, said damDer comprising an input element (12), an output element (20) which is rotatable relative to the input element (12) around an axis of rotation (A), a damping spring arrangement (36) which is arranged in terms of action between the input element (12) and the output element (20) and serves to counteract a relative rotation between the input element (12) and the output element (2, 0 1, the damDina spring arrangement (1 3 -C)) comprising at leas-,- one damping spring unit (38, 40) with at least two damping springs (42, 44, 46) which are connected in series in terms of action, which damping loads the inDut element (12) or the in the event of a relative rotation spring unit (38, 40) output element (20) between the input element (12) and the output element (20) ion of rotation ol:

uncto- of a relative direct- and as a.1 11 the inout element (12) and the output element (20) at- a first damping spring unit end (54) and loads ---Iheoutput element (20) or the input element (12) at a second damping spring unit. end (58), an intermed-late element (48, 50) between each two damping springs (42, 44, 46) of the at least one damping spring unit (38, 40), on which the damping springs (42, 44, 46) are supported with their mutually facing ends, the ntermed-Late element (40, 50) being displaceable with respect to the input element (12) and the output element (20) in the event of a re-ative rotation between Lhe inl,3ut element (12), and the output element (20), 27 a first friction device (62, 22) which acts to generate a frictional force between the input element (12) and Output element (20) or components associated therewith and a second friction device (60, 12, 64, 62) which acts between at least one (50) intermediate element (48, 50) provided in each damping spring unit (38, 40) and the input element (12) and/or the output element (20) or components associated therewith in each case for generating a frictional - force, wherein at 'Least one of the first and second friction devices (62, 22) is designed to generate a frictional force essentia-Liy only when the relative rotational angie between the input element (12) and the output element (20) is greater than a -predetermined limit angle ((xc-) in the range of a basic relative rotational angle from a neutral position.
2. A torsional vibration damper according to claim 1, wherein the first friction device (62, 22) produces a frictional force onIv when the relative rotational angle between the input element (12) and output element (20) is greater than the limit angle (OG).
3. A torsional vibration damper according to claim 2, wherein the second friction device (60, 12, 64, 62) generates a frictional force with all relative rotational angles between the input element (12) and the output element (20).
4. A torsional vibration damper according to cl aim 3, wherein the second friction device (60, 12, 64, 6622) provides a firSt friction device range (60, 12) which generates a frictional force which is substantially independent of the relative rotational angle between the input element (12) and the output element k20) 1 1 28
5. A torsional vibration damper according to claim 4, wherein the second friction device (60, 12, 664, 62) comprises a second friction device range (64, 62) which produces a frictional force as a function of the relative rotational angle between the input element (12) and the output element (20).
0. A torsional vibration damper according to claim 5, wherein the second friction device range (64, 62) generates a frictional fo--ce between the intermediate element (50) and the input element (12) or the output element (20), when the relative rotational anale between inDut element (12) and output element (220) is smaller than or equal to a predetermined angle (a-G) a n d generates a frictionall force between the intermediate element,,50' and the output element (20) or the input element (12) and when the relative rotational angle between the input element (12) and t-ne output element (20) is greater than the predetermined angle.
A torsional vibration damper according to one of claims 1 to 0, wherein the at 'Least one damping spring unit (38, 40) comprises at least three damping springs (42, 44, 46), a respective intermediate element (48, 50) for supporting the damping springs (42, 44, 46) being provided between the mutually facing ends of directly adjacent damping springs (.42, 44, 46) in each case and the second friction device does not act on at least one (68) of the -intermediate elements (48, 50).
R A torsional vibration damper according to one of claims -1 first friction device (62, 22) comprises a Lo /, wherein the t.0 11-11-1 Fi-rctfrict-len ellement- (62) which acts with _friction onthe J -1 e (20) a-rid 'La 1 l y npul: e menr ( 1 2) or the output e is essent, -- freeiv rotatable to the Ilimit angle ((xG) with respect tothe output- element or the input element (12) on the basis of Ehe basic relative rotational angle between the inpu 1 r_ e-lement- 1 29 (12) and the output element (20) and, after the limit angle (c(G) is exceeded, can be rotated with the input element (12) or the output element (20) while generating a frictional force on the outnut element (20) or the input element (12).
9. A torsional vibration damper according to claim 8, wherein the second friction device comprises:

a second f riction element (60) connected to the intermediate eLement (50) and with which the intermediate element (50) acts frictionally on the input element (1-2) or the output element (20) and a third friction element (64) which is arranged in terms of action between the intermediate element (50) and the first friction element (62).
10. A torsional vibration damper according to claim 9, wherein the third friction element (64) is fixed on the intermediate element ('00) and acts frictionally on the first friction element (62).
11. A torsional vibration damper according to claim 9 or 10, wherein the third friction element (64) is a biasing spring (64) which is supported on the first friction element (0.2) and biases the intermediate element (50) onto the input element (12) or the output element (20).

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12. A torsional vibration damper according to claims i to 10, wherein the input element (12) or the output element (_10) comprises a central disc part (12) and the output element (20) or the input element (12) comprises a first cover disc (22) arranged on a first- axiall side of the central disc part (12) and a second cover disc (24) which is arranged on a second axialside of the central disc part (12) and is rigidly connected to the first cover disc (22) and both the central disc part (12) and the first and the second cover discs (22, 24) have, in the region of the two damping spring unit ends (54, 58) of the at least one damping spring unit (38, 40) in each case, control regions (52, 56) to be loaded by the associated damping spring unit end (54, 58) of the at -1 east one damping spring unit (38, 0).
13. A torsional vibration damper according to claim 12 when appended to claim 8, 9, 10 or 11, wherein the first friction element (62) acts on a part (22) of the first and second cover discs (21.2, 2-14) and is pressed bv at least one biasing spring element (64, 70) onto the part (22) and the biasing spring element (64, 7/0) is supported on the another part (24) of first and second cover discs (22, 24) and/or on the inter-mediate element (50).
14. A torsional vibration damper according to claim 8 or one of claims 10 to 13, when appended to claim 8, wherein the first friction element (62) comprises at least one driving projection (00) which encraaes in a peripherally extending driving recess (68) in the input element (12) or the output element (20), a peripheral span of the driving recess (68) essentially determining the limit angle (a-G) in cooperation with a peripheral span of the driving pro-iection (66).
15. A Eorsional vibration damper accord-ing to one of cla-ims 1 tn 14, w,)-ere-in the basic relative rotational angle between the input element (12) and the output element (20) is a neutral ana' rotational Le which def-ines a neutral relative rotation between input element (12) and out-put element (20) when no torque is to be transmitted beyond ine torsional vibration damper in such a way:na-- ----e i-m-it rotational angle (cr,s) is 1 31 to be measured on the basis of the neutral relative rotational angle defining the neutral relative rotational Position.
16. A torsional vibration damper according to one of claims 1 to 15, wherein the basic relative rotational angle is a relative rotational angle between the input element (12) and the output element (20) which is adjusted with a torque which is to be Lransmitted beyond the torsional vibration damper (10) such that the limit angle ((xG) is to be measured on the basis of the relative rotational angle adjusted during transmission of the specific torque.
17. A torsionaL vibration damner or comr)onents thereof substantially as described herein with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings and/or having operational characteristics substantially as depicted in Figure 3 and/or 4 of the accompanying drawings.