Abstract:
A double clutch transmission with two clutches connected to a drive shaft and to one of two transmission input shafts. Fixed gears are coupled to the input shafts and engage idler gears. Several coupling devices connect the idler gears to a countershaft which have an output gear that couple gears of an output shaft such that at least seven power shift forward gears and at least one reverse gear can be shifted, and four gear wheel planes are positioned in a way that at least one power shift winding-path gear can be shifted via the shifting device.

Description:
This application is a National Stage completion of PCT/EP2008/063438 filed Oct. 8, 2008, which claims priority from German patent application serial no. 10 2007 049 266.0 filed Oct. 15, 2007. 
     FIELD OF THE INVENTION 
     The present invention relates to a double clutch transmission for a motor vehicle. 
     BACKGROUND OF THE INVENTION 
     Known from the publication DE 103 05 241 A1 is a 6-speed or 7-speed dual clutch transmission. The dual clutch transmission comprises two clutches, each connected with their inputs to the drive shaft and with their output to one of the two transmission input shafts. The two transmission input shafts are coaxially positioned each other. In addition, two countershafts are arranged to be axially parallel to the transmission input shafts, their idle gears mesh with the fixed gear wheels of the transmission input shafts. Furthermore, coupling devices that are axially movable and arranged on the countershaft in a rotationally fixed manner to shift the respective gear wheels. Each selected ratio is transferred by the drive gear wheels to a differential transmission. To achieve the desired gear ratio steps in this known double clutch transmission, a vast number of gear planes are required, so that a significant amount of installation space is needed. 
     In addition, a spur gear change speed transmission is known through the publication DE 38 22 330 A1. The spur gear change speed transmission comprises a double clutch, that is shiftable under power, where one part is connected with a drive shaft and the other part with a hollow drive shaft, rotatably supported on the drive shaft. For certain gear ratios, the drive shaft can be coupled with the hollow drive shaft via a shifting device. 
     Known from the publication DE 10 2004 001 961 A1 is a power transmission with two clutches, each of which are assigned to a partial transmission. The transmission input shafts of the two partial transmissions are positioned coaxial to each other and mesh, via fixed gear wheels, with idle gears of the designated countershaft. The respective idle gears of the countershafts can be connected, in a rotationally fixed manner, with the respective countershaft via designated shifting devices. The particular idle wheels of the countershaft can be connected via the assigned shifting devices with the associated countershaft in a rotationally fixed manner. A double clutch transmission is known from this publication, which absolutely requires at least six gear planes. Hence, the needed spatial installation requirement, in axial direction, increases with such transmission, so that the installation options are significantly limited with such known transmission. 
     SUMMARY OF THE INVENTION 
     It is the task of this present invention, to propose a double clutch transmission as in the previously described type, in which the power shiftable gear ratio steps are realized with the least spatial installation requirement, secondly, the transmission shall need only few component parts, hereby keeping the manufacturing cost for the transmission low. 
     Thus, a double clutch transmission with just five gear planes in the partial transmissions is realized, whereby the two partial transmissions can be coupled via at least one additional shifting device, to enable winding-path gears. Hereby, the proposed double clutch transmission realizes as few gear planes as possible, but providing a maximum number of transmission ratios, whereby preferably all forward gears and reverse gears are power shiftable in sequential mode. 
     The gear wheels of both partial transmissions are coupled with each other as a winding-path gear, to enable a flow of force through both partial transmissions. The respective shifting device which is used serves to couple idle gears and establish a dependency between transmission input shafts. Independently of the particular embodiment of the double clutch transmission, the configuration of the shifting devices for the coupling of two particular idle gears can be varied, so that the shifting element does not need to be positioned necessarily between the idle gears which need to be coupled. 
     Because of the low number of required gear planes, a short, axial configuration length is required for the proposed transmission, which enables also a front-transversal implementation into motor vehicles. Due to the fact that the inventive double clutch transmission also provides winding-path gears, and because of the three-shaft configuration, the multi-use of particular gear pairs or gear wheels, respectively, is enabled, which leads to a reduction of parts of the transmission. 
