Patent Publication Number: US-2015080166-A1

Title: Locking differential

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 13/829,927 filed Mar. 14, 2013, entitled LOCKING DIFFERENTIAL which claims the benefit under Title 35, U.S.C. Section 119(e) of U.S. Provisional Patent Application Ser. No. 61/719,161, filed Oct. 26, 2012 entitled LOCKING DIFFERENTIAL, the entire disclosures of which are hereby expressly incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a differential, and, more particularly, to a locking differential in which each side gear is independently locked to the differential casing so that torque is not transmitted through the pinion gears when the differential is locked. 
     2. Description of the Related Art 
     Differential gear sets are employed to allow a pair of driven wheels connected to aligned axle half shafts to be driven at differential speeds. For example, when a vehicle turns the outside wheel must rotate faster than the inside wheel. To allow for such cornering while maintaining tires in consistent rolling contact with the ground, the differential gear set allows one of the output half shafts to rotate at a different speed as compared to the other output half shaft. 
     In some circumstances, it can be desirable to lock the differential such that two driven half shafts do not allow for differential rotational speeds of their wheel. For example, if the vehicle loses sure footing such that one of the two wheels receives little resistance to its rotation while the other wheel has normal or high resistance, nearly all rotational input to the differential will be transferred to the low-traction wheel, causing it to spin freely over the low-traction surface while the high-traction wheel receives no rotational input. This allocation of rotational input to the low-traction wheel can prevent the vehicle from moving in response to torque input to the differential. However, if the differential is locked, the wheels are constrained to rotate at the same speed and the higher-traction wheel can use its torque to move the vehicle. 
     Existing locking differentials utilize various structures to lock one of the side gears to the differential casing. With one of the side gears locked to the differential casing, torque input to the differential casing is transferred via the locked side gear to the corresponding axle half shaft. Further, because one of the side gears is locked to the differential casing, rotation of the pinion gears is disallowed so that torque transmitted to the differential casing is further transmitted through the pinion gears to the non-locked side gear so that both side gears (and the associated axle half shafts) rotate at the same speed as the differential casing. 
     Existing “limited slip” type differentials utilize clutch arrangements in engagement with one or both of the side gears and the differential casing. The clutch(es) can be actuated to provide a high frictional resistance to rotation of the side gear(s) relative to the differential case, thereby transferring some torque to a higher-traction wheel when the clutches are actuated. U.S. Pat. No. 5,531,653 shows one such limited slip differential design. 
     Yet another differential design, such as the Detroit Locker® differentials available from Eaton Corporation of Cleveland, Ohio utilize multi-piece differential casing structures that normally transmit torque to both driven wheels but allow differential rotation when a threshold differential torque is applied to the wheels. U.S. Pat. No. 6,681,654 shows a locked differential in which axle couplers are drivingly engaged with axle drivers by a plurality of mutually engaging teeth formed on respective faces of the couplers and drivers. A camming interrelationship between the two drivers operates to pull the driver inward to clear the driving teeth from the axle coupler when differential rotation occurs. 
     SUMMARY 
     The present disclosure provides a selectively locked differential having a locked configuration in which both side gears are independently locked to the differential casing so that torque is not transmitted through the pinion gears. The locking of the side gears is accomplished by generally cylindrical, ring-shaped structures with castellations on one axial end surface of each structure. These castellations selectively interfit with rotatably fixed castellations of secondary structures fixed to the differential casing, such that the ring-shaped structures define a mechanically interconnected, zero-slip arrangement with respect to the rotationally fixed secondary structures when the differential is in the locked configuration. 
