Abstract:
A multi-speed automatic transmission for private cars or commercial vehicles includes input and output shafts, two power paths, a double planetary gear train, first and second brakes. The first power path has a first speed ratio and includes first and second clutches. The second power path has a second speed ratio, which is greater than the first speed ratio and in the same direction, with third and fourth clutches. The transmission has eight forward and two reverse speeds and is highly flexible. In one embodiment, the transmission is reduced to six forward and one reverse speed without the second clutch. In another embodiment, the input and output shafts are aligned and the ratios are supplied respectively by a planetary gear train and a direct drive. In another embodiment, the input and output shafts are parallel and the ratios are supplied respectively by two parallel gear trains including constant mesh gears.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to automatic transmissions, in particular for automobile vehicles, comprising planetary gearsets controlled by friction members such as clutches and brakes, and usually coupled to a start-up coupling device subject to slip, such as a torque converter generally provided with a lock-up clutch, or sometimes a simple clutch. 
   2. Description of the Related Art 
   The recent development of these transmissions shows a marked tendency to increase the number of speeds, quite commonly six. The patent EP 0434525 B1 has described such a transmission comprising, between an input shaft and an output shaft housed in a casing, a so-called double planetary gearset with four members identified from first to fourth in order of speed, concentric with the output shaft, and at least one power path between the input shaft and the double planetary gearset, and five control devices, that is to say three clutches and two brakes of which the selective operation in pairs determines various transmission ratios between the input shaft and the output shaft, a first power path having a first fixed speed ratio and including a first clutch and a second clutch, and a second power path having a second fixed speed ratio, higher than the first fixed speed ratio and in the same direction, and including a third clutch. The first member of the double planetary gearset is connected to the first power path by the first control clutch. The second member is fixed to the output shaft. The third member is connected to the second power path by the third control clutch and held against rotation by the first brake. The fourth member is connected to the first power path by the second control clutch and held against rotation by the second brake. Selective operation in pairs of the five control devices provides six forward gears, i.e. a first, by the first control clutch and the first control brake, a second, by the first control clutch and the second control brake, a third, by the first and second control clutches, a fourth by the first and third control clutches, a fifth, by the second and third control clutches, a sixth by the third control clutch and the second control brake, a braked neutral position, by the first and second control brakes, and a reverse drive, by the second control clutch and the first control brake. 
   This transmission has been widely adopted by automobile vehicle manufacturers. 
   It has been proposed to modify the six-speed transmission of EP 0434525 in order to produce a transmission with seven or more speeds (see Prof.-Dr. Peter Tenberge, in Der E-Automat, Ein Automatikgetriebe mit Esprit, Dec. 2001). This transmission with seven or more speeds has serious drawbacks, in particular as regards the progression of steps of the ratios. 
   SUMMARY OF THE INVENTION 
   According to a first aspect of the invention, an eight speed automatic transmission is provided comprising a minimum of components and having, among other things, a good progression of steps of the ratios. 
   To that end, according to this first aspect of the invention, there is more particularly provided a multispeed automatic transmission, in particular for automobile vehicles, comprising between an input shaft and an output shaft housed in a casing, a so-called double planetary gearset with four members identified from first to fourth in order of speed, concentric with the output shaft, two power paths between the input shaft and the double planetary gearset and five control devices, i.e. three clutches and two brakes of which the selective operation in pairs determines various transmission ratios between the input shaft and the output shaft, the first power path having a first fixed speed ratio and comprising the first and the second clutches and the second power path having a second fixed speed ratio greater than the first ratio and in the same direction, and comprising the third clutch, the first member of the double planetary gearset being connected to the first power path by the first clutch, the second member being fixed to the output shaft, the third member being connected to the second power path by the third clutch and held against rotation by the first brake, and the fourth member being connected to the first power path by the second clutch and held against rotation by the second brake, which transmission is characterized in that it comprises a fourth clutch connecting the fourth member to the second power path and constituting a sixth control device, such that selective operation in pairs of the six control devices provides eight forward gears: a first, by the first clutch and the first brake; a second by the first clutch and the second brake, a third by the first and second clutches; a fourth by the first and fourth clutches; a fifth by the first and third clutches; a sixth in direct drive by the third and fourth clutches; a seventh by the second and third clutches; an eighth by the third clutch and the second brake; a braked neutral position by the first and second brakes; a first reverse drive by the second clutch and the first brake; and a second reverse drive by the fourth clutch and the first brake. 
   Advantageously in a transmission according to this first aspect of the invention, depending on whether the input and output shafts are aligned or parallel, the fixed speed ratios of the two power paths are provided by a three-member planetary gearset having a member fixed to the casing and by a direct drive, or by two parallel gearsets of constant-mesh gearwheels. 
   Advantageously, the input and output shafts being aligned, the first power path comprises a planetary gearset with three members of which one is fixed to the casing, defining the first fixed speed ratio less than one, whereas the second power path is in direct drive defining the second fixed speed ratio equal to one. 
