Abstract:
Engineers have determined that the ability to front end rate shape injection events can result in a number of advantages, including improved injector performance and a reduction in undesirable emissions. In addition, engineers have learned that it is desirable for the needle valve to open slowly at the beginning of an injection event and to close abruptly to end the injection event. Therefore, the present invention utilizes at least one orifice member that is movably positioned in an injector body such that fluid flowing away from the needle valve member closing hydraulic surface flows through a relatively restricted flow path and fluid flowing toward the needle valve member flow through a relatively unrestricted flow path.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates generally to fuel injectors, and more particularly to fuel injectors having a direct control needle valve.  
       BACKGROUND  
       [0002]     An increasing number of fuel injectors are being machined to include a direct control needle valve. In operation, a direct control needle valve is moved between an open position and a closed position by fluid displacement. For instance, the direct control needle valve to move from its closed position toward its open position, a small amount of fluid must be displaced by the needle valve. Similarly, for the needle valve to move from its open position to its closed position, a small amount of fluid must be displaced toward the needle valve. Use of direct control needle valves is desirable because they can allow for greater control over fuel injection events. Engineers have learned that the ability to better control fuel injection events can include a number of advantages, such as improved injector performance and a reduction in undesirable emissions.  
         [0003]     In this regard, it has been learned that a fast needle valve closing is desirable to produce an abrupt end to the injection event. Conversely, it has been determined that a slow needle valve opening can increase needle valve control at the beginning of an injection event. Several attempts have been made to increase control over fuel injection events. One such attempt is disclosed in U.S. Pat. No. 6,024,296, which issued to Wear et al. on Feb. 15, 2000. Wear et al. discloses a fuel injector having a needle control passage that includes a dual flow rate orifice. While Wear et al. shows promise, there is still room for improvement.  
         [0004]     The present invention is directed to overcoming one or more of the problems as set forth above.  
       SUMMARY OF THE INVENTION  
       [0005]     In one aspect of the present invention, a fuel injector includes an injector body that defines a nozzle outlet and a needle control passage. A needle valve member is positioned in the injector body and includes a closing hydraulic surface that is exposed to fluid pressure in the needle control passage. The needle valve member is movable between an open position in which the nozzle outlet is open and a closed position in which the nozzle outlet is blocked. An orifice member is positioned in the injector body and defines a flow passage with relatively restricted flow area and is movable between a first position and a second position. The needle valve member displaces fluid through the flow passage when moving toward its open position. The needle control passage has a relatively unrestricted flow area to fluid flowing toward the closing hydraulic surface over at least a portion of movement of the needle valve member between the open position and the closed position.  
         [0006]     In another aspect of the present invention, a method of injecting fuel includes a step of opening a nozzle outlet slowly at least in part by displacing fluid, which is caused by movement of a needle valve member, through a restricted flow passage defined by an orifice member. The nozzle outlet is quickly closed at least in part by displacing fluid toward a closing hydraulic surface of the needle valve member through an unrestricted flow passage defined at least in part by the orifice member. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a sectioned side diagrammatic view of a fuel injector according to the present invention;  
         [0008]      FIG. 2  is a sectioned side diagrammatic view of the orifice member of the fuel injector of  FIG. 1 ;  
         [0009]      FIG. 3  is a sectioned side diagrammatic view of an orifice member for use with the fuel injector of  FIG. 1  according to another embodiment of the present invention;  
         [0010]      FIG. 4  is a sectioned side diagrammatic view of an orifice member for use with the fuel injector of  FIG. 1  according to yet another embodiment of the present invention;  
         [0011]      FIG. 5  is a sectioned side diagrammatic view of an orifice member for use with the fuel injector of  FIG. 1  according to still another embodiment of the present invention;  
         [0012]      FIG. 6  is a sectioned side diagrammatic view of an orifice member for use with the fuel injector of  FIG. 1  according to yet another embodiment of the present invention;  
         [0013]      FIG. 7  is a sectioned side diagrammatic view of an orifice member for use with the fuel injector of  FIG. 1  according to still another embodiment of the present invention;  
         [0014]      FIG. 8  is a sectioned side diagrammatic view of an orifice member for use with the fuel injector of  FIG. 1  according to yet another embodiment of the present invention;  
         [0015]      FIG. 9  is a sectioned side diagrammatic view of an orifice member for use with the fuel injector of  FIG. 1  according to still another embodiment of the present invention;  
         [0016]      FIG. 10  is a sectioned side diagrammatic view of an orifice member for use with the fuel injector of  FIG. 1  according to yet another embodiment of the present invention;  
         [0017]      FIG. 11  is a sectioned side diagrammatic view of an orifice member for use with the fuel injector of  FIG. 1  according to still another embodiment of the present invention;  
         [0018]      FIG. 12  is a sectioned side diagrammatic view of an orifice member for use with the fuel injector of  FIG. 1  according to yet another embodiment of the present invention;  
         [0019]      FIG. 13  is a sectioned side diagrammatic view of an orifice member for use with the fuel injector of  FIG. 1  according to another embodiment of the present invention; and  
         [0020]      FIG. 14  is a sectioned side diagrammatic view of an orifice member for use with the fuel injector of  FIG. 1  according to still another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0021]     Referring now to  FIG. 1  there is illustrated a fuel injector  10  according to the present invention. While fuel injector  10  has been illustrated as a hydraulically actuated, electronically controlled fuel injector, it should be appreciated that other suitable fuel injectors could be substituted. For instance, the present invention could be utilized in a mechanically actuated fuel injector or in a unit injector in a common rail fuel injection system. Fuel injector  10  includes an injector body  11  that defines a number of fluid passages and contains the various components of fuel injector  10  positioned as they would be between injection events. Fuel injector  10  includes a first electrical actuator  20  that can control pressurization of fuel for injection events and a second electrical actuator  30  that can control timing of injection events. Preferably, first electrical actuator  20  and second electrical actuator  30  are both solenoids. However, it should be appreciated that one or more suitable alternative actuators could instead be utilized. For instance, one or both of these actuators could be replaced by a piezoelectric actuator.  