     In the proposed double clutch transmission, in accordance with the invention, gear planes can be provided, as a so-called dual gear plane and/or single gear plane. In a dual gear plane, an idle gear on the countershafts is each assigned to a fixed gear wheel of a transmission input shaft. To the contrary, in a single gear plane, just one idle gear on a countershaft is assigned to a fixed gear wheel of a transmission input shaft. Due to the fact that, in each dual gear plane, one idle gear can be used for at least two gears, the possible multi-use idle gears enables the realization of a certain number of gear ratios with less gear planes. Hence, the physical length of the transmission can be reduced. 
     For the use of single gear planes, in which just one idle gear on a countershaft is assigned to the fixed gear wheel of a transmission input shaft, a free range of the transmission ratios is possible. 
     The winding-path gears can be realized through several gear pairs or gear planes, respectively, so that additional gears can be shifted via the particular gear pairs or gear planes, respectively of the winding-path gears. 
     The proposed gear planes, in accordance with the inventive double clutch transmission, provide a gear set configuration to obtain at least seven forward gears and at least one reverse gear ratio, whereby at least one winding-path gear can be realized in the first gear step and/or can be shifted in one of the reverse gears can. Also additional winding-path gears can be shifted as the second up to the seventh gear, or also as reverse gear, whereby the seventh gear, depending on the sixth gear, can be power shifted. All forward gears and reverse gears should be, in sequential design, power shiftable. Non-power shiftable winding-path gears can be configured as intermediate gears, in which the transmission takes place between the ratios of two main drive gears, as overdrive gears or speed gears in which the gear ratio is smaller then the smallest gear ratio of the main drive gear (6 th  gear), as an off-road gear or low speed gear in which the gear ratio in each case is larger than the gear ratio of the first gear, and/or as additional reverse gears. 
     The power shiftable reverse gears, in the inventive double clutch transmission, are realized through just one additional arrangement or through just one additional gear wheel whereby and at least, through the additional gear plane, which reverses the rotation, a reverse gear can be realized as winding-path gear, and another reverse gear can be realize directly via the gear plane. The gear ratios of the reverse gears can, for instance, be varied by adding an additional step gear or similar. 
     Within the scope of an embodiment variation of the present invention, it can be provided that the four gear planes are realized through maximal two fixed gear wheels on each transmission input shaft, which mesh, for instance, with a maximum of four or less idle gears on the countershafts. Other constructions of embodiments are possible to realize the four gear planes. 
     In this embodiment variation, at least seven power shift forward gear and several reverse gear ratios can be realized, whereby at least the first gear can be configured as a winding-path gear and one of the reverse gears can be configured as a winding-path gear. The additional shifting device which is realized as the winding-path gears, is positioned in this embodiment variation on the first countershaft, between the second and the third gear plane. Other configuration options are also possible and additional shifting devices can be applied. The first reverse gear can be realized, as a winding-path gear, via the same clutch as the first gear. The second reverse gear can be arranged on the other clutch to be power shfited. 
     Another variation of the invention can provide that at least seven power shift forward gears and two reverse gear ratios can be realized, whereby at least a first gear is configured as a winding-path gear and the second reverse gear is configured as a winding-path gear. 
     Within the scope of and additional embodiment variation of the present invention and contrary to the previously described embodiment variation, an additional shifting device is provided to couple the partial transmissions on the second countershaft between the second and third gear planes. In this embodiment variation, at least seven power shift forward gears and one reverse gear are realized. The reverse gear is preferably configured as a winding-path gear. 
     To connect the idle gears in a rotationally fixed manner, for the individual gear ratio steps with the respective countershaft, dual action coupling devices are provided, for instance, between the third gear plane and the fourth gear plane on at least one of the countershafts. In addition, a single action coupling device can be positioned at least on one of the countershafts. The coupling devices can comprise, for instance, hydraulic actuated clutches or also interlocking claw clutches, as well as any kind of synchronization device. It is also possible to replace a dual action coupling device by two single action coupling devices and, vice versa. 
     It is possible to vary the presented configuration options, and also the number of the gear wheels as well as the number of the coupling devices can be altered, to realize further load or non-load shiftable gears, to realize installation space savings and the use of lesser parts in the proposed double clutch transmission. In addition, the respective configuration positioned of the coupling devices in the gear plane can be varied. Furthermore, also the operating direction of the coupling devices can be altered or extended, respectively. 
