Abstract:
An salisbury axle assembly that includes a differential gearset in a carrier housing. A housing cover is coupled to the carrier housing and is operable for sealingly closing a window on the carrier housing through which there is access to the differential gearset. The housing cover includes a cover member and a seal ring. The cover member includes a mating face and a plurality of raised connection points that are disposed between the carrier housing and the mating face The seal ring is coupled to the mating face and encircles each of the raised connection points. The seal ring further includes at least first and second ring members that are disposed between each of the raised connection points. The pre-attach seal ring sealingly engages the carrier housing and the mating face to a proper compression distance.

Description:
FIELD 
     The present invention relates to a differential cover for a vehicle drivetrain assembly and further relates to a double seal ring that is pre-attached to the differential cover that also includes integral compression limiters. 
     BACKGROUND 
     A differential assembly houses a gear assembly that is traditionally configured to change a direction of a power input from a drive shaft to two half shafts. The drive shaft receives power from an engine and through a transmission, while the half shafts deliver power to the wheels from the differential assembly. With reference to  FIG. 1 , the differential assembly is generally indicated by reference numeral  10 . A drive shaft  12  enters a differential assembly housing  14 , also referred to as a carrier housing  14 , at a front portion  16  of the housing  14 . A gear assembly  17 , or differential gear set, transfers power to a right half shaft  18   a  and a left half shaft  18   b,  which hereinafter are collectively referred to as half shafts  18 . The housing  14  also has a plurality of mounting brackets  20  that are configured to secure the differential assembly  10  within the applicable subassemblies (not shown) of the vehicle (not shown). 
     Based on their construction, solid beam axle housings can be divided into two groups, an integral carrier, or a removable carrier. The integral carrier housing attaches directly to the rear suspension. A service cover, in the center of the housing, fits over the rear of the differential and axle assembly. When service is required, the cover must be removed and the components of the differential unit are then removed. Integral carriers are also commonly referred to as unitized or salisbury-type differentials, named after C. W. Salisbury one of the founders of Salisbury Axle Company. 
     A removable carrier assembly is configured so that the gearing assembly can be removed from the front of the differential housing as a unit, when the front portion of the differential housing unit is removed. With reference to rear live axles, a rear axle refers an axle mounted in the rear of a vehicle and to the rear tires. The front of the rear axle refers to the area which the driveshaft connects thereto and live denotes that the axle carries power, such as in a rear wheel drive vehicle. The typical housing of a removable carrier assembly has a cast-iron center section with axle shaft tubes pressed and welded into either side. The removable carrier assembly is sometimes called a “banjo” because of the bulge in the center of the housing. The bulge contains the final drive gears and differential gears. In appearance, the two designs of axle housing look similar except that the opening for the differential unit on a banjo axle is at the front and the rear of the housing is solid, while access to the salisbury axle is through a rear service cover. 
     It will be appreciated that variations of the salisbury and the banjo axles exist, such as independent front and rear axles. With an independent front or rear axle, the differential housing is mounted to the vehicle&#39;s chassis. As such, the differential housing does not move with the suspension. The half axles, however, are connected to the wheels of vehicle which are suspended. To that end, constant velocity joints are used to connect the half axles to the differential assembly and the wheel hubs so that the half axles are able to move with the suspended wheels. The differential housing remains unsuspended and secured to the applicable subassemblies of the vehicle. 
     With reference to  FIG. 1  and  FIG. 2 , the housing  14  further includes a differential assembly cover  22 , which attaches to a rear portion  24  of the housing  14  with a plurality of fasteners  26 . The rear portion  24  defines a window  24   a  that provides access to the interior cavity of the housing  14 . It will be appreciated that the differential assembly  10  is salisbury differential, as the cover  22  is a separate component that is releaseably connected to the rear of the housing  14 . Disposed between the housing  14  and the differential assembly cover  22  is a gasket  28 . The gasket  28  seals the differential assembly cover  22  to the housing. By sealing the cover  22  to the housing  14 , the gear assembly contained therein is protected from the regime in which it is installed. The cover  22  also forms a sealed volume of space in which the gear assembly is constantly lubricated. 
