Abstract:
A power transmission assembly includes an input member adapted to receive drive torque from a source of torque, an output member adapted to provide drive torque to an output device and a bi-directional roller clutch including a first ring fixed for rotation with one of the input and output members. A second ring is spaced apart from the other of the input and output members. Rollers are positioned in aligned cam tracks formed in facing surfaces of the first and second rings. Neither the first ring nor the second ring support the input member or the output member on the other. The second ring may circumferentially index relative to the first ring for causing the rollers to ride up the cam tracks and force the second ring to frictionally engage the other of the input and output members, thereby establishing a drive connection between the input and output members.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/510,475 filed on Jul. 28, 2009, which claims the benefit of U.S. Provisional Application No. 61/084,285, filed on Jul. 29, 2008. The entire disclosure of each of the above applications is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The present disclosure generally relates to power transmission assemblies for use in automotive vehicles. More particularly, a power transmission assembly with face mounted bi-directional shift clutches is disclosed. 
         [0003]    A number of vehicles have been assembled with manual transmission or transaxle products. Typically, many development hours and dollars are expended to precisely fit a transmission within a particular vehicle. Components connected to or positioned near the transmission have particular characteristics to function in concert with each other. If a different transmission is subsequently desirable, changes to multiple components may be required depending upon the scope of the change of the transmission. 
         [0004]    Typically, many dollars and hours are associated with the design and development of the tooling required to produce the components of a particular transmission design. Much of this tooling is dedicated to producing only components associated with the specific transmission for which it was initially constructed. A design change may render this tooling less useful. 
         [0005]    A number of dual clutch transmissions have been designed to automate the shifting process and provide a power shift between sequentially numbered drive ratios. However, these transmissions may be substantially larger than a corresponding manual transmission having the same number of drive ratios. Other vehicle components may require modification to accommodate the new larger transmission. Accordingly, it may be desirable to provide an automated shift transmission sized to package within an existing manual transmission envelope to further advance the field. 
       SUMMARY 
       [0006]    The present disclosure describes a power transmission assembly including a rotary input member adapted to receive drive torque from a source of torque, a rotary output member adapted to provide drive torque to an output device and a bi-directional roller clutch. The bi-directional roller clutch includes a first ring fixed for rotation with one of the rotary input member and the rotary output member. A second ring is spaced apart from the other of the rotary input member and the rotary output member. Rollers are positioned in aligned cam tracks formed in facing surfaces of the first and second rings. Neither the first ring nor the second ring support the rotary input member or the rotary output member relative to the other. The second ring is adapted to circumferentially index relative to the first ring to cause the rollers to ride up the cam tracks and cause the second ring to frictionally engage the other of the rotary input member and the rotary output member. 
         [0007]    The present disclosure also provides a power transmission assembly including a first clutch adapted to drivingly couple a power source to a first input shaft and a second clutch adapted to drivingly couple the power source to a second input shaft. First, third and fifth drive gears are driven by the first input shaft. Second, fourth and sixth drive gears are driven by the second input shaft. First, second, third, fourth, fifth and sixth driven gears selectively drive a countershaft. The first through sixth drive gears are in meshed engagement with the corresponding first through sixth driven gears. A plurality of first through sixth bi-directional roller clutches are individually associated with respective first through sixth drive or driven gears and can be selectively actuated to establish at least six distinct gear drive ratios between the first and second input shafts and the countershaft. 
