Abstract:
The present invention relates to engines having multiple hydraulic devices. For instance, in a typical multi-cylinder diesel engine, each cylinder includes an intake valve, an exhaust valve, a fuel injector and an engine brake. It is common for each of these devices to be controlled by an individual actuator. However, engineers have learned that decreasing the number of engine components can increase engine robustness. Therefore, the present invention utilizes a single rotary actuator to control multiple hydraulic devices for an engine cylinder.

Description:
TECHNICAL FIELD 
   This invention relates generally to engines, and more particularly to valves for controlling hydraulically actuated fuel injectors and engine brakes. 
   BACKGROUND 
   In several diesel engines today, a number of hydraulically actuated devices, such as hydraulically actuated fuel injectors and engine compression release brakes, are coupled to each engine cylinder. Typically, each of these devices is controlled by an 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. The control valve controls fluid pressure to both an intensifier piston and a direct control needle valve included in the injector body. While fuel injectors, and other hydraulic devices, including individual fluid control valves have performed adequately, there is 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. Therefore, an engine including a single fluid control valve for each cylinder would find particular use in the industry. 
   The present invention is directed to overcoming one or more of the problems as set forth above. 
   SUMMARY OF THE INVENTION 
   In one aspect of the present invention, a hydraulic system has a rotary valve that has a valve body defining a plurality of passages. An electronic control module is in control communication with the rotary valve. A high pressure source is fluidly connected to one of the plurality of passages. A first hydraulic device and a second hydraulic device are fluidly connected to the rotary valve. The rotary valve has a first angular position in which the first hydraulic device is fluidly connected to the high pressure source. The rotary valve has a second angular position in which the second hydraulic device is fluidly connected to the high pressure source. 
   In another aspect of the present invention, an engine has an engine housing defining a plurality of cylinders and a rotary valve for each of the plurality of cylinders. An electronic control module is in control communication with the rotary valve. A first hydraulic device and a second hydraulic device for each of the plurality of cylinders are attached to the engine housing. A source of high pressure fluid is fluidly connected to the rotary valve. The rotary valve has a first angular position in which the first hydraulic device is fluidly connected to the source of high pressure fluid. The rotary valve has a second angular position in which the second hydraulic device is fluidly connected to the source of high pressure fluid. 
   In yet another aspect of the present invention, a method of controlling multiple hydraulic devices includes providing a rotary valve that has a valve body defining a high pressure passage. The rotary valve is placed in control communication with an electronic control module. The high pressure passage is fluidly connected to a high pressure fluid source. The rotary valve is fluidly connected to a first hydraulic device and a second hydraulic device. The rotary valve is rotated to a first angular position that fluidly connects the high pressure passage to the first hydraulic device. The rotary valve is then rotated to a second angular position fluidly connecting the high pressure passage to the second hydraulic device. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic representation of an engine according to the present invention; 
       FIG. 2  is a sectioned side diagrammatic representation of a hydraulically actuated fuel injector fluidly connected to a rotary valve according to the present invention; 
       FIG. 3  is an enlarged sectioned view of the top portion of the fuel injector of  FIG. 2 ; 
       FIG. 4  is sectioned side diagrammatic representation of an engine compression release brake fluidly connected to a rotary valve according to the present invention; 
       FIG. 5  is a sectioned top diagrammatic representation of a rotary valve member in a first position according to the present invention; 
       FIG. 6  is a sectioned top diagrammatic representation of the rotary valve member of  FIG. 6  in a second position; 
       FIG. 7  is a sectioned top diagrammatic representation of the rotary valve member of  FIG. 6  in a third position; and 
       FIG. 8  is a sectioned top diagrammatic representation of the rotary valve member of  FIG. 6  in a fourth position. 
