Patent Publication Number: US-6655602-B2

Title: Fuel injector having a hydraulically actuated control valve and hydraulic system using same

Description:
TECHNICAL FIELD 
     This invention relates generally to hydraulic systems, and more particularly to fuel injectors having hydraulically actuated control valves. 
     BACKGROUND 
     Several recent advances have been made in the area of hydraulically actuated fuel injectors. While many of these advances have been successful, engineers are always searching for ways to improve the performance of hydraulically actuated fuel injectors. For instance, in some hydraulically actuated fuel injectors, a pressure communication passage extends from a pilot valve to the top of the needle valve member, with a branch of this passage running to the underside of a spool valve to control movement of the same. One example of a fuel injector including such a configuration is described in U.S. Pat. No. 5,833,146, issued to Hefler on Nov. 10, 1998. While this design has performed well, a substantial amount of fluid flow past the pilot valve is required to move the spool valve due to the relatively large amount of fluid that must be displaced by movement of the spool valve member. 
     During cold start, when the oil in the pressure communication passage is relatively viscous, it is more difficult to displace the fluid past the relatively small flow area through the pilot valve to allow the spool valve to advance to its open position. This in turn can inhibit the fuel injector from performing optimally when the actuation fluid, typically oil, is viscous at cold start. In order to alleviate this need for substantial fluid flow around the pilot valve member, and to allow the fuel injector to perform closer to optimum at cold start, it would be desirable to make it easier to evacuate fluid from the underside of the spool, particularly during cold start and other high viscosity situations. 
     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 valve assembly includes a valve body that defines a first passage, a second passage and a variable pressure passage. A spool valve member is positioned in the valve body and is movable between a first position in which the first passage is open to the variable pressure passage and a second position in which the second passage is open to the variable pressure passage. A spool control volume is defined by at least one of the valve body and the spool valve member. A control valve member is positioned in the valve body and is movable between an open position in which the first passage is in fluid communication with the spool control volume and a closed position in which the first passage is blocked from fluid communication with the spool control volume. The control valve member includes a hydraulic surface that defines a hydraulic force direction. A biaser is operably in contact with the control valve member to produce a biasing force in opposition to the hydraulic force direction. 
     In another aspect of the present invention, a hydraulically actuated device includes a device body that defines a high pressure passage, a low pressure passage and a variable pressure passage. A source of high pressure actuation fluid is connected to the high pressure passage. A low pressure reservoir is connected to the low pressure passage. A spool valve member is movably positioned in the device body. A spool control volume is defined by at least one of the device body and the spool valve member. A control valve member is movably positioned in the device body and includes a hydraulic surface that defines a hydraulic force direction. The hydraulic surface is exposed to the high pressure passage when the control valve member is in a first position and is exposed to the low pressure passage when the control valve member is in a second position. The hydraulic surface is exposed to fluid pressure in a pressure cavity that is fluidly isolated from the spool control volume. A biaser is operably in contact with the control valve member to produce a biasing force in opposition to the hydraulic force direction. A reciprocating piston is included in the hydraulic device that has a hydraulic surface exposed to fluid pressure in the variable pressure passage. 
     In yet another aspect of the present invention, a method of operating a control valve includes providing a valve assembly that includes a valve body which defines a low pressure passage and a high pressure passage. A pilot valve member, a control valve member and a spool valve member are included in the valve body. The pilot valve member is moved from a first position to a second position to expose a hydraulic surface of the control valve member to the low pressure passage. The control valve member is then moved to a closed position blocking a control pressure surface of the spool valve member from the high pressure passage. Next, the spool valve member is moved from a first position to a second position. The pilot valve member is then returned to the first position to expose the hydraulic surface of the control valve member to the high pressure passage. The control valve member is next moved to an open position exposing the control pressure surface of the spool valve member to the high pressure passage. The spool valve member is then moved to the first position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic representation of a hydraulic system that includes a hydraulic device according to the present invention; 
     FIG. 2 is a diagrammatic representation of hydraulically-actuated electronically-controlled fuel injector according to the present invention; and 
     FIG. 3 is a sectioned side view of the spool valve assembly portion of the fuel injector of FIG.  2 . 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, hydraulic system  10  includes a hydraulically-actuated device  11 , such as a fuel injector or an engine valve. A control valve  12  alternately opens hydraulically-actuated device  11  to a source of high pressure fluid  13  or a low pressure fluid reservoir  14 . The state of control valve  12  is controlled by energizing and de-energizing an electrical actuating device  16 , which is preferably a solenoid but could also be another suitable device such as a piezoelectric actuator. Electrical actuating device  16  is controlled in its operation by a conventional electronic control module  15  via communication line  29 . 
