Patent Abstract:
A transmission includes a housing, an input member connectable to an engine output member, a sleeve member, and a launch clutch assembly connected to the input member and to the sleeve member, wherein the launch clutch is selectively engageable to transmit torque from the input member to the sleeve member. A first countershaft is rotatably supported within the transmission housing. A second countershaft is rotatably supported within the transmission housing. A plurality of co-planar gear sets are connected to the input member, sleeve member, and the countershafts. A plurality of torque transmitting mechanisms are provided for coupling various components of the co-planar gear sets to the input member, sleeve member, and countershafts. The selective engagement of the launch clutch assembly and the torque transmitting mechanisms establishes at least one of five forward speed ratios and a reverse speed ratio.

Full Description:
FIELD 
       [0001]    The present disclosure relates to transmissions for motor vehicles and more particularly to automatic transmissions having one or more layshafts and having a compact design and which provides multiple forward speeds or gears. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    Dual clutch transmissions are a relatively recent addition to the stable of motor vehicle transmissions which previously included manual, continuously variable and automatic transmissions. Dual clutch transmissions or DCT&#39;s as they are now commonly known, combine good fuel economy with rapidly executed shifts. From a performance standpoint, therefore, they closely duplicate the feel and operation of a conventional mechanical transmission. Additionally, they may be configured to operate as an essentially automatic or manual transmission and thus exhibit exceptional versatility. 
         [0004]    Structurally, dual clutch transmissions typically include an input shaft which drives a pair of mutually exclusively engaged input clutches. The input clutches drive a pair of countershafts which each include a plurality of gears freely rotatably disposed on the countershafts and associated synchronizer clutches. The pluralities of gears are in constant mesh with gears secured to an output shaft. Activation of a synchronizer clutch synchronizes and couples a selected gear to its countershaft. Then, the input clutch associated with that countershaft is engaged to transmit torque from the input shaft to the output shaft. Because clutches, gears and synchronizers are disposed or stacked along the countershafts, the axial length of dual clutch transmissions can create packaging issues, particularly in smaller vehicles. 
         [0005]    While there are various ways to classify or categorize dual clutch transmissions, one approach to classification relates to the type of clutch utilized in the transmission: wet or dry. A wet dual clutch transmission contains lubricating transmission fluid not only in the gear and synchronizer section but also in the input clutches. A dry dual clutch transmission, of course, includes transmission fluid in the gear and synchronizer section but not in the clutches. While wet dual clutch transmissions offer slightly better durability and longer clutch life because of the cooling provided by the transmission fluid, they exhibit higher spin losses. Moreover, the incorporation of a lubrication pump which provides pressurized lubricating and cooling fluid further affects overall efficiency. Accordingly, wet dual clutch transmissions, all other parameters being equal, typically exhibit slightly lower fuel economy than dry dual clutch transmissions. 
         [0006]    From the foregoing, it is apparent that improvements addressing both packaging and efficiency issues of dual clutch transmissions are both desirable and possible. The present invention is so directed. 
       SUMMARY 
       [0007]    A layshaft automatic transmission is provided. The transmission includes a transmission housing, an input member connectable to an engine output member, a sleeve member at least partially concentric with the input member and at least partially surrounds the input member, a launch clutch assembly connected to the input member and to the sleeve member, wherein the launch clutch is selectively engageable to transmit torque from the input member to the sleeve member, a first drive gear rotatably fixed for common rotation with the sleeve member, and a second drive gear rotatably fixed for common rotation with the input member. A first countershaft is rotatably supported within the transmission housing and is spaced apart from and parallel with the input member and the sleeve member. A second countershaft is rotatably supported within the transmission housing and is spaced apart from and parallel with the input member and the sleeve member. A first driven gear is rotatably fixed for common rotation with the first countershaft and is in mesh with the first drive gear, a second driven gear is selectively connectable for common rotation with the first countershaft and is in mesh with the second drive gear, a third driven gear is selectively connectable for common rotation with the second countershaft and is in mesh with the second drive gear, a fourth driven gear is selectively connectable for common rotation with the second countershaft and in mesh with the first driven gear, a first output gear is selectively connectable for common rotation with the first countershaft, a second output gear is selectively connectable for common rotation with the first countershaft, a third output gear is selectively connectable for common rotation with the second countershaft, and a fourth output gear is selectively connectable for common rotation with the second countershaft. A plurality of torque transmitting mechanisms are provided for coupling various combinations of the drive gears, driven gears, and output gears to the input member, sleeve member, and countershafts. The selective engagement of the launch clutch assembly and the torque transmitting mechanisms establishes at least one of five forward speed ratios and a reverse speed ratio. 