     It will be appreciated that the gasket  28  must be placed over the housing  14  in a proper orientation to ensure proper installation when the cover  22  is secured to the housing  14 . It will be further appreciated that misalignment of the gasket  28  may lead to improper sealing of the gasket  28 , which may manifest itself in leaks from the housing  14 . Misalignment may also cause the gasket  28  to be pinched or crimped by the fasteners  26  when the cover  22  is secured to the housing  14 . The pinched or crimped gasket  28  may also improperly seal when the cover  22  is secured to the housing  14 . 
     When the cover  22  is secured to the housing  14 , the fasteners  26  must be secured so as to apply a clamping force about the perimeter of the cover  22 . The clamping force causes the gasket  28  to compress and thus form a seal between the cover  22  and the housing  14 . The gasket  28  not only serves to retain the internal lubrication of the differential assembly  10 , but also protects the differential assembly from the regimes of driving environment, such as water, salt, and dirt. It will be appreciated that the axle of a vehicle is located along the underbelly of the vehicle and by the very nature of its location is exposed to not just water, salt, and dirt as mentioned above but may also be exposed to high-pressure water from conventional car washes. It will be appreciated that the gasket  28  must not only seal the lubrication in the differential assembly, it must also keep many things out of differential assembly, so water, dirt, salt and the like does not pollute the lubrication. 
     To that end, an incorrect amount of clamping force applied to the cover  22  may lead to improper sealing of the gasket  28 . Over-tightening the fasteners  26 , for example, may generate too much clamping force and over compress the gasket  28 , such that the gasket  28  may bulge or kink, which is sometimes referred to as coining. Coining and over-compression in general may lead to leaks especially when the gasket expands and contracts due to heating and cooling the assembly  10 . 
     It is desirable, therefore, to secure the differential assembly cover to the housing without a separate compression limiting device. It is further desirable to have the compression limiting device pre-configured into the differential assembly cover. It is also desirable to have a seal pre-attached to the differential assembly cover that is cost-effective and robust. It is additionally desirable to avoid the steps of aligning the gasket while securing the differential assembly cover to the housing. 
     SUMMARY 
     An axle assembly that includes a differential gearset in a carrier housing. A housing cover is coupled to the carrier housing and is operable for sealingly closing a window on the carrier housing through which there is access to the differential gearset. The housing cover includes a cover member and a seal ring. The cover member includes a mating face and a plurality of raised connection points that are disposed between the carrier housing and the mating face. The seal ring is coupled to the mating face and encircles each of the raised connection points. The seal ring further includes at least first and second ring members that are disposed between each of the raised connection points. The seal ring sealingly engages the carrier housing and the mating face. 
     Further areas of applicability of the present invention 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 invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description, the appended claims, and the accompanying drawings, wherein: 
         FIG. 1  is a portion of an environmental view of a prior art differential assembly showing a differential assembly cover; 
         FIG. 2  is an exploded assembly view of the differential assembly of  FIG. 1  showing the differential assembly cover, a gasket, and a differential assembly housing; 
         FIG. 3  is a differential assembly cover constructed in accordance with the various embodiments of the present invention showing a double-beaded seal and a plurality of raised connection points; 
         FIG. 4  is a cross-section of  FIG. 5 ; 
         FIG. 5  is an assembly view showing the differential assembly cover secured to the differential assembly housing and the gasket compressed therebetween; 
         FIG. 6  is another assembly view showing a shoulder bolt securing the differential assembly cover to the differential assembly housing with the gasket in a compressed state; and 
         FIG. 7  is a side view of the exemplary shoulder bolt of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the various embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     With reference to  FIG. 4 , a differential assembly cover is generally indicated by reference numeral  100 . The cover  100  has a bowl portion  102  that can be configured to surround a portion of the gear assembly  17  ( FIG. 1 ) contained in the differential assembly housing  14 , as shown in  FIG. 1 . When the cover  100  is secured to the housing  14  ( FIG. 1 ), the gear assembly  17  ( FIG. 1 ) inside is not only protected from the elements outside of the housing  14  ( FIG. 1 ) but is also sealed inside with lubrication. A modified conventional drain plug  104  can be integrated into the cover  100 . 
