Abstract:
A system and method for altering the axial thrust load path within an automobile transmission eliminates the component end play in the transmission&#39;s roller clutch inner race and induces component end play in the transmission&#39;s rear sun gear. The resulting configuration moves portions of the axial thrust load path to across the roller clutch inner race and away from at least the transmission&#39;s sun gear and the reaction shell splines of the reaction shell. The system may include a kit in which an axially shortened roller clutch inner race and an appropriately sized bearing are provided. Additional kit components may include an axially shortened reaction shell. Alternatively, the roller clutch inner race and/or reaction shell may be shortened manually. A method of altering a preexisting transmission to have a new axial thrust load path is also provided.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to the field of automotive transmissions. In particular, the present invention is directed to an axial thrust load redistribution system and method for an automotive transmission. 
       BACKGROUND 
       [0002]    An automotive transmission alters the power generated by a vehicle&#39;s engine and transmits the resultant power to a drive shaft, which turns the vehicle&#39;s wheels. Bridging between the engine output and the drive shaft requires consideration of the axial thrust load forces exerted by the drive shaft, torque converter, and forces generated by the helical cut gears within the transmission during operation of the vehicle. The axial thrust load forces result from the vehicle&#39;s suspension moving up and down in response to road conditions and thereby moving the drive shaft up and down at one end so as to cause the drive shaft to pivot about a universal joint located near the transmission. The arcuate movement of the drive shaft as it pivots and the generally fixed distance between the transmission and the suspension work together to create axial loads in the transmission during suspension movement. In general, the transmission endures the axial thrust load forces along an axial thrust load path that traverses several transmission components. Over time, these axial thrust load forces lead to transmission component failure. 
       SUMMARY OF THE DISCLOSURE 
       [0003]    A transmission comprising a reaction shell spline and having an original-equipment axial thrust load path traversing the reaction shell spline, the transmission comprising: a transmission housing; an output shaft rotatable relative to the transmission housing, the output shaft having a rotational axis; a reaction shell coaxial with the rotational axis and including a cylindrical first portion proximate the transmission housing, and a cylindrical second portion proximate the output shaft; a roller clutch inner race having an edge proximate the second portion of the reaction shell; and a bearing disposed between the reaction shell and the edge, wherein the bearing and the roller clutch inner race are sized and configured to remove the original-equipment axial thrust load path from the reaction shell spline. 
         [0004]    A replacement kit for an automatic transmission having a preexisting roller clutch inner race and a preexisting spacer, the preexisting roller clutch inner race and the preexisting spacer having an original-equipment combined axial length, the replacement kit comprising: a replacement roller clutch inner race having an axial length that is shorter relative to the preexisting roller clutch inner race; and a replacement bearing sized such that the replacement roller clutch inner race and the replacement bearing have, when installed in the automatic transmission, a combined axial length greater than the original-equipment combined axial length. 
         [0005]    A method of redistributing axial thrust loads in a transmission, comprising: removing a roller clutch race from the transmission; shortening the axial length of the roller clutch inner race; remounting the roller clutch inner race in the transmission; and inserting a bearing proximate the roller clutch inner race. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    For the purpose of illustrating the invention, the drawings show aspects of one or more embodiments of the invention. However, it should be understood that the present invention is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein: 
           [0007]      FIG. 1A  is a partial longitudinal cutaway/partial longitudinal cross-sectional view of a prior art automotive transmission; 
           [0008]      FIG. 1B  is an enlarged partial longitudinal cutaway/partial longitudinal cross-sectional view of the automotive transmission of  FIG. 1A , showing the path that axial thrust loads applied by a drive shaft take through various components of the transmission; 
           [0009]      FIG. 1C  is a partially exploded partial cutaway isometric view of one of the planetary gear sets of the automotive transmission of  FIG. 1A ; 
           [0010]      FIG. 2  is an enlarged partial longitudinal cutaway/partial longitudinal cross-sectional view of the automotive transmission, showing the path that axial thrust loads applied by a drive shaft take through various components of the transmission; and 
           [0011]      FIG. 3  is a flowchart illustrating a method for redistributing axial thrust loads in an automotive transmission according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    As mentioned in the Background section above, drivetrain axial thrust loads can lead to the failure of certain components inside a transmission. The present disclosure includes ways of configuring axial thrust load paths through transmissions in a manner that reduces the incidences of failure of those components due to drivetrain axial thrust loads. For the sake of illustration, a detailed example of an axial load path modification is described below in the context of a fairly common automatic transmission, the model 4L60E transmission manufactured by General Motors, Detroit, Mich. (GM). As will be understood by those skilled in the art, though this particular transmission is used to illustrate concepts of the present invention, other transmissions may benefit from application of these concepts, such as GM model numbers 700-R4, 4L60, 4L65E, or 4L70. In addition, it is noted that while the following example is based on retrofitting an existing original equipment transmission, i.e., the 4L60E transmission, using aftermarket parts (which could be sold as a kit), the disclosed invention can be implemented in a newly designed transmission. That said, before proceeding with a detailed description of various concepts of the present invention in a retrofit context of the 4L60E transmission, the 4L60E transmission and its axial thrust load path at a critical location within the transmission are first described to give the reader a firm understanding of the issues. 
