Abstract:
A gear mechanism for motor vehicles includes a double clutch gear mechanism with two part gear mechanisms and a double clutch which transmits torque from the engine optionally to one of the two part gear mechanisms, with a central disk connected to a drive disk, two outer pressure application plates which are also connected to the drive disk and are moveable in the axial direction relative to the central disk, and friction disks arranged between the central disk and the pressure application plates, wherein the friction disks consist of two support carrier disks arranged parallel to each other and moveably in relation to each other, between which leaf-like spring segments are provided. To eliminate vibration problems which can occur on start-up from standstill, on load-change processes and during the gear change, the leaf-like spring segments have different spring characteristic curves with which a multistage spring characteristic is achieved.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to a gear mechanism for motor vehicles, in particular to a double clutch gear mechanism with two part gear mechanisms and a double clutch, which transmits torque from the engine optionally to one of the two part gear mechanisms. 
     2. Description of the Prior Art 
     Double clutch gear mechanisms, which are mainly concerned here, are automatic gear mechanisms which allow a fully automatic gear change without power interruption by means of two part gear mechanisms. The gear mechanism control selects the gears automatically or at the driver&#39;s request within the limits of the permitted speed ranges. Torque is transmitted via one of the two clutches which connect the two part gear mechanisms optionally with the engine. When one clutch closes, the other opens. 
     Such double clutches, in particular dry double clutches, often suffer from noise and vibration problems which mainly occur during creep processes, on start up from standstill, on load change procedures and during gear changes. The main problems here are gear rattle, start-up grab and selection impacts during the gear change. 
     U.S. Pat. No. 4,697,683 discloses a clutch in which the two friction disks consist of two support carrier disks arranged parallel to each other, between which a single-stage lining spring system is provided. The disadvantages described above also arise with these clutches. 
     SUMMARY OF THE INVENTION 
     A gear mechanism for motor vehicles includes a double clutch gear mechanism with two part gear mechanisms and a double clutch which transmits torque from the engine optionally to one of the two part gear mechanisms, with a central disk connected to a drive disk, two outer pressure application plates which are also connected to the drive disk and are moveable in the axial direction relative to the central disk, and friction disks arranged between the central disk and the pressure application plates, wherein the friction disks consist of two support carrier disks arranged parallel to each other and moveably in relation to each other, between which leaf-like spring segments are provided. To eliminate vibration problems which can occur on start-up from standstill, on load-change processes and during the gear change, the leaf-like spring segments have different spring characteristic curves with which a multistage spring characteristic is achieved. 
     The gear mechanism effectively prevents gear rattle, start-up grab and the occurrence of selection impacts due to leaf-like spring segments, arranged between the support carrier disks, having different characteristic curves so that a multistage spring characteristic can be achieved. 
     The lining spring system in conjunction with an electronic control, in particular double dry clutches display an entirely new harmonic behavior. 
     By means of the multistage spring characteristic, substantially three coupling regions are created: a first coupling region with a gear rattle damping, a second coupling region with a bite point control and creep control, and a third coupling region for the part- and full-load operations. 
     In a refinement of the system, by means of the multistage spring characteristic, five phases can even be optimized: a load point region in which no or very little moment is transmitted (0 to around 1 Nm), an anti-rattle region (around 1 to around 5 Nm), a creep region (around 5 to around 10 Nm), a part-load region (around 10 to around 25 Nm), and a full-load region (over 50 Nm). 
     The multistage spring characteristic can be achieved in various ways by corresponding selection of the spring segments. 
     For example the spring segments, which suitably consist of undulating steel plates, can be given different plate thicknesses and/or alternately different spring characteristics. 
     Alternatively the spring segments can be formed integrally and have a progressive characteristic curve. 
     A further variant provides that the spring segments are formed as double packets in series connection with different characteristic curves. 
     Furthermore it is possible to form the spring segments as double packets in parallel connection with different characteristic curves. 
     In addition the spring segments can be formed alternately as double packets and single springs. 
     Furthermore the spring segments can have different contact regions which come to rest successively on the respective counter-surface, wherein the spring segments of the one group retain a distance from the counter-surface in the decoupled state. 