     Independent of the particular embodiment variation of the double clutch transmission, the drive shaft and the output shaft, preferably, do not need to be positioned coaxially to each other, which realizes especially an installation space saving configuration. For instance, shafts, which are spatial positioned one after the other, can also have a slight offset to each other. In that configuration, a direct gear with the transmission ratio one can be realized via gear meshing, and can, in an advantageous way, can be freely shifted to the fifth, the sixth, or the seventh gear. Other configuration options of the drive shaft and the output shaft are also possible. 
     The proposed double clutch transmission is preferably equipped with an integrated output stage. The output stage can comprise an output gear, a fixed gear wheel on the output shaft, which mesh is with a fixed gear wheel on the first countershaft, as well as with a fixed gear wheel on the second countershaft. 
     Advantageously, the lower forward gears and the reverse gears can be activated through a starting, or shifting clutch, to hereby concentrate higher loads on this clutch and to construct the second clutch with less need for installation space and as more cost-effective. Especially, the gear planes in the proposed double clutch transmission can be positioned in a way that one can start, through the inner transmission input shaft or through the outer transmission input shaft, hereby always a starting through the more appropriate clutch, which is also possible in a concentrically positioned, radial interlaced construction of the double clutch. Hereby and accordingly, the gear planes can be positioned as mirror-symmetric, or swapped, respectively. It is also possible to swap the countershafts or positioned them in a mirroring way. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Following, the present invention is further explained based on the drawings. It shows: 
         FIGS. 1 and 1A  a schematic view of the first embodiment of a 7-gear double clutch transmission with an exemplary shifting scheme; 
         FIGS. 2 and 2A  a schematic view of a second embodiment variation of the inventive 7-gear double clutch transmission with an exemplary shifting scheme; and 
         FIGS. 3 and 3A  a schematic view of a third embodiment variation of the inventive 7-gear double clutch transmission with an exemplary shifting scheme. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An inventive 7-gear double clutch transmission comprises two clutches K 1 , K 2 , the input sides of which are connected to a drive shaft w_an. Also, a torsion vibration damper  16  can be mounted on the drive shaft w_an. The output sides of the clutches K 1 , K 2  are each connected with one of two transmission input shafts w_K 1 , w_K 2 , which are arranged coaxial to each other. The first transmission input shaft w_K 1  is designed as a solid shaft and the second transmission input shaft w_K 2  is designed as hollow shaft. In addition, countershafts w_vorlege 1 , w_vorgelege 2  are provided which are positioned to be axial-parallel to each other. The coupling of the two transmission input shaft w_K 1  and w_K 2  takes place by way of a shifting device H via tooth meshing, so that the transmission input shafts w_K 1  and w_K 2  are coupled together. 
     Only four gear planes are provided in the 7-gear dual clutch transmission. In the first embodiment variation, in accordance with  FIG. 1 , the four gear planes  01 - 05 ,  02 - 13 ,  03 - 06 ,  04 - 07  are each realized via the fixed gear wheels  12 ,  13 ;  14 ,  15  of the two transmission input shafts w_K 1 , w_K 2  and by way of the four idle gears  01 ,  02 ,  03 ,  04  on the first countershaft w_vorgelege  1 , as well as through the idle gears  05 ,  06 ,  07  on the second countershaft w_vorgelege  2 . 
     In the embodiment variation, in accordance with  FIG. 1 , the first gear plane  01 - 05  and the third gear plane  03 - 06 , as well as the fourth gear plane  04 - 07  are each designed as dual gear plane. The second gear plane  02 - 13 , however, is designed as single gear plane. 
     In the first gear plane  01 - 05 , the fixed gear wheel  12  on the second transmission input shaft w_K 2  meshes with the idle gear  01  on the first countershaft w_vorgelege  1 , and with the idle gear  05  on the second countershaft w_vorgelege  2 . The second gear plane  02 - 13  comprises the fixed gear wheel  13  on the second transmission input shaft w_K 2 , which only meshes with the idle gear  02  on the first countershaft w_vorgelege  1 . Hence, the fixed gear wheel  13  on the second transmission input shaft w_K 2  meshes in the second gear plane  02 - 13  only with the idle gear  02 . Hereby, the advantage of a more free transmission gear selection arises, in contrast to gear planes with dual side engagement of the fixed gear wheel. 
