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 brakes arranged within a transmission housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/045,727, filed on Apr. 17, 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 
     In one aspect of the present invention, a transaxle is provided having a transmission input member, a transmission output member, a plurality of planetary gear sets, and a plurality of torque-transmitting mechanisms. 
     In another aspect of the present invention, a housing having a first wall, a second wall and a third wall extending between the first and second walls is provided. 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 third planetary gear set is adjacent second wall, the first 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. 
     In yet another aspect of the present invention, each planetary gear set has a sun gear member, a ring gear member, and a planet carrier member supporting a plurality of planet gears each configured to intermesh with both the sun gear member and the ring gear member. 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 sun gear member of the first planetary gear set is permanently coupled to the sun gear member of the fourth 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. 
     In yet another aspect of the present invention, the output member is permanently coupled with the carrier members of the second and third planetary gear sets. The input member is permanently coupled with the carrier member of the first planetary gear set. 
     In yet another aspect of the present invention, 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 is defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the first and fourth planetary gear sets. A third area is defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the first and second planetary gear sets. A fourth area is defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the second and third planetary gear set. A fifth area is defined radially inward from the outer periphery of the planetary gear sets and axially bounded by the third planetary gear set and the second wall. A sixth area is 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 yet another aspect of the present invention, the first clutch is disposed in the fourth area and is selectively engageable to interconnect the ring gear member of the first planetary gear set with the sun gear member of the third planetary gear set. 
     In yet another aspect of the present invention, a second clutch is disposed in at least one of the third, fourth and fifth areas and is selectively engageable to interconnect the planet carrier member of the first planetary gear set with the sun gear member of the third planetary gear set. 
     In yet another aspect of the present invention, a third clutch is disposed in at least one of the fourth and sixth areas and is selectively engageable to interconnect the ring gear member of the second planetary gear set with the sun gear member of the third planetary gear set. 
     In yet another aspect of the present invention, a first brake is disposed in at least one of the first, fifth and sixth areas and is selectively engageable to interconnect the sun gear member of the first planetary gear set and the sun gear member of the fourth planetary gear set to the housing. 
     In yet another aspect of the present invention, a second brake is disposed in at least one of the first, fifth and sixth areas and is selectively engageable to interconnect the ring gear member of the fourth planetary gear set to the housing. 
     In still another aspect of the present invention, the clutches and the brakes are selectively engageable to establish at least eight forward speed ratios and at least one reverse speed ratio between the transmission input member and the transmission output member. 
     In still another aspect of the present invention, a power transfer assembly has a first and a second transfer gear and a power transfer member. The first transfer gear is rotatably fixed to the engine output member and the second transfer gear is rotatably fixed to the transmission input member. The power transfer member is rotatably coupled to the first and second transfer gears for transferring rotational energy from the first transfer gear to the second transfer gear. 
     In still another aspect of the present invention, a final drive planetary gear set has a final drive sun gear coupled to the transmission output member, a final drive ring gear coupled to the transmission housing and a final drive carrier member rotatably supporting a final drive plurality of pinion gears intermeshed with both the final drive sun gear and the final drive ring gear. 
     In still another aspect of the present invention, a differential gear set having a differential housing coupled to the final drive carrier member and has a pair of gears rotatably supported in the differential housing. One of the pair of the gears is rotatably fixed to one of a pair of road wheels and the other of the pair of the gears is rotatably fixed to the other one of 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; and 
         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. 
     
    
    
     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  12 , an input shaft or member  14 , an output shaft or member  16  and a gear arrangement  18 . The input member  14  is continuously connected to an engine (shown in  FIG. 2 ) or to a turbine of a torque converter (not shown). The output member  16  is continuously connected with a final drive unit (not shown) or transfer case (shown in  FIG. 2 ). 
     The gear arrangement  18  of transmission  10  includes a first planetary gear set  20 , a second planetary gear set  22 , a third planetary gear set  24 , and a fourth planetary gear set  26 . The planetary gear sets  20 ,  22 ,  24  and  26  are connected between the input member  14  and the output member  16 . 