   

   DETAILED DESCRIPTION 
   Referring to  FIG. 1  there is shown an engine  9  according to the present invention. A low pressure reservoir  11  is provided in engine  9  and preferably includes an amount of low pressure engine lubricating oil. While low pressure reservoir  11  is preferably an oil pan that has 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  12  pumps oil from low pressure reservoir  11  and delivers the same to high pressure manifold  13 . High pressure oil flowing out of high pressure manifold  13  is delivered via high pressure fluid supply line  14  to a hydraulic system provided in engine  9  and oil is returned to low pressure reservoir  11  via low pressure return line  15  after it has performed work in the hydraulic system. Engine  9  also has an engine housing  10  that defines a plurality of cylinders  17 . 
   Each of the cylinders  17  defined by engine housing  10  has a movable piston  18 . Each piston  18  is movable between a retracted, downward position and an advanced, upward position. For a typical four cycle diesel engine  9 , the advancing and retracting strokes of piston  18  correspond to the four stages of engine  9  operation. When piston  18  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  17  via an intake valve. When piston  18  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  17  is compressed. At around the end of the compression stroke, fuel can be injected into cylinder  17  by fuel injector  40 , and combustion within cylinder  17  can occur instantly, due to the high temperature of the compressed air. This combustion drives piston  18  downward toward its bottom dead center position, for the power stroke of piston  18 . Finally, when piston  18  once again advances from its bottom dead center position to its top dead center position, post combustion products remaining in cylinder  17  can be vented via an exhaust valve, corresponding to the exhaust stroke of piston  18 . While engine  9  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  10 . 
   Each cylinder  17  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  40  and an engine compression release brake  90 . Fuel injector  40  is fluidly connected to a fuel tank  19  and delivers fuel to cylinder  17  for combustion while engine brake  90  controls release of compressed air from cylinder  17  when combustion is not desirable. A rotary valve  21  is fluidly connected to the fuel injector  40  and engine brake  90  of each cylinder. Rotary valve  21  can act as either a fluid switch or a pressure switch for fuel injector  40  and engine brake  90 . Rotary valve  21  is controlled in operation by an electronic control module  16  via communication line  20 . 
   Referring to  FIGS. 2 and 3  there is shown a sectioned view through a fuel injector  40  fluidly connected to rotary valve  21 . Rotary valve  21  has a valve body  22  that defines a rotary valve bore  26 . A rotary actuator  24  of rotary valve  21  that is in control communication with electronic control module  16 . Rotary actuator  24  is preferably a stepper motor but could be any suitable rotary activator. Rotary actuator  24  is connected to a rotary valve member  23  via an axial member  24 . Valve body  22  also defines a high pressure passage  36  and a low pressure passage  35  that are fluidly connected to high pressure manifold  13  and low pressure reservoir  11 , respectively. Depending on the angular position of valve member  23  within valve bore  26 , high pressure passage  36  and low pressure passage  35  can be fluidly connected to one or more of a spool control passage  32 , a needle control passage  33  and an engine brake control passage  34 , all defined by valve body  22 . 
   A spool communication passage  37  and a needle valve communication passage  38  fluidly connect rotary valve  21  to fuel injector  40 . Fuel injector  40  has an injector body  41  with a spool valve member  45  that is movably positioned between an upward, retracted position and a downward, advanced position. Spool valve member  45  is biased toward its upward position, as shown, by a biasing spring  46 . Spool valve member  45  has a high pressure annulus  51  that is always open to a high pressure passage  59  and is positioned such that it can open an actuation fluid passage  58  to high pressure passage  59  when spool valve member  45  is in its advanced position. A low pressure annulus  52  is also provided on spool valve member  45  that can connect actuation fluid passage  58  to a low pressure passage  54  defined by injector body  41  when spool valve member  45  is in its retracted position. Spool valve member  45  has a control surface  55  that is exposed to fluid pressure in a spool cavity  56 , and a high pressure surface  48  that is continuously exposed to high pressure in high pressure passage  59  via a number of radial passages  50  defined by spool valve member  45 . Spool cavity  56  is fluidly connected to a variable pressure passage  57  and a spool control inlet  42  that are defined by injector body  41 . Variable pressure passage  57  is open to either low pressure reservoir  11  or high pressure manifold  13 , via spool pressure communication passage  37  and spool control passage  32 . 
