Clam-shell shaped differential housing and lubrication system therefor

A clam-shell shaped differential housing including a lower portion for receiving the input shaft and the differential gearing, and an upper portion for enclosing the same within the differential housing. The clam-shell shaped differential housing allows for easy insertion and adjustment of the differential components. In addition, a lubricant reservoir may be formed in the area of the input shaft and pinion bearings to retain the majority of differential lubricant. The clam-shell shaped housing allows a pump to be easily positioned in the reservoir between the inner and outer pinion bearings to pump the lubricant from the reservoir to the differential components through channels formed in the housing. In this manner, the sump of the differential housing remains substantially dry. The pump may also be used to provide hydraulic pressure to a limited slip clutch assembly for the actuation thereof in conjunction with a valve control assembly.

FIELD OF THE INVENTION 
The present invention relates generally to a housing for a differential of 
an automobile or other vehicle, and more specifically to a clam-shell 
shaped differential housing that provides for easy assembly of and access 
to the various differential components, particularly the pinion bearings, 
and also provides the ability to install an improved lubrication system in 
a differential. 
BACKGROUND OF THE INVENTION 
Axle assemblies are well known structures which are commonly used in most 
vehicles. Such axle assemblies include a number of components which are 
adapted to transmit rotational power from an engine of the vehicle to the 
drive wheels thereof. Typically, an axle assembly includes a differential 
gear assembly which is rotatably supported in a non-rotating carrier. The 
differential is connected between an input drive shaft extending from the 
vehicle engine and a pair of output drive shafts or axles extending to the 
vehicle drive wheels. The axle shafts are ordinarily contained within 
non-rotating tubes which are secured at their inner ends to the 
differential carrier. Thus, rotation of the differential by the drive 
shaft causes corresponding rotation of the axle shafts. The differential 
carrier and the axle tubes extending therefrom form a housing for these 
drive train components of the axle assembly, inasmuch as the differential 
and axle shafts are supported for rotation therein. 
Differential carriers have heretofore been provided in two main 
configurations --the unitized carrier construction, commonly referred to 
as a Salisbury or Spicer axle assembly, and the separable carrier 
construction, commonly referred to as the banjo-type carrier assembly. The 
unitized differential carrier is directly connected to the axle tubes, and 
includes an access opening in the rear portion (opposite the input drive 
shaft) for the insertion of the differential gearing and other components. 
This access opening is closed with a cover after the differential 
components have been assembled within the carrier. With respect to the 
banjo-type differential carrier, the axle tubes are connected together by 
a central member which is separate from the carrier. The central member 
has an opening formed therethrough, usually generally circular in shape. 
To assemble the axle, the differential components are assembled within the 
differential carrier, and the carrier is then secured in the opening 
formed in the central member. A cover is also provided to seal the 
differential components within the central opening. With both types of 
differential carriers, once the differential components are assembled 
therein, the carrier is partially filled with a quantity of lubricating 
oil. The unitized differential carrier provides a low cost arrangement 
that is readily adaptable to a wide variety of vehicles, while the 
banjo-type differential carrier allows the carrier and differential 
components to be removed from the vehicle without disturbing the axle 
tubes and associated vehicle components. 
While known differential housings are generally acceptable, there are 
certain drawbacks associated with each variety. For example, there has 
been found a need to provide a differential housing design that is light 
weight, yet sufficiently rigid. Also, known differential housings 
generally provide only very limited access to the differential components 
contained therein. Assembly and adjustment of the differential components, 
especially the "pinion" bearings rotatably supporting the input shaft to 
the differential, is complicated by these known designs wherein the only 
access to the differential components is provided by the access opening 
and cover opposite the input shaft. 
Also, it has been found that known arrangements wherein the differential 
housing is partially filled with a large quantity of lubricating oil to 
form a "sump" actually lead to an increased amount of heat being trapped 
within the differential housing by the oil. Furthermore, the constant 
rotation of the differential components within the quantity of oil cause 
the oil to become aerated, resulting in a loss of lubricating ability. 
Another drawback associated with known differential housing designs is 
that the rear cover, which is bolted to the differential housing along 
with a gasket, forms a seam with the differential housing that may leak 
over time. 
As mentioned, current designs for differential housings limit one's access 
to the torque input shaft of the differential, the drive pinion secured to 
the innermost end of the input shaft, and the pinion bearings that support 
the input shaft for rotation relative to the housing (generally an inner 
and outer roller bearing assembly). This limited access makes it difficult 
to position the various components, and makes the subsequent adjustment 
thereof difficult as well. Current designs also limit the types of pinion 
bearings that may be utilized to support the input shaft. For example, the 
limited access in the area of the pinion bearings does not allow for the 
use of bearing caps which are a convenient arrangement for providing the 
pinion bearing assemblies. 