         [0008]    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 
         [0009]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0010]      FIG. 1  is a schematic depicting a six-speed, dual clutch transmission equipped with face mounted bi-directional shift clutches and constructed in accordance with the teachings of the present disclosure; 
           [0011]      FIG. 2  is a schematic depicting an optional power take-off arrangement for use with the transmission depicted in  FIG. 1 ; 
           [0012]      FIG. 3  is an exploded perspective view of a face mounted bi-directional shift clutch; 
           [0013]      FIG. 4  is a fragmentary cross-sectional view of the shift clutch shown in  FIG. 3 ; 
           [0014]      FIG. 5  is an exploded perspective view of another face mounted bi-directional shift clutch; 
           [0015]      FIG. 6  is a fragmentary cross-sectional view of the clutch shown in  FIG. 5 ; 
           [0016]      FIG. 7  is an exploded perspective view of another face mounted bi-directional shift clutch; 
           [0017]      FIG. 8  is a fragmentary cross-sectional view of the clutch shown in  FIG. 7 ; 
           [0018]      FIG. 9  is a schematic depicting a seven-speed, dual clutch transmission equipped with face mounted bi-directional shift clutches of the present invention; 
           [0019]      FIG. 10  is a schematic depicting an eight-speed, dual clutch transmission equipped with face mounted bi-directional shift clutches of the present invention; 
           [0020]      FIG. 11  is a schematic depicting an eight-speed, dual clutch transmission having nested gears and bi-directional shift clutches; 
           [0021]      FIG. 12  is an exploded perspective view of a bi-directional clutch interconnecting rotatable shafts; 
           [0022]      FIG. 13  is a fragmentary cross-sectional view of the clutch and shaft arrangement shown in  FIG. 12 ; 
           [0023]      FIG. 14  is an exploded perspective view of a bi-directional clutch drivingly interconnecting telescopically arranged shafts; and 
           [0024]      FIG. 15  is a fragmentary cross-sectional view of the shaft and clutch arrangement shown in  FIG. 14 . 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
         [0026]      FIG. 1  is a schematic representing an automatic powershift transmission  10  having a dual clutch  12  driven by a main shaft  14 . During operation of dual clutch  12 , torque may be transferred from main shaft  14  to one or both of a first input shaft  20  and a second input shaft  22 . Second input shaft  22  is shaped as a tube having at least a portion of first input shaft  20  extending therethrough. Various speed gearsets are selectively operable to transfer torque from one of first input shaft  20  and second input shaft  22  to a countershaft  24 . Power is transferred from countershaft  24  through a final drive  26  to a differential assembly  28 . Axle shafts  30  are each driven by differential assembly  28  and fixed for rotation with a driven wheel (not shown). 
         [0027]    Dual clutch  12  includes a first input clutch  32  and a second input clutch  34 . First input clutch  32  is selectively operable to transfer torque from main shaft  14  to first input shaft  20 . Similarly, second input clutch  34  is selectively operable to transfer torque from main shaft  14  to second input shaft  22 . First input clutch  32  includes a first drum  36  fixed for rotation with main shaft  14 . A set of outer first clutch plates  38  are fixed for rotation with and axially moveable relative to first drum  36 . A set of inner first clutch plates  40  are fixed for rotation with a first hub  39 . Inner first clutch plates  40  are axially moveable relative to hub  39  and interleaved with outer first clutch plates  38 . Hub  39  is fixed for rotation with first input shaft  20 . A power-operated dual clutch actuator unit  41  is operable to compress outer first clutch plates  38  with inner first clutch plates  40  to transfer torque through first input clutch  32 . Clutch actuator unit  41  may be a purely electrical device, electro-mechanical or electro-hydraulic without departing from the scope of the present disclosure 
         [0028]    Second input clutch  34  includes a second drum  42  fixed for rotation with main shaft  14 . A set of outer second clutch plates  44  are fixed for rotation with and axially moveable relative to second drum  42 . A set of inner second clutch plates  46  are fixed for rotation with and axially moveable relative to a second hub  48 . Hub  48  is fixed for rotation with second input shaft  22 . Inner second clutch plates  46  are interleaved with outer second clutch plates  44 . Dual clutch actuator unit  41  is operable to cause torque transfer through second input clutch  34  by compressing outer second clutch plates  44  against inner second clutch plates  46 . 
         [0029]    A first speed gearset  50  can be selectively engaged to transfer torque from first input shaft  20  to countershaft  24 . First speed gearset  50  includes a first drive gear  52  fixed for rotation with first input shaft  20 . A first driven gear  54  is supported for rotation on countershaft  24 . First drive gear  52  is in constant meshed engagement with first driven gear  54 . A second speed gearset  56  includes a second drive gear  58  fixed for rotation with second input shaft  22 . A second driven gear  60  is rotatably supported on countershaft  24 . Second drive gear  58  is in constant meshed engagement with second driven gear  60 . A third speed gearset  62  can be selectively engaged to transfer torque from first input shaft  20  to countershaft  24  and includes a third drive gear  64  fixed for rotation with first input shaft  20 . A third driven gear  66  is rotatably supported on countershaft  24 . Third drive gear  64  is in constant meshed engagement with third driven gear  66 . A fourth speed gearset  68  can be selectively engaged to transfer torque from second input shaft  22  to countershaft  24  and includes a fourth drive gear  70  fixed for rotation with second input shaft  22 . A fourth driven gear  72  is rotatably supported on countershaft  24 . Fourth drive gear  70  is in constant meshed engagement with fourth driven gear  72 . 