     In a preferred embodiment of the present invention, the planetary gear set  20  includes a ring gear member  20 A, a planet carrier member  20 B that rotatably supports a set of planet or pinion gears  20 D (only one of which is shown) and a sun gear member  20 C. The ring gear member  20 A is connected for common rotation with a first shaft or intermediate member  42 . The planet carrier member  20 B is connected for common rotation with input shaft or member  14 . The sun gear member  20 C is connected for common rotation with a second shaft or intermediate member  44 . The pinion gears  20 D are each configured to intermesh with both the sun gear member  20 C and the ring gear member  20 A. 
     The planetary gear set  22  includes a ring gear member  22 A, a planet carrier member  22 B that rotatably supports a set of planet or pinion gears  22 D and a sun gear member  22 C. The ring gear member  22 A is connected for common rotation with a third shaft or intermediate member  46 . The planet carrier member  22 B is connected for common rotation with a fourth shaft or intermediate member  48 . The sun gear member  22 C is connected for common rotation with the first shaft or intermediate member  42  and a fifth shaft or intermediate member  50 . The pinion gears  22 D are each configured to intermesh with both the sun gear member  22 C and the ring gear member  22 A. 
     The planetary gear set  24  includes a ring gear member  24 A, a planet carrier member  24 B that rotatably supports a set of planet or pinion gears  24 D and a sun gear member  24 C. The ring gear member  24 A is connected for common rotation with a sixth shaft or intermediate member  52 . The planet carrier member  24 B is connected for common rotation with the output shaft or member  16  and the fourth shaft or intermediate member  48 . The sun gear member  24 C is connected for common rotation with a seventh shaft or intermediate member  54  and an eighth shaft or intermediate member  56 . The pinion gears  24 D are each configured to intermesh with both the sun gear member  24 C and the ring gear member  24 A. 
     The planetary gear set  26  includes a ring gear member  26 A, a carrier member  26 B that rotatably supports a set of planet or pinion gears  26 D and a sun gear member  26 C. The ring gear member  26 A is connected for common rotation with a ninth shaft or intermediate member  58 . The planet carrier member  26 B is connected for common rotation with the sixth shaft or intermediate member  52 . The sun gear member  26 C is connected for common rotation with the second shaft or intermediate member  44  and a tenth shaft or intermediate member  60 . The pinion gears  26 D are each configured to intermesh with both the sun gear member  26 C and the ring gear member  26 A. 
     The transmission  10  also includes a plurality of torque-transmitting mechanisms or devices including a first clutch  66 , a second clutch  68 , a third clutch  70 , a first brake  72  and a second brake  74 . The first clutch  66  is selectively engagable to connect the fifth shaft or intermediate member  50  to the seventh shaft or intermediate member  54 . The second clutch  68  is selectively engagable to connect the input shaft or member  14  to the eighth shaft or intermediate member  56 . The third clutch  70  is selectively engagable to connect the third member or intermediate member  46  to the seventh shaft or intermediate member  54 . The first brake  72  is selectively engagable to connect the tenth shaft or intermediate member  60  to the transmission housing  12  through an eleventh shaft  62  to restrict rotation of the member  60  relative to the transmission housing  12 . Finally, the second brake  74  is selectively engagable to connect the eighth shaft or intermediate member  58  to the transmission housing  12  through a twelfth shaft  64  to restrict rotation of the member  58  relative to the transmission housing  12 . 
