Abstract:
Inclusion of a direct control needle valve in fuel injectors can allow for independent control of injection pressure and timing. Engineers have learned that it is desirable to position the control valve assembly in close proximity to the needle valve member to improve response time. However, by placing the control valve assembly in a central portion of the fuel injector, at least one fluid passage must often be routed through the electrical actuator included in the valve assembly. The present invention seeks to address this problem by providing a direct control valve assembly for a fuel injector that directs fluid around the electrical actuator without increasing the size of the fuel injector. Thus, the present invention includes an electrical actuator having an actuator centerline that is oriented at an angle, which is preferably perpendicular, with respect to a centerline of the fuel injector.

Description:
TECHNICAL FIELD 
     This invention relates generally to valve assemblies, and more particularly to fuel injectors having an electrically actuated valve positioned in a middle portion of the injector body. 
     BACKGROUND 
     Increasingly, fuel injectors are being equipped with direct control needle valves that are controlled in operation by a separate valve assembly to allow for independent control over injection characteristics, such as injection pressure and timing. Engineers have determined that for many applications it is beneficial to position the needle control valve assembly in close proximity to the direct control needle valve member. One example of such a fuel injector is disclosed in U.S. Pat. No. 5,697,342, which issued to Anderson et al. on Dec. 16, 1997. However, when the valve assembly is positioned in this more central portion of the fuel injector, it is problematic finding sufficient room to route fluid passages within the fuel injector around or through the valve assembly electrical actuator. This problem often results in undesirable compromises to accommodate the needed fluid passages around the electrical actuator, while maintaining performance requirements for the valve. 
     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 fuel injector includes an injector body that has a body centerline and provides a middle portion separating an upper portion from a lower portion. The injector body defines a fluid passage extending between the upper portion and the lower portion through the middle portion. An electrical actuator is attached to the injector body and is positioned in the middle portion. The electrical actuator has an actuator centerline. A valve member is positioned in the middle portion and is operably coupled to the electrical actuator. The valve member has a first position in which the fluid passage is open, and a second position in which the fluid passage is at least partially closed. The actuator centerline is oriented at an angle, which is greater than zero, with respect to the body centerline. 
     In another aspect of the present invention a valve assembly for positioning in a casing component includes a body component that has a body centerline and a top face that is separated from a bottom face by an annular side surface. The body component defines a fluid passage that extends from the top face to the bottom face. The top face and the bottom face provide at least one planar contact surface that is substantially perpendicular to the body centerline. An electrical actuator is attached to the body component away from the fluid passage. A valve member having a valve centerline oriented at an angle, greater than zero, with respect to the body centerline, is operably coupled to the electrical actuator, and is at least partially positioned in the body component. The valve member has a first position in which the fluid passage is open, and a second position in which the fluid passage is at least partially closed. 
     In yet another aspect of the present invention, a method of injecting fuel includes routing high pressure fuel to a nozzle chamber through a high pressure passage that is at least partially defined by a valve body component, but away from an electrical actuator that is attached to the valve body component. A needle valve member is moved to an open position, at least in part by relieving fluid pressure on a closing hydraulic surface of the needle valve member. The needle valve member is moved to a closed position, at least in part by resuming fluid pressure on the closing hydraulic surface of the needle valve member. At least one of the moving steps includes a step of energizing the electrical actuator to move a control valve member along a line oriented at an angle, greater than zero, with respect to a centerline of the needle valve member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectioned side diagrammatic view of a fuel injector according to the present invention; 
     FIG. 2 is a sectioned top view of the valve assembly of the fuel injector of FIG. 1 as viewed along section line  2 — 2 ; 
     FIG. 3 is a sectioned side diagrammatic view of a fuel injector according to an alternate embodiment of the present invention; and 
     FIG. 4 is a sectioned top view of the valve assembly of the fuel injector of FIG. 3 as viewed along section line  4 — 4 . 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1 there is illustrated a fuel injector  10  according to the present invention. Fuel injector  10  has been illustrated as a hydraulically actuated electronically controlled fuel injector of the type manufactured by Caterpillar, Inc. of Peoria, Ill. However, it should be appreciated that the present invention could also be utilized in a mechanically actuated fuel injector or a common fuel rail type fuel injector. Fuel injector  10  consists of an injector body  11  made up of various components attached to one another in a manner well known in the art, and a number of movable internal parts positioned in the manner they would be just prior to the start of an injection event. As illustrated, injector body  11  has a middle portion  49  that separates an upper portion  20  from a lower portion  79 . It should be appreciated that the three portions need not be similar in shape or size. Middle portion  49  has a top face  53  and a bottom face  54  that are separated by an annular side surface  51 . A high pressure source  13  supplies fluid to a high pressure passage  14  defined by injector body  11  via a high pressure inlet. Preferably, high pressure source  13  contains an amount of pressurized engine lubricating oil, however, another suitable fluid could be used to actuate fuel injector  10 , such as transmission fluid, fuel or coolant. 