In certain applications, it is necessary that the lubricating fluid found 
within the differential housing be pumped to locations within the 
differential housing where it may not naturally flow, or the fluid may be 
pumped to remote locations for use in lubricating various components, or 
as a hydraulic fluid to actuate pistons and the like. For example, 
lubricating fluid may be pumped from the differential housing, through the 
axle tubes, to the wheel end assemblies for use in wet brakes. A gerotor 
pump has been used in conjunction with the rotating input shaft to create 
the necessary hydraulic pressure. In one arrangement, the gerotor pump is 
secured about the input shaft exterior to the differential carrier at the 
point where the input shaft enters the differential housing. Suction lines 
are provided from the pump to the "sump" area of the differential housing. 
However, it has heretofore been difficult and impracticable to locate the 
gerotor pump on the input shaft, between the inner and outer pinion 
bearings. As is described hereinbelow, such a placement of the gerotor 
pump eliminates the need for suction lines to a sump, and eliminates the 
need to maintain a large quantity of lubricating fluid within the sump. 
Locating the gerotor pump within the differential housing also allows the 
differential to be more compact. 
SUMMARY OF THE INVENTION 
The present invention is therefore directed to a clam-shell shaped 
differential housing comprising a lower portion for receiving differential 
components, and an upper portion for enclosing the differential components 
within the differential housing. The lower portion of the housing 
comprises an upwardly open central section for rotatably receiving and 
supporting the differential case and associated components and first and 
second trunnions extending therefrom for receiving axle shaft housing 
tubes. The lower portion also includes an upwardly open input shaft 
support region for receiving and rotatably supporting an input shaft and 
the associated pinion gear coupled to rotate therewith. The upper portion 
of the differential housing is provided to seal the lower portion such 
that when in position, a differential gearing chamber is defined within 
the differential housing. In a preferred embodiment, the differential 
housing includes a reservoir formed in the region of the input shaft and a 
gerotor pump is provided about the input shaft to be driven thereby. The 
gerotor pump is used to pump the lubricating fluid to the various 
differential components, such that it the overall amount of lubricant 
maintained in the differential housing can be substantially reduced. Also, 
the gerotor pump may be utilized to provide hydraulic pressure to a clutch 
assembly of a limited slip differential. 
The present invention provides the advantage of an easy to assemble 
differential that is strong and lightweight, and that allows for the 
simple addition of a reservoir and pump in association with the input 
shaft so that the amount of lubricating fluid in the differential can be 
reduced without reducing the amount of lubricating fluid flowing to the 
various differential components.

DETAILED DESCRIPTION OF THE INVENTION 
A clam-shell shaped differential housing in accordance with the present 
invention is shown generally at 10 in FIGS. 1-3 and comprises a lower 
portion 12 into which the differential components are placed (as shown in 
FIG. 2) and an upper or cover portion 14 to mate with the lower portion 12 
so that the differential gearing components 40 are encased within housing 
10. Upper portion 14 is bolted or otherwise secured to lower portion 12 
such that a seam 16 is formed therebetween. The connection of upper 
portion 14 to lower portion 12 in this manner creates a generally hollow 
differential gearing chamber 20 within housing 10. It can be seen that the 
manner in which the lower and upper portions 12, 14 of the differential 
housing 10 are joined together is similar to the two halves of a clam 
shell, and thus, the differential housing 10 is referred to herein as a 
clam-shell shaped differential housing. Differential housing 10 also 
includes trunnions 18a, 18b extending from opposing lateral sides thereof 
to respectively receive axle tubes 19 (only one shown) to house the axle 
shafts 41a, 41b as discussed above. 
The clam-shell like structure of housing 10 provides a wide variety of 
advantages over differential housings heretofore known. For example, the 
clam-shell shaped housing disclosed herein is thought to be more rigid and 
strong than known differential housings, which allows for the use of less 
dense or "lighter" alloys in the construction thereof. One of the most 
significant advantages is that with the upper portion 14 removed from 
lower portion 12 as is shown in FIG. 2, the placement of the differential 
gearing and associated components 40 into the differential housing 10 is 
greatly simplified. The components 40 may simply be laid into the lower 
portion 12, which, when upper portion 14 is removed therefrom, comprises a 
upwardly open hollow central portion 22 into which the differential 
components, such as a differential case 42 may be received and supported 
for rotation. Lower portion 12 also includes an upwardly open input shaft 
support region 26 into which an input shaft 52 and its associated 
components (as explained in detail below) may be easily laid when upper 
portion 14 is removed from lower portion 12. 
In addition to the differential case 42 rotatably supported within the 
differential housing 10 by bearing assemblies 44a, 44b, the differential 
components 40 include a differential case driving gear such as ring or 
face gear 45 connected to rotate with differential case 42 through an 
annular flange 43 extending from case 42 with the use of bolts 46 or the 
like. Gear 45 is in meshing engagement with a pinion gear 50 which is 
coupled to rotate with input shaft 52 on the innermost end thereof. Shaft 
52 is supported for rotation relative to housing 10 by inner and outer 
bearing assemblies 54a, 54b, commonly referred to inner and outer pinion 
bearing assemblies, respectively. 
Referring now primarily to FIG. 2, it can be seen that input shaft 52 
includes a yoke 54 secured to rotate with shaft 52 through the use of a 
nut 55. Yoke 54 is effective for receiving torque from a driving member 
(not shown) of the motor vehicle of which differential 10 is a part. As is 
generally known in the art, differential gearing 40 and the associated 
components described herein are effective for transferring torque from 
input shaft 52 to first and second output or axle shafts 41a, 41b which 
are in turn drivingly coupled to the road wheels (not shown) of the motor 
vehicle. Torque is transferred to output shafts 41a, 41b via differential 
gearing 40 in a conventional manner so as to permit differential rotation 
between shafts 41a, 41b. The centerline axis A about which differential 
case 42 rotates is coincident with the longitudinal centerline axis B 
about which the first and second output shafts 41a, 41b rotate. When 
torque is transmitted to input shaft 52 through yoke 54, rotation of 
pinion 50 causes rotation of gear 45, which in turn causes rotation of 
differential case 42 within differential housing 10. The differential case 
42 includes at least one cross shaft or pin 60 having opposing ends 
positioned in bores formed in the rotatable case 42 Shaft 60 is retained 
in case 42 by a locking pin 62. 
The differential gearing 40 further comprises a pair of pinion gears 64 
(commonly referred to as pinion mates) rotatably supported on each end of 
cross shaft 60, and a pair of side gears 66a, 66b, preferably provided in 
the form of bevel gears, respectively coupled to rotate with output shafts 
41a, 41b. Each side gear 66a, 66b is meshingly engaged with the pinion 
mates 62. Accordingly, rotation of case 42 about axis A in response to the 
transmission of torque to input shaft 52 results in rotation of at least 
one of the output shafts 41a, 41b. The interrelationship among pinion 
gears 64, side gears 66a, 66b, and output shafts 41a, 41b, permits 
differential, or relative, rotation to exist between output shafts 41a, 
41b which is required during certain vehicle operations such as cornering. 
It can be seen that differential 10, in accordance with the present 
invention, preferably includes a fluid retaining region or reservoir 70 
formed therein throughout the input shaft support region 26 such that the 
majority of lubricating fluid within differential housing 10 is retained 
in reservoir 70. Reservoir 70 is upwardly open and defined by sidewalls 
72, floor 71, and input shaft support region 26 of differential housing 
10. In this manner, gear 45, differential case 42, pinion gears 62, side 
gears 66a, 66b and other differential components located in central 
section 22 of differential housing 10 are not submerged in a large 
quantity of lubricating fluid (with the associated drawbacks as discussed 
above). Instead, a pump, such as a gerotor pump 80 is provided in fluid 
communication with reservoir 70, preferably at least partially submerged 
therein to pump lubricating fluid from reservoir 70 through channels (not 
shown) formed in housing 10 and/or other conduits, to the various 
differential components in need of lubrication. Pump 80 is driven by input 
shaft 52 and therefore, lubricating fluid is pumped any time input shaft 
52 is rotated. As is shown in FIG. 3, those skilled in the art will 
recognize that as lubrication fluid is pumped throughout the differential 
housing 10, it will drain into the sump region 23 of housing 10. As a 
sufficient quantity of lubricating fluid collects in the sump region to 
contact gear 45, the teeth (not shown) of gear 45 will collect the 
lubricating fluid and carry the same upward until it is "spun" off of the 
gear 45 into the upwardly open reservoir 70. In addition to the advantages 
of this "dry sump" system discussed above, it can be seen that the gear 45 
is not required to stir a large amount of lubricating fluid, and that the 
reservoir allows the air bubbles to exit the fluid before it is once again 
pumped throughout the housing 10. 