         [0022]     Electrical actuator  20  includes a coil  21 , a biasing spring  22  and an armature  23 . A valve member  25 , such as the poppet valve illustrated in  FIG. 1 , is preferably operably connected to armature  23  via a fastener  24  When electrical actuator  20  is de-energized, such as between injection events, valve member  25  is held in, or moved toward, a downward, advanced position, by biasing spring  22 . When valve member  25  is in this position, a high pressure seat  27  is opened and a low pressure seat  28  is blocked, such that a variable pressure passage  29  is fluidly connected to a high pressure passage  56  and blocked from fluid communication with a low pressure passage  26 . When electrical actuator  20  is energized, valve member  25  is moved upward against the force of biasing spring  22  to close high pressure seat  27  and open low pressure seat  28 . In this position, valve member  25  blocks variable pressure passage  29  from high pressure passage  56  and opens the same to low pressure passage  26 .  
         [0023]     Electrical actuator  30 , which is preferably similar in structure to electrical actuator  20 , also includes a coil  31 , a biasing spring  32  and an armature  33 . A valve member  35  is preferably operably connected to armature  33  via a fastener  34 . When electrical actuator  30  is de-energized, such as between injection events, valve member  35  is held in, or moved toward, an advanced position by biasing spring  32 . In this position, valve member  35  opens a high pressure seat  37  and closes a low pressure seat  38 , such that a needle control passage  39  is open to a high pressure passage  57  and blocked from a low pressure passage  36 . When electrical actuator  30  is energized, valve member  35  is pulled toward a retraced position by armature  33  against the force of biasing spring  32 . In this position, valve member  35  closes high pressure seat  27  and opens low pressure seat  28 , such that needle control passage  39  is blocked from high pressure passage  57  and open to low pressure passage  36 .  
         [0024]     Also positioned in injector body  11  is a spool valve member  40 . Spool valve member  40  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  44 . Spool valve member  40  defines a high pressure annulus  42  that is always open to high pressure passage  56  and is positioned such that it can open an actuation fluid passage  48  to high pressure passage  56  when spool valve member  40  is in its advanced position. A low pressure annulus  43  is also included on spool valve member  40  that can connect actuation fluid passage  48  to a low pressure passage  45  defined by injector body  11  when spool valve member  40  is in its retracted position as shown. Spool valve member  40  has a control surface  46  that is exposed to fluid pressure in a spool cavity  47 , and a biasing surface  41  that is continuously exposed to high pressure in high pressure passage  56  via a number of radial passages defined by spool valve member  40 . While surfaces  41  and  46  preferably are about equal in surface area, they could alternatively be of differing surface area. Spool cavity  47  is fluidly connected to variable pressure passage  29 .  
         [0025]     When variable pressure passage  29  is open to high pressure passage  56 , such as when valve member  25  is in its second position, pressure within spool cavity  47  is high and spool valve member  40  is preferably hydraulically balanced and maintained in its retracted position by biasing spring  44 . When spool valve member  40  is in this position, actuation fluid passage  48  is blocked from fluid communication with high pressure passage  56  but fluidly connected to low pressure passage  45  via low pressure annulus  43 . Conversely, when variable pressure passage  29  is fluidly connected to low pressure passage  45 , such as when valve member  25  is in its first position, pressure within spool cavity  47  is sufficiently low that the high pressure acting on biasing surface  41  can overcome the force of biasing spring  44 , and spool valve member  40  can move to its advanced position. When spool valve member  40  is in this advanced position, actuation fluid passage  48  is blocked from low pressure passage  45  but high pressure fluid can flow into actuation fluid passage  48  via high pressure annulus  42  and high pressure passage  56 .  
         [0026]     An intensifier piston  60  is positioned in injector body  11  and includes a hydraulic surface  61  that is exposed to fluid pressure in actuation fluid passage  48 . Piston  60  is biased toward a retracted, upward position by a biasing spring  64 . However, when pressure within actuation fluid passage  48  is sufficiently high, such as when it is open to high pressure passage  56  via high pressure annulus  42 , piston  60  can move to an advanced, downward position against the action of biasing spring  64 . A plunger  63  is also movably positioned in injector body  11  and moves in a corresponding manner with piston  60 . When piston  60  is moved toward its advanced position, plunger  63  also advances and acts to pressurize fuel within a fuel pressurization chamber  67  that is connected to a fuel inlet past a check valve  62 . During an injection event as plunger  63  moves toward its downward position, the check valve  62  is closed and plunger  63  can act to compress fuel within fuel pressurization chamber  67 . When plunger  63  is returning to its upward position, fuel is drawn into fuel pressurization chamber  67  past the check valve  62 . Fuel pressurization chamber  67  is fluidly connected to a fuel supply passage  68  that is defined by injector body  11 . Pressurized fuel contained within fuel supply passage  68  is supplied to a nozzle supply passage  94 .  
         [0027]     Returning to fuel injector  10 , a pressure relief valve  50  is movably positioned in injector body  11  to vent pressure spikes from actuation fluid passage  48 . Pressure spikes can be created when piston  60  and plunger  63  abruptly stop their downward movement due to the abrupt closure of nozzle outlets  96 . 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  51  extends between actuation fluid passage  48  and a low pressure vent. When spool valve member  40  is in its downward position, such as during an injection event, a pin  53  holds pressure relief ball valve member  50  downward to close a seat  54 . When pressure relief valve  50  is in this position, actuation fluid passage  48  is closed to pressure relief passage  51  and pressure can build within actuation fluid passage  48 . However, immediately after injection events, when piston  60  and plunger  63  are hydraulically slowed and stopped, residual high pressure in actuation fluid passage  48  can act against pressure relief valve  50 . Because pressure within spool cavity  47  is high, spool valve member  40  is hydraulically balanced and can move toward its upward position under the action of biasing spring  44 . Pressure relief valve  50  can then lift off of seat  54  to open actuation fluid passage  48  to pressure relief passage  51 , thus allowing pressure within actuation fluid passage  48  to be vented. At the same time, upward movement of pressure relief valve  50 , and therefore pin  53  can aid in the movement of spool valve member  40  toward its upward position.  
         [0028]     Referring in addition to  FIG. 2 , an orifice member  70  is movably positioned in injector body  11 . Orifice member  70  is preferably a variable area valve member that is positioned in needle control passage  39  and defines a portion of the same. Orifice member  70  includes a hydraulic surface  74  that is exposed to fluid pressure in an upstream portion  69  of needle control passage  39 . Orifice member  70  is movable within a spring chamber  76 , which is also a portion of needle control passage  39 , between an upward, first position in which it closes a valve seat  73  defined by injector body  11  and a downward, second position in which valve seat  73  is opened. It should be appreciated that while valve seat  73  has been illustrated as a conical valve seat, it could also be a flat valve seat. Orifice member  70  is biased toward its first position by a biasing spring  77  that is operably positioned in injector body  11 . A flow restriction orifice  71  and flow passage  72  are defined by orifice member  70 . In addition, orifice member  70  defines a fluid passage  79  that fluidly connects flow passage  72  to spring chamber  76 , which is a portion of needle control passage  39 .  
         [0029]     When needle control passage  39  is open to low pressure passage  36 , such as during an injection event, orifice member  70  remains in its upward, biased position under the force of biasing spring  77  and the fluid pressure within spring chamber  76 . However, it should be appreciated that while the fluid within spring chamber  76  is being displaced via fluid passage  79  and flow passage  72 , orifice member  70  will remain in its biased position because the force of biasing spring  77  is sufficient to overcome the low pressure acting on hydraulic surface  74 . When orifice member  70  is in its first position, upstream portion  69  of needle control passage  39  is fluidly connected to a downstream portion  78  of needle control passage  39  via flow passage  72 , which has a relatively restricted flow area. When needle control passage  39  is opened to high pressure passage  57 , orifice member  70  will be abruptly moved to its second position against the force of biasing spring  77  due to the increased hydraulic force acting on hydraulic surface  74 . When orifice member  70  is in its second position, upstream portion  69  is fluidly connected to downstream portion  78  via both flow passage  72  and a relatively unrestricted flow passage  75 , a portion of which is an annular flow area between orifice member  70  and injector body  11 . Thus, when orifice member  70  is in its second position, needle control passage  39  has a relatively unrestricted flow area, which includes flow passage  72  and unrestricted flow passage  75 . However, as high pressure fluid flows into spring chamber  76  via fluid passage  79 , the pressure within spring chamber  76  will increase, causing orifice member  70  to be returned to its first position.  
         [0030]     Returning to  FIG. 1 , a direct control needle valve  90  is movably positioned in injector body  11 . Direct control needle valve  90  preferably includes a piston portion  86  and a needle valve member  91 . Piston portion  86  includes a closing hydraulic surface  85  that is exposed to fluid pressure in a needle control chamber  80 , while needle valve member  91  includes an opening hydraulic surface  93  that is exposed to fluid pressure in nozzle supply passage  94 . Needle valve member  91  is movable between a biased, closed position and an open position. When valve member  35  is in its advanced position, such as when electrical actuator  30  is de-energized, high pressure fuel can act on closing hydraulic surface  85  via both flow passage  72  and unrestricted flow passage  75 . Thus, needle valve member  91  is maintained in its downward, closed position. When valve member  35  is moved to its retracted position, needle control passage  39 , and therefore needle control chamber  80 , becomes blocked from high pressure passage  57  and connected to low pressure passage  36 . With high pressure no longer acting on closing hydraulic surface  85 , needle valve member  91  can be lifted to its upward, open position by the force of pressurized fuel acting on opening hydraulic surface  93 . It should be appreciated that when orifice member  70  is in its second position, needle control passage  39  will have a relatively unrestricted flow area to fluid flowing toward closing hydraulic surface  85  over at least a portion of the movement of needle valve member  91  between its open and closed positions.  
         [0031]     Closing hydraulic surface  85  and opening hydraulic surface  93  are preferably sized such that even when a valve opening pressure is attained in nozzle supply passage  94 , needle valve member  91  will not lift open when needle control chamber  80  is fluidly connected to high pressure passage  57  via needle control passage  39 . However, it should be appreciated that the relative sizes of closing hydraulic surface  85  and opening hydraulic surface  93  and the strength of biasing spring  82  should be such that when closing hydraulic surface  85  is no longer exposed to high pressure in needle control chamber  80 , a valve opening pressure acting on opening hydraulic surface  93  should be sufficient to move needle valve member  91  upward against the force of biasing spring  82  to open nozzle outlet  96 . It should be further appreciated that the strength of biasing spring  82  should be such that needle valve member  91  will remain in its closed position when fuel pressure in nozzle supply passage  94  is below a valve opening pressure, even when needle control chamber  80  is fluidly connected to low pressure passage  36  via needle control passage  39 .  
