Abstract:
An axle assembly that includes a differential casing, which is rotatable about an axis, a pair of side gears that are disposed within the differential casing, a spacer and a cross pin. The spacer is disposed between the side gears. The cross pin is fixed to the differential casing and extends through the spacer. The cross pin is employed to limit end play of the axle shafts in a direction toward one another. The aperture in the spacer that receives the cross pin is relatively larger than the cross pin so that the spacer can control end play of the side gears independently of the cross pin.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is a continuation of U.S. patent application Ser. No. 10/794,780 filed Mar. 5, 2004, now U.S. Pat. No. 7,022,041, entitled “Helical Gear Differential” the disclosure of which is hereby incorporated by reference in its entirety. 

   FIELD OF THE DISCLOSURE 
   The present disclosure relates to differentials for use in automotive drivelines and, more particularly, to a pinion pair arrangement for a four pinion pair, C-clip differential having independent control of side gear endplay and axle shaft endplay. 
   BACKGROUND OF THE DISCLOSURE 
   Differentials of the type used in automotive drivelines generally include a planetary gearset supported within a differential casing to facilitate relative rotation (i.e., speed differentiation) between a pair of output shafts. The planetary gearset typically includes helical side gears fixed to the end of the output shafts, which are meshed with paired sets of helical pinion gears. This type of differentiation is known as a parallel axis helical gear differential. In response to input torque applied to the differential case, the torque transmitted through meshed engagement of the side gears and pinion gears generates thrust forces. To accommodate these and other operating forces, the wall surface of the gear pockets and other thrust surfaces of the differential casing must provide adequate support. 
   In some differentials it is necessary to install C-shaped retainers, or C-clips for restraining and positioning the output shafts in the differentials. To install the C-clips it is necessary to gain access to the interior cavity of the differential casing through an access window arranged on the differential casing. 
   In general, it is desirable to allow the side gear loading to be spread out evenly around the periphery of the differential. One way to achieve even loading is to position the pinion pairs evenly around the periphery of the differential casing. However, because the access window is arranged on the outer periphery of the differential casing, there tends to be incompatibility issues with placement of the pinion pairs. 
   SUMMARY OF THE DISCLOSURE 
   In one form, the present disclosure provides an axle assembly for a vehicle that includes a differential casing, a pair of side gears, a pair of axle shafts, a spacer and a cross pin. The differential casing is rotatable about an axis and includes a first pin aperture. The side gears are disposed within the differential casing. Each axle shaft is coupled for rotation with one of the side gears. The spacer is disposed between the side gears and has a second pin aperture. The cross pin is received into the first and second pin apertures such that receipt of the cross pin into the first pin aperture fixedly but removably couples the cross pin to the differential casing. The size of the second pin aperture is greater than a corresponding size of the cross pin such that the spacer is moveable along the rotational axis of the differential casing relative to the cross pin. As such, the cross pin limits movement of the axle shafts in a direction toward one another and the spacer limits movement of the side gears toward one another independently of the cross pin. 
   In another form, the present disclosure provides a method that includes: providing a differential casing having a rotational axis; installing a pair of side gears within the differential casing; installing a pair of axle shafts to the side gears such that each axle shaft is coupled for rotation with one of the side gears; locating a spacer between the side gears; fixedly coupling a cross pin to the differential casing such that the cross pin is inserted through a pin aperture in the spacer; and moving the side gears and the spacer in a first direction along the rotational axis without moving the cross pin. 
   In yet another form, the present disclosure provides an axle assembly for a vehicle that includes a differential casing, a pair of side gears, a pair of axle shafts, a spacer and a cross pin. The differential casing is rotatable about an axis and includes a first pin aperture. The side gears are disposed within the differential casing. Each axle shaft is coupled for rotation with one of the side gears. The spacer is disposed between the side gears and includes a second pin aperture. The cross pin is received into the first and second pin apertures. Receipt of the cross pin into the first pin aperture fixedly but removably couples the cross pin to the differential casing. The size of the second pin aperture is greater than a corresponding size of the cross pin such that a void space is disposed between the spacer and the cross pin regardless of a position of the side gears axially along the rotational axis. 
   Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
       FIG. 1  is a schematic view of an exemplary motor vehicle into which a differential assembly constructed in accordance with the teachings of the present disclosure is incorporated; 
       FIG. 2   a  is a perspective view of the differential assembly of  FIG. 1 ; 
       FIG. 2   b  is a perspective view of the differential casing of  FIG. 1 ; 
       FIG. 3  is an exploded view of the differential assembly of  FIG. 1 ; 
       FIG. 4  is a sectional view of the differential assembly taken along line  4 — 4  of  FIG. 2   a;    
       FIG. 5  is a cross-sectional view of the differential assembly taken along line  5 — 5  of  FIG. 4 ; 
       FIG. 6  is a perspective view of the differential assembly of  FIG. 1  illustrating the cross pin assembly in an exploded condition; 
       FIG. 7  is a perspective view of the differential assembly of  FIG. 1  illustrating the cross pin assembly engaged to the cylindrical boss of the differential casing; 
       FIG. 8  is a perspective view of the differential assembly of  FIG. 1  illustrating the cross pin assembly in an installed condition; 
       FIG. 9  is an exploded view of a differential assembly according to other features; 
       FIG. 10  is an exploded view of a differential assembly according to other features; and 
       FIG. 11  is an exploded view of the differential assembly according to other features. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. The differential assembly according to the present teachings may be utilized with a wide variety of applications and is not intended to be specifically limited to the particular application recited herein. 
   With initial reference to  FIG. 1 , a drivetrain  10  for an exemplary motor vehicle may include an engine  12 , a transmission  14  having an output shaft  16 , and a propeller shaft  18  connecting the output shaft  16  to a pinion shaft  20  of a rear axle assembly  22 . The rear axle assembly  22  includes an axle housing  24 , a differential assembly  26  supported in the axle housing  24 , and a pair of axle shafts  28  and  30 , respectively, interconnected to a left and right rear wheel  32  and  34 , respectively. The pinion shaft  20  has a pinion shaft gear  36  fixed thereto which drives a ring gear  38  that may be fixed to a differential casing  40  of the differential assembly  26 . A gearset  42  supported within the differential casing  40  transfers rotary power from the casing  40  to a pair of output shafts  44  and  45  connected to the axle shafts  28  and  30 , respectively, and facilitates relative rotation (i.e., differentiation) therebetween. While the differential assembly  26  is shown in a rear-wheel drive application, the present invention is contemplated for use in differential assemblies installed in transaxles for use in front-wheel drive vehicles, and/or in transfer cases for use in four-wheel drive vehicles. 
   Turning now to  FIGS. 2   a – 4 , the differential assembly  26  will be described in further detail. The differential assembly  26  may be a parallel-axis helical-gear type differential and includes the differential casing  40 , which defines an internal chamber  48 . The differential casing  40  includes a main drum or body  46  and an end cap  50 , each of which having respective mating radial flanges  52  and  54 , respectively. The radial flanges  52  and  54  are secured together by a plurality of bolts (not shown) extending through aligned mounting bores  58 . As is known, a ring or bevel gear can be fixed to the radial flange  52  on the differential casing  40  to transfer rotary power (i.e., drive torque) thereto. The differential casing  40  defines a pair of axially aligned openings  60   a  and  60   b  in communication with the internal chamber  48 . The axially aligned openings  60   a  and  60   b  are adapted to receive the end segments of the pair of driving output shafts  44  and  45  ( FIG. 1 ), hereinafter referred to as axle shafts. 
   With specific reference to  FIGS. 3 and 4 , the differential assembly  26  includes the gearset  42  that is operable for transferring drive torque from the differential casing  40  to the output shafts  44  and  45  ( FIG. 1 ) in a manner that facilitates speed differential therebetween. Gearset  42  may be a helical-type and may be disposed within the internal chamber  48 . The gearset  42  includes a pair of side gears  68   a  and  68   b.  The side gears have internal splines  70   a  and  70   b  meshed with external splines, not specifically shown, on the corresponding output shafts  44  and  45  ( FIG. 1 ). In addition, the side gears  68   a  and  68   b  include axial hubs  78   a  and  78   b,  respectively, which are retained in corresponding annular sockets, formed in the main body  46  and the end cap  50  of the differential casing  40 , and annular chambers  82   a  and  82   b.  As will be described in greater detail below, a spacer  86  may be located between the side gears  68   a  and  68   b  for limiting the amount of axial endplay of the side gears  68   a  and  68   b  within the differential case  40 . A cross pin assembly  90  extends through a clearance passage  92  in the spacer  86  and controls endplay of the axle shafts  44  and  45  ( FIG. 1 ). 
   C-shaped retainers, or C-clips  94 , may be retained in the annular chambers  82   a  and  82   b  for preventing the axle shafts  44  and  45 , respectively, from becoming disengaged with the side gears  68   a  and  68   b.  The side gears  68   a  and  68   b  may be bounded at their outer ends by washers  96 . 
   The gearset  42  includes four sets of pinion pairs,  100   a  and  100   b,    102   a  and  102   b,    104   a  and  104   b  and  106   a  and  106   b,  respectively ( FIG. 3 ). For clarity the pinion pairs  100   a  and  100   b,    102   a  and  102   b,    104   a  and  104   b  and  106   a  and  106   b  are hereinafter referred to as a first, second, third and fourth pair of pinion gears  100 ,  102 ,  104  and  106 , respectively. Brake shoes  100   a ′– 106   b ′ cooperate with respective pinion gears  100 – 106 . 
   In  FIGS. 2   b  and  3 , the four sets of pinion pairs  100 – 106  are rotatably supported in complementary sets of pinion bores  110   a  and  110   b,    112   a  and  112   b,    114   a  and  114   b,  and  116   a  and  116   b.  The complementary sets of pinion bores  111   a  and  110   b,    112   a  and  112   b,    114   a  and  114   b,  and  116   a  and  116   b  are hereinafter referred to as a first, second, third and fourth pair of pinion bores  110 ,  112 ,  114 , and  116 , respectively. The pinion bores  110 – 116  are formed in raised hub segments  120  of the main body  46 . The pinion bores  110 – 116  are arranged in paired sets such that they communicate with each other and with the internal chamber  48 . In addition, the pinion bores  110 – 116  are aligned substantially parallel to the rotational axis A of the axle shafts  44  and  46  ( FIG. 1 ). A window opening  124  may be arranged on the differential casing  40  between the first and the fourth pair of pinion gears  100  and  106 . 
   With reference now to  FIG. 5 , the spacial relationship of the pinion pairs will be described. The four pinion bores  110 – 116 , and as a result, the four pinion pairs  100 – 106  ( FIG. 3 ), are radially spaced evenly around the differential casing  40  opposite the window opening  124 . More specifically, the first pair of pinion bores  110  are offset a radial distance α 1  from the second pair of pinion bores  112 . The second pair of pinion bores  112  are offset a radial distance α 2  from the third pair of pinion bores  114 . The third pair of pinion bores  114  are offset a radial distance α 3  from the fourth pair of pinion bores  116 . As illustrated, the respective α distances are taken from the centerline of respective first bores  110   a – 110   d.  The radial offsets between the pinion bores  110  and  112 ,  112  and  114 , and  114  and  116  may be approximately equivalent (e.g., α 1 =α 2 =α 3 ). In the example provided, α 1 , α 2  and α 3  are approximately 75 degrees. 
   With specific reference now to  FIGS. 2   b,    4  and  6 , the configuration of the window opening  124  and the cooperation of the cross pin assembly  90  will be described. The window opening  124  includes an access passage  126  surrounded by a cylindrical boss  128  that may be formed on an outer surface  130  of the differential casing  40 . The cylindrical boss  128  defines a counterbore  132  having an inner radial engaging surface  136 . The cylindrical boss  128  includes a pair of mounting passages  140  formed on raised flanges  142  for receiving a fastener  146  ( FIG. 8 ) therethrough. A ledge portion  150  extends at least partially about the window opening  124  inwardly of the cylindrical boss  128  on the differential casing  40 . 
   The cross pin assembly  90  generally includes a proximal head portion  154 , an intermediate shank portion  158  and a distal end portion  162 . The head portion  154  defines a body that may extend generally transverse to the longitudinal axis of the cross pin  90 . The head portion  154  may include a throughbore  164  for receiving the fastener  146 . The head portion  154  may include arcuate ends  168  that may be slidably disposed against the inner radial engaging surface  136  of the counterbore  132  during assembly. A bottom surface  170  of the head portion  154  locates against the ledge  150 . The distal end portion  162  of the cross pin assembly  90  locates into a bore  172  formed into incorporated on the differential casing  40 . 
   The cross pin assembly  90  may be unitarily formed or may comprise two or more components. In the example provided, the cross pin  90  is a two-piece assembly comprising the proximal head portion  154 , which may be pressed onto a discrete shank that defines both the intermediate shank portion  158  and the distal end portion  162 . It is appreciated that while the distal end portion  162  of the cross pin  90  is shown stepped down from the intermediate shank portion  158 , the cross pin may comprise a uniform outer diameter. For example, an alternate pinion gear arrangement may be employed with a differential assembly providing enough space to accommodate a cross pin defining a consistent outer diameter. 
   With reference to  FIGS. 4 and 7 , assembly of the cross pin assembly  90  into the differential casing  40  will now be described in greater detail. Once the C-clips  94  are properly located and the spacer  86  is located between the side gears  66   a  and  66   b,  the spacer passage  92  may be aligned opposite the window opening  124  on the differential casing  40 . The distal end  162  and the intermediate portion  158  of the cross pin assembly  90  are inserted through the window opening  124  and the spacer passage  92 . The distal end  162  of the cross pin assembly  90  may be located into the bore  172  on the differential case  40  opposite the window opening  124 . The bore  172  and the counterbore  132  pilot the cross pin assembly  90  during installation. The proximal head portion  154  may be inserted in an orientation substantially transverse to the axis of the differential casing  40 . In this way, the head portion  154  of the cross pin assembly  90  will not interfere with the adjacent ring gear  38  ( FIG. 1 ) during installation. 
   As the distal end  162  of the cross pin assembly  90  locates into the bore  172 , the bottom surface  170  of the head portion  154  engages the ledge  150  between the counterbore  132  and the window opening  124 . Similarly, the arcuate ends  168  of the proximal head  154  engage the inner radial engaging surface  136  of the counterbore  132 . The proximal head portion  154  may then be rotated from the position shown in  FIG. 7  into a substantially parallel orientation with the axis A of the differential  26  as illustrated in  FIG. 8  until the throughbore  164  aligns with the mounting passages  140  of the raised flanges  142  on the cylindrical boss  128 . During rotation of the proximal head portion  154 , the inner radial engaging surface  136  pilots the arcuate ends  168  of the proximal head portion  154 . Concurrently, the ledge  150  maintains the cross pin assembly  90  at the proper depth and assures that the throughbore  164  will be properly aligned with the mounting passages  140  of the raised flanges  142  on the cylindrical boss  128 . 
   With the throughbore  164  and the mounting passages  140  aligned to one another, the fastener  146  may be inserted and secured. With the cross pin assembly  90  thus installed, relative movement between the cross pin assembly  90  and the differential casing  40  is essentially inhibited. As a result, the endplay of the axle shafts  44  and  46  ( FIG. 1 ) may be controlled within desirable tolerances as a function of the diameter of the intermediate portion  158  of the cross pin  90 . The spacer  86  is disposed between the sidegears  68   a  and  68   b  and controls axial endplay of the sidegears  68   a  and  68   b  to keep the differential  26  from binding. The cross pin  90  does not touch the spacer  86  in an assembled condition. The passage  92  in the spacer  86  defines a greater diameter than the diameter of the cross pin  90 . In this way, two distinct components are used to control the side gear endplay (namely, the spacer  86 ), and the axle shaft endplay (namely, the cross pin  90 ). Such an arrangement allows for a desired amount of side gear endplay without affecting the axle shaft endplay. 
   The mass of the differential assembly  26  may be distributed to provide rotational balance. Specifically, the mass of the cylindrical boss  128  and the cross pin head  154  cooperate with the mass of the differential casing  40  around the pinion bores  110 – 116  and the mass of the pinion gears  100 – 106  to provide a rotationally balanced differential assembly  26 . Stated another way, the mass of the several components of the differential assembly  26  are distributed about the rotational axis A so as to minimize or eliminate imbalance when the differential assembly  26  is rotated about the rotational axis A. It is appreciated that a counter weight may additionally, or alternatively be incorporated onto the differential casing  40  or the end cap  50  of the differential assembly  26 . 
   The fastener  146  may be configured the same as an open differential such that the same axle assembly lines may be ran with both open differentials and helical gear differentials without changing tooling or torque wrench settings. 
   Turning now to  FIG. 9 , a differential assembly  226  according to other features is shown. The differential assembly  226  incorporates like components as the differential assembly  26  and are identified with a 200 prefix. The differential assembly  226  includes a cross pin  290  having an intermediate shank portion  258  and a distal end portion  262 . The cross pin  290  may be adapted to be retained in the differential case  240  by a retaining disk  234 . Specifically, the proximal end of the cross pin  290  may be adapted to recess into a counterbore  238  formed on an inboard surface of the retaining disk  234 . A retaining ring  244  may be adapted to seat into a radial lip  248  arranged on the counterbore  232  in an assembled position. 
   With reference now to  FIG. 10 , a differential assembly  326  according to additional features is shown. The differential assembly  326  incorporates like components as the differential assembly  26  and are identified with a 300 prefix. The differential assembly  326  includes a cross pin  390  having an intermediate shank portion  358  and a distal end portion  362 . The cross pin  390  may be adapted to be retained in the differential case  340  by an L-plate  334  and a fastener  341 . Specifically, a proximal end of the cross pin  390  may be adapted to pass through an opening  338  arranged on the L-plate  334 . In this way, the L-plate cooperates with the cross pin  390  to maintain the cross pin  390  in a substantially perpendicular orientation with axis A. The fastener  341  may be adapted to be secured through passages  348  incorporated in flange portions  332  and a passage  335  arranged in the L-plate  334 . As a result, in an installed position, the fastener  341  bounds the proximal end of the cross pin  290  and maintains the cross pin  290  in an installed position. 
   With reference now to  FIG. 11 , a differential assembly  426  according to additional features is shown. The differential assembly  426  incorporates like components as the differential assembly  26  and are identified with a 400 prefix. The differential assembly  426  includes a cross pin  490  having an intermediate shank portion  458  and a distal end portion  462 . The cross pin  490  may be adapted to be retained in the differential casing  440  by a fastener  441 . Specifically, the fastener  441  may be adapted to be secured through passages  448  incorporated in flange portions  432  and a passage  435  arranged in the cross pin  490 . 
   An access passage  426  may be incorporated in the differential casing  440  and defines an access for installing C-clips  92  ( FIG. 3 ). A spacer  486  according to additional features includes a passage  492  for accepting the cross pin  490  therethrough in an assembled position. The spacer  486  may be adapted to be installed into the differential casing  440  axially and be positioned between side gears as described herein. 
   While the disclosure has been described in the specification and illustrated in the drawings with reference to various embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure as defined in the claims. Furthermore, the mixing and matching of features, elements and/or functions between various embodiments is expressly contemplated herein so that one of ordinary skill in the art would appreciate from this disclosure that features, elements and/or functions of one embodiment may be incorporated into another embodiment as appropriate, unless described otherwise, above. Moreover, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this disclosure, but that the disclosure will include any embodiments falling within the foregoing description and the appended claims.