Abstract:
A multi-speed transmission in which a sun gear of a fourth planetary gear set is connected with the housing in a non-rotatable manner, a ring gear of a first planetary gear set is permanently connected with a ring gear of the fourth planetary gear set, a sun gear of the first planetary gear set and a sun gear of a second planetary gear set can be coupled with the housing, via a first brake, a carrier of the first planetary gear set can be coupled with the housing, via a second brake, and the output shaft can be coupled with a carrier of the fourth planetary gear set, via a first clutch. Variations of other couplings within the multi-speed transmission forms a set of transmissions having similar properties.

Description:
[0001]    This application is a National Stage completion of PCT/EP2013/055059 filed Mar. 13, 2013, which claims priority from German patent application serial no. 10 2012 207 092.3 filed Apr. 27, 2012. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a multi-stage transmission in planetary design, in particular for a motor vehicle. 
       BACKGROUND OF THE INVENTION 
       [0003]    Such multi-stage transmissions are mainly used as automatic transmissions of motor vehicles wherein the effective power flow in the respective gear step is defined by a targeted actuation of the shift element within the planetary set. In addition, the planetary sets in an automatic transmission are usually connected with a start-up element subject to a slip effect and alternatively provided with a bypass clutch, as for example a hydrodynamic torque converter or a hydraulic clutch. 
         [0004]    A multi-stage transmission in planetary design is known from DE 10 2008 000 428 A1 in which four planetary sets as well as a total of eight rotatable shafts are disposed in a housing, of which one constitutes the input drive shaft and another the output shaft of the multi-stage transmission. Furthermore, at least six shift elements are provided in the area of the shafts, by the targeted actuation of which the power flow within the four planetary sets varies and thus different transmission ratios are definable between the input drive shaft and the output shaft. Hereby it is possible to shift into a total of nine forward gears as well as one reverse gear. 
       SUMMARY OF THE INVENTION 
       [0005]    The object of the invention is to disclose an alternative multi-stage transmission, preferably with an improved degree of efficiency and sufficiently greater and sufficiently evenly distributed transmission ratio range. 
         [0006]    The object of the invention is achieved by means of a multi-stage transmission, comprising at least four planetary sets, a housing, an input drive shaft and an output shaft, in which 
         [0007]    a sun gear of the fourth planetary gear set is connected with the housing in a rotatably fixed manner, 
         [0008]    a ring gear of a first planetary gear set is permanently connected with a ring gear of the fourth planetary gear set, 
         [0009]    a sun gear of the first planetary gear set and a sun gear of a second planetary gear set can be coupled with the housing via a first brake, 
         [0010]    a carrier of the first planetary gear set can be coupled with the housing via a second brake, 
         [0011]    the input drive shaft can be coupled with a carrier of the fourth planetary gear set via a first clutch, 
         [0012]    a carrier can be coupled with the sun gear, a ring gear with the sun gear or the ring gear with the carrier, respectively, of the second planetary gear set or the input drive shaft with the sun gear of the second planetary gear set via a second clutch and three of the following five connections are implemented to be permanent and two of the specified connections to be detachable by means of at least one shift element:
       connection of the input drive shaft with the ring gear of the second planetary gear set,   connection of the input drive shaft with a carrier of a third planetary gear set,   connection of the drive shaft with a ring gear of the third planetary gear set,   connection of the ring gear of the first planetary gear set with a sun gear of the third planetary gear set,   connection of the ring gear of the first planetary gear set with the carrier of the second planetary gear set.       
 
         [0018]    In particular, a gear set is understood to be a planetary gear set; it comprises at least one sun gear, with which one or more planetary gears mesh, a carrier, which determines the axes of the planetary gears, and a ring gear, with which the planetary gears mesh. Preferably, the ring gear has an inner gearing and the sun gear an outer gearing. 
         [0019]    One advantage of the invention can be that the shift elements of the multi-stage transmission, that is, the transmission-side brakes and clutches, are easily accessible from the outside. Thus, the actuators, for example electric motors, hydraulic valves, hydraulic pumps and the like, can be disposed in the vicinity of the shift elements, whereby mechanical and/or hydraulic losses can be diminished and less energy can be necessary for the actuation of shift elements. Also, less energy is needed to maintain the shift element in its current operating state, that is, disengaged or engaged, respectively, for example, because the losses in pressure are less as well as a result of short lines. It is also possible to dispose the shift elements on the housing, so they are at least partially rotationally fixed, by means of which, seals that connect a standing line with a rotating line can be completely or partially avoided. 