   Advantageously furthermore, the three-member planetary gearset comprises a planet carrier fixed to the input shaft carrying planet pinions meshed with each other and respectively with a ring gear and with a sun gear fixed to the casing, the ring gear forming the first power path of fixed ratio less than one comprising the first control clutch and the second control clutch and the input shaft and the planet carrier forming the second power path in direct drive of fixed ratio equal to one comprising the third control clutch and the fourth control clutch. 
   According to an advantageous embodiment, the double planetary gearset comprises a three-member planetary gearset having a planet carrier carrying planet pinions meshed with a sun gear and with a ring gear and additional planet pinions meshed with the planet pinions and with an additional sun gear, the first member being constituted by the additional sun gear, the second member being constituted by the ring gear, the third member being constituted by the planet carrier, and the fourth member being constituted by the sun gear. 
   According to another advantageous embodiment, the double planetary gearset comprises a three-member planetary gearset having a planet carrier carrying planet pinions meshed with a sun gear and with a ring gear, and another three-member gearset having a planet carrier carrying planet pinions meshed with each other and respectively with a ring gear and a sun gear, the first member being constituted by the sun gear, the second member being constituted by the ring gears fixed together for rotation, the third member being constituted by the planet carriers fixed together for rotation, and the fourth member being constituted by the sun gear. 
   According to an advantageous embodiment, the three-member planetary gearset comprises a planet carrier fixed to the input shaft carrying planet pinions meshed with each other and respectively with a ring gear and with a sun gear connected to a control brake for the control of the first power path, the ring gear forming that first power path of fixed ratio less than one comprising the first control clutch and the second control clutch, and the input shaft and the planet carrier forming the second power path in direct drive of fixed ratio equal to one comprising the third control clutch and the fourth control clutch. 
   According to another advantageous embodiment, the input and output shafts being parallel, on the one hand the first power path and the second power path each comprise a parallel gearset, with constant-mesh gearwheels, respectively defining the first fixed speed ratio and the second fixed speed ratio greater than the first ratio and in the same direction, and on the other hand the double planetary gearset comprises a three-member planetary gearset having a planet carrier carrying planet pinions meshed with a sun gear and with a ring gear and another three-member gearset having a planet carrier carrying planet pinions meshed with a sun gear and with a ring gear, the first member being constituted by the ring gear, the second member being constituted by the ring gear and the planet carrier fixed together for rotation, the third member being constituted by the planet carrier and the fourth member being constituted by sun gears fixed together for rotation. 
   According to another aspect of the invention, the architecture of the multi-speed transmission is adapted to make a new transmission with six forward speeds and one reverse drive by omitting the second control clutch of the transmission with eight forward speeds and two reverse drives. 
   According to this aspect of the invention, a multi-speed automatic transmission is provided which comprises between an input shaft and an output shaft housed in a casing, a so-called double planetary gearset with four members identified from first to fourth in order of speed, concentric with the output shaft, two power paths between the input shaft and the double planetary gearset and five control devices, i.e. three clutches and two brakes of which the selective operation in pairs determines various transmission ratios between the input shaft and the output shaft, the first power path having a first fixed speed ratio and comprising the first clutch and the second power path having a second fixed speed ratio greater than the first ratio and in the same direction and comprising the second clutch, the first member of the double planetary gearset being connected to the first power path by the first clutch, the second member being fixed to the output shaft, the third member being connected to the second power path by the second clutch and held against rotation by the first brake and the fourth member being held against rotation by the second brake, which transmission is characterized in that the fourth member is connected to the second power path by the third clutch so as to obtain by selective operation in pairs of the five control devices, six forward gears: a first, by the first clutch and the first brake; a second by the first clutch and the second brake; a third by the first and third clutches; a fourth by the first and second clutches; a fifth in direct drive by the second and third clutches; a sixth by the second clutch and the second brake and a reverse drive by the third clutch and the first brake. 
   According to an advantageous embodiment of this aspect of the invention, the input and output shafts being aligned, the first power path comprises a planetary gearset with three members of which one is fixed to the casing, defining the first fixed speed ratio less than one, whereas the second power path is in direct drive defining the second fixed speed ratio equal to one. 
   Similarly, according to this embodiment of this aspect of the invention, the three-member planetary gearset may comprise a planet carrier fixed to the input shaft bearing planet pinions meshed with each other and respectively with a ring gear and with a sun gear fixed to the casing, the ring gear forming the first power path of fixed ratio less than one comprising the first control clutch and the input shaft and the planet carrier forming the second power path in direct drive of fixed ratio equal to one comprising the second control clutch and the third control clutch. 
   According to another embodiment of this aspect of the invention, the double planetary gearset comprises a three-member planetary gearset having a planet carrier carrying planet pinions meshed with a sun gear and with a ring gear and additional planet pinions meshed with the planet pinions and with an additional sun gear, the first member being constituted by the additional sun gear, the second member being constituted by the ring gear, the third member being constituted by the planet carrier and the fourth member being constituted by the sun gear. 