         [0030]    A fifth speed gearset  74  can be selectively engaged to transfer torque from first input shaft  20  to countershaft  24  and includes a fifth drive gear  76  rotatably supported on first input shaft  20  and a fifth driven gear  78  fixed for rotation with countershaft  24 . Fifth drive gear  76  is in constant meshed engagement with fifth driven gear  78 . A sixth speed gearset  80  can be selectively engaged to transfer torque from second input shaft  22  to countershaft  24  and includes a sixth drive gear  82  rotatably supported on second input shaft  22  and a sixth driven gear  84  rotatably supported on countershaft  24 . Sixth drive gear  82  and sixth driven gear  84  are in constant meshed engagement with one another. A reverse gearset  86  includes a reverse drive gear  88  fixed for rotation with first input shaft  20 . A reverse idler gear  90  is rotatably supported on an idler shaft  92 . Reverse drive gear  88  and reverse idler gear  90  are in constant meshed engagement with one another. A reverse driven gear  94  is rotatably supported on countershaft  24 . Reverse driven gear  94  is in constant meshed engagement with reverse idler gear  90  such that countershaft  24  rotates in an opposite direction when in the reverse gear ratio as compared to the sixth speed ratios previously described. Transmission  10  also includes first, second, third, fourth, fifth, sixth and reverse shifting mechanisms. In particular,  FIG. 1  schematically depicts first through seventh face mounted bi-directional shaft clutches  140 ,  142 ,  144 ,  146 ,  148 ,  150  and  152 , respectively. The bi-directional shift clutches will be described in detail hereinafter. 
         [0031]    Final drive  26  includes an output drive gear  100  fixed for rotation with countershaft  24  and an output driven gear  102  fixed for rotation with a drive member of differential assembly  28 . Output drive gear  100  and output driven gear  102  are in constant meshed engagement with one another. As previously mentioned, differential assembly  28  transfers power to axle shafts  30 . The gearing arrangement previously described permits selective establishment of six forward drive ratios and one rear drive ratio for a two-wheel drive powertrain.  FIG. 1  depicts an optional hypoid power take-off assembly  110  operable to transfer power from main shaft  14  to another set of driven axles (not shown). Because hypoid power take-off assembly  110  is optional, its components are shown in hidden line representation. Hypoid power take-off assembly  110  includes an output gear  112  fixed for rotation with a pinion shaft  114 . Output gear  112  is in constant meshed engagement with fifth driven gear  78 . A pinion gear  116  is formed at one end of pinion shaft  114 . A hypoid gear  118  is in constant meshed engagement with pinion gear  116 . Hypoid gear  118  is fixed for rotation with an output shaft  120 . It is contemplated that output shaft  120  is drivingly coupled to a secondary drive line to provide torque to another set of driven wheels that are not associated with axle shafts  30 . 
         [0032]      FIG. 2  represents an alternate power take-off assembly  124  operable to transfer torque to another set of driven wheels other than those associated with axle shafts  30 . Hypoid power take-off assembly  110  may be replaced with power take-off assembly  124  if a different gear packaging arrangement is desired. Power take-off assembly  124  includes an output gear  126  fixed for rotation with a support shaft  128 . A crossed-axis, single enveloping worm gearset  130  transfers torque from output gear  126  to an output shaft  132 . 
         [0033]    Operation of transmission  10  includes transferring power from main shaft  14  selectively through various gearsets to provide first through sixth forward drive ratios as well as a reverse drive ratio. To provide power at the first gear drive ratio, a first power-operated clutch actuator  154  places first face mounted bi-directional shift clutch  140  in an active mode where relative rotation between first driven gear  54  and countershaft  24  causes first shift clutch  140  to lock and transfer torque. The remaining bi-directional shift clutches may remain or are placed in an inactive or over-running mode such that torque is not transferred from their respective gearsets to the shafts about which they rotate. Due to the dual input shaft arrangement previously described, second bi-directional shift clutch  142 , fourth bi-directional shift clutch  146  and sixth bi-directional shift clutch  150  may be in their active mode positions with no detriment to transmission operation. This may occur because second input clutch  34  will be in the open or disengaged position during transmission operation in the first forward gear ratio. Dual clutch actuator unit  41  places first input clutch  32  in the engaged or torque transferring position. As such, torque is transferred from main shaft  14  through first input clutch  32  to first input shaft  20 . Power continues to flow through first drive gear  52 , first driven gear  54 , first bi-directional shift clutch  140 , countershaft  24 , output drive gear  100 , output driven gear  102 , differential assembly  28  and axle shafts  30 . If transmission  10  is equipped with a power take-off assembly, torque transfers therethrough as well. 
