Patent Publication Number: US-2017356536-A1

Title: Lightweight and narrow differential assembly with powder metal inserts

Description:
RELATED APPLICATIONS 
     The present application claims the benefit to U.S. Provisional Application No. 62/348,043 filed on Jun. 9, 2016, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present disclosure relates to an axle assembly and means of torque conveyance. Axle assemblies in wheeled vehicle drivetrains are known to employ a differential apparatus to transmit torque from a power source to the vehicle wheels. The differential apparatus also permits an outer drive wheel to rotate at a greater velocity than an inner drive wheel when operating a vehicle through a turn. 
     Conventional axle assemblies are large and heavy. The present subject matter discloses an axle assembly and differential apparatus with greater torque capacity in a lighter weight and smaller packaging. 
     SUMMARY 
     The present disclosure provides for an axle assembly comprising a differential carrier including an upper portion coupled with a lower portion, the upper portion comprising a planar surface defining a first hollow protrusion and a second hollow protrusion. The first hollow protrusion and the second hollow protrusion each define an arcuate cavity. An input shaft is coupled with a pinion gear drivingly engaged with a ring gear at least partially disposed within the first hollow protrusion. A differential case having a first portion and a second portion is at least partially disposed in the second hollow protrusion. The ring gear is welded to an exterior surface of said differential case first portion. A plurality of axially extending slots are defined by an interior surface of the differential case first portion. An annular canister having radially extending lugs disposed on an outer surface thereof, is disposed within said differential case. The lugs are in driving engagement with the plurality of differential case slots. A plurality of apertures are radially disposed through the canister, and a plurality of pinion shafts are disposed through and drivingly engaged with the canister apertures. A pinion gear is disposed on each of the pinion shafts. A pair of side gears is in driving engagement with the pinion gears. A first output shaft is in driving engagement with one of the pair of side gears, and a second output shaft is in driving engagement with the other of the pair of side gears. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The accompanying drawings are incorporated herein as part of the specification. The drawings described herein illustrate embodiments of the presently disclosed subject matter, and are illustrative of selected principles and teachings of the present disclosure and do not illustrate all possible implementations thereof. The drawings are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a perspective view of an axle assembly according to an embodiment of the presently disclosed subject matter; 
         FIG. 2  is a perspective view of a portion of the axle assembly according to  FIG. 1 ; 
         FIG. 3  is another perspective view of the portion of the axle assembly according to  FIG. 2 ; 
         FIG. 4  is a perspective of a portion of the axle assembly according to  FIG. 1 ; 
         FIG. 5  is a cross-sectional view of a portion of the axle assembly according to  FIG. 1 ; 
         FIG. 6  is a perspective view of the differential apparatus of the axle assembly according to  FIG. 1 ; and 
         FIG. 7  is a cross-sectional view of the differential apparatus according to  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices, assemblies, systems and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined herein. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless expressly stated otherwise. Also, although they may not be, like elements in various embodiments described herein may be commonly referred to with like reference numerals within this section of the application. 
     An axle assembly  10  may be provided for use in a drive train. As illustrated in  FIG. 1 , the axle assembly  10  comprises a lower carrier housing  12 A and an upper carrier housing  12 B. In an embodiment, the lower carrier housing  12 A and the upper carrier housing  12 B are coupled together via a plurality of fasteners  14 . The upper carrier housing  12 B comprises a substantially flat portion  16  through which fastener apertures  18  are disposed. The fasteners  14  are located at least partially through the apertures  18  and into corresponding bores (not depicted) in the lower carrier housing  12 A. 
     As illustrated in  FIGS. 1-3 , the upper carrier housing  12 B also comprises a first hollow protrusion  22  and a second hollow protrusion  24 , each extending transverse the flat portion  16 . The first hollow protrusion  22  and the second hollow protrusion  24  may each comprise a substantially arcuate geometry. Further, the first hollow protrusion  22  and second hollow protrusion  24  may comprise a stepped, unitary hollow protrusion. The first hollow protrusion  22  accommodates a ring gear  104 , of which a portion is located above the upper surface of the flat portion  16  such that a portion of the ring gear  104  is disposed in the first hollow protrusion  22 . The second hollow protrusion  24  accommodates a differential case  105 , of which a portion is also located above the upper surface of the flat portion  16  such that a portion of the differential case  105  is located in the second hollow protrusion  24 . In an embodiment, the first and second hollow protrusions  22 ,  24  may comprise other shapes that allow portions of the ring gear  104  and differential case  105  to be disposed therein. 