     Fuel injector  10  is controlled in operation by a control valve assembly  15  that is preferably attached to injector body  11 . Control valve assembly  15  includes an electrical actuator  16  that is preferably a solenoid. However, it should be appreciated that electrical actuator  16  could be another suitable device, such as a piezoelectric actuator. Electrical Actuator  16  includes a biasing spring  17 , a coil  18 , and an armature  19 . A pilot valve member  21  is preferably attached to armature  19  via a fastener  22 . Pilot valve member  21  is preferably a poppet valve member, as illustrated, however, another suitable valve member, such as a ball valve member could be substituted. When solenoid  16  is de-energized, armature  19  is held in its biased, advanced position by biasing spring  17 , thus holding valve member  21  in its advanced position. When valve member  21  is in this position, it opens a high pressure seat  23  to allow fluid communication between high pressure passage  14  and a variable pressure passage  29  that is at least partially defined by injector body  11 . When solenoid  16  is energized, armature  19  is moved to a retracted position against the bias of biasing spring  17 , thus pulling valve member  21  toward its retracted position. When valve member  21  is in its retracted position, it closes high pressure seat  23  and opens a low pressure seat  24  thus blocking variable pressure passage  29  from high pressure passage  14  and opening the same to a low pressure drain  25 . 
     A spool valve member  30  is also positioned in injector body  11  and is movable between an upward, retracted position as shown, and a downward, advanced position. Spool valve member  30  is biased toward its retracted position by a biasing spring  35 . Spool valve member  30  defines a high pressure annulus  33  that is always open to high pressure passage  14  and is positioned such that it can open an actuation fluid passage  44  to high pressure passage  14  when spool valve member  30  is in its advanced position. A low pressure annulus  36  is also provided on spool valve member  30  that can connect actuation fluid passage  44  to a low pressure drain  27  via a low pressure passage  34  defined by injector body  11  when spool valve member  30  is in its retracted position as shown. Spool valve member  30  has a control surface  37  that is exposed to fluid pressure in a spool cavity  38  that is in fluid communication with variable pressure passage  29 , and a high pressure surface  31  that is continuously exposed to high pressure in high pressure passage  14  via a number of radial passages that are defined by spool valve member  30 . Preferably, high pressure surface  31  and control surface  37  are about equal in surface area. 
     When variable pressure passage  29  is fluidly connected to high pressure source  13 , such as when pilot valve member  21  is in its retracted position, pressure within spool cavity  38  is high and spool valve member  30  is preferably hydraulically balanced and maintained in its retracted position by biasing spring  35 . When spool valve member  30  is in this position, actuation fluid passage  44  is blocked from fluid communication with high pressure passage  14  but fluidly connected to low pressure passage  34  via low pressure annulus  36 . Conversely, when variable pressure passage  29  is fluidly connected to low pressure reservoir  12 , such as when pilot valve member  21  is in its advanced position, pressure within spool cavity  38  is sufficiently low that the high pressure acting on high pressure surface  31  can overcome the force of biasing spring  35 , and spool valve member  30  can move to its advanced position. When spool valve member  30  is in this advanced position, actuation fluid passage  44  is blocked from low pressure passage  34  but high pressure fluid can flow into actuation fluid passage  44  via high pressure annulus  33  and high pressure passage  14 . 
