Abstract:
A multi-speed planetary transmission includes a housing, a drive shaft connectable to a drive train for transferring a drive torque from the drive train to the multi-speed planetary transmission, and four single planetary transmissions arranged along a housing longitudinal axis. The planetary gears feature a sun gear, ring gear, and planetary carrier. Six shift elements are arranged within the housing and are designed as four clutch elements and two brakes. Connecting shafts form connections between the single planetary transmissions, the drive shaft, the output shaft, the clutch elements and/or the brakes. The single planetary transmissions are shiftable such that nine forward gears and one reverse gear are provided, and the shift elements are arranged in a manner easily accessible from outside the housing.

Description:
FIELD OF THE INVENTION 
     The invention relates to a multi-speed planetary transmission, in particular an automatic transmission for a motor vehicle. Such a transmission is arranged, for example, in a motor vehicle between a drive and the drive wheels. Such a multi-speed planetary transmission features several single planetary transmissions, which can be shifted with each other by means of shift elements in the form of clutches and/or brakes. 
     BACKGROUND 
     A multi-speed planetary transmission frequently uses shift elements that are hydraulically actuated. If such shift elements are arranged inside the transmission, in particular moving relative to the transmission housing, the hydraulic lines must feature transits to a rotating component. A loss of pressure often arises in such transitions, such that the pressure inside the hydraulic line must be actively maintained. This happens, for example, through a hydraulic pump. The same applies when using electrically, pneumatically or mechanically actuating shift elements. 
     SUMMARY OF THE INVENTION 
     A task of the invention is to provide a multi-speed planetary transmission that features a very high proportion of easily accessible shift elements. Additional objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     To solve the tasks, a multi-speed planetary transmission in accordance with the invention includes shift elements, which are designed as four clutches and two brakes, and are easily accessible. At the same time, the multi-speed planetary transmission features four single planetary transmissions arranged between a drive shaft and an output shaft. Each single planetary transmission comprises a sun gear, a ring gear and several planetary gears allocated to each bar (i.e., each planetary carrier). 
     The multi-speed planetary transmission may be advantageously designed in standard design, such that the drive shaft and the output shaft are arranged coaxially in the housing. Alternatively, it is also possible to design the multi-speed planetary transmission in front-transverse design, such that the output shaft may be arranged in a manner axially offset to the drive shaft. 
     The drive shaft may be designed to be connectable through the drive clutch to the drive train of the motor vehicle. The drive clutch is designed in particular as a hydrodynamic torque converter, a hydrodynamic clutch, an additional start-up clutch, an integrated start-up clutch, an integrated start-up brake or an additional electric motor. As a whole, the multi-speed planetary transmission in accordance with the invention is characterized by reduced construction or installation expenses. Both the costs and the weight of the multi-speed planetary transmission are reduced. 
     Advantageous embodiments of the multi-speed planetary transmission arise from the characteristics of the transmission described and claimed herein. 
     An arrangement by which the clutch elements are arranged on the outer shafts, in particular on the drive shaft and/or on the output shaft, is advantageous. The outer shafts can be reached particularly from the outside, such that, when required, access to all clutch elements is possible with little effort. 
     According to an additional advantageous arrangement, the fourth clutch is arranged on the output shaft, and is thus easily accessible from the outside. 
     According to an additional advantageous arrangement, the single planetary transmissions are connectable by means of shift elements in such a manner that the multi-speed planetary transmission features a good transmission ratio series. 
     According to an additional advantageous arrangement, it is ensured that that, when there is a shift between two adjacent gears, and in particular upon a shift from the first forward gear to the reverse gear and vice versa, in each case, exactly one previously locked shift element is open, and exactly one previously open shift element is locked. 
     According to an additional advantageous arrangement, each of the single planetary transmissions is designed as a so-called “negative planetary transmission.” This means that the respective stationary transmission ratio of the respective single planetary transmission has a negative value. It is thereby achieved that the coaxially arranged central gears, thus the inner sun gear and the outer ring gear arranged concentrically to it, feature opposite directions of rotation. According to an additional advantageous arrangement, at least one of the negative planetary transmissions is designed as a so-called “positive planetary transmission.” For example, this is possible by the fact that, with one single planetary transmission, the connection of the bar and the ring gear is exchanged, and at the same time the amount of the stationary transmission ratio is increased by the value of 1. 