     To reduce the size and weight of the axle assembly  10 , as compared to conventional differential assemblies, the differential carrier housing  12 A,  12 B is narrow in the transverse axis (i.e., crosswise) direction parallel with the longitudinal axis of the axle assembly  10 . 
     The upper carrier housing  12 B may comprise a metallic material such as, but not limited to, steel, premium carbon steel, aluminum, and aluminum alloys. In addition, the upper carrier housing  12 B may be formed by a process of single-stage or multi-stage stamping or pressing. During maintenance of the axle assembly  10 , or installation/removal of a differential case assembly  100 , the upper carrier housing  12 A is separated from the lower carrier housing  12 B by at least partially removing the fasteners  14 . 
     As illustrated in  FIGS. 4-5 , a pinion gear  102  is located in the carrier housing  12 A,  12 B to convey torque from a drive power source (not depicted) to the ring gear  104 . The ring gear  104  is coupled with the differential case  105  of the differential case assembly  100 , and the case  105  is rotated with the ring gear  104  when driven by the pinion gear  102 . In an embodiment, the ring gear  104  may comprise a webbed gear. In an embodiment, the ring gear  104  is coupled with the case  105  via laser welding. The interface between the ring gear  104  and the case  105  may comprise an axial or radial gap which allows for an axial or radial welding process to be utilized. 
     The differential case  105  is mounted for rotation within the differential carrier housing  12 A,  12 B via bearings  150 ,  155 . The bearings  150 ,  155  are disposed about a trunnion, or cylindrical protrusion, on opposing portions of the differential case  105  to support the differential case  105  inside the differential carrier housing  12 A,  12 B. In an embodiment, the differential case  105  may be produced via the process of flow forming a metallic material such as, but not limited to, steel, premium carbon steel, aluminum, and aluminum alloys. 
     As illustrated in  FIGS. 4-7 , in an embodiment, the differential case  105  comprises a first portion  105 A and a second portion  105 B. The first and second portions  105 A and  105 B may be welded together utilizing a laser welding process. The differential case  105  further comprises a hollow interior defined by an interior surface  110 . The differential case assembly  100  may be a four-pin differential having a canister  160 . The canister  160  may comprise an annular member having a plurality of axially extending lugs  162  disposed on an exterior surface thereof. The lugs  162  may mate with grooves  164  provided on the interior surface of the differential case  105  to align the canister  160  when in the differential case assembly  100 . In an embodiment, the canister  160  may further comprise four equally spaced apertures  118  through exterior surface and interior surface thereof for receiving pinion gear shafts (i.e., spider shafts). In another embodiment, the apertures  118  are not equally spaced. 
     Further, in an embodiment as illustrated in  FIG. 7 , the canister  160  may comprise a first portion  160 A and a second portion  160 B. The first and second canister portions  160 A,  160 B may comprise annular members having external lugs  162  which are aligned. The interior of the canister  160  comprises an arcuate geometry defining a portion of a substantially spherical shape to accommodate a plurality of pinion gears  120 A,  120 B,  120 C,  120 D disposed therein. 
     In addition, the canister  160  may be formed at least in part by a process of powder metallurgy or sintering to allow the transfer of high torque and high revolutions per minute. It will be apparent to those skilled in the pertinent arts that the canister  160  may also be produced utilizing conventional manufacturing processes. 
     In an embodiment, a first spider shaft  115 A extends through the canister  160  and is coupled at its ends in two opposing apertures  118  of the canister  160 . A first and second pinion gear  120 A,  120 B, are mounted on each end of the first spider shaft  115 A inside the canister  160 . A second spider shaft  1156  extends into the canister  160  transverse the first spider shaft  115 A and is coupled at a first end in another aperture  118  of the canister  160 . A second end of the second spider shaft  1156  may be disposed in an aperture (not depicted) in the first spider shaft  115 A. A third pinion gear  120 C is mounted on the spider shaft  1156  inside the canister  160 . A third spider shaft  115 C extends into the canister  160  opposite the second spider shaft  1156  and is coupled at a first end in an aperture  118  of the canister  160 . A second end of the third spider shaft  115 C may be disposed in an aperture (not depicted) in the first spider shaft  115 A. A fourth pinion gear  120 C is mounted on the third spider shaft  115 C inside the canister  160 . The assembly of the first spider shaft  115 A, the second spider shaft  1156 , the third spider shaft  115 C, and the pinion gears  120 A,  120 B,  120 C,  120 D comprises a pinion gear assembly  116 . 