     Control valve  12  includes a valve body  19  that defines a high pressure inlet  20  that is connected to the source of high pressure fluid  13  via a high pressure supply line  26 . In this embodiment, valve body  19  also defines a pair of low pressure vents  21  and a low pressure drain  22 . These three low pressure openings communicate with low pressure fluid reservoir  14  via a low pressure passage  27 . 
     Referring to FIGS. 2 and 3 there is shown a diagrammatic sectioned side view of a hydraulically-actuated electronically-controlled fuel injector  30  according to the present invention. Fuel injector  30  includes an injector body  31  made up of various components that are attached to one another in a manner well known in the art and a substantial number of internal movable components positioned as they would be just prior to an injection event. Actuation fluid, which is preferably high pressure oil, can flow into a high pressure actuation fluid passage  46  that is defined by injector body  31  via an actuation fluid inlet  20  and high pressure supply line  26  from the source of high pressure fluid  13 . At the end of an injection event, actuation fluid can flow out of a low pressure passage  23  that is defined by injector body  31  via an actuation fluid vent  21  into low pressure fluid reservoir  14 . While a number of different fluids could be used as actuation fluid, the present invention preferably utilizes engine lubricating oil. 
     Fuel injector  30  is controlled in operation by a control valve  12  that includes an electrical actuator  16  which is preferably a solenoid  33 , but could also be another suitable device such as a piezoelectric actuator. Control valve  12  is positioned in injector body  31  and attached by fasteners  36 , which are preferably bolts but could be another suitable attachment device. Solenoid  33  includes a coil  35 , an armature  34  and a pin  37  that is operably coupled to a pilot valve member  38 . Pilot valve member  38  is preferably a ball valve member and is moveable within injector body  31  between a first position in which it closes a low pressure seat  41  and a second position in which it closes a high pressure seat  40 . While pilot valve member  38  has been shown as a ball valve member, it should be appreciated that it could instead be a spool valve member, poppet valve member, or another suitable device. Injector body  31  also defines a pressure communication passage  42  that opens into a control volume  39  between low pressure seat  41  and high pressure seat  40 . Prior to an injection event when solenoid  33  is de-energized, pilot valve member  38  is positioned in its first position to close low pressure seat  41 , as shown. When pilot valve member  38  is in this position pressure communication passage  42  is open to high pressure actuation fluid supply passage  46  via control volume  39  and blocked from fluid communication with low pressure passage  23 . When solenoid  33  is energized, armature  34  pushes pin  37  downward to move pilot valve member  38  toward its second position to close high pressure seat  40 . When pilot valve member  38  is in the second position, pressure communication passage  42  is closed to high pressure actuation fluid supply passage  46  and open to low pressure passage  23  via control volume  39 . 
     Pressure communication passage  42  includes a first branch passage  43  that is fluidly connected to a needle control chamber  103  and a second branch passage  44  that is in fluid communication with a pressure cavity  52 . Pressure cavity  52  is defined in part by injector body  31  and a control valve member  50 . Control valve member  50  is positioned within injector body  31  and is movable between an open position and a closed position. Control valve member  50  includes a hydraulic surface  51  that is exposed to fluid pressure in pressure cavity  52 . When solenoid  33  is de-energized, and pilot valve member  38  is positioned in its first position closing low pressure seat  41 , pressure communication passage  42  is open to high pressure passage  45  and hydraulic surface  51  is exposed to high pressure in second branch passage  44  via pressure cavity  52 . When solenoid  33  is energized and pilot valve member  38  is moved to its second position to close high pressure seat  40 , pressure communication passage  42  is open to low pressure passage  47  and hydraulic surface  51  is exposed to low pressure in second branch passage  44  via pressure cavity  52 . 
     Control valve member  50  also includes a high pressure surface  53  that is continuously exposed to high pressure in high pressure passage  45 . Control valve member  50  is biased toward its upward closed position by the continuous hydraulic force produced by the high pressure fluid in high pressure passage  45  that acts on high pressure surface  53 . This force direction is in opposition to a hydraulic force direction defined by hydraulic surface  51 . However, because high pressure surface  53  has a smaller effective area than hydraulic surface  51 , the hydraulic force acting on hydraulic surface  51  is sufficient to move control valve member  50  toward its downward open position against the hydraulic force acting on high pressure surface  53  when pressure cavity  52  is in fluid communication with high pressure passage  45 . While the present invention has been shown using a hydraulic biaser for control valve member  50 , it should be appreciated that a mechanical biaser, such as a biasing spring, or a combination of hydraulic and mechanical biasers could be substituted for use in the present invention. 
     At least one flat surface  54  is machined on control valve member  50  to form a flow path  64  between high pressure passage  45  and spool control volume  70 . When control valve member  50  is in its closed position, a first valve surface  56  closes a valve seat  72  that is defined by injector body  31  and blocks flow path  64  and high pressure passage  45  from fluid communication with spool control volume  70 . When control valve member  50  is in its open position, first valve surface  56  is out of contact with valve seat  72  and flow path  64  fluidly connects high pressure passage  45  to spool control volume  70 . 
     Control valve member  50  includes a conical valve surface  57  and is guided in part by a sleeve  71  that is positioned within injector body  31 . When control valve member  50  is in its closed, upward position, conical valve surface  57  is out of contact with a conical valve seat  73  that is defined by sleeve  71 . When control valve member  50  is in this position, a spool control volume  70  is open to low pressure vent  21  via a pressure relief passage  75 . Spool control volume  70  is preferably defined by at least one of injector body  31  and a spool valve member  60  and is fluidly isolated from pressure cavity  52 . When control valve member  50  is in its open, downward position, conical valve seat  73  is closed by conical valve surface  57  and fluid communication between spool control volume  70  and pressure relief passage  75  is blocked. 
     Control valve member  50  is preferably positioned at least partially within spool valve member  60 , which is movably positioned in injector body  31 . Spool valve member  60  includes a control pressure surface  67  that is exposed to pressure in spool control volume  70 . A high pressure surface  61  is also included on spool valve member  60  that is continuously exposed to high pressure in high pressure actuation fluid supply passage  46 . Control pressure surface  67  and high pressure surface  61  are preferably sized to have equal effective areas such that when spool control volume  70  is fluidly connected to high pressure passage  45 , spool valve member  60  is hydraulically balanced and biased toward its second position only by the action of a biasing spring  69 . 
     Also included on spool valve member  60  are a high pressure annulus  62  and a low pressure annulus  66 . A variable pressure passage  49  defined by injector body  31  is alternately exposed to fluid pressure in high pressure passage  45  or low pressure passage  47  via high pressure annulus  62  and low pressure annulus  66  depending on the relative positioning of spool valve member  60 . When spool valve member  60  is in its second position, as shown, high pressure annulus  62  is blocked from high pressure passage  45  while low pressure annulus  66  opens variable pressure passage  49  to low pressure passage  47 . When spool valve member  60  is in its first position, low pressure annulus  66  is closed to block variable pressure passage  49  from fluid communication with low pressure passage  47  while high pressure annulus  62  opens variable pressure passage  49  to high pressure passage  45 . 
     Returning now to fuel injector  30 , injector body  31  also includes a reciprocating pumping element, piston  85  and plunger  88 , which can move between an upward position, as shown, and a downward advanced position. Piston  85  is biased toward its upward position by a return spring  87 . Connected to piston  85  is plunger  88  which is biased toward its upward position by return spring  87 . Piston  85  advances due to the hydraulic pressure force exerted on a hydraulic surface  86  which is exposed to fluid pressure in actuation fluid cavity  83 . With only hydraulic surface  86  exposed to high pressure in actuation fluid cavity  83 , piston  85  would accelerate downward at a rate slower than it otherwise would if the full fluid pressure were acting over the complete top surface of piston  85 . However, the volume above an annular top surface  82  of piston  85  is filled with fluid from variable pressure passage  49  via an auxiliary passage  79 . When piston  85  begins to advance, plunger  88  advances in a corresponding fashion and acts as the hydraulic means for pressurizing fuel within a fuel pressurization chamber  89  that is connected to a fuel inlet  25  past a ball check valve  90 . Fuel inlet  25  is connected to a source of fuel  91  via a fuel supply passage  93 . When plunger  88  is returning to its upward position, fuel is drawn into fuel pressurization chamber  89  past check valve  90 . During an injection event as plunger  88  moves toward its downward position, check valve  90  is closed and plunger  88  can act to compress fuel within fuel pressurization chamber  89 . Fuel pressurization chamber  89  is fluidly connected to a nozzle outlet  110  via a nozzle supply passage  106 . 
     A pressure relief valve  80  is movably positioned in injector body  31  to vent pressure spikes from actuation fluid cavity  83 . Pressure spikes can be created when piston  85  and plunger  88  abruptly stop their downward movement due to the abrupt closure of nozzle outlet  110 . 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, pressure relief passage  75  extends between actuation fluid cavity  83  and low pressure vent  21 . When control valve member  50  is in its open position, such as between injection events, a pin  77  holds pressure relief valve  80  downward to open a seat  78 . When pressure relief valve  80  is in this position, actuation fluid cavity  83  is open to pressure relief passage  75  and pressure can build within actuation fluid cavity  83  in preparation for an injection event. When control valve member  50  is away from its open position, such as during an injection event, pressure relief valve  80  can act against pin  77  under the action of high pressure oil in actuation fluid cavity  83  to close seat  78  and allow high pressure oil within actuation fluid cavity  83  to be vented to pressure relief passage  75 . 
     Returning to fuel injector  30 , a direct control needle valve  100  is positioned in injector body  31  and includes a needle valve member  101  that is movable between a first position, in which nozzle outlet  110  is open, and a downward second position in which nozzle outlet  110  is blocked. Needle valve member  101  is mechanically biased toward its downward closed position by a biasing spring  104 . Needle valve member  101  includes opening hydraulic surfaces  108  that are exposed to fluid pressure within a nozzle chamber  105  and a closing hydraulic surface  102  that is exposed to fluid pressure within a needle control chamber  103 . As illustrated in FIG. 2, nozzle chamber  105  is fluidly isolated from spool control volume  70 , while needle control chamber  103  is in fluid communication with first branch passage  43  of pressure communication passage  42 . Therefore, closing hydraulic surface  102  is exposed to high pressure passage  45  when solenoid  33  is de-energized and pilot valve member  38  is positioned to close low pressure seat  41 . Similarly, closing hydraulic surface  102  is exposed to low pressure passage  47  when solenoid  33  is energized and pilot valve member  38  is positioned to close high pressure seat  40 . 
     Closing hydraulic surface  102  and opening hydraulic surfaces  108  are sized such that even when a valve opening pressure is attained in nozzle chamber  105 , needle valve member  101  will not move against the action of biasing spring  104  when needle control chamber  103  is exposed to high pressure in first branch passage  43 . In a similar manner, once solenoid  33  is de-energized at the end of an injection event, the high pressure in needle control chamber  103  will act to quickly move needle valve member  101  to close nozzle outlet  110  and end the injection event. Additionally, because closing hydraulic surface  102  has a larger effective area than opening hydraulic surfaces  108 , once solenoid  33  is de-energized, the high pressure acting on closing hydraulic surface  102  will prevent needle valve member  101  from re-opening nozzle outlet  110  and injecting additional fuel into the combustion space. However, it should be appreciated that the relative sizes of closing hydraulic surface  102  and opening hydraulic surfaces  108  and the strength of biasing spring  104  should be such that when closing hydraulic surface  102  is exposed to low pressure in pressure communication passage  42 , the high pressure acting on opening hydraulic surfaces  108  should be sufficient to move needle valve member  101  upward against the force of biasing spring  104  to open nozzle outlet  110 . 
     INDUSTRIAL APPLICABILITY 
     Prior to the start of an injection event, low pressure in fuel pressurization chamber  89  prevails, plunger  88  is in its retracted position, pilot valve member  38  is positioned to close low pressure seat  40  by the force of high pressure fluid in high pressure actuation fluid supply passage  46  and needle valve member  101  is in its biased position closing nozzle outlet  110 . Spool control volume  70  is in fluid communication with high pressure passage  45  via flow path  64  and actuation fluid cavity  83  is in fluid communication with low pressure passage  47  via variable pressure passage  49 . Control valve member  50  is hydraulically biased toward its open position by the high pressure in first branch passage  44  which is acting on hydraulic surface  51  in pressure cavity  52 . Spool valve member  60  is hydraulically balanced and biased toward its second position by biasing spring  69 . Recall that when spool valve member  60  is in this position, control pressure surface  67  is exposed to high pressure in high pressure passage  45  via flow path  64 . The injection event is initiated by activation of solenoid  33 , which causes armature  34  to push pin  37  downward to move pilot valve member  38  to close high pressure seat  40 . 
     When pilot valve member  38  closes high pressure seat  40 , pressure communication passage  42 , first branch passage  43  and second branch passage  44  become fluidly connected to low pressure passage  23  via control volume  39 . This causes a dramatic drop in pressure in both pressure cavity  52  and in needle control chamber  103 . The drop in pressure in pressure cavity  52  results in a hydraulic imbalance of the pressures acting on control valve member  50 . Because low pressure is now acting on hydraulic surface  51 , the high pressure acting on high pressure surface  53  is sufficient to move control valve member  50  upward toward its closed position. It should be appreciated that the amount of fluid displaced by control valve member  50  is a fraction of the fluid that must be displaced by spool valve member  70 . As control valve member  50  advances, valve surface  52  closes valve seat  72 , thus opening spool control volume  70  to low pressure vent  21  via pressure relief passage  75 . The exposure of control pressure surface  67  to low pressure results in a hydraulic imbalance of spool valve member  60 . 
     Because spool valve member  60  is no longer hydraulically balanced, it moves toward its downward, first position under the hydraulic force of high pressure fluid acting on high pressure surface  61  in high pressure passage  45 . As spool valve member  60  moves toward its downward position, low pressure annulus  66  closes variable pressure passage  49  to low pressure passage  47 . As spool valve member  60  continues to advance, high pressure annulus  62  opens variable pressure passage  49  to high pressure passage  45 , thus beginning the flow of high pressure actuation fluid to actuation fluid cavity  83 . Because control valve member  50  is in its upward position, ball valve member  80  is free to move upward against the action of pin  77 , to close low pressure seat  78 . 
     When actuation fluid cavity  83  becomes fluidly connected to high pressure passage  45 , the high pressure acting on hydraulic surface  86  causes piston  85  to move downward against the action of biasing spring  87 . Also, because variable pressure passage  49  is fluidly connected to high pressure passage  45 , annular top surface  82  is exposed to high pressure via auxiliary passage  79 . Recall that because control valve member  50  is in its closed position, pressure relief valve  80  is positioned to close seat  78 , thus blocking actuation fluid cavity  83  from pressure relief passage  75  and allowing pressure build-up in the same. The downward movement of piston  85  results in a corresponding downward movement of plunger  88 . The downward movement of plunger  88  closes check valve  90  and raises the pressure of the fuel within fuel pressurization chamber  89 , nozzle supply passage  106  and nozzle chamber  105 . Recall that low pressure is acting on closing hydraulic surface  102  because needle control chamber  103  is fluidly connected to low pressure passage  47  via pressure communication passage  42 . The increasing pressure of the fuel within nozzle chamber  105  acts on opening hydraulic surfaces  108  of needle valve member  101 . When the pressure exerted on opening hydraulic surfaces  108  exceeds a valve opening pressure, needle valve member  101  is lifted against the action of biasing spring  104 , and fuel is allowed to spray into the combustion chamber from nozzle outlet  110 . 