     The third gear plane  03 - 06  comprises the fixed gear wheel  14  on the first transmission input shaft w_K 1  which meshes with the idle gear  03  on the first countershaft w_vorgelege  1 , and with the idle gear  06  on the second countershaft w_vorgelege  2 . 
     Finally, in the fourth gear plane  04 - 07 , the fixed gear wheel  15  on the first transmission input shaft w_K 1  meshes with the idle gear  07  on the second countershaft w_vorgelege  2 , also with an idle gear  17  on an intermediate shaft w_zw, the fixed gear wheel  15  on the first transmission input shaft w_K 1  and also the idle gear  04  on the first countershaft w_vorgelege  1 . Hereby, a reversal of rotation can be achieved to realize the reverse gears RA 1 , RA 2 , RB 1 . It is also possible to design the idle gear  17  as a step gear. For the reversal of rotation, the idle gear  04  on the first countershaft w_vorgelege  1  can also mesh with the idle gear  07  on the second countershaft w_vorgelege  1 , so that the idle gear  17  can be omitted. 
     In this proposed gear set configuration, on the first countershaft w_vorgelege  1 , dual action coupling devices A-B, C-D are each provided between the first gear plane  01 - 05  and the second gear plane  02 - 13 , between the third gear plane  03 - 06  and the fourth gear plane  04 - 07 . Also on the second countershaft w_vorgelege  2 , a dual action coupling device F-G is positioned, between the third gear plane  03 - 06  and the fourth gear plane  04 - 07 . In addition, a single action coupling device E is positioned on the second countershaftw_vorgelege  2 , on the side which is facing away from the clutch K 1 , K 2 . 
     To realize winding-path gears, meaning to enable coupling of both partial transmissions, the additional shifting device H is positioned on the first countershaft w_vorgelege 1 , between the second gear plane  02 - 10  and the third gear plane  03 - 06 . 
     The table, which is presented in  FIG. 1A , shows an exemplary shifting scheme for the first embodiment variation of the 7-gear dual clutch transmission. 
     In accordance with the shifting schemes in  FIG. 1A , the first forward gear  1  is shifted via the first clutch K 2  and via the coupling device F-G, shifted the direction G, as well as via the activated shifting device H, as a winding-path gear. The second forward gear  2  is realized via the first clutch K 1  and via the coupling device F-G, shifted in the direction G, the third forward gear  3  is shifted via the second clutch K 2  and via the coupling device A-B, shifted in the direction B. The fourth forward gear for is again shifted via the clutch K 1  and via the coupling device C-D, shifted in the direction C, whereby the fifth gear  5  is realize via the second clutch K 2  and via the coupling device A-B, shifted in the direction A. Finally, the sixth forward gear  6  is shifted via the first clutch K 1  and via the coupling device F-G, shifted in the direction F, whereby the seventh forward gear  7  is shifted via the second clutch K 2  and via the coupling device E on the second countershaft w_vorgelege  2 . The first reverse gear RA 1  is shifted via the second clutch K 2  and via the coupling device C-D, shifted in the direction D. the second reverse gear RA 2  and the alternative first reverse gear RB 1  are each shifted via the first clutch K 1  and via the coupling device C-D, shifted in the direction D. 
     Thus, the first forward gear  1  arranged as a winding-path gear, using the gear wheels  13 ,  02 ,  03 ,  14 ,  07 , and  10 . The second forward gear  2  uses the gear wheels  15 ,  07 , and  10 , whereby the gear wheels  13 ,  02 , and  09  are used to realize the third forward gear  3 . The fourth forward gear  4  uses the gear wheels  14 ,  03 , and  09 , whereby the fifth forward gear  5  uses the gear wheels  12 ,  01 , and  09 , whereby the sixth forward gear  6  uses the gear wheels  14 ,  06 , and  10 . Finally the seventh forward gear  7  uses the gear wheels  12 ,  05 , and  10 . For the first reverse gear RA 1  engaged as a winding-path gear, the gear wheels  13 ,  02 ,  03 ,  14 ,  15 ,  17 ,  04 , and  09  are used. For the second reverse gear RA 2 , the gear wheels  15 ,  17 ,  04 , and  09  are used, whereby the same gear wheels are used for the alternative first reverse gear RB 1   
     Other assignment configurations of the particular gear steps in this embodiment variation, in regard to the clutches, are also possible. Especially with mirror image, for instance, a reversed assignment configuration can easily be realized. 