     The spring segments are suitably established on the support carrier disks by means of rivets. 
     An advantageous embodiment comprises a carrier plate being arranged on at least one side between the respective support carrier disk and the spring segments. 
     The gear mechanism with the clutches described can be used both for automatic and for manual gear mechanisms with just one gear train. In particular the invention is suitable for double clutch gear mechanisms with two part gear mechanisms and a dry double clutch which transmits the torque from the engine optionally to one of the two part gear mechanisms. In this application the respective passive drive train is used for gear rattle damping. 
     The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
         FIG. 1  is a section though the upper part of an exemplary embodiment of a double clutch, 
         FIG. 2  is the same section through a second exemplary embodiment of a double clutch, 
         FIG. 3  is the same section through a third exemplary embodiment of a double clutch, 
         FIG. 4  is the same section through a fourth exemplary embodiment of a double clutch, 
         FIG. 5  is a section through the upper region of a clutch disk, and to the right thereof, a front view thereof, 
         FIG. 6  shows the construction of the lining spring system of the clutch disk, 
         FIG. 7  shows a lining spring system with individual segments—one stage, 
         FIG. 8  shows a lining spring system with double segments—two stages, 
         FIG. 9  shows a drive carrier disk with spring segments—one stage, 
         FIG. 10  shows an intermediate plate spring system—one stage, 
         FIG. 11  shows a lining spring characteristic—one stage, 
         FIG. 12 a    shows a comparison of a lining spring characteristic compared with a two-stage characteristic (first stage linear, second stage progressive), 
         FIG. 12 b    shows a three-stage lining spring characteristic (first stage linear, second stage slightly progressive, third stage highly progressive), 
         FIG. 12 c    shows a four-stage lining spring characteristic (first stage linear, second stage slightly progressive, third stage more progressive, fourth stage highly progressive), 
         FIGS. 13   a/b  shows a first embodiment of a two-stage lining spring characteristic according to  FIG. 12   a,    
         FIGS. 14   a/b  shows a first embodiment of a three-stage and four-stage lining spring characteristic according to  FIGS. 12 b    and  12   c,    
         FIGS. 15   a/b  shows a second embodiment of an at least three-stage lining spring characteristic according to  FIGS. 12 a    and  12   b,    
         FIGS. 15   c/d  shows a third embodiment of an at least two- or three-stage lining spring characteristic according to  FIGS. 12 a    and  12   b,    
         FIGS. 16   a/b  shows a second embodiment of a two-stage lining spring characteristic with strong progression in the second stage according to  FIG. 12   a,    
         FIG. 17 a    shows a third embodiment of a two-stage lining spring characteristic according to  FIG. 12   a,    
         FIG. 17 b    shows a fourth embodiment of an at least three- to four-stage lining spring characteristic according to  FIGS. 12 b  and 12 c   , and 
         FIGS. 18   a/b  shows a double clutch diagram with active drive train and passive drive train. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     According to  FIG. 1  of the drawing, a double clutch  1  substantially consists of a drive disk  2 , a central disk  3  connected thereto, pressure application plates  4  and  5  provided on both sides of the central disk  3 , and friction disks  6  and  7  arranged between the central disk  3  and the pressure application plates  4  and  5  respectively. 
     The drive disk  2  sits rotationally fixed on an input shaft  8  of the double clutch  1  and consequently rotates therewith at the same rotation speed. The input shaft  8  is normally the driveshaft or crankshaft of an engine not shown in the drawing. 
     The drive disk  2  is connected to the central disk  3  via a clutch body  13 , i.e. the central disk  3  rotates with the same rotation speed as the drive disk  2 . The pressure application plates  4  and  5  arranged on both sides of the central disk  3  rotate with the central disk  3  but are however moveable axially in relation to the central disk  3 . The central disk  3  is supported axially via a clutch bearing  19  and a cardanic thrust washer  16  and a cardanic coupling  15  on a hollow shaft  11  leading to the gear mechanism, and is radially free-running. 
     To trigger the coupling process, one of the pressure application plates  4  and  5  is moved in the direction of the central disk  3 , whereby the respective friction disk  6  or  7  is pressed firmly against the central disk  3 . 