         [0008]    In one aspect of the present invention the torque transmitting mechanisms include two clutches and three synchronizer assemblies and a launch device. 
         [0009]    In another aspect of the present invention the torque transmitting mechanisms include two clutches, two synchronizer assemblies, a dog clutch and a launch device. 
         [0010]    In another aspect of the present invention the torque transmitting mechanisms include three synchronizers. 
         [0011]    In yet another aspect of the present invention the launch device is a dry clutch. 
         [0012]    In yet another aspect of the present invention the launch device is a wet clutch. 
         [0013]    In yet another aspect of the present invention the launch device is a fluid coupling. 
         [0014]    Further aspects, advantages and 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 
         [0015]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0016]      FIG. 1  is a diagrammatic view of an embodiment of a five speed layshaft transmission; 
           [0017]      FIG. 2  is a diagrammatic view of another embodiment of a five speed layshaft transmission; 
           [0018]      FIG. 3  is a diagrammatic view of yet another embodiment of a five speed layshaft transmission; 
           [0019]      FIG. 4  is a diagrammatic view of yet another embodiment of a five speed layshaft transmission; 
           [0020]      FIG. 5A  is a diagrammatic view of yet another embodiment of a five speed layshaft transmission; 
           [0021]      FIG. 5B  is a diagrammatic view of yet another embodiment of a five speed layshaft transmission; 
           [0022]      FIG. 6  is a diagrammatic view of yet another embodiment of a five speed layshaft transmission; 
           [0023]      FIG. 7  is a diagrammatic view of yet another embodiment of a five speed layshaft transmission; 
           [0024]      FIG. 8  is a diagrammatic view of yet another embodiment of a five speed layshaft transmission; 
       
    
    
       [0025]    It will be appreciated that in all of the drawings, certain components, for example, the output gears, the differential assembly and the output shafts or axles have been rotated out of radial position or gear sizes or shaft spacings have been altered in order to illustrate the components, their locations and interconnections more clearly. 
       DETAILED DESCRIPTION 
       [0026]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0027]    With reference to  FIG. 1 , a five speed transmission is illustrated and generally designated by the reference number  10 . The five speed dual clutch transmission  10  includes a housing  12  having various bores, openings, flanges and features that receive, locate, support and protect the components of the transmission  10 . The housing  12  rotatably supports an input shaft  14 . The input shaft  14  is coupled at one end to a flywheel damper assembly  15 . The flywheel damper assembly  15  receives input torque from a prime mover (not shown), such as a combustion engine, a hybrid engine, or an electric motor. The input shaft  14  is coupled at an opposite end to a launch clutch  17 . The launch clutch  17  includes a first plurality of clutch plates or discs  19  coupled to the input shaft  14  for rotation therewith. Interleaved with the first plurality of clutch plates or discs  19  is a second plurality of clutch plates or discs  21  that are coupled to and rotate with a quill or drive tube  23 . The launch clutch  17  is engageable to selectively transfer torque from the input shaft  14  to the drive tube  23 . A first, smaller input drive gear  16  is rotatably fixed to the drive tube  23  and a second, larger input drive gear  18  is fixed to the input shaft  14 . It should be appreciated that the terms “smaller” and “larger” with reference to gear sizes are utilized herein only in the most relative and general sense and primarily for the purpose of locating or identifying the gears in the respective drawing Figures. Accordingly, it should be understood that the actual gear sizes, and their relative sizes, may vary from such descriptions in order to achieve certain or specific gear ratios and/or speed changes. 
         [0028]    Also rotatably supported in the housing  12  is a first layshaft or countershaft  20  associated with the odd numbered gears: first, third and fifth and a second layshaft or countershaft  60  associated with the even numbered gears: second and fourth and reverse. However, there may be arrangements that benefit from mixing odd and even gears on a layshaft/countershaft and the above description by no means limits the scope of the invention. The first countershaft  20  and the second countershaft  60  are parallel to and spaced from the input shaft  14 . At one end of the first countershaft  20  is a first, wet input clutch assembly  22  having a first plurality of clutch plates or discs  24  coupled to the first countershaft  20  for rotation therewith. Interleaved with the first plurality of clutch plates or discs  24  is a second plurality of clutch plates or discs  26  that are coupled to and rotate with a first quill or drive tube  28 . The first wet clutch assembly  22  is engageable to selectively transfer torque from the first quill or drive tube  28  to the first countershaft  20 . 