         [0013]    Referring now to  FIG. 1A , this figure shows a prior art automatic transmission  100 , particularly the GM 4L60E transmission. At a high level, transmission  100  includes, among other things, a housing  104 , a torque converter  108 , an input shaft  112 , a pair of planetary gear sets  116  (i.e., front and rear gear sets  116 A-B, respectively), a plurality of friction elements  118 , and an output shaft  120 . When in service, transmission  100  is mounted to a vehicle&#39;s engine (not shown), with torque converter  108  coupled to the engine&#39;s crank shaft (not shown). Torque converter  108  modifies the rotational power (torque and speed) from the engine crank shaft and transmits the resultant power to input shaft  112 . Input shaft  112  rotates planetary gear sets  116 , which are engaged with the output shaft  120  via one or more friction elements  118 . Planetary gear sets  116  (described further below) alter the power received from input shaft  112  and transmit the resultant power to output shaft  120 . Output shaft  120  is coupled to the vehicle&#39;s drive shaft (not shown), which drives the wheels of the vehicle with the power provided by the output shaft. 
         [0014]      FIG. 1B  illustrates a portion of transmission  100 , with a focus on front planetary gear set  116 A and rear planetary gear set  116 B, which are longitudinally spaced along transmission  100 . Each planetary gear set  116  includes a respective sun gear  124 A-B, a respective planetary carrier  128 A-B, corresponding pinion gears  132 A-B, a respective ring gear  136 A-B, and a corresponding gear support housing  140 A-B (best seen in  FIG. 1C  and described further below). A plurality of bearing assemblies  142 A-E are disposed between adjacent components of transmission  100  in order to provide for the relative rotation of one component to another. In between front planetary gear set  116 A and rear planetary gear set  116 B are a reaction shell  144  and a clutch assembly  148 , which includes a roller clutch housing  152 , a roller clutch outer race  156 , a roller clutch  160 , and a roller clutch inner race  164 , among other things. 
         [0015]    Reaction shell  144  is a unitary structure that surrounds the front planetary gear assembly  116 A. Reaction shell  144  is sized and configured such that a cylindrical first portion  168  of the reaction shell is located proximate housing  104  and a cylindrical second portion  172  of the reaction shell is located proximate output shaft  120 . The interior surface of second portion  172  includes a set of splines  176  that engage a portion of rear planetary gear assembly  116 B. First portion  168  and second portion  172  are joined via a back member  180 . A thrust washer  184  rests interpose back member  180  and front planetary gear assembly  116 A, thus allowing for the rotation of front planetary gear assembly independent of reaction shell  144 . Thrust washer  184  is typically a long-wearing flat bearing in the shape of a washer that transmits and resolves axial forces between rotating components to keep them aligned along a shaft. 
         [0016]    Roller clutch housing  152  surrounds roller clutch outer race  156 , roller clutch  160 , and roller clutch inner race  164 , with the roller clutch outer race and roller clutch being coupled to the roller clutch housing. Roller clutch inner race  164  is splined on its inner surface to a portion of the rear planetary gear set  116 B. The forward edge of roller clutch inner race  164  rests proximate a washer  188 , which allows for the rotation of the roller clutch inner race relative to reaction shell  144 . 
         [0017]      FIG. 1C  illustrates a partially exploded view of rear planetary gear set  116 B of  FIGS. 1A and 1B  that should give the reader a better sense of the components of this gear set. As mentioned above, rear planetary gear set  116 B includes planetary carrier  128 B that carries pinion gears  132 B. Pinion gears  132 B are rotatably mounted in concentric relation to longitudinal axis A-A. In this arrangement, pinion gears  132 B are disposed in evenly spaced relation between ring gear  136 B, formed in adjacent gear support housing  140 B, and sun gear  124 B, mounted to reaction shell  144 . Sun gear  124 B, rear planetary gear set  116 B, and gear support housing  140 B engage mating splines  192  on output shaft  120 . As would be readily apparent to a person skilled in the art, and as is evident from  FIG. 1B , front planetary gear set  116 A and rear planetary gear set  116 B have substantially similar configurations and therefore a full description of front planetary gear set  116 A is unnecessary. 