     By the coupling of the respective friction disk  6  or  7 , this rotates with the central disk  3  and transmits the engine torque to the respective output shaft  11  or  12  of the double clutch  1  leading to the gear mechanism. 
     The output shaft  12 , which can be connected to the friction disk  6  shown on the left in the drawing, is formed as a solid shaft and, like the output shaft  11 , opens into a gear mechanism housing not shown in the drawing, where it serves to drive a first part gear mechanism. This first part gear mechanism for example serves gears 1, 3 and 5. 
     The output shaft  11 , which can be connected to the friction disk  7  shown on the right in the drawing, as a hollow shaft surrounds the solid shaft  12  and also leads into the gear mechanism housing not shown in the drawing. It serves to drive a second part gear mechanism, which for example is provided for gears 2, 4, 6 and R. 
     The output shafts  11  and  12  are each connected by form fit, via a notched toothing  20  or  21 , to the friction disks  6  and  7  via damping systems  10  and  24 . 
     The entire double clutch  1  shown in  FIG. 1  is surrounded by a clutch housing, not shown in the drawing. The axial irregularities are compensated by a lining spring system within the clutch. The radial compensation is achieved by the radial play between the central disk  3  and the cardanic thrust washer  16  and the cardanic coupling  15 . 
     According to  FIG. 2  of the drawing, the double clutch  18  substantially comprises the same basic elements as the double clutch  1  in  FIG. 1 , wherein for the individually correlating parts, the same position numerals have been used as in the exemplary embodiment in  FIG. 1 . 
     In the double clutch  18  shown in  FIG. 2 , the drive disk  2  is connected to the central disk  3  via a torsion damper  9  and a clutch body  14 , i.e. the central disk  3  rotates at the same rotation speed as the drive disk  2 . The pressure application plates  4  and  5  arranged on both sides of the central disk  3  rotate with the central disk but are however axially moveable in relation to the central disk  3 . The central disk, in contrast to the first exemplary embodiment, is supported on the hollow shaft  11  via a bearing  19  and decoupled from the input shaft. 
     The respective friction disks  6  and  7  are coupled and decoupled in the same way as in the exemplary embodiment shown in  FIG. 1 . 
     In contrast to the embodiment shown in  FIG. 1 , a pilot bearing  22  is provided between the solid shaft  12  and the engine input shaft  8 . 
     The exemplary embodiment shown in  FIG. 3  is substantially identical to the clutch design in  FIG. 1 . However a pilot bearing  22  is positioned between the solid shaft  12  and the engine input shaft  8 , as in the exemplary embodiment in  FIG. 2 . 
     The embodiment shown in  FIG. 4  corresponds substantially to the clutch variant in  FIG. 2 . This embodiment however has two damping systems  10  and  24  which are arranged between the friction disks  6  and  7  and the output shafts  11  and  12  leading to the gear mechanisms. 
       FIGS. 5 and 6  show standardized friction disk systems as used in the clutch friction disks in double clutch drives, automated gearboxes and manual gearboxes. 
     These friction disk systems are fitted with a clutch lining  25  and connected by means of lining rivets  26  to the spring segments  27 , which in turn are connected via segment rivets  28  to the drive carrier disk  29 . The drive carrier disk  29  has a hub  30  with an internal notched toothing which is formed integrally with the drive carrier disk  29  or can be connected thereto via a rivet connection. 
       FIG. 6  shows in perspective view two fundamental versions of spring segment systems. These comprise firstly a single segment  31  or a double spring segment  32 ,  34 . In both systems, at least one spring segment is connected to the drive carrier disk  29  via a segment rivet  26 . In the double spring segment system, the two single segments  32  and  34  can also be connected to the drive carrier disk. 
     Four different lining spring systems are known from the prior art:
     1) One-stage lining characteristic, single or one-segment system:
         FIG. 7  shows a single or one-segment system. Here the two clutch linings  25  are riveted on either side to the thin, curved single segments  27  by means of lining rivets  26 . The undulation of the single segments  27  or spring segments is here preferably oriented towards the side of the pressure application plates  4  and  5 . In individual cases however the undulation can also be oriented towards the side of the central disk  3 .   
