Abstract:
An oil pump system can include a housing defining a pocket for an oil pump, a cavity, and a pump outlet passage connecting the pocket to the cavity. Low and high pressure relief passages can be defined by the housing for selectively fluidly coupling the cavity to a pressure relief area. A pressure relief valve positioned in the cavity can comprise first and second ends, first and second internal bores, and a slot in communication with the first internal bore. A biasing member positioned in the second internal bore can biasing the valve to a first position. The valve can translate to a second position aligning the slot with the low pressure relief passage to selectively provide low pressure relief to the oil pump, and can translate to a third position aligning the slot with the high pressure relief passage to selectively provide high pressure relief to the oil pump.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/351,457, filed on Jun. 4, 2010, the disclosure of which is hereby incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates generally to an oil pump system for an engine and, more particularly, to an oil pump with a pressure relief valve for an engine. 
     BACKGROUND 
     Motor vehicles typically include an internal combustion engine and an associated lubrication system for providing lubricating oil to various areas of the engine. The various areas can include bearings that support rotating shafts, such as a crankshaft and a camshaft, for example. The engine typically requires a certain flow rate of oil to be delivered to these various areas within a certain range of pressure, where the flow rate and pressure vary depending on the engine speed (i.e., crankshaft rotation speed). A conventional fixed displacement oil pump can be used to deliver lubricating oil to the various lubrication areas. However, such a conventional fixed displacement oil pump can produce less oil pressure than desired when operating at a high engine temperature and low engine speed condition. In addition, the fixed displacement oil pump can also produce excessively high oil pressure when operating at a high engine speed and low engine temperature condition. Increasing the displacement of such a fixed displacement pump to improve the oil pressure at the high temperature and low engine speed operating condition can result in more power consumption and thus a degradation in fuel economy while also increasing the oil pressure at the high engine speed and low temperature condition. 
     Thus, while fixed displacement oil pumps work for their intended purpose, there remains a need for continuous improvement in the relevant art. 
     SUMMARY 
     In one form, an oil pump system for an engine is provided in accordance with the teachings of the present disclosure. The oil pump system can include an oil pump housing, a low pressure and a high pressure relief passage, a pressure relief valve and a biasing member. The oil pump housing can define a pocket configured to receive an oil pump therein, a cavity, and an oil pump outlet passage connecting the pocket to a first end of the cavity. The low pressure relief passage can be defined by the pump housing for selectively fluidly coupling the cavity to a pressure relief area defined by the pump housing and adapted to be in fluid communication with an oil sump. The high pressure relief passage can be defined by the pump housing for selectively fluidly coupling the cavity to the pressure relief area. The pressure relief valve can be positioned in the cavity and can comprise a body having a first end, a second opposite end, a first internal bore extending from the valve first end, a second internal bore extending from the valve second end, and at least one slot positioned in the body in communication with the first internal bore. The biasing member can be positioned in the second internal bore and can bias the pressure relief valve to a first position. The pressure relief valve can be configured to overcome a biasing force of the biasing member and translate to a second position aligning the at least one slot with the low pressure relief passage to selectively provide low pressure relief to the oil pump in response to pressurized oil from the pump outlet passage flowing into the first internal bore being greater than a first predetermined pressure value. The pressure relief valve can be configured to further translate to a third position aligning the at least one slot with the high pressure relief passage to selectively provide high pressure relief to the oil pump in response to pressurized oil from the pump outlet passage being greater than a second predetermined pressure value. 
     In another form, an oil pump system for an engine is provided in accordance with the teachings of the present disclosure. The oil pump system can include a fixed displacement oil pump, an oil pump housing, a low pressure and a high pressure relief passage, an annular pressure relief valve and a biasing member. The oil pump housing can define a pocket configured to receive the fixed displacement oil pump therein, a cavity in fluid communication with the pocket, and an oil pump outlet passage connecting the pocket to a first end of the cavity. The low pressure relief passage can be defined by the pump housing for selectively fluidly coupling the cavity to a pressure relief area defined by the pump housing and adapted to be in fluid communication with an oil sump of the engine. The high pressure relief passage can be defined by the pump housing for selectively fluidly coupling the cavity to the pressure relief area, the high pressure relief passage being separate from the low pressure relief passage. The annular pressure relief valve can be positioned in the cavity and can comprise a body having a first end, a second opposite end, a first internal bore extending from the valve first end, a second internal bore extending from the valve second end, and at least one slot extending through the body and in communication with the first internal bore. The first internal bore can face the first end of the cavity and can be separated from the second internal bore by an internal wall member. The at least one slot can include an arcuate shaped sidewall extending in an axial direction toward the internal wall member. The biasing member can be positioned in the second internal bore and can bias the pressure relief valve to a first position where the pressure relief valve engages the first end of the cavity. The pressure relief valve can be configured to overcome a biasing force of the biasing member and translate to a second position aligning the at least one slot with the low pressure relief passage to selectively provide low pressure relief to the oil pump in response to pressurized oil from the pump outlet passage that flows into the first internal bore and into engagement with the internal wall member being greater than a first predetermined pressure value. The pressure relief valve can be configured to further translate to a third position aligning the at least one slot with the high pressure relief passage to selectively provide high pressure relief to the oil pump in response to pressurized oil from the pump outlet passage being greater than a second predetermined pressure value. The second predetermined pressure value can be greater than the first predetermined pressure value. 
     Further areas of applicability of the teachings of the present disclosure will become apparent from the detailed description, claims and the drawings provided hereinafter, wherein like reference numerals refer to like features throughout the several views of the drawings. It should be understood that the detailed description, including disclosed embodiments and drawings references therein, are merely exemplary in nature intended for purposes of illustration only and are not intended to limit the scope of the present disclosure, its application or uses. Thus, variations that do not depart from the gist of the present disclosure are intended to be within the scope of the present disclosure. 
    
    
     
       DRAWINGS 
         FIG. 1  is a perspective view of an exemplary pressure relief valve for an oil pump according to the principles of the present disclosure; 
         FIG. 2  is a perspective view of the exemplary pressure relief valve according to the principles of the present disclosure; 
         FIG. 3A  is a partial view of a first side of an exemplary oil pump housing of the oil pump according to the principles of the present disclosure; 
         FIG. 3B  is a sectional view of the exemplary oil pump housing of  FIG. 3A  along line  3 B and including the exemplary pressure relief valve according to the principles of the present disclosure; 
         FIG. 4  is a partial sectional view of a second side of the exemplary oil pump housing according to the principles of the present disclosure; 
         FIG. 5  is a partial sectional view of the second side of the exemplary oil pump housing and the exemplary pressure relief valve in a low pressure relief position according to the principles of the present disclosure; 
         FIG. 6  is a partial sectional view of the second side of the exemplary oil pump housing and the exemplary pressure relief valve in a position providing both high pressure and low pressure relief according to the principles of the present disclosure; 
         FIG. 7  is a diagram illustrating an exemplary pump output pressure vs. speed characteristic of the oil pump according to the principles of the present disclosure; and 
         FIGS. 7A-7E  are partial exemplary views of the pressure relief valve in various operational positions relative to the oil pump housing based on various engine operating conditions according to the principles of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     With initial reference to  FIGS. 1-6 , an exemplary oil pump system is provided having a pressure relief valve  10  for use in an oil pump housing  20  that is operably associated with an internal combustion engine. While the discussion will continue with reference to the internal combustion engine, it should be appreciated that the oil pump system can be used in other applications, including various types of engines and/or vehicles. 
     The pressure relief valve  10  includes a first body portion  30 , a second body portion  34  and a plurality of slots or openings  38  positioned in the first body portion  30 , as shown for example in  FIGS. 1 and 2 . Each of the plurality of openings  38  are in fluid communication with an internal bore  40  defined by the first body portion  30 . In one exemplary configuration, internal bore  40  includes an open end  42  and a closed or opposite end formed by an internal wall member  48 , as shown for example in  FIG. 1 . In this regard, it should be appreciated that the pressure relief valve  10  is a flow-through valve where lubricant (i.e., oil) can flow into and through internal bore  40  and selectively out openings  38 , as will be discussed in greater detail below. 
     Each of plurality of openings  38  can include an arcuate shape  44  formed in the first body portion  30  and extending axially away from the open end  42 . In one exemplary configuration, the plurality of openings  38  can be positioned adjacent wall member  48 , as shown for example in  FIG. 1 . The second body portion  34  defines an internal blind bore  46  configured to receive a biasing member or spring  50  ( FIG. 5 ) therein as will be described in greater detail below. Blind bore  46  includes an open end  54  and a closed end  58  formed by wall member  48 . While the pressure relief valve  10  is shown having a cylindrical configuration, it should be appreciated that pressure relief valve  10  can be provided with other shapes in cross-section, as may be required based on design and or packaging constraints. 
     The oil pump housing  20  can include a pump, such as an exemplary fixed displacement rotary oil pump  70 , positioned in a pocket  72  and configured to draw oil from a reservoir or sump of the internal combustion engine and output pressurized oil via a high pressure pump outlet  74 , as shown in  FIG. 3A . In one exemplary configuration, the oil pump housing  20  can include only the single high pressure pump outlet  74 . Using one high pressure pump outlet can reduce the manufacturing complexity associated with multiple high pressure pump outlets, as well as reduce a need for a check valve being operatively associated with the multiple high pressure pump outlets. 
     High pressure pump outlet  74  is fluidly coupled to an internal bore or cavity  78  configured to house the pressure relief valve  10  therein. In one exemplary configuration, the high pressure pump outlet  74  can be coupled to a first end  82  of the cavity  78 , as shown for example in  FIGS. 4-6 . The pressure relief valve  10  can be positioned in cavity  78  through a second end  86  and in an orientation such that first body portion  30  faces first end  82 . Spring  50  is inserted into blind bore  46  through open end  54  such that one end of spring  50  engages wall member  48  and the other end extends through open end  54  and engages a plug or cap  90 , as shown for example in  FIG. 5 . In one exemplary configuration, the plug  90  can be threadably received in pump housing  20  adjacent cavity  78  or in second end  86  of cavity  78 . 
     With particular reference to  FIG. 4 , cavity  78  further includes a high pressure relief port  100  and a low pressure relief port  104 . High pressure relief port  100  and low pressure relief port  104  are each fluidly coupled to an area  108  ( FIG. 3A ) of the pump housing  20  that is in fluid communication with the oil sump and thus an inlet to pump  70 . High pressure relief port  100  includes an annular groove or relief  112  formed in cavity  78  and in fluid communication with a passage  116  that is in fluid communication with area  108 . In a similar manner, low pressure relief port  104  includes an annular groove or relief  120  formed in cavity  78  and in fluid communication with a passage  124  that is likewise in fluid communication with area  108 . In one exemplary configuration, the oil pump housing  20  can include only one high pressure relief port  100  and only one low pressure relief port  104 . 
     While the annular relief  112  and passage  116  of pressure relief port  100  are both larger than the respective annular relief  120  and passage  124  of low pressure relief port  104 , it should be appreciated that the relative sizes of the annular reliefs  112 ,  120  and associated respective passages  116 ,  124  can be varied based on engine design parameters, pump specifications, or combinations thereof. In addition, it should also be appreciated annular reliefs  112 ,  120  can be provided in a configuration other than annular, such as a partially circumferentially extending relief. 
     Pressure relief valve  10  is configured to have an outer surface that is complementary to an inner surface of cavity  78  such that pressure relief valve  10  can axially translate within cavity  78  while minimizing an amount of oil that can pass between the mating surface of the pressure relief valve  10  and cavity  78 . Spring  50  provides a biasing force configured to urge pressure relief valve  10  to a rest or first position where first body portion  30  contacts a shoulder  130  adjacent high pressure pump outlet  74 , as shown for example in  FIG. 3B . In response to pressurized oil of a predetermined pressure being pumped into cavity  78 , pressure relief valve  10  is configured to translate axially along cavity  78  against the bias force of spring  50  to selectively place the openings  38  in fluid communication with the high pressure or low pressure relief ports  100 ,  104  to thereby provide the respective selective high or low pressure relief to oil pump  70 . 
     With additional reference to  FIGS. 7-7E , operation of the oil pump system will now be discussed in greater detail. Initially, it is noted that  FIGS. 7A-7E  illustrate various views representing various positions of pressure relief valve  10  based on corresponding operating conditions (e.g., conditions A-E shown in  FIG. 7 ) of an associated exemplary internal combustion engine. In this regard, it should be appreciated that the operating conditions of the internal combustion engine referenced in the graph of  FIG. 7  are for discussion purposes only and can be varied as may be desired based on, for example, different exemplary engine displacements and/or calibrations. 
     In operation, spring  50  can bias pressure relief valve  10  to the first position abutting shoulder  130  in an operating condition A where the exemplary engine is operating at relatively low engine RPM or speed such that there is not sufficient oil pressure generated to overcome the biasing force of spring  50 . This operating condition can be seen in  FIGS. 7 and 7A  where the openings  38  of pressure relief valve  10  are not in alignment with the high or low pressure relief ports  100 ,  104  such that pressure relief valve  10  does not provide pressure relief to pump  70  via ports  100 ,  104 . 
     As the engine speed increases in operating condition B shown in  FIG. 7 , greater oil pressure is developed by oil pump  70  such that the pressurized oil received in cavity  78  is sufficient to overcome the bias force of spring  50  and translate pressure relief valve  10  toward second end  86  of cavity  78 , as shown in  FIG. 7B . Spring  50  is calibrated such that a predetermined oil pressure is sufficient to translate pressure relief valve  10  so that openings  38  begin to align with low pressure relief port  104  at a predetermined intermediate engine speed. In this regard, pressurized oil from pump  70  flows into cavity  78  and then through internal bore  40  of first body portion  30  and into engagement with wall member  48 . The force of the pressurized oil acting against wall member  48  translates pressure relief valve  10  until the openings  38  begin to align with the low pressure relief port  104 . 
     At this position, oil begins to flow from cavity  78  to area  108  via openings  38  and low pressure relief port  104  thereby providing low pressure relief to pump  70  at intermediate engine speeds. Providing low pressure relief at the intermediate engine speeds can reduce the work of pump  70 , which can improve fuel economy. 
     The size of openings  38  in pressure relief valve  10  are configured to cooperate with the calibrated spring force to provide pressure relief over a specified pressure range of oil pump  70 . In addition, the arcuate shape of openings  38  also provide for a gradual or staged amount of low pressure relief within the specified pressure range. More particularly, the arcuate shape of openings  38  extend in an axial direction so as to provide for an increasing amount of opening  38  being in communication with low pressure relief port  104  as the oil pressure increases over the specified pressure range and can provide a gradual or smooth transition into the desired pressure relief condition. In this manner, the amount of low pressure relief increases as the oil pressure increases over the specified pressure range. 
     As the oil pressure continues to increase with the increasing engine speed shown in operating condition C of  FIG. 7 , the pressure relief valve  10  is urged beyond the low pressure relief port  104  such that openings  38  are no longer aligned with pressure relief port  104 , as shown in  FIG. 7C . In this operating condition C, pressure relief valve  10  again does not provide pressure relief to pump  70  via relief ports  100 ,  104 . As shown in  FIGS. 7A-7C , the pressure relief valve  10 , spring  50  and low pressure relief port  104  are configured to be cooperate to activate pressure relief over the specified pressure range such that the low pressure relief port  104  is inactive above and below the specified pressure range for certain engine speeds. 
     With reference to the operating condition D shown in  FIGS. 7 and 7D , pressurized oil in cavity  78  is of a sufficient pressure such that pressure relief valve  10  is urged further toward second end  86  and the openings  38  begin to align with high pressure relief port  100 . In this operating condition D, pressurized oil in cavity  78  is in fluid communication with area  108  via high pressure relief port  100  thereby providing high pressure relief to oil pump  70 . The low pressure relief port is blocked by first body portion  30  such that low pressure relief is not available via port  104  in this operating condition. 
     As the engine speed increased beyond the operating condition D associated with  FIG. 7D , the oil pressure increases in cavity  78  such that the pressure relief valve  10  is further translated until the second body portion  34  contacts second end  86  of cavity  78 . In this operating condition E, full pressure relief is provided to pump  70  by both the high and low pressure relief ports  100 ,  104 , as shown in  FIG. 7E  with reference to  FIG. 7 . In particular, openings  38  of pressure relief valve  10  are aligned with high pressure relief port  100  to provide high pressure relief to pump  70 . Further, pressure relief valve  10  is sized relative to the position of low pressure relief port  104  in pump housing  20  such that in this operating condition the first body portion  30  is positioned beyond low pressure relief port  104 . This provides for also placing low pressure relief port  104  in unobstructed fluid communication with cavity  78  to provide additional pressure relief to pump  70 . In one exemplary configuration, first body portion  30  can be positioned between the high and low pressure relief ports  100 ,  104 , as shown in  FIG. 7E . 
     By providing high pressure relief at the operating condition D of the engine illustrated in  FIG. 7D  before providing full pressure relief with the addition of low pressure relief port  104  ( FIG. 7E ), a gradual or smoother transition to full pressure relief is provided. Such a gradual transition can provide for a more efficient oil pump operation. 
     The oil pump system of the present disclosure thus provides a low-cost pressure relief system using a minimal number of components to reduce complexity while providing both low and high pressure relief at calibrated pressure ranges. The oil pump system of the present disclosure further provides the advantage of being a passive system that eliminates a need for any external controls. The oil pump system of the present disclosure can utilize a fixed displacement pump as opposed to a variable displacement pump, thus reducing cost and complexity of the oil pump system. In one exemplary aspect, the pressure relief valve and associated ports and relief passages in pump housing  20  can be used with the fixed displacement oil pump  70  in lieu of the variable displacement pump to provide the variable pressure associated with the variable displacement pump while also reducing cost and complexity. 
     It should be understood that the mixing and matching of features, elements and/or functions between various examples may be expressly contemplated herein so that one skilled in the art would appreciate from the present teachings that features, elements and/or functions of one example may be incorporated into another example as appropriate, unless described otherwise above.