     In one form thereof, the present disclosure provides a differential comprising: a differential casing defining a longitudinal axis, a first set of rotatably fixed castellations and a second set of rotatably fixed castellations affixed to the differential casing; a first side gear and a second side gear each rotatable with respect to the differential casing about the longitudinal axis, the first side gear and the second side gear each adapted to be rotatably fixed to a half shaft; at least one pinion gear intermeshingly engaged with the first side gear and the second side gear, the pinion gear rotatable about a pinion gear axis when the first side gear rotates at a rotational speed different from the second side gear; a first clutch plate rotatably fixed to the first side gear and having an end surface with a first set of rotatable castellations formed thereon, the first clutch plate axially moveable within the differential casing between an engaged position and a disengaged position, the first set of rotatable castellations interfitted with the first set of rotatably fixed castellations of the differential casing when the first clutch plate is in the engaged position, the first set of rotatable castellations spaced from the first set of rotatably fixed castellations of the differential casing when the first clutch plate is in the disengaged position, whereby the first side gear is selectively rotatably fixed to the differential casing via the first clutch plate; and a second clutch plate rotatably fixed to the second side gear and having an end surface with a second set of rotatable castellations formed thereon, the second clutch plate axially moveable within the differential casing between an engaged position and a disengaged position, the second set of rotatable castellations interfitted with the second set of rotatably fixed castellations of the differential casing when the second clutch plate is in the engaged position, the second set of rotatable castellations spaced from the second set of rotatably fixed castellations of the differential casing when the second clutch plate is in the disengaged position, whereby the second side gear is selectively rotatably fixed to the differential casing via the second clutch plate, whereby the differential has a locked condition in which each of the side gears is independently locked to the differential casing and torque is not transmitted through the pinion gear. 
     In another form thereof, the present disclosure provides a differential comprising: a differential casing having a hollow cavity formed therein, the hollow cavity defining a longitudinal axis; a first side gear and a second side gear each rotatable with respect to the differential casing about the longitudinal axis, the first side gear and the second side gear each adapted to be rotatably fixed to a half shaft; a pinion housing rotatably affixed to the differential casing and having an end surface with a first set of rotatably fixed castellations formed thereon; at least one pinion gear intermeshingly engaged with the first side gear and the second side gear, the pinion gear rotatably mounted to the pinion housing; a differential end plate rotatably fixed to the differential casing, the differential end plate having an end surface with a second set of rotatably fixed castellations formed thereon; a first clutch plate rotatably fixed to the first side gear and having an end surface with a first set of rotatable castellations formed thereon, the first clutch plate axially moveable along a first direction from a disengaged position in which the first set of rotatable castellations are spaced from the first set of rotatably fixed castellations of the pinion housing, toward an engaged position in which the first set of rotatable castellations are intermeshingly engaged with the first set of rotatably fixed castellations; and a second clutch plate rotatably fixed to the second side gear and having an end surface with a second set of rotatable castellations formed thereon, the second clutch plate axially moveable along the first direction from a disengaged position in which the second set of rotatable castellations are spaced from the second set of rotatably fixed castellations of the differential end plate, toward an engaged position in which the second set of rotatable castellations are intermeshingly engaged with the second set of rotatably fixed castellations. 
     In yet another form thereof, the present disclosure provides a differential comprising: a differential casing having a hollow cavity formed therein, the hollow cavity defining a longitudinal axis, a first set of rotatably fixed castellations and a second set of rotatably fixed castellations affixed to the differential casing within the hollow cavity; a first side gear and a second side gear each disposed in the hollow cavity and rotatable with respect to the differential casing about the longitudinal axis, the first side gear and the second side gear each adapted to be rotatably fixed to a half shaft; at least one pinion gear disposed in the hollow cavity and intermeshingly engaged with the first side gear and the second side gear; a first clutch plate disposed in the hollow cavity and rotatably fixed to the first side gear and having an end surface with a first set of rotatable castellations formed thereon, the first clutch plate axially moveable from a disengaged position in which the first set of rotatable castellations are spaced from the first set of rotatably fixed castellations, toward an engaged position in which the first set of rotatable castellations are intermeshingly engaged with the first set of rotatably fixed castellations; a second clutch plate disposed in the hollow cavity and rotatably fixed to the second side gear and having an end surface with a second set of rotatable castellations formed thereon, the second clutch plate axially moveable from a disengaged position in