Abstract:
Exhaust gas re-circulation is achieved internally in an internal combustion engine having intake and exhaust valves actuated by a camshaft. A controller monitors at least one engine parameter and automatically actuates an electrically actuated fluid operated brake actuator at a predetermined timing of movement of an engine piston to cause the actuator to maintain the exhaust valve at an intermediate position between a full open position and a closed position of the exhaust valve and cause exhaust gasses to be delivered from the exhaust manifold to the combustion chamber of the engine.

Description:
TECHNICAL FIELD  
         [0001]    This present invention relates to internal exhaust gas re-circulation and more particularly to a system for providing internal exhaust gas re-circulation with a compression release brake actuator.  
         BACKGROUND  
         [0002]    Exhaust gas re-circulation systems have been utilized to control emissions and reduce undesirable gasses and particulate matter to the atmosphere. Such engines have been used in an assortment of applications, such as, on highway, off highway and other internal combustion engine powered mobile equipment.  
           [0003]    Exhaust gas re-circulation systems (EGR) typically direct a portion of the exhaust gases emitted from an internal combustion engine to a combustion chamber of the engine by way of an EGR valve disposed in and elaborate external system of ducting and other components. The exhaust gas which is directed to the combustion chamber reduces the concentration of oxygen in the combustion chamber. This reduction in the concentration of oxygen lowers the maximum combustion temperature within the cylinder, slows the chemical reaction of the combustion process and decreases the formation of nitrous oxides (NOx).  
           [0004]    Exhaust gasses also contain unburned hydrocarbons. By reintroducing a portion of the exhaust gasses to the combustion chamber the unburned hydrocarbons are subsequently burned. This further reduces the emission of exhaust gas by-products which would otherwise be emitted as undesirable pollutants from the internal combustion engine.  
           [0005]    Internal combustion engines often include a turbocharger(s) to increase engine performance. Such devices utilize exhaust gases to drive a turbine disposed in the exhaust gas stream of the engine. The turbine is connected to and powers a compressor which boosts the pressure of air supplied to the inlet manifold of the engine. In turbocharged engines, the EGR valve directs a portion of the exhaust gases by way of the ducting from an exhaust manifold of the engine to an inlet of the compressor. This may result in the fouling of the turbocharger compressor and an intercooler of the engine, when such is provided.  
           [0006]    U.S. Pat. No. 6,012,424 to Zdenek Meistrick, dated Jan. 11, 2000 discloses an apparatus to accomplish exhaust gas re-circulation and/or engine braking. This patent discloses an elaborate and complicated system of actuators, control valves and fluid pressure sources defining separate EGR and compression release operating circuits which communicate with and control a slave piston to actuate at least one exhaust valve. Since the operating circuits are dependent on one another to trigger compression release braking and EGR system flexibility is limited. For example, a full range of EGR may not be supplied to the engine.  
           [0007]    This invention is directed at overcoming one or more of the problems set forth above.  
         SUMMARY OF THE INVENTION  
         [0008]    In one embodiment, a compression release brake actuating system for achieving compression release braking and internal exhaust gas re-circulation in an internal combustion engine having a cylinder, a bore in the cylinder and a piston slidably disposed in the bore and movable relative to the cylinder between a top dead center position and a bottom dead center position. A cylinder head is connected to the cylinder and an exhaust manifold is connected to the cylinder head. A combustion chamber is defined by the cylinder head, piston and cylinder. An exhaust valve is connected to the cylinder head and movable between a closed position and an open position. The exhaust valve has substantially zero lift relative to the cylinder head at the closed position and a predetermined maximum amount of lift relative to the cylinder head at the open position. The exhaust valve is adapted to pass exhaust gas between the combustion chamber and the exhaust manifold at the open position and is adapted to block the passing of exhaust gas between the exhaust manifold and the combustion chamber at the closed position. An intake valve is connected to the cylinder head and is movable between a closed position and an open position, said intake valve having substantially zero lift relative to the cylinder head at the closed position and a predetermined maximum amount of lift relative to the cylinder head at the open position. The intake valve is adapted to pass intake fluid flow between said intake manifold and the combustion chamber at the open position of the intake valve and adapted to block the passing of intake fluid flow between the combustion chamber and the intake manifold at the closed position of the intake valve. A camshaft is operatively connected to move the intake and exhaust valves between the closed and open positions. The camshaft determines the maximum amount of lift of each of the exhaust and intake valves at the open position. The exhaust valve is movable to the open position during movement of the piston within a first predetermined range of piston movement and the intake valve is movable to the open position during movement of the piston within a second predetermined range of piston movement. A compression release brake actuator is operatively connected to the exhaust valve and actuatable to maintain the exhaust valve at an intermediate lift position having a magnitude between the maximum amount of lift and the closed position during a predetermined portion of at least one of the first and second ranges of piston movement and providing a re-circulation of the exhaust gas between the exhaust manifold and the combustion chamber.  