   When variable pressure passage  57  is fluidly connected to high pressure manifold  13  by rotary valve  21 , pressure within spool cavity  56  is high and spool valve member  45  is preferably hydraulically balanced and maintained in its upward position by biasing spring  46 . When spool valve member  45  is in this position, actuation fluid passage  58  is blocked from fluid communication with high pressure passage  59  but fluidly connected to low pressure passage  54  via low pressure annulus  52 . Conversely, when variable pressure passage  57  is fluidly connected to low pressure reservoir  11  by rotary valve  21 , pressure within spool cavity  56  is sufficiently low that the high pressure acting on high pressure surface  48  can to overcome the force of biasing spring  46 , and spool valve member  45  can move to its lower position. When spool valve member  45  is in this lower position, actuation fluid passage  58  is blocked from low pressure passage  54  but high pressure fluid can flow into actuation fluid passage  58  via high pressure annulus  51  and high pressure passage  59 . Thus, rotary valve  21  acts as a pressure switch with respect to fuel injector  40 , with no substantial flow volume therethrough. 
   Returning now to fuel injector  40 , an intensifier piston  65  is movably positioned in injector body  41  and has a hydraulic surface  66  that is exposed to fluid pressure in actuation fluid passage  58 . Piston  65  is biased toward a retracted, upward position by a biasing spring  70 . However, when pressure within actuation fluid passage  58  is sufficiently high, such as when it is open to high pressure passage  59 , piston  65  can move to an advanced, downward position against the action of biasing spring  70 . A plunger  68  is also movably positioned in injector body  41  and moves in a corresponding manner with piston  65 . When piston  65  is moved toward its advanced position, plunger  68  also advances and acts to pressurize fuel within a fuel pressurization chamber  72  that is connected to a fuel inlet  73  past a check valve  74 . Fuel inlet  73  is in fluid communication with fuel source  19  via a fuel supply line  75 . During an injection event as plunger  68  moves toward its downward position, check valve  74  is closed and plunger  68  can act to compress fuel within fuel pressurization chamber  72 . When plunger  68  is returning to its upward position, fuel is drawn into fuel pressurization chamber  72  past check valve  74 . Fuel pressurization chamber  72  is fluidly connected to a nozzle outlet  88  via a nozzle supply passage  83 . 
   A pressure relief valve  60  is movably positioned in injector body  41  to vent pressure spikes from actuation fluid passage  58 . Pressure spikes can be created when piston  65  and plunger  68  abruptly stop their downward movement due to the abrupt closure of nozzle outlet  88 . Because pressure spikes can sometimes cause an uncontrolled and undesirable secondary injection due to an interaction of components and passageways over a brief instant after main injection has ended, a pressure relief passage  63  extends between actuation fluid passage  58  and a low pressure vent. When spool valve member  45  is in its downward position, such as during an injection event, a pin  61  holds pressure relief valve  60  downward to close a seat  62 . When pressure relief valve  60  is in this position, actuation fluid passage  58  is closed to pressure relief passage  63  and pressure can build within actuation fluid passage  58 . However, between injection events, when piston  65  and plunger  68  are hydraulically locked, residual high pressure in actuation fluid passage  58  can act against pressure relief valve  60 . Because pressure within spool cavity  56  is high, spool valve member  45  is hydraulically balanced and can move toward its upward position under the action of biasing spring  46 . Pressure relief valve  60  can then lift off of seat  62  to open actuation fluid passage  58  to pressure relief passage  63 , thus allowing pressure within actuation fluid passage  58  to be reduced. At the same time, upward movement of pressure relief valve  60 , and therefore pin  61  can aid in the movement of spool valve member  45  toward its upward position. 