     An intensifier piston  45  is positioned in injector body  11  and includes a hydraulic surface  46  that is exposed to fluid pressure in actuation fluid passage  44 . Piston  45  is biased toward a retracted, upward position by a biasing spring  47 . However, when pressure within actuation fluid passage  44  is sufficiently high, such as when it is open to high pressure passage  14  via high pressure annulus  33 , piston  45  can move to an advanced, downward position against the action of biasing spring  47 . A plunger  48  is also movably positioned in injector body  11  and moves in a corresponding manner with piston  45 . When piston  45  is moved toward its advanced position, plunger  48  also advances and acts to pressurize fuel within a fuel pressurization chamber  50  that is connected to a fuel inlet past a check valve (not shown). During an injection event as plunger  48  moves toward its downward position, the check valve is closed and plunger  48  can act to compress fuel within fuel pressurization chamber  50 . When plunger  48  is returning to its upward position, fuel is drawn into fuel pressurization chamber  50  past the check valve. Fuel pressurization chamber  50  is fluidly connected to a fuel supply passage  52  that is defined at least in part by upper portion  20  and/or middle portion  49  of injector body  11 . As illustrated, fuel supply passage  52  passes through both a top face  53  and a bottom face  54  of middle portion  49 . Pressurized fuel contained within fuel supply passage  52  is supplied to both a nozzle supply passage  80  and a needle control passage  82 . Fuel supply passage  52  is fluidly connected to needle control passage  82  via a upper portion  58  and lower portion  59 . 
     Returning to fuel injector  10 , a pressure relief valve  40  is movably positioned in injector body  11  to vent pressure spikes from actuation fluid passage  44 . Pressure spikes can be created when piston  45  and plunger  48  abruptly stop their downward movement due to the abrupt closure of nozzle outlets  95 . 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  42  extends between actuation fluid passage  44  and a low pressure vent  28 . When spool valve member  30  is in its downward position, such as during an injection event, a pin  39  holds pressure relief ball valve member  40  downward to close a seat  41 . When pressure relief valve  40  is in this position, actuation fluid passage  44  is closed to pressure relief passage  42  and pressure can build within actuation fluid passage  44 . However, immediately after injection events, when piston  45  and plunger  48  are hydraulically slowed and stopped, residual high pressure in actuation fluid passage  44  can act against pressure relief valve  40 . Because pressure within spool cavity  38  is high, spool valve member  30  is hydraulically balanced and can move toward its upward position under the action of biasing spring  35 . Pressure relief valve  40  can then lift off of seat  41  to open actuation fluid passage  44  to pressure relief passage  42 , thus allowing pressure within actuation fluid passage  44  to be vented. At the same time, upward movement of pressure relief valve  40 , and therefore pin  39  can aid in the movement of spool valve member  30  toward its upward position. 
     Referring in addition to FIG. 2, fuel injector  10  also includes a valve assembly  60  that provides an electrical actuator  61  and a valve member  70 . Valve member  70  is preferably at least partially positioned in a casing component  68  provided by fuel injector  10 . Preferably, electrical actuator  61  is an E-frame solenoid  62  that provides an E-frame stator  69 . However, it should be appreciated that other electrical actuators, such as a piezoelectric actuator, a voice coil, or another suitable device, could instead be substituted. Solenoid  62  is positioned in injector body  11  such that an actuator centerline  67  is oriented at an angle, greater than zero, with respect to injector body centerline  96 . Preferably, solenoid  62  is positioned such that actuator centerline  67  is about perpendicular to injector body centerline  96 , as best illustrated in FIG.  1 . When solenoid  62  is oriented as such, fluid passage  52  can be spacially separated from the various components of solenoid  62 . Solenoid  62  includes a coil  64  and an armature  65 . Armature  65  is limited in its movement by a spacer  66  and is coupled to move with valve member  70 . Armature  65  can be attached to valve member  70  as illustrated, or these components could be unattached but coupled to move together, such as by a biasing spring. As with solenoid  62 , valve member  70  is positioned such that a valve centerline  71  is oriented at an angle, greater than zero, with respect to injector body centerline  96 . Preferably, valve member  70  is positioned such that valve centerline  71  and injector body centerline  96  are perpendicular, as best illustrated in FIG.  1 . 