   According to another embodiment of this other aspect of the invention, the double planetary gearset comprises a three-member planetary gearset having a planet carrier carrying planet pinions meshed with a sun gear and with a ring gear and another three-member gearset having a planet carrier carrying planet pinions meshed with each other and respectively with a ring gear and a sun gear, the first member being constituted by the sun gear, the second member being constituted by the ring gears fixed together for rotation, the third member being constituted by the planet carriers fixed together for rotation, and the fourth member being constituted by the sun gear. 
   According to still another embodiment of this aspect of the invention, the input and output shafts being parallel, on the one hand the first power path and the second power path each comprise a parallel gearset, with constant-mesh gearwheels, respectively defining the first fixed speed ratio and the second fixed speed ratio greater than the first ratio and in the same direction, and on the other hand the double planetary gearset comprises a three-member planetary gearset having a planet carrier carrying planet pinions meshed with a sun gear and with a ring gear and another three-member gearset having a planet carrier carrying planet pinions meshed with a sun gear and with a ring gear, the first member being constituted by the ring gear, the second member being constituted by the ring gear and the planet carrier fixed together for rotation, the third member being constituted by the planet carrier and the fourth member being constituted by sun gears fixed together for rotation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the invention will further emerge from the following description given by way of example with reference to the accompanying drawings in which: 
       FIG. 1  is a schematic representation of a transmission with eight forward speeds and two rear drives of a first embodiment according to a first aspect of the invention, with the input and output shafts aligned and a first type of double gearset, mounted behind a hydraulic torque converter; 
       FIG. 2  shows the selective table of the friction members for the transmission with eight forward speeds and two reverse drives according to the first aspect of the invention; 
       FIG. 3  shows a variant of the transmission of  FIG. 1 , with the addition of a freewheel device facilitating the gear change from first to second and from second to first; 
       FIG. 4  shows another variant of the transmission of  FIG. 1 , with a second type of double gearset; 
       FIG. 4A  shows a simplified variant of the embodiment of the transmission of  FIG. 4  in which the ring gears of each of the gearsets of the double gearset are equal and the adjacent planet pinions equal and mounted on the same shaft that is common to the two planet carriers; 
       FIG. 5  shows still another variant of the transmission of  FIG. 1 , with a brake operating as a start-up clutch instead of the torque converter; 
       FIG. 6  is a schematic representation of a transmission with six forward speeds and a single reverse drive of a first embodiment according to a second aspect of the invention; 
       FIG. 7  is a schematic representation of a second embodiment of the transmission with eight forward speeds and two reverse drives in which the input and output shafts are parallel, with a third type of double gearset; 
       FIG. 8  shows a second embodiment of the transmission with six forward speeds and a single reverse drive; and 
       FIG. 9  shows the selective table of the friction members for the transmission with six forward speeds and one reverse drive according to the second aspect of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the first embodiment of  FIG. 1 , a transmission with eight forward speeds and two reverse drives of a first embodiment according to a first aspect of the invention comprises, in a casing, an input shaft E and an output shaft S which are aligned. In a conventional way, the transmission is represented provided with a hydraulic torque converter  60  comprising an impeller  61 , a turbine  62 , a stator  63 , a freewheel device  64 , a lock-up clutch  65  and an output shaft  66  constituting the input shaft E. 
   This transmission has a planetary gearset  10  with three members comprising a planet carrier  12  fixed to the input shaft E carrying planet pinions  13  and  13   a  meshed together and respectively with the ring gear  14  driving a first control clutch C 1  and a second control clutch C 2 , and with a sun gear  11  fixed to the casing, defining a first power path P 1  having a first fixed speed ratio or reduction ratio G 1  less than one. 
   The input shaft E and the planet carrier  12  respectively drive a third control clutch C 3  and a fourth control clutch C 4  and define a second power path P 2  in direct drive, the second fixed speed ratio G 2  being equal to one. 
   In this first embodiment, the transmission has a double planetary gearset  50  of Ravigneaux type with four members referenced A, B, C, D in the order of their respective speeds comprising a three-member planetary gearset  20  having a planet carrier  22  carrying planet pinions  23  meshed with a sun gear  21  and with a ring gear  24 , and additional planet pinions  23   a  meshed with the planet pinions  23  and with an additional sun gear  21   a.    
   Thus, the first member A is formed by the additional sun gear  21 a, the second member B is formed by the ring gear  24 , the third member C is formed by the planet carrier  22 , and the fourth member D is formed by the sun gear  21 . The first member A is associated with the first control clutch C 1 , the second member B is fixed for rotation with the output shaft S, the third member C is associated with the third control clutch C 3  and with a first control brake B 1 , and the fourth member D is associated with the second control clutch C 2 , with the fourth control clutch C 4  and with a second control brake B 2 . 
   Operation is as follows: 
   In first gear, the first control clutch C 1  and the first control brake B 1  are engaged. The first member A is driven according to the reduction ratio G 1  of the gearset  10  and the third member C is held against rotation. Motion is transmitted according to that speed ratio G 1  and the low reduction ratio of the double planetary gearset  50 . 
   In second gear, the first control clutch C 1  and the second control brake B 2  are engaged. The first member A is driven according to speed ratio G 1  and the fourth member D is held against rotation. Motion is transmitted according to speed ratio G 1  and the intermediate reduction ratio of the double planetary gearset  50 . 
   In third gear, the first and second control clutches C 1  and C 2  are engaged. The first and fourth members A and D and the double planetary gearset  50  are driven as a unit according to speed ratio G 1 . Motion is transmitted at that speed ratio. 