   Returning to fuel injector  40 , a direct control needle valve  80  is positioned in injector body  41  and has a needle valve member  82  that is movable between a first position, in which a 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  78 . Needle valve member  82  has an opening hydraulic surface  85  that is exposed to fluid pressure within a nozzle chamber  84  and a closing hydraulic surface  81  that is exposed to fluid pressure within a needle control chamber  77 . A pressure communication passage  76  is in fluid communication with needle control chamber  77  and controls fluid pressure within the same. Pressure communication passage  76  is in fluid communication with rotary valve  21  via a needle valve control inlet  43  defined by injector body  41  and needle valve communication passage  38 . Depending on the angular position of valve member  23  within valve bore  26 , needle control chamber  77  can be fluidly connected to either high pressure manifold  13  or low pressure reservoir  11  via needle control passage  33 . 
   Closing hydraulic surface  81  and opening hydraulic surface  85  are preferably sized such that even when a valve opening pressure is attained in nozzle chamber  84 , needle valve member  82  will not lift open when needle control chamber  77  is fluidly connected to high pressure manifold  13  via rotary valve  21  and pressure communication passage  76 . However, it should be appreciated that the relative sizes of closing hydraulic surface  81  and opening hydraulic surface  85  and the strength of biasing spring  78  should be such that when closing hydraulic surface  81  is exposed to low pressure in needle control chamber  77 , the high pressure acting on opening hydraulic surface  85  should be sufficient to move needle valve member  82  upward against the force of biasing spring  78  to open nozzle outlet  88 . 
   Referring now to  FIG. 4 , there is shown an engine brake  90  fluidly connected to rotary valve  21  according to the present invention. Engine brake  90  is preferably any engine brake that is positioned in engine  9  to vent compressed air within cylinder  17  toward the end of the compression stroke of piston  18 . It is known in the art that injection and combustion are not always necessary, or desirable, during each cycle of piston  18 . One such time might be when a vehicle having engine  9  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  9 , and to decrease undesirable emissions created during unnecessary combustion, an engine brake, such as engine brake  90 , is preferably operably coupled to each cylinder  17  of engine  9 . When combustion is not desired, fuel is not injected into cylinder  17  at the end of the compression stroke, but instead, the compression of air in cylinder  17  during the compression stroke provides braking power for engine  9 . This energy is released by engine brake  90  instead of being recovered as piston  18  retracts toward its downward position. 
   Returning to engine  9  and engine brake  90 , as illustrated, rotary valve  21  functions as a flow control valve for engine brake  90 . Engine brake  90  has an engine brake body  91  that defines a fluid passage  93  and an engine brake control inlet  92 . Engine brake control inlet  92  and fluid passage  93  are fluidly connected to either high pressure manifold  13  or low pressure reservoir  11  via an engine brake control passage  34  defined by rotary valve  21  and an engine brake communication passage  39 . A hydraulic actuator, piston  95 , is positioned in engine 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 exhaust valve for cylinder  17  could also have a conventional actuator that is coupled to the cam shaft. 
   Piston  95  is biased toward its retracted position by a biasing spring  97 . When fluid passage  93  is fluidly connected to low pressure reservoir  11 , piston  95  remains in its retracted position, and engine brake  90  is deactivated to prevent venting of exhaust from engine cylinder  17 . However, when fluid passage  93  is fluidly connected to high pressure manifold  13 , piston  95  is moved to its advanced position toward a seat component  99  against the action of biasing spring  97 , and engine brake  90  can open cylinder  17  to an exhaust passage  98 . While rotary valve  21  has been illustrated to function as a flow control valve for engine brake  90 , it should be appreciated that rotary valve  21  could instead function as a pressure switch for engine brake  90 . In that case, the top portion of engine brake  90  could be substantially similar to the top portion of fuel injector  40 , as illustrated in FIG.  3 . For instance, in that case engine brake  90  could have a spool valve, such as spool valve  45 , that controls pressure above piston  95 . 
