Patent Publication Number: US-7219645-B2

Title: Oil pump for a motorcycle

Description:
RELATED APPLICATION DATA 
     This application claims priority to now abandoned U.S. Provisional Patent Application Ser. No. 60/696,384 filed on Jul. 1, 2005 and incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention relates to an oil pump assembly for a motorcycle. More particularly, the invention relates to an oil pump assembly that includes two pumping units that are each directly driven by a cam shaft. 
     Motorcycles generally include a front wheel and a rear wheel that rotate about separate axles as the motorcycle moves. An engine combusts a fuel-air mixture to produce shaft power that is directed to the rear wheel to propel the motorcycle. Many of the moving parts of the engine require a lubricant, such as oil, that both lubricates the moving parts and provides some cooling for the parts. To provide the necessary oil, the motorcycle includes an oil pump that is driven by the engine. In most constructions, a gear, belt or chain interconnects the pumping element or elements and a cam shaft or a crankshaft to provide power to the pump. 
     SUMMARY 
     The present invention provides an oil pump assembly for a motorcycle. The oil pump attaches to an engine that includes a crankcase, a crankshaft, and two cam shafts. The oil pump assembly includes a pump body that supports two gerotors for rotation. One of the gerotors draws oil from sumps within the crankcase and the cam chest and pumps the oil to an oil reservoir, while a second gerotor pumps the oil from the reservoir, through an oil filter, an oil cooler, and to the engine components that require lubrication. Each gerotor is directly driven by one of cam shafts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a motorcycle including an engine embodying the present invention; 
         FIG. 2  is a partially broken away perspective view of the engine of  FIG. 1 ; 
         FIG. 3  is a perspective view of the engine of  FIG. 2  with an oil pump assembly removed; 
         FIG. 4  is an exploded view of a pump assembly; 
         FIG. 5  is front view of the oil pump assembly illustrating the various flow paths; and 
         FIG. 6  is a perspective view of a separator plate of the pump assembly of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
       FIG. 1  illustrates a motorcycle  10  that includes a front wheel  15 , a rear wheel  20 , an engine  25 , and a transmission  30 . The engine  25  combusts a fuel-air mixture to produce usable shaft power that in turn drives the rear wheel  20  to propel the motorcycle  10 . Generally, a spark-ignition internal combustion engine  25  is employed to power the motorcycle  10 . However, other constructions may include compression-ignition engines, rotary engines, or other types of engines that combust a fuel to produce usable shaft power. 
       FIG. 2  illustrates the engine  25  and transmission  30  of the motorcycle  10  of  FIG. 1 . The transmission  30  attaches to the engine  25  and extends rearward. The transmission  30  contains gearing or other components that allow for variation in the rotating speed of the rear wheel as compared to the rotating speed of the engine  25 , as is well known. 
     The engine  25  includes two cylinders  35  that extend above a crankcase  40 . Each cylinder  35  is angled slightly and includes a plurality of fins  45  that aid the cylinder  35  in cooling during engine operation. A cylinder head  50  is positioned on top of each cylinder  35  and cooperates with the cylinders  35  to define a combustion chamber  55 . Pistons  60 , disposed within each of the cylinders  35 , reciprocate in response to combustion within the combustion chambers  55  to rotate a crankshaft  65 . The crankshaft  65  connects to the rear wheel  20  via the transmission  30  and a drive linkage such as a chain, belt or shaft to allow the rear wheel  20  to rotate in response to combustion within the combustion chamber  55 . In addition, most transmissions  30  include a neutral position that allows the engine  25  to operate without rotating the rear wheel  20 . 
     The crankcase  40 , illustrated in  FIG. 3 , includes a housing  70  that defines cylinder attachment faces for each of the cylinders  35 . The crankcase  40  also at least partially defines a crank chamber  75  (see  FIG. 2 ) and a cam chamber  80  (see  FIG. 3 ). An oil pump face  85  that is substantially normal to the cylinder attachment faces surrounds the cam chamber  80  and defines an attachment surface for an oil pump assembly  90 . The oil pump assembly  90  (shown in  FIG. 4 ) attaches to the oil pump face  85  and substantially closes the cam chamber  80 . 
