Abstract:
An axle assembly and method of reworking an axle assembly. The axle assembly has an axle housing and a differential carrier assembly. A central portion of the axle housing has an opening that is defined by an axle flange that has a first mating surface. The differential carrier assembly has a differential mounted on a carrier. The carrier has a carrier flange that has a second mating surface. The first mating surface is sealed to the second mating surface by seal. At least one of the first and second mating surfaces includes a groove.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an axle assembly, in particular an axle assembly for a heavy vehicle such as a lorry or truck. 
       BACKGROUND 
       [0002]    Road vehicles are known which include driven rear axles. The rear axles include a crown wheel and pinion and differential. The pinion is driven via a drive shaft or the like connected to a prime mover such as an engine. The pinion and drive shaft rotate about a longitudinal axis of the vehicle. The pinion together with the crown wheel enables the crown wheel to rotate about an axis which is laterally orientated relative to the vehicle. The crown wheel drives a differential mechanism which drives a right and left hand drive shaft (known as half shafts). The right hand drive shaft drives a right hand wheel rotatably mounted to the axle and the left hand drive shaft drives a left hand wheel rotatably mounted to the axle. In this way the vehicle can be driven over the ground. 
         [0003]    The crown wheel, pinion and differential assembly require lubrication and cooling and a fluid, typically an oil, will perform this dual function. The crown wheel, pinion and differential assembly are mounted on a differential carrier assembly that is fixed to the axle housing by bolts. When the vehicle is driven, the axle housing and the differential carrier assembly experience vertical, longitudinal and torsional forces, which cause deformation of the axle housing and the differential carrier assembly. This causes leakage of the fluid from the resulting gaps between the differential carrier assembly and the axle housing. 
         [0004]    It is known to include gaskets or sealants between the differential carrier assembly and the axle housing in order to prevent leakage, however leakage of fluid still occurs. This is a particular problem for lightweight axle housings, for which the reduced weight results in greater deformation. 
         [0005]    The leakage of fluid from the axle housing results in high warranty costs and so an axle assembly with improved resistance to vertical, longitudinal and torsional forces is required. 
       SUMMARY 
       [0006]    Thus according to the present invention there is provided an axle assembly including an axle housing having a central portion for receiving a differential, a first axle tube extending from the central portion, and a second axle tube extending from the central portion, the central portion having an opening defined by an axle flange, the axle flange having a first mating surface. The axle assembly further includes a differential carrier assembly having a differential mounted on a carrier, the carrier having a carrier flange which has a second mating surface. The first mating surface is sealed to the second sealing surface by seal. At least one of the first and/or second mating surfaces includes a groove. 
         [0007]    The groove may be formed in at least one of the first and/or second mating surfaces such that the at least one of the first and/or second mating surfaces forms a wall surrounding the groove. The groove may be formed in at least one of the first and/or second mating surfaces such that the groove is spaced apart from an outer edge of the at least one first and/or second mating surfaces. The groove may be formed in at least one of the first and/or second mating surfaces such that the groove is spaced apart from an inner edge of the at least one first and/or second mating surfaces. The groove may not extend to an outer edge of the at least one first and/or second mating surfaces. The groove may not extend to an inner edge of the at least one first and/or second mating surfaces. The groove may form a trough in the at least one of the first and/or second mating surfaces. The groove may be a hollow in the at least one of the first and/or second mating surfaces. The groove may be a depression in the at least one of the first and/or second mating surfaces. The groove may have a continuous outer edge or wall that is formed in a flat surface of the at least one of the first and/or second mating surfaces. 
         [0008]    The groove may accommodate, house or contain a volume of the seal. 
         [0009]    Advantageously including a groove in at least one of the mating surfaces reduces the leakage of fluid from the axle assembly. The groove enables the inclusion of a thicker seal, which fills a larger gap than standard seal. Because the gap to be filled is larger, then the local thickness of the seal is thicker and this locally thicker seal can better withstand deflections, and thereby better prevent leakage of fluid. 
         [0010]    The central portion may be formed by casting. The opening may be generally circular. The first mating surface may be generally flat. 
         [0011]    The differential carrier assembly may include a crown wheel in driving engagement with a pinion. The carrier may be cast. The carrier flange may be generally circular. The second mating surface may be generally flat. 
         [0012]    The seal may include a mechanical seal, for example a gasket or a sealant such as a gasket maker or a flange sealant. The mechanical seal may include a ductile material. Ductility is the ability of a material to be permanently deformed without breaking when a force is applied. The extent to which a specimen stretches before fracture is its percentage elongation. The elongation of the mechanical seal may be more than 200% of the thickness of the seal, preferably more than 500% of the thickness of the seal. The ductile material may include a polymer, for example silicone. The seal may be an elastomeric sealant. 
         [0013]    The groove may be elongate. The groove may be circumferentially oriented with respect to the first and/or the second mating surface. The groove may extend around less than 45 degrees of the first and/or second mating surface, preferably less than 30 degrees, more preferably less than 20 degrees. The groove may have a length of less than 200 millimeters, preferably less than 100 millimeters. The groove may have a depth of less than 2 millimeters. The groove may preferably have a depth that is less than or equal to 1 millimeter. The groove may be machined in the first and/or second mating surface. Alternatively, the groove may be cast in the first and/or second mating surface. 
         [0014]    The axle flange may have a plurality of fastener holes. The plurality of fastener holes may be spaced circumferentially around the axle flange. The plurality of fastener holes may be threaded to receive a threaded stud or a threaded bolt. 
         [0015]    The groove may have a first end that is adjacent to a first fastener hole and a second end that is adjacent to a second fastener hole, wherein the first fastener hole and second fastener hole are positioned sequentially around the circumference of the axle flange. 
         [0016]    The axle flange and/or the carrier flange may include a first notch and a second notch to accommodate the crown wheel. The groove may be located on the first mating surface adjacent to one of the first or the second notches. The axle assembly may include a second groove located on the same mating surface as the first groove. The second groove may be located adjacent to the other of the first or second notches. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
           [0018]      FIG. 1  is a partial exploded view of an axle assembly according to the present invention; 
           [0019]      FIG. 2  is a partial exploded view of the axle assembly of  FIG. 1 ; 
           [0020]      FIG. 3  is a plan view of the axle housing of the axle assembly of  FIGS. 1 and 2 ; and 
           [0021]      FIG. 4  is a partial perspective view of the axle housing of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0023]    With reference to  FIGS. 1 to 4 , there is shown an axle assembly  10  according to the present invention. The axle assembly  10  includes an axle housing  11  and a differential carrier assembly  15 . 
         [0024]    The axle housing  11  is defined by a first part  12 , a second part  14  and a center portion  20  (also known as a central bowl). 
         [0025]    The first part  12  includes a first axle tube  16  (in this case a left hand axle tube or left hand housing leg) having a first end  16   a  (or outboard end) and a second end  16   b  (or inboard end). The first axle tube  16  has a first opening (not shown) at the first end  16   a  and a second opening (not shown) at the second end  16   b.    
         [0026]    The second part  14  includes a second axle tube  18  (in this case a right hand axle tube or right hand housing leg) having a first end  18   a  (or outboard end) and a second end  18   b  (or inboard end). The second axle tube  18  has a first opening  18   c  at the first end  18   a  and a second opening (not shown) at the second end  18   b.    
         [0027]    The center portion  20  is a hollow structure, cast from a metal such as cast iron. The center portion  20  includes an opening  22 , which is generally circular. The opening  22  is defined by an axle flange  24 . The axle flange  24  is generally annular and has a generally flat mating surface  26 . The first mating surface  26  includes twelve fastener holes  28   a ,  28   b ,  28   c ,  28   d ,  28   e ,  28   f ,  28   g ,  28   h ,  28   i ,  28   j ,  28   k ,  28   l , which are spaced circumferentially around the first mating surface  26 . Each of the fastener holes  28   a ,  28   b ,  28   c ,  28   d ,  28   e ,  28   f ,  28   g ,  28   h ,  28   i ,  28   j ,  28   k ,  28   l  is threaded. 
         [0028]    The axle flange  24  also includes a pair of notches  30   a ,  30   b  and a groove  60 . 
         [0029]    The pair of notches  30   a ,  30   b  extend from the axle flange  24  into the opening  22  of the center portion  20 . Notch  30   a  is located on an upper portion  24   a  of the axle flange  24  and notch  30   b  is located on a lower portion  24   b  of the axle flange  24 . 
         [0030]    The groove  60  is elongate and has a first end  62  and a second end  64 . The groove  60  is positioned adjacent to the notch  30   a  on the upper portion  24   a  of the axle flange  24 . The first end  62  of the groove  60  is positioned adjacent to fastener hole  28   a  in the first mating surface  26  and the second end  64  of the groove  60  is positioned adjacent to fastener hole  281  in the first mating surface  26 . Fastener hole  28   a  is positioned adjacent to fastener hole  28   l  around the periphery of the first mating surface  26 . The groove  60  is less than 200 millimeters long and extends around less than 30 degrees of the first mating surface  26 . The groove has a depth of approximately 1 millimeter. The groove  60  is surrounded by a continuous edge or wall in the generally flat mating surface  26  of the axle flange  24 , thus forming a trench in the generally flat mating surface  26 . 
         [0031]    The first axle tube  16  is connected to the center portion  20  such that the second opening at the second end  16   b  of the first axle tube  16  opens into the center portion  20 . Similarly, the second axle tube  18  is connected to the center portion  20  such that the second opening at the second end  18   b  of the second axle tube  18  opens into the center portion  20 . In this way, the first and second axle tubes  16 ,  18  are connected by the center portion  20 . 
         [0032]    The differential carrier assembly  15  has a carrier  32 . The carrier  32  includes a carrier flange  34  and a mount  40 . The carrier flange  34  is generally annular and has a second mating surface  36  that is generally flat. The second mating surface  36  includes twelve fastener holes  38   a ,  38   b ,  38   c ,  38   d ,  38   e ,  38   f ,  38   g ,  38   h ,  38   i ,  38   j ,  38   k ,  38   l  (only some of which are shown in  FIGS. 1 and 2 ), which are spaced circumferentially around the second mating surface  36 . Each of the fastener holes  38   a ,  38   b ,  38   c ,  38   d ,  38   e ,  38   f ,  38   g ,  38   h ,  38   i ,  38   j ,  38   k ,  38   l  is threaded. 
         [0033]    The mount  40  supports a crown wheel  42 , and a differential  46 . 
         [0034]    The differential carrier assembly  15  includes bearings to rotatably support the pinion  44 . Further bearings rotatably support the crown wheel  42 . These bearings are mounted on mount  40  connected to the differential carrier assembly  15 . The crown wheel  42  is in meshing engagement with the pinion  44  in a manner known in the art. 
         [0035]    The center portion  20  is sized and shaped to accommodate the crown wheel  42 , pinion  44 , differential  46  and the mount  40 . The opening  22  is sized and shaped to allow the crown wheel  42 , pinion  44 , differential  46  and the mount  40  to be passed through the opening  22  and to be received in the center portion  20 . The notches  30   a ,  30   b  in the axle flange  24  are sized and positioned to provide additional space for the outer diameter of the crown wheel  42 , thereby facilitating rotation of the crown wheel  42  when the axle housing  11  and differential carrier assembly  15  are assembled. The differential carrier assembly  15  acts as a cover to close the opening  22  of the center portion  20 . In this way, a fluid for example oil (not shown) for lubricating and cooling the crown wheel  42 , pinion  44  and differential  46  can be retained within the axle housing  11  and the differential carrier assembly  15 . 
         [0036]    The axle assembly  10  is assembled as follows. 
         [0037]    The pinion  44  is mounted on the carrier  32 . The crown wheel  42 , and differential  46  are mounted on the mount  40  of the carrier  32 . 
         [0038]    The differential carrier assembly  15 , upon which the crown wheel  42 , pinion  44  and differential  46  are mounted, is brought into contact with the axle housing  11  such that the crown wheel  42 , pinion  44  and differential  46  and the mount  40  are accommodated within the center portion  20 . 
         [0039]    A layer of sealant  54 , for example an elastomeric sealant e.g., a silicone sealant, such as Dow Corning 7091, Loctite 509, Loctite 518, Permabond LH195 or Permabond LH197, is applied to the first mating surface  26 . The sealant  54  is applied to fill the groove  60  in the first mating surface  26 . 
         [0040]    The second mating surface  36  of the differential housing assembly  14  is brought into contact with the layer of sealant  54  on the first mating surface  26 , such that each of the fastener holes  38   a ,  38   b ,  38   c ,  38   d ,  38   e ,  38   f ,  38   g ,  38   h ,  38   i ,  38   j ,  38   k ,  38   l  in the second mating surface  36  is lined up with each of the fastener holes  28   a ,  28   b ,  28   c ,  28   d ,  28   e ,  28   f ,  28   g ,  28   h ,  28   i ,  28   j ,  28   k ,  28   l  in the first mating surface  26 . The sealant  54  provides a sealing connection between the first mating surface  26  and the second mating surface  36 . 
         [0041]    Threaded bolts or studs  48  (only 4 of which are shown in  FIGS. 1 and 2 ) are passed through the fastener holes  38   a ,  38   b ,  38   c ,  38   d ,  38   e ,  38   f ,  38   g ,  38   h ,  38   i ,  38   j ,  38   k ,  38   l  of the second mating surface  36  and the fastener holes  28   a ,  28   b ,  28   c ,  28   d ,  28   e ,  28   f ,  28   g ,  28   h ,  28   i ,  28   j ,  28   k ,  28   l  of the first mating surface  26  in order to secure the carrier assembly  15  to the axle housing  11 . The threaded bolts  48  have a threaded portion  48   a  at one of their ends and a second threaded portion  48   b  at the other of their ends. The threaded portion  48   a  of each of the threaded bolts  48  engages the threaded portion (not shown) of each of the fastener holes  28   a ,  28   b ,  28   c ,  28   d ,  28   e ,  28   f ,  28   g ,  28   h ,  28   i ,  28   j ,  28   k ,  28   l  in the first mating surface  26 . The threaded portion  48   b  of each of the threaded bolts  48  engages the threaded portion (not shown) of each of the fastener holes  38   a ,  38   b ,  38   c ,  38   d ,  38   e ,  38   f ,  38   g ,  38   h ,  38   i ,  38   j ,  38   k ,  38   l  in the second mating surface  36 . 
         [0042]    The axle assembly  10  is connected to the engine by a drive shaft (not shown) that extends through opening  58  in the differential carrier assembly  15  to the pinion  44 . The engine (not shown) causes the drive shaft (not shown) and pinion  44  to rotate about a longitudinal axis of the vehicle (not shown). 
         [0043]    The pinion  44  is drivingly engaged to the crown wheel  42  to enable the crown wheel to rotate about an axis which is laterally orientated relative to the vehicle (not shown). 
         [0044]    The left hand drive shaft  50  extends through the opening (not shown) in the left hand axle tube  16  and the right hand drive shaft  52  extends through opening  18   c  in the right hand axle tube  18 . 
         [0045]    In this way, the left and right hand drive shafts  50 ,  52  are caused to rotate in a direction which is laterally orientated relative to the vehicle. The left hand drive shaft  50  drives a left hand wheel (not shown) that is rotatably mounted to the axle and the right hand drive shaft  52  drives a right hand wheel rotatably mounted to the axle. 
         [0046]    The differential  46  interacts with the crown wheel  42  to enable the left and right hand drive shafts  50 ,  52  to rotate at different speeds, for example when the vehicle is driving around a corner. 
         [0047]    During movement of the vehicle, the axle housing  11  and differential carrier assembly  15  are exposed to vertical, longitudinal and torsional forces caused by movement of the vehicle, the wheels and the axle shafts. 
         [0048]    These forces cause deformation of the axle assembly  10 . The formation of gaps between the axle housing  11  and the differential carrier assembly  15  is prevented by the sealant  54  within the groove  60  and in the between the first mating surface  26  and the second mating surface  36 . 