   Referring to  FIGS. 5-8 , rotary valve  21  has been shown with valve member  23  in each of its four angular positions. Recall that rotary valve  21  is acting as a pressure switch for fuel injector  40  and as a fluid switch for engine brake  90 . It should be appreciated that if rotary valve  21  were acting in a different capacity for either one or both of these hydraulic devices, the angular positions of valve member  23  would correspond to the connection of different passages within fuel injector  40  and engine brake  90  to high pressure source  13  and low pressure reservoir  11 . As illustrated in  FIG. 5 , when rotary valve  21  is in its first angular position, engine brake control passage  34  is open to low pressure passage  35 , while spool control passage  32  and needle control passage  33  are fluidly connected to high pressure passage  36 . When valve member  23  is in this position, fluid passage  93  of engine brake  90  is open to low pressure reservoir  11  while variable pressure passage  57  and pressure communication passage  76  are open to high pressure manifold  13 . In other words, when rotary valve  21  is in this angular position, engine brake  90  is deactivated and fuel injector  40  is between fuel injection events. 
   As illustrated in  FIG. 6 , when rotary valve member  23  is in its second position, both engine brake control passage  34  and spool control passage  32  are open to low pressure reservoir  11 , while needle control passage  33  is open to high pressure manifold  13 . Fluid passage  93  remains fluidly connected to low pressure reservoir  11 , while variable pressure passage  57  is now blocked from high pressure manifold  13  and opened to low pressure reservoir  11 . When valve member  23  is in this position, pressure communication passage  76  remains open to high pressure manifold  13 . Therefore, engine brake  90  remains deactivated, while fuel injector  40  can prepare for fuel injection. In other words, spool valve member  45  can move toward its downward position to connect actuation fluid passage  58  to high pressure passage  59 . High pressure acting on hydraulic surface  66  can move piston  65  toward its downward position to allow fuel within fuel pressurization chamber  72  to be raised to injection pressure levels. 
   As illustrated in  FIG. 7 , when rotary valve member  23  is in its third position, engine brake control passage  34 , spool control passage  32  and needle control passage  33  are all open to low pressure reservoir  11  via low pressure passage  35 . This corresponds to engine brake  90 , variable pressure passage  57  and pressure communication passage  76  being fluidly connected to low pressure reservoir  11 . When rotary valve member  23  is in this position, engine brake  90  remains deactivated. However, because pressure communication passage  76  is now open to low pressure reservoir  11 , low pressure can act on closing hydraulic surface  81 . The fuel pressure in nozzle supply passage  83  is now sufficient to lift needle valve  82  and fuel can be injected from fuel injector  40 . 
   As illustrated in  FIG. 8 , when rotary valve member  23  is in its fourth position, engine brake control passage  34 , spool control passage  32  and needle control passage  33  are all open to high pressure manifold  13  via high pressure passage  36 . When rotary valve member  23  is in this position, piston  95  is exposed to high pressure in fluid passage  93  and can move toward its advanced position to open cylinder  17  to engine passage  98 . However, because pressure communication passage  76  is also open to high pressure, needle valve  82  is prohibited from lifting toward its upward position to open nozzle outlet  88 . Further, because variable pressure passage  57  is open to high pressure, spool valve member  45  can move toward its upward position, to close actuation fluid passage  58  from high pressure passage  59 , thus allowing piston  65  and plunger  68  to retract. 
   INDUSTRIAL APPLICABILITY 
   Referring to  FIGS. 1-8 , operation of the present invention will be discussed for one engine cylinder. It should be appreciated that while different cylinders are operating at different stages of their intake-compression-power-engine cycles at one time, the present invention operates in the same manner for each cylinder. Recall, in addition, that the rotary valve  21  of the present invention is being described for use with a four cylinder, four cycle engine  9 . However, it should be appreciated that rotary valve  21  would find application in engines having a different number of cylinders or for those with cylinders operating under a different number of cycles. In addition, while rotary valve  21  has been illustrated as a flow control valve for engine brake  90  and a pressure switch for fuel injector  40 , it should be appreciated that it could function as a pressure switch to control other valves for cylinder  17 . Similarly, rotary valve  21  could function as a flow control device to directly control activation of hydraulic devices in engine  9 . 