       2) Two-stage lining characteristic, double segment springing system:
         FIG. 8  shows a double segment springing system. Two symmetrical double segments  32  arranged back to back, opposing in the active direction, are arranged between the clutch linings  25 . The double spring segments  32  are clamped on opposite sides and connected alternately to the lining rivets  26  so as to allow full utilization of the existing spring travel. The advantage over single segmenting is a higher spring rate. Then only half or a smaller spring travel is required to build up the same coupling capacity. However in this embodiment, the clutch reinforcement is very great, which has a disadvantageous effect on the clutch controllability.   
       3) Single-stage lining characteristic, spring segment integrated in drive carrier disk:
         FIG. 9  shows the drive carrier disk with a single segment  34 . This construction is designed for space reasons if rivet connection is not possible.   
       4) Single-stage lining characteristic, intermediate plate springing system
         FIG. 10  shows an intermediate plate springing system. Here the lining spring  36  is premounted on the drive carrier disk  29  and connected by force fit to the drive carrier disk via spring rivets  37 . The clutch lining or linings in this embodiment are riveted directly to the carrier plate  62 .   
       

     The coupling capacity is determined by the following formula:
 
 Mk=Fa*Mu*Rm*z  
 
where:
         Mk=coupling moment   Fa=pressure application force   Mu=coefficient of friction   Rm=mean friction radius   Z=number of friction surfaces       

     The pressure application force arises from the resulting spring rates connected in series, multiplied by the spring travel when the clutch is pressed. In the medium and low torque regions, the clutch lining spring dominates the pressure application force characteristic. This is shown as an example in  FIG. 11 . Three regions are illustrated there:
     1) Position 38
       Clutch creep moment from 10 Nm to 25 Nm, achieved over a spring travel of around 0.1 mm.   
       2) Position 39
       Bite point range in which no torque is transmitted, over a spring travel of around 0.05 mm.   
       3) Position 40
       Coupling point at which more than 50 Nm is transmitted over a spring travel of around 0.28 mm.   
       

     A lining spring characteristic curve shows as an example the very small spring travel band in which very high pressure application forces can be generated. If a high variability in the friction values is added, a high and also highly variable transmission function results with a high torque spread of the clutch. 
     This effect is shown in  FIG. 12 . The characteristic  44  here shows a possible transmission function with constant coefficient of friction, resulting from a small spring travel and a high spring rate of the lining springs used. To achieve a constant creep moment or bite point setting of the clutch reliably and repeatedly, a very precise travel control is required. This however causes difficulties if the coefficient of friction also varies. 
     To solve these problems, according to the invention a lining characteristic with at least two stages, up to four stages, is provided. This is depicted in  FIGS. 12 a  to 12 c   , wherein this must be matched according to the level and variability of the lining coefficient of friction. 
     The following lining spring characteristics or stages are provided:
     A) phase of gear rattle damping   B) clutch bite point and creep control   C) part-load range   D) full-load range   

     With regard to the lining spring travel, the following feature combinations are proposed:
     a) The lining spring travel is extended by around 0.5 mm compared with conventional lining spring travels. This is possible since modern friction linings are substantially more wear-resistant.   b) A gear rattle damping phase  63  is introduced in order to allow the introduction of an electronically controlled gear rattle prevention or damping system, namely for a region from 1 Nm to 5 Nm. The spring travel proposed here is 0.5 mm but this can also be varied.   c) A bite point and creep coupling moment phase  64  of 5 Nm to 25 Nm is proposed, within a lining spring travel of around 0.3 mm.   d) A part-load/start-up and operation phase  67  is introduced which is provided for operations over around 25 Nm to 50 Nm/120 Nm.   e) A full-load/start-up and operation phase  65  is introduced which is provided for coupling moments greater than around 120 Nm up to the end of the lining spring travel of the system at around 1.3 mm.   

     This entire characteristic cannot be achieved by a single lining spring characteristic curve but at least two or more spring characteristics are required. For this springs can be used in parallel connection or in series connection. 