     When solenoid  62  is de-energized, such as between injection events, armature  65  is maintained in its biased, advanced position by a biasing spring  63  that is provided by valve assembly  60 , thus holding valve member  70  in its advanced position, as illustrated in FIG.  2 . When valve member  70  is in this position, a conical valve surface  72  included on valve member  70  is away from a conical high pressure seat  73  defined by injector body  11 , such that an upper portion  58  is fluidly connected to a lower portion  59 . High pressure fuel can therefore flow from fuel pressurization chamber  50  into needle control passage  82  around valve member  70 . When solenoid  62  is energized, such as just prior to an injection event, armature  65  is moved to a retracted position against the bias of biasing spring  63 , thus pulling valve member  70  toward its retracted position. When valve member  70  is in this position, valve surface  72  closes high pressure seat  73 , and upper portion  58  is blocked from lower portion  59 , thus ending the flow of high pressure fuel from fuel pressurization chamber  50  to needle control passage  82 . A low pressure seat  75 , defined by a sleeve  76 , is opened by the retracting movement of valve member  70  to open lower portion  59  to a low pressure space  78  via a low pressure passage  77  that connects to annular side surface  51 . 
     Returning to fuel injector  10 , a direct control needle valve member  90  (FIG. 1) is movably positioned in injector body  11  and includes an opening hydraulic surface  92  exposed to fluid pressure in a nozzle chamber  93  and a closing hydraulic surface  86  exposed to fluid pressure in needle control chamber  84 . Nozzle chamber  93  is in fluid communication with nozzle supply passage  80 , while needle control chamber  84  is in fluid communication with needle control passage  82 . Needle valve member  90  is movable between an upward, open position and a downward, closed position and is biased toward its downward position by a biasing spring  85 . When valve member  70  is in its advanced position, such as while fuel in fuel pressurization chamber  50  is being pressurized, high pressure fuel can act on closing hydraulic surface  86  such that needle valve member  90  is maintained in its downward, closed position. When valve member  70  is moved to its retracted position, needle control passage  82 , and therefore needle control chamber  84 , is blocked from high pressure and connected to a low pressure area inside casing  68 . With high pressure no longer acting on closing hydraulic surface  86 , needle valve member  90  can be lifted to its upward, open position by the force of pressurized fuel acting on opening hydraulic surface  92 . 
     Closing hydraulic surface  86  and opening hydraulic surface  92  are preferably sized such that even when a valve opening pressure is attained in nozzle chamber  93 , needle valve member  90  will not lift open when needle control chamber  84  is fluidly connected to fuel supply passage  52  via nozzle control passage  82 . However, it should be appreciated that the relative sizes of closing hydraulic surface  86  and opening hydraulic surface  92  and the strength of biasing spring  85  should be such that when closing hydraulic surface  86  is no longer exposed to fluid pressure in fuel supply passage  52 , a valve opening pressure acting on opening hydraulic surface  92  should be sufficient to move needle valve member  90  upward against the force of biasing spring  85  to open nozzle outlet  95 . It should be further appreciated that the strength of biasing spring  85  should be such that needle valve member  90  will remain in its closed position when fuel pressure in nozzle chamber  93  is below a valve opening pressure, even when needle control chamber  84  is blocked from fuel supply passage  52 . 
     Referring now to FIG. 3, there is illustrated a fuel injector  110  according to an alternate embodiment of the present invention. While fuel injector  10 , illustrated in FIG. 1, included a means for pressurizing fuel to injection levels, fuel injector  110  is an electronically controlled nozzle, such as would be used with a common rail fuel injection system. Fuel injector  110  provides an injector body  111  that has an upper portion  120  and a lower portion  179  that are separated by a middle portion  149 . As illustrated, middle portion  149  has a top face  153  and a bottom face  154  that are separated by an annular side surface  151 . In addition, injector body  111  defines a fuel supply passage  152  that is fluidly connected to a source of pressurized fuel  113  via a fuel supply line  114 . Thus, when fuel injector  110  is attached to a common rail, fuel supply passage  152  is continuously supplied with fuel that is pressurized to injection levels. Fuel injector  110  also includes a valve assembly  160  that is similar to valve assembly  60 , previously disclosed. However, whereas valve assembly  60  can be referred to as a normally open valve assembly, or one in which valve member  70  is maintained in its advanced, or open, position between injection events, and is closed only when fuel injection is desired, valve assembly  160  could be referred to as a normally closed valve assembly. In other words, valve member  170  is maintained in a closed position until fuel injection is desired, and then moved to an open position at that time. 
