Patent Abstract:
An oil pump assembly is shown for wet oil sump applications at extreme angles for power sports equipment. The oil pump is comprised of a pump body, an oil pick-up and a driven gear shield, where these components may be integrally formed from die cast aluminum. The pump body includes a rotor body housing a gerotor assembly for pumping. The oil pump is attached to the rear wall of the crankcase and below the crankshaft, and is driven by the crankshaft.

Full Description:
FIELD OF INVENTION 
       [0001]    The subject invention relates to a wet oil sump system for four cycle engines, with particular use in power sports vehicular applications. 
       BACKGROUND OF THE INVENTION 
       [0002]    Lubrication systems in four cycle engines typically take one of two approaches, the first, a “wet oil sump” has a pool of oil at the bottom of the crankcase or oil pan together with an oil sump that siphons oil from the sump; or second, a “dry sump” which has an extra oil tank provided outside of the engine with an internal pump to distribute the oil to the engine. In either system, oil is distributed to lubricate such items as the main bearings of the crankshaft, the pistons and cylinder walls, connecting rods, cam shaft bearings, valves, and the like. In either the “wet sump” or “dry sump” system, oil is distributed through the various points and returned to the sump in a relatively closed loop system. 
         [0003]    In the power sports industry, for example in four cycle engines that power snowmobiles and ATVs, the engines need to operate at extreme angles as the vehicles ascend and descend at a multitude of extreme angles. In this working environment, there has heretofore been tradeoffs between the wet oil sump and the dry oil sump methodology. As a dry sump system utilizes a closed volume for housing the lubricating oil, the volume of oil required to supply the system is less however the system is more complex as it requires an extra reservoir. The dry sump system however is less sensitive to the angles at which it operates and is therefore sometimes desired for extreme angles. 
         [0004]    Wet oil sumps on the other hand, are easier to design as the engines are simply designed to allow the oil reservoir to pool at the bottom of the engine crankcase to create the oil sump. Due to the angle changes of the engine during the traversing of the vehicle, however, a larger volume of oil is required to ensure that the level of the oil is always maintained at or above the oil pump pickup. 
         [0005]    Other shortcomings of present oil supply systems are also addressed in this disclosure. Most oil pumps are driven by a drive gear in meshing engagement with the crankshaft and the drive gear simply rotates within the pool of oil in the oil sump. This location of the drive gear within the oil sump may produce disadvantages to the overall system for a number of reasons. First, extra horsepower is required to drive the drive gear through the oil sump due to the resistance of the gear traveling in the oil. Second, the gear driven within the oil aerates the oil which in turn causes a decrease in the lubrication effect of the oil due to the air within the oil. Thirdly, driving the drive gear through the oil heats the oil which then in turn places a larger load on the oil cooler which may also cause an overall reduction in horse power. 
       SUMMARY OF THE INVENTION 
       [0006]    In a first embodiment, an engine and pump assembly comprises a crankcase having a crankcase wall with an opening therethrough, an oil pump body, a pumping member and an oil pump cap, with the oil pump body and pumping member positioned internally of the crankcase wall. The oil pump cap is positioned externally of the crankcase wall. The oil pump body has a sump member extending into an oil reservoir, and a pump case to receive the pumping member. 
         [0007]    In another embodiment, an oil pump assembly comprises an oil pump body for insertion within a crankcase. The oil pump body has an integral oil sump member extending into an oil reservoir, and an integral pump case. A pumping member is receivable in the pump case, and is profiled to pump oil upon rotation thereof. 