         [0029]    Freely rotatably disposed on the first countershaft  20  is a first, larger driven gear  32  in constant mesh with the first, smaller input drive gear  16 . Freely rotatably disposed on the first drive tube  28  is a second, smaller driven gear  34  in constant mesh with the second, larger input gear  18 . Disposed between the first, larger driven gear  32  and the second, smaller driven gear  34  is the first wet, input clutch assembly  22 . 
         [0030]    Freely rotatably disposed on the first countershaft  20  is a third, larger drive gear  46  and a fourth, smaller drive gear  48  axially spaced from the third drive gear  46 . Disposed between the third, larger drive gear  46  and the fourth, smaller drive gear  48  is a first double synchronizer clutch assembly  52 . The first synchronizer clutch assembly  52  is rotationally coupled to the first countershaft  20  by a first interengaging synchronizer  54  and is free to translate axially along the first countershaft  20 . A first shift actuator assembly  56  which may be mechanical, hydraulic, electric or pneumatic, includes an output member and shift fork assembly  58  that engages and bi-directionally translates the first synchronizer clutch assembly  52 . When translated to the right or left from a neutral center position, the first synchronizer clutch assembly  52  first synchronizes the speed of the adjacent gear, either the gear  48  to the right or the gear  46  to the left, and then positively couples the synchronized gear to the first countershaft  20 . 
         [0031]    At one end of the second countershaft  60  is a second, wet input clutch assembly  62  having a first plurality of clutch plates or discs  64  coupled to the second countershaft  60  for rotation therewith. Interleaved with the first plurality of clutch plates or discs  64  is a second plurality of clutch plates or discs  66  that are coupled to and rotate with a second quill or drive tube  68 . The second wet input clutch assembly  62  is engageable to selectively transfer torque from the second quill or drive tube  68  to the second countershaft  60 . 
         [0032]    Freely rotatably disposed on the second quill or drive tube  68  is a fifth, driven gear  72  in constant mesh with the second, larger input drive gear  18  and a sixth, driven gear  74  in constant mesh with the first, larger driven gear  32 . Disposed between the fifth, driven gear  72  and the sixth, driven gear  74  is the second, wet input clutch assembly  62 . 
         [0033]    Disposed adjacent the sixth, driven gear  74  is a reverse dog clutch or single sided synchronizer clutch assembly  75 . The synchronizer clutch  74  is rotationally coupled to the second countershaft  60  by an synchronizer  77  and is free to translate axially along the second countershaft  60 . A shift actuator assembly  79  which may be hydraulic, electric or pneumatic, includes an output member and shift fork assembly  81  that engages and bi-directionally translates the synchronizer clutch assembly  75 . When translated to the right from a neutral center position, the synchronizer clutch assembly  75  first synchronizes the speed of the adjacent gear  74  and then positively couples the synchronized gear to the second countershaft  60 . 
         [0034]    Freely rotatably disposed on the second countershaft  60  is a seventh, larger drive gear  84  and an eighth, smaller drive gear  86  axially spaced from the seventh drive gear  84 . Disposed between the seventh, larger drive gear  84  and the eighth, smaller drive gear  86  is a second double synchronizer clutch assembly  88 . The second synchronizer clutch  88  is rotationally coupled to the second countershaft  60  by synchronizer  92  and is free to translate axially along the second countershaft  60 . A second shift actuator assembly  94  which may be mechanical, hydraulic, electric or pneumatic, includes an output member and shift fork assembly  96  that engages and bi-directionally translates the second synchronizer clutch assembly  88 . When translated to the right or left from a neutral center position, the second synchronizer clutch assembly  88  first synchronizes the speed of the adjacent gear, either the gear  86  to the right or the gear  84  to the left, and then positively couples the synchronized gear to the second countershaft  60 . 
         [0035]    The third, larger drive gear  46  and the seventh, larger drive gear  84  both are in constant mesh with and drive a first output or ring gear  98  that is associated with and is an input member to a differential assembly  100 . Similarly, the fourth, smaller drive gear  48  and the eighth, smaller driven gear  86  both are in constant mesh with and drive a second output or ring gear  102  that is also associated with and is an input member to the differential assembly  100 . The differential  104  is coupled to a respective pair of axles or output shafts  106  and  108   
         [0036]    In the embodiment illustrated in  FIG. 1 , the first, larger driven gear  32  is associated and active with first gear and reverse, the second, smaller driven gear  34  is associated and active with third and fifth gears, the third, larger drive gear  46  is associated and active with fifth gear and the fourth, smaller drive gear  48  is associated and active with first and third gears. The fifth, driven gear  72  is associated and active with second and fourth gears, the sixth, driven gear  74  is associated and active with reverse, the seventh, larger drive gear  84  is associated and active with fourth gear and the eighth, smaller drive gear  86  is associated and active with second gear and reverse. 
         [0037]    To engage first gear, the first double synchronizer clutch assembly  52  is translated to the right to synchronize and connect the gear  48  to the first countershaft  20 . The launch clutch  17  may then be engaged to transfer drive torque from the input shaft  14 , through the gears  16 ,  32  and  48  to the output gear  102 , the differential assembly  100  and the axles or output shafts  104  and  106 . 
         [0038]    To engage second gear, the second double synchronizer clutch assembly  88  is translated to the right to synchronize and connect the gear  86  to the second countershaft  60 . The second input clutch assembly  62  may then be engaged to transfer drive torque from the input shaft  14 , through the gears  18 ,  72  and  86  to the output gear  102 , the differential assembly  100  and the axles or output shafts  104  and  106 . 
         [0039]    To engage third gear, the first double synchronizer clutch assembly  52  is translated to the right to connect the gear  48  to the first countershaft  20 . The first input clutch assembly  22  is then engaged to transfer drive torque from the input shaft  14 , through the gears  18 ,  34  and  48  to the output gear  102 , the differential assembly  100  and the axles or output shafts  104  and  106 . 
         [0040]    To engage fourth gear, the second double synchronizer clutch assembly  88  is translated to the left to connect the gear  84  to the second countershaft  60 . The second input clutch assembly  62  is then engaged to transfer drive torque from the input shaft  14 , through t the gears  18 ,  72  and  84  to the output gear  98 , the differential assembly  100  and the axles or output shafts  104  and  106 . 
         [0041]    To engage fifth gear, the first synchronizer clutch assembly  52  is translated to the left to engage the gear  46  and connect it to the first countershaft  20 . The first input clutch assembly  22  is then engaged to transfer drive torque from the input shaft  14 , through the gears  18 ,  34  and  46  to the output gear  98 , the differential assembly  100  and the axles or output shafts  104  and  106 . 
         [0042]    Reverse is achieved by translating the synchronizer clutch assembly  79  to the right to engage the gear  74  and connect it to the second countershaft  60  and translating the second synchronizer clutch assembly  88  to the right to engage the gear  86  and connect it to the second countershaft  60 . It is also possible to use a dog clutch or a sliding reverse configuration in place of the synchronized reverse. The launch clutch  17  is then engaged to transfer drive torque from the input shaft  14 , through the gears  16 ,  32 ,  74  and  86  to the output gear  102 , the differential assembly  100  and the axles or output shafts  104  and  106 . It should be clear that there are instances where a stepped gear configuration can be used, for example to achieve a proper reverse gear while maintaining an optimum package. The direction reversal necessary for reverse is achieved by engagement of the first, driven gear  32  and the sixth, driven gear  74 , as noted above. 
         [0043]    Turning to  FIG. 2 , another embodiment of a five speed transmission is illustrated and generally indicated by reference number  200 . The transmission  200  is similar to the transmission  10  shown in  FIG. 1  and like components are indicated by like reference numbers. However, the transmission  200  further includes a hydraulic pump  202  secured to and located within the housing  12 . The pump  202  is driven by the input shaft  14  and supplies pressurized hydraulic or transmission fluid to various components of the transmission  200 . However off axis configurations are also possible with the easy access to the input shaft  14 . In addition, the transmission  200  includes a barrel cam  204  disposed on the input shaft  14  or optionally off axis parallel to the input shaft  14 . The barrel cam  204  is configured to engage multiple actuators which may include actuators  56 ,  94  and/or  77  in order to shift the synchronizers  52 ,  88  and  75 , respectively. 
         [0044]    With reference to  FIG. 3 , another embodiment of a five speed layshaft transmission is illustrated and generally indicated by reference number  300 . The transmission  300  is similar to the transmission  10  shown in  FIG. 1  and like components are indicated by like reference numbers. However, the launch clutch  17  is replaced with a dry launch clutch  317 . To accommodate the location of the dry launch clutch  317 , the input shaft  14  is replaced with a sleeve shaft  314 A and a center shaft  314 B located concentrically within the sleeve shaft  314 A. The sleeve shaft  314 A is directly coupled with a hub  318  of the launch clutch  317 . The hub  318  is in turn directly driven by an input shaft  320  interconnected to the prime mover (not shown). The drive gear  18  is rotatably connected to the sleeve shaft  314 A. 