           [0009]    In another embodiment, an internal combustion engine includes a cylinder having a bore and a piston slidably disposed in the cylinder bore and movable relative to the cylinder between a top dead center position and a bottom dead center position. A cylinder head is connected to the cylinder. An exhaust manifold is connected to the cylinder head. A combustion chamber is defined by the cylinder head, the piston and the cylinder. An exhaust valve is connected to the cylinder head and movable between a closed position and an open position. The exhaust valve has substantially zero lift relative to the cylinder head at the closed position and a predetermined maximum amount of lift relative to the cylinder head at the open position. The exhaust valve is adapted to pass exhaust gas between the combustion chamber and the exhaust manifold at the open position and adapted to block the passing of exhaust gas between the exhaust manifold at the closed position. An intake valve is connected to the cylinder head and movable between a closed position and an open position. The intake valve has substantially zero lift relative to the cylinder head at the closed position and has a predetermined maximum amount of lift relative to said cylinder head at the open position. The intake valve is adapted to pass intake fluid flow between the intake manifold and the combustion chamber at the open position of the intake valve and being adapted to block the passing of intake fluid flow between the combustion chamber and the intake manifold at the closed position of the intake valve. A camshaft is operatively connected to move the intake and exhaust valves between the closed and open positions. The camshaft determines the maximum amount of lift of each of the exhaust and intake valves at the open position. The exhaust valve is movable to the open position during movement of the piston within a first predetermined range of piston movement and the intake valve is movable to the open position during movement of the piston within a second predetermined range of piston movement. A compression release brake actuator is operatively connected to said exhaust valve and being actuatable during said first predetermined range of piston movement to modify the movement of the exhaust valve between said open and closed positions and maintain the exhaust valve at said intermediate position during at least a portion of the first range of piston movement and during a portion of a second range of piston movement and provide a re-circulation of the exhaust gas between the exhaust manifold and the combustion chamber.  
           [0010]    In yet another embodiment, a method of controlling internal exhaust gas re-circulation in an internal combustion engine having a compression release brake actuator, an exhaust valve, an intake valve, an exhaust manifold, a cam shaft operatively connected to move said exhaust valve between an open position at which the exhaust valve is at a maximum lift position and a closed position, a combustion chamber defined by a piston, a cylinder and a cylinder head, The piston being movable between a top dead center position and a bottom dead center position, including the steps of: moving the exhaust valve mechanically with the camshaft from the closed position to the open position in response to the piston being at a first predetermined range of piston movement; moving the intake valve mechanically by the camshaft from the closed position to the open position in response to the piston being at a second predetermined range of piston movement different than said first predetermined range of piston movement; actuating the compression release brake actuator in response to the piston being at a predetermined position within at least one of the predetermined first and second predetermined ranges of piston movement; maintaining the exhaust valve at the intermediate lift position subsequent to actuation of the compression release brake actuator and during a predetermined range of piston movement; and passing exhaust gas between the exhaust manifold and the combustion chamber while the exhaust valve is at the intermediate position. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a diagrammatic longitudinal cross-section view of an embodiment of an internal combustion engine showing an engine brake and internal exhausts gas re-circulation system,  
         [0012]    [0012]FIG. 2 is a diagrammatic cross-section view taken along line  2 - 2  of FIG. 1,  
         [0013]    [0013]FIG. 3 is a graphical illustration of the timing and lift profiles of intake and exhaust valves of a 4 stroke internal combustion engine cycle with internal exhaust gas re-circulation;  
         [0014]    [0014]FIG. 4 is another graphical illustration of the timing and lift profiles of intake and exhaust valves of a 4 stroke internal combustion engine cycle with internal exhaust gas re-circulation; and  
         [0015]    [0015]FIG. 5 is another graphical illustration of the timing and lift profiles of intake and exhaust valves of a 4 stroke internal combustion engine cycle with internal exhaust gas re-circulation. 
