Abstract:
A device for use with a vehicle transmission system includes a housing having a clutch provided therein and a first member extending from the housing and configured for coupling to a vehicle differential. The first member includes a generally hollow tube configured to carry a rotatable shaft therein. The device does not include a second member for directly coupling the device to a transmission housing or to the differential.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/796,725, which was filed May 1, 2006, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention relates generally to electronic limited slip devices and associated components for use with vehicle transmissions. 
       FIG. 1  is a schematic drawing of a portion of a vehicle  100  having an all-wheel drive transmission  110  in which a power takeoff unit (PTU)  120  is provided for transferring power from the half shaft  102  (the shaft that extends from the differential  104  to the side shaft  106 ) to a propshaft  108  that is coupled to the rear vehicle axle (not shown). In such a configuration, the PTU  120  is coupled or mounted to both the engine  130  at an engine mount and to the transmission housing  112  at a transmission mount (e.g., the PTU is coupled both to the engine and to the transmission with one or more brackets  140 ,  142 ,  144  that are secured in place with fasteners such as bolts, etc.). The PTU  120  is also contained within a relatively large and heavy housing  122  that is made of a metal such as steel or aluminum. One reason for the mounting of the PTU  120  to both the engine  130  and to the transmission  110  in this manner and for the inclusion of the relatively large and bulky housing for the PTU  120  is that because of the angular relationship of the propshaft  108  to the half shaft  106 , relatively significant forces (e.g., torque) are present during operation of the vehicle  100 . 
       FIG. 2  is a schematic view of a portion of a vehicle  200  having a front-wheel drive transmission  210  utilizing an electronic limited slip device  220  (eLSD). A carrier  224  is provided around a portion of the half shaft  202  proximate the location where the half shaft  202  is coupled to the differential  204 . As shown in such FIGURES, the eLSD  220  is traditionally also provided in a relatively large and heavy housing  222  that is made of a metal such as steel or aluminum similar to that shown in  FIG. 1  for use with a PTU  120 . This housing for the eLSD  220 , similar to that illustrated in  FIG. 1  for the PTU  120 , is conventionally mounted both to the engine  230  and to the transmission  210  with one or more brackets  240 ,  242 ,  244  that are secured in place with fasteners such as bolts, etc.  FIG. 3  illustrates a similar system as shown in  FIG. 2  (with like components having similar reference numerals in the  300  series) except, for example, for the fact that the shape of the carrier  324  differs from that of the carrier  224  shown in  FIG. 2  and an extra mounting bracket  346  is provided to secure the eLSD  320  to the engine  330 . 
       FIG. 4  is a more detailed schematic view of a portion of a vehicle  400  having a front wheel drive transmission utilizing an eLSD  420 . A carrier  424  is the form of a hollow member is provided around a portion of a half shaft  402  proumate the location where the half shaft  402  is coupled to the differential  404  and coupled using a splined arrangement  425 . The eLSD  420  includes a housing  422  that is coupled to an engine and to the transmission. A clutch  450  of the eLSD is provided within a clutch housing  452 . 
     One disadvantage associated with currently available vehicle transmissions that utilize eLSD systems is that the housing used to enclose the eLSD is relatively large and bulky, and takes up space that may be better used for other systems, devices, or components. Another disadvantage of such systems is that the housing must be made specifically for each vehicle or platform type so that it fits within the envelope (e.g., space) provided by the vehicle manufacturer and is compatible with the other components of the transmission. Such customization may result in inefficiencies in that the housing must be redesigned and new equipment (e.g., dies) must be created in order to manufacture the housings for each of the various vehicle programs or platforms. 
     SUMMARY 
     An exemplary embodiment relates to a device for use with a vehicle transmission system that includes a housing having a clutch provided therein and a first member extending from the housing and configured for coupling to a vehicle differential. The first member includes a generally hollow tube configured to carry a rotatable shaft therein. The device does not include a second member for directly coupling the device to a transmission housing or to the differential. 
