Abstract:
Multi-speed transmission in planetary design, in particular an automatic transmission for a motor vehicle, comprising one drive shaft and one output shaft, which are arranged in a housing, four planetary sets, in each case comprising at least one sun gear, one planetary carrier and one ring gear, along with at least six shifting elements, comprising a first brake, a second brake and a third brake and a first clutch, a second clutch and a third clutch, the selective meshing of which brings about different transmission ratio relationships between the drive shaft and the output shaft, such that at least nine forward gears and one reverse gear can be realized, whereas the planetary carrier of the second and fourth planetary sets is arranged in a manner radially offset to the planetary carriers of the second and the fourth planetary gear sets.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates generally to a multi-speed transmission, with which nine forward gears and one reverse gear can be shifted, and which has four planetary sets. 
       BACKGROUND 
       [0002]    DE 10 2008 000 429 A1 provides a transmission. 
         [0003]    The previously known transmission fulfills a wide range of requirements placed on modern multi-speed transmissions. In particular, the transmission may be manufactured with low construction costs, since a relatively small number of elements is required for the formation of the transmission; however, this enables a sequential shifting operation, with which double gearshifts are avoided, such that, during gearshifts in defined gear groups, only one shifting element is changed. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention is directed to a multi-speed transmission, which features at least nine forward gears and at least one reverse gear with a sufficient transmission ratio, but which, compared to the transmission conforming to this type, is able to be produced with a transmission length that is smaller in the direction of the drive axle. Moreover, the present subject matter may provide a multi-speed transmission that can be used, in particular, as a hybrid transmission and/or for which the integration of an e-machine and/or a hybrid module with an e-machine, torsion damper system and motor-separating clutch does not unduly increase the transmission length. 
         [0005]    Accordingly, the present subject matter proposes a multi-speed transmission in planetary design, which features a drive axle and an output axle, which are arranged in a housing. Furthermore, at least four planetary sets and six power-shifting elements comprising brakes and clutches are provided, the selective meshing of which brings about different transmission ratio relationships between the drive and the output, such that at least nine forward gears and one reverse gear can be realized. 
         [0006]    Preferably, the four planetary sets are formed as negative planetary gear sets, thus in each case comprising at least one sun gear, one ring gear, one planetary gear and one planetary carrier. Whereas the sun gear, the ring gear and the planetary carrier are rotatably mounted either rigidly or around a common axis. The at least one planetary gear is rotatably arranged on the planetary carrier, whereas the axis of rotation of the planetary gear is formed in a manner that is fixed relative to the planetary carrier and parallel to the common axis of the planetary carrier, the sun gear and the ring gear. Preferably, a plural number of planets are arranged on the planetary carrier. The planetary gear or planetary gears mesh both with the sun gear and with the ring gear. 
         [0007]    Moreover, one or more of the planetary sets may be formed as a positive planetary set, whereas one positive planetary set features at least one first planetary gear and one second planetary gear, whereas the first planetary gear meshes with the sun gear and the second planetary gear meshes with the ring gear. Thereby, the first planetary gear meshes in the second planetary gear. 
         [0008]    Preferably, the planetary carriers of the second and the fourth planetary set are arranged radially to the direction of the drive axle, offset to the planetary carriers of the first and the third planetary gear sets. In addition, the axes of rotation of the planetary carriers of the second and fourth planetary set are radially offset to the axes of rotation of the first and fourth planetary sets. The dimensions of the transmission in the axial direction of the drive axle are reduced by the offset, whereby the transmission can also be fitted in more compact installation spaces. 
         [0009]    Preferably, the first, third, and fourth planetary set are arranged in the axial direction of the drive shaft in the order of first, third and fourth planetary set or fourth, third and first planetary set. The second planetary set is preferably arranged either between the first and the third planetary set or above the first planetary set, thus on the side of the first planetary set turned away from the drive axle, or on the side of the first planetary set turned away from the third planetary set. 
         [0010]    This offset arrangement enables the provision of additional installation space at the entrance of the drive axle and the integration there of additional components, such as a clutch and/or an electric motor. 
         [0011]    Preferably, the drive shaft is connectable through the first clutch to the sun gear of the first planetary set, the sun gear of the first planetary set is connectable through the first brake to the housing, the ring gear of the first planetary set is connected to the sun gear of the second planetary set, the planetary carrier of the first planetary set is connected to the planetary carrier of the second planetary set and the ring gear of the third planetary set, the ring gear of the first planetary set and the sun gear of the second planetary set is connectable through a third clutch to the drive shaft, the ring gear of the second planetary set is connected to the housing and the sun gear of the third planetary set is connectable through a third brake to the housing. 