         [0032]     In addition to these considerations, it should be appreciated that flow restriction orifice  71  should be large enough that needle valve member  91  can displace a sufficient amount of fluid via flow passage  72  to move toward its open position when orifice member  70  is in its first position. However, flow restriction orifice  71  should still be sufficiently small that flow passage  72  is a relatively restricted flow passage. Thus, when orifice member  70  is in its first position and needle control passage  39  is opened to low pressure passage  36 , high pressure actuation fluid in needle control chamber  80  and needle control passage downstream portion  78  will be displaced relatively slowly through flow passage  72  and flow restriction orifice  71 . Therefore, because fluid is being displaced at a reduced rate within needle control chamber  80 , needle valve member  91  will be lifted toward its open position slowly. In other words, once the valve opening pressure is reached in nozzle supply passage  94 , needle valve member  91  will be lifted slowly toward its open position. Thus, fuel pressure at nozzle outlet  96  will be increasing for a majority of time between the opening of needle valve member  91  and the closing of needle valve member  91 . However, when needle control passage  39  is re-opened to high pressure passage  57 , high pressure fluid will act on hydraulic surface  74  and move orifice member  70  toward its second position. Thus it should be appreciated that because needle control chamber  80  will be open to high pressure passage  57  via a relatively unrestricted flow path at this time, the injection event can end abruptly, which is desirable.  
         [0033]     Referring now to  FIG. 3 , an orifice member  170  is illustrated according to an alternate embodiment of the present invention. It should be appreciated that with minor modification of fuel injector  10  illustrated in  FIG. 1 , orifice member  170  could be positioned within injector body  11  to make a complete injector. Orifice member  170  includes a flow restriction orifice  171  and a flow passage  172  and defines a portion of needle control passage  39 . As with orifice member  70 , illustrated in  FIGS. 1 and 2 , orifice member  170  is also movable between an upward, first position and a downward, second position and is biased toward its first position by a biasing spring  182  that is operably positioned within injector body  11 . However, unlike the embodiment illustrated in  FIGS. 1 and 2 , orifice member  170  is positioned in needle control chamber  180 . Thus, as illustrated in  FIG. 3  biasing spring  182  is common biaser that is compressed between orifice member  170  and piston portion  186  of direct control needle valve  190  and acts to bias orifice member  170  toward its first position while biasing needle valve member  191  toward its closed position.  
         [0034]     When needle control passage  39  is open to low pressure passage  36 , such as during an injection event, orifice member  170  will remain in its upward, biased position under the force of biasing spring  182  and the fluid pressure within needle control passage  180 . However, it should be appreciated that while the fluid within needle control chamber  180  is being displaced via flow passage  172 , orifice member  170  will remain in its first position. When orifice member  170  is in its first position, a conical valve seat  173  defined by injector body  11  is closed. Thus, needle control chamber  180  is open to needle control passage  39  via only restricted area flow passage  172 . When needle control passage  39  is opened to high pressure passage  57 , orifice member  170  will be abruptly moved to its second position against the force of biasing spring  182 . When orifice member  170  is in its second position, valve seat  173  is opened and needle control chamber  180  is open to needle control passage  39  via flow passage  172  and an unrestricted flow passage  175 . Thus, a closing hydraulic surface  185  of needle valve  190  is exposed to high pressure fluid via a relatively unrestricted flow passage when orifice member  170  is in its second position. As with the previous embodiment, when orifice member  170  is in its second position, needle control passage  39  is opened to needle control chamber  180  via an unrestricted flow area that includes both unrestricted flow passage  175 , which is a portion of the annular flow area between orifice member  170  and injector body  11 , and flow passage  172 . However, as with the previous embodiment, it should be appreciated that as high pressure fluid flows into needle control chamber  180  via flow passage  172 , the pressure within needle control chamber  180  will increase, thus causing orifice member  170  to be returned to its first position in preparation for the next injection event. In addition, it should be appreciated that direct control needle valve  190  could be composed of two or more pieces, as illustrated, or it could instead be composed of a single component.  
         [0035]     It should be appreciated that flow restriction orifice  171  should be large enough that needle valve member  191  can displace a sufficient amount of fluid via flow passage  172  to move toward its open position when orifice member  170  is in its first position. However, flow restriction orifice  171  should still be sufficiently small that flow passage  172  is a relatively restricted flow passage. Thus, when orifice member  170  is in its first position and needle control passage  39  is opened to low pressure passage  36 , high pressure actuation fluid needle control chamber  180  will drain relatively slowly through flow passage  172  and flow restriction orifice  171 . Therefore, because fluid within needle control chamber  180  is being displaced through restricted flow passage  172 , needle valve member  191  will be lifted toward its open position slowly. In other words, once the valve opening pressure is reached in nozzle supply passage  194 , needle valve member  191  will be lifted slowly toward its open position. However, when needle control passage  39  is re-opened to high pressure passage  57 , high pressure fluid will act on hydraulic surface  174  and move orifice member  170  toward its second position. Thus it should be appreciated that because needle control chamber  180  will be open to high pressure passage  57  via a relatively unrestricted flow path at this time, the injection event can end abruptly, which is desirable.  
         [0036]     Referring now to  FIG. 4 , there is illustrated an orifice member according to yet another embodiment of the present invention. Orifice member  270  is movably positioned within injector body  11 . It should be appreciated that with minor modifications to fuel injector  10 , the orifice member illustrated in  FIG. 5  could be incorporated to make a complete injector. Orifice member  270  is movable between an upward first position and a downward second position and is biased toward its second position by a biasing spring  275 . As illustrated, orifice member  270  defines a flow restriction orifice  278  and a flow passage  272  that fluidly connect a first cavity  276  with a second cavity  277 . Orifice member  270  includes a first hydraulic surface  273  that is exposed to fluid pressure within first cavity  276 , which also contains biasing spring  275 . A check control piston  271  is also movable between an upward first position and a downward second position and is positioned between orifice member  270  and a direct control needle valve  290 . Direct control needle valve  290  includes a needle valve member  291  and is biased toward a closed position by a biasing spring  282  that is positioned in a spring chamber  280 . Check control piston  271  includes a second hydraulic surface  274 , which functions as a closing hydraulic surface for needle valve  290 , that is exposed to fluid pressure within second cavity  277 .  
         [0037]     When needle control passage  39  is opened to low pressure passage  36 , such as at the beginning of an injection event, the fluid within a second cavity  277  is displaced rapidly. However, because first cavity  276  is fluidly connected to second cavity  277 , and therefore needle control passage  39 , via a relatively restricted flow path that includes flow restriction orifice  278  the fluid within first cavity  276  will be displaced slowly. As the fluid within first cavity  276  is slowly displaced, a valve opening pressure can be attained within nozzle supply passage  94 . Once the valve opening pressure is reached, needle valve member  291  can be lifted toward its open position fluidly connecting nozzle outlet  96  to nozzle supply passage  94 . It should be appreciated that for this embodiment of the present invention, the valve opening pressure is the pressure sufficient to lift needle valve member  291 , check control piston  271  and orifice member  270  against the downward force of biasing springs  275  and  282  and the fluid pressure within first cavity  276  that is acting on first hydraulic surface  273 .  
         [0038]     When needle control passage  39  is first opened to high pressure passage  57 , such as just prior to the desired end of the injection event, high pressure can act on closing hydraulic surface  274  to move check control piston  271 , and therefore needle valve member  291  toward their respective downward positions. Because needle control passage  39  is a relatively unrestricted flow path between high pressure passage  57  and second cavity  277 , check control piston  271  and needle valve member  291  can be moved toward their downward, closed positions in an abrupt manner. However, it should be appreciated that orifice member  270  will not immediately move toward its downward position, but will remain relatively stationary in its upward position as needle valve member  291  closes nozzle outlet  96 . Once the fluid pressure acting on first hydraulic surface  273 , combined with the biasing force of biasing spring  275 , overcomes the force of high pressure fluid in second cavity  277 , orifice member  270  will be returned to its downward position in contact with check control piston  271 .  
         [0039]     It should be appreciated that the various sizes and strengths of first hydraulic surface  273 , closing hydraulic surface  274 , biasing spring  275  and biasing spring  282  should be such that even when a valve opening pressure is attained in nozzle supply passage  94 , needle valve member  291  will not lift to its open position when first orifice member  270  is in its downward position and first cavity  276  is open to high pressure passage  57  via flow restriction orifice  278  and flow passage  272 . However, the relative sizes of closing hydraulic surface  274  and opening hydraulic surface  293  and the strength of biasing spring  282  should be such that when closing hydraulic surface  274  is no longer exposed to high pressure in second cavity  277 , a valve opening pressure acting on opening hydraulic surface  293  should be sufficient to move needle valve member  291  upward against the force of biasing spring  282 , biasing spring  275  and the fluid pressure within first cavity  276  to open nozzle outlet  96 . It should be further appreciated that the strength of biasing springs  275  and  282  should be such that needle valve member  291  will remain in its closed position when fuel pressure in nozzle supply passage  94  is below a valve opening pressure, even when second cavity  277  is fluidly connected to low pressure passage  36  via needle control passage  39 .  
         [0040]     In addition to these considerations, it should be appreciated that flow restriction orifice  278  should be large enough that orifice member  270  can displace a sufficient amount of fluid via needle control passage  39  that needle valve member  291  can move toward its open position when fluid within first cavity  276  is being displaced. However, flow restriction orifice  278  should still be sufficiently small that a relatively restricted flow passage exists between first cavity  276  and needle control passage  39 . Thus, when orifice member  270  is in its downward position and needle control passage  39  is opened to low pressure passage  36 , high pressure actuation fluid in first cavity  276  will drain relatively slowly through flow restriction orifice  278 . Therefore, because fluid is being displaced from first cavity  276  via a flow restriction, needle valve member  291  will be lifted toward its open position slowly. In other words, once the valve opening pressure is reached in nozzle supply passage  94 , needle valve member  291  will be lifted slowly toward its open position. Thus, as with the previous embodiments, fuel pressure at nozzle outlet  96  will be increasing for a majority of time between the opening of needle valve member  291  and the closing of needle valve member  291 . However, when needle control passage  39  is re-opened to high pressure passage  57 , high pressure fluid will act on closing hydraulic surface  274  and move check control piston  271  toward its downward position. Thus it should be appreciated that because second cavity  277  is open to high pressure passage  57  via a relatively unrestricted flow path, the injection event can end abruptly, which is desirable.  
         [0041]     It should be appreciated that various modifications could be made to the embodiments of the present invention disclosed herein. For instance, recall that the  FIG. 2  embodiment of the present invention, while the unrestricted flow passage has been illustrated as including a relatively restricted flow passage defined by the orifice member and the annular area around the orifice member. Alternatively, the orifice member could define a restricted flow passage and one or more unrestricted flow passages. Referring in addition to  FIG. 5 , an orifice member  370  is illustrated including a restricted flow passage  372  and two unrestricted flow passages  375 . When orifice member  370  is in its first position, only restricted flow passage  372  fluidly connects upstream portion  69  of needle control passage  39  to downstream portion  78 . However, when orifice member  370  is in the second position, a relatively unrestricted flow path including restricted flow passage  372  and unrestricted flow passages  375  fluidly connect upstream portion  69  to downstream portion  78 . While the orifice member  370  illustrated in  FIG. 5  includes a flat, top surface, the orifice member could instead include an annular top surface. For instance, referring to  FIG. 6 , and orifice member  470  has been illustrated that is similar to orifice member  370 . Orifice member  470  defines a restricted flow passage  472  that opens at the flat top surface of orifice member  470 . However, unlike orifice member  370 , orifice member  470  defines unrestricted flow passages  475  that open at an annular portion of the top surface of orifice member  470 .  
         [0042]     In addition to these modifications, the present invention could be modified as illustrated in  FIGS. 7 and 8 . Referring to  FIGS. 7 and 7   a , an orifice member  570  has been illustrated that defines a restricted flow passage  572  that is fluidly connected to needle control passage  39  at all times. In addition, orifice member  570  defines two slots  588  that can open upstream portion  69  of needle control passage  39  to downstream portion  78  via unrestricted flow passages  575  when orifice member  572  is away from its upward position. Similarly, in  FIGS. 8 and 8   a , an orifice member  670  has been illustrated that defines a restricted flow passage  672  that can fluidly connect upstream portion  69  to downstream portion  78  regardless of the position of orifice member  670 . Orifice member  670  also defines slots  688  that can fluidly connect upstream portion  69  to downstream portion  78  via unrestricted flow passages  675  when orifice member  670  is away from its upward position. As illustrated, the slots can be fluidly connected to the restricted flow passage, as illustrated in the  FIG. 7  embodiment, or they can be blocked from fluid communication with the restricted flow passage, as illustrated in  FIG. 8 .  
         [0043]     In addition to these modifications, while the orifice members of the present invention have been illustrated closing conical valve seats, it should be appreciated that the valve seats could also be flat. For instance, as illustrated in  FIG. 9 , an orifice member  770  has been illustrated in its upward position within a needle control chamber  780 . When orifice member  770  is in this position, needle control passage  39  is open to needle control chamber  780  only via a restricted flow passage  772  defined by orifice member  770 . In addition, when orifice member  770  is in this position, a flat valve seat  773 , defines by injector body  11 , is closed by orifice member  770 . However, when orifice member  770  is away from this position, needle control passage  39  is open to needle control chamber  780  via both restricted flow passage  772  and an unrestricted flow passage  775 , defined by orifice member  770 . While valve seat  773  has been illustrated as a portion of a protrusion that extends from injector body  11  in the  FIG. 9  embodiment, another alternative of a flat valve seat has been illustrated in  FIG. 10 . Note that in  FIG. 10 , valve seat  873  is closed by a raised portion of orifice member  870  when orifice member  870  is in its upward position. In addition, the  FIG. 10  embodiment could be further modified to be a variable area orifice member  970 , as illustrated in  FIG. 11 . Note that orifice member  970  defines an unrestricted passage  975  that is a T-passage that fluidly connects needle control passage  39  to needle control chamber  980  when orifice member  970  is away from its upward position.  
         [0044]     In addition to these modifications, and referring to the  FIG. 3  embodiment, orifice member  170  could be modified as illustrated in  FIG. 12 . Note that orifice member  1070 , illustrated in  FIG. 12 , is movable between an upward position and a downward position about a pin  1088 . Pin  1088  might be desirable to prevent orifice member  1070  from contacting needle valve member  1091  when these components are moving toward each other. Additionally, the present invention could be modified as illustrated in  FIG. 13 . Orifice member  1170 , illustrated in  FIG. 13 , includes a dual flow rate orifice  1171 . By appropriately sizing and shaping dual flow rate orifice  1171 , high pressure fluid flowing into needle control chamber  1180  from needle control passage  39  will be relatively unrestricted. However, fluid flow from needle control chamber  1180  to needle control passage  39 , such as when needle valve member  1191  is moving toward its upward position, will be relatively restricted. Further, the  FIG. 4  embodiment could be modified as illustrated in  FIG. 14 . Note that unlike the  FIG. 4  embodiment, a single biasing spring  1275  biases orifice member  1270  and needle valve member  1291  toward their downward positions.  
       INDUSTRIAL APPLICABILITY  
       [0045]     Referring now to  FIGS. 1 and 2 , just prior to an injection event, low pressure prevails in fuel injector  10 , valve member  35  is in its biased position opening needle control passage  39  to high pressure passage  57 , valve member  25  is in its biased position opening variable pressure passage  29  to high pressure passage  56 , and spool valve member  40  is hydraulically balanced and positioned in its retracted position opening actuation fluid passage  48  to low pressure passage  45 . Orifice member  70  is in its advanced, first position such that needle control chamber  80  is open to needle control passage  39  via only restricted flow orifice  71  and needle valve member  91  is held in its downward, closed position by biasing spring  82 . Prior to the initiation of an injection event, electrical actuator  20  is energized to begin fuel pressurization within fuel injector  10 .  
