Abstract:
An internal combustion engine comprises an engine block having a crankshaft housed in a crankcase portion of the engine block and a coolant jacket adjacent to cylinder walls defining a coolant passage through the engine block to transfer heat from the cylinder walls to coolant flowing therethrough. An oil separator, formed integrally within said engine block and adjacent the coolant jacket, operates to separate oil from blowby gas accumulating in the crankcase portion and to transfer heat from the coolant passage to warm the blowby gas. The engine further includes a cylinder head mounted on an upper surface of the engine block, which may include a PCV passage to transfer blowby gas from the oil separator to the intake.

Description:
TECHNICAL FIELD 
     The present invention relates to a positive crankcase ventilation system for an internal combustion engine. 
     BACKGROUND OF THE INVENTION 
     During engine operation, combustion gas may leak between the cylinder and its piston rings into the engine crankcase. The leaked combustion gas is referred to as blowby gas and may comprise unburned intake air/fuel mixture, exhaust gas, oil mist, and water vapor. 
     A positive crankcase ventilation (PCV) system is typically employed to ventilate the crankcase and recirculate the blowby gas to the intake side of the engine for burning the gas in the combustion chamber. The PCV system takes advantage of the negative pressure in the intake to draw the gas out of the crankcase and may utilize a PCV valve to regulate the flow. 
     A PCV system may be incorporated as a foul air/oil separator in the cam cover of the engine. In the case where design package restraints make it unworkable to package an adequate separator within the cover, the separator may be attached externally to the cover or engine block. An external hose routes the blowby gas to the intake. 
     In cold environments, a common concern is freezing of the water vapor component of the blowby gas in an external PCV hose and valve. To minimize the risk of freezing, some PCV systems may include a PCV heater, or an extra hot water-carrying hose routed adjacent the PCV hose, or electrically heating or insulating the PCV hose, but these come at a significant cost. 
     The need exists for a PCV system which is protected from the risk of freezing without adding substantial cost or complexity to the engine. 
     SUMMARY OF THE INVENTION 
     The present invention incorporates a PCV system within the engine block and cylinder head castings to minimize the risk of freezing the PCV system. 
     A foul air/oil separator is cast integral with the engine block, with chambers to allow oil to separate and drain to the crankcase, while not allowing the foul air to bypass portions of the chambers through the oil drain holes. The chambers are positioned adjacent to water jacket passages used to carry engine-warmed coolant away from the engine to maintain the PCV chambers, and therefore the gas therein, above freezing. 
     As the blowby gas exits the final chamber of the air/oil separator, it may pass through an orifice in the cylinder head gasket to control the flow rate of the gas, without the need for a PCV valve. A passage within the cylinder head delivers the blowby gas to a short hose to the intake manifold, which transports the gas to the intake side of the engine. 
     This integral PCV system eliminates the expensive need for PCV-specific gas heaters or insulation of PCV hoses to minimize the risk of freezing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front sectional view of an engine embodying a PCV system of the present invention taken along section  1 — 1  of FIG. 2; 
     FIG. 2 is a plan view of a portion of the engine block and PCV system of FIG. 1; and 
     FIG.  3 . is an isometric view of the chambers of the PCV system. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a portion of an engine, generally  10 , comprised of an engine block  12  having a crankshaft  14  housed in a crankcase portion  16  of the block. Cylinders  18 , defined by cylinder walls  20 , are arranged in series along the longitudinal axis  22  of the engine block  12  as shown in FIG.  2 . Each cylinder  18  houses a piston  24  for reciprocation therein during operation. To cool the cylinders  18 , an adjacent coolant jacket  26  is provided in the engine block  12 . The coolant jacket  26  includes a coolant jacket wall  28 , which is generally parallel to the cylinder walls  20  and spaced radially therefrom to create a coolant passage  30 . The coolant passage  30  extends from a coolant inlet, not shown, at one end of the engine block  12 , along both sides of the cylinders  18 , to a coolant outlet, not shown, at the opposing end of the block. Coolant is pumped through coolant passage  30  to transfer heat out of the cylinder walls  20 , and is thereby engine-warmed. The engine-warmed coolant also warms the coolant jacket wall  28  of the coolant passage  30 . 
     A cylinder head  36  is mounted to the top of the engine block  12  with a head gasket  38  interposed therebetween. The cylinder head  36  closes each cylinder  18  and cooperates with each piston  24  in forming combustion chambers  40 . Each combustion chamber  40  has at least one intake port  42  through the cylinder head  36  to deliver an air/fuel intake mixture and at least one exhaust port  44  to carry exhaust gases away. An intake valve  46  is seated in the intake port  42  and an exhaust valve  48  is seated in the exhaust port  44  adjacent the combustion chamber  40 . An intake manifold  50  is mounted to the intake side  52  of the cylinder head  36  through a sealing flange  54 . The intake manifold includes an upstream throttle body, not shown, to meter intake charge into an intake plenum  58 , which distributes the charge to intake runners  60  aligned with intake ports  42  in the cylinder head  36 . 
     During engine operation, the intake stroke of the piston  24  draws intake air through the intake manifold  50  and intake port  42  to the combustion chamber  40 . During the power stroke, a small portion of the combustion gas blows by the piston  24 , and piston rings, and into the crankcase portion  16  of the engine block  12 . This combustion or blowby gas includes corrosive exhaust gas, unburned air/fuel intake mixture, oil mist, and water vapor. Therefore, the engine  10  requires a positive crankcase ventilation (PCV) system, shown generally as  66  in FIG. 3, to ventilate the crankcase  16  and recirculate the blowby gas to the intake side of the engine to be burned in the combustion chamber  40 . 