         [0034]    Prior to transferring torque through transmission  10  at the second gear drive ratio, a sequential up-shift from the first gear drive ratio to the second gear drive ratio may be anticipated by pre-selecting the position of certain shift mechanisms. To pre-select a sequential up-shift from the first gear drive ratio to the second gear drive ratio, a second power-operated actuator  158  places second bi-directional shift clutch  142  in the active mode to drivingly couple second driven gear with countershaft  24 . 
         [0035]    Transmission  10  provides for power shifting between sequential drive ratio positions. To execute a power shift, a time overlap exists between disengagement of first input clutch  32  and engagement of second input clutch  34 . Dual clutch actuator unit  41  causes simultaneous actuation and de-actuation of the clutches within dual clutch  12  to provide a smooth, uninterrupted flow of power to final drive  26 . Once first input clutch  32  is completely disengaged, first bi-directional shift clutch  140  may be placed in the inactive mode. Because transmission  10  is equipped with a number of bi-directional shift clutches, pre-selection of a next anticipated gear drive ratio is not required but may be desired to minimize any power flow interruption. 
         [0036]    A second gear to third gear shift is similarly accomplished. In particular, the third gear drive ratio may be pre-selected by energizing a third power-operated actuator  160  to place third bi-directional shift clutch  144  in the active mode to drivingly couple third driven gear  66  with countershaft  24 . To shift from second gear to third gear, dual clutch actuator unit  41  disengages second input clutch  34  while first input clutch  32  is engaged. Once a third gear drive ratio is established, power flows from main shaft  14  through first input clutch  32 , first input shaft  20 , third drive gear  64 , third driven gear  66 , third bi-directional shift clutch  144 , countershaft  24  and final drive  26  to differential assembly  28 . Once the third gear drive ratio has been established, second bi-directional shift clutch  142  may be placed in the inactive mode. 
         [0037]    It should be appreciated that additional sequential up-shifts may be completed in similar fashion to the shifts previously described. Fourth, fifth, sixth and seventh power-operated actuators  162 ,  164 ,  166   168  cooperate with fourth, fifth, sixth and seventh bi-directional shift clutches  146 ,  148 ,  150  and  152  to control transmission operation. Furthermore, transmission  10  is operable to shift from an odd numbered gear to an odd numbered gear or an even numbered gear to an even numbered gear due to the presence of the first through sixth bi-directional shift clutches. 
         [0038]    To obtain the reverse gear ratio, seventh bi-directional shift clutch  152  is actuated by seventh power-operated actuator  168  to drivingly couple reverse driven gear  94  with countershaft  24 . To launch in the reverse direction, first input clutch  32  is engaged. Power is transferred from main shaft  14  through first input clutch  32 , first input shaft  20 , reverse drive gear  88 , reverse idler gear  90 , reverse driven gear  94 , seventh bi-directional shift clutch  152 , countershaft  24  and final drive  26  to differential assembly  28 . 
         [0039]      FIGS. 3 and 4  depict first face mounted bi-directional shift clutch  140 . The remaining bi-directional clutches are substantially similar to first face mounted bi-directional shift clutch  140  and will not be described in further detail. Bi-directional shift clutch  140  is a controllable, multi-mode, bi-directional overrunning roller clutch that is operable to selectively drivingly interconnect first driven gear  54  and countershaft  24 . It should be appreciated that first bi-directional shift clutch  140  is used only as a torque transfer device and not for a gear mounting purpose. In this manner, first driven gear  54  may be accurately supported for rotation on countershaft  24  by a bearing  180 . Accurate alignment of first driven gear  54  provides a desired mesh between first driven gear  54  and first drive gear  52  to assure proper torque transfer with minimal noise, vibration or harshness being generated by the gear teeth engagement. 
