Abstract:
A pin retention and assembly system that is used with vehicles, such as, off-road vehicles is provided. The pin retention and assembly system has modular locking pins engaging a collar positionable about a bearing journal of a differential housing. Channels are formed in the bearing journal for receiving the locking pins. The channels aid in maximizing the size of the bearing journal. The locking pins engage the collar to lock the differential housing. In an embodiment, the locking pins and locking apertures in the differential housing are orientated asymmetrically causing the number of locking pins to be independent to the apertures in the side gear.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Patent Application No. 60/784,843 entitled “PIN RETENTION SYSTEM FOR LOCKING DIFFERENTIAL” filed on Mar. 22, 2006; U.S. Provisional Patent Application No. 60/784,842 entitled “PIN RETENTION AND ASSEMBLY SYSTEM FOR LOCKING DIFFERENTIAL” filed on Mar. 22, 2006; and U.S. Provisional Patent Application No. 60/789,080 entitled “LOCK PIN RADIAL ORIENTATION FOR A LOCKING DIFFERENTIAL” filed on Apr. 4, 2006, each of which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to locking differentials, and more particularly, to a pin retention and assembly system for locking differentials. 
     BACKGROUND 
     Differentials are known in the automotive industry as devices that split engine torque two ways, allowing each output to spin at a different rate. Generally, differentials have three primary tasks: to aim the engine power at the wheels; to act as the final gear reduction in the vehicle, slowing the rotational speed of the transmission one final time before being transferred to the wheels; and to transmit the power to the wheels while allowing them to rotate at different speeds. 
     In a typical vehicle application, the rotating driveshaft of the vehicle engages a ring gear, which is mounted onto the differential housing. Thus, the driveshaft drives the ring gear, which in turn rotates the differential housing. A typical mechanical differential contains a housing (or carrier), two side gears, and several pinion gears. Pinion shafts attach the pinion gears to the housing so that as the housing rotates the pinion gears are driven. Specifically, inputting torque to the housing drives the pinion shaft that, in turn, drives the pinion gears. The pinion gears drive the two side gears, which in turn drive the axle (or half shafts) attached thereto. 
     Locking differentials are used predominantly on vehicles intended for off the road use, such as tractors, agricultural machines, military vehicles, all terrain vehicles, etc. Frequently, the half-shafts of off-road vehicles will experience different resistive couples due to, for example, the roughness of the ground and/or a slippery surface. In such a case, if the differential is not partially or totally excluded from functioning, then the half-shaft or the wheel experiencing the least amount of resistance from the ground will receive the majority of the power. As a result, the vehicle will lose traction. 
     Conventional locking differentials are constructed such that the pinion gears are mounted to the differential casing or housing and the differential input gear. The side gears engage the pinion gears to rotate the left and right axles. A typical locking differential includes apertures in the differential housing to allow locking pins to enter therethrough and engage the side gear. Therefore, the differential housing is locked so as not to transmit torque through the gear set by the locking pins engaging the side gears. When the differential is locked, e.g. the locking pins engage the side gear, the rear axles are locked together and rotate at the same speed. When the differential is to be unlocked, the locking pins are removed from the side gear and the rear axles are permitted to rotate at different speeds. 
     The locking pins are typically mounted to a circular collar. Therefore, when the collar is engaged, the collar and locking pins move axially relative to the differential housing. Specifically, the locking pins slide within the differential housing into engagement with the side gear, thus locking the differential housing relative to the gear set. 
       FIG. 1  illustrates a known locking differential design having five radial apertures  3  located symmetrically about a side gear  4 .  FIG. 2  illustrates a known differential housing  5  having locking apertures  6  that are positioned to correspond to the apertures  3  of the side gear  4 . Specifically, the locking apertures  6  are spaced symmetrically about the housing  5 .  FIG. 3  illustrates a known collar  8  having equally symmetrically spaced pins  7  for engagement with the locking apertures  6  of the housing  5  and the apertures  3  of the side gear  4 . 
       FIG. 4  illustrates how the components of  FIGS. 1-3  interact in a known differential assembly  9 . Specifically, the differential assembly  9  includes the differential housing  5 , the side gears  4  and pinion gears  2 . The known differential locking assembly  9  also has a bearing journal  11  formed therethrough. The bearing journal  11  is sized to receive front axles or rear axles of a vehicle (not shown) that are connected to the side gears  4 . 
     A pinion shaft  10  attaches the pinion gears  2  to the housing  5 . The collar  8  moves about the bearing journal  11  to engage the side gears  4  and the housing  5 . The pins  7  are located radially outward from the bearing journal  11 . More specifically, the locking pins  7  extend from the collar  8  into the housing  5 . In use, each of the pins  7  engage the aperture  3  in the side gear  4  and the locking apertures  6  of the housing  5  to lock the housing  5  to the side gear  4 . 