         [0018]    Returning to  FIG. 1B , bearing assemblies  142 A-E are disposed in transmission  100  to allow for the rotation of adjacent components. For instance, bearing assembly  142 A allows for the rotation of sun gear  124 A with respect to input shaft  112 ; bearing assembly  142 B allows for the rotation of planetary carrier  128 A with respect to sun gear  124 A; bearing assembly  142 C allows for the rotation of planetary carrier  128 A relative to gear support housing  140 A; and so forth. Typically, bearing assemblies  142  are generally disk shaped, having an inner and outer radius. The space between the inner and outer radius is occupied by a roller, or needle, bearing. 
         [0019]    Some parts in transmission  100 , such as roller clutch inner race  164 , have a small amount of play, typically called “component end play,” that allows the component to move axially within the transmission relative to other components. For instance, roller clutch inner race  164  has end play, allowing it to move forward and backward relative to the longitudinal axis of housing  104 . In contrast, sun gear  124 A, at the junction of reaction shell  144  and sun gear  124 B, does not typically have component end play. 
         [0020]    Bearing assemblies  142  and thrust washer  184  promote, when combined with the other previously described components of transmission  100 , the route for an axial thrust load path  198 . As described previously, axial thrust loads are generated in part by the vertical movement of the drive shaft, which occurs when the vehicle&#39;s suspension moves relative to the vehicle&#39;s body. As described in the Background section above, vertical movement of one end of the drive shaft with the suspension movement changes the location of output shaft  120 , such that the output shaft moves axially (i.e., backwards and forwards relative to the vehicle&#39;s engine) with respect to the rest of the transmission and thus places stress on the components along axial thrust load path  198 . 
         [0021]    In transmission  100 , axial thrust load path  198  traverses, from left to right, bearing assembly  142 A, sun gear  124 A, bearing assembly  142 B, planetary carrier  128 A, bearing assembly  142 C, gear support housing  140 A, thrust washer  184 , reaction shell  144  (proximate reaction shell splines  176 ), sun gear  124 B, bearing assembly  142 D, planetary carrier  128 B, and bearing assembly  142 E. 
         [0022]      FIG. 2  illustrates a portion of an exemplary transmission  200  made in accordance with the present invention. Specifically, example transmission  200  is a modified version of transmission  100  of  FIGS. 1A-C , which has been retrofitted to change portions of the axial thrust load path through the transmission. Therefore, generally, transmission  200  includes many of the same components described above, such as, housing  104 , torque converter (not shown), input shaft  112  (not shown), planetary gear sets  116  (i.e., front and rear gear sets  116 A-B, respectively), friction elements (not shown), and output shaft  120 . Planetary gear sets  116  include respective sun gears  124 A-B, respective planetary carriers  128 A-B, corresponding pinion gears  132 A-B, a respective ring gears  136 A-B, and corresponding gear support housings  140 A-B (best seen in  FIG. 1C  and described further below). Between front planetary gear set  116 A and rear planetary gear set  116 B is a reaction shell  204 , a roller clutch housing  152 , a roller clutch outer race  156 , a roller clutch  160 , and a roller clutch inner race  208 , among other things. 
         [0023]    In one example of transmission  200 , portions of the axial thrust load path through the transmission are changed by modifying or providing custom manufactured versions of reaction shell  204  and/or roller clutch inner race  208 , and/or by including another bearing assembly, such as bearing assembly  142 F, between reaction shell  204  and roller clutch inner race  208 . These alterations modify the amount of component end play in various components within transmission  200 , thus changing the axial thrust load path in the transmission. 
         [0024]    In an example embodiment of transmission  200 , roller clutch inner race  208  has a shorter axial length than roller clutch inner race  164  (as shown in  FIG. 1B ) and bearing assembly  142 F is disposed between roller clutch inner race  208  and reaction shell  144  (as shown in  FIG. 1B ). Reducing the axial length of roller clutch inner race  208  provides room for the replacement of washer  188  (as shown in  FIG. 1B ) with bearing assembly  142 F. Thus, roller clutch inner race  208  and bearing assembly  142 F can be designed in concert with one another to substantially eliminate any end play that would have existed in roller clutch inner race  164  in transmission  100 , thus relieving sun gear  124 B and reaction shell splines  176  and bearing  142 D from axial thrust loading and promoting an axial thrust load path  212 . 
         [0025]    Axial thrust load path  212  traverses, from left to right in  FIG. 2 , bearing assembly  142 A, sun gear  124 A, bearing assembly  142 B, planetary carrier  128 A, bearing assembly  142 C, gear support housing  140 A, a thrust washer  184 , reaction shell  204  (or reaction shell  144  from  FIG. 1B ), bearing assembly  142 F, roller clutch inner race  208 , planetary carrier  128 B, and bearing assembly  142 E. 
         [0026]    The axial length of roller clutch inner race  208  may be modified by methods known in the art or may be manufactured to have the appropriate axial length, for instance, when supplied as a component of a kit. In an alternative embodiment, bearing assembly  142 F may be a thrust washer, similar to thrust washer  184  ( FIG. 1B ). 
         [0027]    To further ensure the location of axial thrust load path  212  across the components described above, a reaction shell  204  may by included, which has a shorter axial length relative to reaction shell  144  of  FIGS. 1A-C . For example, reaction shell  204  may be sized and configured so that a gap  216  exists between an edge  220  of the reaction shell closest to sun gear  124 B. Gap  216  may provide end play in sun gear  124 B, thus limiting the axial thrust load forces on the sun gear and bearing assembly  142 D and promoting the transmission of axial thrust load forces generated by output shaft  120  along axial load force path  212 . Reaction shell  204  can be provided, for example, by reducing the axial length of reaction shell  144  ( FIG. 1B ) by grinding or other methodologies known in the art or as a new reaction shell that is manufactured to have the appropriate axial length. 
         [0028]      FIG. 3  shows a flow diagram of an axial thrust load redistribution method  300  for modifying an original equipment transmission, such as transmission  100  ( FIGS. 1A-C ), to have an axial thrust load path that traverses a roller clutch inner race, such as axial thrust load path  212  ( FIG. 2 ). With reference to  FIGS. 1B and 3 , washer  188  and roller clutch inner race  164  are removed from transmission  100  at step  304 . At step  308 , the axial length sufficient to remove end play from roller clutch inner race  164  is determined. Then, at step  312  the roller clutch inner race  164  is shortened via machining or other methods known in the art. The axial length of roller clutch inner race  164  should be sufficient so that when the roller clutch inner race and a bearing assembly are used together, such as bearing assembly  142 F ( FIG. 2 ), the resultant axial length of these two components is equal to or greater than the axial length determined at step  308 , thus removing the component end play from roller clutch inner race  164  ( FIG. 1B ). 
         [0029]    Roller clutch inner race  164  is then inserted into transmission  100  at step  316 . At step  320 , a bearing assembly or thrust washer, such as bearing assembly  142 F ( FIG. 2 ), is positioned proximate roller clutch inner race  164 . An additional step in method  300  may include step  324 , at which point reaction shell  144  is altered, typically by shortening the axial length of the reaction shell through machining or other methods known in the art, so that the reaction shell is sized to provide a gap, such as gap  216  ( FIG. 2 ), between the reaction shell and sun gear  124 B. In any event, whether reaction shell  144  is modified or not, at step  328 , transmission  100  is reassembled for reinstallation into a vehicle. 
         [0030]    It is understood that the appropriate axial length of roller clutch inner race  164  is determined, at least in part, by the size of bearing assembly  142 F or a suitable substitute, such as a thrust washer. In an alternative embodiment, roller clutch inner race  164  can be reused if, for example, a bearing assembly or thrust washer has an axial length that, when combined with roller clutch inner race  164 , removes the component end play from the roller clutch inner race, but does not move reaction shell  144  toward torque converter  108  to an extent that engagement between the reaction shell splines  176  and sun gear  124 B is compromised. In another alternative embodiment of method  300 , the roller clutch inner race  164  can be replaced at step  308  by prefabricated roller clutch inner race, such as roller clutch inner race  208 . In any event, any alternative embodiments should result in an axial length of the combination of roller clutch race  164  (or  208 ) and bearing assembly  142 F that is sufficient to remove the component end play from roller clutch inner race  164  (or  208 ). 
         [0031]    Alternatively, reaction shell  144  may be replaced by a manufactured reaction shell  204  having a size and configuration such that gap  216  exists. Generally, the alterations to reaction shell  144  should be sufficient in amount to aid in the removal of sun gear  124 B and the reaction shell splines  176  and bearing  142 D from the axial thrust load path  212  ( FIG. 2 ). 
         [0032]    In some embodiments, bearing assembly  142 F and roller clutch inner race  208  are conveniently provided as a kit for modifying an original equipment transmission prone to accelerated failure due to axial thrust loads caused by the torque converter, forces generated by the helical cut gears within the transmission, and suspension movement, such as transmission  100 . Additionally, the kit can include reaction shell  208  along with bearing assembly  142 F and roller clutch inner race  208 . In either of the preceding embodiments, the kit may include instructions regarding the method of installation, such as method  300  described above. In other embodiments, bearing assembly  142 D or roller clutch inner race  208  or reaction shell  208  may be provided individually with instructions for installation in a transmission, such as transmission  100 . 
         [0033]    Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the spirit and scope of the present invention.