Patent Publication Number: US-8535191-B1

Title: Aluminum flange with anti-rotation slots

Description:
BACKGROUND 
     Differential assemblies are typically configured to transmit an input drive torque from a pinion gear to an axle output shaft through a ring gear, associated bevel pinion gears and a differential housing, which are mounted within a driveline assembly, such as an axle or transmission housing. The bevel pinion gears mesh with corresponding output bevel gears attached to left and right output shafts that extend one on each side of the ring gear. The differential assembly compensates for speed differences between left and right wheels connected to the left and right output shafts. Differential assemblies are typically of three types, a locking, limited slip and an open type. The differential housing may be one or two pieces and are generally constructed of cast iron. Indeed, cast iron differential housings are commonly used due to its low cost of manufacture and high strength. However, cast iron differential housings adversely impact vehicle weight by contributing significantly to the weight of a vehicle&#39;s rotating inertia. While the use of lower weight materials such as aluminum would significantly reduce the differential weight, issues surrounding the use of such lightweight materials have other concerns. For example, issues surrounding the use of aluminum housings may include decreased wear resistance at a contact area with a side gear shim, strength and deflection issues over the full operating temperature range, as well as increased transmission of noise and vibration. 
     Manufacturers are constantly attempting to reduce vehicle weight to improve fuel and driveline efficiency, which is a continued topic with regulators and a driving force of component design in the automotive industry. Housing size and weight are generally determined by the vehicle engine size, operating conditions, strength of the housing and clearances needed for the rotating assembly configured within the housing. Thus, it is desirable to find individual components that may be constructed of resilient materials and designs to minimize weight while maintaining or improving strength and resiliency of the components. Therefore, there is a need in drivetrain design to provide a differential that benefits from the weight savings of partial or all-aluminum housings, while maintaining the strength and economy of the all cast iron housing. 
     BRIEF SUMMARY 
     A differential flange assembly is disclosed herein that includes a flange member and a washer member. The flange member is defined by an engagement face and having an aperture therethrough. At least one slot is formed on the engagement face so as to extend radially outward from the aperture. The washer member has at least one tab extending from a peripheral edge of the washer member and at least one opening. The tab is configured to be seated within the slot to mate the washer member to the engagement face of the flange member. The interaction of the slot of the flange member and the tab of the washer member prevent rotation of the washer member with respect to the flange member. 
     The differential flange assembly may be used as part of a differential assembly that includes the differential flange and a differential carrier. In one exemplary arrangement, the differential housing may include cast iron differential carrier and that cooperates with light weight material flange to contain the components of the differential assembly. In one particular exemplary arrangement, the flange may be constructed of aluminum for reduced weight. The tabbed washer may also provide at least one of a sliding surface and a reaction surface during high loading and high speed deltas, thereby serving to protect the aluminum flange. 
     The flange may be configured with at least one oil channel beneath a washer. At least one oil channel is configured to provide lubrication paths for both the gear and washer surfaces of the differential assembly. A circumferential oil groove may also be formed in the flange to direct the oil behind a side gear. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the drawings, illustrative embodiments are shown in detail. Although the drawings represent some embodiments, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present invention. Further, the embodiments set forth herein are exemplary and are not intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and configurations shown in the drawings and disclosed in the following detailed description. 
         FIG. 1  illustrates a top view of an exemplary driveline system that includes an exemplary differential assembly; 
         FIG. 2  illustrates an exploded view of an exemplary differential assembly illustrated in  FIG. 1 ; 
         FIG. 3  illustrates a partial cut-out view of the exemplary differential assembly of  FIG. 2  assembled; 
         FIG. 4  illustrates an isometric front view of an exemplary flange from the differential assembly of  FIG. 2 ; 
         FIG. 5  illustrates a cross-sectional view of the exemplary flange of  FIG. 4 ; 
         FIG. 6  illustrates a plan view of an exemplary tabbed washer; and 
         FIG. 7  illustrates a cross-sectional view of the exemplary tabbed washer of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to a two-piece torque transmitting differential assembly. The two pieces include a flange constructed of a first material and a differential carrier constructed of a second material that is different than the first material. The materials may be aluminum, steel, grey iron, ductile cast iron, nodular cast iron, spheroidal graphite iron, spherulitic graphite cast iron or other known material. 
       FIG. 1  illustrates an exemplary driveline assembly  100  of a vehicle. The driveline assembly  100  includes an engine  112  that is connected to a transmission  114  and a power take off unit  116 . It should be realized that the differential unit  150  may also be used without power transfer unit to provide a front wheel drive gear ratio, thus the disclosure is not limited to the arrangement illustrated in  FIG. 1 . Generally, the engine  112  may be affixed to the transmission  114  through an engine crankshaft (not shown) that is fixed to a transmission input shaft to provide torque to the transmission  114 . The torque may be transmitted through a series of gears (not shown), within a transmission housing, and ultimately to a transmission output shaft (not shown). A front differential  150  may be rotatively connected to the transmission output shaft through a ring gear. 
     Front differential  150  has a plurality of shaft elements  132 ,  134  and corresponding articulating torque transfer joints  142 . For example, front differential assembly  150  includes right hand front half shaft  132  and a left hand front half shaft  134 , each of which are connected to a wheel  144  and are configured to deliver power to those wheels  144 . While the joints  142  are illustrated as constant velocity joints  142 , it is understood that other types of joints may be used, such as, but not limited to universal, tripod, cardan, double cardan and plunging constant velocity joints. 
     For the exemplary arrangement of  FIG. 1 , the power take off unit  116  has a propeller shaft  160  and a front wheel propeller shaft  161  extending therefrom. The front wheel propeller shaft  161  connects the front differential  150  to the power take off unit  116 . The propeller shaft  160  connects the power take off unit  116  to a rear differential  150 ′, wherein the rear differential  150 ′ includes a rear right hand side shaft  132 ′ and a rear left hand side shaft  134 ′, each of which ends with a wheel  144  on one end thereof. 
     The propeller shaft  160  may include an articulated tripod joint  145 , a front propshaft  147 , a rear propshaft  149 , and two high speed constant velocity joints  142 . The constant velocity joints transmit power to the wheels  144  through the driveshaft  160  even if the wheels or the shaft have changing angles due to steering and suspension jounce and rebound. A constant velocity joint  142  is located on both ends of the half shafts that connect to the wheel  144  and the rear differential  150 ′. 
     As discussed above, the driveline  100  represents an all wheel drive vehicle, however it should be noted that the embodiments of the differential assemblies  150 ,  150 ′ of the current disclosure can also be used in rear wheel drive vehicles, front wheel drive vehicles, all wheel drive vehicles and four wheel drive vehicles. 
     Referring now to  FIG. 2 , elements of an exemplary differential assembly  150 , will now be described in detail. Differential assembly  150  includes a differential carrier  210 , and a differential flange  212  that cooperate configured to secure a series of gears and components within the differential carrier  210 , as will be explained in further detail below. For example, differential assembly  150  further includes left hand side gear hub  232 , a right hand side gear hub  234 , thrust washers  214 ,  228 , at least one pinion shaft  216 , a plurality of pinion gears  218 ,  220  and pinion washers  222 ,  224 , and a tabbed washer  230 . 
     Thrust washer  214  is mounted over a shaft portion  235  of right hand side gear hub  234 , opposing a side gear  238  secured to an end of shaft portion  235 . Assembled thrust washer  214  and right hand side gear hub  234  are positioned within a cavity  236  of the differential carrier  210  such that an end  241  of right hand side gear hub  234  extends through an opening  243  of differential carrier  210 , as illustrated in  FIG. 3 . 
     In the embodiment shown in  FIGS. 2-3 , pinion shaft  216  is configured as a two pinion gear arrangement, however it is understood that other pinion gear arrangements are contemplated, including a four pinion gear arrangement. Pinion shaft  216  has a first pinion gear  218  secured on one end, a second pinion gear  220  secured on an opposite end, and pinion thrust washers  222 ,  224  positioned radially outward of the pinion gears  218 ,  220 . The pinion shaft  216 , the gears  218 ,  220  and pinion washers  222 ,  224  are also positioned within the cavity  236  such that the pinion gears  218  (omitted from  FIG. 3  merely for illustrative purposes),  220  are engaged with side gear  238  of right hand side gear hub  234 . During assembly, the first or second pinion gears  218 ,  220  may be positioned within the cavity  236  and the pinion shaft  216  may be slid through a corresponding aperture  242  (best seen in  FIG. 2 ) and connected to the opposing gears  218 ,  220  and thrust washers  222 ,  224  such that the pinion shaft  216 , the pinion thrust washers  222 ,  224  and the pinion gears  218 ,  220  are rotatively fixed to the differential carrier  210 . Additionally, to prevent the pinion shaft  216  from sliding out of the differential carrier  210 , a lock pin  226  may be provided that is configured to engage with a pinion shaft aperture  246  in the pinion shaft  216  and a lock pin cavity  346  (see  FIG. 3 ) configured in the differential carrier  210 . 
     Thrust washer  228  is mounted over a shaft portion  233  of left hand side gear hub  232 , opposing a side gear  240  secured to end of shaft portion  233 . Tabbed washer  230  is also mounted over the shaft portion  233  of left hand side gear hub  232 . Left hand side gear hub  232  is positioned within cavity  236  such that side gear operatively engages with pinion gears  218 ,  220 . Shaft portion  233  extends outwardly from cavity  236  of differential carrier  210 . As discussed above, the flange  212  is configured to cooperate with the differential carrier  210  to retain the internal components of the differential assembly  150  therewithin. 
     In the exemplary arrangement, the flange  212  is made of a light-weight material, such as aluminum, to reduce the weight of the differential assembly  150 . In one exemplary arrangement, the flange  212  is constructed of aluminum. More specifically, the flange  212  may be constructed of an aluminum alloy, such as, but not limited to a 6013 alloy with a T6 heat treatment. The alloy may be an aluminum-magnesium-silicon-copper alloy typically used in the aircraft industry. The use of a light weight material, such as aluminum, for the flange  212  serves to provide a differential assembly  150  with a significantly reduced weight. The 6013 alloy with T6 heat treatment may also be utilized due to its relatively stable strength under vehicle engine operating temperatures. Other suitable light-weight materials, including, but not limited to, titanium and magnesium, may also be used. 
     Details of the flange  212  are best seen in  FIGS. 4-5 . More specifically, the flange  212  is defined by an outer periphery mating surface  410  that may be configured with a plurality of apertures  254  each configured to receive fasteners (not shown), such as, for example, a bolt. Mating surface  410  is configured to mate with a corresponding outer periphery mating surface  411  of differential carrier  210 . Mating surface  411  also includes a plurality of apertures  256  that are configured to align with apertures  254 . In one exemplary arrangement, apertures  256  are threaded to facilitate connection of the flange  212  to differential carrier  210 . To facilitate proper alignment of flange  212  and differential carrier  210 , outer periphery mating surface  410  may be provided with at least one alignment feature  414  that is configured to cooperate with a corresponding alignment feature disposed on the differential carrier  210 . In the exemplary configuration illustrated in  FIGS. 3-5 , the alignment feature  414  is configured as an aperture that receives an alignment fastener  252 . Alignment fastener  252  is configured to be received through alignment element  414  and engage a corresponding alignment aperture (not shown) formed on outer periphery mating surface  411  of differential carrier  210 . 
     Flange  212  is further defined by a center aperture or shaft support  424  configured to receive the shaft portion  233  of the left hand gear hub  232  therethrough (best seen in  FIG. 3 ). Extending around center aperture  424  is a raised pilot ring  416 . Pilot ring  416  is configured to be inserted into a corresponding recess (best seen in  FIG. 3 ) of the differential carrier  210 , so as to facilitate alignment of flange  212  with differential carrier  210 . 
