Abstract:
The present invention relates to engines having multiple hydraulic devices. For instance a multi-cylinder diesel engine might include both an a fuel injector and an engine compression release brake. Traditionally, each of these hydraulic devices has been controlled by an individual actuator control valve. However, engineers have learned that decreasing the number of engine components can increase engine robustness. In addition, engineers have learned that de-coupling fluid pressure to the needle valve member hydraulic surface from fluid pressure lines to other injector components can result in greater control of the injector. Therefore, the present invention utilizes a single actuator control valve to control both hydraulic devices for an engine cylinder and to provide independent control of fluid pressure to the needle valve member closing hydraulic surface.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates generally to engines, and more particularly to actuators for controlling hydraulically actuated fuel injectors and engine compression release brake valves.  
         BACKGROUND  
         [0002]    In several multi-cylinder diesel engines today, a number of hydraulically actuated devices are coupled to each engine cylinder. For example, it is becoming common place for each cylinder to include a hydraulically actuated fuel injector and an engine compression release brake. In most instances, each of these hydraulic devices is controlled by its own individual fluid control valve. For instance, hydraulically actuated fuel injectors such as that shown in U.S. Pat. No. 5,738,075 issued to Chen et al. on Apr. 14, 1998, include a solenoid driven fluid control valve that is attached to the injector body. Fluid pressure to both an intensifier piston hydraulic surface and a direct control needle valve hydraulic surface is controlled by this control valve. While fuel injectors, and other hydraulic devices, including individual fluid control valves have performed adequately, there remains room for improvement. For instance, it is known in the art that a reduction in the number of engine components can make the engine more robust. Further, engineers have found that by de-coupling the fluid pressure line to the direct control needle valve from the fluid pressure line to other injector components, can result in greater control over injection events.  
           [0003]    The present invention is directed to overcoming one or more of the problems as set forth above.  
         SUMMARY OF THE INVENTION  
         [0004]    In one aspect of the present invention, a hydraulic system includes a source of high pressure fluid and a low pressure reservoir. An actuator control valve having a valve body is also provided. The valve body defines a high pressure passage that is fluidly connected to the source of high pressure fluid, a low pressure passage that is fluidly connected to the low pressure reservoir, and a device control passage. The actuator control valve is movable between a first position in which the device control passage is open to the low pressure passage, and a second position in which the device control passage is open to the high pressure passage. The device control passage is fluidly connected to at least one of a first hydraulic device and a second hydraulic device.  
           [0005]    In another aspect of the present invention, an engine includes an engine housing that defines a plurality of cylinders. An actuator control valve is provided for each of the cylinders and is attached to the engine housing. The actuator control valve has a valve body that defines a device control passage, a high pressure passage and a low pressure passage. An electronic control module is provided that is in control communication with the actuator control valve. A first hydraulic device and a second hydraulic device are provided for each of the plurality of cylinders. A source of high pressure fluid is fluidly connected to the high pressure passage. A low pressure reservoir is fluidly connected to the low pressure passage. The actuator control valve is movable between a first position in which the device control passage is open to the low pressure passage and a second position in which the device control passage is open to the high pressure passage.  
           [0006]    In still another aspect, a method of operating a fuel injector and an engine compression release brake includes a step of connecting the engine compression release brake and fuel injector to an actuator control valve. The engine compression release brake is actuated at least in part by activating the actuator control valve and disabling the fuel injector. The fuel injector is actuated at least in part by activating the actuator control valve. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a schematic representation of an engine according to the present invention;  
         [0008]    [0008]FIG. 2 is a sectioned side diagrammatic representation of an actuator according to the present invention;  
         [0009]    [0009]FIG. 3 is a sectioned side diagrammatic representation of a fuel injector according to the present invention; and  
         [0010]    [0010]FIG. 4 is a sectioned side diagrammatic representation of an engine compression release brake according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0011]    Referring to FIG. 1 there is shown an engine  10  according to the present invention. A low pressure reservoir  12  is provided in engine  10  and preferably includes an amount of low pressure engine lubricating oil. While low pressure reservoir  12  is preferably an oil pan that has an amount of engine lubricating oil, it should be appreciated that other fluid sources having an amount of available fluid, such as coolant, transmission fluid or fuel, could instead be used. A high pressure pump  13  pumps oil from low pressure reservoir  12  and delivers the same to high pressure manifold  14 . High pressure oil flowing out of high pressure manifold  14  is delivered via high pressure fluid supply line  15  to a hydraulic system provided in engine  10 , and oil is returned to low pressure reservoir  12  via low pressure return line  16  after it has performed work in the hydraulic system. Engine  10  also has an engine housing  11  that defines a plurality of cylinders  19 .  
         [0012]    Each of the cylinders  19  defined by engine housing  11  has a movable piston  20 . Each piston  20  is movable between a retracted, downward position and an advanced, upward position. For a typical four cycle diesel engine  10 , the advancing and retracting strokes of piston  20  correspond to the four stages of engine  10  operation. When piston  20  retracts from its top dead center position to its bottom dead center position for the first time, it is undergoing its intake stroke and air can be drawn into cylinder  19  via an intake valve. When piston  20  advances from its bottom dead center position to its top dead center position for the first time it is undergoing its compression stroke and air within cylinder  19  is compressed. At around the end of the compression stroke, fuel can be injected into cylinder  19  by fuel injector  60 , and combustion within cylinder  19  can occur instantly, due to the high temperature of the compressed air. This combustion drives piston  20  downward toward its bottom dead center position, for the power stroke of piston  20 . Finally, when piston  20  once again advances from its bottom dead center position to its top dead center position, post combustion products remaining in cylinder  19  can be vented via an exhaust valve corresponding to the exhaust stroke of piston  20 , or partially vented via an engine compression release brake valve  90  during engine braking. While engine  10  has been illustrated as a four cycle, four-cylinder engine, it should be appreciated that any desired number of cylinders could be defined by engine housing  11 .  
         [0013]    Each cylinder  19  is operably connected to a number of hydraulically actuated devices. As illustrated in FIG. 1, these hydraulic devices are preferably a hydraulically actuated fuel injector  60  and an engine compression release brake  90 . Fuel injector  60  is fluidly connected to a fuel tank  21  and delivers fuel to cylinder  19  for combustion while engine brake  90  controls release of compressed air from cylinder  19  when combustion is not desirable. A brake/injector actuator control valve  24  is fluidly connected to the fuel injector  60  and engine brake  90  of each cylinder  19 . Brake/injector actuator control valve  24  preferably acts as a flow control valve, but could be modified to function as a pressure switch for fuel injector  60  and engine brake  90 . Brake/injector actuator control valve  24  is controlled in operation by an electronic control module  17  via communication line  18 .  
         [0014]    A two-way valve  23  is preferably positioned between the brake/injector actuator control valve  24  and the engine brake  90  of each cylinder  19 . Each of the two-way valves  23  can include its own individual electronic actuator, an individual mechanical actuator, or a single actuator that simultaneously opens and closes all of the two-way valves  23  based upon an electronic control signal and/or an operator control action. Those skilled in the art should appreciate that valve  23  could be eliminated and brake/injector actuator control valve  24  could be modified from that which is illustrated herein to perform the function of valve  23 . Additionally, it should be appreciated that valve  23  could instead be a three-way valve. A more detailed description of this modified brake/injector actuator control valve  24  will follow the description of the actuator control valve  24  illustrated herein.  
         [0015]    Referring to FIG. 2, there is shown a sectioned side view of the brake/injector actuator control valve  24  of FIG. 1 according to the present invention. Brake/injector actuator control valve  24  has an valve body  25  that is attached to an electrical actuator  26 . Electrical actuator  26  is preferably a solenoid that includes a coil  28  and an armature  29 . Alternatively, electrical actuator  26  could be another device, such as a piezoelectric actuator. A fastener  30  attaches armature  29  to a pilot valve member  31 , which is positioned in valve body  25  and trapped between a high pressure seat  32  and a low pressure seat  33 . Valve body  25  defines a high pressure passage  44  that is fluidly connected to high pressure manifold  14  and a low pressure passage  37  that is fluidly connected to low pressure reservoir  12 . When electrical actuator  26  is de-energized, such as when brake/injector actuator control valve  24  is in a first position, a biasing spring  27  biases pilot valve member  31  toward its downward position, closing low pressure seat  33 . When pilot valve member  31  is in this position, a variable pressure passage  35  defined by valve body  25  is fluidly connected to high pressure passage  44 . When electrical actuator  26  is energized, such as when brake/injector actuator control valve  24  is in a second position, armature  29  and pilot valve member  31  move upward toward its first position closing high pressure seat  32  and opening low pressure seat  33 . When pilot valve member  31  is in this position, variable pressure passage  35  is fluidly connected to low pressure passage  37 .  