which the second set of rotatable castellations are spaced from the second set of rotatably fixed castellations, toward an engaged position in which the second set of rotatable castellations are intermeshingly engaged with the second set of rotatably fixed castellations; and an actuator having at least one actuation pin actuatable to a locked configuration in which the actuation pin advances into the hollow cavity of the differential casing to simultaneously urges the first clutch plate and the second clutch plate toward their respective engaged positions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features of the disclosure, and the manner of attaining them, will become more apparent and will be better understood by reference to the following description of embodiments of the disclosure taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective, partial cutaway view of a locking differential in accordance with the present disclosure; 
         FIG. 2  is an exploded, perspective view of the locking differential shown in  FIG. 1 ; 
         FIG. 3  is an elevation, cross-section view of the locking differential shown in  FIG. 1 , in which the differential is in an unlocked configuration; 
         FIG. 4  is an elevation, partial cutaway view of the locking differential shown in  FIG. 1 , in which the differential is in the unlocked configuration; 
         FIG. 5  is a perspective view of selected components of the locking differential shown in  FIG. 1 , in which the differential is shown in the unlocked configuration; 
         FIG. 6  is a perspective, partial cutaway view of the locking differential components shown in  FIG. 5 , in which the differential has been toggled to a locked configuration; 
         FIG. 7  is a perspective view of a pinion gear housing made in accordance with the present disclosure, with pinion gears mounted thereto; 
         FIG. 8  is a side elevation view of a portion of the locking differential of  FIG. 1 , illustrating detail of castellations formed on structures within the locking differential; 
         FIG. 9  is a perspective, partially exploded view of selected components of an alternative locking differential in accordance with the present disclosure, illustrating an unlocked configuration; and 
         FIG. 10  is a perspective view of the selected components of the locking differential shown in  FIG. 9 , illustrating a locked configuration. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the disclosure and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION 
     The present disclosure provides a locking differential, such locking differential  10  shown in  FIG. 1 , which includes a binary locking feature such that the differential is capable of being selectively configured into one of an unlocked or a locked condition to allow or prevent differential rotation between two axle half shafts. In such a binary configuration, differential  10  does not utilize a “limited slip” configuration in which the axle half shafts are partially locked, that is, are not allowed to freely rotate with respect to one another but are also not entirely prevented from relative rotation. 
     The binary locking feature of differential  10  is provided by a pair of clutch plates  30 ,  34  which are axially moveable within differential casing  12  to selectively rotatably lock a pair of side gears  14 ,  16  ( FIG. 2 ) with respect to differential casing  12 . As described in detail below, this rotatable locking of side gears  14 ,  16  is accomplished using first and second sets of rotatable castellations  50 ,  54  which selectively engage corresponding first and second sets of rotatably fixed castellations  52 ,  56  ( FIG. 2 ). Clutch plates  30 ,  34  each move in a common axial direction along longitudinal axis A when toggling between their respective engaged to the disengaged positions, thereby facilitating the use of a single actuator  22  to rotatably fix or decouple side gears  14 ,  16  with respect to differential casing  12 . 
     As used herein, two parts are considered to be “rotatably fixed” with respect to one another if those two parts are not rotatable with respect to one another about their respective axes of rotation. Thus, for example, left side gear  14  is considered to be rotatably fixed to left axle half shaft  40  because left side gear  14  includes splines  65  formed on the inner bore  64  thereof which matingly engage splines  60  formed on left axle half shaft  40 , thereby preventing rotation of side gear  14  relative to half shaft  40 . Similarly, a single part is considered to be “rotatably fixed” if that part is not rotatable within the relevant frame of reference (i.e., with respect to the other parts referred to in that frame of reference). Thus, for example, castellations  56  formed on differential end plate  38  are considered “rotatably fixed” in the context of locking differential  10  because end plate  38  does not rotate with respect to the other components of differential  10  (as described in further detail below), even though the entire locking differential  10 , including end plate  38 , rotates when power is applied to drive shaft  44  (as also described below). 
     Conversely, for purposes of the present disclosure, a first part that is “rotatably mounted” to a second part is considered to be rotatable with respect to such second part. Thus, for example, clutch plates  30 ,  34  are rotatably mounted to differential casing  12  because clutch plates  30 ,  34  are able to rotate within hollow cavity  36  defined by casing  12  when clutch plates  30 ,  34  are disengaged (as further described below). Similarly, a single part is considered to be “rotatable” if that part is able to rotate within the relevant frame of reference, such as rotatable castellations  50 ,  54  formed on clutch plates  30 ,  34 , in the context of the parts making up locking differential  10 . 