         [0046]     When electrical actuator  20  is energized, valve member  25  is pulled toward its retracted position by armature  23 . Variable pressure passage  29 , and thus spool cavity  47 , is now blocked from high pressure passage  56  and opened to low pressure passage  26 . With low pressure acting on control surface  46  in spool cavity  47 , spool valve member  40  is moved toward its advanced position as a result of the high pressure acting on biasing surface  41 . Actuation fluid passage  48  is now opened to high pressure passage  56 . High pressure actuation fluid flowing into actuation fluid passage  48 , acts on hydraulic surface  61  of piston  60 , causing piston  60  and plunger  63  to begin to move toward their advanced positions to pressurize fuel in fuel pressurization chamber  67  and nozzle supply passage  94 . However, because closing hydraulic surface  85  is also exposed to high pressure in needle control chamber  80  via needle control passage  39 , needle valve member  91  will not be moved to its upward position to open nozzle outlet  96 . Further, it should be appreciated that piston  60  and plunger  63  move only a slight distance at this time because of hydraulic locking, which is a result of nozzle outlet  96  remaining closed. However, the slight movement of piston  60  and plunger  63  is still sufficient to raise fuel pressure within fuel pressurization chamber  67  to injection pressure levels.  
         [0047]     Just prior to the desired start of injection, electrical actuator  30  is energized and valve member  35  is pulled toward its upward position by armature  33 . Needle control passage  39  is now blocked from high pressure passage  57  and opened to low pressure passage  36 . However, because orifice member  70  is in its upward, first position, downstream portion  78  of needle control passage  39  is opened to low pressure passage  36  only via a restricted flow path. Once the pressure acting on opening hydraulic surface  93  exceeds a valve opening pressure, needle valve member  91  begins moving toward its upward position, and fuel spray into the combustion space can commence. However, because fluid within needle control chamber  80  is being displaced slowly, the opening of needle valve member  91  is slowed. Thus, nozzle outlet  96  is opened slowly by fluid displacement through a restricted flow passage including flow passage  72  defined by orifice member  70 , as a result of movement of needle valve member  91  toward its open position. Because low pressure is acting on hydraulic surface  74 , orifice member  70  will remain stationary in its biased, first position while needle valve member  91  moves from its closed position to its open position. Thus, fluid within needle control chamber  80  is displaced slowly. In addition, fluid within spring chamber  76  will be displaced via fluid passage  79  and flow passage  72 .  
         [0048]     When the desired amount of fuel has been injected by fuel injector  10 , electrical actuator  30  is de-energized and valve member  35  is returned to its downward position by biasing spring  32 . Needle control passage  39  is re-opened to high pressure passage  57 . With high pressure acting on hydraulic surface  74 , orifice member  70  is moved toward its second, downward position against the action of biasing spring  77 . Once orifice member  70  moves from its first, restricted position to its second, unrestricted position, valve seat  73  is opened. Downstream portion  78  of needle control passage  39  is now fluidly connected to high pressure passage  57  via both flow passage  72  and unrestricted flow path  75 . Thus, fluid can be displaced toward needle control chamber  80  in an abrupt manner. Once the pressure acting on closing hydraulic surface  85  exceeds a valve closing pressure, needle valve member  91  is returned to its downward position closing nozzle outlet  96  to end the injection event. Therefore, nozzle outlet  96  is closed quickly as a result of fluid displacement toward closing hydraulic surface  85  via an unrestricted flow passage that includes both flow passage  72  and unrestricted flow passage  75 . Once nozzle outlet  96  is closed, piston  60  and plunger  63  end their downward movement as a result of hydraulic locking. However, these components do not immediately begin to retract because hydraulic surface  61  is still exposed to high pressure fluid in actuation fluid passage  48 . It should be appreciated that if a split injection is desired, electrical actuator  30  would be re-energized and valve member  35  would be returned to its upward position fluidly connecting needle control passage  39  to low pressure passage  36 .  
         [0049]     Once the injection event has ended, the various components of fuel injector  10  reset themselves in preparation for the following injection event. As high pressure actuation fluid flows into spring chamber  76  via fluid passage  79 , pressure within spring chamber  76  increases, causing orifice member  70  to be returned to its first position. Electrical actuator  20  is de-energized and valve member  25  is returned to its downward position under the force of biasing spring  22  to open variable pressure passage  29  is now open to high pressure passage  56 . Control surface  46  is exposed to high pressure within spool cavity  47 . Once nozzle outlet  96  is closed, residual high pressure in actuation fluid passage  48  is sufficient to move pressure relief valve  50  upward away from seat  54  to fluidly connect actuation fluid passage  48  to pressure relief passage  51 . Pressure relief valve  51  can therefore help vent high pressure actuation fluid from actuation fluid passage  48  to prevent pressure spikes from causing undesired secondary injections. At the same time, the upward movement of pressure relief valve  50  causes pin  53  to aid spool valve member  40  in returning to its upward position. Recall that control surface  46  is again exposed to high pressure in spool cavity  47 , causing spool valve member  40  to once again be hydraulically balanced such that it can return to its upward position under the force of biasing spring  44 , in addition to the upward force of pin  53 . When spool valve member  40  begins to retract, piston  60  and plunger  63  end their downward movement, however, as a result of hydraulic locking they do not immediately begin to retract. Once spool valve member  40  is returned to its upward position, actuation fluid passage  48  is blocked from fluid communication with high pressure passage  56  and fluidly connected to low pressure passage  45 , which further reduces the pressure within actuation fluid passage  48 . Piston  60  and plunger  63  can now move toward their retracted positions. As plunger  63  retracts, fuel can be drawn into fuel pressurization chamber  67 .  
         [0050]     Referring now to the embodiment illustrated in  FIG. 3 , prior to an injection event, electrical actuator  20  is energized, variable pressure passage  29  is fluidly connected with low pressure passage  26  by the movement of valve member  25 , actuation fluid passage  48  is fluidly connected to high pressure passage  56  by the movement of spool valve member  40 , and piston  60  and plunger  63  move slightly toward their advanced positions pressurize fuel within fuel pressurization chamber  67 . Just prior to an injection event, electrical actuator  30  is energized and valve member  35  is pulled toward its upward position by armature  33 . Needle control passage  39  is now fluidly connected to low pressure passage  36  and high pressure actuation fluid within needle control chamber  180  can be drained via flow passage  172  and flow restriction orifice  171 . Once a valve opening pressure is reached in nozzle supply passage  94 , needle valve member  191  is lifted toward its upward position and fuel spray into the combustion space can commence. However, once again, because fluid within needle control chamber  180  is being displaced slowly via a restricted flow path, the opening of needle valve member  191  is not abrupt.  
         [0051]     Once the desired amount of fuel has been injected by fuel injector  10 , electrical actuator  30  is de-energized and valve member  35  is returned to its downward position by biasing spring  32 , re-opening needle control passage  39  to high pressure passage  57 . With high pressure acting on hydraulic surface  174 , orifice member  170  is moved toward its second, downward position against the action of biasing spring  182 . Once orifice member  170  opens valve seat  173 , needle control chamber  180  is fluidly connected to high pressure passage  57  via both flow passage  172  and unrestricted flow path  175 . Thus, fluid is quickly displaced toward needle control chamber  180 . The dramatic increase in pressure that results from this large fluid displacement, together with the action of orifice member  170  against biasing spring  182 , causes needle valve member  191  to be moved to its downward position to end the injection event. Once the injection event is ended, the various components of fuel injector  10  reset themselves in the manner described for the  FIGS. 1 and 2  embodiment of the present invention.  
         [0052]     Referring now to the  FIG. 4  embodiment, prior to an injection event, orifice member  270  and check control piston  271  are in contact and in their respective downward positions. Needle valve member  291  is held in its downward position closing nozzle outlet  96  by biasing spring  282 , check control piston  271 , orifice member  270  and biasing spring  275 . Prior to the desired start of the injection event, electrical actuator  20  is energized, variable pressure passage  29  is fluidly connected with low pressure passage  26  by the movement of valve member  25 , actuation fluid passage  48  is fluidly connected to high pressure passage  56  by the movement of spool valve member  40 , and piston  60  and plunger  63  move slightly toward their advanced positions pressurize fuel within fuel pressurization chamber  67 . Just prior to an injection event, electrical actuator  30  is energized and valve member  35  is pulled toward its upward position by armature  33 . Needle control passage  39  is now fluidly connected to low pressure passage  36 .  
         [0053]     When needle control passage  39  is opened to low pressure passage  36 , pressure within second cavity  277  is dramatically reduced. However, orifice member  270 , check control piston  271  and needle valve member  291  remain in their respective downward positions as a result of the downward force of both biasing spring  275  and the high pressure fluid acting on first hydraulic surface  273  in first cavity  276 . However, because first cavity  276  is fluidly connected to needle control passage  39 , and therefore low pressure passage  36 , via flow restriction orifice  278 , fluid within first cavity  276  is slowly displaced. As high pressure fluid within first cavity  276  is slowly displaced via flow passage  272  and flow restriction orifice  278 , the fuel pressure acting on opening hydraulic surface  293  within nozzle supply passage  94  begins to approach a valve opening pressure. Once a valve opening pressure is attained, needle valve member  291  is lifted toward its open position against the force of biasing springs  275  and  282 . As fluid within first cavity  276  continues to be slowly displaced, needle valve member  291  slowly moves toward its upward, open position.  
         [0054]     Once the desired amount of fuel has been injected by fuel injector  10 , electrical actuator  30  is de-activated and valve member  35  is returned to its biased position fluidly connecting needle control passage  39  to high pressure passage  57 . Once needle control passage  39  is opened to high pressure passage  57 , high pressure can act on closing hydraulic surface  274  to move check control piston  271  toward its downward position. As check control piston  271  moves downward, needle valve member  291  is moved to close nozzle outlet  96  and end the injection event. Because second cavity  277  is open to high pressure passage  57  via a relatively unrestricted flow passage, needle control passage  39 , the closing of needle valve member  291  is abrupt, as opposed to the slowed opening of needle valve member  291  that is facilitated by flow restriction orifice  278 . Once the injection event has ended, electrical actuator  20  is de-energized and the various components of fuel injector  10  reset themselves in preparation for the subsequent injection event.  
         [0055]     Further, in addition to the modifications to the present invention illustrated previously, and as indicated previously, it should be appreciated that while a hydraulically actuated fuel injector has been illustrated, the present invention would find application with a mechanically actuated fuel injector or with a unit injector included in a common rail fuel injection system. Further, those skilled in the art will appreciate that for a hydraulically actuated fuel injector, any suitable actuation fluid could be used, such as engine lubricating oil, fuel or coolant fluid.  
         [0056]     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.