         [0020]    The spatial configuration of easily accessible shift elements simplifies the usual replacement of hydraulically actuated lamellar clutches or brakes by electromechanically or electrohydraulically actuated brakes and clutches, that are comparatively easy to control as needed. Easily accessible shift elements are, on the one hand, brakes that couple a shaft with the housing in a rotatably fixed manner, but, on the other hand, are shift elements on the outer lying shafts of the multi-stage transmission, preferably an input or output shaft to which the hydraulic fluid required for actuation can be supplied comparatively easily. 
         [0021]    Besides this property, the multi-stage transmission also has a good degree of gearing efficiency, only little stress on component parts, especially low planetary set and shift element torque, low absolute and relative speeds of rotation and/or low construction costs. The latter makes possible the implementation of the multi-stage transmission with just little weight and low costs. Finally, the multi-stage transmission enables a good transmission ratio range, thus a very serviceable stepping of the gears. 
         [0022]    In general, a preferred embodiment of the multi-stage transmission comprises four planetary gear sets, four clutches, two brakes and a fixed coupling of the housing. 
         [0023]    Through actuation of two shift elements, respectively (brakes and/or clutches) nine forward gears and one reverse gear can be engaged, wherein three other alternative shift positions are available for the fourth gear. 
         [0024]    A hydrodynamic torque converter, a hydrodynamic clutch, and additional start-up clutch, an integrated start-up clutch or brake and/or an additional electric machine can serve as start-up elements. 
         [0025]    In principle, an electric machine or other power/energy source can be disposed on each shaft. Furthermore, a freewheel can be disposed on each shaft, basically for the housing or for another shaft. 
         [0026]    Preferably the multi-stage transmission is implemented as a standard drive, but a front-traverse design is also conceivable. 
         [0027]    All shift elements can act in a friction or form locking manner. Preferably the first clutch and/or the third clutch (in other transmission variants the seventh instead of the third clutch), however, are implemented as form-locking clutches, especially as claw clutches, which leads to a significantly improved efficiency and therefore higher fuel economy. 
         [0028]    As a result it is understood that the first and third clutch (or the seventh clutch) need to be actuated only once when shifting from the first through the ninth gear and that therefore these shift elements are especially suited to be implemented as a claw clutch. It is thus also understood that with these shift elements the advantage of the better degree of effectiveness prevails over the disadvantage of the more difficult handling because of their comparatively seldom activation. In particular it is understood that the actuation of both shift elements can take place in comparatively high gears, whereby the difference of rotational speed of the shafts can be small and thus favorable for the one actuation of the claw clutch. 
         [0029]    The geometric position (sequence) of the individual gear set and shift elements is freely selectable, as long as it allows the connectivity of elements. The individual elements can thus be shifted in their position arbitrarily. 
         [0030]    Further advantageous variants of the multi-stage transmission result from the description in overview with the drawings. Functionally, these have the same properties as the main system, in particular similar degree of effect, similar stepping etc. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    For a better understanding of the invention this will be more precisely explained by means of the following drawings. 
           [0032]    They are, in greatly simplified schematic representation: 
           [0033]      FIG. 1  a first schematically representative model variant of a multi-stage transmission according to the invention; 
           [0034]      FIG. 2  a second schematically representative model variant of a multi-stage transmission according to the invention; 
           [0035]      FIG. 3  a third schematically representative model variant of a multi-stage transmission according to the invention; 
           [0036]      FIG. 4  a fourth schematically representative model variant of a multi-stage transmission according to the invention; 
           [0037]      FIG. 5  a fifth schematically representative model variant of a multi-stage transmission according to the invention; 
           [0038]      FIG. 6  a sixth schematically representative model variant of a multi-stage transmission according to the invention; 
           [0039]      FIG. 7  a seventh schematically representative model variant of a multi-stage transmission according to the invention; 
           [0040]      FIG. 8  an eighth schematically representative model variant of a multi-stage transmission according to the invention and 
           [0041]      FIG. 9  a table that shows the engaged shift elements for the transmission variant illustrated in  FIG. 1  in each gear step. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0042]    By way of introduction it should be noted that the same parts are provided with the same reference numbers or same part designations in the differently described embodiments so that the disclosures contained in the whole description can be correspondingly applied to the parts with the same reference numbers or same part designations. The chosen specifications of position, for example such as above, below, on the side etc., also refer to the immediately described as well as represented drawing and with a change of position are to be applied correspondingly to the new position. Furthermore, single features or combinations of features from the different embodiments illustrated and described may also represent, by themselves, independent, inventive or invention-related solutions. 