     For purposes of the present disclosure, various structures of locking differential  10  may be said to define axial “end surfaces,” which are surfaces at an axial end of the structure with respect to longitudinal axis A. Except as otherwise specified herein, the exemplary axial end surfaces shown in the figures and described further below define one or more surface planes which are substantially perpendicular to longitudinal axis A. Thus, for example, end surface  68  of differential casing  12  ( FIG. 2 ) is an annular, substantially planar surface located at an axial end of casing  12 , and defines a plane that is substantially perpendicular to longitudinal axis A. Similarly, mating end surface  70  of differential end plate  38 , which mates with end surface  68  of casing  12  upon assembly of differential  10 , is also disposed at an axial end of differential end plate  38  and defines a plane that is substantially normal to longitudinal axis A. 
     Referring now to  FIG. 1 , locking differential  10  is shown in the context of a power train system, such as a vehicle differential used to transmit power from the engine of the vehicle to driven wheels of the vehicle. For example, drive shaft  44  may be operably connected to a vehicle power source, such as an internal combustion engine or electric motor. Power is transmitted from the engine to drive shaft  44 , which includes drive gear  46  at a terminal end thereof in splined engagement with ring gear  48 . Ring gear  48 , in turn, is affixed to differential casing  12  by a plurality of fasteners  58 , which pass through apertures  72 ,  74  ( FIG. 2 ) formed in differential casing  12  and differential end plate  38 , respectively, and thread into threaded bores formed in the non-splined side of ring gear  48 . Locking differential  10  may be covered by differential housing  96 , which contains lubricants for the various parts of differential  10  and protects the gears and bearing surfaces from outside contamination. 
     As ring gear  48  rotates, torque is transferred to differential casing  12 , thereby causing rotation of differential casing  12  and associated components rotatably fixed thereto, including pinion housing  20 , differential end plate  38 , and actuator  22 . More particularly, actuator  22  is rotatably fixed to differential casing  12  by actuator pins  26  received within actuation apertures  28 , as best shown in  FIG. 2 . Pinion housing  20  is rotatably fixed to differential casing  12  via pinion gear axle shafts  76   a ,  76   b  ( FIGS. 1 and 7 ), which pass through the side wall of the substantially cylindrical pinion gear housing  20  and into the adjacent side wall of differential casing  12  as shown in  FIG. 1 . Differential end plate  38  is fixed to differential casing  12  by fasteners  58 , as noted above. 
     Transfer of torque from differential casing  12  and the other components rotatably fixed thereto and left and right axle half shafts  40 ,  42  may be accomplished in one of two ways, depending on whether locking differential  10  is in the locked or unlocked configuration. As further described below, pinion gears  18  participate in the transfer of torque from casing  12  to side gears  14  and  16  in the unlocked configuration. In the locked configuration, on the other hand, torque is transferred through pinion housing  20  and clutch plates  30 ,  34  while pinion gears  18  are bypassed. 
     FIGS.  1  and  3 - 5  all illustrate locking differential  10  in the unlocked configuration. In this configuration, a first set of rotatable castellations  50  formed on end surface  31  of clutch plate  30  are spaced from a corresponding set of rotatably fixed castellations  52  formed on end surface  21  of pinion housing  20 . In an exemplary embodiment, the spacing between castellations  50  and  52  is at least 0.025 inches to ensure that no interaction therebetween will occur during operation of differential  10 . Similarly, a second set of rotatable castellations  54  formed on end surface  35  of clutch plate  34  are spaced from a corresponding second set of rotatably fixed castellations  56  formed on end surface  39  of differential end plate  38  near mating surface  70 . 
     In the above-described spaced, non-interfitting relationship between castellations  50 ,  52  and  54 ,  56 , clutch plates  30  and  34  are free to rotate with respect to pinion housing  20  and differential end plate  38 , respectively (and are therefore also rotatable with respect to differential casing  12 ). However, pinion gears  18  include respective pinion gear splines  78  which are intermeshingly engaged with correspondingly formed side gear splines  80  on each of side gears  14  and  16 , as best shown in  FIG. 3 , preventing free rotation of side gears  14 ,  16  without also rotating pinion gears  18 . Meanwhile, side gears  14 ,  16  include splines  65 ,  67  formed in bores  64 ,  66 , respectively, which intermeshingly engage with axle splines  60 ,  62  of half shafts  40 ,  42  respectively ( FIG. 2 ). 
     Thus, as differential casing  12  rotates under power from drive shaft  44 , pinion gears  18  circumnavigate longitudinal axis A as pinion housing  20  rotates together with casing  12 . In the absence of any differential rotation of left and right axle half shafts  40 ,  42 , such as may arise from different levels of traction available to vehicle wheels mounted at respective ends of half shafts  40 ,  42 , pinion gears  18  transfer torque to side gears  14 ,  16  via splines  78 ,  80  and the circumnavigation of pinion gears  18  also rotates each side gear  14 ,  16  about longitudinal axis A. The splined engagement of side gears  14 ,  16  with half shafts  40 ,  42 , in turn, drives the wheels and moves the vehicle forward in a straight line. During this straight line vehicle movement, pinion gears  18  continue to circumnavigate longitudinal axis A but do not rotate about their respective pinion axes A P1 , A P2  ( FIG. 7 ). 
     However, in some instances left and right axle half shafts  40 ,  42  are urged to rotate at different speeds. For example, one wheel may lose traction and spin faster than the other wheel, or the vehicle may corner causing the outside wheels to rotate faster than the inside wheels. During such differential rotation, one of side gears  14 ,  16  rotates with respect to the other, causing pinion gears  18  to rotate about their respective pinion gear axes A P1 , A P2 . This rotation of pinion gears  18  facilitates differential rotation of side gears  14 ,  16  while maintaining rolling contact of the wheels mounted to half shafts  40 ,  42 . This differential rotation is allowed because side gears  14 ,  16  are free to rotate with respect to differential casing  12  and the other associated components rotationally fixed thereto, but disallowed when side gears  14 ,  16  become rotationally fixed to casing  12  as further described below. 
     When left side gear  14  rotates with respect to differential casing  12 , left clutch plate  34  also experiences rotation because left clutch plate  34  is rotationally fixed to left side gear  14 . More particularly, referring to  FIG. 2 , left side gear  14  includes outer surface splines  82  which are intermeshingly engaged with inner surface splines  86  formed along the inner bore of left clutch plate  34 . Similarly, right side gear  16  includes outer surface splines  84  which rotatably fix side gear  16  to inner surface splines  88  of right clutch plate  30 , such that right clutch plate  30  rotates relative to differential casing  12  when right side gear  16  so rotates. 
       FIG. 6  illustrates the locked configuration of locking differential  10 . In the locked configuration, right clutch plate  30  is urged to move along longitudinal axis A by forces F, which may be provided by actuator  22  as further described below. When so urged, clutch plate  30  advances along longitudinal axis A toward differential end plate  38 . In the engaged position, the first set of rotatable castellations  50  formed on the illustrated axial end surface  31  of clutch plate  30  interfit with the first set of rotatably fixed castellations  52  formed on the adjacent end surface  21  of pinion housing  20 , such that rotatable castellations  50  are received between rotatably fixed castellations  52 , and vice versa. When so interfitted, relative rotation between pinion housing  20  and clutch plate  30  is completely prevented, such that right side gear  16  is not allowed to rotate relative to differential casing  12  and the other rotatably fixed structures of differential  10 , including pinion housing  20  and differential end plate  38 . 
     The axial movement of right clutch plate  30  causes a corresponding axial movement of left clutch plate  34  in the same direction, i.e., toward differential end plate  38 . This corresponding axial movement is effected by the depression of lock pins  32  by castellations  50  of right clutch plate  30 , as best illustrated by a comparison between  FIGS. 5 and 6 . As illustrated in  FIG. 5 , lock pin  32  protrudes outwardly from axial end surface  21  of pinion housing  20 , and is disposed between a neighboring pair of rotatably fixed castellations  52 . When one of rotatable castellations  50  is received within the space occupied by lock pin  32 , the axial movement of castellation  50  into this space causes castellation  52  to advance toward end surface  21  thereby depressing lock pin  32 . As shown in  FIG. 6 , this depression pushes the opposite axial end of lock pine  32  outwardly, causing lock pin  32  to abut and urge clutch plate  34  toward differential end plate  38 . As clutch plate  34  moves axially away from pinion housing  20 , the second set of rotatable castellations  54  interfit with the second set of rotatably fixed castellations  56  formed on differential end plate  38 . This interfitting of castellations  54 ,  56  rotatably fixes left clutch plate  34  to differential end plate  38 , thereby entirely preventing relative rotation of left clutch plate  34  and left side gear  14  with respect to differential casing  12  and associated rotatably fixed structures. 
     Thus, when forces F are applied to right and left clutch plates  30 ,  34 , locking differential  10  is toggled from a disengaged configuration to an engaged configuration, in which relative rotation between left and right side gears  14 ,  16  is completely prevented. This disallowance of differential rotation further dictates that left and right axle half shafts  40 ,  42  must rotate at the same speed, thereby ensuring that torque is applied to both wheels driven by locking differential  10  equally. This arrangement has benefits in certain applications, such as off road applications or other instances where reduced traction is experienced by one or both of the driven wheels. 
       FIG. 8  illustrates detail of the interfitting geometries of rotatable castellations  50 ,  54  of clutch plates  30 ,  34  respectively and rotatably fixed castellations  52 ,  56  of pinion housing  20  and end plate  38 , respectively. Rotatable castellations  50  and the interfitting fixed castellations  52  each define a common castellation depth D 1 , which is measured along longitudinal axis A. Castellations  50 ,  52  also define a common draft angle Θ, which is the angle between respective lateral walls of castellations  50 ,  52  and longitudinal axis A. When castellations  50 ,  52  are interfitted with one another (as shown in  FIG. 6 ), the respective lateral walls of castellations  50 ,  52  bear against one another and present a physical barrier to relative rotation between clutch plate  30  and pinion housing  20 . Similarly, rotatable castellations  54  and the interfitting fixed castellations  56  each define a common castellation depth D 2 , and a common draft angle α to provide a physical barrier to rotation between clutch plate  34  and end plate  38 . Depths D 1  and D 2  and angles Θ, α may be the same or different, depending on what is required or desired for a particular application. 
     In an exemplary embodiment, depths D 1  and D 2  are between 0.075 inches and 0.225 inches, such as 0.125 inches. Angles Θ, α may be between −1 degrees (i.e., oppositely arranged from the illustrated angle and having a nominal value of 1 degree) and 5 degrees, such as 1 degree. Where the intermeshing gearing components of locking differential  10  are made of steel and actuator  22  provides a total force F of about 100 lb, locking differential can transmit up to 6,000 ft-lbs of torque to half shafts  40 ,  42 . 
     With right clutch plate  30  rotatably fixed to pinion housing  20 , and left clutch plate  34  rotatably fixed to differential end plate  38 , torque is transmitted from drive shaft  44  ( FIG. 1 ) to side gears  14  and  16  via differential casing  12 , pinion housing  20 , differential end plate  38  and right and left clutch plate  30  and  34 , respectively. Thus, unlike in the unlocked configuration described above, pinion gears  18  do not participate in the transfer of torque from drive shaft  44  to side gears  14  and  16  when locking differential  10  is in the locked configuration. This protects pinion gears  18  from wear or damage when differential  10  is locked, and provides more efficient and effective mechanisms for torque transfer through differential  10  in the locked configuration. 
     Moreover, larger and more chaotic transfers of torque are increasingly likely when differential  10  is in the locked configuration because uneven traction may be available to the wheels. As noted above, pinion gear splines  78  and side gear splines  80  are responsible for transferring torque from drive shaft  44  to axle half shafts  40 ,  42  during normal operation of a vehicle on dry pavement or other high traction surfaces. Thus, splines  78  and  80  experience normal wear during “normal driving,” e.g. operation of the vehicle on roadways or other improved surfaces. On the other hand, locking differential  10  is placed into the locked configuration when reduced or uneven traction is available to the vehicle wheels, such as in off-road applications. In these instances, pinion gear splines  78  and side gears splines  80  are relieved from the potentially heavy duty associated with torque transfer in off road driving, and castellations  50 ,  52  and  54 ,  56  assume this duty. 
     As best shown in  FIG. 3 , castellations  50 ,  52 ,  54 ,  56  are positioned radially outwardly of splines  78 ,  80  with respect to longitudinal axis A thereby increasing the distance between longitudinal axis A and the torque transferring structure, thereby increasing the lever arm available, reducing the reaction torque felt by clutch plates  30 ,  34  and enhancing the ability to transfer high amounts of torque when differential  10  is in the locked configuration. In addition, the associated torque-transferring parts of locking differential  10  utilized in the locked configuration, i.e., pinion housing  20 , clutch plates  30 ,  34  and differential end plate  38 , are generally cylindrically shaped structures in which torque transfer happens through the cylindrical wall of the structure. As a skilled artisan will recognize, cylinders are well suited to transfer large amounts of torque, thereby rendering these structures of locking differential  10  ideally suited to the heavy duty associated with the locked configuration. 