     Another exemplary embodiment relates to a transmission system for a vehicle that includes a transmission comprising a housing, a differential, and an electronically limited slip device comprising a clutch housing and a tubular member extending from the clutch housing. The electronically limited slip device is coupled to the differential only by the tubular member and the electronically limited slip device is not directly coupled to the housing of the transmission. 
     Another exemplary embodiment relates to a method for assembling a transmission system for a vehicle that includes providing an electronically limited slip device comprising a clutch housing and a tubular member extending from the clutch housing, attaching the clutch housing to a vehicle engine, and coupling the tubular member to a differential without separately coupling the electronically limited slip device to the differential or to a transmission housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a portion of a vehicle having a conventional all-wheel drive transmission. 
         FIG. 2  is a schematic cross-sectional view of a portion of a vehicle having a conventional front-wheel drive transmission utilizing an electronic limited slip device. 
         FIG. 3  is a schematic cross-sectional view of a portion of a vehicle having a front-wheel drive transmission utilizing a conventional electronic limited slip device illustrating the mounting of the electronic limited slip device to the engine and transmission 
         FIG. 4  is a schematic cross-sectional view of a portion of a vehicle having a front-wheel drive transmission utilizing a conventional electronic limited slip device. 
         FIG. 5  is a schematic cross-sectional view of a portion of a vehicle having a front-wheel drive transmission utilizing an electronic limited slip device according to an exemplary embodiment. 
         FIG. 6  is a perspective view of an electronic limited slip device according to an exemplary embodiment. 
         FIG. 7  is a cutaway perspective view of the electronic limited slip device shown in  FIG. 6 . 
         FIG. 8  is a perspective view of the electronic limited slip device shown in  FIG. 6  provided within a transmission envelope according to an exemplary embodiment. 
         FIG. 9  is a schematic cross-sectional view of an electronic limited slip device according to an exemplary embodiment. 
         FIG. 10  is another schematic cross-sectional view of an electronic limited slip device according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to an exemplary embodiment, an electronic limited slip device (eLSD) for a vehicle such as an automobile includes a clutch provided within a clutch housing and a carrier for a shaft coupled to the clutch housing and configured to be coupled to a portion of a transmission. The carrier is configured to couple the eLSD to the transmission without a separate housing provided around the carrier as may be used in conventional eLSD. The eLSD is also configured to be coupled to a portion of a vehicle engine (e.g., by brackets). Such an eLSD system may be used with a variety of vehicle programs or platforms without the need to design a new, custom, housing for each new vehicle program or platform (e.g., the eLSD system may be used interchangeably on a variety of different types of vehicle programs or platforms). Such an eLSD system may be used with a variety of vehicle programs or platforms without the need to design a new, custom, housing for each new vehicle program or platform (e.g., the eLSD system may be used interchangeably on a variety of different types of vehicle programs or platforms). 
     Another exemplary embodiment relates to a transmission system for a vehicle that includes a transmission and an eLSD. The eLSD is mounted to a vehicle engine using brackets or other fasteners. The eLSD also includes a carrier for a vehicle shaft that is coupled to a portion of the transmission without a separate housing. The carrier is configured to receive a male member of the transmission therein. Either the male member or the carrier may include splines or ribs configured for receipt in grooves or channels provided in the other of the male member or carrier to couple the carrier to the male member. 
       FIG. 5  is a schematic view of a portion of a vehicle  500  having a front-wheel drive transmission  510  utilizing an eLSD  520  according to an exemplary embodiment. According to such an embodiment, the portion of the housing  552  that conventionally would have been provided proximate the location where the half shaft  502  is coupled to the differential  504  (see, e.g., housing  322  in  FIG. 3 ) is not provided such that the eLSD  520  is coupled to an engine  530  using brackets  540 ,  542  or similar means and there is no need to provide direct attachment of the eLSD  520  to the transmission  510 . The carrier  524  that is conventionally provided in the same region has been retained. 