     
    
     DETAILED DESCRIPTION  
       [0016]    With reference to the drawings and particularly FIGS. 1 and 2, an internal combustion engine  10  is shown having with a compression release brake actuating system  12  for achieving compression release braking and internal exhaust gas re-circulation. The internal combustion engine  10  has an engine block  14 , a cylinder head  16  connected to the engine block  14  by a plurality of fasteners (not shown), and a crankshaft  18  rotatively connected to the engine block  14 . A plurality of cylinders  20 , each having a bore  22 , are disposed in the engine block  14  and connected to the cylinder head  16  by way of the aforementioned cylinder block connection. A plurality of pistons  24  are slidably disposed in the bore  22  of the cylinders  20 , one in each cylinder  20 , and connected to the crankshaft  18  by a connecting rod  26 . The cylinder head  16  and each cylinder bore  22  and associated piston  24  define a combustion chamber  28  therebetween. The pistons  24  are movable in the cylinder bores  22  between a top dead center position (TDC) adjacent the cylinder head  16  and a bottom dead center position (BDC) spaced from the top dead center position as determined by the crankshaft  18 . As shown in FIG. 1, the internal combustion engine is a 6 cylinder four cycle in line engine having combustion, exhaust, intake and compression strokes of the pistons  24 . It is to be noted that internal combustion engines with a greater number of cylinders or a fewer number of cylinders are considered equivalents. It is also noted that the engine may operate in a two cycle mode.  
         [0017]    Each cylinder  20  has a pair of intake valves  30  and a pair of exhaust valves  32 . The intake and exhaust valves are  30 ,  32  are slidably connected to the cylinder head and moveable between a closed position at which the valves  30 ,  32  are in seated engagement and have substantially zero lift with respect to the cylinder head  16  and an open position at which the valves  30 , 32  are spaced a predetermined maximum desired lift distance from the seated position in the cylinder head  16 . Each pair of intake and exhaust valves  30 , 32  are positioned in an associated combustion chamber  28 . The intake and exhaust valves  30 , 32  are biased to the closed position by a coil spring  34  and mechanically opened into the combustion chamber  28  during normal engine operation by mechanical system  48  having a camshaft  36  rotatively connected to the engine block  14 . The camshaft  36  is operatively connected to forcibly move the intake and exhaust valves  30 , 32  between the closed and open positions. The camshaft  36  determines the maximum amount of lift of each of the exhaust and intake valves  30 , 32  at the open position.  
         [0018]    As best seen in FIGS.  3 - 5 , and with respect to each cylinder  20  of the internal combustion engine  10 , the exhaust valves  32  are timed to normally be movable by the camshaft  36  to the open position during movement of the respective piston  24  within a first predetermined range of piston movement and the intake valves  30  are timed to normally be movable by the camshaft  36  to the open position during movement of the piston  24  within a second predetermined range of piston movement. As shown in FIGS.  3 - 5 , the camshaft  36  begins opening the exhaust valve  32  on the combustion stroke of the respective piston  24  at about 90 degrees of rotation of the crankshaft  18  and normally closes the exhaust valve  32  on the exhaust stroke of the piston  24  at about 360 degrees of crankshaft rotation. The camshaft  36  begins opening the intake valve  30  on the at about 360 degrees of crankshaft  18  rotation and on the exhaust stroke of the piston  24  and closes the intake valve  30  on the compression stroke of the piston  24  at about 540 degrees of rotation of the crankshaft  18 . It should be noted that the specific crankshaft angles recited are approximate and may vary for between engine platforms.  
         [0019]    In the embodiment shown in FIG. 2, each lobe  38  of the camshaft  36  engages and reciprocally moves a cam follower  40 . A push rod  42  transfers motion of the cam follower to a rocker arm  44  pivotally connected to the cylinder head  16 . One end  46  of the rocker arm  44  bears against the push rod  42  and an opposite end  50  of the rocker arm bears against a valve bridge  52 . The valve bridge  52  is engageable with the pair of exhaust valves  32  and a similar valve bridge (not shown) is engageable with the pair of intake valves  30 . It should be noted that, the camshaft  36  of the mechanical system  48  may directly mechanically actuate the intake and exhaust valves  30 , 32 , directly engage the valve bridge  52 , or directly engage the rocker arm  44 . It should that single or multiple intake and exhaust valves  30 , 32  may be provided for each combustion chamber  28 .  
         [0020]    The fixed geometry of the mechanical system  48  establishes the amount of lift of the intake and exhaust valves  30 ,  32  between the closed and open positions. In the particular embodiment of the internal combustion  10  shown, the normal amount of travel to place the exhaust valves at the open position is about 20 millimeters (0.78 inches). This provides desirable engine exhaust flow characteristics and proper engine operation of the particular. It should be recognized that the amount of lift is a function of engine geometry and may vary by engine model.  
         [0021]    An exhaust manifold  54  is connected to said cylinder head and in fluid flow communication with the combustion chambers  28 . The exhaust valves  32  are adapted to pass exhaust gas between each combustion chamber  28  and the exhaust manifold at the open position of the exhaust valve and adapted to block the passing of exhaust gas between said exhaust manifold  54  and the combustion chamber at the closed position of the exhaust valve.  
         [0022]    An intake manifold  56  is connected to the cylinder head  16  and in fluid flow communication with each combustion chamber  28 . The intake valve  30  passes intake fluid flow such as air and air/fuel mixture or other air mixture between the intake manifold  56  and the combustion chamber  28  at the open position and blocks the passing of intake fluid flow between the combustion chamber  28  and the intake manifold  56  at the closed position.  
         [0023]    A turbocharger (not shown) of conventional design may be provided to boost the inlet air mixture pressure of the engine  10 . The compressor of the turbocharger is connected to the intake manifold  56  and the turbine of the compressor is connected to the exhaust manifold  54 .  
         [0024]    The compression release brake actuating system  12  has at least one compression release brake actuator  60  which is connected to the cylinder head  16  of the internal combustion engine  10  and operatively connected to the exhaust valve  32  and actuatable to position the exhaust valve  32  at an intermediate lift position located between open position at which the maximum desired amount of lift is provided and the closed position during a predetermined portion of at least one of a first and second ranges of piston  24  movement and providing a re-circulation of the exhaust gas between said exhaust manifold  54  and the combustion chamber  28 . It is to be noted that a compression release brake actuator  60  may be provided for one or more of the cylinders  20 .  
         [0025]    The compression release brake actuating system  12  has a sensor  62  adapted to sense an engine parameter and deliver a position signal related to a position of said piston  24 . A controller  64  is connected to the compression release brake actuator  60  and to the sensor  62 . The controller  64  may be a microprocessor based or discrete hard wired components. The controller  64  is adapted to receive the position signal and deliver a responsive actuation control signal. The compression release brake actuator  60  receives the actuation control signal and in one mode of operation moves the associated exhaust valve  32  to the intermediate lift position in response to receiving the actuation control signal. In another mode of operation, the compression release brake actuator  60  receives the actuation control signal and stops movement of the related exhaust valve  32  at the intermediate position in response to receiving the actuation control signal.  