       FIG. 12 a    illustrates a solution with the resulting spring characteristic  43  which results from the superposition of a first spring characteristic  41  and a second spring characteristic  42 , wherein the different lining spring travels are active, for example spring characteristic  42  from around 0.1 mm and spring characteristic  41  from around 0.8 mm. This solution arises from a two-stage spring characteristic, wherein the feature of this solution is that the first spring characteristic has a particularly flat characteristic curve and is used to damp the gear rattle on the passive drive path. 
     Preferably multistage solutions are used, as shown for example in  FIGS. 12 b  and 12 c   .  FIG. 12 b    shows a solution in three stages, wherein the third stage is provided for part-load and full-load operations.  FIG. 12 c    shows an optimum spring characteristic curve which is divided into four regions:
         C-Stage 1: Gear rattle damping   C-Stage 2: Clutch bite point and creep control   C-Stage 3: Part-load region   C-Stage 4: Full-load region       

     Any individual total spring characteristic curve can be achieved in the same way with lining springs which are arranged in series or parallel connection. It is also possible to combine a series and parallel connection of the lining springs. 
     Different detailed solutions are described below which lead to a two- or multistage lining spring characteristic: 
       FIG. 13 a    shows a first single segment design in which a single segment  47  with a first spring rate is attached by force fit or connected via a rivet  49  to the clutch lining. A second single element  46  with a second spring rate is connected to the clutch lining only with one clutch rivet, wherein however the connection at the second lining rivet is designed such that a distance  45  remains from the clutch lining. When the two clutch linings are pressed together, first the spring rate of the lining spring  47  is applied and on further pressing together, the spring rate of the lining spring  46  is added so that both lining springs  47  and  46  are active. This can be achieved with a total of at least three segments, preferably 3 to 6 or 4 to 8 single segments, of which in each case the first half is fitted with the first spring rate and the second half with the second spring rate. The lining springs are then positioned such that a right-angled, parallel and stable position of the clutch linings is guaranteed. The individual segments are here integrated in or riveted by force fit to the drive carrier disk  28 . 
       FIG. 13 b    shows a similar solution to  FIG. 13 a   . The difference here lies only in that the clutch lining is glued to a carrier plate  66 . In this case the carrier plate or the single segments can be connected to the drive carrier disk by force fit. 
       FIG. 14 a    shows a multistage, at least however two-stage, double segment variant in which a first double segment  51  with a specific first spring rate is attached to the clutch lining via rivets. A second double segment  52  with a second spring rate is also connected to the clutch lining by force fit. 
     In parallel to the first double segment variant, a second double segment variant is connected at a distance, in which the one element  69  has a third spring rate and the other segment  70  a fourth spring rate. 
     Both double segment variants are equipped with a stop, wherein the weaker spring characteristic curve is switched to mass in each case. When the two clutch linings are pressed together, both spring rates of lining springs  50  and  51  are then applied directly, and at a distance  45 , then the lining springs  69  and  70 . 
     Such a variant can be achieved with in total at least eight double segments, i.e. four with a distance and the first and second spring rates, and four without a distance with the third and fourth spring rates. Similarly, a 3/6 or 5/10 solution is possible. 
     The lining springs are then positioned to guarantee a right-angled, parallel and stable position of the clutch linings. The double segments are then either integrated in or riveted by force fit to the drive carrier disk  28 . 
       FIG. 14 b    shows a similar design to  FIG. 13 a   . The difference lies merely in that the clutch lining is glued to a carrier plate  66 . In this case the carrier plate and the single segments can be connected to the drive carrier disk by force fit. 
     The spring characteristics are here as follows:
         Stage 1: C-Stage 1=C1*C2/(C1+C2)   Stage 2: C-Stage 2=C1*C2/(C1+C2)+C3*C4/(C3+C4)   Stage 3: (Stop C1/C2):C-Stage 3=C2+C3*C4/(C3+C4)   Stage 4: (Stop C3/C4):C-Stage 4=C2+C4       

       FIG. 15 a    shows a second multistage segment variant in which a single segment  46  with a first spring rate is connected by force fit or riveted to the clutch lining. A second double segment  51  with a second spring rate is connected to both clutch linings. The single segment  46  is however attached by force fit to one clutch lining only with one lining rivet; on one of the two rivets, the connection is designed such that a distance  45  is present. When the two clutch linings are pressed together, first the spring rate of the double lining spring  51  is applied. When the rivet distance is then zero, both spring rates of the lining springs  51  and  46  are applied. This configuration can also achieve three spring rates in the same construction space, in that in the double segment, the two single segments have different spring rates. Thus at first, the first spring rate of the double segment  51  would act, then the spring rate of the single segment  45 , and finally the combination of the spring rate of the single segment  46  with the two spring rates of the single segments of the double segment  51 . 