     In the second embodiment variation, in accordance with  FIG. 2 , the four gear planes  01 - 05 ,  02 - 06 ,  03 - 07 ,  04 - 15  are each realized through two fixed gear wheels  12 ,  13 ;  14 ,  15  on the two transmission input shafts w_K 1 , w_K 2  and through four idle gears  01 ,  02 ,  03 ,  04  on the first countershaft w_vorgelege  1 , three idle gears  05 ,  06 ,  07  on the second countershaft w_vorgelege  2 . 
     In the embodiment variation, in accordance with  FIG. 2 , the first gear plane  01 - 05  and the second gear plane  02 - 06 , as well as the third gear plane  03 - 07  are each designed as dual gear planes. In contrary, the fourth gear plane  04 - 15  is designed as a single gear plane. 
     In the first gear plane  01 - 05 , the fixed gear wheel  12  of the second transmission input shaft w_K 2  meshes with the idle gear  01  on the first countershaft w_vorgelege  1 , and with the idle gear  05  on the second countershaft w_vorgelege  2 , as it is provided in the first embodiment variation. 
     Contrary to the first embodiment variation, the second gear plane  02 - 06  comprises the fixed gear wheel  13  on the second transmission input shaft w_K 2 , which meshes with the idle gear  02  on the first countershaft w_vorgelege  1 . Also, the idle gear  17  on an intermediate shaft w_zw meshes with the fixed gear wheels  13  on the second transmission input shaft w_K 2 , and with the idle gear  06  on the second countershaft w_vorgelege  2 . Hereby, a reversal of rotation can be achieved to realize the reverse gears R 1  and R 2 . It is also possible to design the idle gear  17  as a step gear. For the reversal of rotation, the idle gear  06  on the second countershaft w_vorglege  2  can also mesh with the idle gear  02  on the first countershaft w_vorgelege  1 , so that the idle gear  17  can be omitted. 
     The third gear plane  03 - 07  comprises the fixed gear wheels  14  on the first transmission input shaft w_K 1 , which meshes with the idle gear  03  on the first countershaft w_vorgelege  1 , with the idle gear  07  on the second countershaft w_vorgelege  2 . 
     Finally, in the fourth gear plane  04 - 15 , the fixed gear wheels  15  on the first transmission input shaft w_K 1  only meshes with the idle gear  04  on the first countershaft w_vorgelege  1 . Hereby, the advantage of a more free transmission gear selection arises, in contrast to gear planes with dual side arrangement of the fixed gear wheel. 
     In this proposed gear set configuration, a dual action coupling devices A-B, C-D are each provided, on the first countershaft w_vorgelege  1 , between the first gear plane  01 - 05  and the second gear plane  02 - 06 , and between the third gear plane  03 - 07  and the fourth gear plane  04 - 15 . On the second countershaft w_vorgelege  2 , a dual action coupling device E-F is positioned between the first gear plane  01 - 05  and the second gear plane  02 - 06 . In addition, a single action coupling device G is positioned on the second countershaft w_vorgelege  2 , on the side which is facing away from the clutches K 1 , K 2 , of the third gear plane  03 - 07 . 
     The table, which is presented in  FIG. 2A , shows an exemplary shifting scheme for the first embodiment variation of the 7-gear dual clutch transmission. 