     A first cam shaft  95  and a second cam shaft (not shown) are supported for rotation substantially within the cam chamber  80  of the crankcase  40  and extend at least partially into the oil pump assembly  90  when the oil pump assembly is coupled to the crankcase  40 . Each cam shaft  95  is coupled to the crankshaft  65  such that the cam shafts  95  rotate in response to rotation of the crankshaft  65  at a speed that is directly proportional to the speed of the crankshaft  65 . In preferred constructions, a timing belt interconnects the crankshaft  65  and the cam shafts  95  to achieve the desired rotation. Each cam shaft  95  supports one or more cams that actuate one or more valves to admit a fuel-air mixture into the combustion chamber  55  of one of the cylinders  35  or to allow for the discharge of exhaust gases from the combustion chamber  55 , as is known in the art. 
     Turning to  FIG. 4 , the oil pump assembly  90  is illustrated in an exploded condition. The oil pump assembly  90  includes a pump cover  100 , a bypass valve  105 , a pressure sensor  110 , a pump body  115  that defines a scavenge aperture  120  and a lube oil aperture  125 , and a plurality of flow paths that will be discussed with regard to  FIG. 5 . The scavenge aperture  120  is substantially cylindrical and defines a substantially planar bottom surface  130  (shown in  FIG. 5 ). A first aperture  135  is formed in the planar surface  130  and provides for fluid communication between an oil sump in the crank chamber  75  and the scavenge aperture  120 . A second aperture  140  is formed as part of the cylindrical wall that defines the scavenge aperture  120  and provides for fluid communication between a sump in the cam chamber  80  and the scavenge aperture  120 . A third aperture  145  is formed in the planar surface  130  and provides for fluid communication between the scavenge aperture  120  and an oil reservoir  148  such as an oil tank, a hollow structural member, or another container. 
     A scavenge gerotor  150  is disposed within the scavenge aperture  120  and includes a first inner rotor  155  and a first outer rotor  160 . The first outer rotor  160  includes a cylindrical surface  165  that fits within the scavenge aperture  120  and allows the first outer rotor  160  to rotate with respect to the pump body  115 . The first outer rotor  160  also includes an internal space  170  defined by a plurality of teeth-receiving apertures. The first inner rotor  155  includes a central aperture  171  that engages the first cam shaft  95  such that the first inner rotor  155  rotates with the first cam shaft  95 . The first inner rotor  155  includes a plurality of teeth sized and shaped to fit within the teeth-receiving apertures of the outer rotor  160  such that the outer rotor  160  rotates in response to rotation of the inner rotor  155 . The rotational axis AA of the first cam shaft  95  is offset slightly from the center of the scavenge aperture  120  such that as the first outer rotor  160  rotates around the inner rotor  155 , gaps  175  open and close between the inner rotor  155  and the outer rotor  160 , as is well known in the gerotor art. 
     The lube oil aperture  125  is substantially cylindrical, is shallower than the scavenge aperture  120 , and defines a substantially planar bottom surface  180 . An intake aperture  185  is formed in the planar bottom surface  180  and provides fluid communication between the oil reservoir  148  and the lube oil aperture  125 . An outlet aperture  190  is formed in the planar bottom surface  180  and provides for fluid communication between the lube oil aperture  125  and an oil filter  195 . The lube oil aperture  125  receives a lube oil gerotor  200  that is similar to the scavenge gerotor  150  in that it includes a second inner rotor  205  and a second outer rotor  210 . The second outer rotor  210  fits within the lube oil aperture  125  but remains free to rotate with respect to the pump body  115 . The second inner rotor  205  includes a central aperture that receives the second cam shaft such that the second inner rotor  205  rotates with the second cam shaft. Rotation of the second inner rotor  205  produces a corresponding rotation of the second outer rotor  210  such that gaps  215  between the inner and outer rotors  205 ,  210  open and close at predefined locations around the lube oil aperture  125 . 
     As can be seen, the scavenge gerotor  150  is substantially thicker than the lube oil gerotor  200 . The increased thickness provides additional pumping capacity for the scavenge gerotor  150  that may be needed to draw lubricant upward from the sumps. In other constructions, the scavenge gerotor  150  and the lube oil gerotor  200  may be of similar thickness. 
     In some constructions, a separator plate  220  (shown in  FIG. 6 ) covers the exposed end faces of the gerotors  150 ,  200  to inhibit leakage out of the gerotors  150 ,  200  in an axial direction. The separator plate includes two circular apertures  222  and three flow apertures  223   a ,  223   b , and  223   c . The circular apertures  222  allow for the lubrication of the cam shafts. The first flow aperture  223   a  allows for suction flow into the scavenge gerotor  150  from the crankcase sump  236 . The second aperture  223   b  allows for suction flow into the scavenge gerotor  150  from the cam chamber sump  237 . The third aperture  223   c  allows for suction flow into the lube oil gerotor  200 . Of course other constructions may rely on features other than the separator plate  220  to inhibit this unwanted leakage. The pump cover  100  attaches to the pump body  115  to close any exposed flow paths, to inhibit unwanted axial movement of the components, and to retain the separator plate  220  in the desired position. In some constructions, a gasket  221  may be positioned between the pump body  115  and the pump cover  100  to improve the seal therebetween. 
     With continued reference to  FIG. 4 , the bypass valve  105  includes a valve plunger  225 , a biasing member  230 , and a plug  235 . The plunger  225  fits within an aperture that is formed in the pump body  115  and is movable between a closed position and an open or bypass position. The biasing member  230 , in the form of a compression spring, engages the valve plunger  225  and biases it toward the closed position. The plug  235  engages the pump body  115  to close the aperture, and provides a surface that engages the biasing member  230 . In some constructions, the plug  235  includes an o-ring, a gasket, or other sealing device that enhances the ability of the plug  225  to seal the aperture and inhibit oil leakage. 
     The pressure sensor  110  attaches to the pump body  115  and includes a pressure-sensing element that is in fluid communication with the lubricant within the pump body  115  as will be discussed with regard to  FIG. 5 . In preferred constructions, the pressure sensor  110  includes a pressure switch that is set to switch when a drop in pressure below a predetermined value occurs. If the pressure drops below a predetermined value, the switch actuates to activate an indicator such as a warning light for the operator. Thus, the pressure sensor  110  can be used to warn the motorcycle  10  operator of low lubricant pressure conditions that may be harmful to the engine  25 . 
     With reference to  FIG. 5 , the various flow paths and operation of the oil pump assembly  90  will be described. During engine operation, the crankshaft  65  rotates in response to combustion within the combustion chambers  55 . The rotation of the crankshaft  65  causes rotation of the cam shafts  95 , which in turn causes rotation of both the scavenge gerotor  150  and the lube oil gerotor  200 . As the scavenge gerotor  150  rotates, the first inner and first outer rotors  155 ,  160  begin to separate adjacent the first aperture  135  and adjacent the second aperture  140 . The scavenge gerotor  150  produces a partial vacuum as the space between the first inner rotor  155  and the second inner rotor  160  increases. The partial vacuum draws oil, or other fluids (e.g., air), from the crankcase sump  236  through aperture  135  and from the cam chamber sump  237  through aperture  140  into the space between the first inner rotor  155  and the first outer rotor  160 . Continued rotation of the gerotor  150  directs the fluid trapped in the space to the third aperture  145 . From the third aperture  145 , the fluid flows along a first internal flow path  240  that is formed within the pump body  115  to a first body outlet  245 . From the first body outlet  245 , the fluid flows through a conduit  238 , such as an oil line to the oil reservoir  148 . Thus, the scavenge gerotor  150  functions to draw oil, or other fluids, from collection points within the engine  25  and deliver that fluid to the oil reservoir  148  where it can be reused to lubricate and cool engine components. 
     The lube oil gerotor  200  is oriented such that the second inner rotor  205  and the second outer rotor  210  begin separating in the area over the intake aperture  185 . As the rotors  205 ,  210  separate, a partial vacuum is created, which draws fluid from the oil reservoir  148 , through an external oil line  246  or other flow path, and through a second internal flow path  250 . The fluid rotates around the lube oil aperture  125  with the second rotors  205 ,  210  until the lubricant is adjacent the outlet aperture  190 . As the space between the second inner rotor  205  and second outer rotor  210  approaches the outlet aperture  190 , the second inner rotor  205  and the second outer rotor  210  move closer to one another, thus reducing the volume between them. As the volume is reduced, the fluid is forced through the outlet aperture  190  and into a third internal flow path  255 . 
