Abstract:
A differential gear mechanism constructed in accordance to one example of the present disclosure can include a differential casing having a first differential case portion that defines a first output shaft opening and a second differential case portion that defines a second output shaft opening. The first differential case portion can include an annular pocket formed thereon and defined by an outer circumferential wall, an inner circumferential wall and an end wall. A piston can be slidably disposed in the annular pocket and configured to actuate a clutch assembly. A first and a second side gear can be rotatably mounted within the differential casing. The first and second side gears can be co-axially aligned along an axis of rotation of the differential casing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/049,461 filed on Oct. 9, 2013, which claims the benefit of U.S. Provisional Application No. 61/712,239 which was filed on Oct. 10, 2012, U.S. Provisional Application No. 61/843,531, which was filed on Jul. 8, 2013, and U.S. Provisional Application No. 61/878,302 which was filed on Sep. 16, 2013. The disclosures of each of the above applications are incorporated herein by reference in their entirety. 
     
    
     FIELD 
       [0002]    The present disclosure relates generally to differential gear mechanisms and more particularly to a differential case having an integrated piston housing. 
       BACKGROUND 
       [0003]    A differential gear mechanism can be provided in an axle assembly and used to transfer torque from a driveshaft to a pair of output shafts. The driveshaft can drive the differential through the use of a bevel gear that meshes with a ring gear mounted to a housing of the differential. In automotive applications, a differential allows the tires mounted at either end of the axle assembly to rotate at different speeds. This is important when the vehicle is turning because the outer tire travels over an arc of greater distance than the inner tire. Thus, the outer tire must rotate at a faster speed than the inner tire to compensate for the greater distance of travel. The differential includes a differential case and a gear arrangement that allows torque to be transferred from the driveshaft to the output shafts while concurrently allowing the output shafts to rotate at different speeds as needed. The gear arrangement can generally include a pair of side gears that are mounted for rotation with the respective output shafts. A series of cross pins or pinion gear shafts are fixedly mounted to the differential case for rotation therewith. A corresponding plurality of pinion gears are mounted for rotation with the pinion gear shafts and are in meshing relationship with both of the side gears. 
         [0004]    Some differential gear mechanisms include traction modifying differentials. Typically, a clutch pack can be disposed between one of the side gears and an adjacent surface of the differential case. The clutch pack or locking mechanism is operable to limit relative rotation between the gear case and the one side gear. In such differentials, engaging the clutch pack or locking mechanism (retarding differentiation) is achieved by one of several different approaches. Some configurations include a piston that actuates to cause the clutch pack to move between open, locked and partially locked conditions. 
         [0005]    The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
       SUMMARY 
       [0006]    A differential gear mechanism constructed in accordance to one example of the present disclosure can include a differential casing having a first differential case portion that defines a first output shaft opening and a second differential case portion that defines a second output shaft opening. The first differential case portion can include an annular pocket formed thereon and defined by an outer circumferential wall, an inner circumferential wall and an end wall. A piston can be slidably disposed in the annular pocket and configured to actuate a clutch assembly. A first and a second side gear can be rotatably mounted within the differential casing. The first and second side gears can be co-axially aligned along an axis of rotation of the differential casing. The first side gear can define a first shaft opening configured to provide a first torque transmitting connection with a first output shaft received within the first output shaft opening. The second side gear can define a second shaft opening configured to provide a second torque transmitting connection with a second output shaft received within the second output shaft opening. 
         [0007]    According to additional features the differential gear mechanism can further comprise a reaction block disposed on the first differential case portion. The reaction block can be configured to transfer a first side gear separation force onto the first differential case portion. The first differential case can further include an annular lip formed in part by the inner circumferential wall. The reaction block can be disposed on the annular lip. 
         [0008]    According to still other features the reaction block can include a radial arm and a ledge. The ledge can rest against the annular lip of the reaction block. The radial arm opposes the inner circumferential wall of the annular pocket of the first differential case. The first side gear defines an annular channel that nestingly receives the reaction block therein. The reaction block can define a plurality of bores therethrough. The reaction block can be conical. 
         [0009]    According to other features the first differential case can define a plurality of blind bores that receive planet gear shafts from a planetary gear set. The differential assembly can further include a first o-ring disposed between the piston and the outer circumferential wall of the annular pocket. A second o-ring can be disposed between the piston and the inner circumferential wall of the annular pocket. A washer can be disposed between the reaction block and the first side gear. 
         [0010]    A differential gear mechanism constructed in accordance to another example of the present disclosure can include a differential casing having a first differential case portion that defines a first output shaft opening and a second differential case portion that defines a second output shaft opening. The first differential case portion can include an annular pocket formed thereon. A piston can be slidably disposed in the annular pocket and configured to actuate a clutch assembly. A first and a second side gear can be rotatably mounted within the differential casing. The first and second side gears can be co-axially aligned along an axis of rotation of the differential casing. The first side gear can define a first shaft opening configured to provide a first torque transmitting connection with a first output shaft received within the first output shaft opening. The second side gear can define a second shaft opening configured to provide a second torque transmitting connection with a second output shaft received within the second output shaft opening. A reaction block can be disposed on the first differential case portion. The reaction block can be configured to transfer a first side gear separation force onto the first differential case portion. 
         [0011]    According to additional features, the annular pocket can be defined by an outer circumferential wall, an inner circumferential wall and an end wall. The first differential case can further include an annular lip formed in part by the inner circumferential wall. The reaction block can be disposed on the annular lip. The reaction block can include a radial arm and a ledge. The ledge can rest against the annular lip of the reaction block. The radial arm can oppose the inner circumferential wall of the annular pocket of the first differential case. 
         [0012]    According to other features, the first side gear defines an annular channel that nestingly receives the reaction block therein. The first differential case can define a plurality of blind bores that receive planet gear shafts from a planetary gear set. The differential assembly can further include a first o-ring disposed between the piston and the outer circumferential wall of the annular pocket. A second o-ring can be disposed between the piston and the inner circumferential wall of the annular pocket. 
         [0013]    A differential gear mechanism constructed in accordance to another example of the present disclosure can include a differential casing having a first differential case portion that defines a first output shaft opening and a second differential case portion that defines a second output shaft opening. The first differential case portion can include an annular pocket formed thereon. The first differential case can further define a plurality of blind bores that receive planet gear shafts from a planetary gear set. A piston can be slidably disposed in the annular pocket and configured to actuate a clutch assembly. A first and a second side gear can be rotatably mounted within the differential casing. The first and second side gears can be co-axially aligned along an axis of rotation of the differential casing. The first side gear can define a first shaft opening configured to provide a first torque transmitting connection with a first output shaft received within the first output shaft opening. The second side gear can define a second shaft opening configured to provide a second torque transmitting connection with a second output shaft received within the second output shaft opening. A reaction block can be disposed on the first differential case portion. The reaction block can be configured to transfer a first side gear separation force onto the first differential case portion. 
         [0014]    According to other features, the reaction block can include a radial arm and a ledge. The ledge can rest against the annular lip of the reaction block. The radial arm can oppose the inner circumferential wall of the annular pocket of the first differential case. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0016]      FIG. 1  is schematic of an exemplary vehicle driveline incorporating a differential gear mechanism constructed in accordance to one example of the present disclosure; 
           [0017]      FIG. 2  is a front perspective view of a limited slip differential assembly constructed in accordance to one example of the present disclosure; 
           [0018]      FIG. 3  is a cross-sectional view of the limited slip differential assembly taken along lines  3 - 3  of  FIG. 2 ; 
           [0019]      FIG. 4  is a detailed sectional view of a first differential case, piston, reaction block and side gear of  FIG. 3 ; 
           [0020]      FIG. 5  is a front exploded perspective view of a portion of the differential case of  FIG. 2 ; and 
           [0021]      FIG. 6  is a rear exploded perspective view of a portion of the differential case shown in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    With initial reference to  FIG. 1 , an exemplary vehicle driveline is shown and generally identified with reference numeral  10 . The exemplary vehicle driveline  10  described herein is for a front wheel drive vehicle having a transversely mounted engine  12 , although other configurations can be utilized with the present disclosure. The engine  12  provides a rotary output to a transmission  14 . 