     The integral PCV system  66  of the present invention will now be discussed with additional reference to FIG.  3 . The PCV system  66  includes an air/oil separator  68  cast integral to the engine block  12  to separate oil from the blowby gas for recombustion. In the preferred embodiment, the separator  68  is labyrinthine in structure with three adjacent chambers, a first chamber  70 , a second chamber  72 , and a third chamber  74 , each stepped up in height from the previous chamber to allow gravity to drain separated oil back to the crankcase  16 . 
     The separator  68  is in flow communication with the crankcase  16  via a crankcase opening  76  at a lower end  78  of the first chamber  70  to draw blowby gas out of the crankcase and into the PCV system  66 . An upper transfer passage  80  bridges the first and second chambers  70 , 72  at an upper end  82  of the separator  68  to transfer blow by gas into the adjacent second chamber  72 . The upper transfer passage  80  may be cast integral to the cylinder head  36 . The floor  84  of the second chamber  72  is at a height intermediate the height of the first chamber  70 , making the second chamber stepped up from the first. 
     A lower end  86  of the second chamber  72  has an oil drainage conduit  88  connecting the second to the first chamber  70 , where the drainage conduit is sloped up so that the conduit is higher in the first chamber than in the second chamber. The drainage conduit  88  operates as a small “sink trap” where oil fills the conduit to block gas flow from bypassing part of the first and second chambers  70 , 72 , while allowing oil to trickle out of the second chamber. 
     A lower transfer passage  90  bridges the second and third chambers  72 , 74  from the lower end  86  of the second chamber  72  to a lower end  92  of the third chamber  74 . The floor  94  of the third chamber  74  is at a height intermediate the height of the second chamber  72  and therefore the third chamber is stepped up from the second chamber. The upper end  82  of the separator  68  has a gas outlet  96  through the third chamber  74  to transfer blowby gas to a cast-in PCV passage  98  in the mating cylinder head  36 . 
     The separator  68  operates to separate oil from the foul air of the blowby gas. As shown in FIG. 3 by the large open arrows, foul air flows in the crankcase opening  76  and through the labyrinthine-structured separator  68 , where oil adheres to the chamber walls. Oil then drains via gravity from the third chamber  74  into the second chamber  72  through the lower transfer passage  90 , from the second chamber  72  into the first chamber  70  through the drainage conduit  88 , and finally to the crankcase  16  through the crankcase opening  76  in the first chamber  70  as shown by the small arrows. The separator  68  is described as having three chambers but one or more chambers are also contemplated. 
     To effectively prevent the blowby gas from freezing, the separator chambers  70 , 72 , 74  are cast as part of the engine block  12  adjacent to the coolant jacket wall  28  as best shown in FIG.  1 . Coolant is pumped into the engine coolant passage  30  and by the cylinder walls  20  where combustion heat is transferred to the coolant. The coolant passages  30  are routed in close proximity to the separator  68 , such that heat from the engine-warmed coolant is transferred to the blowby gas therein. Since water vapor is a component of blowby gas, there is a risk that the blowby gas may condense and freeze if it is not warmed. 
     The cylinder head gasket  38  has a small aperture, not shown, aligned with the gas outlet  96  from the separator  68  in FIG.  3  and operates as a flow restrictor to control the flow of blowby gas to the intake. It supplants a commonly employed PCV valve. The cast-in PCV passage  98  in the cylinder head  36  extends from the aperture in the head gasket  38  to a side outlet  102  in the intake side  52  of the head. The PCV passage  98  may be routed adjacent to cylinder head water passages to further heat the blowby gas. The intake manifold flange  54  has a tube nipple  104 , molded from plastic, aligned with the side outlet  102  of the PCV passage  98  in the cylinder head  36 . A short PCV hose  106  attaches to the tube nipple  104  on the intake manifold flange  54  and to a second tube nipple to the intake plenum  58 . This PCV hose  106  may be composed of rubber or nylon. In place of a PCV hose, an intake manifold passage may be molded into the intake manifold which extends between the side outlet of the PCV head passage to the plenum. 
     During engine operation, blowby gas accumulates in the crankcase. Negative pressure in the intake plenum  58  (just downstream of the throttle valve) draws the blowby gas into the PCV system  66 , and more specifically, into the cast-in-the-block separator  68 . Oil is separated from the gas and drains back to the crankcase  16 . Engine-warmed coolant flowing through adjacent coolant passages  30  warms the blowby gas in the separator  68 . The gas passes through the aperture in the cylinder head gasket  38  and through the cast-in PCV passage  98  in the cylinder head  36 , where it is delivered to the PCV hose  106  connecting to the intake plenum  58  and becomes a component of the intake charge. 
     The PCV system of the present invention provides an inexpensive means for returning blowby gas to the intake system without the risk of freezing a PCV valve or the throttle valve. The separator of the present invention is not limited to the exact structure of three chambers, but rather to having the chambers cast integral in the block adjacent to the water passage. 
     The foregoing description of the preferred embodiment of the invention has been presented for the purpose of illustration and description. It is not intended to be exhaustive, nor is it intended to limit the invention to the precise form disclosed. It will be apparent to those skilled in the art that the disclosed embodiment may be modified in light of the above teachings. The embodiment was chosen to provide an illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, the foregoing description is to be considered exemplary, rather than limiting, and the true scope of the invention is that described in the following claims.