     In another embodiment, not depicted, a first spider shaft  115 A extends into the canister  160  transverse a longitudinal axis of the canister  160  and is coupled at a first end in an aperture of the canister  160 . A first pinion gear  120 A is mounted on a second end of the spider shaft  115 A inside the canister  160 . A second spider shaft  1156  extends into the canister  160  opposite the first spider shaft  115 A and is coupled at a first end in another aperture of the canister  160 . A second pinion gear  120 B is mounted on a second end of the spider shaft  1156  inside the canister  160 . A third spider shaft  115 C extends into the canister  160  transverse the first and second spider shafts  115 A,  1156  and is coupled at a first end in another aperture of the canister  160 . A third pinion gear  120 C is mounted on a second end of the spider shaft  115 C inside the canister  160 . A fourth spider shaft  115 D extends into the canister  160  opposite the third spider shaft  115 C, and transverse the first and second spider shaft  115 A,  115 B, and is coupled at a first end in another aperture of the canister  160 . A fourth pinion gear  120 D is mounted on a second end of the spider shaft  115 D inside the canister  160 . 
     In another embodiment, not depicted, the pinion gears  120 A,  120 B,  120 C,  120 D are supported in the canister  160  by a unitary cross pin  115 . The cross pin  115  may comprise shafts  115 A,  115 B,  115 C,  115 D extending radially such that an end of each shaft supports one of the pinion gears  120 A,  120 B,  120 C,  120 D and is disposed through a canister  160  aperture. 
     The pinion gears  120 A,  120 B,  120 C,  120 D are meshed with a first side gear  130  and a second side gear  135  within the differential case  105 . The side gears  130 ,  135  comprise internal splines to engage axle half shafts (not depicted) or stub shafts (not depicted). The differential case  105  comprises bores  140  and  145  through the differential case  105  trunnions to accommodate the half shafts or stub shafts coupled with the side gears  130 ,  135 . The axle half shafts or stub shafts are inserted into the bores  140 ,  145  and into the side gears  130 ,  135  where they engage the side gear  130 , 135  internal spline portions. In an embodiment, the axle half shafts or stub shafts are secured in their position in the differential case assembly  100  by c-clips (not depicted) inserted into grooves in the axle half shafts. 
     The differentical case assembly  100  may be assembled by sliding the ring gear  104  onto the exterior surface of the second case portion  1056  such that a portion of the ring gear  104  abuts second case portion  1056  flange  106 . The ring gear  104  is then laser welded to the second case portion  1056  where the ring gear  104  abuts the flange  106 . The second side gear  135  may then be located inside the second case portion  1056  such that its gear teeth substantially face the center of the differential case  105 . The second canister portion  160 B may then be slid into engagement with the corresponding interior grooves in the second case portion  105 B, such that the second canister portion  160 B is in the preferred alignment with its arcuate interior facing the center of the differential case  105 . The pinion gear assembly  116  having the pinion gears  120 A,  120 B,  120 C,  120 D located on the shafts  115 A,  115 B,  115 C, may then be located in the second canister portion  1606 . The shafts  115 A,  1156 ,  115 C are disposed in the half apertures defined by the second canister portion  160 B. In the embodiment comprising the first and second canister portions  160 A,  160 B, the first canister portion  160 A may then be installed in the second case portion  105 B. The first and second canister portions  160 A,  160 B define half apertures comprising the apertures  118  of the canister  160 . The half apertures align with the shafts  115 A,  1156 ,  115 C and create the plurality of apertures  118  through the canister  160 . The first side gear  130  may then be placed into engagement with the pinion gear assembly  116  inside the second case portion  1056 . Next, the first case portion  105 A may be coupled with the second case portion  1056  such that an outer surface  108  of the first case portion  105 A abuts an interior surface of the second case portion  105 B. The first case portion  105 A comprises an annular portion creating a flange which abuts the first canister portion  160 A. The first case portion  105 A may be laser welded to the second case portion  105 B. 
     While various embodiments have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant art that the disclosed subject matter may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments described above are therefore to be considered in all respects as illustrative, not restrictive.