   Prior to the intake stage for cylinder  17 , valve member  23  is in its first angular position such that fluid passage  93  of engine brake  90  is fluidly connected to low pressure reservoir  11 . Low pressure is therefore acting on piston  95 , such that engine brake  90  is in an off condition and cylinder  17  is closed to exhaust passage  98 . At the same time, variable pressure passage  57  and pressure communication passage  76  are fluidly connected to high pressure manifold  13 . When valve member  23  is in this position, spool valve member  45  is in its upward position opening actuation fluid passage  58  to low pressure passage  54  such that piston  65  and plunger  68  are in their upward positions. Additionally, because closing hydraulic surface  81  is exposed to high pressure in needle control chamber  77  and pressure communication passage  76 , needle valve member  82  is held in its downward position to close nozzle outlet  88 . As engine piston  18  moves downward toward its bottom position it draws air into cylinder  17  via the intake valve. Upon reaching its bottom dead center position, the intake stroke is ended and piston  18  begins to advance toward its upward position to compress the air that has been drawn into cylinder  17 . Preferably, it is during this advancing movement of piston  18  that electronic control module  16  determines if fuel injection will be desirable at the end of the compression stroke. If it is, rotary actuator  24  rotates axial member  25  to move rotary valve member  23  to its second angular position to prepare fuel injector  40  for fuel injection. 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  18 . 
   When valve member  23  moves to its second angular position, fluid passage  93  remains fluidly connected to low pressure reservoir  11 , such that engine brake  90  will not vent the contents of cylinder  17 . In addition, pressure communication passage  76  remains fluidly connected to high pressure manifold  13  to prevent needle valve member  82  from opening nozzle outlet  88  to the combustion space. However, when valve member  23  is in this position, variable pressure passage  57  is blocked from fluid communication with high pressure manifold  13  and opened to low pressure reservoir  11 . Pressure within spool cavity  56  is now reduced and spool valve member  45  can move toward its downward position due to the high pressure acting on high pressure surface  48 . When spool valve member  45  advances, actuation fluid passage  58  becomes blocked from low pressure passage  54  and opened to high pressure passage  59  via high pressure annulus  51 . High pressure is now acting on hydraulic surface  66  causing piston  65  and plunger  68  to start moving toward their advanced positions to pressurize fuel in fuel pressurization chamber  72  and nozzle chamber  84 . However, because closing hydraulic surface  81  is exposed to high pressure in needle control chamber  77 , needle valve member  82  will not be moved to its upward position to open nozzle outlet  88 . Further, it should be appreciated that piston  65  and plunger  68  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  65  and plunger  68  is still sufficient to raise fuel pressure within fuel pressurization chamber  72  to injection pressure levels. 
   Just prior to the desired start of injection, when piston  18  is near its top dead center position to end the compression stroke, rotary valve member  23  is moved to its third angular position by rotary actuator  24 . Fluid passage  93  remains fluidly connected to low pressure reservoir  11  to prevent engine brake  90  from venting the contents of cylinder  17 . In addition, variable pressure passage  57  remains fluidly connected to low pressure reservoir  11  such that spool valve member  45  remains in its upward, retracted position fluidly connecting actuation fluid passage  58  to high pressure passage  48 . However, pressure communication passage  76  is now fluidly connected to low pressure reservoir via rotary valve  21  to expose needle control chamber  77  to low pressure. Because high pressure is no longer acting on closing hydraulic surface  81 , the fuel pressure in nozzle chamber  84  is sufficient to overcome the bias of biasing spring  78  and needle valve member  82  moves to its open position to allow fuel injection into cylinder  17 . As previously discussed, this fuel injection from injector  40  is timed to coincide with the end of the compression stroke of piston  18 . When fuel is injected into cylinder  17 , it ignites instantly due to the high temperature of the compressed air within cylinder  17 . This combustion drives piston  18  downward for its power stroke. 