     Referring now in addition to FIG. 4, valve assembly  160  provides an electrical actuator  161 , which is preferably an E-frame solenoid  162  that has an E-frame stator  169 . However, as with the previous embodiment, it should be appreciated that electrical actuator  161  could be any suitable device, such as a piezoelectric actuator or a voice coil. As with the previous embodiment, solenoid  162  is positioned within injector body  111  such that an actuator centerline  167  is oriented at an angle, greater than zero, with respect to an injector body centerline  196 . Preferably, solenoid  162  is positioned such that actuator centerline  167  is perpendicular to injector body centerline  196 . When solenoid  162  is oriented as such, fluid passage  152  can be spacially separated from the various components of solenoid  162 . Solenoid  162  provides a coil  164  and an armature  165 . Armature  165  is coupled to move with a valve member  170  that is at least partially positioned within a casing component  168 . Armature  165  can be attached to valve member  170  as illustrated, or these components could be unattached but coupled to move together, such as by a biasing spring. As with solenoid  162 , valve member  170  is positioned such that a valve centerline  171  is oriented at an angle, greater than zero, with respect to injector body centerline  196 . Preferably, valve member  170  is positioned such that valve centerline  171  and injector body centerline  196  are perpendicular, as best illustrated in FIG.  3 . 
     When solenoid  162  is de-energized, such as between injection events, armature  165  is maintained in its biased, advanced position by a biasing spring  163  provided by valve assembly  160 , thus holding valve member  170  in an advanced, closed position. When valve member  170  is in this position, a conical valve surface  172  provided on valve member  170  is in contact with a conical valve seat  173  defined by injector body  111 , such that an upper portion  158  is blocked from a low pressure passage  156 . Pressurized fuel from fuel source  113  can flow through a flow restriction  157  into a needle control chamber  184  via a needle control passage  182 . When solenoid  162  is energized, such as just prior to an injection event, armature  165  is moved to a retracted position against the bias of biasing spring  163 , thus pulling valve member  170  toward a retracted, open position. When valve member  170  is in this position, valve surface  172  is moved away from valve seat  173 , and lower portion  159  is fluidly connected to low pressure passage  156  via an armature cavity  166 . Therefore, lower portion  159  and upper portion  158 , via flow restriction  157 , are opened to low pressure. Sizing flow restrictions on each side of valve member  170  can have a significant influence on performance. 
     Returning to fuel injector  110 , a direct control needle valve member  190  (FIG. 3) is movably positioned in injector body  111  and includes an opening hydraulic surface  192  exposed to fluid pressure in a nozzle chamber  193  and a closing hydraulic surface  186  exposed to fluid pressure in needle control chamber  184 . Nozzle chamber  193  is in fluid communication with nozzle supply passage  180 , while needle control chamber  184  is in fluid communication with needle control passage  182 . Needle valve member  190  is movable between an upward, open position and a downward, closed position and is biased toward its downward position by a biasing spring  185 . When valve member  170  is in its advanced position, such as between injection events, high pressure fuel can act on closing hydraulic surface  186  such that needle valve member  190  is maintained in its downward, closed position. When valve member  170  is moved to its retracted position, such as just prior to the start of an injection event, needle control passage  182 , and therefore needle control chamber  184 , is opened to low pressure via armature cavity  166  and low pressure passage  156 . With high pressure no longer acting on closing hydraulic surface  186 , needle valve member  190  can be lifted to its upward, open position by the force of pressurized fuel acting on opening hydraulic surface  192 . 
     It should be appreciated that the various passages and surfaces within injector  110  should be sized to allow fuel injector  110  to perform as desired. For instance, because upper portion  158  is opened to a low pressure area when valve member  170  is moved to its retracted, open position, flow restriction  157  should be small enough to prevent the depressurization of fuel in fuel supply passage  152  when valve member  170  opens valve seat  173 . However, flow restriction  157  should be sized large enough that a sufficient amount of high pressure can be exerted on closing hydraulic surface  186  in needle control chamber  184  to maintain needle valve member  190  in its downward, closed position when valve member  170  is in its closed position. In addition, closing hydraulic surface  186  and opening hydraulic surface  192  are preferably sized such that needle valve member  190  will not lift open when needle control chamber  184  is fluidly connected to fuel supply passage  152  via nozzle control passage  182 . However, it should be appreciated that the relative sizes of closing hydraulic surface  186  and opening hydraulic surface  192  and the strength of biasing spring  185  should be such that when closing hydraulic surface  186  is no longer exposed to fluid pressure in fuel supply passage  152 , a valve opening pressure acting on opening hydraulic surface  192  should be sufficient to move needle valve member  190  upward against the force of biasing spring  185  to open nozzle outlet  195 . 
     Industrial Applicability 
     Referring now to FIGS. 1 and 2, prior to an injection event, low pressure prevails in fuel injector  10 , pilot valve member  21  is in its advanced position opening variable pressure passage  29  to high pressure passage  14  and spool valve member  30  is hydraulically balanced and positioned in its biased, retracted position fluidly connecting actuation fluid passage  44  to low pressure passage  34  such that low pressure is acting on hydraulic surface  46  of piston  45 . Valve member  70  is in its biased advanced position opening needle control passage  82  to fuel supply passage  52  and needle valve member  90  is in its downward position closing nozzle outlet  95 . Just prior to the desired start of the injection event, solenoid  16  is activated and valve member  21  is pulled to its retracted position by armature  19 . Variable pressure passage  29  is now blocked from high pressure passage  14  and opened to low pressure drain  25 . 
     With control surface  37  now exposed to low pressure in spool cavity  38  via variable pressure passage  29 , spool valve member  30  is no longer hydraulically balanced. The high pressure acting on high pressure surface  31  is now sufficient to move spool valve member  30  to its advanced position. Actuation fluid passage  44  is thus blocked from fluid communication with low pressure passage  34  and opened to high pressure passage  14  via high pressure annulus  33 . High pressure actuation fluid flowing into actuation fluid passage  44 , acts on hydraulic surface  46  of piston  45 , causing piston  45  and plunger  48  to begin to move toward their advanced positions to pressurize fuel in fuel pressurization chamber  50  and fuel supply passage  52 . However, because closing hydraulic surface  85  is also exposed to high pressure in needle control chamber  84  via fuel supply passage  52  and needle control passage  82 , needle valve member  90  will not be moved to its upward position to open nozzle outlet  95 . Further, it should be appreciated that piston  45  and plunger  48  move only a slight distance at this time because of hydraulic locking, which is a result of nozzle outlet  95  remaining closed. However, the slight movement of piston  45  and plunger  48  is still sufficient to raise fuel pressure within fuel pressurization chamber  50  to injection pressure levels. 
     When injection is desired, solenoid  62  is activated and valve member  70  is pulled to its retracted position by armature  65 . High pressure seat  73  is now closed by valve surface  72 , thus ending fluid communication between needle control passage  82  and fuel supply passage  52 . Needle control passage  82  is now opened to low pressure space  78  via low pressure passage  77  and fluid pressure acting on closing hydraulic surface  86  is relieved. With low pressure now acting on closing hydraulic surface  85  in needle control chamber  84  via needle control passage  82 , needle valve member  90  can be lifted to its upward, open position by the force of pressurized fuel acting on opening hydraulic surface  192 . Fuel in nozzle chamber  93  can now spray into the combustion space via nozzle outlet  95 . 
     When the desired amount of fuel has been injected into the combustion space, solenoid  62  is de-energized. Valve member  70  is then returned to its biased, advanced position by biasing spring  63 . As valve member  70  advances, high pressure seat  73  is reopened and needle control passage  82  is once again fluidly connected to fuel supply passage  52  to resume fluid pressure on closing hydraulic surface  86 . With high pressure again acting on closing hydraulic surface  85 , needle valve member  90  is returned to its downward, closed position blocking nozzle outlet  95  and ending the injection event. As a result of hydraulic locking, piston  45  and plunger  48  stop their advancing movement but do not immediately begin to retract because hydraulic surface  46  is still exposed to high pressure fluid in actuation fluid passage  44 . It should be appreciated that if a split injection is desired, solenoid  62  would be re-energized and valve member  70  would be returned to its retracted position fluidly connecting needle control passage  82  to low pressure passage  77 . With closing hydraulic surface  85  once again exposed to low pressure, and with high pressure still acting on opening hydraulic surface  92 , needle valve member  90  would once again be moved to its open position. 