     Significant machining and complex assembly is needed for such known locking differentials. Particularly, the manufacture of the collar  8  and the locking pins  7  are required to be extremely precise so that each of the locking pins  7  enters each of the locking apertures  6  machined in the differential housing  5 . Such manufacturing and assembly has created problems when one of the locking pins  7  is misaligned or one of the locking apertures  6  is slightly off-center. In addition, such precise machining is time-consuming and greatly increases manufacturing costs. 
     As illustrated in  FIG. 4 , the locking pins  7  and the locking apertures  6  have been located in a radial pattern significantly larger than the bearing journal  11 . In several applications, it is desirable to reduce the overall radial pattern of the locking pins  7  while increasing or at least maintaining the size of the bearing journal  11 . Further, there is always a desire to improve the manufacture and assembly of locking differentials. 
     However, efficient design of the locking differential depends on the size and stresses related to the components. There is a constant need in the art to minimize contact stresses and to achieve a compact sized differential. It is an object of the present invention to address these needs in providing an improved design. Further, there is a constant need in the field to improve upon component design and manufacturing and assembly techniques for locking differentials to reduce costs and time associated with all stages of manufacture and assembly. 
     SUMMARY OF THE INVENTION 
     A pin retention and assembly system that may be used with vehicles, such as, off-road vehicles is disclosed. The pin retention and assembly system has modular locking pins engaging a collar positionable about a bearing journal of a differential housing. Channels are formed in the bearing journal for receiving the locking pins. The locking pins engage the collar to lock the differential. In an embodiment, the locking pins and locking apertures in the differential housing are orientated asymmetrically so that the number of locking pins is independent to the number of apertures in the side gear. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Objects and advantages together with the operation of the invention may be better understood by reference to the following detailed description taken in connection with the following illustrations, wherein: 
         FIG. 1  illustrates a known side gear having symmetrically orientated apertures. 
         FIG. 2  illustrates a known differential housing having symmetrically orientated locking apertures formed therein. 
         FIG. 3  is a cross-sectional view of a known collar having symmetrically orientated locking pins extending therefrom. 
         FIG. 4  is a known locking differential assembly having a collar, side gears and pinion gears. 
         FIG. 5  illustrates a differential assembly having a bearing journal and channels formed therein in an embodiment of the present invention. 
         FIG. 6  illustrates another view of a differential housing having a bearing journal and channels formed therein in an embodiment of the present invention. 
         FIG. 7A  is a side perspective view of a locking pin having a groove in an embodiment of the present invention. 
         FIG. 7B  is a cross-sectional view of the locking pin of  FIG. 7A . 
         FIG. 8  illustrates a differential housing having symmetrical locking apertures and channels in an embodiment of the present invention. 
         FIG. 9  illustrates a collar having half round apertures in an embodiment of the present invention. 
         FIG. 10  is a cross-sectional view of  FIG. 9 . 
         FIG. 11  illustrates a differential assembly having channels and modular locking pins in an embodiment of the present invention. 
         FIG. 12A  illustrates a collar having asymmetrical locking apertures in an embodiment of the present invention. 
         FIG. 12B  illustrates a cross-sectional view of the collar of  FIG. 12A . 
         FIG. 13  illustrates a differential housing having asymmetrical locking apertures and channels in an embodiment of the present invention. 
         FIG. 14  illustrates a side gear having apertures extending into the side gear at teeth of the side gear in an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is directed to a pin retention and assembly system for a differential housing. It should be understood that nothing in the following description of the preferred embodiment should limit the scope of the invention to the preferred embodiment. 
       FIGS. 5 and 6  illustrate a locking differential assembly  100  in an embodiment of the present invention. The assembly  100  includes a differential housing  12 , side gears  18  and pinion gears  20  attached to a pinion shaft  32 . The differential housing  12  has a bearing journal  23  therethrough. A collar  22  having locking pins  16  extending therefrom is slidable to engage locking apertures  60  of the housing  12  and apertures  50  in the side gear  18 . 
     The bearing journal  23  has channels  70  as illustrated in  FIGS. 5 and 6 . The channels  70  may be located radially about the housing  12 . In an embodiment, the channels  70  may be formed and/or located within or slightly above the bearing journal  23 . In a preferred embodiment, the channels  70  are radially aligned to correspond to the position of the locking apertures  60  and/or the locking pins  16 . In such an embodiment, each channel  70  may be sized and shaped to receive a single locking pin  16 . 
     The channels  70  are sized and shaped such that the locking pins  16  are movable within the channels  70 . The shape of the channels  70  may be circular, rectangular with rounded corners, oval and/or the like. The present invention should not be deemed as limited to any specific shape and/or length of the channels  70 . One of ordinary skill in the art will appreciate that the channels  70  may have many shapes and/or configurations within the spirit of the present invention. 
     The channels  70  may permit the locking pins  16  to be supported therein. In addition, the channels  70  may permit a larger sized bearing journal  23  of the differential housing  12 . Furthermore, the channels  70  may simplify the assembly process of the differential housing  12 .  FIG. 8  shows the housing  12  having the locking apertures  60  and a plurality of the channels  70  located radially about the housing  12 . 
       FIGS. 7A and 7B  illustrate an embodiment of the locking pins  16  having a groove  30 . In such an embodiment, the locking pins  16  are modular and manufactured separately from the collar  22 . The locking pins  16  may be generally round and elongated members. In one embodiment, the locking pins  16  are cylindrical in shape. The locking pins  16  may have any shape for engaging the locking apertures  60 , the apertures  50  of the side gear  18  and/or the collar  22 . The locking pins  16  should not be deemed as limited to any specific shape. 
     It should be noted that the collar  22  and the locking pins  16  can be independently manufactured relatively inexpensively due to the non-complex design of the collar  22  and the locking pins  16 . Further, given the modular design, the locking differential assembly  100  can be easily disassembled to replace any component as necessary. In an embodiment, a groove  30  is formed adjacent one of the ends of the locking pin  16 . The groove  30  may be a cut-out portion, a slot, a notch and/or the like. The groove  30  is capable of engaging the collar  22  to secure the locking pin  16  to the collar  22 . 
     The groove  30 .may engage a body  24  of the collar  22  as shown in  FIG. 11 . For example, the groove  30  may engage a support aperture  28  of the collar  22 . The support aperture  28  is provided in the collar  22  and is sized such that the collar  22  may move axially about said bearing journal  23 . Rotation of the collar  22  may lock or otherwise secure the locking pins  16  onto the support aperture  28  of the collar  22 . 
     In a preferred embodiment of the present invention, the support aperture  28  of the collar  22  has a plurality of outward extending half-round apertures  80  as illustrated in  FIG. 9 . The half-round apertures  80  may correspond in number to the locking apertures  60  in the differential housing  12 . In addition, the half-round apertures  80  may correspond in number and in shape to the locking pins  16 . In a preferred embodiment, the half-round apertures  80  are shaped for engagement with the groove  30  of each of the locking pins  16 . As such, the shape of the half-round apertures  80  may be any shape as will be appreciated by one of ordinary skill in the art. 
     The half-round apertures  80  are positioned and/or aligned on the grooves  30  of the locking pins  16  prior to rotation of the collar  22  to secure the locking pins  16  to the collar  22  as illustrated in  FIG. 11 . In one such embodiment, the locking pins  16  may be pre-positioned in the channels  70 . The collar  22  may then be axially assembled over the locking pins  16  and rotated to engage the body  24  of the collar  22  into the grooves  30  of the locking pins  16 . Thus, the locking pins  16  may be secured by wedge-type engagement with the grooves  30 . The collar  22  may be secured from further rotation by methods that will be appreciated by one of ordinary skill in the art, such as, for example, a pin or a screw. 
     In another embodiment, the collar  22  may not require the half-round apertures  80 . While not preferred, such an embodiment may require that the locking pins  16  be pre-positioned onto the body portion  24  of the collar  22  prior to assembly of the collar  22  on the housing  12 . 
       FIG. 10  illustrates a cross-sectional view of the collar  22  of  FIG. 9 . The collar  22  has the body or flange portion  24 , an actuator  26 , and the support aperture  28 . The support aperture  28  is sized and shaped to engage the bearing journal  23 . Preferably, the support aperture  28  is slightly larger in diameter than the outer diameter of the bearing journal  23  so that the collar  22  can be axially assembled onto the bearing journal  23 . The collar  22  may, therefore, be capable of sliding or otherwise moving over the bearing journal  23 . The actuator  26  of the collar  22  is engaged, for example, mechanically, pneumatically or automatically to move the collar  22 . 
     As illustrated in  FIGS. 10 and 11 , the collar  22  may be moved axially along the bearing journal  23  so that the locking pins  16  are engagable with the differential housing  12 . For example, the locking pins  16  may move into the locking apertures  60  to engage the side gear  18  and lock the differential assembly  100 . The locking pins  16  may move axially along the channels  70  so as to maintain a proper position relative to the locking apertures  60 . 
     As shown in  FIGS. 1-4 , the locking apertures  6  of the housing  5  of the prior art have tended to be oriented symmetrically so that the locking mechanism can engage during each pass of a corresponding side gear aperture. However, the efficient location and number of side gear apertures depends upon the configuration of the side gear. Likewise, the efficient location and number of locking apertures in the differential housing depends upon the configuration of the side gear apertures. 
     In another embodiment of the present invention, the collar  22  and the locking pins  16  are oriented so as to minimize contact stresses by maximizing the contact areas of the locking pins  16  and the side gear apertures  50 . In addition, the present invention may provide a compact sized differential assembly  100  by providing a minimum axial dimension of the side gear  18 . A further object of the present invention is to provide design flexibility so that the number of locking pin apertures can be independent of the number of the side gear apertures  50 . 
     As shown in  FIG. 14 , the side gear  18  has a plurality of side gear apertures  50  located thereon and/or positioned radially about the side gear  18 . In such an embodiment, the side gear  18  may have more apertures  50  than the five symmetrical apertures  3  typically located in the side gear  4  of the prior art. The present invention should not be deemed as limited to any number and/or any location of the side gear apertures  50 . 
     Specifically,  FIG. 14  illustrates an embodiment of the present invention where the side gear  18  has thirteen teeth  90  and thirteen side gear apertures  50 . The positions of the side gear apertures  50  may be aligned with the location of the teeth  90  of the side gear  18  in such a way that the axis of at least one of the side gear apertures  50  is in the plane which divides one gear tooth  90  into, for example, two equal halves. The present invention should not be deemed as limited to any specific number of the side gear apertures  50  and/or any number of locking apertures  60 . 
     To minimize contact stresses, the overlap length of the locking pins  16  and the side gear apertures  50  should be as large as possible. Deeper side gear apertures  50  may provide longer overlap length of the locking pins  16  and side gear apertures  50 . Typically, the deepest side gear apertures  50  can be made in the side gear  18  when the side gear apertures  50  are aligned with the side gear teeth  90 . At such a position, the material of the side gear  18  is at a maximum thickness or depth. Otherwise, the side gear apertures  50  may penetrate the gear face or make the gear face too thin to bear load. Thicker side gears  18  can also provide depth of material for deeper side gear apertures  50 , but this also results in a larger size and weight of the components and the differential assembly  100 . 
     The number of side gear teeth  90  may be orientated for smooth transmission of torque and rotation speed while minimizing size and weight of the differential assembly  100 . The number of locking pins  16  is designed for smooth engagement and disengagement. Advantageously, the present invention seeks to reduce the engagement time of the locking pins  16  with the side gear apertures  50 . If, for example, the side gear apertures  50  and the locking apertures  60  in the housing  12  are axially symmetrical, the number of side gear apertures  50  and the number of the locking apertures  60  is required to be equal. Alternatively, the number of side gear apertures  50  is required to be dividable wholly by the number of locking apertures  60  in the housing  12 . 
     As illustrated in  FIG. 13 , the axially asymmetric pattern of the locking apertures  60  allows the matching of the locking apertures  60  with the side gear apertures  50  even when the number of side gear apertures  50  is not equal to the number of locking apertures  60 . In addition, the asymmetric pattern of the locking apertures  60  eliminates the need for having the number of side gear apertures  50  to be dividable wholly by the number of the locking apertures  60 . Therefore, the asymmetric pattern allows for the number of the locking apertures  60  in the housing  12  to be independent to the number of side gear apertures  50 . Advantageously, such an embodiment provides a differential assembly  100  that does not limit the number of side gear teeth  90  when deep apertures are necessary for large overlap length of the locking apertures  60  and the side gear apertures  50 . Furthermore, the quantity and cost of the locking pins  16  and the locking apertures  60  may be reduced while maintaining the integrity of the locking function. 
       FIGS. 12A and 12B  illustrate an embodiment of the present invention where the locking pins  16  are integrally formed with the collar  22  in an asymmetrical pattern. Of course, the collar  22  may have modular locking pins  16  having grooves  30  for engagement with the support aperture  28  of the collar  22  as shown in  FIG. 11 . Furthermore, in an embodiment the locking pins  16  may lock with the half-round apertures  80  of the collar  22  in an asymmetric pattern. 
     The collar  22 , as illustrated in  FIGS. 12A and 12B , have five asymmetrical locking pins  16  attached thereto. The asymmetrical orientation of the locking pins  16  permits engagement at any rotational position without having to provide equal or divisible numbers of side gear apertures  50  and the locking apertures  60 . 
     While the invention has been described with reference to the preferred embodiment, other modification and design changes can be appreciated upon reading the disclosure along with the accompanying drawings. As such, nothing in the present description should be implied to limit the invention from what is claimed below.