         [0023]    The driveline  10  can further include a transaxle  22  and a limited slip differential assembly  30  having a planetary gear assembly  16 , a clutch assembly  32  and a differential gear assembly  34 . The limited slip differential assembly  30  is received in a housing  36  and operates to drive a pair of axle shafts  40  and  42  that are connected to front drive wheels  44  and  48 , respectively. In general, the limited slip differential assembly  30  functions as a traditional open differential during normal operating conditions until an event occurs where a bias torque is required. When a loss in traction is detected or anticipated, the clutch assembly  32  can be selectively actuated in order to generate the optimum bias ratio for the situation. 
         [0024]    The transmission  14  can receive the rotary output from the engine  12  and provide a rotary input to the limited slip differential assembly  30 . Further, the transmission  14  can be operable to provide various gear ratios between the rotary output of the engine  12  and the rotary input of the limited slip differential assembly  30 . 
         [0025]    The planetary gear assembly  16  includes a ring gear  46 , a sun gear  20  and a plurality of planet gears  50  carried by a planet carrier  52 . The ring gear  46  is non-rotatably fixed to the housing  36 , and the sun gear  20  is meshingly engaged with the plurality of planet gears  50  carried by the planet carrier  52 . The planet gears  50  are meshed with the ring gear  46 . The planet carrier  52  is coupled for rotation with a differential case  54  of the differential gear assembly  34 . The planetary gear assembly  16  provides a gear ratio reduction from the sun gear  20  to the planetary carrier  52  and, therefore, to the differential case  54 . The sun gear  20  is rotatably coupled to the transmission  14  via a coupling device, such as a chain or belt, such that an output of the transmission  14  drivingly rotates the sun gear  20 , which translates rotational output from the transmission  14  into rotational input of the sun gear  20 . 
         [0026]    The differential gear assembly  34  includes a pair of side gears  60  and  62  that are mounted for rotation with the axle shafts  40  and  42  (and first and second drive wheels  44  and  48 ), respectively. The side gears  60  and  62  define first and second axle shaft openings  64  and  65  ( FIG. 3 ). A plurality of cross pins or pinion gear shafts  66  are fixedly mounted to the differential case  54  for rotation therewith. A corresponding plurality of pinion gears  70  are mounted for rotation with the pinion gear shafts  66  and are in meshing relationship with both of the side gears  60  and  62 . In an open configuration, described more fully below, the differential gear assembly  34  acts to allow the axle shafts  40  and  42  to rotate at different speeds. 
         [0027]    The clutch assembly  32  couples the planetary gear assembly  16  with the differential gear assembly  34 . The clutch assembly  32  includes a clutch pack  72  and a clutch actuator  73 . The clutch pack  72  includes a plurality of annular plates  74  interleaved between a plurality of annular friction disks  78 . The plurality of annular plates  74  can be coupled for rotation with one of the differential case  54  and the differential gear assembly  34 . The plurality of annular friction disks  78  can be coupled for rotation with the other one of the differential case  54  and the differential gear assembly  34 . In the illustrated embodiment, the plurality of annular plates  74  are coupled for rotation to the differential case  54  (e.g., splined to an inner diameter  76  of the differential case  54 ) and the plurality of annular friction disks  78  are coupled for rotation with the differential gear assembly  34  (e.g., splined to an outer diameter  80  of the side gear  60 ). It will be appreciated that the annular friction disks  78  may be supported for rotation by either of the side gears  60  or  62 , or both. 
         [0028]    The plurality of annular plates  74  and annular friction disks  78  are interleaved between one another and act to rotate past one another in substantially non-contacting relationship when the clutch assembly  32  is in its open position. However, it will be appreciated by those skilled in the art that the term “non-contacting” as used herein is relative and is not meant to necessarily indicate that the annular plates  74  and annular friction disks  78  have absolutely no contact when the clutch assembly  32  is in the open condition. The annular plates  74  and annular friction disks  78  are axially movable into frictional engagement relative to one another, thereby reducing relative rotation between the annular plates  74  and annular friction disks  78  when the clutch assembly  32  is in the closed or partially closed configurations. In this manner, when the clutch assembly  32  is in its closed position, the side gears  60  and  62 , as well as the axle shafts  40  and  42  and the drive wheels  44  and  48  rotate together. 