         [0016]    Returning to brake/injector actuator control valve  24 , a spool valve member  40  is also positioned in valve body  25  and is movable between an upward, retracted position as shown, and a downward, advanced position. Spool valve member  40  is biased toward its retracted position by a biasing spring  49 . Spool valve member  40  defines a high pressure annulus  42  that is always open to high pressure passage  44  and is positioned such that it can open a device control passage  52  to high pressure passage  44  when spool valve member  45  is in its advanced position. A low pressure annulus  45  is also provided on spool valve member  40  that can connect device control passage  52  to a low pressure passage  47  defined by valve body  25  when spool valve member  40  is in its retracted position as shown. Spool valve member  40  has a control hydraulic surface  54  that is exposed to fluid pressure in a spool cavity  53 , and a high pressure surface  41  that is continuously exposed to high pressure in high pressure passage  44  via a number of radial passages  43  defined by spool valve member  40 . Surfaces  41  and  54  preferably are about equal in surface area, but could be different. Spool cavity  53  is fluidly connected to variable pressure passage  35 .  
         [0017]    When variable pressure passage  35  is fluidly connected to high pressure manifold  14 , such as when pilot valve member  31  is in its second position, pressure within spool cavity  53  is high and spool valve member  40  is preferably hydraulically balanced and maintained in its retracted position by biasing spring  49 . When spool valve member  40  is in this position, device control passage  52  is blocked from fluid communication with high pressure passage  44  but fluidly connected to low pressure passage  47  via low pressure annulus  45 . Conversely, when variable pressure passage  35  is fluidly connected to low pressure reservoir  12 , such as when pilot valve member  31  is in its first position, pressure within spool cavity  53  is sufficiently low that the high pressure acting on high pressure surface  41  can to overcome the force of biasing spring  49 , and spool valve member  40  can move to its advanced position. When spool valve member  45  is in this advanced position, device control passage  52  is blocked from low pressure passage  47  but high pressure fluid can flow into device control passage  52  via high pressure annulus  42  and high pressure passage  44 .  
         [0018]    Device control passage  52  is fluidly connected to a first device fluid supply passage  55  and a second device fluid supply passage  56 . First device fluid supply passage  55  acts to fluidly connect device control passage  52  to a actuation fluid passage  70  (FIG. 3) defined by an injector body provided by fuel injector  60 . Second device fluid supply passage  56  fluidly connects device control passage  52  to a brake fluid passage  93  (FIG. 4) defined by a brake body  91  provided by engine brake  90 . As indicated, a modified brake/injector actuator control valve  24  could be substituted for brake/injector actuator control valve  24  and valve  23  illustrated herein. It should be appreciated that in this instance, first device supply passage  55  and second device fluid supply passage  56  would not be in fluid communication with a single device control passage  52 . Rather, in this instance, device control passage  52  would be a first device control passage fluidly connected to first device fluid supply passage  56  and valve body  25  would define a second device control passage that would be in fluid communication with second device fluid supply passage  56 . By independently controlling the connection of the first device control passage and the second device control passage to high pressure manifold  14  and low pressure reservoir  12 , this modified actuator control valve could replace both brake/injector actuator control valve  24  and valve  23  without departing from the scope of the present invention.  
         [0019]    Referring in addition to FIG. 3, there is shown a fuel injector  60  according to the present invention. Injector body  61  provides an electrical actuator  62 , which is preferably a solenoid, that has an armature  64  attached to a needle control valve member  65 , which is positioned in injector body  61  and movable between an upward position and a downward position. Those skilled in the art will recognize that electrical actuator  62  could instead be a piezoelectric actuator. Valve member  65  is preferably hydraulically balanced and biased toward its downward position by a biasing spring  63 . Valve member  65  is preferably substantially identical in form and function to the pilot valve of actuator control valve  24 . Actuation fluid passage  70  and pressure passage  66  are fluidly connected to either high pressure manifold  14  or low pressure reservoir  12  via device control passage  52  and first device fluid supply passage  56 . When electrical actuator  62  is de-energized, such as between injection events, valve member  65  is moved to its downward position by the force of biasing spring  63  closing low pressure seat  67 . When valve member  65  is in this position, a pressure communication passage  71  defined by injector body  61  is in fluid communication with pressure passage  66 . When electrical actuator  62  is energized, such as just prior to an injection event, valve member  65  is preferably pulled to its upward position by armature  64  to open low pressure seat  67  and close high pressure seat  68 . When valve member  65  is in this position, pressure communication passage  71  is blocked from fluid communication with pressure passage  66  and open to a low pressure passage  69  that is defined by injector body  61 .  
         [0020]    While fuel injector  60  has been illustrated creating a flow path between actuation fluid passage  70  and pressure communication passage  71 , it should be appreciated that injector body  61  could be modified to eliminate this flow path. For instance, injector body  61  could instead define a fluid passage that is in fluid communication with high pressure manifold  14  directly, or with fuel pressurization chamber  76 . When electrical actuator  62  is de-energized, valve member  65  is moved to its downward position under the force of biasing spring  63 . In this instance, closing hydraulic surface  79  would be exposed to high pressure fluid in needle control chamber  84  whenever electrical actuator  62  is de-energized, and high pressure exists in passage  70 .  
         [0021]    Returning to fuel injector  60 , an intensifier piston  72  is positioned in injector body  61  and includes a hydraulic surface  73  that is exposed to fluid pressure in actuation fluid passage  70 . Piston  72  is biased toward a retracted, upward position by a biasing spring  74 . However, when pressure within actuation fluid passage  70  is sufficiently high, such as when it is open to high pressure passage  44  via device control passage  52 , piston  72  can move to an advanced, downward position against the action of biasing spring  74 . A plunger  75  is also movably positioned in injector body  61  and moves in a corresponding manner with piston  72 . When piston  72  is moved toward its advanced position, plunger  75  also advances and acts to pressurize fuel within a fuel pressurization chamber  76  that is connected to a fuel inlet  78  past a check valve. Fuel inlet  78  is in fluid communication with fuel source  21  via a fuel supply line. During an injection event as plunger  75  moves toward its downward position, the check valve is closed and plunger  75  can act to compress fuel within fuel pressurization chamber  76 . When plunger  75  is returning to its upward position, fuel is drawn into fuel pressurization chamber  76  past the check valve. Fuel pressurization chamber  76  is fluidly connected to a nozzle outlet  88  via a nozzle supply passage  77 .  
         [0022]    Returning to fuel injector  60 , a direct control needle valve  80  is positioned in injector body  61  and has a needle valve member  82  that is movable between a first position, in which nozzle outlet  88  is open, and a downward second position in which nozzle outlet  88  is blocked. Needle valve member  82  is mechanically biased toward its downward closed position by a biasing spring  81 . Needle valve member  82  has an opening hydraulic surface  83  that is exposed to fluid pressure within a nozzle chamber  85  and a closing hydraulic surface  79  that is exposed to fluid pressure within a needle control chamber  84 . Pressure communication passage  71  is in fluid communication with needle control chamber  84  and controls fluid pressure within the same.  
         [0023]    Closing hydraulic surface  79  and opening hydraulic surface  83  are preferably sized such that even when a valve opening pressure is attained in nozzle chamber  85 , needle valve member  82  will not lift open when needle control chamber  84  is fluidly connected to high pressure manifold  14  via brake/injector actuator control valve  24  and pressure communication passage  71 . However, it should be appreciated that the relative sizes of closing hydraulic surface  79  and opening hydraulic surface  83  and the strength of biasing spring  81  should be such that when closing hydraulic surface  79  is exposed to low pressure in needle control chamber  84 , a valve opening pressure acting on opening hydraulic surface  83  should be sufficient to move needle valve member  82  upward against the force of biasing spring  81  to open nozzle outlet  88 . It should be further appreciated that the strength of biasing spring  81  should be such that needle valve member  82  will remain in its closed position even when pressure communication passage  71 , and therefore needle control chamber  84  are open to low pressure reservoir  12  via device control passage  52 .  
         [0024]    Referring now to FIG. 4, there is shown an engine brake  90  according to the present invention. Engine brake  90  is preferably any engine brake that is positioned in engine  10  to vent compressed air within cylinder  19  toward the end of the compression stroke of piston  20 . It is known in the art that injection and combustion are not always necessary, or desirable, during each cycle of piston  20 . One such time might be when a vehicle having engine  10  is descending a relatively steep hill. During the descent, injection and combustion are not necessary and instead braking is often desirable. To increase efficiency of engine  10 , and to decrease undesirable emissions created during unnecessary combustion, an engine brake, such as engine brake  90 , is preferably operably coupled to each cylinder  19  of engine  10 . When combustion is not desired, fuel is not injected into cylinder  19  at the end of the compression stroke, but instead, the compression of air in cylinder  19  during the compression stroke provides braking power for engine  10 . This energy is released by engine brake  90  instead of being recovered as piston  20  retracts toward its downward position.  
         [0025]    Returning to engine  10  and engine brake  90 , as illustrated, brake/injector actuator control valve  24  functions as a flow control valve for engine brake  90 . Engine brake  90  has a brake body  91  that defines a brake fluid passage  93  and a brake control inlet  92 . Brake control inlet  92  and brake fluid passage  93  are fluidly connected to high pressure manifold  14  via device control passage  52  and second device fluid supply passage  56  when two way valve  23  is in its open position. A hydraulic actuator, piston  95 , is positioned in brake body  91  and is movable between a retracted, upward position and an advanced, downward position. It should be appreciated that in addition to the hydraulic actuator provided in engine brake  90 , the engine valve for cylinder  19  could also have a conventional actuator that is coupled to the cam shaft.  
         [0026]    Piston  95  is biased toward its retracted position by a biasing spring  97 . When two way valve  23  is in its closed position, brake fluid passage  93  remains at low pressure and piston  95  remains in its retracted position. When in this position, engine brake  90  is deactivated to prevent venting of engine from engine cylinder  19 . However, when two way valve  23  is in its open position and actuator control valve  24  is activated, brake fluid passage  93  is fluidly connected to high pressure manifold  14 . When this occurs, piston  95  is moved to its advanced position away from a seat component  99  against the action of biasing spring  97 , and engine brake  90  can open cylinder  19  to an exhaust passage  98 .  
       INDUSTRIAL APPLICABILITY  
       [0027]    Referring to FIGS.  1 - 4 , operation of the present invention will be discussed for one engine cylinder  19 . It should be appreciated that while different cylinders are operating at different stages of their intake-compression-power-exhaust cycles at one time, the present invention operates in the same manner for each cylinder. Recall, in addition, that the present invention is being described for use with a four cylinder, four cycle engine  10 . However, it should be appreciated that brake/injector actuator control valve  24  would find application in engines having a different number of cylinders or for those with cylinders operating under a different number of cycles.  
         [0028]    Prior to the intake stage for cylinder  19 , brake/injector actuator control valve  24  is in its first position such that pilot valve member  31  is in its second position, as shown, and spool valve member  40  is in its retracted position such that device control passage  52  is fluidly connected to low pressure reservoir  12 . Two way valve  23  is in its closed position such that engine brake  90  is in an off or disabled condition, and cylinder  19  is closed to exhaust passage  98 . Needle control valve member  65  of fuel injector  60  is in its downward, biased position, such that pressure communication passage  71  is fluidly connected to low pressure reservoir  12 . Both closing hydraulic surface  79  and opening hydraulic surface  85  are exposed to low pressure, and needle valve member  82  is thus held in its downward position to close nozzle outlet  88  under the action of biasing spring  81 . In addition, with low pressure acting on hydraulic surface  73 , piston  72  and plunger  75  are in their upward, biased positions.  
         [0029]    As engine piston  20  moves downward toward its bottom position, it draws air into cylinder  19  via the intake valve. Upon reaching its bottom dead center position, the intake stroke is ended and piston  20  begins to advance toward its upward position to compress the air that has been drawn into cylinder  19 . Preferably, it is during this advancing movement of piston  20  that electronic control module  17  determines if fuel injection will be desirable at the end of the compression stroke. If it is, electrical actuator  26  is energized to move pilot valve member  31  to its upward, first position. However, it should be appreciated that this determination could be made at any suitable time prior to the end of the compression stroke of piston  20 .  
         [0030]    In order to initialize either an injection event or a actuation event, actuator control valve  24  is activated and moved to its second position. This begins by energizing solenoid coil  28  to move pilot valve member  31  upward to close high pressure seat  32 . When pilot valve member  31  moves upward to its first position to close high pressure seat  32 , variable pressure passage  35  is fluidly connected to low pressure reservoir  12 . Hydraulic surface  54  of spool valve member  40  is now exposed to low pressure in spool cavity  53 , and spool valve member  40  is moved to its advanced position by the high pressure acting on high pressure surface  41 . Device control passage  52  is now open to high pressure passage  44  via high pressure annulus  42 . High pressure fluid can now flow into first device fluid supply passage  55  and second device fluid supply passage  56 . However, brake fluid passage  93  of engine brake  90  is not fluidly connected to high pressure manifold  14  because two way valve  23  remains in its closed position.  
         [0031]    With high pressure actuation fluid flowing into actuation fluid passage  70 , piston  72  and plunger  75  begin to move toward their advanced positions to pressurize fuel in fuel pressurization chamber  76  and nozzle chamber  85 . However, because closing hydraulic surface  79  is now exposed to high pressure in needle control chamber  84  via pressure communication passage  71 , needle valve member  82  will not be moved to its upward position to open nozzle outlet  88 . Further, it should be appreciated that piston  72  and plunger  75  move only a slight distance at this time because of hydraulic locking, which is a result of nozzle outlet  88  remaining closed. However, the slight movement of piston  72  and plunger  75  is still sufficient to raise fuel pressure within fuel pressurization chamber  76  to injection pressure levels.  
         [0032]    Just prior to the desired start of injection, when piston  19  is near its top dead center position to end the compression stroke, electrical actuator  62  is energized and pin  68  pulls valve member  65  toward its upward position blocking pressure communication passage  71  from the high pressure in pressure passage  66  and opening it to low pressure passage  69 . Needle control chamber  84  is now open to low pressure. Because high pressure is no longer acting on closing hydraulic surface  79 , the fuel pressure in nozzle chamber  85  is sufficient to overcome the bias of biasing spring  81  and needle valve member  82  moves to its open position to allow fuel injection into cylinder  19 . As previously discussed, this fuel injection from injector  60  is timed to coincide with the end of the compression stroke of piston  20 . When fuel is injected into cylinder  19 , it ignites instantly due to the high temperature of the compressed air within cylinder  19 . This combustion drives piston  20  downward for its power stroke.  
         [0033]    Returning to fuel injector  60 , when the desired amount of fuel has been injected into cylinder  19 , electrical actuator  62  is de-energized and valve member  65  is returned to its downward position under the force of biasing spring  63  to open high pressure seat  68 . Pressure communication passage  71  is now open to high pressure, thus exposing closing hydraulic surface  79  to high pressure fluid in needle control chamber  84 . The high pressure acting on closing hydraulic surface  79  is sufficient to move needle valve  82  downward to close nozzle outlet  88  and end injection. However, because of hydraulic locking, piston  72  and plunger  75  stop their advancing movement, but do not immediately begin to retract because hydraulic surface  73  is still exposed to high pressure fluid in actuation fluid passage  70 . It should be appreciated that if a split injection is desired, electrical actuator  62  would be re-energized and valve member  65  would be returned to its upward position fluidly connecting pressure communication passage  71  to low pressure passage  69 . With closing hydraulic surface  79  once again exposed to low pressure, and with high pressure still acting on opening hydraulic surface  85 , needle valve member  82  would once again be moved to its open position.  
         [0034]    Once the injection event is completed, electrical actuator  26  is de-energized to allow brake/injector actuator control valve  24  to return to its first position, thus allowing pilot valve member  31  to return to its downward position, closing low pressure seat  33 . Variable pressure passage  35  is now open to high pressure passage  44 . Hydraulic surface  54  is exposed to high pressure within spool cavity  53 , and spool valve member  40  once again becomes hydraulically balanced and begins to move toward its upward position under the action of biasing spring  49 . Device control passage  52  is now blocked from high pressure passage  44  and open to low pressure passage  47 , thus opening first device fluid supply passage  55  and second device fluid supply passage  56  to low pressure fluid. However, because two way valve  23  remains in its closed position, engine compression release brake valve  90  continues to be inactive.  
         [0035]    Once first device fluid supply passage  55  is opened to low pressure passage  47 , pressure within actuation fluid passage  70  is reduced and piston  72  and plunger  75  can return to their upward positions. As plunger  75  retracts, fuel from fuel source  21  can be drawn into fuel pressurization chamber  76  via fuel inlet  78  past the check valve. Recall that while closing hydraulic surface  79  is exposed to low pressure fluid via pressure communication passage  71 , needle valve member  88  will remain in its closed position under the action of biasing spring  81  due to the low fluid pressure acting on opening hydraulic surface  85 . As the components of fuel injector  60  are resetting themselves, piston  20  is advancing toward its top dead center position for its exhaust stroke to vent any residue from injection out of cylinder  19  via the engine compression release brake valve.  
         [0036]    During a typical engine cycle, once piston  20  reaches the bottom dead center position for its power stroke, it begins to advance again for the exhaust stroke of the cylinder cycle. In other words, the engine exhaust valve is opened for the duration of the movement of piston  20  from its bottom dead center position to its top dead center position, and post combustion products remaining in cylinder  19  can be vented. In some instances, when piston  20  is advancing toward the top dead center position of its compression stroke, electronic control module  17  and/or the operator determine that fuel injection is not desirable, and instead engine brake  90  should be activated. At about top dead center, electrical actuator  26  of brake/injector actuator control valve  24  is again energized and moved to its second position, causing pilot valve member  31  to be moved to its upward position fluidly connecting variable pressure passage  35  to low pressure reservoir  12 . Hydraulic surface  54  of spool valve member  40  is again exposed to low pressure in spool cavity  53 , and spool valve member  40  is moved to its advanced position by the high pressure acting on high pressure surface  41 . Device control passage  52 , first device fluid supply passage  55  and second device fluid supply passage  56  are now open to high pressure passage  44  via high pressure annulus  42 . However, because high pressure fluid is acting on closing hydraulic surface  79  via pressure communication passage  71  fuel injector  60  is disabled and fuel injection will not take place so long as electrical actuator  62  remains de-energized to maintain valve member  65  in its downward position. To begin the venting portion of an engine braking event, two way valve  23  is moved to its open position.  
         [0037]    When two way valve  23  is in its open position, brake fluid passage  93  of engine brake  90  becomes fluidly connected to high pressure manifold  14  via second device fluid supply passage  56 . With brake fluid passage  93  now open to high pressure manifold  14 , piston  95  can advance against the bias of biasing spring  97 , and engine brake  90  can vent the contents of cylinder  19 . This preferably occurs as the piston  20  approaches its top dead center position during its compression stroke. In other words, in no contemplated case does the same cylinder undergo both an engine braking event and an injection event during the same cycle. It is this principal that allows a single actuator control valve, such as actuator control valve  24 , to be utilized in controlling the activation of both engine brake  90  and fuel injector  60 . Further, it is this principal that allows a modified actuator control valve, such as described to replace both actuator control valve  24  and valve  23 , to be utilized in controlling the activation of both engine brake  90  and fuel injector  60 . Once the compressed air has been vented from cylinder  19 , current to electrical actuator  26  can be ended, allowing pilot valve member  31  to return to its downward position and spool valve member  40  to return to its retracted position, fluidly connecting device control passage  52 , first device fluid supply passage  55  and second device fluid supply passage  56  to low pressure reservoir  12 . With piston  95  again exposed to low pressure, it can return to its retracted position under the action of biasing spring  97  to close the exhaust port. Two way valve  23  is now returned to its closed position in anticipation of a subsequent engine braking or injection event.  
         [0038]    It should be appreciated that the present invention provides a number of advantages over prior engine systems. For instance, because the fluid control line to the needle valve hydraulic surface has been separated from the fluid control line for the spool, greater control of the injection event can occur. In addition, because the number of fluid control valves has been reduced, the engine can be more robust. Further, because there are fewer working components within the engine, there are fewer components that can fail during engine operation.  
         [0039]    It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present invention in any way. For instance, while the present invention has been illustrated controlling only the fuel injector and the engine brake for each cylinder, it should be appreciated that it could also control a hydraulic intake valve for the cylinder. Additionally, while the present invention has been illustrated including a fuel injector having a flow path between the brake/injector actuator control valve and the closing hydraulic surface of the needle valve member, it should be appreciated that this flow path could be eliminated and replaced by a high pressure passage, as discussed above. Further, while the present invention has been illustrated including an actuator control valve and a two-way valve for each cylinder, it should be appreciated that a modified actuator control valve could be substituted to replace both of these components. For instance, a single actuator control valve, such as a rotary valve, could be utilized to control both the fuel injector and the engine brake by including separate hydraulic actuation lines that could be fluidly connected to each device, thereby eliminating the need for a valve to activate or deactivate one or both of the devices. Those skilled in the art will appreciate that if a non-direct-control fuel injector is used, some other means to disable the injector for an engine brake event would be needed. Such an alternative might utilize a three-way valve as a substitute for a two-way valve  23  described above. The three-way valve would have different positions that enable either the fuel injector or the engine brake, but not both simultaneously. Thus, those skilled in the art will appreciate that other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims.