Abstract:
A high-performance oil pump for pumping oil in an internal combustion engine that eliminates or greatly reduces cavitation in the oil pump, thereby increasing the efficiency and performance of the oil pump. The present invention provides a housing having an inlet for receiving a supply of oil and an outlet for discharging the oil. At least two gears rotatably and matingly are disposed within the housing for pumping the oil from the inlet to the outlet. A pressure regulation circuit is disposed within the housing for balancing oil flow pressure between the inlet and the outlet by redirecting a portion of the oil from the outlet to the inlet when said oil flow pressure reaches a predetermined level at the outlet in order to reduce or eliminate cavitation of oil in the oil pump.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application which claims the benefit of U.S. patent application Ser. No. 12/262,391, which was filed on Oct. 31, 2008, which claims the benefit of priority from U.S. Provisional Patent Application Ser. No. 61/001,176, which was filed Oct. 31, 2007. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to oil pumps, and in particular, a high-performance external involute gear-style oil pump that eliminates or greatly reduces cavitation in the oil pump, thereby increasing the efficiency and performance of the oil pump. 
     BACKGROUND OF THE INVENTION 
     Cavitation is an undesirable condition that often occurs in external involute gear-style oil pumps that are commonly used on internal combustion engines. Cavitation occurs when the static pressure at any point in the fluid flow of the fluid being pumped becomes less than the fluid&#39;s vapor pressure, thereby creating vapor bubbles in the inlet fluid stream. When this situation arises in an oil pump, vapor bubbles in the inlet oil stream reach the high-pressure side or outlet side of the oil pump and implode, thereby causing noise, vibration, and damage to any surface of the oil pump in which the imploding bubbles touch. The effects of cavitation can range from a loss of oil pump efficiency, a reduction in the oil pumps&#39; output, or more serious effects, such as noise, vibration, and damage to the oil pump&#39;s components. 
     The onset of cavitation is determined by the oil pump&#39;s speed, capacity, and inlet design. In addition, external involute gear-style oil pumps tend to cavitate at relatively low operating speeds as compared to other pump designs. Cavitation has caused lubrication issues with many high-performance engines, since many of those engines utilize an external involute gear-style oil pump. Because of this condition, many high-performance engines utilize a dry sump oiling system; however, such dry sump oiling systems are more expensive and complex, thereby increasing the cost and maintenance of such systems. 
     SUMMARY OF THE INVENTION 
     The present invention provides a high-performance oil pump for pumping engine oil in an internal combustion engine in order to reduce or eliminate cavitation of the oil in the oil pump. The present invention provides a housing having an inlet for receiving oil and an outlet for discharging oil. At least two gears are rotatably and matingly disposed within a pumping chamber of the housing for pumping oil from the inlet to the outlet. An inlet passageway extends from the inlet to the inlet side of the pumping chamber, and an outlet passageway extends from an outlet side of the pumping chamber to the outlet. A pressure regulating circuit disposed within the housing redirects oil from the outlet side of the pumping chamber to the inlet passageway when the pressure differential between the outlet side of the pumping chamber and the inlet side of the pumping chamber exceeds a predetermined level in order to reduce or eliminate cavitation of oil in the oil pump. 
     The pressure regulation circuit of the present invention provides a pressure relief valve having a spool valve structure disposed within the bore of the housing. A redirect outlet passageway communicates with the outlet side of the pumping chamber and the pressure relief valve. A redirect inlet passageway communicates with the pressure relief valve and the inlet passageway. The pressure relief valve is moveable between a normally closed position, wherein oil is prevented from passing from the redirect outlet passageway to the redirect inlet passageway, and an open position, wherein oil is allowed to pass from the redirect outlet passageway to the redirect inlet passageway. The relief valve is biased in the closed position and moves from the closed position to the open position when the pressure differential between the redirect outlet passageway and the redirect inlet passageway exceeds a predetermined level. 
     The inlet of the housing provides an opening that is communicatable with a supply of oil, and the opening of the inlet has a larger diameter than the inlet passageway. A strainer is removably connected to and extends across the inlet for filtering oil and minimizing a pressure drop of oil prior to entering the inlet passageway. The inlet passageway has a longitudinal axis that extends directly from the inlet to the inlet side of the pumping chamber. 
     A venting passageway extends from the inlet to the bore in the housing for receiving the relief valve in order to maintain atmospheric pressure on both sides of the relief valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various other uses of the present invention will become more apparent by referring to the following detailed descriptions and drawings, and which: 
         FIG. 1  is an exploded view of the high-performance oil pump of the present invention; 
         FIG. 2  is a sectional view of the high-performance oil pump of the present invention; 
         FIG. 3  is a top plan view of the oil pump cover of the high-performance oil pump of the present invention; 
         FIG. 4  is a top plan view of the oil pump body of the high-performance oil pump of the present invention; 
         FIG. 5  is a sectional view of the oil pump cover of the high-performance oil pump of the present invention; 
         FIG. 6  is a sectional view of the high-performance oil pump of the present invention; 
         FIG. 7  is a top plan view of the high-performance oil pump of the present invention; 
         FIG. 8  is an isometric view of the oil pump cover of the high-performance oil pump of the present invention; and 
         FIG. 9  is an isometric view of the oil pump of the high-performance oil pump of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, the present invention will now be described in detail with reference to the disclosed embodiments. 
       FIGS. 1-10  illustrate a high-performance oil pump  10  of the present invention for reducing or eliminating cavitation of oil in the oil pump  10 . The oil pump  10  provides a housing  12  having an oil pump body  14  and an oil pump cover  16 . The oil pump cover  16  has an inlet  18  formed therein for receiving oil (not shown) from an oil supply reservoir (not shown), such as an oil pan from an internal combustion engine (not shown). The inlet  18  is in communication with a hollow pumping chamber  20  formed in the oil pump body  14  of the housing  12 . An outlet  22  is also formed in the oil pump body  14  and is in communication with the pumping chamber  20 . A pair of gears  24 ,  26  are rotatably disposed within the pumping chamber  20  of the oil pump body  14  and are driven by the engine. The gears  24 ,  26  pump oil from the inlet  18  to the outlet  22  of the housing  12 , and the outlet  22  of the housing  12  is connected to and communicates with an engine block of the engine so as to provide oil to the engine block. A pressure regulation circuit  28  disposed within the housing  12  balances oil flow pressure between the inlet  18  and the outlet  22  by redirecting a portion of the oil from the outlet  22  to the inlet  18  of the oil pump  10  when the oil flow pressure differential between the outlet  22  and the inlet  18  reaches a predetermined level. By allowing oil to flow from the outlet  22  to the inlet  18 , especially under high speed engine conditions, an appropriate amount of oil is supplied to the inlet  18 , thereby ensuring a proper supply of oil to the pumping chamber  20  and reducing or avoiding cavitation of the oil in the oil pump  10 . By reducing or eliminating cavitation, the efficiency and performance of the oil pump  10  is increased. 
     In order to provide the housing  12  of the present invention with the appropriate structural strength and weight, the oil pump body  14  and the oil pump cover  16  of the housing  12  may be fabricated from billet 6061-T6 aluminum, which is hard-coated and anodized for durability. Although the noted aluminum is an ideal material for the housing  12  of the oil pump  10 , it should be noted that the present invention is not limited to such material, but rather, various other materials having similar strength and weight properties can be utilized. 
     The oil pump cover  16  has a substantially cylindrical configuration with the inlet  18  formed at an open end  30  of the oil pump cover  16 . The initial opening  32  of the inlet  18  extends across almost the entire width of the end  30  of the oil pump cover  16 . The initial opening  32  of the inlet  18  is relatively large and sized accordingly in order to reduce flow restriction of the oil. A steel mesh strainer  34  is seated within an annular recess  36  in the inlet  18  of the oil pump cover  16 , and a removable retaining ring  38  is also seated in an annular recess  40  in the inlet  18  of the oil pump cover  16  so as to secure the strainer  34  in the oil pump cover  16 . Since an oil filter (not shown) is typically downstream from the oil pump  10 , the oil being supplied from the oil pan to the oil pump  10  is not filtered. Thus, the strainer  34  filters any contaminates in the oil and prevents such contaminates from entering the oil pump  10  of the present invention while minimizing the amount of pressure drop across the strainer  34 . The retaining ring  38  can be easily removed from the oil pump cover  16 , thereby allowing regular maintenance to be performed on the strainer  34 . For example, the strainer  34  can be removed, cleaned, and replaced in the oil pump cover  16 . Since the strainer  34  can provide restriction of the oil flow into the inlet  18 , the initial opening  32  of the inlet  18  from the oil pump cover  16  is relatively large, as previously mentioned, to ensure for the proper flow of oil into the inlet  18 . 
     For oil to be pumped from the oil supply to the pumping chamber  20 , the inlet  18  in the oil pump cover  16  provides an inlet passageway  42  extending from and in communication with the initial opening  32  of the inlet  18  of the oil pump cover  16 . Although the inlet passageway  42  is smaller in diameter than the initial inlet opening  32 , the inlet passageway  42  is still larger than most conventional designs in order to reduce flow restriction of the oil. The length of the inlet passageway  42  is also designed to be as short a distance as possible to the pumping chamber  20  in order to reduce the restriction of flow to the incoming oil. Again, the initial opening  32  is larger than the inlet passageway  42  to ensure that there is no flow resistance caused by the strainer  34 . The inlet passageway  42  has a longitudinal axis that is laterally offset from the longitudinal axis of the oil pump cover  16 , and the inlet passageway  42  extends substantially straight through the oil pump cover  16  to communicate with an inlet side  43  of the hollow pumping chamber  20  provided in the oil pump body  14 . Thus, the inlet  18  provides communication between the oil supply and the pumping chamber  20  of the housing  12 . 
     In order to pump oil from the oil supply through the inlet  18  and out through the outlet  22 , the oil pump cover  16  has a substantially rectangular stepped configuration, wherein a substantially flat mating surface  44  on the oil pump cover  16  abuts a substantially flat mating surface  46  on the oil pump body  14 . Four apertures  48  extend through the mating surface  44  of the oil pump cover  16  and are correspondingly aligned with four threaded apertures  50  in the mating surface  44  of the oil pump body  14 . Four conventional threaded fasteners  51  extend through the apertures  48  and thread into apertures  50  to secure the oil pump cover  16  to the oil pump body  14 . 
     The gears  24 ,  26  of the oil pump  10  are disposed within the hollow pumping chamber  20  of the oil pump body  14  wherein the pumping chamber  20  is open to the mating surfaces  44 ,  46  of the oil pump body  14  and the oil pump cover  16 . The pair of gears  24 ,  26  are external involute gears that are substantially similar and are designed to mesh together in a complementary manner. The first gear  24  has a throughbore extending along its longitudinal axis for receiving an idler shaft  52  wherein the first gear  24  is press fit onto the idler shaft  52 . The idler shaft  52  has one of its ends  54  received within a blind bore  56  provided in the mating surface  44  of the oil pump cover  16 . A small trough  55  provided on the mating surface  44  of the oil pump cover  16  directs oil from the pumping chamber  20  to the blind bore  56  to lubricate the end  54  of the idler shaft  52 . The other end  58  of the idler shaft  52  extends through a throughbore  60  in the oil pump body  14 . The throughbore  60  has a stepped-diameter to secure the idler shaft  52  in the housing  12 . The first gear  24  is then free to rotate with the idler shaft  52  within the pumping chamber  20  of the oil pump body  14 . 
     The second gear  26  also has a throughbore extending along the longitudinal axis of the second gear  26 . A drive shaft  62  is inserted through the throughbore of the second gear  26  wherein the second gear  26  is press-fit to the drive shaft  62 . One end  64  is seated within a blind bore  66  extending from the mating surface  44  of the oil pump cover  16 . A small trough  57  is provided on the mating surface  44  of the oil pump cover  16  to direct oil from the pumping chamber  20  to the blind bore  66  to lubricate the end  64  of the drive shaft  62 . A throughbore  68  extending through the oil pump body  14  receives the drive shaft  62 . A free end  70  of the drive shaft  62  extends outward beyond the oil pump body  14  and is coupled to a portion of the engine, such as a crankshaft or a camshaft. The second gear  26  is disposed within the pumping chamber  20  of the oil pump body  14  and rotates with the drive shaft  62 . The first and second gears  24 ,  26  are situated such that when the second gear  26  is driven by the drive shaft  62 , the second gear  26  rotates in a meshing and complementary fashion with the first gear  24 . Since the drive shaft  62  is connected to the camshaft or crankshaft of the engine, the speed at which the gears  24 ,  26  rotate is in direct relation to the speed of the engine. 
     To pump the oil from the inlet  18  through to the outlet  22 , an outlet passageway  72  extends from an outlet side  73  of the pumping chamber  20  of the oil pump body  14  to an outlet opening  78  which extends to an outside landing  74  on the oil pump body  14 . The outlet opening  78  is larger in diameter than the outlet passageway  72  and is relatively large and sized accordingly in order to reduce the restriction of oil flow. A through-hole  76  extending from the opposite side of the oil pump body  14  extends into the outlet opening  78  of the oil pump body  14 . The through-hole  76  allows for a fastener (not shown) to extend up through the through-hole  76 , thereby connecting the landing  74  of the oil pump body  14  directly to the engine block of an engine. This allows the oil pump  10  of the present invention to pump the oil from the inlet  18  to the outlet  22  and into the engine block of the engine. 
     In order to regulate and balance oil flow pressure between the outlet  22  and the inlet  18  of the oil pump, the pressure regulation circuit  28  provides a relief valve  80  slidably disposed within the oil pump cover  16 . The relief valve  80  is movable between a normally closed position, wherein oil is prohibited from flowing from the outlet  22  to the inlet  18 , and an open position, wherein oil is allowed to flow from the outlet  22  to the inlet  18  to ensure a proper supply of oil to the pumping chamber  20 , thereby reducing or avoiding cavitation of the oil in the oil pump  10 . The relief valve  80  is disposed within the oil pump cover  16  in a blind bore  82  extending through an integral boss  84  formed on the outside of the oil pump cover  16 . The relief valve  80  provides a spool valve  86  slidably disposed within the blind bore  82  for movement between the closed position and the open position. The spool valve  86  has a larger diameter portion  88 , which is slightly smaller than the diameter of the blind bore  82 , and a smaller diameter portion  90  that is integral with and extends from the larger diameter portion  88  of the spool valve  86 . The smaller diameter portion  90  of the spool valve  86  may abut the end of the blind bore  82  in order to prohibit further movement of the spool valve  86  at that end of the bore  82 . The larger diameter portion  88  of the spool valve  86  has a blind bore  92  extending from the end of the spool valve  86 . A helical compression spring  94  is inserted into the bore  92  of the spool valve  86 , wherein a portion of the helical compression spring  94  extends outward from the spool valve  86  and is housed within the blind bore  82  in the oil pump cover  16 . A plug  96  is threaded into corresponding threads provided in the opening of the blind bore  82  in the boss  84  of the oil pump cover  16 . The plug  96  secures the spool valve  86  and the gears  24  within the blind bore  82  in the oil pump cover  16  and acts as an abutment to one end of the compression spring  94 . 
     In order for the relief valve  80  to redirect oil from the outlet  22  to the inlet  18  when the flow pressure differential between the outlet  22  and the inlet  18  reaches a predetermined level, a redirected outlet passageway  98  is formed on the mating surface  44  of the oil pump cover  16  and is in communication with the outlet side  73  of the pumping chamber  20 . This redirected outlet passageway  98  extends from the pumping chamber  20  to the end of the blind bore  82  in the oil pump cover  16  that houses the relief valve  80 . This provides communication between the outlet  22  and the blind bore  82  housing the relief valve  80 . Thus, the outlet pressure of the oil is constantly in communication with the relief valve  80 , and when the outlet pressure becomes great enough to overcome the force of the compression spring  94  on the spool valve  86 , the spool valve  86  will begin to move against the force of the compression spring  94 . The compression spring  94  has a predetermined spring force that corresponds to a desired outlet pressure wherein oil from the outlet  22  is redirected to the inlet  18 . 
     When the outlet pressure becomes too great, the spool valve  86  moves to the open position, and oil is allowed to flow from the outlet  22  to the inlet  18  of the oil pump  10 . To redirect such flow of oil, a redirected inlet passageway  95  is provided by a pair of blind bores  100  that extends between the inlet passageway  42  and the blind bore  82  that houses the relief valve  80 . The blind bores  100  have longitudinal axes that are substantially perpendicular to the longitudinal axis of the inlet passageway  42 . Thus, the redirected inlet passageway  95  provides communication from the blind bore  82  housing the relief valve  80  to the inlet passageway  42 . At the end of the pair of blind bores  100  that extends outward from the oil pump cover  16 , a plug  101  is threaded into the oil pump cover  16  to maintain the oil within the oil pump  10 . Thus, when the outlet pressure becomes too great and the spool valve  86  moves to the open position, the oil from the redirected outlet passageway  98  travels into the blind bore  82  housing the relief valve  80  and into the redirected inlet passageway, which allows for oil to travel back to the inlet passageway  42 . This supply of oil is added to the normal supply of oil in the inlet  18 , thereby providing an additional supply of oil to the gears  24 ,  26  within the pumping chamber  20  of the housing  12 . This additional supply of oil ensures a sufficient supply of oil so as to reduce or eliminate the onset of cavitation within the oil pump  10 . The redirected outlet passageway and the redirected inlet passageway are substantially straight and direct so as to reduce the length and turns within the redirected passageways. This assists in avoiding any flow restriction of the oil. 
     It should also be noted that a small venting passageway  102  extends from the inlet  18  to the backside of the spool valve  86 . This allows atmospheric pressure to be provided on the backside of the spool valve  86  so that the spool valve  86  can move freely between the open and closed positions, thereby avoiding vacuum within the blind bore housing the spool valve  86 . 
     In operation, the initial opening  32  of the inlet  18  of the oil pump  10  of the present invention may be located within an oil pan of an engine, and the outlet  22  of the oil pump  10  may be connected to the engine block of an engine. Once the engine begins operating, the drive shaft  62  of the oil pump  10  is driven by the crankshaft or camshaft of the engine. The drive shaft  62  drives the second gear  26 , which, in turn, drives the first gear  24 . As the gears  24 ,  26  rotate, the un-meshing of the gears  24 ,  26  create a local drop in pressure, which draws the oil into the inlet  18  of the oil pump  10  from the oil pan. The incoming oil flows into the pumping chamber  20  due to the un-meshing of the gears  24 ,  26 . As the oil pump  10  speed increases with the engine speed, so does the speed of the gears  24 ,  26 , and, as a result, the fill time of the oil into the pumping chamber  20  is reduced to the point at which the incoming oil does not have enough time to fill the pumping chamber  20 . This is when cavitation may start to occur. 
     In order to reduce or eliminate the onset of cavitation, the outlet pressure of the oil begins to reach a level wherein the spool valve  86  begins to move from the first or closed position, wherein oil is prohibited from flowing from the outlet  22  to the inlet  18 , to the second or open position, wherein a portion of the oil from the outlet  22  is allowed to flow to the inlet  18 . As the outlet pressure forces the spool valve  86  against the compression spring  94 , the spool valve  86  continues to move toward the open position until the larger diameter portion  88  of the spool valve  86  moves beyond the pair of blind bores  100  provided in the oil pump cover  16 . When this occurs, the spool valve  86  is in the open position, and a portion of the oil travels from the outlet side  73  of the pumping chamber  20 , through the redirect outlet passageway  98 , through the redirect inlet passageway  95 , through the inlet passageway  42 , and into the inlet side  43  of the pumping chamber  20 . This provides a sufficient amount of oil to the pumping chamber  20  so that the oil pump  10  does not begin to cavitate. 
     Once the oil pressure at the outlet  22  is reduced, such as by the slowing of the engine, the outlet pressure delivered to the spool valve  86  begins to drop. When this occurs, the compression spring  94  forces the spool valve  86  back toward the closed position, thereby closing the redirect inlet passageway to the inlet passageway  42 . This prohibits the flow of oil from the outlet  22  to the inlet  18 , as there is now a sufficient supply of oil to the pumping chamber  20 . 
     It should be noted that various engine configurations may require various oil pump  10  configurations of the present invention. For instance, the oil inlet  18  and strainer  34  may have to be a further distance laterally to communicate with the oil pan. In addition, height limitations may require a reduction in the number or a rerouting of the oil flow passageways. Lastly, various engine sizes may require various size oil pumps  10  of the present invention. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments, but to the contrary, it is intended to cover various modifications or equivalent arrangements included within the spirit and scope of the appended claims. The scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.