     The inventors have recognized that because the eLSD  520  does not transfer power between the front-mounted transmission  510  and the rear axle (as is the case in the case of a PTU  120  as shown in  FIG. 1 ), there are no significant forces (e.g., torques) that are applied to the eLSD  520 . In other words, as compared to the PTU  120  used in the system shown in  FIG. 1 , there are relatively few forces applied to the eLSD  520 . Accordingly, the inventors have discovered that it is possible to remove a significant portion of the housing  552  (e.g., housing  322  shown in  FIG. 3 ) without producing degradation to the performance of the eLSD  520  or the transmission  510 . 
     Thus, as shown in  FIG. 5 , while the eLSD  520  remains mounted to the engine  530  using brackets  540 ,  542  and fasteners similar to those used in conventional transmission systems, the eLSD  520  is not enclosed in a housing  552  in the area proximate the location where the half shaft  502  is coupled to the differential  504 . A carrier  524  (e.g., a hollow cylinder or tube) similar to that shown in  FIG. 3  is still utilized according to an exemplary embodiment for providing protection for the spinning half shaft  502 . 
       FIG. 6  is a perspective view of an eLSD  620  according to an exemplary embodiment that may be used in conjunction with a system such as that shown in  FIG. 5 . The eLSD  620  includes a carrier  624  for protecting the half shaft  602 , but does not include a housing surrounding the carrier  624 . The clutch housing  652  is configured to be secured by a bracket (not shown) or other means to the engine. 
       FIG. 7  is a cutaway perspective view of the eLSD  620  shown in  FIG. 7  showing the clutch  650  and half shaft  602  provided within the eLSD  620 .  FIG. 8  illustrates the mounting of the eLSD  620  shown in  FIGS. 6 and 7  to a transmission system  610  (e.g., the eLSD  620  is shown as being provided within the envelope or space of a transmission system)  610 . 
       FIG. 9  illustrates a schematic cross-sectional view of a portion of a vehicle  700 , and shows the use of an eLSD  720  similar to that shown in  FIGS. 6-8  according to an exemplary embodiment. The carrier  724  of the eLSD is connected directly to a portion of the transmission without the need for brackets or other fasteners. According to an exemplary embodiment, a portion  712  of the transmission  710  is provided as a male member that is received within the carrier  724 , which acts as a female member for receiving the male member. The male member includes splines or ribs around the outer surface thereof that are received by grooves or channels formed on the interior surface of the carrier  724 . It should be understood that according to other exemplary embodiments, the position of these components may be reversed (e.g., the carrier may be a male member that is received within a female member of the transmission) and that the splines may be provided on the carrier (with grooves or channels provided in the portion of the transmission to which the carrier is coupled). 
       FIG. 10  illustrates a cross-sectional view of a portion of a system such as that shown in  FIG. 9  in which a portion of the half shaft  802 , carrier  824 , and eLSD  820  are shown. As illustrated in  FIG. 10 , a mounting bracket  840  may be provided as being coupled to or integrally formed with the clutch housing  852  of the eLSD  820 . The bracket  840  may be coupled or secured to the engine  830  using fasteners such as bolts and the like. 
     According to other exemplary embodiments, the carrier may be additionally secured to the transmission using brackets or the like to provide additional stability for the eLSD. One advantageous feature of eliminating the housing that normally surrounds the carrier is that a relatively significant weight savings may be realized (e.g., the weight of the metal used to form the housing in this region). Another advantageous feature is the elimination of the necessity to make custom housings depending on the particular vehicle application in which the eLSD will be used. By coupling the carrier directly to the transmission, the carrier may be used interchangeably with a variety of different vehicle programs or platforms. 
     Still another advantageous feature of eliminating the housing is that the space external to the carrier in the region formerly occupied by the housing may be used for other components of the transmission. For example, cooling channels, electronics, and/or other components may be mounted proximate the carrier. In this manner, the overall space taken by the transmission and its associated components may be reduced, to allow for the use of the eLSD in a transmission having a smaller package envelope. 
     It is important to note that the construction and arrangement of the electronic limited slip device and related components as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments of the present inventions have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present invention as defined in the appended claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the preferred and other exemplary embodiments without departing from the scope of the present inventions.