         [0012]    With the characteristic that two or more elements are connected to each other, it is particularly understood that the two or more elements feature the same rotational speed, and it is particularly preferable that the two or more elements are connected to the same shaft in a torque-proof manner. 
         [0013]    With the characteristic that two or more elements are connectable to each other, it is particularly understood that such elements are detachable from each other, and it is particularly preferable that they are connected to each other by a shifting element. 
         [0014]    The special design of the transmission enables a particularly cost-efficient transmission, by which nine forward gears and one reverse gear are enabled. 
         [0015]    Preferably, the planetary carrier of the third planetary set is connected to a first idler gear, and is connectable through a second clutch to the drive shaft, whereas the first idler gear meshes in the sun gear of the fourth planetary set. Thereby, the idler gear may be arranged firmly on the shaft or formed in one piece with the shaft, which connects the planetary carrier of the third planetary set with the second clutch. In particular, the idler gear may feature the same rotational speed as the planetary carrier of the third planetary gear set. The idler gear may be formed as a spur gear, but also as a bevel gear, worm gear or any other form of gear wheel. 
         [0016]    Moreover, a torque can be transferred from the planetary carrier of the third planetary set to the sun gear of the fourth planetary set through a chain, a belt or the like. 
         [0017]    Preferably, the planetary carrier of the fourth planetary set is connected to the output shaft. Thereby, the output shaft may be arranged in a manner radially offset to the drive shaft, such that the transmission is especially suitable for installation transverse to the main axis of the vehicle. 
         [0018]    Furthermore, the ring gear of the fourth planetary set may be connected through an idler gear to the sun gear of the third planetary set, and may be connectable through the idler gear and the third brake to the housing. 
         [0019]    The output shaft may be equipped with an output gear. Thereby, such an output gear may be a gear wheel, such as a spur gear, but even a gear that enables the transfer of a torque by means of a belt, friction wheel, etc. 
         [0020]    Preferably, the second clutch is arranged in the axial direction between the third and the first planetary sets. Whereas the axial direction is perpendicular to the main direction of propagation of the drive axle. 
         [0021]    Although all shifting elements can be formed as frictional shifting elements or as claw shifting elements, the third clutch and/or the third brake are particularly suitable for formation as a claw shifting element. Since claw shifting elements typically feature a higher efficiency in the transmission of torque, the efficiency of the transmission is increased through the use of a claw shifting element. 
         [0022]    In a specific embodiment, the second brake or the third brake may be formed as start-up elements. 
         [0023]    In an additional embodiment, the third clutch and the second brake may be designed as start-up elements. 
         [0024]    With “start-up element,” an electric motor may be particularly understood. 
         [0025]    In particular, nine gears can be realized in the multi-speed transmission, whereas the first gear arises through the locking of the third clutch and the second and third brakes, the second gear arises through the locking of the first and third brakes and the third clutch, the third gear arises through the locking of the third brake and the first and third clutches, the fourth gear arises through the locking of the third brake and the second clutch and one of the shifting elements of the first brake, second brake, first clutch and third clutch, the fifth gear arises through the locking of the first to third clutches, the sixth gear arises through the locking of the first brake and the second and third clutches, the seventh gear arises through the locking of the second brake and the second and third clutches, the eighth gear arises through the locking of the first and second brakes and the second clutch and the ninth gear arises through the locking of the second brake and the first and second clutches. 
         [0026]    Preferably, for a change from one gear into the next higher gear, only one shifting element must be open and one shifting element must be locked. 
         [0027]    The reverse gear may arise through the closing of the second and third brakes and the first clutch. 
         [0028]    In addition, the transmission in accordance with the invention is designed in such a manner that adaptability to the various drive train arrangements is enabled, both in the direction of the power flow and in spatial terms. The multi-speed transmission in accordance with the invention is particularly suitable for installation in passenger vehicles with front-transverse motorization and a driven front axle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    Additional details and advantages of the present invention arise from the following description of an embodiment in conjunction with the drawing. The following is shown in this: 
           [0030]      FIG. 1 : a schematic view of an exemplary embodiment of a multi-speed transmission in accordance with the invention and 
           [0031]      FIG. 2 : a shifting diagram for the example of a multi-speed transmission shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    Reference will now be made to embodiments of the invention, one of more examples of which are shown in the drawings. Each embodiment is provided by way of explanation of the invention, and not as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be combined with another embodiment to yield still another embodiment. It is intended that the present invention include these and other modifications and variations to the embodiments described herein. 
         [0033]      FIG. 1  shows a multi-speed transmission in accordance with an exemplary embodiment of the invention with a drive shaft  1  and an output shaft  2 , which are arranged in a housing G, whereas the output shaft  4  is arranged in a manner offset to the axis to the drive shaft  1 . Four planetary sets P 1 , P 2 , P 3  and P 4  are provided, whereas the first and the second planetary sets P 1 , P 2  are designed as negative planetary sets and form a shiftable upstream gear set, and whereas the third and the fourth planetary gear sets P 3 , P 4  form the main gear set. 
         [0034]    As shown in  FIG. 1 , six shifting elements (i.e., a first brake  03 , a second brake  05  and a third brake  07  along with a first clutch  13 , a second clutch  16  and a third clutch  18 ) are provided. The spatial arrangement of the shifting elements may be arbitrary, and is limited only by the dimensions and the external shaping. In particular, in addition to the arrangement shown of the second clutch  16  in an axial direction in front of all planetary sets P 1 , P 2 , P 3  and P 4 , the second clutch  16  may also be arranged in an axial manner between the upstream gear set P 1 , P 2  and the main gear set P 3 , P 4 . Furthermore, in addition to the arrangement shown of the third brake  07 , such third brake  07  may connect the shaft  9  to the housing G. 
         [0035]    With the previously described shifting elements  03 ,  05 ,  07 ,  13 ,  16 ,  18 , a selective shifting of nine forward gears and one reverse gear can be realized. 
         [0036]    The exemplary embodiment shown features a total of nine rotating shafts (i.e., a first shaft  1 , a second shaft  2 , a third shaft  3 , a fourth shaft  4 , a fifth shaft  5 , a sixth shaft  6 , a seventh shaft  7 , an eighth shaft  8  and a ninth shaft  9 ). 
         [0037]    With the exemplary embodiment shown of the multi-speed transmission in accordance with  FIG. 1 , the bars of the first and the second planetary sets P 1 , P 2  are coupled to each other through the fourth shaft, which is connected to the ring gear of the planetary set P 3  of the main gear set, whereas the ring gear of the first planetary set P 1  is coupled with the sun gear of the second planetary set P 2  through the eighth shaft  8 , which is detachably connectable to the drive shaft  1  through the third clutch  18 . 
         [0038]    Furthermore, the sun gear of the first planetary set P 1  is also attachable to the housing G of the transmission by means of the third shaft  3  through the first brake  3 , and is detachably connectable to the drive shaft  1  through the first clutch  13 . With the exemplary embodiment shown, the first clutch  13  and the first brake  03  feature a common multi-disk carrier. The ring gear of the second planetary set P 2  is attachable to the housing G of the transmission by means of the fifth shaft  5  through the second brake  05 . 
         [0039]    With the exemplary embodiment shown according to  FIG. 1 , the sixth shaft  6  is, through an idler gear  10 , constantly connected to the ring gear of the fourth planetary set P 4  and the bar of the third planetary set P 3 , and is detachably connectable to the drive shaft  1  through the second clutch  16 . The seventh shaft  7  is constantly connected to the sun gear of the third planetary set P 3  and, through the ninth shaft  9 , is constantly connected to the ring gear of the fourth planetary set P 4 , and is attachable to the housing G of the transmission through the third brake  07 . The output takes place through the output shaft  2  constantly connected to the bar of the fourth planetary set P 4 . 
         [0040]    Accordingly, the idler gear  10  and the fourth planetary set P 4  are provided in a coaxial manner to the output shaft  2  formed as an intermediate shaft, which carries a fixed gear  11  as the output gear. 
         [0041]      FIG. 2  shows an exemplary shifting diagram of the exemplary embodiment of a multi-speed transmission shown in  FIG. 1 , whereas it is assumed that the third clutch  18  and the third brake  07  are designed as claw shifting elements (i.e., as claw clutches or claw brakes). For each gear, three shifting elements are locked. As an example, the respective transmission ratios i of the individual gears and the gear steps or progressive steps φ to be determined from these can be seen in the shifting diagram. 