     In the exemplary embodiment shown in  FIG. 2 , actuator  22  provides the motive force for toggling locking differential  10  from the unlocked configuration to the locked configuration. Actuator  22  includes actuator pins  26  affixed to lock plate  24 , which is axially displaceable along longitudinal axis A with respect to actuator body  90 . In an exemplary embodiment, actuator body  90  is an electromagnetic coil which can be energized to urge lock plate  24  and actuator pins  26  axially away from actuator body  90 , and de-energized or oppositely energized to draw lock plate  24  back toward actuator body  90 . 
     Pins  26  are received into hollow cavity  36  of differential casing  12  via actuation apertures  28 , as best shown in  FIGS. 2 and 3 . Upon actuation, a distal axial end of pins  26  comes into abutting engagement with the end surface of right clutch plate  30  opposite castellations  50 , thereby imparting force F ( FIG. 6 ) upon right clutch plate  30  as described above. Biasing element  33  is disposed between on right clutch plate  30  and right side gear  16 , such that biasing element  33  urge clutch plate  30  out of engagement with pinion housing  20  when pins  26  are withdrawn. Similarly, another biasing element  33  may be disposed between left clutch plate  34  and differential end plate  38 , such that the expansion biasing force withdraws rotatable castellations  54  out of engagement with rotatably fixed castellations  56  when lock pins  32  are not being pushed axially outwardly from pinion housing  20  by castellations  50  of right clutch plate  30 . In an exemplary embodiment illustrated in  FIG. 2 , biasing elements  33  are resiliently deformable wave-type springs sized to be received upon respective outer cylindrical surfaces of side gears  14 ,  16  upon assembly, as illustrated. 
     The particular arrangement of castellations  50 ,  52 ,  54 , and  56  facilitate the actuation of both right and left clutch plates  30 ,  34  along a common axial direction, e.g., toward differential end plate  38 . In particular, rotatably fixed castellations  52  and  56  of pinion housing  20  and differential end plate  38 , respectively, each extend axially away from their respective end surfaces  21 ,  39  toward actuator  22 . Conversely, rotatable castellations  50 ,  54  of right and left clutch plates  30 ,  34 , respectively, each extend axially away from their respective end surfaces  31 ,  35  and away from actuator  22 . Thus, a single actuator  22  pushing actuator pins  26  toward rotatably fixed castellations  52  and  56 , in cooperation with lock pins  32  which transmit axial motion of right clutch plate  30  to left clutch plate  34  as described above, operates to interfit castellations  50  with castellations  52  simultaneously with the interfitting of castellations  54  and castellations  56 . In this way, both left and right side gear  14  and  16  are rotatably fixed to differential casing  12  by actuation of a single actuator  22 . 
     In the illustrated embodiment of  FIG. 2 , actuator  22  is mounted upon protrusion  94 , which is a monolithically formed feature of differential casing  12 . Gasket  92  may also be received upon protrusion  94  to prevent ingress of fluid or other contaminants from infiltrating hollow cavity  36  of differential casing  12 . 
     The order of assembly for locking differential  10  is best illustrated in  FIG. 2 . As noted above, actuator  22  and gasket  92  may be received upon protrusion  94  of differential casing  12 , with actuator pins  26  received within actuation apertures  28 . This assembly takes place along a first axial direction, opposed to an opposing axial direction leading into hollow cavity  36 . 
     The remaining components of locking differential  10  (excluding axle half shafts  40 ,  42 ) take place along the opposing axial direction, as these remaining components are advanced into or toward the opening leading to hollow cavity  36 . First, right clutch plate  30  is received into hollow cavity  36  along longitudinal axis A, followed by right side gear  16 , which is placed into splined engagement with clutch plate  30  as described above. 
     Pinion housing  20  is then received within hollow cavity  36  to align pinion shaft apertures  100  formed in pinion housing  20  with corresponding pinion shaft apertures  102  formed in differential casing  12 . Pinion gear  18  may then be received within the cavity of pinion housing  20 , and pinion shaft  76   a  may be received entirely through apertures  102 ,  100 , the axial bore of an opposing pair of pinion gears  18 , and back through apertures  100  and  102 . Pinion gear axial shafts  76   b , which may be two separate half shaft pieces, may then be received within a respective set of apertures  102  and  100 , and one of pinion gears  18 . 
     Next, left side gear  14  is received within hollow cavity  36  and brought into splined engagement with pinion gears  18  as described above. Left clutch plate  34  is then received within hollow cavity  36  and brought into splined engagement with the outer surface of left side gear  14 , also described above. Finally, differential end plate  38  is affixed to the end surface of differential casing  12 , and fasteners  58  are used to affix end plate  38  to casing  12 . With locking differential  10  thus assembled, differential casing  12  may be mounted into engagement with drive shaft  44  and axle half shafts  40 ,  42  as described above. 
     Turning now to  FIGS. 9 and 10 , selected components of an alternative locking differential  10   a  are shown. Differential  10   a  is nearly identical to locking differential  10  illustrated in  FIGS. 1-8 . Similar components of differential  10   a  are identified by the same reference numeral used with respect to differential  10  but are followed by the alphabetic designator “a”. Moreover, differential  10  and differential  10   a  have all the same components with the same reference numeral designations, except as otherwise specified in the following discussion. Thus, for example, differential  10   a  includes differential casing  12  and actuator  22  even though these components are omitted from  FIGS. 9 and 10  for clarity. 
     As best seen in  FIG. 9 , differential end plate  38   a  includes a plurality of pins  56   a  formed in end surface  39   a , in which pins  56   a  extend inwardly into hollow cavity  36  of differential casing  12  and toward actuator  22  when end plate  38   a  is assembled to casing  12 . Clutch plate  34   a  includes a corresponding plurality of receiving slots or recesses  54   a  sized and positioned to selectively receive pins  56   a , such that when clutch plate  34   a  is urged into abutting contact with differential end plate  38   a  as shown in  FIG. 10 , pins  56   a  are received within recesses  54   a  to rotatably lock clutch plate  34   a  to differential casing  12  in similar fashion to rotatable locking of clutch plate  34  to casing  12  effected by interfitting of castellations  54  and  56  described above with respect to differential  10 . 
     Similarly, a plurality of pins  52   a  are arranged around the periphery of end surface  21   a  of pinion housing  20   a , and protrude from outwardly from end surface  21   a  toward actuator  22   a . Clutch plate  30   a  includes a number of recesses  50   a  sized and positioned to selectively receive pins  52   a . When pins  52   a  are received in recesses  50   a  as shown in  FIG. 10 , clutch plate  30   a  is rotatably fixed to pinion housing  20   a  in similar fashion to the rotatably fixed arrangement of clutch plate  30  when castellations  50 ,  52  are interfitted with one another as described above. 
     Moreover, it is contemplated that pins  52   a ,  56   a  may be considered rotatably fixed “castellations” for purposes of the present disclosure, as pins  52   a ,  56   a  form axially outwardly extending structures which can serve to rotatably fix clutch plates  30   a ,  34   a  to their respective adjacent structures. Similarly, the protrusions which respectively flank and define recesses  50   a ,  54   a  may also be considered rotatable “castellations” for the same reason. 
     Similar to differential  10 , differential  10   a  utilizes a single actuator  22  which, when actuated, operates to urge clutch plate  30   a  toward pinion housing  20   a  and thereby rotatably fix both of clutch plates  30   a  to differential casing  12  via pinion housing  20   a . As illustrated, pinion housing  20   a  includes a plurality of lock pins  32  which transmit the axial translation of clutch plate  30   a  to clutch plate  34   a  in the same manner as described above with respect to differential  10 , such that actuation of actuator  22  also rotatably fixes clutch plates  34   a  to differential casing  12  via end plate  38   a . Biasing elements  33  are provided to urge clutch plates  30   a  and  34   a  out of such engagement when actuator  22  is not actuated. 
     In an exemplary embodiment, pins  52   a  or pins  56   a , or both, are separate components received in correspondingly formed bores formed in pinion housing  20   a  and end plate  38   a , respectively. This facilitates efficient and inexpensive manufacture of pinion housing  20   a  and end plate  38   a , while adding negligible time and effort to assembly of differential  10   a.    
     While this disclosure has been described as having exemplary designs, the present disclosure can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this disclosure pertains and which fall within the limits of the appended claims.