   Returning to fuel injector  40 , when the desired amount of fuel has been injected into cylinder  17 , rotary valve member  23  is returned to its first angular position to allow the various components of fuel injector  40  to reset themselves in preparation for the next injection event. Variable pressure passage  57  becomes blocked from fluid communication with low pressure reservoir  11  and is opened to high pressure manifold  13 . The high pressure acting on closing hydraulic surface  81  is sufficient to move needle valve  82  downward to close nozzle outlet  88  and end injection. Because of hydraulic locking, piston  65  and plunger  68  stop their advancing movement, but do not immediately being to retract because of residual high pressure acting on hydraulic surface  66 . At this time, control surface  55  is exposed to high pressure within spool cavity  56 , and spool valve member  45  once again becomes hydraulically balanced and begins to move toward its upward position under the action of biasing spring  46 . Residual high pressure in actuation fluid passage  58  is sufficient to move pressure relief valve  60  upward away from seat  62  to fluidly connect actuation fluid passage  58  to pressure relief passage  63 . Pressure relief valve  60  can therefore help vent high pressure actuation fluid from actuation fluid passage  58  to prevent pressure spikes from causing undesired secondary injections. At the same time, the upward movement of pressure relief valve  60  causes pin  61  to aid spool valve member  45  in returning to its upward position. 
   Once actuation fluid passage  58  is opened to pressure relief passage  63 , pressure within actuation fluid passage  58  is reduced and piston  65  and plunger  68  can return to their upward positions. In addition, once spool valve member  45  is returned to its upward position, actuation fluid cavity is blocked from fluid communication with high pressure passage  59  and fluidly connected to low pressure passage  54 , which further reduces the pressure within actuation fluid passage  58 . As plunger  68  retracts, fuel from fuel source  19  can be drawn into fuel pressurization chamber  72  via fuel inlet  73  past check valve  74 . As the components of fuel injector  40  are resetting themselves, piston  18  is advancing toward its top dead center position for its exhaust stroke to vent any residue from injection out of cylinder  17  via the exhaust valve. 
   During a typical engine cycle, once piston  18  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 exhaust valve is opened for the duration of the movement of piston  18  from its bottom dead center position to its top dead center position, and post combustion products remaining in cylinder  17  can be vented. In addition to exhaust during this portion of the engine cycle, it is sometimes desirable to vent the compressed air from cylinder  17  at the end of the compression stroke using engine brake  90 . During these conditions, when piston  18  is advancing toward the top dead center position of its compression stroke, electronic control module  16  determines that fuel injection is not desirable, and instead engine brake  90  should be activated. Rotary valve member  23  is then moved to its fourth angular position by axial member  25 , rather than its second or third position as described above. When valve member  23  is in this position, variable pressure passage  57  and pressure communication passage  76  remain fluidly connected to high pressure manifold  13 . However, fluid passage  93  of engine brake  90  becomes fluidly connected to high pressure manifold  13  via rotary valve  21 . With fluid passage  93  now open to high pressure manifold  13 , piston  95  can advance against the bias of biasing spring  97 , and engine brake  90  can vent the contents of cylinder  17 . Once the compressed air has been vented from cylinder  17 , rotary valve member  23  can return to its first angular position to open fluid passage  93  to low pressure reservoir  11 , exposing piston  95  to low pressure and allowing the same to return to its retracted position under the action of biasing spring  97  to close the exhaust port. Rotary valve member  23  is now ready to return to its first angular position. 
   It should be appreciated that a number of modifications could be made to the present invention. For instance, while engine brake control passage  34  has been illustrated as a fluid supply passage, it could instead be a pressure communication passage, like spool control passage  32  and needle control passage  33 . In that instance, engine brake  90  would have a control valve, such as spool valve member  45 , positioned in fuel injector  40 . Engine brake control passage  34  would be positioned in a different location with respect to low pressure passage  35  and high pressure passage  36  for engine brake  90  to function properly. In other words, engine brake control passage  34  would need to be defined by valve body  22  such that it is fluidly connected to high pressure passage  36  when valve member  23  is in its first, second and third positions. This would allow a spool valve member, such as spool valve member  45 , to remain in its retracted position blocking an actuation fluid passage from communication with a high pressure passage. When valve member  23  is in its fourth position, engine brake control passage  34  would be open to low pressure passage  35 , such that the spool valve member could advance. In addition to the change in the orientation of engine brake control passage  34  with respect to high pressure passage  36  and low pressure passage  35 , it should be appreciated that the size of engine brake control passage  34  could also be modified. For instance, when rotary valve  21  is acting as a flow control valve, as illustrated herein, engine brake control passage  34  must be large enough for a sufficient amount of fluid to flow into fluid passage  93  to move piston  95  toward its downward position when it is connected to high pressure passage  36 . However, if rotary valve  21  were acting as a pressure switch, engine brake control passage  34  could be smaller in diameter and still communicate a sufficient amount of pressure to engine brake  90  to allow it to function as desired. 
   The present invention could also be modified to allow rotary valve  21  to replace both the fuel injector pilot valve member, as well as spool valve member  45 . In this modification, spool communication passage  37  would be replaced by a piston communication passage that is fluidly connected to actuation fluid passage  58 . Spool control passage  32 , defined by valve body  22 , would be replaced by a piston control passage oriented with respect to low pressure passage  35  and high pressure passage  36  such that piston  65  would function as desired. Unlike spool control passage  32 , which is a pressure communication passage, the piston control passage would be a fluid communication passage. In this instance, when valve member  23  is in its first position, the piston control passage would be exposed to low pressure passage  35 , such that piston  65  remains in its upward, retracted position. When valve member  23  is in its second and third position, the piston control passage would be open to high pressure passage  36  such that high pressure would act on hydraulic surface  66  of piston  65  to move the same toward its advanced position to aid in the pressurization of fuel within fuel pressurization chamber  72 . Finally, when valve member  23  is in its fourth position, the piston control passage would be reopened to low pressure passage  35  to allow piston  65  and plunger  68  to return to their retracted positions in preparation for the next injection event. 
   In addition to these modifications, it should be appreciated that still further modifications could be made to rotary valve  21  and engine  9 . For instance, rotary valve  21  could be used to replace the poppet valve in a HEUI-A fuel injector, as described in U.S. Pat. No. 5,713,520 issued to Glassey et al. on Feb. 3, 1998. Rotary valve  21  would function as described above for replacement of both the control valve and the spool valve of a HEUI-B injector. In addition, rotary valve  21  could also be modified to control the intake valve for cylinder  17 , in addition to controlling fuel injector  40  and engine brake  90 . This would find particular application in a camless engine in which exhaust, intake and injection are all hydraulically actuated by a single rotary valve for each cylinder. It should be appreciated that a single rotary valve, such as rotary valve  21 , can control all of these aspects of engine function because exhaust, braking, intake and injection all occur at different times during the engine cycle. 
   The rotary valve of the present invention provides advantages over engines and hydraulic systems that do not utilize such a valve for control of their hydraulic devices. For instance, because the number of fluid control valves has been reduced, the engine can be more robust. Utilization of a single control valve to control the hydraulic devices for the cylinder can reduce problems associated with timing, because there is no need to coordinate the operation of multiple devices. For instance, because a single control valve is controlling both the fuel injector and the engine brake, these devices cannot be activated at the same time. Further, the smaller the number of working components within the engine, the smaller the number of components that can fail during engine operation. 
   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 rotary valve of the present invention has been illustrated as controlling only an engine brake and a hydraulically actuated fuel injector, it should be appreciated that it could additionally control an intake valve for the cylinder. Further, while the rotary valve has been illustrated controlling a fuel injector having a spool valve that controls fluid pressure in the actuation fluid cavity, it should be appreciated that the rotary valve could replace both the pilot valve and the spool valve for a HEUI-A fuel injector, as illustrated herein. It should be appreciated that the spool control outlet of the rotary valve would be replaced with a piston control outlet, and further that this outlet would be connected to high or low pressure at different times than the spool control outlet. Thus, those skilled in the art will appreciate that other aspects and features of the present invention can be obtained from a study of the drawings, the disclosure, and the appended claims.