   In fourth gear, the first and fourth control clutches C 1  and C 4  are engaged. The first member A is driven according to speed ratio G 1  and the fourth member D is driven in direct drive. Motion is transmitted according to a first ratio intermediate between G 1  and the direct drive. 
   In fifth gear, the first and third control clutches C 1  and C 3  are engaged. The first member A is driven according to speed ratio G 1  and the third member C is driven in direct drive. Motion is transmitted according to a second ratio intermediate between G 1  and the direct drive. 
   In sixth gear, the third and fourth control clutches C 3  and C 4  are engaged. The third and fourth members C and D and the double planetary gearset  50  are driven as a unit in direct drive. Motion is transmitted in direct drive. 
   In seventh gear, the second and third control clutches C 2  and C 3  are engaged. The third member C is driven in direct drive and the fourth member D is driven according to speed ratio G 1 . Motion is transmitted according to a partial overdrive ratio of the double planetary gearset  50 . 
   In eighth gear, the third control clutch C 3  and the second control brake B 2  are engaged. The third member C is driven in direct drive and the fourth member D is held against rotation. Motion is transmitted according to the complete overdrive ratio of the double planetary gearset  50 . 
   In the braked neutral position, the first and second control brakes B 1  and B 2  are engaged. The third and fourth members C and D and the double planetary gearset  50  are held stationary as a unit. The output shaft S is held against rotation while the input shaft is free to rotate. No motion is transmitted. 
   In the first reverse drive, the second control clutch C 2  and the first control brake B 1  are engaged. The fourth member D is driven according to G 1  and the third member C is held against rotation. Motion is transmitted according to that ratio G 1  and the reverse drive ratio of the double planetary gearset  50 . 
   In second reverse drive, the fourth control clutch C 4  and the first control brake B 1  are engaged. The fourth member D is driven in direct drive and the third member C is held against rotation. Motion is transmitted according to the reverse drive ratio of the double planetary gearset  50 . 
     FIG. 2  shows the selective table of the friction members in relation with these eleven operating modes. It will be noted that these eleven modes correspond in fact to the fifteen combinations of pairs of the four control clutches and two control brakes, minus four prohibited combinations for which the input shaft E is held against rotation and the output shaft S released, i.e. those of the of the third control clutch C 3  with the first control brake B 1 , of the second control clutch C 2  with the second control brake B 2 , of the second control clutch C 2  with the fourth control clutch C 4  and of the fourth control clutch C 4  with the second control brake B 2 . It will also be noted that the change from each combination to the next, or to the one thereafter, or further, is achieved throughout the whole range by changing only one of the two friction members engaged, i.e. exclusively by single transition shifts, which readily lend themselves to any kind of control. 
   Reference will now be made to  FIGS. 3 ,  4 , and  5 , which represent three respective variants of the transmission with eight forward speeds and two reverse drives of  FIG. 1 . All parts in common with  FIG. 1  or having the same functions keep the same reference numbers. 
   In a variant of  FIG. 3 , a freewheel device R 1  is added in parallel with the first control brake B 1  to facilitate in conventional manner the gear shifts from first to second and from second to first. This freewheel device is in no way involved in the operation which remains identical to that of  FIG. 1 . 
   In a variant of  FIG. 4 , the double planetary gearset  50  is of Simpson type and comprises the three-member gearset  20  of  FIG. 1  and another three-member gearset  30  having a planet carrier  32  carrying planet pinions  33  and  33   a  meshed with each other and respectively with a ring gear  34  and a sun gear  31 . The first member A is constituted by the sun gear  31  of the gearset  30 , the second member B is constituted by the ring gears  24  and  34  of the gearsets  20  and  30  fixed for rotation together, the third member C is constituted by the planet carrier  22  and  32  of the gearsets  20  and  30  fixed for rotation together, and the fourth member D is constituted by the sun gear  21  of the gearset  20 . 
   In the embodiment of  FIG. 4A , as in the variant of  FIG. 4 , the double planetary gearset  50  is of Simpson type and comprises the three-member gearset  20  of  FIG. 1  and another three-member gearset  30  having a planet carrier  32  carrying planet pinions  33  and  33   a  meshed with each other and respectively with a ring gear  34  and a sun gear  31 . The first member A is constituted by the sun gear  31  of the gearset  30 , the second member B is constituted by the ring gears  24  and  34  of the gearsets  20  and  30  fixed for rotation together, the third member C is constituted by the planet carrier  22  and  32  of the gearsets  20  and  30  fixed for rotation together, and the fourth member D is constituted by the sun gear  21  of the gearset  20 . In contrast to the variant of  FIG. 4 , the ring gears  24  and  34  are equal and the adjacent planet pinions  23  and  33  are equal and mounted on the same shaft common to the two planet carriers  22  and  32 , thus providing an overall simplification. 
   In the third variant of  FIG. 5 , the torque converter  60  is omitted, and the permanent connection to the casing of the sun gear  11  of the gearset  10  is replaced by a non-permanent connection by means of a brake Bo used as a start-up clutch. 
   According to this third variant, operation is as follows: 
   When stopped, the brake B 0  is disengaged. The first power path P 1  is interrupted and all the speeds which pass therethrough i.e. the first, the second, the third, the fourth, the fifth, the seventh and the first reverse drive are disengaged. Starting is possible in all these speeds while progressively engaging the brake B 0  exactly like a conventional start-up clutch, on the sole condition that it is made with appropriate dimensions and that appropriate cooling thereof is ensured. Of course starting is only made practically in first gear and first reverse drive, and possibly in second gear. 
   When in gear, the brake B 0  is engaged for all the forward and reverse speeds, and the operation remains identical to that of  FIG. 1 . 
   The examples  1 ,  2 , and  3  below show the excellent progression of steps of the ratios and the remarkable flexibility in the spread of these transmissions with eight forward speeds and two reverse drives, according to the first aspect of the invention. 
   EXAMPLE  1   
   FIGS.  1  to  5   
   
     
       
             
             
           
             
             
             
             
           
             
             
             
             
           
             
             
             
             
           
             
             
           
         
             
                 
             
           
           
             
                 
               Double gearset 50 (Ravigneaux 20 or 
             
             
               Planetary gearset 10 
               Simpson 20, 30) 
             
             
                 
             
           
        
         
             
               Ring gear 14 
               88 teeth 
               Ring gears 24, 34 
               88 teeth 
             
             
               Planet pinions 13 
               17 teeth 
               Planet pinions 23, 33 
               25 teeth 
             
             
               Planet pinions 13a 
               15 teeth 
               Planet pinions 23a, 33a 
               23 teeth 
             
             
               Sun gear 11 
               46 teeth 
               Sun gear 21 
               38 teeth 
             
             
               Ratio G1 
               0.477 
               Sun gears 21a, 31 
               31 teeth 
             
             
                 
             
           
        
         
             
                 
               Gears 
               Torques 
               Steps 
             
             
                 
                 
             
           
        
         
             
               2 nd  RD 
               0.432 
               2.316 
               2.095 
             
             
               1 st  RD 
               0.206 
               4.852 
               1.226 
             
             
               1 
               0.168 
               5.948 
               1.826 
             
             
               2 nd   
               0.307 
               3.257 
               1.554 
             
             
               3 rd   
               0.477 
               2.095 
               1.391 
             
             
               4 th   
               0.664 
               1.507 
               1.229 
             
             
               5 th   
               0.816 
               1.226 
               1.226 
             
             
               6 th  (direct drive) 
               1.000 
               1.000 
               1.226 
             
             
               7 th   
               1.226 
               0.816 
               1.168 
             
             
               8 th   
               1.432 
               0.698 
             
           
        
         
             
                 
               Spread: 8.52 
             
             
                 
             
           
        
       
     
   
   EXAMPLE  2   
   FIGS.  1  to  5   
   
     
       
             
             
           
             
             
             
             
           
             
             
             
             
           
             
             
             
             
           
             
             
           
         
             
                 
             
           
           
             
                 
               Double gearset 50 (Ravigneaux 20 or 
             
             
               Planetary gearset 10 
               Simpson 20, 30) 
             
             
                 
             
           
        
         
             
               Ring gear 14 
               87 teeth 
               Ring gears 24, 34 
               89 teeth 
             
             
               Planet pinions 13 
               17 teeth 
               Planet pinions 23, 33 
               26 teeth 
             
             
               Planet pinions 13a 
               15 teeth 
               Planet pinions 23a, 
               25 teeth 
             
             
               Sun gear 11 
               42 teeth 
               33a 
               37 teeth 
             
             
               Ratio G1 
               0.517 
               Sun gears 21a, 31 
             
             
                 
             
           
        
         
             
                 
               Gears 
               Torques 
               Steps 
             
             
                 
                 
             
           
        
         
             
               2 nd  RD 
               0.416 
               2.405 
               1.933 
             
             
               1 st  RD 
               0.215 
               4.650 
               1.156 
             
             
               1 st   
               0.186 
               5.377 
               1.826 
             
             
               2 nd   
               0.340 
               2.945 
               1.523 
             
             
               3 rd   
               0.517 
               1.933 
               1.321 
             
             
               4 th   
               0.683 
               1.464 
               1.210 
             
             
               5 th   
               0.826 
               1.210 
               1.210 
             
             
               6 th  (direct drive) 
               1.000 
               1.000 
               1.201 
             
             
               7 th   
               1.201 
               0.833 
               1.179 
             
             
               8 th   
               1.416 
               0.706 
             
           
        
         
             
                 
               Spread: 7.61 
             
             
                 
             
           
        
       
     
   
   EXAMPLE  3   
   FIGS.  1  to  5   
   
     
       
             
             
           
             
             
             
             
           
             
             
             
             
           
             
             
             
             
           
             
             
             
           
         
             
                 
             
           
           
             
                 
               Double gearset 50 (Ravigneaux 20 or 
             
             
               Planetary gearset 10 
               Simpson 20, 30) 
             
             
                 
             
           
        
         
             
               Ring gear 14 
               87 teeth 
               Ring gears 24, 34 
               98 teeth 
             
             
               Planet pinions 13 
               17 teeth 
               Planet pinions 23 
               32 teeth 
             
             
               Planet pinions 13a 
               15 teeth 
               Planet pinions 33 
               25 teeth 
             
             
               Sun gear 11 
               42 teeth 
               Planet pinions 23a, 33a 
               23 teeth 
             
             
               Ratio G1 
               0.517 
               Sun gear 21 
               34 teeth 
             
             
                 
                 
               Sun gears 21a, 31 
               38 teeth 
             
             
                 
             
           
        
         
             
                 
               Gears 
               Torques 
               Steps 
             
             
                 
                 
             
           
        
         
             
               2 nd  RD 
               0.347 
               2.882 
               1.933 
             
             
               1 st  RD 
               0.179 
               5.573 
               0.895 
             
             
               1 st   
               0.201 
               4.986 
               1.833 
             
             
               2 nd   
               0.368 
               2.720 
               1.407 
             
             
               3 rd   
               0.517 
               1.933 
               1.270 
             
             
               4 th   
               0.657 
               1.522 
               1.237 
             
             
               5 th   
               0.813 
               1.230 
               1.230 
             
             
               6 th  (direct drive) 
               1.000 
               1.000 
               1.167 
             
             
               7 th   
               1.167 
               0.857 
               1.154 
             
             
               8 th   
               1.347 
               0.742 
             
           
        
         
             
                 
                 
               Spread: 6.72 
             
             
                 
                 
             
           
        
       
     
   
   Reference will now be made to  FIG. 6  which represents a transmission with six forward speeds and one reverse drive according to a first embodiment of a second aspect of the invention. This transmission adopts the same general architecture as the transmission of  FIG. 1 , but in which the control clutch C 2  and the speeds dependent thereon, i.e. the third, the seventh and the first reverse speed are omitted, so reducing the transmission to six forward speeds and one reverse drive. 
   The operation of this transmission with six forward speeds and one reverse drive is the following: in first, the first control clutch C 1  and the first control brake B 1  are engaged. The first member A is driven according to the reduction ratio G 1  of the gearset  10  and the third member C is held against rotation. Motion is transmitted according to that speed ratio G 1  and the low reduction ratio of the double planetary gearset  50 . 
   In second gear, the first control clutch C 1  and the second control brake B 2  are engaged. The first member A is driven according to speed ratio G 1  and the fourth member D is held against rotation. Motion is transmitted according to speed ratio G 1  and the intermediate reduction ratio of the double planetary gearset  50 . 
   In third gear, the control clutches C 1  and C 4  (here the first and third) are engaged. The first member A is driven according to speed ratio G 1  and the fourth member D is driven in direct drive. Motion is transmitted according to a first ratio intermediate between G 1  and the direct drive. 
   In fourth gear, the control clutches C 1  and C 3  (here the first and second) are engaged. The first member A is driven according to speed ratio G 1  and the third member C is driven in direct drive. Motion is transmitted according to a second ratio intermediate between G 1  and the direct drive. 
   In fifth gear, the control clutches C 3  and C 4  (here the second and third) are engaged. The third and fourth members C and D and the double planetary gearset  50  are driven as a unit in direct drive. Motion is transmitted in direct drive. 
   In sixth gear, the control clutch C 3  (here the second) and the second control brake B 2  are engaged. The third member C is driven in direct drive and the fourth member D is held against rotation. Motion is transmitted according to the complete overdrive ratio of the double planetary gearset  50 . 
   In the braked neutral position, the first and second control brakes B 1  and B 2  are engaged. The third and fourth members C and D and the double planetary gearset  50  are held stationary as a unit. The output shaft S is held against rotation while the input shaft is free to rotate. No motion is transmitted. 
   In reverse drive, the control clutch C 4  (here the third) and the first control brake B 1  are engaged. The fourth member D is driven in direct drive and the third member C is held against rotation. Motion is transmitted according to the reverse drive ratio of the double planetary gearset  50 . 
   The selective table of the friction members thus modified is shown in  FIG. 9 . All parts in common with  FIG. 1  or having the same functions keep the same reference numbers. 
   Example  4  below shows the still excellent progression of steps of the ratios and the still well-adapted spread of this transmission with six forward speeds and one reverse drive. 
   EXAMPLE  4   
   FIG.  6   
   