     The transmission  10  is capable of transmitting torque from the input shaft or member  14  to the output shaft or member  16  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  66 , second clutch  68 , third clutch  70 , first brake  72  and second brake  74 ). 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  12  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 . Input shaft or member  14  is supported by the first wall  102  by bearings  112 . Output shaft or member  16  is supported by the second wall  104  by bearings  114 . The planetary gear sets  20 ,  22 ,  24  and  26  and the torque-transmitting mechanisms  66 ,  68 ,  70 ,  72  and  74  are disposed within cavity  110 . Further, cavity  110  has a plurality of areas or zones A, B, C, D, E, and F in which the plurality of torque transmitting mechanisms  66 ,  68 ,  70 ,  72  and  74  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  26 , radially inward by a reference line “L” which is a longitudinal line that is axially aligned with the input shaft  14 , 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  20 ,  22 ,  24  and  26 . While reference line “M” is illustrated as a straight line, it should be appreciated that reference line “M” follows the outer periphery of the planetary gear sets  20 ,  22 ,  24  and  26 , and accordingly may be stepped or non-linear depending on the location of the outer periphery of each of the planetary gear sets  20 ,  22 ,  24  and  26 . Zone B is defined by the area bounded by: planetary gear set  26 , the planetary gear set  20 , 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  20 , the planetary gear set  22 , 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  22 , the planetary gear set  24 , 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  24 , the second 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  102 . 
     In the gear arrangement  18  of transmission  10  shown in  FIG. 1A , the planetary gear set  26  is disposed closest to the first wall  102 , the planetary gear set  24  is disposed closest to the second wall  104 , the planetary gear set  20  is disposed adjacent the planetary gear set  26 , and the planetary gear set  22  is disposed between the planetary gear sets  20  and  24 . 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 and third clutches  66  and  70  are disposed within Zone D, the second clutch  68  is disposed within Zone C, the first brake  72  and the second brake  74  are disposed within Zone F. 
     However, the present invention contemplates other embodiments where the torque-transmitting mechanisms  66 ,  68 ,  70 ,  72  and  74  are disposed in the other Zones. The feasible locations of the torque-transmitting mechanisms  66 ,  68 ,  70 ,  72  and  74  within the Zones are illustrated in the chart shown in  FIG. 1B . The chart of  FIG. 1B  lists clutches and brakes 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, first brake  72  and second brake  74  may be located in zones A, E or F. 
     Referring now to  FIG. 2 , a front wheel drive powertrain  150  incorporating a transaxle  154  is illustrated, in accordance with the embodiments of the present invention. Transaxle  154  includes the transmission  10  having the gear arrangement  18  of  FIGS. 1A and 1B . Transaxle  154  is mounted to an engine  156 . Engine  156  produces a driving torque in an engine output shaft  157  that drives the input shaft  14  of transmission  10 , as described below. Engine  156  is generally an internal combustion engine, however, the present invention contemplates other types of engines such as electric and hybrid engines. Further, transaxle  154  includes a transfer chain or belt  158 , a drive sprocket or gear  160 , a driven sprocket or gear  162 , a differential  164 , a final drive planetary gear set  166  and a pair of drive axles  168  and  170  that drive a pair of road wheels  172  and  174 , respectively. 
     Transfer chain or belt  158  engages at a first end  180  drive sprocket or gear  160  and at a second end  182  the driven sprocket or gear  162 . The drive sprocket or gear  160  is coupled to engine output shaft or member  157 . Driven sprocket  162  is rotatably fixed to a drive shaft or rotatable member  159 . Drive shaft or rotatable member  159  is coupled to the input shaft  14  of transmission  10 . The output shaft  16  of transmission  10  is connected to an output sleeve shaft  163 . Output sleeve shaft  163  is coupled to a sun gear  190  of a final drive planetary gear set  166  to achieve the desired gear ratio. A carrier member  192  of final drive planetary gear set  166  supports a plurality of pinion gears each of which mesh with both the sun gear  190  and a ring gear  194  of final drive planetary gear set  166 . The carrier member  192  of final drive planetary gear set  166  is rotatably coupled to and transfers driving torque to a housing  196  of the differential  164 . Differential  164  transfers the driving torque generated by engine  156  to the two drive axles  168  and  170  through two sets of bevel gears  198 ,  200  rotationally supported in the differential housing. Drive axles  168  and  170  are rotatably fixed to and independently driven by the bevel gears  198 ,  200  of the differential  164  to supply the driving torque to the vehicle road wheels  172  and  174 . 
     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.