Abstract:
A lubrication system for an internal combustion engine having valves to optimize oil flow through an engine to increase engine efficiency. The lubrication system includes an engine driven oil pump connected to supply pressurized oil through a main oil feed to a main bearing gallery, a cam gallery, a cam phaser and switching valve lifters. A pair of pressure increasing valves connected to the main bearing gallery and the cam gallery selectively restrict oil flow to the cam gallery and the main bearing gallery to raise oil pressure supplied to the cam phaser. A pressure regulator valve is connected to the cam gallery to control oil pressure supplied to the switching lifters for cylinder deactivation or stepping valve train operation. The optimization of oil flow allows the engine to use a smaller oil pump and thereby increase engine efficiency while providing for actuation of the cam phaser or the switching lifters over the full engine speed range.

Description:
TECHNICAL FIELD 
     This invention relates to engine oil systems and, more particularly, to a system including pressure valves to optimize oil flow and pressure for various lubrication and actuation functions. 
     BACKGROUND OF THE INVENTION 
     Internal combustion engines may use lubricating oil for many purposes including, for example, lubricating moving parts, actuating cam phasers, and controlling valve lifters for valve stepping and cylinder deactivation. Cam phasers and cylinder deactivation devices generally require a higher oil pressure for actuation during engine operation than the moving parts of the engine require for proper lubrication. 
     One approach to maximize engine efficiency is to use a smaller oil pump to provide only the minimum amount of oil pressure needed to prevent engine wear. However, smaller oil pumps do not provide enough oil pressure to actuate a cam phaser or switching lifters at low and idle engine speeds. Thus, cam phasing, valve stepping, and cylinder deactivation can only be achieved at higher engine speeds. 
     Another approach is to use a larger oil pump to provide enough oil pressure to operate the cam phaser or switching lifters at low engine speeds. This approach allows phasing, valve stepping, and cylinder deactivation at lower engine speeds to alter the valve timing and increase engine efficiency. However, the efficiency gains are not without cost. A higher pressure produced by larger oil pump supplies excess flow that over lubricates the moving parts of the engine and requires additional energy to drive the pump, creating parasitic losses that reduce engine efficiency. 
     A method is desired of selectively regulating oil pressure throughout an engine to increase engine efficiency while allowing the engine to operate a cam phaser or switching lifters at low engine speeds without having to greatly increase oil pump output. 
     SUMMARY OF THE INVENTION 
     Co-pending applications pertaining to related subject matter were filed concurrently with this application on Sep. 18, 2003 as U.S. application Ser. No. 10/666,745, U.S. application Ser. No. 10/666,864, and U.S. application Ser. No. 10/667,233. 
     The present invention provides an oil system for an internal combustion engine having oil pressure control valves to optimize oil pressures in the engine while increasing engine efficiency by minimizing parasitic losses created from over lubrication. 
     In an exemplary embodiment, the oil system includes an oil pump having an inlet and an outlet. An oil pickup connected with the inlet extends into an engine oil sump to draw oil into the oil system. The outlet of the oil pump connects to a main oil feed which supplies oil to a main bearing gallery and a cam phaser. Oil sent to the cam phaser is used to actuate the cam phaser, while oil directed to the main bearing gallery is used primarily for lubrication purposes. In addition, some of the oil pumped into the main bearing gallery is sent through a cam gallery feed to a cam gallery in an upper part of the engine for lubrication of a valve train. When switching lifters are present, some of the oil directed to the cam phaser or the cam gallery may be diverted to the switching lifters to allow valve stepping or cylinder deactivation. 
     A first pressure increasing valve connected between the main oil feed and the main bearing gallery has a small opening designed to provide minimal oil flow to the main bearing gallery while oil pump output is low. As oil pump output increases, the pressure increasing valve reacts by providing additional openings to allow for addition flow through the valve. 
     The restriction of oil flow created by the first pressure increasing valve increases oil pressure to the main oil feed and the cam phaser while the main bearing gallery operates at a lower oil pressure. This allows cam phasing at engine idle or other conditions when oil pump pressure is normally to low to actuate the cam phaser. The additional oil pressure supplied to the cam phaser allows the phaser to vary valve timing at all engine speeds without a large increase in the size of the oil pump. The use of a smaller oil pump reduces parasitic losses for increased engine efficiency. 
     A second pressure increasing valve connected between the main bearing gallery and the cam gallery has a small opening designed to provide minimal oil flow to the cam gallery while oil pump output is low. As oil pump output increases, the pressure increasing valve reacts by providing additional openings to allow for additional flow through the valve. 
     The restriction of oil flow created by the second pressure increasing valve increases oil pressure to the main bearing gallery, while the cam gallery operates at a lower oil pressure. This allows the cam gallery to operate at a lower oil pressure than the main bearing gallery to reduce engine oil demands, thereby allowing the engine to operate with a smaller oil pump to reduce parasitic losses and increase engine efficiency. 
     A pressure regulator valve positioned between the second pressure increasing valve and the cam gallery regulates pressure to the cam gallery to control the switching lifters for valve stepping or cylinder deactivation. When low valve step operation is desired, the pressure regulator valve maintains low oil pressure to the switching lifters. When high valve step operation is desired the pressure regulator valve maintains high oil pressure to the switching lifters to cause high valve lift. When the switching lifters are used for cylinder deactivation, the pressure regulator valve may be used to provide adequate oil pressure for cylinder deactivation or normal oil pressure for standard engine operation. 
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a pictorial view of an internal combustion engine including an oil system with a cam phaser according to the invention; 
     FIG. 2 is a pictorial view of a portion of a direct acting valve train with switching lifters having portions broken away to show interior features of the components; 
     FIG. 3 is a pictorial view of an exemplary oil system for the engine of FIG. 1; 
     FIG. 4 is a pictorial view of a first pressure increasing valve for the oil system; 
     FIG. 5 is a pictorial view of a second pressure increasing valve for the oil system; and 
     FIG. 6 is a diagrammatic view of a pressure regulator valve for the oil system. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1 of the drawings in detail, numeral  10  generally indicates an internal combustion engine. The engine includes a cylinder block  12  having a bank of cylinders  14  containing pistons  16  connected with a crankshaft  18 . A cylinder head  20  carries intake and exhaust valves  21 ,  22  actuated by camshafts  24 ,  26 . A cam phaser  28  is mounted on the exhaust camshaft  26  to vary the exhaust valve timing. An oil pan  30  below the block forms an oil sump for the engine. 
     FIG. 2 illustrates an exhaust portion of an engine valve train  32  for use in an overhead cam piston type engine. The valve train  32  includes exhaust camshaft  26  which is driven through a drive sprocket  34  connected by a chain  36  (FIG. 1) with the engine crankshaft  18 . Cam phaser  28  is connected between the sprocket  34  and the camshaft  26  in order to vary the timing of the camshaft relative to the piston motion and other operating functions of the engine and relative to other camshafts of the engine. 
     The exhaust valves  22  are actuated through switching valve lifters  38  which are engaged by cams  40  of the camshaft  26 . The switching valve lifters  38  react to oil pressure to deactivate or selectively change the amount of valve lift provided for the associated exhaust valves  22 . More particularly, oil pressure supplied to the switching lifters  38  may be used to reduce valve lift or disable valve lift for cylinder deactivation. 
     FIG. 3 illustrates the passages of an oil system  44  within the engine  10 . The oil system includes an engine driven oil pump  46  having an inlet  48  and an outlet  50 . An oil pickup  52  connected with the pump  46  extends into the sump of the oil pan  30 . The pump  46  connects through an oil filter  54  with a main oil feed  56 . The main oil feed  56  distributes oil to a cam phaser feed  58  and a main bearing gallery  60 . The main bearing gallery  60  supplies oil to crankshaft main bearings and connecting rod bearings, not shown. The main bearing gallery  60  connects with a cam gallery feed  62  which carries oil to a cam gallery  64  for lubricating camshaft bearings and valve gear  66  within the cylinder head  20  of the engine  10 . 
     In accordance with the invention, a first pressure increasing valve  68 , as shown in FIG. 4, is connected between the main oil feed  56  and the main bearing gallery  60 . The first pressure increasing valve  68  has a tubular housing  70  surrounding a slidable flow control piston  72 . The piston  72  internally defines an orifice  74 . A biasing spring  76  between the piston  72  an outlet end  78  of the housing  70  urges the piston  72  toward an inlet end  80  of the housing, to close a large inlet opening  82  in the housing. A plurality of bypass openings  84  extend through a tubular wall of the housing  70  adjacent the inlet end  80 . 
     Under low oil pressure conditions, the biasing spring  76  holds the flow control piston  72  against the inlet end  80  of the housing  70 , closing the bypass openings  84  to only allow oil flow through the orifice  74  of the pressure increasing valve  68 . 
     As oil pressure increases at the inlet end  80  of the housing  70 , the piston  72  begins to slide toward the outlet end  78  and compress the biasing spring  76 . As the piston  72  moves toward the outlet end  78 , the piston allows incoming oil to flow through the bypass openings  84  to increase oil pressure to the cam gallery  64 . As oil pressure on the inlet end  80  of the housing  70  is reduced, the biasing spring  76  pushes the piston  72  back toward the inlet end  80  to close the bypass openings  84  and reduce oil pressure to the cam gallery  64 . 
     A second pressure increasing valve  86 , as shown in FIG. 5, is connected between the main bearing gallery  60  and the cam gallery  64 . The pressure increasing valve  86  has a tubular housing  88  surrounding a slidable flow control piston  90 . The piston  90  internally defines an orifice  92 . A biasing spring  94  between the piston  90  and an outlet end  96  of the housing  88  urges the piston  90  toward an inlet end  98  of the housing, to close a large inlet opening  100  in the housing. A plurality of bypass openings  102  extend through a tubular wall of the housing  88  adjacent the inlet end  98 . 
     Under low oil pressure conditions, the biasing spring  94  holds the flow control piston  90  against the inlet end  98  of the housing  88 , closing the bypass openings  102  to only allow oil flow through the orifice  92  of the pressure increasing valve  86 . 
     As oil pressure increases at the inlet end  98  of the housing  88 , the piston  90  begins to slide toward the outlet end  96  and compress the biasing spring  94 . As the piston  90  moves toward the outlet end  96 , the piston allows incoming oil to flow through the bypass openings  102  to increase oil pressure to the cam gallery  64 . As oil pressure on the inlet end  98  of the housing  88  is reduced, the biasing spring  94  pushes the piston  90  back toward the inlet end  98  to close the bypass openings  102  and reduce oil pressure to the cam gallery  64 . 
     A pressure regulator valve  104 , as shown in FIG.  6 ,is connected between the cam gallery  64  and the pressure increasing valve ξ. The pressure regulator valve  104  has a housing  106  surrounding a piston subassembly  108  comprising first and second slidable flow control pistons  110 ,  112 . Pistons  110 ,  112  are oppositely spaced and positioned adjacent an inlet  114  and an outlet  116 . A biasing spring  118  positioned above the piston subassembly  108  biases the pistons  110 ,  112  toward the lower end  120  of the housing  106  to space the pistons away from the inlet  114  to allow maximum flow through the valve  104 . Alternatively, a solenoid may be used in place of the spring  118  to control the placement of the pistons  110 ,  112  within the housing  106 . A pressure control inlet  122  diverts a portion of the incoming oil to a lower surface  124  of the piston  112  to increase the amount of oil pressure acting upon the lower surface. As a result, the pressure lifts the piston subassembly  108  against the spring  118  causing the second piston  112  to obstruct the inlet  114  to reduce flow through the valve  104 . 
     Referring now to FIGS. 3-6, the inlet  114  of the pressure regulator valve  104  receives oil from the cam gallery feed  62 . The position of the pistons  110 ,  112  relative to the inlet  114  regulates the amount of oil directed through the valve  114  and to the cam gallery  64  to control the amount of oil pressure supplied to the switching lifters  38  of the valve train  32 . Preferably, the pressure regulator valve  104  provides low oil pressure for low valve lift or normal valve train  32  operation and higher oil pressure as needed for high step valve train operation or cylinder deactivation. 
