Abstract:
A front wheel drive transmission is provided having an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes a sun gear member, a planet carrier member, and a ring gear member. The torque transmitting devices include clutches and a brake arranged within a housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/030,265, filed on Feb. 21, 2008, which is hereby incorporated in its entirety herein by reference. 
    
    
     FIELD 
     The invention relates generally to a multiple speed transmission having a plurality of planetary gear sets and a plurality of torque transmitting devices and more particularly to a transmission configured for a front wheel drive vehicle having eight or more speeds, four planetary gear sets and a plurality of torque transmitting devices. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
     A typical multiple speed transmission uses a combination of a plurality of torque transmitting mechanisms, planetary gear arrangements and fixed interconnections to achieve a plurality of gear ratios. The number and physical arrangement of the planetary gear sets, generally, are dictated by packaging, cost and desired speed ratios. 
     While current transmissions achieve their intended purpose, the need for new and improved transmission configurations which exhibit improved performance, especially from the standpoints of efficiency, responsiveness and smoothness and improved packaging, primarily reduced size and weight, is essentially constant. Accordingly, there is a need for an improved, cost-effective, compact multiple speed transmission. 
     SUMMARY 
     A transaxle is provided having an input member, an output member, a plurality of planetary gear sets, and a plurality of torque-transmitting mechanisms. The plurality of planetary gear sets each have a sun gear member, a planetary carrier member, and a ring gear member. 
     In one aspect of the present invention, the housing of the transaxle has a first wall, a second wall, and a third wall extending between the first and second walls. The first, second, third and fourth planetary gear sets are disposed within the housing. The fourth planetary gear set is adjacent the first wall, the first planetary gear set is adjacent second wall, the third planetary gear set is adjacent the fourth planetary gear set and the second planetary gear set is between the first and third planetary gear sets. 
     Moreover, the ring gear member of the first planetary gear set is permanently coupled to the sun gear member of the second planetary gear set. The ring gear member of the second planetary gear set is permanently coupled to the planet carrier member of the third planetary gear set. The ring gear member of the third planetary gear set is permanently coupled to the planet carrier member of the fourth planetary gear set. The sun gear member of the third planetary gear set is permanently coupled to the sun gear member of the fourth planetary gear set. The output member is permanently coupled to the carrier member of the fourth planetary gear set. The input member is permanently coupled to the carrier member of the first planetary gear set. The sun gear member of the first planetary gear set is permanently coupled to the housing. 
     Further, the housing has a first area defined radially inward from an outer periphery of the planetary gear sets and axially bounded by the first wall and the fourth planetary gear set, a second area defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the third and fourth planetary gear sets, a third area defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the second and third planetary gear sets, a fourth area defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the first and second planetary gear set, a fifth area defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the first planetary gear set and the second wall, and a sixth area defined radially inward from the third wall and radially outward from the outer periphery of the planetary gear sets and axially bounded by the first wall and the second wall. 
     In another aspect of the present invention, a first clutch is disposed in at least one of the first, third, fourth and sixth areas. A second clutch is disposed in at least one of the first, third and fourth areas. A third clutch is disposed in at least one of the second, fifth and sixth areas. A fourth clutch is disposed in at least one of the second, fourth, fifth and sixth areas. A brake is disposed in at least one of the first, second and sixth areas. The clutches and the brake are selectively engageable to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member. 
     In yet another aspect of the present invention, a transfer gear train is provided having a first and second transfer gear. The first transfer gear is rotatably fixed to the output member and the second transfer gear is rotatably fixed to an intermediate shaft. A differential gear set is provided for driving a pair of road wheels. A pinion gear is rotatably fixed to the intermediate shaft, and an input differential gear in mesh with the pinion gear and configured to rotatably drive the differential gear set is also provided. 
     In still another aspect of the present invention, a power transfer assembly having a first and second transfer gear, a power transfer member, a final drive planetary gear set and a differential gear set. The first transfer gear is rotatably fixed to the output member and the second transfer gear is rotatably fixed to a drive shaft. The power transfer member is rotatably coupled to the first and second transfer gear for transferring rotational energy from the first transfer gear to the second transfer gear. The final drive planetary gear set is coupled to the drive shaft for receiving a driving torque from the second transfer gear. The differential gear set is coupled to the final drive planetary gear set and to a pair of road wheels for receiving a final drive rotational torque and transferring the final drive torque to the pair of road wheels. 
     Further, areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1A  is a schematic diagram of a gear arrangement for a front wheel drive transmission, according to the principles of the present invention; 
         FIG. 1B  is a chart showing the locations of the torque transmitting devices for the arrangement of planetary gear sets of the transmission shown in  FIG. 1A , in accordance with the embodiments of the present invention; 
         FIG. 2  is a schematic diagram of a front wheel drive transaxle arrangement incorporating the gear arrangement of the transmission of  FIG. 1A  and  FIG. 1B , according to the principles of the present invention; and 
         FIG. 3  is a schematic diagram of another embodiment of a front wheel drive transaxle arrangement incorporating the gear arrangement of the transmission of  FIG. 1A  and  FIG. 1B , according to the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
     Referring now to  FIG. 1A , an embodiment of a front wheel drive multi-speed or eight speed transmission is generally indicated by reference number  10 . The transmission  10  is illustrated as a front wheel drive or transverse transmission, though various other types of transmission configurations may be employed. The transmission  10  includes a transmission housing  11 , an input shaft or member  12 , an output shaft or member  13  and a gear arrangement  15 . The input member  12  is continuously connected to an engine (not shown) or to a turbine of a torque converter (not shown). The output member  13  is continuously connected with a final drive unit (not shown) or transfer case (not shown). 
     The gear arrangement  15  of transmission  10  includes a first planetary gear set  14 , a second planetary gear set  16 , a third planetary gear set  18 , and a fourth planetary gear set  20 . The planetary gear sets  14 ,  16 ,  18  and  20  are connected between the input member  12  and the output member  13 . 
     In a preferred embodiment of the present invention, the planetary gear set  14  includes a sun gear member  14 C, a ring gear member  14 A, and a planet carrier member  14 B that rotatably supports a set of planet or pinion gears  14 D (only one of which is shown). The sun gear member  14 C is connected to transmission housing  11  with a first shaft or intermediate member  42 . The ring gear member  14 A is connected for common rotation with a second shaft or intermediate member  44  and a third shaft or intermediate member  46 . The planet carrier member  14 B is connected for common rotation with input shaft or member  12  and a fourth shaft or intermediate member  48 . The pinion gears  14 D are configured to intermesh with the sun gear member  14 C and the ring gear member  14 A. 
     The planetary gear set  16  includes a ring gear member  16 A, a planet carrier member  16 B that rotatably supports a set of planet or pinion gears  16 D and a sun gear member  16 C. The ring gear member  16 A is connected for common rotation with a fifth shaft or intermediate member  50 . The sun gear member  16 C is connected for common rotation with the second shaft or intermediate member  44 . The planet carrier member  16 B is connected for common rotation with the sixth shaft or intermediate member  52 . The pinion gears  16 D are configured to intermesh with the sun gear member  16 C and the ring gear member  16 A. 
     The planetary gear set  18  includes a ring gear member  18 A, a planet carrier member  18 B that rotatably supports a set of planet or pinion gears  18 D and a sun gear member  18 C. The ring gear member  18 A is connected for common rotation with a seventh shaft or intermediate member  54 . The sun gear member  18 C is connected for common rotation with the eighth shaft or intermediate member  56 . The planet carrier member  18 B is connected for common rotation with the fifth shaft or intermediate member  50 . The pinion gears  18 D are configured to intermesh with the sun gear member  18 C and the ring gear member  18 A. 
     The planetary gear set  20  includes a sun gear member  20 C, a ring gear member  20 A, and a carrier member  20 B that rotatably supports a set of planet or pinion gears  20 D. The sun gear member  20 C is connected for common rotation with the eighth shaft or intermediate member  56 . The ring gear member  20 A is connected for common rotation with a ninth shaft or intermediate member  58 . The planet carrier member  20 B is connected for common rotation with the output shaft or member  13  and the seventh shaft or intermediate member  54 . The pinion gears  20 D are configured to intermesh with the sun gear member  20 C and the ring gear member  20 A. 
     The transmission  10  also includes a plurality of torque-transmitting mechanisms or devices including a first clutch  26 , a second clutch  28 , a third clutch  30 , a fourth clutch  32  and a brake  34 . The first clutch  26  is selectively engagable to connect the sixth shaft or intermediate member  52  to the ninth shaft or intermediate member  58 . The second clutch  28  is selectively engagable to connect the input shaft or member  12  to the sixth intermediate member  52 . The third clutch  30  is selectively engagable to connect the fourth intermediate member  48  to the eighth intermediate shaft or member  56 . The fourth clutch  32  is selectively engagable to connect the third shaft or intermediate member  46  to the eighth shaft or intermediate member  56 . Finally, the brake  34  is selectively engagable to connect the ninth intermediate member  58  to the transmission housing  11  to restrict rotation of the member  58  relative to the transmission housing  11 . 
     The transmission  10  is capable of transmitting torque from the input shaft or member  12  to the output shaft or member  13  in at least eight forward torque ratios and one reverse torque ratio. Each of the forward torque ratios and the reverse torque ratio are attained by engagement of one or more of the torque-transmitting mechanisms (i.e. first clutch  26 , second clutch  28 , third clutch  30 , fourth clutch  32  and brake  34 ). Those skilled in the art will readily understand that a different speed ratio is associated with each torque ratio. Thus, eight forward speed ratios may be attained by the transmission  10 . 
     The transmission housing  11  includes a first wall or structural member  102 , a second wall or structural member  104  and a third wall or structural member  106 . The third wall  106  interconnects the first and second walls  102  and  104  to define a space or cavity  110 . The input shaft or member  12  and output shaft or member  13  are supported by the second wall  104  by bearings  112 . The planetary gear sets  14 ,  16 ,  18  and  20  and the torque-transmitting mechanisms  26 ,  28 ,  30 ,  32  and  34  are disposed within cavity  110 . Further, the cavity  110  has a plurality of areas or zones A, B, C, D, E, and F in which the plurality of torque transmitting mechanisms  26 ,  28 ,  30 ,  32  and  34  will be specifically positioned or mounted, in accordance with the preferred embodiments of the present invention. 
     As shown in  FIG. 1A , zone A is defined by the area or space bounded by: the first wall  102 , planetary gear set  20 , radially inward by a reference line “L” which is a longitudinal line that is axially aligned with the input shaft  12 , and radially outward by a reference line “M” which is a longitudinal line that extends adjacent an outer diameter or outer periphery of the planetary gear sets  14 ,  16 ,  18  and  20 . While reference line “M” is illustrated as a straight line throughout the several views, it should be appreciated that reference line “M” follows the outer periphery of the planetary gear sets  14 ,  16 ,  18  and  20 , and accordingly may be stepped or non-linear depending on the location of the outer periphery of each of the planetary gear sets  14 ,  16 ,  18  and  20 . Zone B is defined by the area bounded by: planetary gear set  20 , the planetary gear set  18 , radially outward by reference line “M”, and radially inward by reference line “L”. Zone C is defined by the area bounded by: the planetary gear set  18 , the planetary gear set  16 , radially outward by reference line “M”, and radially inward by reference line “L”. Zone D is defined by the area bounded by: the planetary gear set  16 , the planetary gear set  14 , radially outward by reference line “M”, and radially inward by reference line “L”. Zone E is defined by the area bounded by: the planetary gear set  14 , the second end wall  104 , radially outward by reference line “M”, and radially inward by reference line “L”. Zone F is defined by the area bounded by: the first wall  102 , the second wall  104 , radially inward by reference line “M” and radially outward by the third wall  106 . 
     In the gear arrangement  15  of transmission  10  shown in  FIG. 1A , the planetary gear set  20  is disposed closest to the first wall  102 , the planetary gear set  14  is disposed closest to the second wall  104 , the planetary gear set  18  is adjacent the planetary gear set  20 , and the planetary gear set  16  is disposed between the planetary gear sets  18  and  14 . The torque-transmitting mechanisms are intentionally located within specific Zones in order to provide advantages in overall transmission size, packaging efficiency, and reduced manufacturing complexity. In the particular example shown in  FIG. 1A , the first clutch  26  and brake  34  are disposed within Zone A, the second clutch  28  is disposed within Zone D, the third and fourth clutches  30  and  32  are disposed within Zone E. 
     However, the present invention contemplates other embodiments where the torque-transmitting mechanisms  26 ,  28 ,  30 ,  32  and  34  are disposed in the other Zones. The feasible locations of the torque-transmitting mechanisms  26 ,  28 ,  30 ,  32  and  34  within the Zones are illustrated in the chart shown in  FIG. 1B . The chart of  FIG. 1B  lists clutches and the brake in the left most column and the available zones to locate the clutch/brake in the top row. An “X” in the chart indicates that the present invention contemplates locating the clutch or brake in the zone listed in the top row. For example, brake  34  may be located in zones A, B or F and fourth clutch  32  may be located in zones B, D, E or F. 
     Referring now to  FIG. 2 , a front wheel drive powertrain  150  incorporating a transaxle  153  is illustrated, in accordance with the embodiments of the present invention. Transaxle  153  includes the transmission  10  having the gear arrangement  15  of  FIGS. 1A and 1B . Transmission  10  is mounted to an engine  152 . Engine  152  provides a driving torque through input shaft  12  to transmission  10 . Engine  152  is generally an internal combustion engine, however, the present invention contemplates other types of engines such as electric and hybrid engines. Further, transaxle  153  includes a transfer gear train  154 , a differential  156 , and a pair of drive axles  158  and  160  that drive a pair of road wheels  162  and  164 , respectively. 
     Transfer gear train  154  includes a first transfer gear  166  and a second transfer gear  168 . Output shaft or member  13  is coupled to the first transfer or spur gear  166 . First transfer gear  166  may be a straight spur gear having straight gear teeth or a helical gear having helical gear teeth. First transfer gear  166  meshes with the second transfer gear  168 . Second transfer gear  168  is rotatably fixed to an intermediate shaft or rotatable member  170 . Further, a pinion  172  is mounted to shaft  170  and intermeshes with an input differential gear  174 . Input differential gear  174  transfers driving torque to the differential  156 . Differential  156 , as conventionally known, transfers the driving torque generated by engine  152  to the two drive axles  158  and  160 . Drive axles  158  and  160  are independently driven by differential  156  to supply the driving torque to the vehicle road wheels  162  and  164 . 
     Referring now to  FIG. 3 , another embodiment of a front wheel drive powertrain  200  incorporating a transaxle  202  is illustrated, in accordance with the embodiments of the present invention. Transaxle  202  includes the gear arrangement  15  of transmission  10  of  FIGS. 1A and 1B  and is mounted to the engine  152 . Engine  152  provides a driving torque through input shaft  12  to transmission gear arrangement  10 . Further, transaxle  202  includes a transfer chain  204 , a driven sprocket or gear  206 , a differential  208 , a final drive planetary gear set  210  and a pair of drive axles  158  and  160  that drive a pair of road wheels  162  and  164 , respectively. 
     Transfer chain  204  engages at a first end  212  a drive sprocket or gear  214  and at a second end  216  the driven sprocket or gear  206 . The drive sprocket  214  is coupled to output shaft or member  13 . Driven sprocket  206  is rotatably fixed to a drive shaft or rotatable member  220 . Further, drive shaft  220  is coupled to the sun gear of the final drive planetary gear set  210  to achieve the desired gear ratio. The final drive planetary gear set  210  transfers driving torque to the differential  208  though the carrier member of the final drive planetary gear set  210  to the housing of the differential  208 . Differential  208 , as conventionally known, transfers the driving torque generated by engine  152  to the two drive axles  158  and  160  through bevel gears of differential  208 . Drive axles  158  and  160  are independently driven by differential  208  to supply the driving torque to the vehicle road wheels  162  and  164 . 
     The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.