         [0042]    The first gear arises through the locking of the third clutch  18  along with the second and third brakes  05 ,  07 , the second gear arises through the locking of the first and third brakes  03 ,  07  along with the third clutch  18 , the third gear arises through the locking of the third brake  07  and the first and third clutches  13 ,  18  and the fourth gear arises through the locking of the third brake  07  and the second clutch  16 , whereas, optionally, another one of the shifting elements (for example, the first clutch  13  in this case) is locked. However, instead of the first clutch  13 , the third clutch  18  or the first brake  03  or the second brake  05  may likewise be easily locked. In all cases, only one shifting element is to be actuated when shifting from third to fourth gear, or from fourth to fifth gear, as the case may be. 
         [0043]    The fifth gear, which is formed as a direct gear, is obtained through the locking of the first, second and third clutches  13 ,  16 ,  18 ; the sixth gear is obtained through the locking of the first brake  03  along with the second and third clutches  16 ,  18 . With locked second and third clutches  16 ,  18 , and the locking of the second brake  05 , the seventh gear is obtained. The eighth gear arises through the locking of the first and second brakes  03 ,  05  and the second clutch  16 , and the ninth gear arises through the locking of the second brake  05  and the first and second clutches  13 ,  16 . As is also shown in the shifting diagram in accordance with  FIG. 2 , the reverse gear arises through the locking of the second and third brakes  05 ,  07  and the first clutch  13 . 
         [0044]    The shifting matrix presented in  FIG. 2 , in particular the transmission ratios and gear jumps shown therein, arise through the steel transmission ratio of the four planetary sets P 1 , P 2 , P 3 , and P 4  of −2, −1.5, −2.64 and −2.64, respectively. 
         [0045]    Given the fact that the second brake  05  and the third brake  07  are locked in a first forward gear and in the reverse gear, such shifting elements designed as frictional shifting elements may be used as start-up elements. In addition or as an alternative, the drive shaft can be separated by a coupling element of a drive motor. It is also possible to arrange an external start-up element behind the transmission in the direction of the power flow. With this alternative design, the drive shaft is typically firmly connected to the crankshaft of the motor. 
         [0046]    It is also possible to provide additional freewheels at each suitable location of the multi-speed transmission, for example between one shaft and the housing, or, if applicable, in order to connect two shafts. 
         [0047]    In accordance with exemplary aspects of the invention, an axle differential and/or a distributor differential may be arranged on the input side or on the output side. 
         [0048]    Within the framework of an advantageous additional form, if necessary, the input shaft  1  may be separated from the drive motor by a coupling element, whereas a hydrodynamic converter, a hydraulic clutch, a dry starting clutch, a wet starting clutch, a motor separating clutch, a magnetic powder clutch or a centrifugal clutch may be used as the coupling element. It is also possible to arrange such a start-up element in the direction of the power flow behind the transmission, whereas, in this case, the input shaft  1  is constantly connected to the crankshaft of the motor. 
         [0049]    The multi-speed transmission in accordance with exemplary aspects of the invention also allows for the arrangement of a torsional vibration damper between the motor and the transmission. 
         [0050]    Within the framework of an additional exemplary embodiment of the invention that is not shown, a wear-free brake, such as a hydraulic retarder or an electric retarder or the like, may be arranged at each shaft, preferably at the input shaft  1  or the output shaft  2 ; this is of particular importance for use in commercial vehicles. Furthermore, a power take-off may be provided to drive additional power units at each shaft, preferably at the input shaft  1  or the output shaft  2 . 
         [0051]    The frictional shifting elements that are used may be formed as power-shifting clutches or brakes. In particular, force-fitting clutches or brakes, such as multi-disk clutches, band brakes and/or cone clutches, may be used. 
         [0052]    An additional advantage of the multi-speed transmission presented here is that an electric motor can be installed at each shaft as a generator and/or as an additional drive motor. 
         [0053]    Modifications and variations can be made to the embodiments illustrated or described herein without departing from the scope and spirit of the invention as set forth in the appended claims. 
       REFERENCE SIGNS 
       [0000]    
       
           1  Drive shaft 
           2  Output shaft 
           3  Third shaft 
           4  Fourth shaft 
           5  Fifth shaft 
           6  Sixth shaft 
           7  Seventh shaft 
           8  Eighth shaft 
           9  Ninth shaft 
           10  Idler gear 
           11  Fixed gear 
           03  First brake 
           05  Second brake 
           07  Third brake 
           13  First clutch 
           16  Second clutch 
           18  Third clutch 
         P 1  First planetary set 
         P 2  Second planetary set 
         P 3  Third planetary set 
         P 4  Fourth planetary set 
         i Transmission ratio 
         φ Progressive step 
         G Housing