     In accordance with the shifting schemes in  FIG. 2A , the first forward gear  1  is shifted via the second clutch K 2  and via the coupling device G on the second countershaft w_vorgelege  2 , shifted in the direction G, and via the activated shifting device H, as a winding-path gear. The second forward gear  2  is realized via the first clutch K 1  and via the coupling device G on the second countershaft w_vorgelege  2 , shifted in the direction G, the third forward gear  3  is shifted via the second clutch K 2  and via the coupling device A-B, shifted in the direction B. The fourth forward gear for is again shifted via the first clutch K 1  and via the coupling device C-D, shifted in the direction C, whereby the fifth forward gear  5  is realized via the second clutch K 2  and via the coupling device E-F, shifted in the direction E. Finally, the sixth forward gear  6  is shifted via the first clutch K 1  and the coupling device-D, shifted in the direction D, whereby the seventh forward gear  7  is again shifted via the second clutch K 2  and via the coupling device A-B, shifted in the direction A. The first reverse gear R 1  is shifted via the second clutch K 2  and via the coupling device E-F, shifted in the direction F. The second reverse gear R 2  is shifted via the first clutch K 1  and via the coupling device E-F, shifted in the direction F, as well as via the activated shifting device H as a winding-path gear. 
     Thus, the first forward gear  1  is engaged, as a winding-path gear using the gear wheels  13 ,  02 ,  03 ,  14 ,  07 , and  10 . In the second forward gear  2 , the gear wheels  14 ,  07 , and  10  are used, the gear wheels  13 ,  02 , and  09  are used to realize the third forward gear  3 . In the fourth forward gear  4 , the gear wheels  14 ,  03 , and  09  are used, in the fifth forward gear  5  the gear wheels  12 ,  05 , in  10  are used, the sixth forward gear  6  uses the gear wheels  15 ,  04 , and  09 . Finally, the seventh forward gear  7  uses the gear wheels  12 ,  01 , and  09 . The first reverse gear R 1  uses the gear wheels  13 ,  17 ,  06 , and  10 , the second reverse gear R 2  is engaged as a winding-path gear, using the gear wheels  14 ,  03 ,  02 ,  13 ,  17 ,  06 , and  10 . 
     Other assignment configurations of the particular gear steps in this embodiment variation, in regard to the clutches, are also possible. Especially through mirroring, for instance, a reversed assignment configuration can easily be realized. 
     In contrast to the first and the second embodiments variation, the additional shifting device H, in the third embodiment variation in accordance with  FIG. 3 , is provided on the second countershaft w_vorgelege  2  for the coupling of the two partial transmissions, between the second gear plane  02 - 06  and the third gear plane  03 - 07 . Another difference is an additional idle gear  08  which is positioned on the second countershaft w_vorgelege  2 . This idle gear  08  expands the fourth gear plane  04 - 08  in a way, that the fixed gear wheels  15  on the first transmission input shaft w_K 1  meshes with the idle gear  04  on the first countershaft w_vorgelege  1  as well as with the idle gear  08  on the second countershaft w_vorgelege  2 . Contrary the second embodiment variation, the single action coupling device G, in the third embodiment variation, is positioned on the second countershaft w_vorgelege  2 , on the side which is facing away from the clutches of the fourth gear plane  04 - 08 . 
     The third gear plane  03 - 07  also provides that the fixed gear wheels  14  and the idle gear  07  on the second countershaft w_vorgelege  2 , and also an idle gear  17  on an intermediate shaft w_zw, mesh with, the fixed gear wheel  14  with the idle gear  07  on the second countershaft w_vorgelege  2 , as well as with idle gear  03  of the first countershaft w_vorgelege  1 . In this case, a rotation reversal can be provided to realize the reverse gear R 1 . It is also possible, that the idle gear  17  is designed as a step gear. The provide the rotation reversal, the idle gear  07  on the second countershaft w_vorgelege  2  meshes with the idle gear  03  on the first countershaft w_vorgelege  1 , so that the idle gear  17  can be omitted. 
     In the embodiment variation, in accordance with  FIG. 3 , all gear planes  01 - 05 ,  02 - 06 ,  03 - 07 , and  04 - 08  are designed as dual gear planes. 
     The table, which is presented in  FIG. 3A , shows an exemplary shifting scheme for the first embodiment variation of the 7-gear dual clutch transmission. 