Another advantage associated with clam-shell shaped differential housing 10 
is that the upwardly open input shaft support region 26 of lower portion 
12 allows for the easy installation into region 26 of the input shaft 52, 
the inner and outer pinion bearings 54a, 54b, and the gerotor pump 80 in a 
manner similar to that discussed above with respect to the insertion of 
differential case 42 into region 22. Also, the engagement between pinion 
gear 50 and gear 45 is easily adjusted. Finally, as is shown in FIG. 3, 
the upwardly open input shaft support region allows the inner and outer 
pinion bearings 54a, 54b to be provided in the nature of two-part bearing 
assemblies, respectively having lower portions 55a, 55b onto which the 
input shaft is laid, and upper portions 56a, 56b, commonly referred to as 
bearing caps, that are simply bolted to lower portions 55a, 55b, 
respectively, once the position of input shaft 52 within housing 10 has 
been adjusted as desired. The enclosed nature of known differential 
housings in the area of the input shaft and associated bearings makes the 
use of these bearing caps difficult and impracticable. Also, the 
installation of the gerotor pump 80 is much simplified by the open nature 
of the input shaft support region 26 of lower portion 12 of housing 10. 
Once the components are positioned as desired, the required amount of 
lubricating fluid is poured into housing 10, and upper portion 14 is 
connected to lower portion as described above. A suitable gasket or 
sealing compound is preferably located at the seam 16 between the upper 
and lower portions 12, 14 of housing 10. However, the present housing has 
much less of a tendency to leak lubricating fluid due to the fact that, 
unlike known differential housings, the entire seam 16 is above the level 
of the lubricating fluid. 
Referring now to FIG. 4, there can be seen a schematic representation of a 
lubrication/hydraulic system in accordance with the present invention. The 
formation of reservoir 70 as described above, allows for the simple and 
easy installation of lubrication system 90 within differential housing 10. 
Specifically, pump 80 is in fluid communication with reservoir 70 
(preferably by being at least partially submerged therein), and a filter 
92 is provided between pump 80 and reservoir 70 to filter metal shavings, 
dirt, and other contaminants from the lubrication fluid. A pressure 
regulator valve 100 is positioned in fluid communication with outlet 82 of 
pump 80 and reservoir 70 such that, upon the occurrence of excessive 
hydraulic pressure in the lubrication system 90, lubrication fluid is 
pumped from outlet 82 of pump 80 back to reservoir 70 such that the 
excessive system pressure is relieved. As shown herein, pressure relief 
valve 100 is normally closed under the force of spring 102. However, when 
excessive hydraulic pressure develops at pump outlet 82 (and consequently 
at regulator 100), spring 102 becomes compressed under fluid pressure, and 
component 104 of regulator 100 becomes aligned with inlet and outlet 105, 
106 of regulator 100 such that fluid communication is allowed from pump 
outlet 82 to reservoir 70 through regulator 100. 
As discussed above, upon rotation of input shaft 52, pump 80 pumps 
lubrication fluid from reservoir 70 to various regions and components 
within differential housing 10 as required. Specifically, outlet 82 of 
pump 80 is in fluid communication with pinion gear 50 through valve 
assembly 110 and conduit 111, such that pressurized lubrication fluid is 
directed onto pinion gear 50. Outlet 82 of pump 80 is also in fluid 
communication with bearings 44a, 44b and other differential components as 
described through conduit 112. As described above, the conduits shown in 
FIG. 4 may simply be channels formed in differential housing 10. 
Lubrication of the bearings 44a, 44b pinion gear 50, and other components 
with lubricant supplied under pressure from outlet 82 of pump 80 is 
superior to known differential lubrication systems wherein these 
components are merely "splash" lubricated. 
In an alternate embodiment, differential housing 10 also includes therein 
the required components to act as a limited slip differential as is well 
known in the art. In such an alternative embodiment, lubrication system 90 
may also function as a hydraulic actuation system for the limited slip 
clutch assembly, with the lubrication fluid acting as the hydraulic fluid. 
Because pump 80 pumps anytime input shaft 52 rotates, a limited slip 
clutch actuation valve control assembly 120 is provided to selectively 
block/unblock fluid communication of lubricating fluid from outlet 82 of 
pump 80 to the piston assembly (not shown) of the limited slip clutch 
assembly (not shown). As is generally known in the art of limited slip 
differentials, when one road wheel of the vehicle spins or 
"differentiates," the limited slip clutch assembly becomes actuated to 
thereby lock the differential gearing components, thus causing both road 
wheels to rotate at the same speed. Valve control assembly 120 is normally 
closed (as indicated at 122) to allow differentiation between the vehicle 
road wheels as is required during normal vehicle operations. However, upon 
the occurrence of excessive differentiation, as might occur when one or 
both road wheels are presented with ice or another surface having a low 
coefficient of friction, valve control assembly 120 allows the hydraulic 
lubrication fluid to flow under pressure to the piston assembly of the 
limited slip clutch assembly such that the clutch assembly is actuated. 
Those skilled in the art will recognize that the foregoing description has 
set forth the preferred embodiment of the invention in particular detail 
and it must be understood that numerous modifications, substitutions and 
changes can be undertaken without departing from the true spirit and scope 
of the present invention as defined by the ensuing claims.