         [0040]    Bi-directional shift clutch  140  includes a hub  182  having a body portion  184  positioned in splined engagement with countershaft  24 . An extended ring portion or first ring  186  of hub  182  includes an inner cylindrical surface  188  concentrically mounted on or in close proximity to a cylindrical guide surface  190  partially defining an annular recess  192  in first driven gear  54 . Body portion  184  includes an outer surface having a portion  194  that is shaped as a smooth cylinder. Axially-extending arcuate cam tracks  196  are formed on the outer surface of first ring  186  on hub  182  adjacent to cylindrical portion  194 . A second ring or slider ring  200  is positioned within recess  192 . A corresponding plurality of axially-extending arcuate cam tracks  198  are formed on an inner surface of slider ring  200 . A like plurality of elongated cylindrical rollers  202  are retained within aligned sets of cam tracks  196  and  198 . Slider ring  200  is a split ring having an outer cylindrical surface  204  selectively engageable upon expansion with an inner cylindrical surface  206  of recess  192 . Slider ring  200  includes an actuation slot  208 . 
         [0041]    Bi-directional shift clutch  140  also includes a shifting sleeve  210  that is rotatably supported on cylindrical portion  194  of hub  182 . Shifting sleeve  210  includes a first radially extending flange  212  and a second radially extending flange  214  spaced apart from one another to define a groove  216 . A lug  218  axially extends from flange  214  toward actuation slot  208 . Shifting sleeve  210  is axially moveable upon actuation of first power-operated actuator  154  between first and second positions. At the first axial position, lug  218  is positioned within actuation slot  208 . When shifting sleeve  210  is moved to the second position, lug  218  is positioned outside of actuation slot  208 . A shift fork (not shown) is positioned within groove  216 . First power-operated actuator  154  is operable to translate the shift fork and move shifting sleeve  210  between its first and second positions. Movement of shifting sleeve  210  between its first and second positions places first bi-directional shift clutch  140  in one of the active and inactive modes. In particular, when shifting sleeve  210  is in the first position, lug  218  is positioned within actuation slot  208  to restrict relative rotation between slider ring  200  and hub  182 . Thus, bi-directional shift clutch  140  is placed in its inactive mode where cam tracks  196 , cam tracks  198  and cylindrical rollers  202  remain aligned with one another. As such, outer surface  204  of slider ring  200  remains spaced apart from inner surface  206  of first driven gear  54  to continue to allow relative rotation between countershaft  24  and first driven gear  54  regardless of the speed differential between these components. 
         [0042]    When first power-operated actuator  154  is commanded to translate the shift fork and move shifting sleeve  210  to its second position, shift clutch  140  is placed in its active mode. In particular, lug  218  is positioned outside of actuation slot  208 . As such, relative rotation between countershaft  24  and first driven gear  54  causes hub  182  to rotate relative to first driven gear  54  and slider ring  200 . A limited amount of relative rotation between slider ring  200  and hub  182  occurs. This limited relative rotational movement causes rollers  202  to ride up the circumferentially indexed cam tracks  196  and  198  which, in turn, causes rollers  202  to exert a radially outwardly directed force on slider ring  200 . As a result, the split slider ring  200  expands and its outer surface  204  is driven into frictional engagement with inner surface  206  of first driven gear  54 . Accordingly, shift clutch  140  is locked and first driven gear  54  is drivingly coupled to countershaft  24  to transfer torque through transmission  10  at the first speed gear ratio. It will be appreciated that bi-directional overrunning roller clutch  140  can be used in virtually any power transmission assembly used in vehicular drivetrain applications for the purpose of selectively coupling first and second rotary members. 