     Flange  212  further includes at least one slot  417  that extends radially outward from central aperture  424 . Slots  417  are sized to receive tabs  248  of the tabbed washer  230 , as will be explained below in further detail. In the exemplary arrangement illustrated in  FIGS. 3-5 , there are three slots  417  provided that are spaced equally apart. Each slot  417  includes an end portion  415  and an inner portion  419 . End potion of the slot  417  is positioned within an outer land area  422  that is positioned between pilot ring  416  and an inner land area  423 . Inner portion  419  of slot  417  is formed in inner land area  423  and opens into central aperture  424 . A circumferential oil channel  420  is formed between the outer and inner land areas  422 ,  423  so as to divide slot  417  into end portion  415  and inner portion  419 . 
     Flange  212  may further include at least one oil groove  418  that is fluidly connected to slot  417  and oil channel  420 . In one exemplary arrangement, oil groove  418  extends from oil channel  420  via inner portion  419  of slot  417  along an inside surface of  421  of central aperture  424 . In one exemplary configuration, oil groove  418  is configured as spiral-shaped and extends the length of the central aperture  424  to a rearward edge  425  thereof, as best seen in  FIG. 5 . However, other shaped oil grooves  418  are also contemplated. In the exemplary arrangement illustrate herein, at least one oil groove  418  extends from each slot  417  such that there are an equal number of oil grooves  418  and slots  417 . The function of the oil groove  418  and oil channel  420  will be described in further detail below. 
     Referring to  FIGS. 6-7 , the structure of the exemplary tabbed washer  230  will now be described in detail. As discussed above, the tabbed washer  230  includes at least one tab  248  that extends radially outward from an outer periphery  712  of the tabbed washer  230 . In the exemplary arrangement illustrated herein, the tabbed washer  230  includes three tabs  248  equally spaced apart and configured to mate with the slots  417 . However, it is understood that the number of tabs  248  may vary and is predetermined based on the number of slots  417  configured in the flange  212 . The tabbed washer  230  is also configured with a through aperture  710  to enable tabbed washer  230  to be disposed over the shaft portion of left hand side gear hub  232 . As best seen in  FIG. 7 , the tabbed washer  230  is further defined by a generally planar top surface  714  and a generally planar bottom surface  716 . At least one of the planar surfaces  714 ,  716  may be configured as at least one of a sliding surface and a reaction surface during high loading and high speed operation of the differential assembly  150  to protect the flange  212  from excessive wear due to rubbing between at least one of the washer  228 , the tabbed washer  230  and the flange  212 . In some exemplary arrangements, one or both of the planar surfaces  714 ,  716  of tabbed washer  230  may be treated and/or coated for improved wear resistance at the washer surface. Further, in some exemplary arrangements, the thickness of tabbed washer  230  may be designed to be sufficiently wide enough such that thrust washer  228  may be eliminated from the differential assembly  150 . 
     Tabbed washer  230  is assembled to flange  212  such that tabs  248  are positioned within slots  417 . In one exemplary arrangement, slots  417  and tabs  248  are configured such that tabbed washer  230  are press-fit within slots  417 . In another exemplary arrangement, slots  417  are sized to be slightly larger than tabs  248 , thereby enabling tolerances to be relaxed. Once tabbed washer  230  is positioned within slots  417 , tabbed washer  230  is supported on inner land area  423  such that oil channel  420  forms a trough underneath tabbed washer  230 . 
     Once tabbed washer  230  is assembled to flange  212 , the two elements may then be slid over shaft potion  233  of left hand gear hub  232 . If thrust washer  228  is provided, thrust washer is slid over shaft portion  233  of left hand gear hub  232  so as to be positioned between tabbed washer  230  and side gear  240 . Outer mating periphery  410  of flange  212  is mated to outer mating periphery  411  and secured together by suitable fasteners (not shown), such as, for example, bolts. When assembled, the flange  212  is thus rotatively fixed to the differential carrier  210 . In one exemplary arrangement the fasteners are configured to extend through the plurality of apertures  254 , and further configured to engage into a corresponding threaded aperture positioned on the differential carrier  210 . The fasteners may be tightened to a predetermined torque. As also discussed above, the outer periphery mating surface  410  may include at least one alignment element  414  that is configured to engage a corresponding alignment element configured on the differential carrier  210 . The alignment element  414  is illustrated in  FIG. 4  as an aperture that is configured to receive an alignment pin that is either configured directly on the differential carrier  210  (not shown) or an alignment pin  252  that is inserted through the aperture  414  during assembly. 
