Patent Abstract:
A four-stage multi-gear transmission in which the carrier of a fourth gearset ( 4 ) is connected in a rotationally fixed manner to a housing ( 72 ), a ring gear of a first gearset ( 1 ) is connected rotationally fixed to a sun gear ( 41 ) of the fourth gearset ( 4 ), a drive input ( 70 ) can couple, via a first clutch ( 61 ), a sun gear ( 11 ) of the first gearset ( 1 ), a ring gear ( 42 ) of the fourth gearset ( 4 ) can couple, via a second clutch ( 62 ), a drive output ( 71 ), a carrier ( 13 ) of the first gearset ( 1 ) can couple, via a first brake ( 51 ), a housing ( 72 ) and the sun gear ( 11 ) of the first gearset ( 1 ) can couple, via a second brake ( 52= ), the housing ( 72 ). Varying other couplings within the multi-gear transmission can provide a range of transmissions with similar properties.

Full Description:
This application is a National Stage completion of PCT/EP2013/051982 filed Feb. 1, 2013, which claims priority from German patent application serial no. 10 2012 203 936.8 filed Mar. 14, 2012. 
     FIELD OF THE INVENTION 
     The invention concerns a multi-gear transmission of planetary design, in particular for a motor vehicle. 
     BACKGROUND OF THE INVENTION 
     Such multi-gear transmissions are preferably used as automatic transmissions of motor vehicles, wherein the power flow acting in each gear within the planetary gearset is defined by selective actuation of the shifting elements. Furthermore, in an automatic transmission the planetary gearsets are usually connected to a starting element that is subject to slip and optionally provided with a locking clutch, such as a hydrodynamic torque converter or a liquid clutch. 
     From DE 10 2008 000 428 A1 a planetary multi-gear transmission is known, in which, in a housing four planetary gearsets and a total of eight rotating shafts are arranged, one of which is the drive input shaft and another the drive output shaft of the multi-gear transmission. In addition, in the area of the shafts at least six shifting elements are provided, by the selective actuation of which the power flow within the four planetary gearsets is varied and such that various transmission ratios between the drive input and the drive output can be defined. In that way, nine forward gears and one reverse gear can be engaged. 
     SUMMARY OF THE INVENTION 
     The purpose of the present invention is to indicate an alternative multi-gear transmission, preferably with improved efficiency and with a sufficiently large and sufficiently uniformly distributed range of transmission ratios. 
     The objective of the invention is achieved by a multi-gear transmission comprising at least four planetary gearsets, a housing, a drive input shaft and a drive output shaft, wherein:
         a carrier of the fourth planetary gearset connected to the housing in a rotationally fixed manner,   a ring gear of the first planetary gearset is connected in a rotationally fixed manner to a sun gear of the fourth planetary gearset,   the drive input shaft can be coupled to a sun gear of the first planetary gearset by means of a first clutch,   a ring gear of the fourth planetary gearset can be coupled to the drive output shaft by means of a second clutch,   a carrier of the first planetary gearset can be coupled to the housing by a first brake,   the sun gear of the first planetary gearset can be coupled to the housing by a second brake, and at least four of the following connections are formed permanently whereas at least two of the following connections can be formed detachably by means of at least one shifting element:   connection of a ring gear of the second planetary gearset to the carrier of the first planetary gearset,   connection of the ring gear of the first planetary gearset to a carrier of the second planetary gearset,   connection of the ring gear of the first planetary to a sun gear of a third planetary gearset,   connection of a ring gear of the third planetary gearset to the drive output shaft,   connection of the drive input shaft to a sun gear of the second planetary gearset,   connection of the drive input shaft to a carrier of the third planetary gearset.       

     A planetary gearset is in particular understood to mean a gearset that comprises at least one sun gear which meshes with one or more planetary gearwheels, a carrier that determines the axes of the planetary gearwheels, and a ring gear which meshes with the planetary gearwheels. Preferably, the ring gear has inner teeth and the sun gear gas outer teeth. 
     An advantage of the invention can be that the shifting elements of the multi-gear transmission, i.e. the brakes and clutches of the transmission, can be accessed easily from the outside. Thus the actuators, such as electric motors, hydraulic valves, hydraulic pumps and the like, can be arranged close to the shifting elements whereby mechanical and/or hydraulic losses are reduced and less energy may be required for actuating the shifting elements. Less energy may also be needed for maintaining a shifting element in its current operating condition at the time, namely open or closed, for example since by virtue of short pressure lines pressure losses are also lower. This also makes it possible to arrange shifting elements on the housing and therefore at least in part rotationally fixed, such that seals that connect a static line with a rotating line can be wholly or partially avoided. 
     The spatial arrangement of shifting elements that are easily accessible also simplifies the replacement of the usually hydraulically actuated disk clutches or disk brakes, for example by electro-mechanically or electro-hydraulically actuated brakes and clutches, which can be comparatively simply actuated as necessary. Easily accessible shifting elements are on the one hand brakes that couple a shaft to the housing in a rotationally fixed manner, but also shifting elements on external shafts of the multi-gear transmission, preferably on the drive input shaft or the drive output shaft, to these brakes the hydraulic fluid needed for actuation of these brakes can be supplied comparatively simply. 
     Besides this characteristic, the multi-gear transmission also has good gearing efficiency, only slight loading of the components, in particular planetary gearsets and shifting element torques, low absolute and relative rotation speeds, and/or little structural complexity. The latter feature enables the multi-gear transmission to be produced with relatively low weight and for low cost. Finally, the multi-gear transmission also provides a good transmission ratio range, i.e. a user-friendly gear gradation. 
     In general, a preferred embodiment of the multi-gear transmission has four planetary gearsets, four clutches, two brakes and a fixed housing coupling. 
     By actuation of two shifting elements at a time (brakes and/or clutches), nine forward gears and one reverse gear can be engaged, whereas for the fourth gear another three alternative shift positions are available. 
     As the starting element a hydrodynamic torque converter, a hydrodynamic clutch, an additional starting clutch, an integrated starting clutch or brake and/or an additional electric machine can be used. 
     In principle an electric machine or some other force/power source can be arranged on any shaft. Moreover, in principle a freewheel can be arranged on any shaft, to the housing or to another shaft. 
     Preferably, the multi-gear transmission is configures as a standard drive unit although a front transverse configuration is also conceivable. 
     All the shifting elements can be frictional or interlocking. Preferably, however, the clutch that connects the drive input shaft to the sun gear of the first planetary gearset and/or the clutch that connects the ring gear of the fourth planetary gearset to the drive output shaft are in the form of interlocking clutches, in particular claw clutches, which results in substantially better efficiency and hence substantial fuel consumption advantages. 
     In this case it was realized that when shifting through from the first to the ninth gear the first and second clutches have to be actuated only once, so those shifting elements are particularly suitable to be designed as claw clutches. Furthermore, it was realized that in the case of those two shifting elements, owing to their comparatively infrequent actuation, the advantage of better efficiency outweighs the disadvantage of more difficult manipulation. In particular, it was recognized that the two shifting elements can be actuated in comparatively high gears, whereby the rotational speed difference between the shafts can be small and therefore favorable for the actuation of a claw clutch. 
     The geometrical position (sequence) of the individual gearsets can be freely chosen provided that it permits the appropriate connections between elements. Thus, the position of individual elements can be modified as desired. 
     Other advantageous variants of the multi-gear transmission emerge from the description in combination with the figures. These all have the same functional properties as the main system, in particular the same efficiency, the same gradation, etc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For the better understanding of the invention, it is described in more detail with reference to the figures shown below. 
       The figures shown in each case in greatly simplified schematic form: 
         FIG. 1 : A first, schematically represented example variant of a multi-gear transmission according to the invention, and  FIG. 1A  shows a variant of this figure; 
         FIG. 2 : A second, schematically represented example variant of a multi-gear transmission according to the invention; 
         FIG. 3 : A third, schematically represented example variant of a multi-gear transmission according to the invention; 
         FIG. 4 : A fourth, schematically represented example variant of a multi-gear transmission according to the invention; 
         FIG. 5 : A fifth, schematically represented example variant of a multi-gear transmission according to the invention; 
         FIG. 6 : A sixth, schematically represented example variant of a multi-gear transmission according to the invention; 
         FIG. 7 : A seventh, schematically represented example variant of a multi-gear transmission according to the invention; 
         FIG. 8 : A eighth, schematically represented example variant of a multi-gear transmission according to the invention; and 
         FIG. 9 : A ninth, schematically represented example variant of a multi-gear transmission according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     By way of introduction it should be noted that in the various embodiments described the same components are given the same indexes, so that in the disclosures given throughout the description, components with the same indexes can be logically regarded as equivalent. Likewise, positional details chosen in the description, such as above, below, lateral, etc., refer to the figure being described at the time and in the event of a position change should be logically transferred to the new position. Furthermore, individual features or combinations thereof in the various example embodiments shown and described, represent inventive solutions in their own right or ones according to the invention. 
       FIG. 1  shows a multi-gear transmission comprising four planetary gearsets  1 ,  2 ,  3 ,  4 , a drive input shaft  70 , a drive output shaft  71 , six further rotating shafts and six shifting elements  51 ,  52 ,  61 ,  62 ,  63 ,  64 , of which two are brakes  51 ,  52  and four are clutches  61 ,  62 ,  63 ,  64 . The four planetary gearsets  1 ,  2 ,  3 ,  4  are arranged one after another in the sequence of the first planetary gearset  1 , the second planetary gearset  2 , the third planetary gearset  3  and the fourth planetary gearset  4 . The first, second and third planetary gearsets  1 ,  2 ,  3  are in the form of minus planetary gearsets, whereas the fourth planetary gearset is a plus planetary gearset. The planetary gearsets  1 ,  2 ,  3 ,  4  are accommodated together in a housing  72 . In the multi-gear transmission variant shown in  FIG. 1 :
         a carrier of the fourth planetary gearset  4  is connected to a housing  72  in a rotationally fixed manner,   a ring gear of the first planetary gearset  1  is connected in a rotationally fixed manner to a sun gear of the fourth planetary gearset  4 ,   the drive input shaft  70  can be coupled by the first clutch  61  to a sun gear  11  of the first planetary gearset  1 ,   a ring gear  42  of the fourth planetary gearset  4  can be coupled by a second clutch  62  to the drive output shaft  71 ,   a carrier  13  of the first planetary gearset  1  can be coupled by a second brake  52  to the housing  72 ,   the sun gear  11  of the first planetary gearset  1  can be coupled by a first brake  51  to the housing  72 ,   the ring gear  22  of the second planetary gearset  2  is permanently connected to the carrier  13  of the first planetary gearset  1 ,   the ring gear  12  of the first planetary gearset  1  is permanently connected to the carrier  23  of the second planetary gearset  2 ,   the ring gear  12  of the first planetary gearset  1  is permanently connected to the sun gear  31  of the third planetary gearset  3 ,   the ring gear  32  of the third planetary gearset  3  is permanently connected to the drive output shaft  71 ,   the drive input shaft  70  can be coupled by a fourth clutch  64  to the sun gear  21  of the second planetary gearset  2 , and   the drive input shaft  70  can be coupled by a third clutch  63  to the carrier  33  of the third planetary gearset  3 .       

       FIG. 2  shows a multi-gear transmission very similar to the multi-gear transmission of  FIG. 1 , but which differs therefrom in the following particulars: 
     The ring gear  22  of the second gearset  2  can be coupled by a fourth clutch  64  to the carrier  13  of the first gearset  1 , and
         the drive input  70  is permanently connected to the sun gear  21  of the second gearset  2 .       

       FIG. 3  shows a further multi-gear transmission very similar to the multi-gear transmission of  FIG. 1 , but which differs from the embodiment of  FIG. 1  in the following particulars: 
     The ring gear  12  of the first gearset  1  can be coupled by a fourth clutch  64  to the carrier  23  of the second gearset  2 , and
         the drive input shaft  70  is permanently connected to the sun gear  21  of the second gearset  2 .       

       FIG. 4  shows another variant of a mufti-gear transmission comprising four planetary gearsets  1 ,  2 ,  3 ,  4 , a drive input shaft  70 , a drive output shaft  71 , six further rotating shafts and six shifting elements  51 ,  52 ,  61 ,  62 ,  63 ,  64  of which two  51 ,  52  are brakes and four  61 ,  62 ,  63 ,  64  are clutches. The four planetary gearsets  1 ,  2 ,  3 ,  4  are arranged one after another in the sequence of the first planetary gearset  1 , the second planetary gearset  2 , the third planetary gearset  3  and the fourth planetary gearset  4 . The first, second and third planetary gearsets  1 ,  2 ,  3  are in the form of minus planetary gearsets whereas the fourth planetary gearset  4  is a plus planetary gearset. The planetary gearsets  1 ,  2 ,  3 ,  4  are jointly accommodated in a housing  72 . In the variant shown in  FIG. 4 :
         the carrier of the fourth planetary gearset  4  is connected rotationally fixed to the housing  72 ,   the ring gear of the first planetary gearset  1  is connected rotationally fixed to the sun gear  41  of the fourth planetary gearset  4 ,   the drive input shaft  70  can be coupled by a first clutch  61  to the sun gear  11  of the first planetary gearset  1 ,   the ring gear  42  of the fourth planetary gearset  4  can be coupled by a second clutch  62  to the drive output shaft  71 ,   the carrier  13  of the first gearset  1  can be coupled by a second brake  52  to a housing  72 ,   the sun gear  11  of the first gearset  1  can be coupled by a first brake  51  to the housing  72 ,   the ring gear of the second gearset  2  is permanently connected to the carrier  13  of the first gearset  1 ,   the ring gear  12  of the first gearset  1  is permanently connected to a carrier  23  of the second gearset  2 ,   the ring gear  12  of the first gearset  1  is permanently connected to the sun gear of the third gearset  3 ,   the ring gear  32  of the third gearset  3  can be coupled by a third clutch  63  to the drive output shaft  71 ,   the drive input shaft  70  can be coupled by a fourth clutch  64  to the sun gear  21  of the second gearset  2 , and   the drive input shaft  70  is permanently connected to the carrier  33  of the third gearset  3 .       

       FIG. 5  shows a multi-gear transmission that differs from the multi-gear transmission of  FIG. 4  in the following particulars: the ring gear  12  of the first gearset  1  can be coupled by a third clutch  63  to the sun gear of the third gearset  3 , and the ring gear  32  of the third gearset  3  is permanently connected to the drive output shaft  71 . 
       FIG. 6  shows a multi-gear transmission that differs from the multi-gear transmission of  FIG. 4  in the following particulars: the ring gear of the second gearset  2  can be coupled by a fourth clutch  64  to the carrier  13  of the first gearset  1 , and the drive input shaft  70  is permanently connected to a sun gear  21  of the second gearset  2 . 
     Furthermore, the sun gear of the second gearset  2  is permanently connected to the drive input shaft. 
       FIG. 8  shows a multi-gear transmission very similar to the multi-gear transmission of  FIG. 6 , and in which only the points h) and k) are differently designed. To be specific: the ring gear  12  of the first gearset  1  can be coupled by a fourth clutch  64  to a carrier  23  of the second gearset  2 , and the drive input  70  is permanently connected to a sun gear  21  of the second gearset  2 . 
     Finally,  FIG. 9  shows a multi-gear transmission that differs from the multi-gear transmission of  FIG. 8  in the following particulars: 
     The ring gear  12  of the first gearset  1  can be coupled by a third clutch  63  to a sun gear of a third gearset  3 , and a ring gear  32  of the third gearset  3  is permanently connected to the drive output  71 . 
     With all the multi-gear transmissions shown in  FIGS. 1 to 9  the following gears can be engaged: 
     A first gear can be obtained by closing the second brake  52 , the second clutch  62  and the fourth clutch  64 . 
     A second gear can be obtained by closing the first brake  51 , the second clutch  62  and the fourth clutch  64 . 
     A third gear can be obtained by closing the first, second and fourth clutches  61 ,  62  and  64 . 
     A fourth gear can be obtained by closing the second, third and fourth clutches  62 ,  63  and  64 , or 
     by closing the first brake  51 , the second clutch  62  and the third clutch  63 , or 
     by closing the first, second and third clutches  61 ,  62  and  63 . 
     A fifth gear can be obtained by closing the first clutch  61 , the third clutch  63  and the fourth clutch  64 . 
     A sixth gear can be obtained by closing the first brake  51 , the third clutch  63  and the fourth clutch  64 . 
     A seventh gear can be obtained by closing the second brake  52 , the third clutch  63  and the fourth clutch  64 . 
     An eighth gear can be obtained by closing the first brake  51 , the second brake  52  and the third clutch  63 . 
     A ninth gear can be obtained by closing the second brake  52 , the first clutch  61  and the third clutch  63 . 
     A reverse gear can be obtained by closing the second brake  52 , the first clutch  61  and the second clutch  62 . 
     In all cases, the shifting elements not mentioned are open. 
     Preferably, in the multi-gear transmissions shown:
         the first gearset  1  is a minus gearset,   the second gearset  2  is a minus gearset,   the third gearset  3  is a minus gearset, and   the fourth gearset  4  is a plus gearset.       

     In an advantageous variant the transmission ratio of:
         the first gearset  1  between the sun gear  11  and the ring gear  12  equals −2.015, and   the second gearset  2  between the sun gear  21  and the ring gear  22  equals −1.600, and   the third gearset  3  between the sun gear  31  and the ring gear  32  equals −1.700, and   the fourth gearset  4  between the sun gear  41  and the ring gear  42  equals +1.804.       

     In general, instead of a first-mentioned connection/coupling to a carrier  13 ,  23 ,  33 ,  43  of a gearset  1 ,  2 ,  3 ,  4  and a second-mentioned connection/coupling to a ring gear  12 ,  22 ,  32 ,  42  of the gearset  1 ,  2 ,  3 ,  4 , the first-mentioned connection/coupling can be made to the ring gear  12 ,  22 ,  32 ,  42  of the gearset  1 ,  2 ,  3 ,  4  and the second-mentioned connection/coupling can be made to the carrier  13 ,  23 ,  33 ,  43  of the gearset  1 ,  2 ,  3 ,  4 , whereby the gearset  1 ,  2 ,  3 ,  4 , instead of being a minus gearset, becomes a plus gearset or instead of being a plus gearset, becomes a minus gearset. In other words, the connections/couplings to the carrier  13 ,  23 ,  33 ,  43  and to the ring gear  12 ,  22 ,  32 ,  42  of a gearset  1 ,  2 ,  3 ,  4  are interchanged and the rotational direction between the sun gear  11 ,  21 ,  31 ,  41  and the ring gear  12 ,  22 ,  32 ,  42  of this gearset  1 ,  2 ,  3 ,  4 , is reversed. An example of such variation is shown in  FIG. 1A  of the drawings. In the layout of the multi-gear transmission it should also be noted that the value of the fixed transmission ratio of the gearset should be increased or reduced by 1, respectively, if the shiftable transmission ratios between the drive input  70  and the drive output  71  are otherwise to remain unchanged. By virtue of the variation of the gearsets  1 ,  2 ,  3 ,  4  the connection/coupling between the individual transmission elements can therefore be varied without thereby changing the characteristic of the transmission. This possibility provides for a large number of design variants which, in individual cases, may simplify the production of the transmission. The aforesaid interchanging of the connection/coupling is not restricted to just one gearset  1 ,  2 ,  3 ,  4  but can also be implemented in more than one gearset  1 ,  2 ,  3 ,  4 . 
     The example embodiments illustrate possible embodiment variants of a multi-gear transmission according to the invention, but at this point it should be said that the invention is not limited specifically to the embodiment variants thereof illustrated, but rather, the individual embodiment variants can be combined with one another and such possible variation lies within the competence of a specialist active in the technical field concerned by virtue of vocational training in technical procedures by objective innovation. In particular, the options arising from such combinations but not explicitly illustrated in the figures are covered by the scope of protection. Furthermore, all conceivable embodiment variants made possible by combinations of individual details of the embodiment variants illustrated and described are also covered by the scope of protection. 
     For the sake of completeness let it finally be pointed out that for the better understanding of the structure of the multi-gear transmission, the structure has been illustrated in the figures in a schematic manner, and in reality therefore, it can comprise more components, fewer components or even components other than those shown. In general, the specific design details lie within the scope of specialized knowledge of the field. 
     The objectives addressed by the independent inventive solutions emerge from the description. 
     INDEXES 
     
         
           1  First transmission gearset 
           2  Second transmission gearset 
           3  Third transmission gearset 
           4  Fourth transmission gearset 
           11  Sun gear of the first transmission gearset 
           12  Ring gear of the first transmission gearset 
           13  Carrier of the first transmission gearset 
           21  Sun gear of the second transmission gearset 
           22  Ring gear of the second transmission gearset 
           23  Carrier of the second transmission gearset 
           31  Sun gear of the third transmission gearset 
           32  Ring gear of the third transmission gearset 
           33  Carrier of the third transmission gearset 
           41  Sun gear of the fourth transmission gearset 
           42  Ring gear of the fourth transmission gearset 
           43  Carrier of the fourth transmission gearset 
           51  First brake 
           52  Second brake 
           61  First clutch 
           62  Second clutch 
           63  Third clutch 
           64  Fourth clutch 
           70  Drive input 
           71  Drive output 
           72  Housing

Technology Classification (CPC): 5