ES2204208A1 - Clutch, coupling element as well as disposal formed by them and procedure for the assembly of a clutch. (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Clutch, coupling element as well as arrangement formed by them and procedure for mounting a clutch, wherein two clutch surfaces and two pressure plates belonging thereto and which are individually actuatable should make possible, in a clutch with at least two friction discs, a clutch process, respectively of soft disengagement of the corresponding friction discs. (Machine-translation by Google Translate, not legally binding)

Description

Clutch, coupling element as well as arrangement formed by them and procedure for the assembly of a clutch.

The invention relates to a clutch, a coupling element for a disengagement unit of a clutch as well as an arrangement formed by a unit of clutch disengagement and a coupling element corresponding and to a clutch assembly procedure.

The invention relates here in particular to clutches, which, in combination with double gearboxes, are use, respectively they should be used especially in the scope of motor vehicles. These gearboxes are currently in tests for use in the field of  motor vehicles, since conventional gearboxes already cannot meet the increasing requirements of the standards on emissions. In order to continue offering, as an alternative to automatic changes, respectively continuous changes, manual gearboxes work for it in automation of a manual gearbox. For this, it is proposed that a process Gearshift is done by means of two box shafts gearboxes each equipped with gear shift sprockets, which are  can be coupled with the gear change sprockets of a output tree One of the trees in the gearbox must always withstand even gears and the other tree in the box I change the odd gears. With the gearboxes of this class it is then possible to always put an even and one gear odd while the gear change process itself said takes place by means of coupling, respectively the decoupling of the corresponding gearbox tree. A gearbox of this kind is equivalent, from the point of view of its gearshift properties, essentially to a box of manual change, but it is cheaper and has a degree of performance higher as well as a greater number of gears than a change automatic. In addition, a gearbox of this kind also changes running under load - so it is not necessary to decouple it from the everything - and doesn't require synchronization as perfect as the necessary in conventional manual gearboxes.

To make a provision of this class you They need, therefore, two clutches. However, these they need a relatively large building space and are relatively expensive

The object of the present invention is therefore propose a provision, which, properly, can be coupled in action a gearbox of this class with a drive and that Despite this, it has a smaller space need possible.

As a solution, a clutch with at least  two friction discs, two clutch surfaces corresponding and two pressure plates belonging to it, which They can be operated individually. A provision of this class requires, on the one hand, a construction volume relatively small, since only one clutch is used and also, especially, a clutch housing. Especially, it's just necessary, for a clutch drive element to be connected with A motor or analog. In addition, this provision guarantees despite that, that the process of gear change, respectively the clutch, respectively the clutch can be adapted so adequate to existing conditions.

The two clutch surfaces are provided advantageously in at least one construction group joined together rigid with a clutch housing. This may be especially the Common clutch plate described above. A rigid union of This class can be built, on the one hand, cheaply. By other, individually actuated pressure plates make possible as until now clutch processes, respectively of disengaged individual.

In particular it is possible to arrange both Clutch surfaces on a clutch plate. This guarantees, on the one hand, a reduction of costs in the manufacturing and, on the other, an additional reduction in the volume of construction, since it is only necessary to provide a plate clutch. The clutch plate is preferably arranged centrally between the two pressure plates. This results in a additional reduction in construction volume, so that a Clutch of this class only requires a construction volume inappropriately greater than in the case of a simple clutch.

A clutch according to the invention has a especially compact construction, when a clutch housing surrounds the two friction discs and the two pressure plates as well as eventually the clutch plate.

The housing may have radial holes for cope with the accumulation of heat due to the two discs of friction.

The housing can be specially designed in such a way so that it compensates the driving forces of two springs of drive each assigned to a pressure plate. This is can perform relatively easily, when the Housing surrounds the remaining part of the clutch. The compensation is you can perform in this case by means of a spring support drive or other spring elements as well as one or of several additional construction groups rigidly joined With clutch housing.

Preferably, the first of the two plates of pressure is pressed in the unloaded state against the surface corresponding clutch (normaly closed NC). The concept "unloaded state" describes in this regard a state in the one that the clutch is not activated. In a provision of this class is guaranteed, that the corresponding tree is also coupled in the event of a malfunction.

In particular, it is possible that the pressure plate is pressed against the friction disc by means of a spring saucer. In this way it is possible to build the partial layout of this clutch as an individual clutch known per se.

In addition, the second of the two pressure plates can allow, in the unloaded state, that the friction disc corresponding turn freely (normaly open NO). This way you guarantees that this tree is decoupled, even with a breakdown of operation. This has the advantage, especially in the cooperation with a first NC pressure plate, which are not clutch concurrent marches.

Both the first march and the march cooperate advantageously with the NC pressure plate, from so that in the case of a breakdown, at least the first gear, respectively reverse gear. It is understood, that a construction of this kind of gearbox from a NC clutch and a clutch is also NOT advantageous with Independence of the remaining clutch characteristics.

Friction discs are attached with preference with two concentrically arranged output shafts, which in turn lead to the corresponding gearbox. This it allows a very compact construction of all the arrangement formed by clutch and gearbox. In addition, the own clutch can possess an extremely construction compact, since then the friction discs are arranged coaxially.

At least one of the friction discs can be Built with a gentle nod. This can compensate for alignment errors, which may occur, especially due to to coaxial output trees. In addition, a provision of this class also lends, regardless of the remaining Clutch characteristics, for cheap compensation of errors of this kind.

It is especially possible that the friction disk Build elastic in the radial direction. This can be guarantee for example by means of a suitable hole provided in an area of the friction disc, which rigidly joins in the direction rotation the friction lining with the corresponding shaft. For this should not be necessary, especially spring elements independent. The "rigid" concept describes on the contrary and in relation to what has been said a coupling with kinematic union of shape in the direction of the contour between the tree and the lining of friction, which, however, can nod.

In addition, the friction disc may possess, in especially in the area that joins the friction lining with the shaft corresponding, axially directed areas, which make possible a nodding of this class. In addition, with these axially directed areas construction space can be better utilized, so that The clutch can be built smaller.

The lining of the first of the two discs of friction is preferably constructed soft and the lining of the second of the two friction discs is built hard. The disk of soft friction can be attached in this case with a tree for the First gear and / or for a reverse gear. With friction disc Soft is guaranteed, that the clutch guarantees a start nice. On the contrary, the hard friction disc does not have to meet this condition, as it is only used for more marches high. This provision is especially advantageous because of the fact that a hard friction disc has a construction volume considerably less.

The concept of "soft friction disc" describes in this context a friction disk, which satisfies all the requirements, which a clutch must meet during the start. On the contrary, a "hard friction disk" is only something harder than allowed by these requirements. As a hard friction disc, a special rigid sintered coating while as a disk of Soft friction is chosen a lining itself known for vehicles. In special, for the latter you can also use springs of cover.

To drive the pressure plates,  it can provide at least one drive spring, which has both inside, as well as outside a lever arm. This means that a pivot point defined by the forces centrifuges is shifted radially inwards and that the lever arms oriented against each other are subjected to turning torques defined by centrifugal forces. With this you can proceed to compensation of centrifugal forces. Also, in the outer lever arm in the radial direction, which normally it will be the shortest, an additional mass can be provided, which reinforces a centrifugal mass compensation of this class. A provision of this class is also applicable, regardless of remaining clutch characteristics, to normal clutches, respectively simple.

Especially in relation to the axial areas of friction discs, which make it possible to reduce the volume of construction, it is also possible to arrange the springs of drive almost radially, so that the influence of the Centrifugal force is minimized, in addition, widely.

The clutch can have a unit of disengaged with two disengaged bearings, which are independently operable and always cooperating with one of The two pressure plates. With the use of a unit of disengaged from this class you can build the clutch according to the invention with a relatively small volume, although the Pressure plates are individually operable.

Preferably, at least one of the bearings of  disengaged is hydraulically operated. This makes it possible, by one side, a relatively simple force transmission and, for another, that with a relatively small construction volume is They can generate great forces.

Preferably, at least one bearing of disengaged is coupled in action with an electric actuator. This  it can also be done for example through a system hydraulic as force transmission element, respectively of force multiplication. The use of an actuator electric allows without more a computer controlled excitation of the clutch, so that the gear change processes, respectively the disengagement of an odd gear and the clutch of an even gear - respectively in the reverse direction - can be regulate optimally.

Preferably a first bearing of externally disengaged in the direction of radial to the second clutch release bearing. This guarantees a compact construction and makes possible, in addition, a radially symmetrical construction of so that a dependent assembly of a angle.