         [0049]    The elongation of the sealant material is 600% of the thickness of the sealant applied to the first mating surface  26 . In use, the additional sealant  54  within the groove  60  is able to deform to fill any gaps that might otherwise form between the axle housing  11  and the differential carrier assembly  15  as a result of vertical, longitudinal and torsional forces acting on the axle assembly  10  caused by movement of the vehicle. In this way, leakage of fluid from within the axle assembly is prevented. 
         [0050]    The groove  60  is positioned between adjacent fastener holes so that the sealant  54  is provided at a region of the axle assembly  10  that is not secured or fastened together by threaded bolts or studs  48 , i.e., the sealant  54  is provided at a region that is at risk of gaps forming when the axle assembly  10  is exposed to vertical, longitudinal and/or torsional forces. 
         [0051]    The groove  60  is positioned adjacent to the notches  30   a ,  30   b  since this is a region of the axle flange  24  where the width of the first mating surface  26  is reduced. This region of the axle flange  24  is at risk of gaps forming when the axle assembly  10  is exposed to vertical, longitudinal and/or torsional forces. 
         [0052]    In the embodiment described above, the center portion  20  of the axle housing  11  is cast with the groove  60  on the first mating surface  26 . In alternative embodiments, the groove may be formed by machining. 
         [0053]    In the embodiment described above, the groove  60  is positioned adjacent to the notch  30   a  on the upper portion  24   a  of the axle flange  24 , with the first end  62  of the groove  60  positioned adjacent to fastener hole  28   a  and the second end  64  of the groove  60  positioned adjacent to fastener hole  281 . The fastener hole  28   a  is adjacent to the fastener hole  28   l . The fastener holes  28   a ,  28   l  are positioned next to each other, or contiguous, or physically adjacent, or neighboring, around the periphery or circumference of the axle flange  24 . In alternative embodiments, the groove may be positioned adjacent to the notch  30   b  on the lower portion  24   b  of the axle flange  24 , with the first end  62  of the groove positioned adjacent to fastener hole  28   f  and the second end  64  of the groove positioned adjacent to fastener hole  28   g . The fastener hole  28   f  is adjacent to the fastener hole  28   g . The fastener holes  28   f ,  28   g  are positioned next to each other, or contiguous, or physically adjacent, or neighboring, around the periphery or circumference of the axle flange  24 . In alternative embodiments, the groove may be positioned such that the first end  62  is adjacent to one of the fastener holes  28   a ,  28   b ,  28   c ,  28   d ,  28   e ,  28   f ,  28   g ,  28   h ,  28   i ,  28   j ,  28   k ,  28   l  and the second end  64  is adjacent to a second of the fastener holes, the second of the fastener holes being positioned adjacent to, contiguous with or next to, or physically adjacent, or neighboring, the first of the fastener holes. 
         [0054]    In the embodiment described above, the groove  60  is located on the first mating surface  26  of the axle flange  24 . In alternative embodiments, the groove may be located on the second mating surface  36  of the differential carrier assembly  15 . The groove may be machined in the second mating surface  36  of the differential carrier assembly  15 . In this way, a differential carrier assembly  15  having a groove may be retrofitted to an existing axle assembly. 
         [0055]    In the embodiment described above, the sealant is a silicone sealant. In alternative embodiments, the sealant may include any material suitable for adhering and/or sealing the first mating surface  26  to the second mating surface  36 , for example any gasket maker. In alternative embodiments, the sealant may be a gasket, for example a gasket including silicone. 
         [0056]    In the embodiment described above, and as shown in  FIGS. 1 and 2 , the threaded bolts or studs  48  have threaded portions  48   a ,  48   b  at each of their ends. In alternative embodiments, bolts with threads at only one of the ends may be used. 
         [0057]    In the embodiment described above, the axle flange  24  and the carrier flange  34  each have twelve fastener holes. In alternative embodiments, any number of fastener holes may be included on each of the axle flange  24  and the carrier flange  34 . 
         [0058]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.