     A seal ring  106  encircles a perimeter  108  of the cover  100 . The perimeter  108  of the cover  100  includes a cover mating face  110 . The seal ring  106  is connected to the cover mating face  110 , which encircles the bowl portion  102 , such that when the cover  100  is attached to the housing  14  ( FIG. 1 ), at least the bowl portion  102  is sealed from the outside. 
     The seal ring  106  may include at least a first sealing member  112  and a second sealing member  114  that may be approximately concentric with the first sealing member  112 . The seal ring  106  can also include a web member (not shown) that connects the first sealing member  112  to the second member  114 . It will be appreciated that either the first sealing member  112  and/or the second sealing member  114  may be individually applied or connected to the cover mating face  110  directly or as an assembly incorporating the web member (not shown) therebetween. 
     In the various embodiments of the present invention, the sealing ring  106  is attached to the cover mating face  110  with a suitable adhesive. It will be appreciated that when the cover  100  is secured to the housing  14  ( FIG. 1 ) there is no need to align a separate gasket as the sealing ring has already been affixed to the cover mating face  110  in the proper orientation. It will be further appreciated that the sealing member can contain one sealing member or a plurality of sealing members. 
     The cover  100  also includes a plurality of raised connection points  116 . The plurality of raised connection points  116  are integral to the cover mating face  110  and define a plurality of apertures  118  within the connection points  116  spaced along the perimeter  108  of the cover  100 . In the various embodiments, there are ten (10) connection points  116  that are approximately equally spaced apart from one another. It will be appreciated, that while ten (10) connection points  116  are depicted in  FIG. 3 , more or less connection points  116  can be used as size, geometry, and sealing requirements change in a given application. 
     The seal ring  106  encircles each connection point  116  so that a continuous seal is formed around the bowl portion  102  of the cover  100 . It will be appreciated that the raised connection point  116  is at a different elevation than a portion of the cover mating face  110  adjacent to the raised connection point  116 , as shown in  FIGS. 4 and 5 . To that end, the seal ring  106  encircles each connection point  116  but the sealing ring  106  is otherwise mounted to the cover mating face  110  at a lower elevation when compared to the elevation of the connection point  116 . In the various embodiments, the distance in the elevation between each of the raised connection points  116  and an end  106   a  of the seal ring  106  opposite face  110  is referred to as the compression distance. 
     In the various embodiments, the cover  100  can be stamped as one piece. The stamping process creates, among other things, the bowl portion  102 , the raised connection points  106 , and the cover mating face  110  along with the general geometry of the bowl. Moreover, the sealing ring  106  can be affixed to the cover  100  during the stamping process, so that the cover  100  and the seal ring  106  can be produced as a single unit. This can not only eliminate the need to match the cover  100  to the gasket  28  ( FIG. 2 ), this can also reduce production time, part cost and inventory control issues. 
     With reference to  FIG. 4 , a portion of the cross-section of the cover  100  is shown with the seal ring  106  encircling the raised connection point  116 . A segment of the bowl portion  102  connects with the cover mating face  110 . Each of the apertures  118  is formed within each of the raised connection points  116 . It will be appreciated that the seal ring  106  is shown in an uncompressed state in  FIG. 4 , and in a compressed state in  FIG. 5 . 
     With reference to  FIG. 5 , a fastener  122  is shown having a head  124  and a threaded shank  126  that is at least partially inserted within a threaded aperture  128 . A plurality of fasteners  122  secure the cover  100  to a housing mounting face  130  of a housing  132 . It will be appreciated that the raised connection point  116  makes direct contact with the housing mounting face  130  and by virtue of the geometry of the cover  100 , the seal ring  106  is compressed to a desired distance. In the various embodiments, the desired distance to compress the seal ring  106  between the cover mating face  110  and the housing mounting face  130  may be the compression distance. 
     In the various embodiments, the housing  132  can be a salisbury differential housing, wherein the cover  100  is a modified housing cover configured to secure to a salisbury differential housing. The cover  100  may also be modified to seal to an axle assembly configured with independent suspension or to various transaxles. Moreover, the cover  100  can also be used in other areas of the vehicle beyond its use on front or rear axles. 
     The cover  100  is placed over the housing  132  and secured to the housing with the plurality of fasteners  122 . It will be appreciated that when the apertures  118  of the connection points  116  are aligned with the housing mounting face  130 , the seal ring  106  is necessarily aligned properly to the housing  132 . The plurality of fasteners  122  are then used to secure the cover  100  to the housing  132 . When the fasteners  122  are secured, the configuration of the cover  100  is such that the seal ring  106  is properly compressed between the cover mating face  110  and the housing mounting face  130 . As such, the seal ring  106  can be compressed by an amount equal to the compression distance between the cover mating face  110  and the housing mounting face  130 , while the connection points  116  make direct contact with the housing mounting face  130 . 
     It will be appreciated that a proper seal between the housing cover  100  and the differential housing  132  is required to not only contain lubrication within the differential housing  132  but also keep out the many pollutants to which the exterior of the differential housing is exposed. Some of the pollutants, for example, include water, salt spray, dirt, oil, and the like. Moreover, axle assemblies are commonly exposed to high-pressure wash systems or driven through water both of which can add to the need to have a robust seal between the housing cover  100  and differential housing  132 . 
     Other devices can be employed to address compression of the seal ring  106  a proper distance or put another way to limit compression. Any such device must not only be robust, easy to use, and compliant with other materials, it must also be cost effective in a mass production scale.  FIG. 6  depicts a portion of the cover  100  using a shoulder bolt, which is generally indicated by reference numeral  134 . The shoulder bolt  134  has a head  136  from which a shank  138  extends. The shank  138  has a threaded-portion  140  and a non-threaded-portion  142 , which is located between the threaded portion  140  and the head  136 . The length of the shank  138  includes a length of the threaded-portion  140  and a length of the non-threaded-portion  142 , which are indicated by reference numerals  144  and  146 , respectively, a shown in  FIG. 7 . It will be appreciated that the threaded portion  140  has a smaller diameter than the non-threaded portion  142 , such that the end of the non-threaded portion  142 , adjacent to the threaded portion  140 , generally forms a shoulder  142   a.    
     The shoulder bolt  134  can be inserted into a threaded aperture  148  or a conventional nut. It will be appreciated that the shoulder bolt  134  can only be inserted a distance  144  into the threaded aperture  148 . As shown in  FIG. 6 , the shoulder bolt  134  is inserted through the differential assembly cover  100  and the housing  132 . The shoulder bolt  134  is then secured into the threaded aperture  148 . It will be appreciated that the shoulder bolt  134  compresses the cover  100  against the housing  132  enough to properly clamps the seal ring  106  therebetween. As such, the shoulder bolt  134  limits the compression of the seal ring  106  as the shoulder bolt  134  can only be inserted the distance  144  into the threaded aperture  148 . 
     In lieu of the shoulder bolt  134 , a compression limiter (not shown) may be introduced between the cover  100  and the housing  132  to establish a proper compression distance for the seal ring  106 . In various embodiments, a compression limiter may take the form of a sleeve (not shown) over a conventional fastener, which may be used to limit the insertion of the fastener. While introducing compression limiters may be a less expensive option than using shoulder bolts, compression limiters add to the overall parts count of the assembly and can increase the overall cost of the process. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.