     The third internal flow path  255  is at least partially formed in the crankcase  40  and leads to the oil filter  195 . The oil filter  195  removes small particles and substances that may be harmful to the engine components. From the filter  195 , the oil flows into an oil cooler  260  that includes a heat exchanger that cools the oil. The cooled oil is better suited to cool and lubricate the moving components of the engine  25 . From the oil cooler  260 , the oil reenters the pump body  115  via a first body inlet  265 , and flows through a series of lubrication channels  270  that direct the oil to the locations were lubrication and cooling is desired. For example, the oil can be directed to bearings that support the crankshaft  65  and/or bearings that support the cam shafts  95  to provide the desired lubrication and cooling. The directly driven gerotors  150 ,  200  provide sufficient flow capacity and pressure output to allow pressurized lubrication at these bearings. After lubricating the desired components, the oil collects in one of the crankcase sump and the cam case sump for collection and reuse by the scavenge gerotor  150 . 
     A bypass aperture  275 , formed as part of the pump body  115 , leads to a bypass flow path  276  between the third internal flow path  255  (lube oil gerotor outlet) and the second internal flow path  250  (lube oil gerotor intake), The bypass valve  105  is positioned such that the plunger  225  is biased to close the bypass aperture  275 . However, when the force generated by the high-pressure lubricant in the third internal flow path  255  overcomes the force produced by the compression spring, the plunger  225  begins moving away from the bypass aperture  275 . With the plunger  225  moving away from the bypass aperture  275 , lubricant from the third internal flow path  255  is bypassed to the second internal flow path  250 . 
     Generally, the discharge pressure of the scavenge gerotor  150  and the lube oil gerotor  200  is a function of engine speed with higher engine speeds producing higher discharge pressures. At high engine speeds, excess high-pressure lubricant is bypassed from the outlet of the lube oil gerotor  200  to the intake aperture  185  adjacent the lube oil gerotor  200 , thereby holding the delivered flow constant at high speeds. The increased flow and pressure at the intake aperture  185  increases the cavitation speed of the lube oil gerotor  200  and therefore, could increase the volumetric efficiency of the gerotor  200  at these higher speeds. 
     As illustrated in  FIG. 5 , the pressure sensor  110  is in fluid communication with one of the series of lubrication channels  270  that direct lubricant to the points that require lubrication or cooling. As such, the pressure sensor  110  is able to detect a pressure drop in these flow paths  270 . A pressure drop in these flow paths  270  could be harmful to the engine  25  as low-pressure would indicate that some or all of the moving parts may be receiving inadequate lubrication and cooling. 
     The arrangement of the oil pump assembly  90  illustrated herein allows for the use of a bypass valve  105  that allows for supercharging of the lube oil gerotor inlet. In addition, the directly driven gerotors  150 ,  200  have increased reliability over other mechanically driven oil pump arrangements and provide additional capacity that allows for direct pressurized lubrication of the bearings, rather than the more common splashed lubrication. Furthermore, the positioning of the apertures that lead into and out of the pump body  115  are such that straight fittings can be employed at all locations. 
     The oil pump assembly  90  illustrated herein includes several inlets and outlets that provide for connection between components external to the pump (e.g., oil cooler  260 , oil filter  195 , etc.). The arrangement of the pump assembly  90  is such that straight fittings  280  can be employed at all inlets and outlets, thereby eliminating the need for any angled fittings. The fittings  280  may include pipe fittings, compression fittings, hose fittings, and the like. 
     Thus, the invention provides, among other things, a new and useful oil pump assembly  90  for a motorcycle  10 . More particularly, the invention provides a new and useful oil pump  90  that includes two gerotors  150 ,  200 , each directly driven by one of the cam shafts  95 . Various features and advantages of the invention are set forth in the following claims.