     According to an additional advantageous arrangement, the arrangement of the single planetary transmissions in the housing, in particular along the drive shaft and/or output shaft, is variable. This means that the geometrical position of the respective single planetary transmissions, in particular their order along the drive shaft and/or output shaft, is freely selectable. Simultaneously or alternatively, the shift elements, with respect to their geometrical position in the housing, can be arranged in a manner that is freely selectable. 
     According to an additional advantageous embodiment, the connecting shafts, the drive shaft and/or the output shaft are each connected to the housing and/or to each other by means of a freewheel element. Thereby, additional degrees of freedom for the interconnection of the single planetary transmissions and their coupling in the housing arise. 
     According to an additional advantageous arrangement, a drive may be attached at the connecting shaft, the drive shaft and/or the output shaft. The additional drive may be configured, for example, as an electric motor. It is also conceivable to use other power and/or drive sources as the drive. 
     According to an additional advantageous arrangement, the shift elements are designed as frictional-locking and/or positive-locking. 
     According to an additional advantageous embodiment, the second brake, the second clutch element, and the fourth clutch element are designed as claw-shift elements. Based on the characteristics of the multi-speed planetary gear set, the design of the specified shift elements as claw-shift elements leads to significantly reduced fuel consumption. 
     Both the characteristics specified in the claims and the characteristics specified in the following embodiments of the device in accordance with the invention are, by themselves alone or in combination with each other, suitable for providing additional forms in accordance with the invention. In terms of the additional forms, the particular combinations of characteristics do not represent a limitation; rather, they are essentially solely of an exemplary nature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Additional characteristics, advantages and details of the invention arise from the following description of embodiments with reference to the drawing. The following is shown: 
         FIG. 1  is a first embodiment of a multi-speed planetary transmission, 
         FIG. 2  is a shifting matrix for illustrating the shift elements to be locked for a respective gear, 
         FIG. 3  is a second embodiment of a multi-speed planetary transmission in accordance with  FIG. 1  with a modified arrangement of the shift elements, and 
         FIG. 4  is a third embodiment of a multi-speed planetary transmission in accordance with  FIG. 1  with a different arrangement of the shift elements. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to embodiments of the invention, one or 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. 
     In  FIGS. 1 to 4 , parts that correspond to each other are provided with the same reference signs. Moreover, details of the embodiments explained in more detail below may, in and of themselves, present an invention or be part of an object under the invention. 
       FIG. 1  schematically represents a multi-speed planetary transmission  1 . The multi-speed planetary transmission  1  is designed in particular as a transmission for a motor vehicle. 
     In  FIG. 1 , the multi-speed planetary transmission  1  is represented in simplified form by the fact that it represents solely one part of the multi-speed planetary transmission  1  arranged above in respect of a transmission longitudinal axis  2 . 
     The multi-speed planetary transmission  1  features a housing  3 . Six shift elements, i.e. a first clutch  4 , a second clutch  5 , a third clutch  6 , and a fourth clutch  7 , along with a first brake  8  and a second brake  9 , are arranged within the housing  3 . Furthermore, the multi-speed planetary transmission features a drive shaft  10  for transferring a drive torque from a drive on the multi-speed planetary transmission  1  that is not shown. Accordingly, the multi-speed planetary transmission  1  features an output shaft  11 . The drive shaft  10  and the output shaft  11  are arranged coaxially with respect to the housing longitudinal axis  2 . Both the drive shaft  10  and the output shaft  11  are respectively led out of the housing  3 . 
     The multi-speed planetary transmission also features four planetary gear sets  12  to  15  arranged along the housing longitudinal axis  2 . In accordance with the presentation in  FIG. 1 , the first planetary gear set  12 , the second planetary gear set  13 , the third planetary gear set  14  and the fourth planetary gear set  15  are arranged along a reference direction  16 , which is oriented from the input shaft  10  to the output shaft  11  parallel to the transmission longitudinal axis  2 . 
