Abstract:
An engine includes a crankcase defining a crankcase space, a first shaft disposed at least partially within the crankcase and supported for rotation by the crankcase, and an oil pump coupled to the first shaft and operable to draw low pressure oil from the crankcase and discharge a flow of high pressure oil. A pressure relief path is positioned to selectively receive a portion of the flow of high pressure oil and a pressure relief assembly is coupled to the pressure relief path and is arranged to spray the portion of the high pressure flow that passes through the pressure relief passage against an interior surface of the crankcase.

Description:
RELATED APPLICATION DATA 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/761458 filed Feb. 6, 2013, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    Some current engines run hotter than desired per application heat test specification. The oil pump size for these engines is large relative to displacement and bypasses significant volumes of oil during normal operation. The large oil pump size is an advantage in terms of providing sufficient oil to the engine components when the engine oil is hot and the engine is operating at a low speed. The large pump also compensates for bearing wear over time and compensates for larger bearing clearance tolerance stack-up that may exist in some engines. 
       SUMMARY 
       [0003]    In one construction, the invention provides an engine that includes a crankcase defining a crankcase space, a first shaft disposed at least partially within the crankcase and supported for rotation by the crankcase, and an oil pump coupled to the first shaft and operable to draw low pressure oil from the crankcase and discharge a flow of high pressure oil. A pressure relief path is positioned to selectively receive a portion of the flow of high pressure oil and a pressure relief assembly is coupled to the pressure relief path and is arranged to spray the portion of the high pressure flow that passes through the pressure relief passage against an interior surface of the crankcase. 
         [0004]    In another construction, the invention provides an engine that includes a crankcase having a first end, a second end, and a crankcase space. A first cylinder is coupled to the first end and first piston is operable to reciprocate within the crankcase. A crankshaft is rotatable in response to reciprocation of the first piston, a camshaft is rotatable in response to rotation of the crankshaft, and an oil pump is operable in response to the rotation of the camshaft to draw low pressure oil from the crankcase space and deliver a flow of high pressure oil. A pressure relief path is positioned to selectively receive a portion of the flow of high pressure oil and a pressure relief assembly is coupled to the pressure relief path and is arranged to spray the portion of the high pressure flow that passes through the pressure relief passage against the second end of the crankcase. 
         [0005]    In yet another construction, the invention provides a method of cooling an engine lubricant within an engine. The method includes reciprocating a piston within a cylinder, drawing low pressure oil from a crankcase space into an oil pump in response to the reciprocating piston, and discharging a flow of high pressure oil from the oil pump. The method also includes selectively directing a portion of the high pressure oil to a pressure relief path and discharging the portion of high pressure oil through a nozzle, the nozzle operable to reduce the pressure of the high pressure oil and to spray the oil onto a surface of a crankcase. 
         [0006]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is an isometric sectional view of the spray cool oil system in accordance with an exemplary embodiment; 
           [0008]      FIG. 2  is another isometric sectional view of the spray cool oil system in accordance with an exemplary embodiment; 
           [0009]      FIG. 3  is another isometric sectional view of the spray cool oil system in accordance with an exemplary embodiment; 
           [0010]      FIG. 4  is an enlarged perspective view of a portion of the engine of  FIG. 3 ; and 
           [0011]      FIG. 5  is a front view of a prior art engine. 
       
    
    