     This arrangement can be achieved with a total of at least three single and double segments in a 3/6 or 4/8 configuration. The lining springs should then be positioned to guarantee a right-angled, parallel and stable position of the clutch linings. The single segments can either be integrated in or connected by force fit to the drive carrier disk  28 . 
       FIG. 15 b    shows a similar solution to  FIG. 15 a   . The difference however lies in that the clutch lining in the variant in  FIG. 15 b    is glued to a carrier plate  66 . In this case the carrier plate  66  or the single and double segments can be connected to the drive carrier disk by force fit via riveting. 
     The spring characteristics are here as follows:
         Stage 1: C-Stage 1=C1*C2/(C1+C2)   Stage 2: C-Stage 2=C1*C2/(C1+C2)+C3   Stage 3 (Stop C1/C2): C-Stage 3=C2+C3       

       FIGS. 15 c  and 15 d    show a similar solution to  FIGS. 15 a  and 15 b   . The difference here lies in the arrangement of the spring elements with the different spring characteristics:
         Stage 1: C-Stage 1=C1   Stage 2: C-Stage 2=C3*C2/(C3+C2)+C1   Stage 3 (Stop C3/C2): C-Stage 3=C1+C3       
       FIG. 16 a    shows a lining variant in which one of the two lining spring systems is formed as a double-leaf lining spring  52 . Alternatively here the lining springs shown as the single segment  47  can also be formed as double-leaf lining springs. In this design there is a possibility of achieving more than two spring rates in that different lining thicknesses or forms are used, and hence a very high spring rate progression is achieved. 
       FIG. 16 b    shows the same variant as  FIG. 16 a   , wherein however the clutch lining  48  is fitted with a carrier plate  66 . 
       FIG. 17 a    shows a further two-stage lining variant with an intermediate plate solution and/or a double segment spring with two different spring rates which are implemented on an intermediate plate  54 . This intermediate plate  54  is connected to the carrier plate  66  by force fit, for example by means of rivets  53 , and furthermore to the clutch lining via lining rivets  26 . One side of the intermediate plate  54  is in direct force-fit contact with the first clutch lining, while the other side of the intermediate plate  54  has a distance from the clutch lining. When the clutch is pressed together, first one side of the intermediate plate  54  with a first spring rate is compressed. When the distance between the intermediate plate  54  and the clutch lining  48  is zero, the second side comes into contact with the clutch lining so that the second combined spring rate is applied. In this embodiment the carrier plate or intermediate plate can be connected by force fit to the drive carrier disk. 
       FIG. 17 b    shows a multistage lining design with an intermediate plate solution and/or a double segment spring  54  with two spring rates and a second double segment spring again with two different spring rates, which are implemented in a second intermediate plate. Here the distances between the lining variants can be selected such that optionally each of the four springs rates individually or together can be connected in parallel. This has the advantage that optionally a one- to four-stage version can be selected, wherein the one-stage version can be the total spring rate C1+C2+C3+C4 and the four-stage version C1, then C1+C2, then C1+C2+C3 and then C1+C2+C3+C4. All conceivable combinations connected in parallel are possible. The arrangement can be achieved with a total of at least three single and double segments, i.e. 3/6 or 4/8 configurations. 
     The lining springs are then positioned to guarantee a right-angled, parallel and stable position of the clutch linings. The single segments can either be integrated in or riveted by force fit to the drive carrier disk  28 . 