         [0029]    The clutch assembly  32  can operate in an open configuration to allow the side gears  60  and  62  to rotate independently from each other, e.g., at different speeds. The clutch assembly  32  can also operate in a closed or partially closed configuration where the side gears  60  and  62  rotate together or partially together (that is, not independently), e.g., at substantially the same speed. The clutch assembly  32  can, for example, be a hydraulic clutch assembly  32  that utilizes pressurized hydraulic fluid that can act on a piston  82  to selectively actuate the clutch pack  72  between the open, closed and partially closed configurations. 
         [0030]    With additional reference now to  FIGS. 2-6 , additional features of the differential gear assembly  34  will be described. The differential case  54  can include a first differential case portion  90  that defines a first output shaft opening  92  ( FIG. 3 ) and a second differential case portion  94  that defines a second output shaft opening  96  ( FIG. 2 ). The first and second differential case portions  90  and  94  can be coupled together by a plurality of fasteners  98 . In the example shown, the fasteners include hex bolts although other configurations are contemplated. As will become appreciated from the following discussion, the first differential case portion  90  can include define an integrally formed piston housing  100 . Further, the first differential case portion  90  can share a common wall  102  ( FIG. 3 ) between the planetary gear assembly  16  and the piston housing  100 . 
         [0031]    The first differential case portion  90  can define an annular pocket  110  ( FIG. 4 ) and a plurality of blind bores  114  ( FIG. 3 ). The annular pocket  110  can be defined by an outer circumferential wall  120 , an inner circumferential wall  122  and an end wall  124 . The end wall  124  can be integral to the common wall  102 . The first differential case  90  can further include an annular lip  128  formed in part by the inner circumferential wall  122 . The blind bores  114  can be receive planet gear shafts  130  that support the planet gears  50  of the planetary gear assembly  16 . 
         [0032]    A first o-ring  134  can disposed between the piston  82  and the outer circumferential wall  120  of the annular pocket  110 . In one example, the piston  82  can define an outer annular recess  136 . The first o-ring  134  can nest in the outer annular recess  136 . A second o-ring  140  can be disposed between the piston  82  and the inner circumferential wall  122  of the annular pocket  110 . In one example, the piston  82  can define an inner annular recess  142 . The second o-ring  140  can nest in the inner annular recess  142 . 
         [0033]    During operation of the clutch assembly  32 , the piston  82  can be caused to actuate toward and away (in a horizontal direction as viewed in  FIG. 3 ) from the clutch pack  72  in the annular pocket  110 . Actuation of the piston  82  can be caused by a predetermined amount of hydraulic pressure delivered to the clutch assembly  32  generating the optimum bias ratio for the situation to maintain the proper kinematic wheel speed difference as if both wheels were gripping predictably. In the example shown, actuation of the piston  82  toward an engaged position (rightward as viewed in  FIG. 3 ) causes the annular plates  74  and the annular friction disks  78  to become frictionally engaged thereby locking the differential gear assembly  34  such that the side gears  60  and  62  rotate at the same speed. 
         [0034]    A reaction block  150  can be disposed on the first differential case portion  190 . The reaction block  150  can be configured to transfer a separation force from the first side gear  60  onto the first differential case portion  90 . In this regard, the reaction block  150  and the first differential case portion  90  can provide structural support for maintaining an axial position of the side gear  60 . The reaction block  150  can be nestingly received in an annular channel  154  ( FIGS. 4 and 6 ) defined in the first side gear  60 . A washer  156  can be disposed in the annular channel  154  between the side gear  60  and the reaction block  150 . The reaction block  150  can generally include a conical body  160  that defines a plurality of bores  162  therethrough. The reaction block  150  can include a radial arm  170  ( FIG. 4 ) and a ledge  172 . The ledge  172  rests against the annular lip  128  of the first differential case portion  90 . The radial arm  170  opposes the inner circumferential wall  122  of the annular pocket  110 . 
         [0035]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.