     Once the injection event has ended, the various components of fuel injector  10  reset themselves in preparation for the following injection event. Solenoid  16  is de-energized and valve member  21  is returned to its downward position under the force of biasing spring  17  to open high pressure seat  23 . Variable pressure passage  29  is now open to high pressure passage  14 , thus exposing control surface  37  is exposed to high pressure within spool cavity  38 . With nozzle outlet  95  closed, residual high pressure in actuation fluid passage  44  is sufficient to move pressure relief valve  40  upward away from seat  41  to fluidly connect actuation fluid passage  44  to pressure relief passage  42 . Pressure relief valve  40  can therefore help vent high pressure actuation fluid from actuation fluid passage  44  to prevent pressure spikes from causing undesired secondary injections. At the same time, the upward movement of pressure relief valve  40  causes pin  39  to aid spool valve member  30  in returning to its upward position. Recall that control surface  37  is again exposed to high pressure in spool cavity  38 , causing spool valve member  30  to once again be hydraulically balanced such that it can return to its upward position under the force of biasing spring  35 , in addition to the upward force of pin  39 . When spool valve member  30  begins to retract, piston  45  and plunger  48  end their downward movement, however, as a result of hydraulic locking they do not immediately begin to retract. Once spool valve member  30  is returned to its upward position, actuation fluid passage  44  is blocked from fluid communication with high pressure passage  14  and fluidly connected to low pressure passage  34 , which further reduces the pressure within actuation fluid passage  44 . Piston  45  and plunger  48  can now move toward their retracted positions. As plunger  48  retracts, fuel can be drawn into fuel pressurization chamber  50  past the check valve  87 . 
     Referring now to the FIGS. 3 and 4 embodiment of the present invention, prior to an injection event, fuel supply passage  152  is fluidly connected to pressurized fuel source  113 , valve member  170  is in its advanced position blocking fuel supply passage  152  from low pressure space  178  and needle valve member  190  is in its downward position blocking nozzle outlet  195 . Just prior to the desired start of injection, solenoid  162  is energized and valve member  170  is pulled to its retracted position by armature  165 . Fuel supply passage  152  is now fluidly connected to low pressure space  178  via armature cavity  166  and low pressure passage  156 . With low pressure now acting on closing hydraulic surface  186  in needle control chamber  184 , needle valve member  190  is lifted to its upward position by the force of pressurized fuel acting on opening hydraulic surface  192 . Fuel spray into the combustion space via nozzle outlet  195  can now commence. 
     When the desired amount of fuel has been injected into the combustion space, solenoid  162  is de-energized and valve member  170  is returned to its advanced position by biasing spring  163 . When valve member  170  is moved to its advanced position, valve surface  172  closes valve seat  173 , thus blocking fuel supply passage  152  from low pressure space  178 . High pressure once again acts on closing hydraulic surface  185  in needle control chamber  184  and needle valve member  190  is moved to its downward position blocking nozzle outlet  195  and ending the injection event. 
     It should be appreciated that a number of modifications could be made to the embodiments of the present invention that have been illustrated herein. For instance, while fuel injector  10  has been illustrated as a hydraulically actuated fuel injector, the present invention could also be utilized with a mechanically actuated fuel injector. For such an injector, plunger  48  would be driven downward to pressurize fuel within fuel pressurization chamber  50  by a rocker arm and tappet assembly. In addition, while the valve member and the electrical actuator have been illustrated as being oriented in the injector body such that the valve centerline and the electrical actuator centerline are perpendicular to the injector body centerline, this is not necessary. Instead the valve member and/or the electrical actuator could be positioned such that the valve centerline and/or the electrical actuator centerline are oriented at any angle greater than zero with respect to the injector body centerline. Further, it should be appreciated that the present invention could find application in any fuel injector having a fuel or fluid passage that must pass through the electrical actuator. Use of the present invention can allow the desired fluid passage to pass around the electrical actuator, rather than through it, while still providing for a compact injector body. 
     Although this invention is illustrated in the context of a hydraulically actuated unit injector as shown in commonly-owned U.S. Pat. No. 5,738,075, for example, one skilled in the art will recognize that this invention is equally applicable to other fuel systems such as the amplifier piston common rail system (APCRS) illustrated in the paper “Heavy Duty Diesel Engines—The Potential of Injection Rate Shaping for Optimizing Emissions and Fuel Consumption”, presented by Messrs. Bernd Mahr, Manfred Durnholz, Wilhelm Polach, and Hermann Grieshaber; Robert Bosch GmbH, Stuttgart, Germany, at the 21 st  International Engine Symposium, May 4-5, 2000, Vienna, Austria. In this regard, while the present invention has been illustrated for use in fuel injectors having a high pressure passage extending through the injector body, it should be appreciated that the valve assembly could instead control fluid communication between the needle control chamber and a low pressure passage or a low pressure drain. 
     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. 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.