         [0043]      FIG. 1  shows a multi-stage transmission comprising four planetary gear sets  1 ,  2 ,  3 ,  4 , an input drive shaft  70 , an output shaft  71 , six other rotatable shafts  73 ,  74 ,  75 ,  76 ,  77 ,  78 , six shift elements  51 ,  52 ,  61 ,  62 ,  63 ,  64 , of which there are two brakes  51 ,  52  and four clutches  61 ,  62 ,  63 ,  64 . The four planetary gear sets  1 ,  2 ,  3 ,  4  are disposed behind one another in the sequence: first planetary gear set  1 , second planetary gear set  2 , third planetary gear set  3 , fourth planetary gear set  4 . The first planetary gear set  1 , the second planetary gear set  2 , the third planetary gear set  3  and the fourth planetary gear set  4  are constructed as minus planetary gear sets. The planetary gear sets  1 ,  2 ,  3 ,  4  are jointly surrounded by a housing  72 . In the variant of the multi-stage transmission of  FIG. 1 : 
         [0044]    a sun gear  41  of the fourth planetary gear set  4  is connected with the housing  72  in a rotatably fixed manner, 
         [0045]    a ring gear  13  of a first planetary gear set  1  is permanently connected with a ring gear  43  of the fourth planetary gear set  4 , 
         [0046]    a sun gear  11  of the first planetary gear set  1  and a sun gear  21  of a second planetary gear set  2  can be coupled with the housing  72  via a first brake  51 , 
         [0047]    a carrier  12  of the first planetary gear set  1  can be coupled with the housing  72  via a second brake  52 , 
         [0048]    the output shaft  71  can be coupled with a carrier  42  of the fourth planetary gear set  4  via a first clutch  61 , 
         [0049]    the input drive shaft  70  can be coupled with one with the sun gear  21  of the second planetary gear set  2  via a second clutch  62 , 
         [0050]    the input drive shaft  70  can be coupled with the ring gear  23  of the second planetary gear set  2  via a third clutch  63 , 
         [0051]    the input drive shaft  70  can be coupled with the carrier  32  of the third planetary gear set  3  via a fourth clutch  64 , 
         [0052]    the output shaft  71  is permanently connected with the ring gear  33  of the third planetary gear set  3 , 
         [0053]    the ring gear  13  of the first planetary gear set  1  is permanently connected with the sun gear  31  of the third planetary gear set  3  and 
         [0054]    the ring gear  13  of the first planetary gear set  1  is permanently connected with the carrier  22  of the second planetary gear set  2 . 
         [0055]      FIG. 2  shows a multi-stage transmission that is very similar to the multi-stage transmission of  FIG. 1  and differs from the embodiment of  FIG. 1  in the following points: 
         [0056]    the input drive shaft  70  is permanently connected with the carrier  32  of the third planetary gear set  3  and 
         [0057]    the output shaft  71  can be coupled with the ring gear  33  third planetary gear set  3  via a fifth clutch  65 . 
         [0058]      FIG. 3  shows a multi-stage transmission that is very similar to the multi-stage transmission of  FIG. 1  and differs from the embodiment of  FIG. 1  in the following points: 
         [0059]    the input drive shaft  70  is permanently connected with the carrier  32  of the third planetary gear set  3  and 
         [0060]    the ring gear  13  of the first planetary gear set  1  can be coupled with the sun gear  31  of the third planetary gear set  3  via a sixth clutch  66 . 
         [0061]      FIG. 4  shows a multi-stage transmission that is very similar to the multi-stage transmission of  FIG. 1  and differs from the embodiment of  FIG. 1  in the following points: 
         [0062]    the input drive shaft  70  is permanently connected with the ring gear  23  of the second planetary gear set  2  and 
         [0063]    the ring gear  13  of the first planetary gear set  1  can be coupled with the carrier  22  of the second planetary gear set  2  via a seventh clutch  67 . 
         [0064]      FIG. 5  shows a multi-stage transmission that is very similar to the multi-stage transmission of  FIG. 4  and differs from the embodiment of  FIG. 4  in the following points: 
         [0065]    the ring gear  23  of the second planetary gear set  2  is not to be coupled with the sun gear  21  of the second planetary gear set  2  but with the carrier  22  of the second planetary gear set  2  via a second clutch  62 . 
         [0066]      FIG. 6  shows a multi-stage transmission that is very similar to the multi-stage transmission of  FIG. 4  and differs from the embodiment of  FIG. 4  in the following points: 
         [0067]    the sun gear  21  of the second planetary gear set  2  is not to be coupled with the ring gear  23  of the second planetary gear set  2  but with the carrier  22  of the second planetary gear set  2  via a second clutch  62 . 