         [0045]    The launch clutch  317  includes one or more clutch plates or discs  319  coupled to the center shaft  314 B for rotation therewith. Interleaved with the one or more clutch plates or discs  319  are mating steels  321  that are coupled to and rotate with the hub  319 . Optionally the mating steels  321  can be mated to the shaft and the friction elements can be mated to the hub or the steel functionality can be integrated into the flywheel or damper assembly. The launch clutch  317  is engageable to selectively transfer torque from the input shaft  320  to the center shaft  314 B. The drive gear  16  is rotatably connected with the center shaft  314 B. 
         [0046]    With reference to  FIG. 4 , another embodiment of a five speed layshaft transmission is illustrated and generally indicated by reference number  400 . The transmission  400  is similar to the transmission  10  shown in  FIG. 1  and like components are indicated by like reference numbers. However, the launch clutch  17  is disposed on the input shaft  14  axially between the gear  16  and the gear  18 . In addition, gear sets  46 ,  84 , and  98  have been axially switched with gear sets  48 ,  86 , and  102 . Thus, in operation, the transmission  400  provides first and third gear by translating the first synchronizer assembly  52  to the left rather than the right, fifth gear by translating the first synchronizer assembly  52  to the right rather than the left, reverse and second gear by translating the second synchronizer assembly  88  to the left rather than the right, and fourth gear by translating the second synchronizer assembly  88  to the right rather than the left. The gear ratios achieved and arrangement are merely for clarification and can vary depending on design. Locations of the clutch elements can also be changed as long as the function is preserved. For example clutches  22  and  26  can be placed to the right of gears  72  and  34  respectively. 
         [0047]    With reference to  FIG. 5A , an embodiment of a manual five speed dual clutch transmission is illustrated and generally indicated by reference number  500 . The transmission  500  is similar to the transmission  10  shown in  FIG. 1  and like components are indicated by like reference numbers. In addition the transmission  500  incorporates some of the features of transmissions  200 ,  300 , and  400 . For example, the launch clutch  17  is replaced with a dry launch clutch  517 . The manual transmission  500  includes an input shaft  514  coupled to the dry launch clutch  517 . The dry launch clutch  517  includes one or more clutch plates or discs  519  coupled to the shaft  514  for rotation therewith. Interleaved with the clutch plates or discs  519  are mating steels  521  that are coupled to and rotate with the hub  518  or alternatively integrated into a flywheel assembly in a manner similar to a manual clutch. It should be appreciated that the clutch plates  519  and mating steels  521  may be reversed. The launch clutch  517  is engageable to selectively transfer torque from the input shaft  520  to the shaft  514 . 
         [0048]    The drive gears  16  and  18  are freely rotatably disposed on the shaft  514 . A synchronizer clutch  525  is disposed between the drive gears  16  and  18 . The synchronizer clutch  525  is rotationally coupled to the center shaft  514 . A shift actuator assembly  527  which may be mechanical, hydraulic, electric or pneumatic, includes an output member and shift fork assembly  528  that engages and bi-directionally translates the synchronizer clutch assembly  525 . When translated to the left from a neutral center position, the synchronizer clutch assembly  525  first synchronizes the speed of the adjacent gear  16  and then positively couples the synchronized gear to the shaft  514 . It should be appreciated that the clutch plates  519  and mating steels  521  may be reversed. When translated to the right, the synchronizer clutch assembly  525  first synchronizes the speed of the adjacent gear  18  and then and then positively couples the synchronized gear to the shaft  514 . In this arrangement, the clutches  22  and  66  are removed and gears  34  and  72  are rotationally fixed on the first and second countershafts  20  and  60 , respectively. In addition, the synchronizer clutch  75  may be optionally removed depending upon design considerations. 
         [0049]    Finally, a barrel cam  530  may be disposed on the input shaft  14  and configured to engage the actuators  56 ,  94 , and  527  in order to shift the synchronizers  52 ,  88 , and  526 . However other means of actuation are still possible. 
         [0050]    With reference to  FIG. 5B , an alternate embodiment of a manual five speed dual clutch transmission is illustrated and generally indicated by reference number  500 ′. The transmission  500 ′ is similar to the transmission  500  shown in  FIG. 5A  and like components are indicated by like reference numbers. In addition the transmission  500 ′ incorporates some of the features of transmissions  200 ,  300 , and  400 . For example, the transmission  500 ′ replaces the synchronizer clutch  525  shown in  FIG. 5A  with two synchronizer clutches  535 ′ and  537 ′. A shift actuator assembly  539 ′ which may be mechanical, hydraulic, electric or pneumatic, includes an output member and shift fork assembly  541 ′ that engages and bi-directionally translates the synchronizer clutch assembly  525 ′. When translated to the left from a neutral center position, the synchronizer clutch assembly  535 ′ first synchronizes the speed of the adjacent gear  32  and then positively couples the synchronized gear to the countershaft  20 . When translated to the right, the synchronizer clutch assembly  535 ′ first synchronizes the speed of the adjacent gear  34  and then positively couples the synchronized gear to the countershaft  20 . A shift actuator assembly  543 ′ which may be mechanical, hydraulic, electric or pneumatic, includes an output member and shift fork assembly  545 ′ that engages and bi-directionally translates the synchronizer clutch assembly  537 ′. When translated to the left from a neutral center position, the synchronizer clutch assembly  537 ′ first synchronizes the speed of the adjacent gear  74  and then positively couples the synchronized gear to the countershaft  60 . When translated to the right, the synchronizer clutch assembly  537 ′ first synchronizes the speed of the adjacent gear  72  and then positively couples the synchronized gear to the countershaft  60 . 
         [0051]    With reference to  FIG. 6 , another embodiment of a five speed dual clutch transmission is illustrated and generally indicated by reference number  600 . The transmission  600  is similar to the transmission  300  shown in  FIG. 3  and like components are indicated by like reference numbers. However, the launch clutch  317  is replaced with a wet launch clutch  617  located inside the housing  12 . A flywheel damper assembly  619  is preferably disposed on the input shaft  320  outside the housing  12 . The launch clutch  617  is preferably located axially between the gear  18  and the housing  12  proximate the flywheel damper assembly  619 . 
         [0052]    With reference to  FIG. 7 , another embodiment of a five speed dual clutch transmission is illustrated and generally indicated by reference number  700 . The transmission  700  is similar to the transmission  10  shown in  FIG. 1  and like components are indicated by like reference numbers. However, the gear sets  16 ,  32  and  74  have been axially switched with gear sets  18 ,  34  and  72 . In addition, the launch clutch  17  is disposed between the gear sets  16  and  18  and the clutch assemblies  22  and  62  are disposed at ends of the countershafts  20  and  60 , respectively. 
         [0053]    Finally, turning to  FIG. 8 , another embodiment of a five speed dual clutch transmission is illustrated and generally indicated by reference number  800 . The transmission  800  is similar to the transmission  10  shown in  FIG. 1  and like components are indicated by like reference numbers. However, the transmission  800  includes a hydraulic coupling or other hydrodynamic starting device 802. To accommodate the hydraulic coupling  802 , the input shaft  14  is replaced with a sleeve shaft  814 A and a center shaft  814 B located concentrically within the sleeve shaft  814 A. The sleeve shaft  814 A is directly coupled with a pump  804  of the hydraulic coupling  802 . The pump  804  is in turn directly driven by an input shaft  806  interconnected to the prime mover (not shown). The drive gear  18  is rotatably connected to the sleeve shaft  814 A. 
         [0054]    The pump  804  hydraulically drives a turbine  808 . The turbine  808  is rotatingly coupled to the center shaft  814 B. The drive gear  16  is selectively, rotatably connected with the center shaft  814 B through the launch clutch  17 . Alternatively the launch clutch  17  can be eliminated and a freewheel element  820  can be added to gear  32  as shown by dashed lines in  FIG. 8 . 
         [0055]    The layshaft transmissions  10 ,  200 ,  300 ,  400 ,  500 ,  500 ′  600 ,  700 , and  800  according to the present invention provide many features and benefits. For example, there are fewer planes of gears compared to an equivalent dual clutch transmission. Additionally, the input clutches are disposed on the axes of the quills and countershafts. All of these features permit a more axially compact transmission. In fact, the nominal axial distance between the input shaft and the center of the differential is smaller than in most dual clutch transmission configurations. 
         [0056]    The solid input shaft improves hydraulic pump packaging and provides the potential for improved hybridization. The gear sets between the input shaft and the gears on the quills reduce quill, clutch and countershaft speeds and thus reduce spin losses in both the gears and the input clutches relative to conventional dual clutch transmission configurations. 
         [0057]    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.

Technology Classification (CPC): 8