     In accordance with the shifting schemes in  FIG. 3A , the first forward gear  1  is shifted via the second clutch K 2  and via the coupling device A-B, shifted in the direction B. The second forward gear  2  is realized via the first clutch K 1  and via the coupling device C-D, shifted into the direction C, the third forward gear  3  is shifted via the second clutch K 2  and via the coupling device E-F, shifted in the direction F. The fourth forward gear  4  is again shifted via the first clutch L 1  and via the coupling device C-D, shifted in the direction D, whereby the fifth forward gear  5  is realized via the second clutch K 2  and via the coupling device A-B, shifted in the direction A. Finally, the sixth forward gear  6  is shifted via the first clutch K 1  and via the coupling device G on the second countershaft w_vorgelege  2 , whereby the seventh forward gear  7  is again shifted via the second clutch K 2  and via the coupling device E-F, shifted in the direction E. The reverse gear R 1  is shifted via the second clutch K 2  and via the, shifted into the direction C, coupling device C-D, as well as via the shifting device H as a winding-path gear. 
     Thus, the first forward gear  1  uses the gear wheels  13 ,  02 , and  09 . The second forward gear  2  uses the gear wheels  14 ,  03 , and  09 , the gear wheels  13 ,  0 , and  10  are used to realize the third forward gear  3 . For the fourth forward gear  4 , the gear wheels  15 ,  04 , and  09  are used, the fifth forward gear  5  uses the gear wheels  12 ,  01 , and  09 , the sixth forward gear  6  uses the gear wheels  15 ,  08 , and  10 . Finally, the seventh forward gear  7  uses the gear wheels  12 ,  05 , and  10 . The reverse gear R 1  uses, as a winding-path gear, the gear wheels  13 ,  06 ,  07 ,  14 ,  17 ,  03 , and  09 . 
     Other assignments for the particular gear steps, in regard to clutches, are also possible in this embodiment variation. Especially, and for instance through mirroring, a reversed assignment can easily be realized. 
     In the above described embodiment variations, the direction into which the coupling devices are shifted, to connect a particular idler gear wheel with the respective countershaft, can be altered by a modifying the coupling devices, for instance, through particular deflection devices. 
     REFERENCE CHARACTERS 
     
         
         
           
               01  Idler gear wheel on the first Countershaft 
               02  Idler gear wheel on the first Countershaft 
               03  Idler gear wheel on the first Countershaft 
               04  Idler gear wheel on the first Countershaft 
               05  Idler gear wheel on the second Countershaft 
               06  Idler gear wheel on the second Countershaft 
               07  Idler gear wheel on the second Countershaft 
               08  Idler gear wheel on the second Countershaft 
               09  Fixed gear wheel on the first Countershaft as Output Stage 
               10  Fixed gear wheel on the second Countershaft as Output Stage 
               11  Fixed gear wheel on the Output Shaft 
               12  Fixed gear wheel on the second Transmission Input Shaft 
               13  Fixed gear wheel on the second Transmission Input Shaft 
               14  Fixed gear wheel on the first Transmission Input Shaft 
               15  Fixed gear wheel on the first Transmission Input Shaft 
               16  Torsion Vibration Damper 
             K 1  First Clutch 
             K 2  Second Clutch 
             w_an Drive Shaft 
             w_ab Output Shaft 
             w_vorgelege 1  first Countershaft 
             w_vorgelege  2  second Countershaft 
             A-B dual action Coupling Device 
             C-D dual action Coupling Device 
             E single action Coupling Device 
             E-F dual action Coupling Device 
             F-G dual action Coupling Device 
             G single action Coupling Device 
             H additional Shifting Device 
             i Gear Transmission Ratio 
             phi Transmission Ratio Spread 
               1  First Forward Gear 
               2  Second Forward Gear 
               3  Third Forward Gear 
               4  Fourth Forward Gear 
               5  Fifth Forward gear 
               6  Sixth Forward Gear 
               7  Seventh Forward Gear 
             RA 1  First Reverse Gear 
             RA 2  Second Reverse Gear 
             RB 1  alternative first Reverse Gear 
             R 1  first Reverse Gear 
             R 2  second Reverse Gear 
             w_zw Intermediate Shaft 
               17  Idler gear wheel on the Intermediate Shaft