     With reference to  FIG. 18 , a description is now given of how the invention can achieve the electronically controllable gear rattle prevention/damping: 
       FIG. 18 a    shows diagrammatically a double clutch system with a first part gear mechanism  59  together with a first clutch  55 , and a second part gear mechanism  58  with a second clutch  56 . The first part gear mechanism implements gears 1-3-5 and the second part gear mechanism gears 2-4-6. As shown in the drawing, in each case there is an active path  60  and a passive path  61 . The passive path  61  can either be presynchronized or switched neutrally via the synchronization mechanism. In the exemplary embodiment shown in  FIG. 18 a   , the second clutch  56  is switched passively. 
     Scenario 1: The passive path is pre synchronized. 
     In this case the clutch builds up a counter-moment and “clamps” the presynchronized gear wheels against each other, so they can no longer cause gear rattle. The other loose gear wheels are then given a corresponding differential rotation speed via the engaged second clutch  56 , which in turn generates a damping on the non-presynchronized gear wheel and thus damps the gear rattle. 
     Scenario 2: The passive path is not presynchronized. 
     In this case application of the passive clutch generates a rotation speed difference between the loose gear wheels and the passive input shaft, which leads to a damping of gear rattle. 
       FIG. 18 b    shows the same double clutch gear mechanism as in  FIG. 18 a   . Here however the first part gear mechanism  59  lies in the passive path  60  and the second part gear mechanism  58  in the active path  61 . The scenarios 1 and 2 mentioned above can be transferred in similar manner to the first passive part gear mechanism. 
     The use of the passive part gear mechanism as damper for the loose gear wheels described above is in principle also applicable to double dry gear mechanisms and double wet gear mechanisms. The basic requirement for such an application is that the passive path is always held under slip control and hence the passive path is shielded from engine torque irregularities. This is possible only if the coupling moment can be set precisely in the region from around 1 Nm to 10 Nm. The invention described here of the two- or multistage lining spring as a solution for gear rattle damping is indispensable. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Double clutch/system 1 
           2  Drive disk 
           3  Central disk 
           4  Pressure application plate 
           5  Pressure application plate 
           6  Friction disk 
           7  Friction disk 
           8  Input shaft 
           9  Torsion damper 
           10  Torsion damper 
           11  Output shaft (hollow shaft) 
           12  Output shaft (solid shaft) 
           13  Clutch body  1   
           14  Clutch body  2   
           15  Cardanic coupling of central disk 
           16  Cardanic thrust washer 
           17  Central disk mounted on hollow shaft  11   
           18  Double clutch/system 2 
           19  Clutch bearing 
           20  Notched toothing—clutch  1   
           21  Notched toothing—clutch  2   
           22  Pilot bearing 
           23  Bearing system/hollow shaft/solid shaft 
           24  Torsion damper 
           25  Clutch lining 
           26  Lining rivet 
           27  Spring segment  1   
           28  Segment rivet, drive carrier disk 
           29  Drive carrier disk 
           30  Hub 
           31  Single segment 
           32  Double segment 
           33  Segment lining rivet 
           34  Spring segment  2   
           35  Single disk spring segment 
           36  Premounted lining spring/drive carrier disk system 
           37  Spring rivet 
           38  Phase—creep control 
           39  Phase—low torque transmission 
           40  Phase—high torque transmission 
           41  Single lining spring characteristic  1   
           42  Single lining spring characteristic  2   
           43  Lining spring characteristic  1 + 2  overlaid 
           44  Standard lining spring characteristic 
           45  Distance of lining spring  1  from lining spring  2   
           46  Lining spring  1   
           47  Lining spring  2   
           48  Clutch lining integrated in a steel disk 
           49  Lining rivet  2   
           50  Double lining spring characteristic  1   
           51  Double lining spring characteristic  2   
           52  Double leaf lining spring 
           53  Segment rivet 
           54  Double segment spring with two spring characteristics 
           55  Clutch  1   
           56  Clutch  2   
           57  Engine rotation speed 
           58  Part gear mechanism  1   
           59  Part gear mechanism  2   
           60  Active drive train 
           61  Passive drive train 
           62  Output shaft rotation speed 
           63  Gear rattle damping phase 
           64  Creep coupling moment phase 
           65  Start-up moment phase 
           66  Carrier plate 
           67  Part-load phase 
           68  Second double segment design 
           69  Double segment spring characteristic  3   
           70  Double segment spring characteristic  4   
       
    
     In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.