     As the incoming oil pressure to the pressure control inlet  122  increases, the piston subassembly  108  moves against the biasing spring  118  causing the second piston  112  to partially obstruct flow through the inlet  114  to maintain a predetermined maximum oil pressure to the cam gallery  64  and the switching lifters  38 . As the incoming oil pressure to the pressure control inlet  122  decreases, the biasing spring system  118  moves the piston subassembly  108  toward its original position, thereby opening the inlet  114  to reduce restriction through the valve  104 . 
     During engine operation, the oil pump  46  draws oil from the oil pan  30  through the oil pickup  52 . The oil is then pumped through the pump outlet  50  and oil filter  54  to the main oil feed  56 . The oil in the main oil feed  56  is then directed to the main bearing gallery  60  and the cam phaser  28 . Some of the oil in the main bearing gallery  60  flows to the cam gallery  64  through the pressure increasing valve  68 . 
     At lower engine speeds while oil pump output is minimal, only a small portion of the oil pumped though the oil system  44  flows through the orifice  74  of the pressure increasing valve  68 . The remainder of the oil not flowing through the orifice  74  builds oil pressure on the inlet end  80  of the pressure increasing valve  68  which creates back pressure in the main oil feed  56  and in turn increases oil pressure to the cam phaser  28 . This allows the cam phaser  28  to actuate during idle and low rpm conditions, when oil pump pressure would otherwise be too low for cam phaser actuation. This restriction of oil flow to the main bearing gallery  60  at lower engine speeds limits the system&#39;s oil flow requirements, thereby allowing the engine  10  to operate with a smaller more efficient oil pump. 
     A portion of the oil flowing into the main bearing gallery is pumped through the orifice  92  of the pressure increasing valve  86 . The remainder of the oil not flowing through the orifice  92  builds oil pressure on. the inlet end  98  of the pressure increasing valve  86  which increases oil pressure in the main bearing gallery. This restriction of oil flow to the cam gallery feed  62  limits the system&#39;s oil flow requirements, thereby allowing the engine  10  to operate with a smaller more efficient oil pump. 
     The pressure regulator valve  104  regulates oil flow from the cam gallery feed  62  to the cam gallery  64  and the switching lifters  38 . During low oil pressure operation, such as idle or low rpm operation, the size of the inlet  114  maintains an oil pressure to the cam gallery  64  which is optimal to cause the switching lifters  38  to operate with low valve lift. 
     As engine speed increases, the output from the oil pump  34  increases, causing the oil pressure in the system  32  to increase. As oil pressure increases at the inlet end  80 , the piston  72  slides toward the outlet end  78  against the biasing spring  76 . The movement of the piston  72  increases flow through the pressure increasing valve  68  by opening the bypass openings  84 . The increased flow of oil through the pressure increasing valve  68  increases oil pressure in the main bearing gallery  60 . 
     The increased oil pressure in the main bearing gallery  60  causes the piston  90  of the pressure increasing valve  86  slide toward the outlet end  96  against the biasing spring  94 . The movement of the piston  90  increases flow through the pressure increasing valve  86  by opening the bypass openings  102 . The increased flow of oil through the pressure increasing valve increases oil flow to the cam gallery feed  62 . 
     The increased oil flow to the cam gallery feed  62  causes pressure to increase on the lower surface  124  of the piston  112 , which causes the piston subassembly  108  to move upward in the housing  106  and compress the biasing spring  94 . As the piston subassembly  108  moves upward, the second piston  112  restricts flow through the inlet  114  to maintain high oil pressure to the switching lifters  38  for high valve lift operation. 
     Alternatively, if the engine is equipped with switching lifters  38  for cylinder deactivation, cylinder deactivation may be achieved by changing the oil flow rates through the pressure regulator valve as needed so that at lower engine speeds the switching lifters  38  receive adequate oil pressure for cylinder deactivation. 
     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.