         [0008]    In yet another embodiment, an oil pump assembly comprises an oil pump body and an oil pump case for insertion within a crankcase; an oil sump member for extending into an oil reservoir; a pumping member receivable in the pump case, and being profiled to pump oil upon pumping movement thereof. A drive gear drives the pumping member and a drive gear shield at least partially surrounds the drive gear and prevents the drive gear from being submersed into oil in the oil reservoir. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of a two cylinder four cycle engine shown from a drive side; 
           [0010]      FIG. 2  shows a partially exploded view of the four cycle engine of  FIG. 1 ; 
           [0011]      FIG. 2A  is an enlarged view of a portion of the four cycle engine of  FIG. 2 ; 
           [0012]      FIG. 3  shows a cross-sectional view through lines  3 - 3  of  FIG. 2 ; 
           [0013]      FIG. 4  is an exploded view of the oil pump; 
           [0014]      FIG. 4A  is a perspective view of the oil pump cover, from an opposite side as that viewed in  FIG. 4 ; 
           [0015]      FIG. 5  is a cross-sectional view through lines  5 - 5  of  FIG. 4 ; 
           [0016]      FIG. 6  is a view similar to that of  FIG. 3  showing the oil pump exploded away from the engine crankcase; 
           [0017]      FIG. 7  is a view similar to that of  FIG. 6  showing the oil pump attached to the engine crankcase; 
           [0018]      FIG. 8  shows a perspective view showing the interaction between the oil pump and the oil pump cover; 
           [0019]      FIG. 9  shows a longitudinal cross-section through the engine and the oil pump. 
           [0020]      FIG. 10  shows a cross-sectional view similar to that of  FIG. 9 , but as a side section; 
           [0021]      FIG. 10A  shows a cross-sectional view similar to that of  FIG. 10A , but when in the nose-up condition at 65°; 
           [0022]      FIG. 10B  shows a cross-sectional view similar to that of  FIG. 10 , but when in the nose-down condition at 35°; and 
           [0023]      FIG. 11  shows a partial perspective cutaway of the camshaft sprocket guide. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0024]    With reference first to  FIGS. 1 and 2 , a four cycle in-line two cylinder engine is shown at  2  comprised of an engine head  4  and an engine crankcase at  6 . Engine head  4  includes first and second cylinders  8 ,  10  (and crankcase compartments,  8 A,  10 A (FIG.  2 )), and a bell housing  12  defined by a combination of head  4  and crankcase  6 . Crankcase  6  includes a rear wall  14  to which an oil pump assembly  16  is attached as described further herein. Engine head  4  and crankcase  6  may be comprised of a hypereutectic aluminum alloy material (similar to that disclosed in U.S. Pat. No. 5,253,625, which is incorporated herein by reference) however where the cylinder bores are honed and polished to a point where the silicon is proud of the remaining surface material in the bore. 
         [0025]    With reference now to  FIGS. 2 and 2A , head  4  is shown exploded away from crankcase  6 , with crankshaft  20  also shown removed. Oil pump assembly  16  is also shown exploded away from the crankcase and includes an outer cap  22  and an inner oil pump  24 , as described further herein. Rear wall  14  is shown including a mounting area  26  which is comprised of a mounting bore  28  and a supply opening at  30 . Bore  28  has a flange  32  in surrounding relation with a plurality of threaded openings at  34 . Meanwhile opening  30  includes a flange at  36  having threaded openings at  38 . Outer cap  22  includes a flange  42  having openings  44  aligned with openings  34 , and flange  46  having openings  48  aligned with threaded openings  38 . Apertures  50  are provided for mounting the pump  24  within bore  28  as will be described herein. 
         [0026]    As also shown in  FIG. 2A , gasket  60  is provided having gasket portion  62  for alignment with flange portions  32 ,  42 ; apertures  64  for alignment with apertures  34 ,  44 ; gasket portion  66  for alignment with flange portions  36 ,  46 ; and apertures  68  for alignment with apertures  38 ,  48 . Gasket  60  further includes apertures  70  for alignment with apertures  50 , and includes a central opening at  72  and an elongate opening at  74  as described herein. Finally, pump assembly  16  includes a plurality of fasteners, fasteners  84  for receipt through apertures  44 , fasteners  88  for receipt through apertures  48  and fasteners  90  receivable through apertures  50 . With reference now to  FIG. 2B , oil cap  22  includes an inside surface at  52  having defined therein an oil channel  54  defining a discharge channel  56  and a supply channel  58 . 
