Abstract:
The present invention provides a differential housing having guide slots formed therein. The guide slots permit movement of pinion shaft axially therethrough. A plurality of apertures are provided in the housing for properly positioning a pinion shaft within the housing. The apertures further provide fluid communication between the exterior and the interior of the housing to aid in adequately lubricating the components within the differential housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority from U.S. Provisional Patent Application No. 60/784,844 entitled “STRUCTURE OF DIFFERENTIAL HOUSING” filed on Mar. 22, 2006, which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention is generally related to mechanical differentials, and more particularly to an improved differential housing.  
       BACKGROUND  
       [0003]     Differentials are known in the automotive industry as devices that split engine torque two ways, allowing each output to spin at a different speed. 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 transmission to the wheels; and to transmit the power to the wheels while allowing them to rotate at different speeds.  
         [0004]     A typical mechanical differential contains a housing (or carrier), two side gears, and several pinion gears. A rotating driveshaft of the vehicle engages a ring gear, which is mounted onto the differential housing. The driveshaft drives the ring gear, which in turn rotates the differential housing. Pinion shafts attach the pinion gears to the housing so that, as the housing rotates, the pinion gears are driven. The pinion gears drive the two side gears, which in turn drive the axle (or half shafts) attached thereto.  
         [0005]     The pinion shafts of the differential are supported by the differential housing so that the torque of the housing can be transmitted to the pinion shafts and thereby drive the pinion gears. The pinion gears spin upon the pinion shafts and rotate about the axis of the housing. A conventional differential housing utilizes either holes or slots in the wall of the differential housing to support the pinion shafts.  
         [0006]     Pinion slots in the differential housing are shown in U.S. Pat. No. 6,743,138 issued to Visteon Global Technologies, Inc., hereby expressly incorporated by reference herein. As shown in  FIGS. 3, 4 , and  6 , these slots assist in the assembly of the differential by permitting the axial loading of the pinion and gear set (e.g. spider-type pinion set). Specifically,  FIG. 3  illustrates a differential housing  2  having slots  4  for axially loading a pinion shaft  6  having pinion gears  8 . For example, the pinion gears  8  are secured to the pinion shaft  6  prior to axially inserting the pinion assembly into the housing  2 . A cover  11  secures to the housing  2  to complete the assembly.  FIG. 4  illustrates a spider pinion shaft  12  having four pinion gears  8  attached thereto. The spider pinion shaft  12  is axially inserted into the housing  2  by sliding within four slots  4  in the housing  2 .  
         [0007]     Another known differential assembly utilizes holes  20  in the differential housing  2  as shown in  FIGS. 1, 2 , and  5 . The holes  20  permit a pinion shaft  22   a  to be inserted radially through the housing  2  from the exterior during assembly and supported therein during operation by locking pins mounted through the pinion shaft  22   a  and into the housing  2 . The holes  20  support the pinion shaft  22   a - 22   c  such that the pinion gears  8  meshingly engage side gears  19 . The pinion gears  8  may, for example, be positioned within the housing  2 , and the pinion shaft  22   a  may be inserted from the outside of the housing  2  through each of the pinions gears  8 .  
         [0008]     Specifically,  FIG. 2  illustrates four holes  20  in the housing  2  for insertion of the three pinion shafts  22   a - 22   c.  One of the pinion shafts  22   a  is capable of being inserted through one of the holes  20  from outside the housing  2 . After insertion of the long pinion shaft  22   a,  the other pinion shafts  22   b,    22   c  may be inserted through the holes in the housing  2 . However, the hole-type design requires locking pins  25  for securing the shafts  22   a - 22   c  to the housing  2 .  
         [0009]     In addition, the hole-type design requires insertion of the pinion gears  8  into the housing  2  and feeding the shafts  22   a - 22   c  through the pinion gears  8 . Therefore, with the hole-type feature, the pinion shafts  22  are separate parts that are inserted into the support holes  20  from the outside of the housing  2  during the assembly process requiring the coordination of numerous separate parts and assembly steps.  