         [0043]      FIGS. 5 and 6  depict another version of a bi-directional shift clutch at reference numeral  230 . Bi-directional shift clutch  230  is substantially similar to clutch  140 . Accordingly, similar elements will retain their previously introduced reference numerals. It should be appreciated that clutch  230  may be used in place of any one of previously mentioned bi-directional shift clutches  140 ,  142 ,  144 ,  146 ,  148 ,  150  and  152 . Bi-directional shift clutch  230  includes a hub  232  in splined driving engagement with countershaft  24 . Bearing  180  rotatably supports a driven gear  234  on countershaft  24 . An axially extending ring portion  236  is integrally formed with driven gear  234 . A split slider ring  238  includes an outer cylindrical surface  240  selectively drivingly engageable with an inner cylindrical surface  242  of ring portion  236 . A plurality of cam tracks  252  are formed on an inner surface of slider ring  238 . A corresponding set of axially extending cam tracks  254  are formed on an outer surface of hub  232 . A plurality of rollers  256  are in alignment with sets of cam tracks  254  and  252 . A shifting sleeve  258  includes a body portion  260  slideably supported on an external surface  262  of ring portion  236 . A groove  264  is formed in body portion  260  to receive the shift fork. A leg  266  radially inwardly extends from body  260  substantially at a distance equal to a thickness of ring portion  236 . A lug  268  axially extends from the distal end of leg  266  into an actuation slot  270  formed in slider ring  238 . Shift clutch  230  functions substantially similarly to clutch  140  via axial translation of shifting sleeve  258  to establish active and inactive modes. 
         [0044]      FIGS. 7 and 8  depict another face mounted bi-directional shift clutch identified at reference numeral  276 . Clutch  276  is substantially similar to clutch  230 . As such, like elements will retain their previously introduced reference numerals. Clutch  276  differs from clutch  230  mainly in the configuration of a shifting sleeve  278  being supported on an outer substantially cylindrically shaped surface  280  of hub  232  instead of being supported on an outer surface of ring portion  236  on driven gear  234 . An axially inwardly extending lug  282  extends from shifting sleeve  278  and can be selectively positioned within actuation slot  270  formed in split slider ring  238 . Shifting sleeve  278  is axially translatable to selectively move lug  282  between first and second axial positions and place clutch  276  in one of its active and inactive modes. 
         [0045]      FIG. 9  depicts a seven-speed automatic powershift transmission  300  equipped with individual bi-directional shift clutches associated with each speed gearset. Transmission  300  is substantially similar to transmission  10 . As such, like elements will be identified with their previously introduced reference numerals having an “a” suffix. Transmission  300  differs from transmission  10  by including a seventh speed gearset  302  having a seventh drive gear  304  supported for rotation on first input shaft  20   a  and a seventh driven gear  306  fixed for rotation with countershaft  24   a . Seventh drive gear  304  is in constant meshed engagement with seventh driven gear  306 . Additionally, an eighth bi-directional shift clutch  308  is selectively moveable by an eighth power-operated actuator  310  to drivingly interconnect seventh drive gear  304  with first input shaft  20   a . Further differences between the transmissions include fifth drive gear  76   a  being fixed for rotation with first input shaft  20   a  while fifth driven gear  78   a  is rotatably supported on countershaft  24   a . Fifth bi-directional shift clutch  148   a  is also moved to coordinate with fifth driven gear  78   a.    
         [0046]    The gears associated with obtaining a reverse gear ratio are also different within transmission  300  when compared to transmission  10 . In particular, a first reverse idler gear  312  is fixed for rotation with reverse idler shaft  92   a  and in constant meshed engagement with first drive gear  52   a . A second reverse idler gear  314  is supported for rotation on idler shaft  92   a . Second reverse idler gear  314  is in constant meshed engagement with reverse driven gear  94   a . Reverse driven gear  94   a  is fixed for rotation with countershaft  24   a . Seventh bi-directional shift clutch  152   a  is operable to drivingly interconnect second reverse idler gear  314  with idler shaft  92   a  to define the reverse gear ratio. Torque is transferred through transmission  300  to provide a reverse gear ratio by actuating first input clutch  32   a  to transfer torque from main shaft  14   a  through first input clutch  32   a , first input shaft  20   a , first drive gear  52   a , first reverse idler gear  312 , seventh bi-directional shift clutch  152   a  second reverse idler gear  314 , reverse driven gear  94   a , countershaft  24   a  and final drive  26   a  to differential assembly  28   a . Transmission  300  may be equipped with an optional power take-off assembly  320 . 
         [0047]    Power take-off assembly  320  includes an output gear  322  in constant meshed engagement with reverse driven gear  94   b . Output gear  322  is fixed for rotation with a pinion shaft  324  having a pinion gear  326  fixed at one end. A ring gear  328  is in constant meshed engagement with pinion gear  326  to provide torque to an output shaft  330 . It should be appreciated that while power take-off assembly  320  is depicted as to include a bevel gear or hypoid gear assembly, other drive arrangements such as the cross axis single enveloping worm gearset  130  may be implemented without departing from the scope of the present disclosure. 
         [0048]      FIG. 10  depicts an eight-speed automatic powershift transmission identified at reference numeral  400 . Transmission  400  is equipped with individual bi-directional shift clutches associated with each speed gearset in a manner substantially similar to transmission  300 . Transmission  400  differs from transmission  300  only in that an eighth speed gearset  402  is included to provide an eighth forward speed gear ratio. Eighth speed gearset  402  includes an eighth drive gear  404  supported for rotation on second input shaft  22   b  and an eighth driven gear  405  fixed for rotation with countershaft  24   b . A ninth bi-directional shift clutch  406  is moveable by a ninth power-operated actuator  408  to selectively drivingly couple eighth drive gear  404  with second input shaft  22   b  to provide the eighth speed gear ratio. Transmission  400  may also be configured as a two wheel drive or all wheel drive device in the manner previously described. 
         [0049]      FIG. 11  depicts another eight-speed automatic powershift transmission having individual bi-directional shift clutches associated with each speed gearset and identified at reference numeral  600 . The axial positioning of various speed gearsets has been varied when compared to the transmissions previously discussed to reduce the overall length of transmission  600 . To further facilitate an axial length reduction, reduced diameter bi-directional shift clutches are used in conjunction with the larger of the drive or driven gear for a particular speed gearset such that at least a portion of the bi-directional shift clutch is nested within a pocket formed within the speed gear. The axial space occupied by a nested speed gear and bi-directional shift clutch arrangement is less than the space occupied by the other speed gear and bi-directional clutch combination. The speed gearsets are substantially similar to those previously described. As such, like elements will retain their previously introduced numerals including a “c” suffix. 
         [0050]    The gearsets are arranged to not only minimize the overall axial length of transmission  600  but also the weight. As such, the length of second input shaft  22   c  may be minimized by positioning each of the even numbered gearsets closest to dual clutch  12   c . From right to left as viewed in  FIG. 11 , the gearsets are axially arranged in sequence as second speed gearset  56   c , sixth speed gearset  80   c , fourth speed gearset  68   c , eighth speed gearset  402   c , seventh speed gearset  302 , fifth speed gearset  74   c , third speed gearset  62   c , reverse speed gearset  86   c  and first speed gearset  50   c . The relative axial position of the various bi-directional shift clutches to other bi-directional clutches as well as the axial position of each bi-directional shift clutch relative to its respective speed gear may also allow further nesting of components to reduce the axial length of transmission  600 . Accordingly, the position of each bi-directional clutch will be described. 
         [0051]    First through ninth bi-directional shift clutch and actuator assemblies  602 ,  604 ,  606 ,  608 ,  610 ,  612 ,  614 ,  616  and  618 , are depicted in  FIG. 11 . The first through eighth bi-directional shift clutches are associated with the first through eighth speed gearsets, respectively. Ninth bi-directional clutch and actuator assembly  618  is associated with second reverse idler gear  314   c . To reduce the axial length required to package second speed gearset  56   c , sixth speed gearset  80   c  and their respective bi-directional shift clutches, second bi-directional shift clutch and actuator assembly  604  is positioned in cooperation with countershaft  24   c  axially between second speed gearset  56   c  and sixth speed gearset  80   c . Sixth bi-directional clutch and actuator assembly  612  is also axially positioned between second speed gearset  56   c  and sixth speed gearset  80   c  but is positioned in cooperation with second input shaft  22   c . The reduced axial length is achieved by positioning second bi-directional clutch and actuator assembly  604  within a pocket  630  formed in second driven gear  60   c , positioning sixth bi-directional clutch and actuator assembly  612  within a pocket  632  formed in sixth drive gear  82   c  and at least partially axially overlapping second bi-directional clutch and actuator assembly  604  with sixth bi-directional clutch and actuator assembly  612 . 
         [0052]    Fourth speed gearset  68   c , eighth speed gearset  402   c , fourth bi-directional clutch and actuator assembly  608  and eighth bi-directional clutch and actuator assembly  616  are positioned in a similar nested arrangement. For example, fourth bi-directional clutch and actuator assembly  608  is positioned within a recess  634  formed in fourth driven gear  72   c . Eighth bi-directional clutch and actuator assembly  616  is positioned within a recess  636  formed in eighth drive gear  404   c . Fourth bi-directional clutch and actuator assembly  608  and eighth bi-directional clutch and actuator assembly  616  at least partially axially overlap with one another as well. 
         [0053]    To further reduce the axial length of transmission  600 , fifth speed gearset  74   c , seventh speed gearset  302   c , fifth bi-directional clutch and actuator assembly  610  and seventh bi-directional clutch and actuator assembly  614  are arranged as a nested package. It should also be appreciated that seventh speed gearset  302   c  may be positioned in at least a partially axially overlapping manner with eighth speed gearset  402   c . In particular, seventh drive gear  304   c  is positioned within a pocket  640  formed in eighth drive gear  404   c . Similarly, eighth driven gear  405   c  is positioned within a pocket  642  formed in seventh driven gear  306   c.    
         [0054]    Fifth bi-directional clutch and actuator assembly  610  is positioned within a pocket  644  formed in fifth driven gear  78   c  while seventh bi-directional clutch and actuator assembly  614  is positioned within a pocket  646  formed in seventh drive gear  304   c . Fifth bi-directional clutch and actuator assembly  610  at least partially axially overlaps seventh bi-directional clutch and actuator assembly  614 . 
         [0055]    Other condensed packaging arrangements include positioning third bi-directional clutch and actuator assembly  606  within a pocket  648  formed in third driven gear  66   c . First bi-directional clutch and actuator assembly  602  is positioned within a recess  650  formed in first driven gear  54   c . Ninth bi-directional clutch and actuator assembly  618  is positioned within a recess  652  formed in first reverse idler gear  312   c.    
         [0056]    Transmission  600  may be configured to provide torque to a two wheel drive vehicle or may include a power take-off to provide drive torque to all four wheels of a vehicle. The power take-off may include a bevel gearset or a worm gear arrangement as shown in  FIG. 2 . 
         [0057]      FIGS. 12 and 13  depict a power transmission arrangement  698  having a face mounted bi-directional shift clutch  700  operable to selectively drivingly interconnect a first shaft  702  with a second shaft  704 . The components of clutch  700  are substantially similar to those previously described in relation to clutch  230 . Differences between the arrangements include a hub  706  being fixed to or integrally formed with first shaft  702 . Cam tracks  708  are formed on hub  706 . A drum  710  is fixed to or integrally formed with second shaft  704 . The remaining components of clutch  700  are substantially similar to the components of clutch  230  and are identified with like numerals. 
         [0058]      FIGS. 14 and 15  depict another power transmission arrangement  750  including bi-directional clutch  700  selectively drivingly interconnecting a first shaft  752  with second shaft  704 . Shafts  752  and  704  are positioned in a telescopic manner with second shaft  704  rotatably supported on first shaft  752  by a bearing  756 . Clutch  700  depicted in  FIGS. 12 through 15  functions substantially similarly to clutch  230  previously described. 
         [0059]    Other features of the bi-directional shift clutches previously described include that the hub, ring/drum and slider ring can be interchangeably internal or external in form. The lug that is set between the seam or split in the slider ring may be mounted on or in unison with the hub and can be integral with the axially shifting sleeve. 
         [0060]    Each face mounted bi-directional shift clutch can be modified for length and diameter based on packaging and torque requirements, since the gear radial location is supported by a bearing surface or assembly. The roller diameter, length and count are determined by the torque requirement, clutch housing diameter and length as well as the friction coefficient between the slider ring and the hub or drum. The ramp angle and form of the cam racks controls the radial force of the roller, engagement/disengagement rate, and slider ring to hub clearance gap for drag torque or efficiency. 
         [0061]    For automotive torque applications, most components may be produced with metal material. The cam tracks can be integral, inserted or attached to the drive or the driven members. Many cam track details can be processed with powdered metal technology, stamping, rolling, forging, broaching, EDM, milling, grinding, shaping, or hobbing. The disengaging/engaging shifting sleeve may also be made from molded plastic with an integral metal lug encased therein. This will eliminate the need for nylon padding of metal shifting forks. The entire assembly can be produced with plastics for low torque applications. The face mounted bi-directional shift clutch may be a direct replacement for the traditional synchronizer/clutch assembly. 
         [0062]    Furthermore, the foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations may be made therein without departing from the spirit and scope of the disclosure as defined in the following claims.