         [0068]    At this point it should be noted that the variants illustrated in  FIG. 5  and  FIG. 6 , in regard to the position of the second clutch  62 , can also be used in the following variants of the transmission. That is, the second clutch  62  does not have to be disposed between the ring gear  23  and the sun gear  21  also in the following variants of the transmission, but can be disposed between the sun gear  21  and the carrier  22  or between the ring gear  23  and the carrier  21 . 
         [0069]      FIG. 7  shows a multi-stage transmission that is very similar to the multi-stage transmission of  FIG. 4  and differs from the embodiment of  FIG. 4  in the following points: 
         [0070]    the input drive shaft  70  is permanently connected with the carrier  32  of the third planetary gear set  3  and 
         [0071]    the output shaft  71  can be couple with the ring gear  33  of the third planetary gear set  3  via a fifth clutch  65 . 
         [0072]      FIG. 8  shows a multi-stage transmission that is very similar to the multi-stage transmission of  FIG. 4  and differs from the embodiment of  FIG. 4  in the following points: 
         [0073]    the input drive shaft  70  is permanently connected with the carrier  32  of the third planetary gear set  3  and 
         [0074]    the ring gear  13  of the first planetary gear set  1  can be coupled with the sun gear  31  of the third planetary gear set  3  via a sixth clutch  66 . 
         [0075]    In the multi-stage transmission represented in  FIG. 1  the following gears can be engaged: 
         [0076]    A first gear can be implemented with the engaged second brake  52 , the engaged first clutch  61  and the engaged third clutch  63 . 
         [0077]    A second gear can be implemented with the engaged first brake  51 , the engaged first clutch  61  and the engaged third clutch  63 . 
         [0078]    A third gear can be implemented with the engaged first clutch  61 , the engaged second clutch  62  and the engaged third clutch  63 . 
         [0079]    A fourth gear is implemented with the engaged first clutch  61 , the engaged third clutch  63  and the engaged fourth clutch  64 , or 
         [0080]    with the engaged second brake  52 , the engaged first clutch  61  and the engaged fourth clutch  64 , or 
         [0081]    with the engaged first clutch  61 , the engaged second clutch  62  and the engaged fourth clutch  64 , or 
         [0082]    with the engaged first brake  51 , the engaged first clutch  61  and the engaged fourth clutch  64 . 
         [0083]    A fifth gear is implemented with the engaged second clutch  62 , the engaged third clutch  63  and the engaged fourth clutch  64 . 
         [0084]    A sixth gear is implemented with the engaged first brake  51 , the engaged third clutch  63  and the engaged fourth clutch  64 . 
         [0085]    A seventh gear is implemented with the engaged second brake  52 , the engaged third clutch  63  and the engaged fourth clutch  64 . 
         [0086]    An eighth gear is implemented with the engaged first brake  51 , the engaged second brake  52  and the engaged fourth clutch  64 . 
         [0087]    A ninth gear is implemented with the engaged second brake  52 , the engaged second clutch  62  and the engaged fourth clutch  64 . 
         [0088]    A reverse gear is implemented with the engaged second brake  52 , the engaged first clutch  61  and the engaged second clutch  62 . 
         [0089]    At the same time, the respective shift elements not mentioned are disengaged. 
         [0090]    The table in  FIG. 9  also shows this as it shows the transmission ratios of the respective gear steps as well. 
         [0091]    The shift positions of the multi-stage transmission shown in  FIG. 2  are completely similar to those of the multi-stage transmission shown in  FIG. 1  but there the fifth clutch  65  takes the place of the fourth clutch  64 . 
         [0092]    The shift positions of the multi-stage transmission shown in  FIG. 3  are completely similar to those of the multi-stage transmission shown in  FIG. 1  but there the sixth clutch  66  takes the place of the fourth clutch  64 . 
         [0093]    The shift positions of the multi-stage transmission shown in  FIGS. 4 to 6  are completely similar to those of the multi-stage transmission shown in  FIG. 1  but there the seventh clutch  67  takes the place of the third clutch  63 . 
         [0094]    The shift positions of the multi-stage transmission shown in  FIG. 7  are completely similar to those of the multi-stage transmission shown in  FIG. 4  but there the fifth clutch  65  takes the place of the fourth clutch  64 . 
         [0095]    The shift positions of the multi-stage transmission shown in  FIG. 8  are completely similar to those of the multi-stage transmission shown in  FIG. 4  but there the sixth clutch  66  takes the place of the fourth clutch  64 . 
         [0096]    Preferably, all the gear sets  1 ,  2 ,  3 ,  4  in the multi-stage transmission are implemented as minus gear sets. 
         [0097]    In an advantageous variant the transmission ratios are: 
         [0098]    −1.920 between sun gear  11  and ring gear  13  of the first gear set  1 , and/or 
         [0099]    −1.750 between sun gear  21  and ring gear  23  of the second gear set  2 , and/or 
         [0100]    −1,650 between sun gear  31  and ring gear  33  of the third gear set  3 , and/or 
         [0101]    −1.500 between sun gear  41  and ring gear  43  of the fourth gear set  4 . 
         [0102]    In general, instead of an implementation of a first specified connection/coupling to a carrier  12 ,  22 ,  32 ,  42  of a gear set  1 ,  2 ,  3 ,  4  and a second specified connection/coupling to a ring gear  13 ,  23 ,  33 ,  43  of this gear set  1 ,  2 ,  3 ,  4 , the first specified connection/coupling may be implemented to specified ring gear  13 ,  23 ,  33 ,  43  of this gear set  1 ,  2 ,  3 ,  4  and the second specified connection/coupling to specified carrier  12 ,  22 ,  32 ,  42  of this gear set  1 ,  2 ,  3 ,  4 , wherein this gear set  1 ,  2 ,  3 ,  4  is implemented as a plus gear set instead of a minus gear set or as a minus gear set instead of a plus gear set, respectively. In other words the connection/coupling to the carrier  12 ,  22 ,  32 ,  42  and to the ring gear  13 ,  23 ,  33 ,  43  of a gear set  1 ,  2 ,  3 ,  4  is exchanged and the direction of rotation between sun gear  11 ,  21 ,  31 ,  41  and ring gear  13 ,  23 ,  33 ,  43  of gear set  1 ,  2 ,  3 ,  4  is reversed. It should also be noted that in the configuration of the multi-stage transmission the value of the stationary transmission ratio is increased by 1 or decreased by 1, if the shiftable transmission ratios between input drive shaft  70  and output shaft  71  should otherwise remain equal. By specified variations of the gear sets  1 ,  2 ,  3 ,  4  the connection/coupling between the individual transmission elements can thus be changed without changing the characteristics of the transmission at the same time. Thereby several structural configurations are available, which can simplify the implementation of the transmission in individual cases. The above-mentioned exchange of the connection/coupling is not limited to one gear set  1 ,  2 ,  3 ,  4 , but can be applied to several gear sets  1 ,  2 ,  3 ,  4  at the same time as well. 
         [0103]    The embodiments show possible variations in the implementation of a multi-stage transmission of the invention, wherein it should be noted here the invention is not limited to the variations in implementation of it specifically shown, but rather diverse combinations of the individual variations in implementation are possible among themselves and this possibility of variation lies within the ability of the person skilled in the art on the basis of the teaching of technical actions by means of the present invention. In particular, the possibilities that also result from the combinatorics, although not explicitly shown in the drawings, are included in the scope of protection. Moreover, the total conceivable variations in implementation that are possible through combinations of single details of the represented and described embodiment variations are included in the scope of protection. 
         [0104]    For the sake of order it is noted that, for better understanding of the design of the multi-stage transmission, this is shown schematically in the drawings and in reality can comprise more parts than shown, less parts than shown or even other parts. In general, the concrete structural configuration lies within the scope of he abilities of a person skilled in the art. 
         [0105]    The problem underlying the independent inventive solutions can be inferred from the description. 
       REFERENCE NUMERALS 
       [0000]    
       
           1  first transmission gear set 
           2  second transmission gear set 
           3  third transmission gear set 
           4  fourth transmission gear set 
           11  sun gear of the first transmission gear set 
           12  carrier of the first transmission gear set 
           13  ring gear of the first transmission gear set 
           21  sun gear of the second transmission gear set 
           22  carrier of the second transmission gear set 
           23  ring gear of the second transmission gear set 
           31  sun gear of the third transmission gear set 
           32  carrier of the third transmission gear set 
           33  ring gear of the third transmission gear set 
           41  sun gear of the fourth transmission gear set 
           42  carrier of the fourth transmission gear set 
           43  ring gear of the fourth transmission gear set 
           51  first brake 
           52  second brake 
           61  first clutch 
           62  second clutch 
           63  third clutch 
           64  fourth clutch 
           65  fifth clutch 
           66  sixth clutch 
           67  seventh clutch 
           70  input drive shaft 
           71  output shaft 
           72  housing 
           73 ,  74 ,  75 ,  76 ,  77 ,  78  shaft