The disengagement unit is also available with coaxial preference with at least one of the output shafts, of so that the construction of the entire provision is symmetrical rotation and compact. Because of this, a provision of This class is extremely reliable and can be mounted with ease, since an alignment of the unit is not necessary disengaged in relation to the remaining groups of building.

The disengagement unit is configured with preference so that the disengagement bearings are subjected in the activated state to opposing forces. Through appropriate choice of corresponding spring elements or by means of additional compensation element can be obtained in this case a wide compensation. This results in not only the clutch itself has an almost force-free construction, but also that the disengagement unit itself is almost free of forces in the driven state. This can reduce the efforts, which act on the gearbox, respectively the engine crankshaft

At least one clutch bearing may be coupled in action with a drive spring designed such so that, in the unloaded state, it acts against the bearing of disengaged with a retention force, preferably the force of retention of a hydraulic drive for the bearing of disengaged. With this, the entirety can be built without gaps of the provision. On the other hand, instead it is also possible to provide additional spring elements, which act directly on the clutch release bearing.

Between the first of the two springs of drive, preferably between an outer lever arm of the drive spring, and the first of the two plates of pressure can be provided a drive element. With it they can transmit the driving forces over a distance greater, so that, despite the use of a unit of disengaged with two disengaged bearings, the pressure plate at a different axial point. This guarantees a Simple construction with which all assembly is facilitated. This it manifests later in a corresponding reduction of costs

A provision of this class also guarantees that the disengagement unit is accessible from one side and that the Two pressure plates can be operated without further ado. The element of drive is preferably arranged radially outside the friction discs

The drive element may comprise the minus a disengagement rod preferably arranged axially between the drive spring and the pressure plate. This can be transmitted in a relatively simple way the corresponding driving forces.

In particular, it is possible that the element of drive has several disengagement rods joined together by means of a clamping ring. This clamping ring makes possible in this case, that the entire disengagement element can be mounted in a single operation, which results in a corresponding cost reduction.

To obtain an improved compensation of forces can be built tangential spring springs arranged between the pressure plates and the housing to hold pressure plates rigidly rotated relative to the housing, so that they oppose a disengagement force. This means that this pressure plate has to be disengaged with an amplified disengaged force, which is advantageous, when the clutch of the other pressure plate is performed with a force greater than that necessary for disengaging of the first pressure plate. It is understood, that a spring of tangential crossbow of this class, which exerts a force opposite to a disengagement force, can also be used advantageous for compensation of forces, regardless of the remaining characteristics of a clutch. This is especially advantageous in cooperation with a drive element, since this can result in active disengagement, so that the spring Tangential crossbow does not have to be used for disengaging, as is the case according to the state of the art.

In addition, the unit of disengaged with a symmetrical rotating coupling fitting with  relation to an axis of rotation of the clutch. This coupling fitting may comprise at least one coupling element for the joint of at least one disengagement bearing with an actuator.

With such an arrangement you can considerably simplify assembly, since it is not necessary mount the union in a certain direction of rotation. For him On the contrary, it is possible to join it simply with a coupling element correspondent.

Accordingly, the invention also proposes a coupling element for a clutch, respectively for the clutch disengagement unit, which has a cavity symmetrical rotation Also in this cavity you can provide least one coupling element for joining at least one disengagement bearing with an actuator.

In an arrangement of this kind it is especially possible, that the disengagement unit is fixed, respectively a with the remaining clutch and then the assembly of the entire provision. This is only necessary then that the coupling coupling of the unit disengaged into the corresponding cavity.

Accordingly, the invention also proposes an arrangement formed by a disengagement unit of a clutch and a corresponding coupling element, which have at least one slot in one of the two groups of construction formed by the disengagement unit and the element of coupling. The slot can be joined in this case with a hole of the other group of the two building groups formed by a disengagement unit and a coupling element, of so that a union can be created between an actuator and a disengagement bearing of the disengagement unit.

The slot can be provided in this case in the union connector of the disengagement unit or in the element of coupling

The joint between the actuator and the bearing of disengaged occurs in an arrangement of this class with independent of the angle of rotation of the disengagement unit, of so that the disengagement unit can be mounted without further ado.

A simple assembly of the clutch due to the fact that, before fixing the housing of the clutch, a disengagement unit is arranged behind a drive spring on the side of the friction disc. With that a union occurs between the disengagement unit and the part remaining clutch so that all of the layout can be mounted afterwards in a single step of mounting.

An assembly of this kind can be made of an especially simple way, when the disengagement unit joins, after arranging it behind the drive spring, With a coupling element. This is done preferably after fixing the clutch housing.

It is understood, that in the clutch described in The above is only of secondary importance, that the flow of forces occur from the clutch plate, respectively the pressure plates towards the friction disc shafts or inversely. From this point of view, the present invention it also covers provisions in which construction groups designated with the concept "exit" are used as drive

Other advantages, objectives and properties of Present invention are explained by the description of the drawing attached in which three clutches are represented by way of example according to the invention. In the drawing they show:

Figure 1, in section, a first form of execution of a clutch according to the invention.

Figure 2, a plan view of the springs of tangential crossbow of the clutch of figure 1.

Figure 3, a side view of the spring of outer clutch drive of figure 1.

Figure 4, in section, the union between the drive spring and clutch release rod of figure 1.

Figure 5, in a plan view, the arrangement of figure 4.

Figure 6, a variant of the arrangement represented in figure 4.

Figure 7, in a representation analogous to the of figure 1, a second embodiment of a clutch according to the invention.

Figure 8, in a representation analogous to the of figures 1 and 7, a third embodiment of a clutch according to the invention.

In the form of execution represented in the Figure 1 are arranged on both sides of a two clutch plate 30 friction discs 10, 20, which can be pressed against the clutch plate by means of pressure plates 11 and 21. In the clutch plate 30 is provided for this purpose surfaces 31 and 32 of corresponding clutch.

The clutch plate 30 is joined together rigid with a housing 40 fixed in turn to a steering wheel 41 of two masses or an analog device.

The clutch cooperates through these elements with a drive, respectively a motor.

Figure 1 shows the clutch in the no load state This means that the disengagement unit 50 It is not subject to a force. As you can see, plate 11 pressure is pressed in this state without load by means of a saucer spring 12 against friction disc 10 corresponding, respectively against surface 31 of clutch belonging to the (normaly closed NC). Conversely, the other pressure plate 21 is open and freely rotates the corresponding friction disc 20 (normaly open NO).

The housing 40 surrounds the two discs 10, 20 of friction as well as the two pressure plates 11, 21 and at their end away from the flywheel 41 of two masses it has support tabs 42, 43 in which support springs 13, 22 drive. Each of the drive springs possesses, both radially towards the inside, as well as radially outward lever arms 13a, 13b (provided with references by way of example in figures 3 to 5), which compensate each other in their action due to centrifugal force. In addition, these springs 13, 22 Actuators are arranged essentially radially. The lever arms 13b located externally in the direction radially have holes 13c in which they penetrate with their lugs 15 disengaged rods 14. These disengagement rods are joined together by means of a clamping ring 16. Ring 16 clamping as well as holes 13c and lugs 15 absorb centrifugal forces, which occur.

A form of alternative execution in which a tab 13c 'of spring 13' of  drive surrounds the disengaged rods 14 '.

The disengagement unit 50 has two bearings 51 and 52 of disengagement, which are coupled in action with the drive springs 13 and 22. If these bearings 51, 52 of disengaged are subjected to a load, exert forces on each other opposite on drive springs 13 and 22. In this case they are operated by means of two hydraulic pipes 53. The hydraulic pipes 53 flow into holes 54 provided for once on a fitting 55 of the disengagement unit 50. Fitting 55 is disposed in a corresponding cavity of an element 56 of coupling, at the same time, that in this cavity there are two slots 57 in which holes 54 open. slots 57 is in turn connected with actuators not represented.

As can be seen, the bearing 52 of disengaged is actually a clutch bearing, since, under load, close the pressure plate 21 against the plate 30 of clutch.

As follows directly from Figure 1, the forces of the two disengagement bearings 51 and 52 are They compensate each other. However, due to the characteristic of spring of leaf spring 12, this cannot be guaranteed total form To increase the degree of Compensation 17 spring tangential springs are designed, existing in any case according to the state of the technique, of the pressure plate 11 so that they oppose a disengaged. The sizing of the springs is done here from such that, with disengagement forces, respectively paths large disengagement, greater compensation takes place.

The friction discs 10 and 20 have linings different. While the friction disk 10 comprises a liner "soft" normal, like the one used in motor vehicles, the friction disc lining 20 is chosen as a sintered liner rigid. In addition, the two friction discs 10 and 20 comprise zones 18, respectively 23 directed axially, as well as holes 24 (not shown in friction disk 10), which make possible a friction disk pitch, respectively a radial elasticity This can compensate for possible misalignment of trees 1 and 2 not supported in the clutch side. As you can see, trees 1 and 2 as well as the disengagement unit 50 are coaxially arranged each.

The zones 18, respectively 23 axial create, in addition, a free space in which the unit 50 of disengaged.

In the arrangement described in Figure 1, couple the inner shaft 1 with the odd gears as well as with the reverse of a gearbox while the tree 2 cylindrical shaped exterior is coupled with gears peers

The housing 40 has a hole 44 to prevent  heat build up

Saucer spring 12 is chosen in the example described execution of steel to generate the forces of pressure needed Springs 13, respectively 12 of drive are chosen from a material as light as possible, of so that the influence of centrifugal force is reduced. With Preference can be used aluminum.

The execution example shown in the figure  8 is essentially equivalent to that shown in figure 1. Without However, the disengagement bearings 51, 52 are changed in their radial arrangement versus the exemplary embodiment represented in Figure 1. Accordingly, 13 '' and 22 '' springs result from slightly modified drive.

Also the form of execution represented in the Figure 7 is identical, from the point of view of its operation, to the forms of execution described above, but the 51 'and 52' disengagement elements are constructed as units of disengaged with radial action. With this you can minimize from advantageous way the influence. of the centrifugal force. Given the these units 51 'and 52' only act in the radial direction, the Construction of the entire arrangement is narrower. Without However, an arrangement 13a '' ', 13b' '' is used instead,  respectively 22a '' ', 22b' '' of relatively more levers complex.

Claims (37)

1. Clutch with at least two discs (10, 20) of friction, two corresponding clutch surfaces (31, 32) and two pressure plates (11, 21) belonging to them, which are individually operable. 2. Clutch according to claim 1, characterized in that the two clutch surfaces (31, 32) are provided in at least one construction group rigidly connected with a clutch housing (40). 3. Clutch according to claim 1 or 2, characterized in that the two clutch surfaces (31, 32) are arranged on a clutch plate (30). 4. Clutch according to claim 3, characterized in that the clutch plate (30) is arranged centrally between the two pressure plates (11, 21). 5. Clutch according to one of claims 1 to 4, characterized by a housing (40), which surrounds the two friction discs (10, 20) and / or the two pressure plates (11, 21). 6. Clutch according to claim 5, characterized in that the housing (40) has radial holes (44). 7. Clutch according to one of claims 1 to 6, characterized by a housing (40), which compensates for the driving forces of two springs (13, 22; 13 ';13'',22'';13a''', 13b ''',22a''', 22b ''') drive always assigned to a pressure plate (11, 21). 8. Clutch according to one of claims 1 to 7, characterized in that the first of the two pressure plates (11, 21) is pressed in the unloaded state against the corresponding clutch surface (31). 9. Clutch according to claim 8, characterized in that the first of the two pressure plates (11, 21) is pressed against the friction disk (10) by means of a plate spring (12). 10. Clutch according to one of claims 1 to 9, characterized in that the second of the two pressure plates (11, 21) allows the friction disc (20) to rotate freely in the unloaded state. 11. Clutch according to one of claims 1 to 10, characterized in that the friction discs (10, 20) are connected with two shafts (1, 2) arranged concentrically. 12. Clutch according to one of claims 1 to 11, characterized by at least one friction disc (10, 20), which can be routed. 13. Clutch according to claim 12, characterized in that the friction disc is constructed elastic in the radial direction. 14. Clutch according to claim 12 or 13, characterized in that the friction disk (10, 20) has holes (24) provided in an area of the friction disk (10, 20), which rigidly joins the liner in the direction of rotation of friction with the corresponding shaft (1, 2). 15. Clutch according to one of claims 12 to 14, characterized in that the friction disc (10, 20) has areas (18, 23) directed in the axial direction. 16. Clutch according to one of claims 1 to 15, characterized in that the lining of the first of the two friction discs (10, 20) is softly constructed and that the lining of the second of the two friction discs (10, 20) is build hard. 17. Clutch according to claim 16, characterized in that the soft friction disc (10) is engaged in action with a shaft (1) for a first gear and / or for a reverse gear. 18. Clutch according to one of claims 1 to 17, characterized by at least one spring (13, 22; 13 ';13'',22'';13a''', 13b ''',22a''', 22b ''') drive, which has both internally in the radial direction, and also externally in the radial direction at least one lever arm (13a, 13b). 19. Clutch according to claim 18, characterized in that an additional mass (13b) is provided on the lever arm (13b) located externally in the radial direction. 20. Clutch according to one of claims 1 to 19, characterized by a disengagement unit (50) with two clutch bearings (51, 52; 51 ', 52'), which can be activated separately and always cooperating with one of the two plates (10, 20) pressure. 21. Clutch according to claim 20, characterized in that at least one bearing (51, 52; 51 ', 52') is hydraulically actuated. 22. Clutch according to claim 20 or 21, characterized in that at least one clutch bearing (51, 52; 51 ', 52') is engaged in action with an electric actuator. 23. Clutch according to one of claims 20 to 22, characterized in that at least a first disengagement bearing (51, 52; 51 ') is arranged externally radially to the second disengagement bearing (51, 52; 52'). 24. Clutch according to one of claims 20 to 23, characterized in that the disengagement unit (50) is arranged coaxial with at least one shaft (1, 2). 25. Clutch according to one of claims 20 to 24, characterized in that the disengagement bearings (51, 52) are subjected in the activated state to opposing forces. 26. Clutch according to one of claims 20 to 25, characterized in that at least one bearing (51, 52; 51 ', 52') is engaged in action with a spring (13, 22; 13 ';13'',22'';13a''', 13b ''',22a''', 22b '''), which is constructed in such a way that in the unloaded state it acts against the bearing (51, 52; 51', 52 ') of disengagement with a retention force, preferably with the retention force of a hydraulic drive for the disengaged bearing (51, 52; 51', 52 '). 27. Clutch according to one of claims 1 to 26, characterized in that between the first of the two springs (13, 22; 13 ';13'',22'';13a''', 13b ''',22a''',22b''') of drive, preferably a lever arm (13b) of the drive spring (13), and the first of the two pressure plates (10) is provided with a drive element, preferably an element Disengaged 28. Clutch according to claim 27, characterized in that the drive element comprises at least one disengagement rod (14) preferably arranged axially between the spring (13, 22; 13 ';13'',22'';13a''',13b''', 22a ''',22b''') and the pressure plate (10). 29. Clutch according to claim 28, characterized in that the actuating element has several disengagement rods (14) joined together by means of a clamping ring (16). 30. Clutch according to one of claims 1 to 29, characterized in that a first pressure plate (10) is connected, by means of at least one spring (17) of a tangential crossbow, with a housing (40), at the same time, that the tangential leaf spring (17) exerts a force opposite to a disengagement force. 31. Clutch according to one of claims 1 to 30, characterized by a disengagement unit (50) with a symmetrical rotating coupling (55) in relation to a rotation axis of the clutch. 32. Clutch according to claim 31, characterized in that the coupling fitting (55) comprises at least one coupling element (54) for connection with at least one disengagement bearing with an actuator. 33. Coupling element for a clutch disengagement unit, preferably according to one of claims 31 or 32, characterized by a symmetrical rotation cavity relative to the axis of rotation of the clutch. 34. Coupling element according to claim 33, characterized in that in the cavity at least one connecting element (57) is provided for joining at least one disengaged bearing (51, 52; 51 ', 52') with an actuator . 35. Arrangement formed by a clutch disengagement unit, respectively a clutch and a corresponding coupling element (56), characterized by at least one groove (57) running in one of the construction groups formed by the unit (50) of disengagement and / or the coupling element (56), which is connected with a cavity (54) of the other construction group (56) formed by the disengagement unit (50) and / or the coupling element (56), so that there is a connection between an actuator and a disengaged bearing (51, 52; 51 ', 52'). 36. Procedure for mounting a clutch in which, before fixing a clutch housing (40), a unit (50) of the friction disc is provided disengaged behind a spring (13, 13 ', 13' ', 13a' '', 13b '' ', 22a '' ', 22b' ''). 37. Method according to claim 36, characterized in that the disengagement unit (50) joins, after its arrangement behind the spring (13, 13 ', 13'',13a''', 13b ''',22a''',22b'''), with a coupling element (56).