         [0010]     A spider pinion shaft  12  or a pinion shaft  6  having the pinion gears  8  attached thereto cannot be used with the differential housing  2  having the holes  20 . The spider pinion shaft  12  requires the slots  4  for sliding the spider pinion shaft  12  into the housing  2 . However, manufacturing the slot  4  is more expensive and requires special-purpose machines, like broach machines or coining machines, to process the slot  4  in an accurate circumferential position while maintaining an accurate width. Incorrect circumferential positioning of the pinion shafts  12  can cause extra damage load to the gear contact surfaces. Accurate slot width is necessary to ensure that the pinion shaft  12  can slide axially in the slots  4  without deflecting too far circumferentially. Too much circumferential deflection is detrimental to the contact surfaces of the pinion gears  8  and the pinion shaft  12 .  
         [0011]     Moreover, each of these known differential assemblies fails to provide adequate lubrication to the pinion gears  8  and the interior of the housing  2 . In the hole-type embodiment, lubrication is limited from flowing through the housing  2  via the holes  20  due to the snug fit of the shafts  22   a - 22   c  in the holes  20 . On the other hand, the slot-type design fails to provide any apertures in the housing for lubrication.  
         [0012]     Accordingly, there is a need in the art for a differential housing capable of supporting axially loading pinion shafts, such as a spider pinion shafts, as well as supporting pinion shafts inserted from the outside of the housing, if desired. In addition, there is a need in the industry for a housing capable of using slots and holes to provide adequate lubrication to the pinion gears while maintaining the structural integrity of the housing. Moreover, there is a need to provide a housing capable of supporting pinion shafts without the use of locking pins while providing adequate lubrication into the housing.  
       SUMMARY OF THE INVENTION  
       [0013]     The present invention provides a differential housing having both guide slots and radial apertures. The guide slots and the radial apertures may overlap such that pinion shafts may be axially inserted axially through the guide slots and supported within the apertures. The apertures may further provide fluid communication for lubricating fluid, such as oil, through the housing to properly lubricate the various components of the differential housing assembly. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a cross-sectional view of a typical differential with pinion shaft support holes therethrough.  
         [0015]      FIG. 2  is a cross-sectional view of the differential of  FIG. 1  taken generally along line A-A.  
         [0016]      FIG. 3  is a cross-sectional view of a typical differential with pinion shaft support slots therein.  
         [0017]      FIG. 4  is a cross-sectional view of the differential of  FIG. 3  taken generally along line A-A.  
         [0018]      FIG. 5  is a cross-sectional view of a typical differential housing having pinion shaft support holes there through.  
         [0019]      FIG. 6  is a cross-sectional view of a typical differential housing with pinion shaft support slots therein.  
         [0020]      FIG. 7  is a cross-sectional view of a differential housing according to an embodiment of the invention.  
         [0021]      FIG. 8  illustrates an embodiment of a differential housing having a pinion shaft insertable therethrough. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     A typical differential with the hole-type design is shown in  FIGS. 1, 2 , and  5 . A typical differential with a slot-type design is shown in  FIGS. 3, 4 , and  6 . An embodiment of the invention disclosed herein is shown in  FIG. 7 .  
         [0023]     As shown in  FIG. 7 , a differential housing  52  that has an inner wall  54  and an outer wall  56  defining an interior  58  of the differential housing  52 . The interior  58  is capable of housing side gears, pinion gears and pinion shafts as illustrated in  FIGS. 1-6 . An opening  90  is located axially at one end of the housing  52  which provides access to the interior during assembly. A cover is securable to the housing  52  after assembly to close the opening  90 , such as the cover  11  as illustrated in  FIG. 1 .  
         [0024]     The differential housing  52  has apertures  60  and guide slots  70  therein. The combination of the apertures  60  and the guide slots  70  is generally more advantageous for differential assemblies having more than two pinion gears, multiple pinion shafts and/or a spider pinion shaft. However, one of ordinary skill in the art will appreciate that the invention may be used with any number of pinion gears and/or pinion shafts.  
         [0025]     As shown in  FIG. 7 , the guide slots  70  may be located along the inner wall  54  of the differential housing  52 . For example, the guide slots  70  may extend axially or longitudinally from the opening  90  along the inner wall  54  of the housing  52  toward the interior  58  a predetermined distance from the opening  90 . The guide slots  70  allow the sliding of pinion shafts into the housing  52  during assembly. Advantageously, the guide slots  70  provide for axial insertion of pinion shafts  91  having pinion gears  92  previously mounted thereon, as illustrated in  FIG. 8 .  
         [0026]     Termination of the guide slots  70  may occur in the interior  58  at a predetermined distance from the opening  90 . At the predetermined distance, the pinion shafts  91  may be properly positioned within the differential housing  52 . In an embodiment, the housing  52  may have four guide slots  70  for the insertion of one or more pinion shafts  91 . For example, the spider pinion shaft assembly  12  of  FIG. 4  may be axially inserted into the housing  52  via the guide slots  70 . The guide slots  70  may align such that two confronting guide slots  70  allow axial insertion of the vertical portion of the pinion shaft  91  within the housing  52  while two additional radially offset guide slots  70  allow axial insertion of the horizontal portion of the pinion shaft  91 . Nevertheless, the present invention should not be deemed as limited to any specific number of pinion shafts  91 , guide slots  70 , and/or any specific number of apertures  60 .  
         [0027]     To assist in the axial loading and support of the pinion shafts  91 , the height H of the guide slots  70  may decrease toward the interior  58  of the housing  52 . The width W of the guide slots  70  may also decrease toward the interior  58  of the housing  52 . To this end, insertion of the pinion shafts  91  may be essentially be snap-fitted through the guide slots  70  into their set position to assist in preventing axially movement or disengagement of the pinion shaft  91  from their set position within the interior  58  of the housing  52 .  
         [0028]      FIG. 7  further shows apertures  60  extending axially through the housing  52 . The apertures  60  extend through the outer wall  56  and the inner wall  54  to provide fluid communication between the exterior of the housing  52  and interior of the housing  52 . Fluid, such as oil, may lubricate the pinion shafts  91 , pinion gears  92 , side gears and/or the other components through the apertures  60  to prevent friction and debris buildup.  
         [0029]     The apertures  60  may extend through the differential housing  52  so that the apertures  60  and the guide slots  70  are in communication with each other. In an embodiment, each of the guide slots  70  may have a corresponding aperture  60 . The apertures  60  may be positioned at the terminal end of the guide slots  70  and sized and shaped to support the pinion shafts therein. For example, the guide slots  70  may connect the opening  90  of the differential housing  52  with the apertures  60  so that a spider-type pinion shaft may be assembled through the guide slots  70  and into the apertures  60 .  
         [0030]     The apertures  60  may overlap the guide slots  70  at overlap regions  100 . As the width W and the height H of the guide slots  70  decrease toward the interior  58  of the housing  52 , there may be an increased resistance to the insertion of the pinions shafts  91 . Accordingly, the pinion shafts  91  may move through the guide slots  70  and snap into the apertures  60  such that the pinion shafts  91  will not shift significantly from their set position. For example, together the guide slots  70  and the apertures  60  may allow axial insertion of the pinions shafts into the interior  58  of the housing  52  such that the pinion shafts will snap or otherwise securely fit in the apertures  60 . Advantageously, the present invention is capable of properly positioning the pinion shafts  91  such that locking pins are not required, as shown in  FIG. 2 .  
         [0031]     As a further advantage, the overlap region  100  allows the present invention to increase the allowable tolerances permitted in the construction of the housing  52 , thus reducing costs for manufacturing. For example, the pinion shaft  91  is insertable through the guide slots  70  and supportable within the apertures  60  in a fashion in which the accuracy of circumferential positioning and width of the slots and apertures are easier achieve with a low-cost manufacturing machine than the known slot-type differentials as shown in  FIG. 6 .  
         [0032]     Still another advantage of the present invention is that the apertures  60  allow fluid communication through the housing  52 . Known hole-type differentials provide a tight fit of the pinion shafts  91  into the apertures  60  such that fluid communication is very limited. Typically, the pinion shafts  91  of known differentials are pinned to the housing so that fluid communication is very limited because there may be no axial play and/or movement possible by the pinion shaft  91 . The present invention, however, allows limited axial movement of the pinion shafts  91  within the apertures  60  as designed to aid in lubrication.  
         [0033]     Moreover, in at least one embodiment, the guide slots  70  may be produced inexpensively, for example, by die casting due to the guide slots  70  functioning only to aid in assembly. The apertures  60  may also be produced relatively inexpensively, for example, by use of a drill and milling machine. The size and the location of the apertures  60  can be precisely produce to support a pinion gear assembly, such as, the spider pinion gear assembly.  
         [0034]     While the invention has been described with reference to the preferred embodiment, other modifications and design changes can be appreciated upon reading the disclosure along with the accompany drawings while also falling within the scope of the invention as described and claimed. As such, nothing in the present description should be implied to limit the invention from what is claimed below.