         [0026]    The sensor  62  may be adapted to sense the angular position of the crankshaft  18  as the crankshaft  18  rotates about its longitudinal axis  74  in the engine block  14 . Since the crankshaft  18  is pivotally connected to the pistons  24 , the angular position of the crankshaft  18  provides piston  24  position information. It should be noted that sensors  62  may include one or more sensors  62  and the sensor  62  may sense other engine parameters, for example, engine speed, cylinder pressure, and piston position to mention just a few.  
         [0027]    The compression release brake actuator  60  has a body  66  connected to the cylinder head  16 , a plunger  68  slidably movably connected to the body and movable between retracted and extended positions, and a source of pressurized fluid  70  connected to the plunger and adapted to move the plunger  68  relative to the body  66  to the extended position and stop movement of the exhaust valve  32  or position the exhaust valve  32  at the intermediate position. The plunger  68  may be engageable with the rocker arm  44  to maintain the exhaust valve  32  at the intermediate position.  
         [0028]    The compression release brake actuator  60  has an electrically actuated control valve  72  having, for example, a solenoid, piezo or other known electrical actuator, controls the flow of pressurized fluid flow from the source of pressurized fluid  70  to the actuator  60 . The electrically actuated control valve  72  is connected to the controller  64  and connected in fluid communication between the source of pressurized fluid flow  70  and the compression release brake actuator  60 . The control valve  72  is actuatable to controllably deliver pressurized fluid flow to the actuator  60  in response to receiving the actuating control signal.  
         [0029]    The source of pressurized fluid  70  may be a variable delivery pump  76  connected to a common rail  78  of a fuel system of the internal combustion engine  10 . The variable delivery pump preferably delivers high pressure hydraulic actuating fluid, in the vicinity of 3000 psi, to the common rail. The high pressure hydraulic fluid provides the energy to actuate the fuel injectors (not shown). The common rail  78  is connected to the electrically actuated control valve  72  and provides pressurized fluid flow to also actuate the compression release brake actuators  60 . It should be noted that other known sources of high pressure fluid are considered suitable substitutes.  
         [0030]    As seen in FIG. 4, the compression release brake actuator  60  may be actuated during the first predetermined range of piston movement. This actuation modifies the movement of the exhaust valve  32  from the open to the closed position and maintains the exhaust valve  32  at the intermediate position during at least a portion of the second range of piston  24  movement to provide a late closing of the exhaust valve  32  and internal exhaust gas re-circulation. As seen in FIG. 4 the exhaust valve  32  closes at about 430 degrees of crankshaft  18  rotation.  
         [0031]    As seen in FIG. 3, the second range of piston  24  movement occurs during an intake stroke of the piston  24 . The compression release brake actuator  60  is actuated during movement of the piston  24  within the second range of piston  24  movement (intake stroke) and maintains the exhaust valve  32  at the intermediate position during a predetermined portion of the second range of piston  24  movement. Exhaust gas is re-circulated between the exhaust manifold  54  and the combustion chamber  28  during this predetermined portion of the second range of movement. As shown in FIG. 3, the exhaust valve  32  is moved to the intermediate position between of 420 degrees and about 560 degrees of camshaft rotation.  
         [0032]    As seen in FIG. 5, each piston  24  is movable relative to the cylinder toward said top dead center position during a compression stroke of the piston  24 . The compression release brake actuator  60  is actuatable during the compression stroke of the piston  24  and maintains the associated exhaust valves  32  at the intermediate position during a predetermined third range of movement of the piston  24  at which the pressure in the exhaust manifold  56  is greater in magnitude than the pressure in the associated combustion chamber  28  and exhaust gas is re-circulated from the exhaust manifold  56  to the combustion chamber  28 .  
       INDUSTRIAL APPLICABILITY  
       [0033]    With reference to the drawings and in operation the compression release brake actuating system  12 , which is normally provided to move the exhaust valve  32  to the intermediate position when the piston  24  is near the top dead center position on the compression stroke of the piston  24  and blow down the related cylinder  20  to achieve compression release engine braking, also facilitates internal exhaust gas re-circulation between the exhaust manifold  54  and the combustion chamber  28  in a simple and economical manner by maintaining the exhaust valve  32  at the intermediate position at a proper timing relative to piston  24  position thereby eliminating the need for expensive external exhaust gas re-circulation systems or other complicated systems.  
         [0034]    The compression release brake actuator  60  is actuatable in response to a signal delivered from the controller  64  which is related to an engine parameter signal delivered to the controller  64  based on the position of the piston  24 . This facilitates accurate exhaust valve  32  response and precise exhaust valve positioning. Thus, the exhaust valve  32  is moved to the open and closed positions by way of the compression release brake actuator  60  in accordance with the timing set forth in FIGS.  3 - 5  and without requiring a substantial amount of additional hardware. The compression release brake actuating system  12  utilizes pressurized fluid flow from the high pressure source  70 , which may have preexisted to provide pressurized hydraulic fluid flow for actuation of the fuel injectors (not shown), to force the plunger  68  of the actuator  60  to either maintain the exhaust valve  24  at the intermediate position or to forcibly urge the exhaust valve  24  to the intermediate position.  
         [0035]    The actuator  60  receives an electrical signal from the controller  64  and the electrically actuated control valve  72  responds to this signal and delivers high pressure fluid from the high pressure source  70  to the plunger  68 . The high pressure plunger  68  slidably extends from the body  66  which results in the exhaust valve  32  being maintained at the intermediate position. In the absence of a electrical control signal being delivered to the compression release brake actuator  60  the high pressure at the control valve  72  is blocked from the plunger  68  and the actuator is disabled.  
         [0036]    The method of controlling internal exhaust gas re-circulation in an internal combustion engine  10  with the compression release brake actuator  60 , comprises the steps of moving the exhaust valve  32  mechanically by the camshaft from the closed position to the open position in response to the piston being at a first predetermined range of piston  24  movement; moving the intake valve  30  mechanically by the camshaft  36  from the closed position to the open position in response to the piston  24  being at a second predetermined range of piston movement different than said first predetermined range of piston movement; and actuating the compression release brake actuator  60  in response to the piston  24  being at a predetermined position within at least one of said predetermined first and second ranges of piston  24  movement; maintaining the exhaust valve  32  at the intermediate lift position subsequent to actuation of the compression release brake actuator  60  and during a predetermined range of piston  24  movement; and passing exhaust gas between the exhaust manifold  54  and the combustion chamber  28  while the exhaust valve  32  is at the intermediate position.  
         [0037]    The method further may include the steps of: maintaining the exhaust valve  32  at the intermediate position during a predetermined range of piston  24  movement occurring during the second predetermined range of piston  24  movement and during movement of the intake valve  30  between the open and closed positions.  
         [0038]    The method may further include the steps of: stopping movement of the exhaust valve  32  at the intermediate position and from closing and maintaining the exhaust valve  32  at the intermediate position during a predetermined range of piston  24  movement during which the intake valve  30  is being moved between the closed and open positions.  
         [0039]    The method further may include the steps of: moving the exhaust valve  32  to the intermediate position during the compression stroke of the piston  24 , and maintaining the exhaust valve  32  at the intermediate position during a predetermined range of movement of the piston  24  during the compression stroke.  
         [0040]    The method further may include the step of delivering a piston position signal to the compression release brake actuator  60  and moving the plunger  68  to a second position at which said exhaust valve  32  is maintained at the intermediate position.  
         [0041]    Other aspects may be obtained from a study of the drawings, the disclosure and the appended claims.