       [0012]    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. 
       DETAILED DESCRIPTION 
       [0013]      FIG. 5  illustrates an engine  10  including a crankcase  15  having a first side  20  and a second side  25  that is substantially opposite the first side  20 . A first cylinder  30  extends from the first side  20  at an oblique angle with respect to a vertical axis  35  (vertical in  FIG. 4 ) and a second cylinder  40  extends from the first side  20  at an opposite oblique angle. Thus, the cylinders  30 ,  40  define a V-shaped or V-twin arrangement with the vertical axis  35  bisecting the “V”. A first piston  45  is disposed within the first cylinder  30  to define a first piston-cylinder and a second piston (not shown) is disposed within the second cylinder  40  to define a second piston-cylinder. A crankshaft  50  extends from the crankcase  15  and is coupled to the first piston  45  and the second piston as is known in the art. 
         [0014]    Each of the cylinders  30 ,  40  includes a plurality of exterior fins  55  that aid in cooling during engine operation. As is known to those of skill in the art, the cylinders  30 ,  40  are the hottest point of the engine  10  with the second side  40  of the crankcase  15  being substantially cooler during engine operation. In the illustrated construction, the cylinders  30 ,  40  are formed as part of the crankcase  15 . However, other constructions may include separate cylinders  30 ,  40  that attach to the crankcase  15 . 
         [0015]    Turning to  FIG. 3 , a portion of the engine  10  is illustrated with a portion of the crankcase  15  broken away to better illustrate the interior. As can be seen, the engine  10  further includes a camshaft  60 , an oil pump  65  and a pressure relief assembly  70 . The camshaft  60  is disposed parallel to the crankshaft  50  with the crankcase  15  supporting both for rotation. Gears  75  on the camshaft  60  and the crankshaft  50  mesh to produce rotation of the camshaft  60  at a desired speed with respect to the crankshaft  50 . For example, a ratio of two to one with the camshaft  60  rotating once for every two revolutions of the crankshaft  50  is common. Cams  80  are coupled to the camshaft  60  and are arranged to operate the various intake and exhaust valves of the piston-cylinders. In the illustrated construction, four cams  80  are provided with each cam  80  operating either an intake valve or an exhaust valve for one of the piston-cylinders. 
         [0016]    The oil pump  65  is disposed at one end of the camshaft  60  and is supported for rotation with the camshaft  60 . In the illustrated construction, a rotary gear pump is employed as the pump  65 . In preferred constructions, the oil pump  65  is positioned at or near the lowest operating point of the engine  10  to reduce the length of suction required to draw low pressure oil into the pump  65 . However, other arrangements are possible. In the illustrated construction, the engine  10  is arranged with the crankshaft  50  in a vertical orientation and the oil pump  65  at the bottom of the crankcase  15 . 
         [0017]    The pressure relief assembly  70 , best illustrated in  FIG. 4  includes a pressure relief path  85 , a plug  90 , a biasing member  95 , and a nozzle  100 . The pressure relief path  85  includes a first diameter portion  105  and a second larger diameter portion  110  downstream of the first diameter portion  105 . The interface between the first diameter portion  105  and the second diameter portion  110  defines a plug seat  115  that is arranged to receive the plug  90  and define a seal therebetween. The plug seat  115  may be tapered, rounded, or otherwise formed to enhance the seal between the plug  90  and the plug seat  115  as may be desired. 
         [0018]    The plug  90  includes a tapered outer surface  120  that is arranged to engage the plug seat  115  to form a seal between the plug seat  115  and the plug  90 , thereby inhibiting the unwanted passage of oil. The plug  90  also includes an inner surface  125  that is sized and arranged to receive a first end  130  of the biasing member  95 . 
         [0019]    The nozzle  100  is sized to fixedly engage the second diameter portion  110  to substantially close the end opposite the plug seat  115 . One or more apertures  135  are formed in the nozzle  100  to produce the desired pressure drop and spray pattern  140  during operation, as will be discussed below. The nozzle  100  includes an inner surface  145  arranged to receive and support a second end  150  of the biasing member  95 . 
         [0020]    The biasing member  95  is positioned between the plug  90  and the nozzle  100  and acts to bias the plug  90  into sealed engagement with the plug seat  115 . In the illustrated construction, the biasing member  95  includes a coil spring with other biasing members  95  or arrangements being possible. The biasing member  95  is selected to maintain the plug  90  in the closed position until the pressure of the oil against the plug  90  exceeds a predetermined value. When the oil pressure is above the predetermined value, the plug  90  moves to an open position and high pressure oil flows to the nozzle  100  and out the nozzle aperture  135 . 
         [0021]    During engine operation, combustion of a fuel occurs within the piston-cylinders as is known in the art. The combustion produces reciprocating movement of the piston  45  which is converted to rotation of the crankshaft  50  and the camshaft  60  as is known in the art. Rotation of the camshaft  60  rotates the oil pump  65 . As the oil pump  65  rotates, low pressure oil is drawn into the oil pump  65  and then discharged at a high pressure (between about 20 psi and 100 psi). The high pressure oil flows along a flow path  155  to an oil filter  160  (shown in  FIG. 4 ). The pressure relief path  85  is connected to the flow path  155  at a point between the oil pump  65  and the filter  160 . 
         [0022]    When the engine  10  is operating at lower power levels or speeds, the oil pump  65  produces oil at a pressure low enough to assure that the pressure relief assembly  70  remains in a closed position. At some operating conditions, such as high speed operation or high power output operation, the pressure of the oil discharged by the oil pump  65  may exceed a predetermined pressure level. When this occurs, the oil pressure overcomes the force applied to the plug  90  by the biasing member  95  and the plug  90  moves toward an open position. When opened, a portion of the high pressure oil flows through the pressure relief path  85  and through the nozzle  100 . 
         [0023]    As illustrated in each of  FIGS. 1-3 , the nozzle  100  is arranged to discharge the oil in a fanned pattern  140  that impinges against a wall  165  of the crankcase  15 . The wall  165  is selected to aid in the cooling of the oil as it is the wall  165  opposite the cylinders  30 ,  40  and therefore naturally operates at a temperature that is relatively cool when compared to the opposite end (cylinder or first end  20 ) of the crankcase  15 . Fins  170  are formed on the exterior of the crankcase  15  adjacent this wall  165  to further aid in cooling the area, thereby further cooling the oil within the crankcase  15 . The nozzle  100  also throttles the oil to a pressure that is about equal to the pressure within the crankcase (atmospheric pressure or lower), thereby cooling the oil. 
         [0024]    Thus, the nozzle  100  sprays the hot bypassed oil against the relatively cool wall  165  of the second side  25  of the crankcase  15 . The oil will be cooled in several ways. Initially, the pressure drop as the oil escapes the pressure relief path  85  and moves into the internal atmospheric pressure of the crankcase  15  will produce a cooling effect for the oil. Next, forced convection between the oil as it is sprayed and the internal atmosphere of the crankcase  15  further cools the hot oil. The wider fanned pattern  140  enhances this cooling effect. Next, the hot oil directly contacts the inner surface of the crankcase  15  and conduction directs heat from the oil to the cooler wall  165  of the crankcase  15 . Finally, the fanned spray pattern  140  is such that the surface area of the crankcase  15  impacted by the oil and through which the oil is cooled is much larger than the area employed in internal pump bypass designs, thereby further enhancing the cooling efficiency. 
         [0025]    In some constructions, cooling air can be directed from the engine blower or fan to the external fins  170  to further enhance the cooling efficiency of the system. 
         [0026]    Various features and advantages of the invention are set forth in the following claims.