     Shortly before the desired amount of fuel has been injected into the combustion space, current to solenoid  33  is ended to end the injection event. Solenoid  33  is de-energized and pilot valve member  38  moves under the hydraulic force of high pressure actuation fluid in high pressure actuation fluid supply passage  46  to close low pressure seat  41  which in turn closes pressure communication passage  42  from fluid communication with low pressure passage  23  and fluidly connects it to the source of high pressure actuation fluid  13 . Pressure communication passage  42  now delivers high pressure actuation fluid to both pressure cavity  52  and needle control chamber  103 . The high pressure within needle control chamber  103  acts on closing hydraulic surface  102  and causes needle valve member  101  to move to its downward, closed position to close nozzle outlet  110 . Also, because high pressure is now acting on hydraulic surface  51 , control valve member  50  starts moving toward its downward position. 
     As control valve member  50  moves toward its downward position, valve surface  56  opens valve seat  72 , which fluidly connects spool control volume  70  with high pressure passage  45 . As control valve member  50  continues to advance, valve surface  57  closes valve seat  73 , thus closing spool control volume  70  from pressure relief passage  75 . During this movement, end  58  comes back into contact with pin  77 , which moves ball valve member  80  to open seat  78 . This allows high pressure actuation fluid in actuation fluid cavity  83  to be vented in pressure relief passage  75 , thus preventing any secondary injection events. 
     As control valve  50  advances, spool control volume  70  opens to high pressure passage  45 , and spool valve member  60  once again becomes hydraulically balanced and moves toward its upward position under the action of biasing spring  69 . This upward movement allows low pressure annulus  66  to open variable pressure passage  49  to low pressure passage  47  while high pressure annulus  62  is closed, blocking high pressure passage  45  from fluid communication with the same. Variable pressure passage  49  now exposes actuation fluid cavity  83  to low pressure via low pressure passage  47 . 
     Just prior to the opening of variable pressure passage  49  to low pressure passage  47 , the downward decent of piston  85  and plunger  88  ends. Once variable pressure passage  49  is open to low pressure passage  47 , hydraulic surface  86  is exposed to low pressure in actuation fluid cavity  83  and piston  85  and plunger  88  move toward their upward, biased positions under the action of biasing spring  87 . This upward movement of plunger  88  relieves the pressure on fuel within fuel pressurization chamber  89  and causes a corresponding drop in pressure nozzle supply passage  106  and nozzle chamber  105 . 
     Between injection events various components of injector body  31  begin to reset themselves in preparation for the next injection event. Because the pressure acting on piston  85  and plunger  88  has dropped, return spring  87  moves piston  85  and plunger  88  back to their retracted positions. The retracting movement of plunger  88  causes fuel from fuel inlet  25  to be pulled into fuel pressurization chamber  89  via fuel supply passage  93 . 
     The present invention allows hydraulically actuated fuel injectors to perform more closely to expected levels by removing the need for a large volume of flow around pilot valve member  38 . By rearranging the plumbing within injector body  31  to connect the high and low pressure passages to spool control volume  70  on a separate fluid circuit than that of the needle control chamber, pilot valve member  38  can function merely as a pressure switch. By utilizing a control valve member  50  that requires only a small amount of fluid flow due to the small distance that it must move, only a small amount of fluid flow past pilot valve member  38  is needed. Therefore, the present invention can allow hydraulically actuated fuel injectors to perform closer to expected even during cold start conditions when the oil is relatively viscous. 
     It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present invention in any way. For instance, while the control valve member has been illustrated as being positioned within an inner diameter of the spool valve member, it should be appreciated that this is not necessary. With modifications to the various high low and variable pressure passageways, control valve member could instead be positioned outside the spool valve member and control the flow to the spool control volume. Additionally, while the spool valve member has been illustrated having hydraulic surfaces with relatively equal effective areas such that the spool valve member is hydraulically balanced when high pressure is acting on both surfaces, the present invention does not require this. In particular, these surfaces could be sized such that spool valve member is biased in one direction when high pressure is acting on both surfaces. Further, this could be exploited to remove the need for a mechanical biaser acting on the spool valve member. Finally, while the control valve member has been shown having only a hydraulic bias, it should be appreciated that a mechanical biaser could be substituted, or added to act with the hydraulic bias. Thus, those skilled in the art will appreciate that other aspects and features of the present invention can be obtained from a study of the drawings, the disclosure, and the appended claims.