     The first brake  8  and the second brake  9  are firmly arranged on an inner wall of the housing  3 . Furthermore, the first clutch  4 , the second clutch  5  and the third clutch  6  are arranged directly next to each other along the reference direction  16 . With the embodiment shown, the three clutches  4  to  6  feature a common outer multi-disk carrier  17 . The clutches  4 ,  5  and  6  are arranged on the outer drive shaft  10 . The fourth clutch  7  is also arranged on the outer output shaft  11 . 
     According to the embodiment shown, each of the planetary gear sets  12  to  15  features an inner, externally toothed sun gear, an outer, internally toothed ring gear that is arranged in particular concentrically to the transmission longitudinal axis  2  along with several planetary gears, each of which features a bar, arranged between the sun gear and the ring gear. Depending on the size of the multi-speed planetary transmission, the number of planetary gears may vary. Accordingly, the first planetary gear set  12  comprises a sun gear  18 , a ring gear  19  and at least one planetary gear  21  featuring a bar  20  (also known as a planetary carrier. Accordingly, the second planetary gear set  13  comprises a sun gear  22 , a ring gear  23  and at least one planetary gear  25  with a bar  24 . The third planetary gear set  14  comprises a sun gear  26 , a ring gear  27  and at least one planetary gear  29  with a bar  28 . The fourth planetary gear set  15  comprises a sun gear  30 , a ring gear  31  and at least one planetary gear  33  with a bar  32 . 
     In the following, an interconnection of the planetary gear sets  12  and  15  by means of the shift elements  4  to  9  along with the connection of the planetary gear sets  12  and  15  to the drive shaft  10  and the output shaft  11  are explained in detail. 
     The drive shaft  10  is connectable through the first clutch  4  to the bar  28  of the third planetary gear set  14 . The drive shaft  10  is connectable through the second clutch  5  to the ring gear  19  of the first planetary gear set  12 . At the same time, the drive shaft  10  is connectable through the second clutch element  5  to the sun gear  22  of the second planetary gear set  13 . The drive shaft  10  is connectable through the third clutch  6  to the sun gear  18  of the first planetary gear set  12 . At the same time, the drive shaft  10  is connectable through the third clutch element  6  to the first brake  8 . 
     The output shaft  11  is connected to the ring gear  27  of the third planetary gear set  14 . The output shaft is connectable through the fourth clutch element  7  to the bar  32  of the fourth planetary gear set  15 . 
     The bar  20  of the first planetary gear set  12  is connected to the bar  24  of the second planetary gear set  13 . The ring gear  23  of the second planetary gear set  13  is connected to the second brake  9 . The bar  24  of the second planetary gear set  13  is connected to the ring gear  31  of the fourth planetary gear set  15 . The bar  24  of the second planetary gear set  13  is connected to the sun gear  26  of the third planetary gear set  14 . 
     The sun gear  30  of the fourth planetary gear set  15  is connected through an eighth connection shaft  41  to the housing  3 . 
     The first planetary gear set  12  features a preferred stationary transmission ratio of i 0 =−1.898, the second planetary gear set  13  features one of i 0 =−1.609, the third planetary gear set  14  features one of i 0 =−1.500 and the fourth planetary gear set  15  features one of i0=−1.500 i 0    
       FIG. 2  shows a shifting matrix for the gears G to be shifted. The gears are designed, in ascending order in the shifting matrix, beginning with the first gear G 1  up to the ninth gear G 9  and a reverse gear R. For example, it can be read from the shifting matrix that, for the realization of the first gear G 1 , the second brake  9 , the second clutch  5  and the fourth clutch  7  must be in a locked shifting position. Furthermore, the shifting matrix discloses a transmission ratio i at each gear. Moreover, a respective gear jump j is presented in the shifting matrix. For example, the gear jump j between the first gear G 1  and the second gear G 2  amounts to 1.709. Such numerical value corresponds to the relationship of the transmission ratio of the first gear, i.e. 4.348, to the transmission ratio of the second gear G 2 , i.e. 2.545. 
     In the last three rows of the shifting matrix, alternative shifting configurations for realizing the fourth gear G 4  are presented with G 4   a , G 4   b  and G 4 C. As a general rule, for the gears G 1  to G 9  and R, it applies that, with a shift of gears between two adjacent gears, in each case, exactly one previously locked shift element is open, and exactly one previously open shift element is locked. This means that two shift elements are always simultaneously locked. In particular, with the alternative gear arrangements G 4   a  and G 4   b , this principle is suspended, since, upon an upshift from the third gear G 3  to (for example) the first alternative fourth gear G 4   a , the second clutch  5  and the third clutch  6  must be open and at the same time the first clutch  4  and the first brake  8  must be locked. 
     Independent of this, the alternative fourth gears G 4   a  to G 4   c  feature an identical transmission ratio i of 1.267. This means that an alternative shifting position for the fourth gears G 4   a  to G 4   c  will not lead to a change of the gear jumps j, in particular between the third and fourth gear and the fourth and fifth gear. 
     The individual numerical values for the transmission ratios i and the gear jumps j arise directly from the shifting matrix in accordance with  FIG. 2 , to which reference is hereby made. 
       FIG. 3  shows an embodiment of an additional multi-speed planetary transmission. The multi-speed planetary transmission is differentiated from the multi-speed planetary transmission  1  in accordance with  FIG. 1  by a modified arrangement of the clutches. The second clutch  5  and the third clutch  6  are arranged and correspondingly interconnected on the drive shaft  10  analogously to the multi-speed planetary transmission  1 . Furthermore, the fourth clutch  7  is arranged and interconnected at the output shaft  11  identically to the multi-speed planetary transmission  1  in accordance with  FIG. 1 . However, in contrast to the multi-speed planetary transmission  1  in accordance with  FIG. 1 , the first clutch element  4   a  is not arranged on the drive shaft  10 , but is arranged on the output shaft  11 , and enables a connection of the output shaft  11  through the fourth connecting shaft  37  to the ring gear  27  of the third planetary gear set  14 . 
     All clutches  4   a ,  5 ,  6 ,  7  are arranged on the outer shafts  10 ,  11 . The brakes  8 ,  9  are fixed to the housing  3 . All shift elements  4   a ,  5  to  9  are easily accessible from outside. 
       FIG. 4  shows an embodiment of an additional multi-speed planetary transmission. The multi-speed planetary transmission in accordance with  FIG. 4  is differentiated from the multi-speed planetary transmission  1  in accordance with  FIG. 1  by the fact that the first clutch  4   b  is not arranged directly on the drive shaft  11 , but is arranged on the seventh connecting shaft  40 . Accordingly, through the seventh connecting shaft  40 , the first clutch  4   b  enables a connection of the bar  38  of the second planetary gear set  13  to the sun gear  26  of the third planetary gear set  14 . 
     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 
     
         
         
           
               1  Multi-speed planetary transmission 
               2  Transmission longitudinal axis 
               3  Housing 
               4  First clutch 
               4   a  First clutch 
               4   b  First clutch 
               5  Second clutch 
               6  Third clutch 
               7  Fourth clutch 
               8  First brake 
               9  Second brake 
               10  Drive shaft 
               11  Output shaft 
               12  First single planetary transmission 
               13  Second single planetary transmission 
               14  Third single planetary transmission 
               15  Fourth single planetary transmission 
               16  Reference direction 
               17  Multi-disk carrier 
               18  Sun gear 
               19  Ring gear 
               20  Bar 
               21  Planetary gear 
               22  Sun gear 
               23  Ring gear 
               24  Bar 
               25  Planetary gear 
               26  Sun gear 
               27  Ring gear 
               28  Bar 
               29  Planetary gear 
               30  Sun gear 
               31  Ring gear 
               32  Bar 
               33  Planetary gear 
               34  First connecting shaft 
               35  Second connecting shaft 
               36  Third connecting shaft 
               37  Fourth connecting shaft 
               38  Fifth connecting shaft 
               39  Sixth connecting shaft 
               40  Seventh connecting shaft 
               41  Eighth connecting shaft 
               42  Multi-speed planetary transmission 
               43  Multi-speed planetary transmission 
               44  Ninth connecting shaft 
             G Gears 
             i Transmission ratio 
             j Gear jump