         [0027]    With reference now to  FIG. 3 , an inside of the crankcase  6  is shown, where rear wall  14  includes an inside surface at  100  having a recess at  102  positioned just below mounting bore  28 . Crankcase  6  also includes a lower surface at  104  and upright surfaces  106  which would together define oil sump  108 . Supply opening  30  ( FIG. 2A ) would be in fluid communication with oil regulator  110  as further described herein. 
         [0028]    With reference now to  FIG. 4 , oil pump  24  will be described in greater detail. Pump  24  is generally comprised of a pump housing  120 , a gerotor assembly  122 , a drive shaft  124 , a driven gear  126  and a pump cover  128 . With reference now to  FIGS. 4 and 5 , pump housing  120  will be described in greater detail. Pump housing  120  is comprised of an integrated die cast aluminum member which includes a rotor housing  130 , an oil pickup  132 , an upright housing portion  134  and a gear shield  136 . As shown best in  FIG. 5 , rotor housing  130  includes an internal diameter at  140  to receive the gerotor assembly  122  and further includes an internal passage way  142  defined within the upright passageway  134  which communicates with discharge opening  144 . Finally, pickup  132  includes a volume  146  and pump housing  120  includes a central aperture  148  provided for receiving drive shaft  124  as described herein. 
         [0029]    As shown in  FIG. 4 , gerotor assembly  122  includes an inner rotor  150  and an outer rotor  152 . Inner rotor  150  includes gear teeth  154  whereas outer rotor includes mating teeth  156 . It should be appreciated that according to the gerotor geometry, outer rotor  152  includes one more tooth than inner rotor  150  thereby defining a vacuum/suction side and a pressure/discharge side upon rotation of the inner and outer rotor together within internal diameter  140 . Inner rotor also includes a slotted opening at  158  which, as should be understood, receives pin  160  and shaft  124 . 
         [0030]    Thus to assemble pump  24 , shaft  124  is positioned within aperture  158  of inner rotor  150  and inner rotor  150  is positioned within outer rotor  152 . Driven gear  126  is now be positioned within drive shield  136  and shaft  124 , together with inner and outer rotors  150 ,  152 , is positioned through aperture  148  with drive shaft flattened portion  162  received in the corresponding opening  164  of driven gear  126 . It should be appreciated that driven gear  126  is held to shaft  124  by way of suitable fasteners, such as a thrust washer  166 , together with flat washers  168  and snap ring  170 . At this point, pump cover  128  can be positioned over rotor housing  130  with free end  172  of shaft  124  being journalled in aperture  174  ( FIG. 4A ) of pump cover  128 . Fasteners  176  can be positioned through apertures  178  and received in threaded openings  180  in rotor housing  130 . This positions the discharge slot  190  in pump cover  128  in position to the pressure/discharge side of the gerotor assembly  122  as described above. This also positions apertures  194  in position over threaded bosses  196  as will be described in further detail herein. Finally, a filter  200  can be held to the oil pickup  132  by way of an insert  202  and a spring clip  204  attached to lugs  206  (only one of which can be viewed in  FIG. 4 ). 
         [0031]    With reference now to  FIGS. 2 and 6 , with the pump  24  as assembled, pump  24  is receivable into crankcase cavity  8   a , which corresponds to cylinder  8  ( FIG. 2 ). Pump  24  is receivable in bore  28  as shown. As mentioned above, pump cap  22  and gasket  60  are receivable over mounting area  26  and as shown in  FIG. 2A , and pump cap  22  is held in place by fasteners  84  and  88 . With the pump  24  so positioned, apertures  50  in pump cap  22  align with apertures  194  ( FIG. 4 ) in pump cover  128 , and threaded openings  196  of pump body  120  ( FIG. 4 ), and fasteners  90  received through apertures  50  pull the entire pump assembly  24  forward into gasket  60 , which in turn is trapped between pump cover  128  and surface  52  ( FIG. 2B ) of pump cap  22 . It should be appreciated then that the gasket  60  has two separate functions, firstly to seal the connection between the pump cap  22  with the mounting area  26  and secondly, to seal the connection of the pump  24  relative to the pump cap  22 . 
         [0032]    As installed, the upright body portion  134  ( FIG. 4 ) of the pump housing  120  is received in the recess  102  ( FIG. 6 ) of the crankcase wall  14  as best shown in  FIG. 7 . As installed, discharge slot  190  of pump cover  128  is aligned with the slot  54  of pump cap  22 . Furthermore, discharge slot  58  has been aligned with supply opening  30  and thereafter to oil regulator  110  as described above. Crankshaft  20  is now positioned in the corresponding journals of crankcase  6 , with drive gear  200  is in meshing engagement with driven gear  126  as shown in  FIG. 9 . As pump  24  is tucked into recess  104 , the pump  24  provides a low profile arrangement allowing clearance for the crankshaft to rotate, as best viewed in  FIG. 9 . 
         [0033]    Thus, due to the geometry of the oil pump  24  together with the geometry of the crankcase, the engine can operate at extreme angles both front to back and side to side, in fact, can operate nose up to 65°, nose down to  350 , and side to side at  450 . This is accomplished at least in part by the crankcase  6  and head  4  being designed to allow complete drainage of oil, and to prevent excessive pooling of oil. 
         [0034]    More particularly and with reference to  FIGS. 9 and 10 , the crankshaft compartments  8 A and  10 A are separated by a mid wall  210  which defines the two compartments. The two compartments  8 A,  10 A have fluid communication by way of conduit  212 . Compartment  10 A is smaller than compartment  8 A and in fact is roughly ⅓ the total volume of the two compartments together. Furthermore, and with reference to  FIGS. 10 and 11 , the crankcase  6  and head  4  define a camshaft tunnel  230  for camshaft  232 . A transverse channel  234  is positioned inward of tunnel  230 , and communicates with apertures  236 A and  236 B which empty back into compartment  8 A. These apertures are positioned below the windage plate  238 , and their function and operation are defined below. 
         [0035]    With reference first to  FIG. 10 , the engine  2  is shown in a level condition with oil levels of  220  and  222  being substantially level with each other, and which together would accumulate to approximately 2 quarts of motor oil. With respect now to  FIG. 10A , the nose up condition at 65° is shown with the modified oil level shown in this condition, substantially all of the oil is shown in compartment  8 A, having drained through the conduit  212 . The conduit  212  does not impede oil transfer between the compartments  8 A,  10 A but rather prevents “sloshing” about in the crankcase. 
         [0036]    With reference now to  FIG. 10B , the vehicle is shown with nose down position at 35°. Due to the relative volume sizes of the compartments  8 A and  10 A, as mentioned above, the oil will never completely drain from the wet sump within crankcase compartment  8 A. Furthermore, the oil pickup  132  is longitudinally over half the length of the oil sump in crank compartment  8 A, and as shown is approximately 65%. As such, the oil pickup remains in the oil sump even when in the extreme nose down scenario. 
         [0037]    Furthermore, due to the configuration of the camshaft tunnel  230  as described above, an excessive amount of oil will not pool there. That is, in the nose condition of  FIG. 10B , compartment  10 A is substantially filled at  22 B, and compartment  8 A is filled to the position  20 B above the oil pickup  132 . A small amount of oil pools to the level of  224 , but the remainder drains through transverse channel  234  and through apertures  236  A and  236 B back to the compartment OA. It is also the location of apertures  236 A and  236 B which allows for the side to side engine movement of  450 .

Technology Classification (CPC): 5