     
       
             
             
           
             
             
             
             
           
             
             
             
             
           
             
             
             
             
           
             
             
           
         
             
                 
             
           
           
             
                 
               Double gearset 50 (Ravigneaux 20 or 
             
             
               Planetary gearset 10 
               Simpson 20, 30) 
             
             
                 
             
           
        
         
             
               Ring gear 14 
               77 teeth 
               Ring gears 24, 34 
               86 teeth 
             
             
               Planet pinions 13 
               15 teeth 
               Planet pinions 23 
               32 teeth 
             
             
               Planet pinions 13a 
               14 teeth 
               Planet pinions 33 
               21 teeth 
             
             
               Sun gear 11 
               41 teeth 
               Planet pinions 23a, 33a 
               20 teeth 
             
             
               Ratio G1 
               0.468 
               Sun gear 21 
               22 teeth 
             
             
                 
                 
               Sun gears 21a, 31 
               38 teeth 
             
             
                 
             
           
        
         
             
                 
               Gears 
               Torques 
               Steps 
             
             
                 
                 
             
           
        
         
             
               RD 
               0.256 
               3.909 
               1.238 
             
             
               1 st   
               0.207 
               4.841 
               1.800 
             
             
               2 nd   
               0.372 
               2.689 
               1.550 
             
             
               3 rd   
               0.576 
               1.735 
               1.326 
             
             
               4 th   
               0.765 
               1.308 
               1.308 
             
             
               5 th  (direct drive) 
               1.000 
               1.000 
               1.256 
             
             
               6 th   
               1.256 
               0.796 
             
           
        
         
             
                 
               Spread: 6.08 
             
             
                 
             
           
        
       
     
   
   Furthermore, the modifications illustrated and described above with reference to  FIGS. 3 ,  4  and  5  may also be adopted in the transmission with six forward speeds and one reverse drive of  FIG. 6 . 
   Reference will now be made to  FIG. 7  which is a schematic representation of a second embodiment of the transmission with eight forward speeds and two reverse drives according to the first aspect of the invention in which the input shaft E and the output shaft S are parallel. All parts in common with  FIGS. 1 and 7  or having the same functions keep the same reference numbers. 
   This transmission has a first parallel gearset  1  of constant-mesh gearwheels comprising a gearwheel l a  fixed to the input shaft E and a first group gearwheel  1   b , first control clutch C 1 , second control clutch C 2 , which is mounted concentrically with the output shaft S, constituting the first power path P 1  having the first fixed speed ratio G 1 . 
   This transmission also has a second parallel gearset  2  of constant-mesh gearwheels comprising a gearwheel  2   a  fixed to the input shaft E and a second group gearwheel  2   b , third control clutch C 3 , fourth control clutch C 4 , which is similarly mounted concentrically with the output shaft S, constituting the second power path P 2  having the second fixed speed ratio G 2  greater than G 1  and in the same direction. 
   In this transmission, the double planetary gearset  50  comprises the three-member gearset  20  of  FIG. 1  and another three-member gearset  40  having a planet carrier  42  carrying planet pinions  43  meshed with a sun gear  41  and a ring gear  44 . The first member A is constituted by the ring gear  44  of the gearset  40 , the second member B is constituted by the planet carrier  42  of the gearset  40  and the ring gear  24  of the gearset  20  fixed for rotation together, the third member C is constituted by the planet carrier  22  of the gearset  20 , and the fourth member D is constituted by the sun gears  21  and  41  of the gearsets  20  and  40  fixed for rotation together. 
   The four members A, B, C, D are associated with the four control clutches C 1 , C 2 , C 3 , and C 4  and two control brakes B 1 , B 2  as in  FIG. 1 . The selective table of  FIG. 2  applies without modification and the description of the operation is identical with the single exception of the disappearance of the direct drive which is replaced by the ratio G 2 . 
   Example 5 below reproduces example 1 of the first embodiment of the transmission. With very slight differences due to the inevitable constraints of meshing, the spread and the steps are all maintained and the speeds and the torques are all proportional to those of example 1 in the ratios G 2  and 1/G 2 , showing the identical results of this second embodiment of the transmission with eight forward speeds and two reverse speeds, according to the second aspect of the invention. 
   EXAMPLE  5   
   FIG.  7   
   
     
       
             
             
             
           
             
             
             
             
             
           
             
             
             
             
           
             
             
             
             
           
             
             
           
         
             
                 
                 
             
           
           
             
                 
                 
               Double gearset 50 
             
             
                 
               Parallel gearset 1, 2 
               (Simpson 20, 40) 
             
             
                 
                 
             
           
        
         
             
                 
               Gearwheel 1a 
               27 teeth 
               Ring gears 24 
               88 teeth 
             
             
                 
               Gearwheel 1b 
               51 teeth 
               Planet pinions 23 
               25 teeth 
             
             
                 
               Ratio G1 
               0.529 
               Sun gear 21 
               38 teeth 
             
             
                 
               Gearwheel 2a 
               41 teeth 
               Ring gear 44 
               81 teeth 
             
             
                 
               Gearwheel 2b 
               37 teeth 
               Planet pinions 43 
               18 teeth 
             
             
                 
               Ratio G2 
               1.108 
               Sun gear 41 
               45 teeth 
             
             
                 
                 
             
           
        
         
             
                 
               Gears 
               Torques 
               Steps 
             
             
                 
                 
             
           
        
         
             
               2 nd  RD 
               0.479 
               2.090 
               2.093 
             
             
               1 st  RD 
               0.229 
               4.374 
               1.227 
             
             
               1 st   
               0.186 
               5.368 
               1.827 
             
             
               2 nd   
               0.340 
               2.938 
               1.556 
             
             
               3 rd   
               0.529 
               1.889 
               1.390 
             
             
               4 th   
               0.736 
               1.359 
               1.229 
             
             
               5 th   
               0.905 
               1.106 
               1.225 
             
             
               6 th  (direct drive) 
               1.108 
               0.902 
               1.226 
             
             
               7 th   
               1.358 
               0.736 
               1.168 
             
             
               8 th   
               1.587 
               0.630 
             
           
        
         
             
                 
               Spread: 8.52 
             
             
                 
             
           
        
       
     
   
   Reference will now be made to  FIG. 8  which represents a second embodiment of the transmission with six forward speeds and one reverse drive, in which, as in  FIG. 7 , the input shaft (E) and the output shaft (S) are parallel. In this transmission, with respect to that illustrated in  FIG. 7 , the control clutch C 2  and the speeds which depend thereon, i.e. the third, the seventh and the first reverse drive are omitted. The selective table of the friction members is that of  FIG. 9 . All parts in common with  FIG. 7  or having the same functions keep the same reference numbers. 
   Example 6 below reproduces example 4 of the first embodiment of the transmission with six forward speeds and one reverse drive. With very slight differences due to the inevitable constraints of meshing, the spread and the steps are all maintained and the speeds and the torques are all proportional to those of example 4 in the ratios G 2  and 1/G 2 , showing the identical results of this second embodiment. 
   EXAMPLE  6   
   FIG.  8   
   
     
       
             
             
             
           
             
             
             
             
             
           
             
             
             
             
           
             
             
             
             
           
             
             
             
           
         
             
                 
                 
             
           
           
             
                 
                 
               Double gearset 50 
             
             
                 
               Parallel gearset 1, 2 
               (Simpson 20, 40) 
             
             
                 
                 
             
           
        
         
             
                 
               Gearwheel 1a 
               28 teeth 
               Ring gears 24 
               86 teeth 
             
             
                 
               Gearwheel 1b 
               53 teeth 
               Planet pinions 23 
               32 teeth 
             
             
                 
               Ratio G1 
               0.528 
               Sun gear 21 
               22 teeth 
             
             
                 
               Gearwheel 2a 
               43 teeth 
               Ring gear 44 
               86 teeth 
             
             
                 
               Gearwheel 2b 
               38 teeth 
               Planet pinions 43 
               32 teeth 
             
             
                 
               Ratio G2 
               1.132 
               Sun gear 41 
               22 teeth 
             
             
                 
                 
             
           
        
         
             
                 
               Gears 
               Torques 
               Steps 
             
             
                 
                 
             
           
        
         
             
               RD 
               0.289 
               3.455 
               1.236 
             
             
               1 st   
               0.234 
               4.270 
               1.796 
             
             
               2 nd   
               0.421 
               2.377 
               1.548 
             
             
               3 rd   
               0.651 
               1.536 
               1.327 
             
             
               4 th   
               0.864 
               1.157 
               1.309 
             
             
               5 th   
               1.132 
               0.884 
               1.256 
             
             
               6 th   
               1.421 
               0.704 
             
           
        
         
             
                 
                 
               Spread: 6.07 
             
             
                 
                 
             
           
        
       
     
   
   Of course, the invention is not limited to the embodiments described and shown for illustrative purposes only, but encompasses all variations. In particular, other arrangements of the two power paths P 1 , P 2 , the two different speed ratios G 1 , G 2 , and/or the double planetary gearset  50  will fall within the true spirit and scope of the invention as defined in the appended claims.