     The slots  417  are configured on the mating surface of outer mating periphery  410  to provide a compressive fit for trapping the tabbed washer  230  when the flange  212  is fastened to the differential carrier  210 , as discussed above. Due to reaction forces from the gear set  218 ,  220 ,  238 ,  240  positioned within the differential carrier  210 , and the interaction between the tabs  248  and the slots  417 , rotation of the washer  230  is prevented. The axial position of the tabs  248  within the slots  417  is maintained by the clamping of the flange  212  to the differential carrier  210 , as best illustrated in  FIG. 3 . 
     As also described above, the flange  212  may also include the raised pilot ring  416  that is configured to be received within an opening of differential housing  212 . For certain light-weight materials, the raised pilot ring  416  will expand due to the operational temperatures experienced by the differential assembly  150 . This expansion will further enhance securement between the flange  212  and the differential carrier  214 . 
     The oil groove  418  configured within central aperture  424  serves to provide a lubricant to the inner surface of central aperture  424 , as well as to the shaft portion  233  of left hand gear hub  232 . As discussed above, the oil groove  418  may be fluidly connected to the oil channel  420  configured on the flange  212  inner land surface  422  to provide the lubricant beneath the tabbed washer  230 . The oil groove  418  and the oil channel  420  are configured to provide lubrication paths for both the gears  218 ,  220 ,  238 ,  240  and washers  230 ,  228 ,  214 ,  222 ,  224  surfaces. The oil channel  420  in the flange  212  also serves to direct the lubricant to the side gears  238 ,  240 . Additionally, a corresponding lubricant system (not illustrated) may be configured in the differential carrier  210 . 
     The left hand gear hub  232  is shown as a hollow tube configured with a splined section  310 . The splined section  310  is configured to receive a corresponding splined section (not illustrated) configured on at least one of the shaft element  132  and the joint  142 , depending on the application. The engagement with the spline section  310  rotatively fixes the differential assembly  150  with at least one of the shaft elements  132  and the joint  142  to transmit torque from the transmission  116  to the wheels  144 . 
     The preceding description has been presented only to illustrate and describe exemplary embodiments of the methods and systems of the present invention. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. The invention may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope. The scope of the invention is limited solely by the following claims. 
     The present disclosure has been particularly shown and described with reference to the foregoing illustrations, which are merely illustrative of the best modes for carrying out the disclosure. It should be understood by those skilled in the art that various alternatives to the illustrations of the disclosure described herein may be employed in practicing the disclosure without departing from the spirit and scope of the disclosure as defined in the following claims. It is intended that the following claims define the scope of the disclosure and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. This description of the disclosure should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. Moreover, the foregoing illustrations are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application. 
     Reference in the specification to “one example,” “an example,” “one embodiment,” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the example is included in at least one example. The phrase “in one example” in various places in the specification does not necessarily refer to the same example each time it appears. 
     With regard to the processes, systems, methods, heuristics, etc. described herein, it should be understood that, although the steps of such processes, etc. have been described as occurring according to a certain ordered sequence, such processes could be practiced with the described steps performed in an order other than the order described herein. It further should be understood that certain steps could be performed simultaneously, that other steps could be added, or that certain steps described herein could be omitted. In other words, the descriptions of processes herein are provided for the purpose of illustrating certain embodiments, and should in no way be construed so as to limit the claimed invention. 
     Accordingly, it is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments and applications other than the examples provided would be upon reading the above description. The scope of the invention should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the arts discussed herein, and that the disclosed systems and methods will be incorporated into such future embodiments. In sum, it should be understood that the invention is capable of modification and variation and is limited only by the following claims. 
     All terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those skilled in the art unless an explicit indication to the contrary in made herein. In particular, use of the singular articles such as “a,” “the,” “the,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary.