Fuel injection system with common actuation device and engine using same

Abstract
The present invention relates to engines having common rail fuel injection systems. In traditional common rail fuel injection systems, each fuel injector utilized by the fuel system includes its own solenoid. These individual solenoids must cooperate to ensure that the proper amount of fuel is being injected from each injector at the proper time. It is believed in the art that a reduction in the number of moving or electrical components in the fuel injection system can improve robustness of the system. Therefore, the fuel injection system of the present invention includes fuel injectors that are controlled in operation by a common electronic actuator that is positioned remote from the fuel injectors.
Description




TECHNICAL FIELD




This invention relates generally to engines, and more particularly to common rail fuel injection systems that use a common electrical actuator(s) to control multiple fuel injectors.




BACKGROUND ART




Common rail fuel injection systems are becoming more widespread for use with diesel engines. One example of such a fuel injection system is shown and described in U.S. Pat. No. 5,133,645, which issued to Crowley et al. on Jul. 28, 1992. Crowley et al. includes an electronic control module and an electronic distribution unit which control a plurality of high pressure fuel supply pumps and fuel injectors. As with other traditional common rail fuel injection systems, each of the fuel injectors included in the Crowley et al. fuel injection system includes its own individual electrical actuator. In this and other common rail fuel injection systems, the individual electrical actuators must cooperate to ensure that the proper amount of fuel is injected from each injector at the proper time. While the Crowley fuel injection system has performed adequately, there is room for improvement. For instance, if the number of electrical actuators, or solenoids, could be reduced, this could benefit the fuel infection system in a number of ways. First, because the number of parts has been reduced, there are less parts that can fail during system operation and hinder system performance. Additionally, injector performance variability might be reduced. Any reduction in the number of moving and/or electrical components should improve system robustness.




The present invention is directed to overcoming one or more of the problems as set forth above.




DISCLOSURE OF THE INVENTION




In one aspect of the present invention, an engine comprises an engine housing, a high pressure fuel rail and a low pressure fuel drain. A plurality of fuel injectors included in a fuel injection system are positioned within the engine housing and are fluidly connected to the fuel rail. Each of the plurality of fuel injectors includes an injector body that defines a nozzle outlet and a nozzle supply passage. Also included in each of the plurality of fuel injectors is a needle valve member that is movably positioned in the injector body adjacent the nozzle outlet. A fluid switch that has a plurality of positions is also included in the engine. An electronically controlled valve is positioned between the fluid switch and the fuel drain. A different one of the plurality of fuel injectors is fluidly connected to the electronically controlled valve at each of the plurality of positions of the fluid switch.




In another aspect of the present invention, a fuel injection system comprises a high pressure fuel rail and a low pressure fuel drain. A plurality of fuel injectors is fluidly connected to the high pressure fuel rail. Each of the plurality of fuel injectors includes an injector body that defines a nozzle outlet, at least one high pressure fluid inlet, at least one low pressure fluid drain, at least one fluid passageway and a nozzle supply passage, and includes a direct control needle valve member movably positioned in the injector body adjacent the nozzle outlet. The direct control needle valve member includes a closing hydraulic surface that is exposed to fluid pressure in a needle control chamber. A first of the at least one fluid passageways is fluidly connected to the high pressure fuel rail. A second of the at least one fluid passageways is fluidly connected to the low pressure fuel drain. A fluid switch is included in the fuel injection system that has a plurality of positions. An electronically controlled valve is positioned remote from the plurality of fuel injectors fluidly between the fluid switch and the fuel drain. A different one of the plurality of fuel injectors is fluidly connected to the electronically controlled valve at each of the plurality of positions.




In yet another aspect of the present Invention, a method of fuel injection comprises providing an engine that includes a fuel injection system. The fuel injection system has a high pressure fuel rail, a low pressure fuel drain, a plurality of fuel injectors that each include an injector body that defines a needle control chamber, a fluid switch having a plurality of positions and an electronically controlled valve. The electronically controlled valve is positioned remote from the plurality of fuel injectors between the fluid switch and the low pressure fuel drain. One of the plurality of fuel injectors is enabled to be fluidly connected to the electronically controlled valve, in part by moving the fluid switch to a first position. Next, the electronically controlled valve is moved to an open position to open the needle control chamber of the one fuel injector to fluid communication with the low pressure fuel drain. An amount of fuel is then injected from the one fuel injector. The electronically controlled valve is next moved to a closed position to block the needle control chamber of the one fuel injector from fluid communication with the low pressure fuel drain. The one fuel injector is then prevented from being open to the electronically controlled valve and an other of the plurality of fuel injectors is enabled to be fluidly connected to the electronically controlled valve, in part by moving the fluid switch to a second position.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a schematic representation of a fuel injection system according to one embodiment of the present invention;





FIG. 2

is a sectioned diagrammatic representation of a fluid switch for use with the fuel injection system of

FIG. 1

;





FIG. 3

is a sectioned diagrammatic representation of a fuel injector for use with the fuel injection system of

FIG. 1

;





FIG. 4

is a schematic representation of a fuel injection system according to another embodiment of the present invention;





FIG. 5

is a sectioned diagrammatic representation of a fuel injector for use with the fuel injection system of

FIG. 4

;





FIG. 6

is a schematic representation of a fuel injection system according to yet another embodiment of the present invention;





FIG. 7

is a sectioned diagrammatic representation of a fuel injector for use with the fuel injection system of

FIG. 6

;





FIGS. 8



a-f


are graphs of pressure release switch position, pressure release actuator current, pressure release valve position, net force on the needle, needle position and injection rate, respectively, versus time for the fuel injector of

FIG. 3

for one injection cycle;





FIGS. 9



a-h


are graphs of pressure release switch position, pressure release actuator current, pressure release valve position, net force on the needle, flow area to the nozzle, injection rate, rate shaping actuator current and rate shaping valve position, respectively, versus time for the fuel injector of

FIG. 5

for one injection cycle;





FIGS. 10



a-i


are graphs of pressure release switch position, pressure release actuator current, net force on the needle, flow area to the nozzle, injection rate, rate shaping valve position, pressure build-up actuator current, pressure build-up valve position and pressure build-up switch position, respectively, versus time for the fuel injector of

FIG. 7

for one injection cycle; and





FIG. 11

is a graphical representation of total fuel consumption versus time for the fuel injection systems of

FIGS. 1

,


4


and


6


.











BEST MODE FOR CARRYING OUT THE INVENTION




Referring now to

FIG. 1

, there is shown an engine


10


including a common rail fuel injection system


11


according to the present invention. Fuel injection system


11


is positioned within an engine housing


12


and includes a low pressure fuel drain, which is preferably a fuel tank


13


, that is in fluid communication with a high pressure fuel rail


16


. A high pressure pump


15


is positioned between fuel tank


13


and high pressure fuel rail


16


, and is supplied with fuel from fuel tank


13


by a gear pump


14


. High pressure fuel rail


16


includes a plurality of outlets


17


that are in fluid communication with an equal number of fuel injectors


60


via high pressure fuel supply lines


18


.




Each fuel injector


60


includes an injector body


61


that defines a nozzle outlet


99


that can spray fuel into a combustion chamber of engine


10


. Each fuel injector


60


also defines a pressure release drain


62


for reduction of internal pressure to allow injection to take place. A pressure release switch


20


is in fluid communication with each pressure release drain


62


via a series of drain passages


21


. Cam


19


of pressure release switch


20


is driven by a crank and preferably rotates at one half the speed of the engine. Referring in addition to

FIG. 2

, there is shown a sectioned view of a preferred version of pressure release switch


20


. Included in pressure release switch


20


are a number of spring biased valve members


23


, equal to the number of fuel injectors


60


included in fuel injection system


11


. Each valve member


23


is biased toward a first, or left, position by a biasing spring


25


and includes a contact surface


24


, which is preferably a convex surface. As cam


19


rotates, a contact platform


22


is rotated which comes in contact with contact surface


24


of valve member


23


. Contact platform


22


preferably includes sloped sides such that contact surface


24


can move smoothly over contact platform


22


, to allow valve member


23


to make a smooth transition to its second, or right, position. When valve member


23


is in its biased, first position, an annulus


26


, included on valve member


23


is out of fluid communication with drain passage


21


and a main passage


29


, as illustrated in

FIG. 2

by valve member


23




b


. However, when valve member


23


is in its second position, such as valve member


23




a


, annulus


26


is open to main passage


29


and drain passage


21


via drain passage


28


.




When annulus


26


is open to drain passage


28


for a particular fuel injector


60


, that fuel injector


60


is capable of being connected to fuel tank


13


via main passage


29


. Therefore, only one fuel injector


60


can be connected to fuel tank


13


, at a time, depending on the position of cam


19


in relation to pressure release switch


20


. However, fuel injector


60


is not connected to fuel tank


13


via main passage


29


until a pressure release electronic actuator


32


is activated by an electronic control module


33


. Pressure release electronic actuator


32


is attached to a pressure release electronic control valve


31


that is positioned remote from fuel injectors


60


. Pressure release electronic actuator


32


is preferably a two position control valve. Pressure release electronic control valve


31


is moved from a biased, closed position to an open position when pressure release electronic actuator


32


is activated. While pressure release electronic actuator


32


is preferably a solenoid, it should be appreciated that other actuators, such as a piezoelectric actuator, could be substituted.




Referring in addition to

FIG. 3

, there is shown a fuel injector


60


for use with fuel injection system


11


. Fuel injector


60


includes an injector body


61


that defines a nozzle outlet


99


, pressure release drain


62


and a high pressure fuel inlet


63


. Pressure release drain


62


, which is connected to drain passage


21


, can fluidly connect a needle control chamber


88


with fuel tank


13


, via a drain passage


70


, when pressure release electronic actuator


32


is activated and pressure release electronic control valve


31


and pressure release switch


20


are appropriately positioned. High pressure fuel inlet


63


fluidly connects fuel injector


60


to high pressure fuel rail


16


via high pressure fuel supply line


18


. A high pressure fuel passage


71


is defined by injector body


61


and includes a needle control passage


73


and a nozzle supply passage


93


which fluidly connect high pressure fuel inlet


63


to needle control chamber


88


and a nozzle chamber


97


respectively.




A direct control needle valve


90


is movably positioned in injector body


61


and includes a piston portion


91


and a needle portion


95


. Needle valve


90


is movable between a downward position in which nozzle outlet


99


is closed and an upward position in which nozzle outlet


99


is open. Needle valve


90


is biased toward its downward position by a biasing spring


94


. Needle valve


90


includes an opening hydraulic surface


96


that is exposed to fluid pressure within nozzle chamber


97


. A closing hydraulic surface


92


of needle valve


90


is included on piston portion


91


and is exposed to fluid pressure within needle control chamber


88


. A small diameter portion


79


included on needle control passage


73


limits the amount of high pressure fuel that can flow into needle control chamber


88


above piston portion


91


. Small diameter portion


79


is sized to communicate pressure while simultaneously limiting flow volume therethrough. Piston portion


91


and needle control chamber


88


are preferably sized such that a match clearance exits between piston portion


91


and injector body


61


. Preferably, this will prevent fuel from flowing around piston portion


91


toward biasing spring


94


. However, because some fuel could migrate downward toward biasing spring


94


during the movement of needle valve


90


, injector body


61


preferably defines a drain passage


72


that fluidly connects needle control chamber


88


to a drain


68


to vent any fuel that flows below piston portion


91


from fuel injector


60


.




When pressure release drain


62


is blocked from fluid communication with fuel tank


13


, high pressure fuel can act on both closing hydraulic surface


92


and opening hydraulic surface


96


. Closing hydraulic surface


92


and opening hydraulic surface


96


are preferably sized such that needle valve


90


will remain in its downward, biased position to close nozzle outlet


99


when pressure release drain


62


is blocked from fuel tank


13


When pressure release drain


62


is open to fuel tank


13


via drain passage


21


, high pressure fuel in needle control chamber


88


can flow out of fuel injector


60


through drain passage


70


. In other words, when pressure release drain


62


is open to fuel tank


13


, high pressure fuel rail


16


is fluidly connected to fuel tank


13


via needle control chamber


88


and drain passages


70


,


21


. However, recall that small diameter portion


79


of needle control passage


73


limits flow volume into needle control chamber


88


. When needle control chamber


88


is fluidly connected to fuel tank


13


, fuel pressure acting on opening hydraulic surface


96


is sufficient to overcome the downward bias exerted by biasing spring


94


and needle valve


90


can be moved toward its upward position to open nozzle outlet


99


.




Referring to

FIGS. 4 and 5

, there is shown a common rail fuel infection system


100


and fuel injector


160


according to an alternate embodiment of the present invention. Fuel injection system


100


and fuel injector


160


are similar to fuel injection system


11


and fuel injector


60


, respectively. Therefore, like reference numerals have been used to denote like components, and a repeated description of like components will not be provided. With minor modification, fuel injection system


100


could be incorporated into engine


10


to make a complete engine. In addition to the fuel injection system components shown and described in the

FIG. 1

embodiment, fuel injection system


100


includes a rate shaping electronic control valve


140


that is operably connected to electronic control module


33


and includes a rate shaping electronic actuator


142


, which is preferably a two position solenoid, but could be another electronic actuator, such as a piezoelectric actuator. Rate shaping electronic control valve


140


is preferably a two position control valve and is positioned remote from each fuel injector


160


fluidly between high pressure fuel rail


16


and a rate shaping fuel inlet


164


of each fuel injector


160


. When rate shaping electronic actuator


142


is activated by electronic control module


33


, rate shaping electronic control valve


140


is moved from a biased, closed position toward an open position. When rate shaping electronic control valve


140


is in its open position, rate shaping fluid inlet


164


is fluidly connected to high pressure fuel rail


16


via a high pressure fluid passage


143


. When rate shaping electronic control valve


140


is in this position, high pressure fuel can flow into a rate shaping fluid passageway


174


, defined by injector body


161


, via rate shaping fluid inlet


164


to change the position of a flow restriction valve member


180


that is movably positioned in injector body


161


.




High pressure fuel flowing into rate shaping fluid passageway


174


can act on flow restriction valve member


180


. Flow restriction valve member


180


is preferably any suitable valve member, such as a spool valve member, and includes a hydraulic surface


181


that is exposed to fluid pressure in rate shaping fluid passageway


174


. Flow restriction valve member


180


is movable between an upward, retracted position and a downward, advanced position and is biased toward its upward position by a biasing spring


183


. When flow restriction valve member


180


is in its retracted position, an annulus


182


included on flow restriction valve member


180


allows for unrestricted flow of fuel from high pressure fuel inlet


63


into nozzle supply passage


93


. When flow restriction valve member


180


is in its advanced position, annulus


182


partially blocks high pressure fuel inlet


63


from nozzle supply passage


93


, as illustrated in

FIG. 5

, to create a flow restriction


185


relative to nozzle outlet


99


.




Flow restriction


185


reduces the amount of high pressure fuel that is flowing into nozzle chamber


97


, thus reducing the fuel pressure exerted on opening hydraulic surface


96


. Therefore, when flow restriction valve member


180


is in its advanced position, fuel injector


160


will inject fuel at a lower pressure than it will when flow restriction valve member


180


is in its retracted position. While the size of annulus


182


can be varied to alter injection pressure when flow restriction valve member


180


is in its advanced position, it should be appreciated that annulus


182


could be sized so large that flow restriction


185


has little or no effect on the pressure of fuel flowing into nozzle chamber


97


. Similarly, annulus


182


could be sized small enough that fuel pressure in nozzle chamber


97


cannot be sustained above a valve opening pressure. Therefore, annulus


182


should be sized such that a valve opening pressure can be sustained when flow restriction


185


is present in nozzle supply passage


93


, while still achieving the desired, lower injection pressure.




Note that unlike pressure release electronic control valve


31


, rate shaping electronic control valve


140


is not prevented from affecting conditions within all fuel injectors


160


. This is because rate shaping electronic control valve


140


is not separated from the injectors by a switch, such as pressure release switch


20


. It should be appreciated that this should not effect fuel injection, or which fuel injector is injecting fuel, because pressure introduced into non-injecting fuel injectors


160


as a result of the position of rate shaping electronic control valve


140


merely changes the position of flow restriction valve member


180


. In other words, the pressure forces acting on closing hydraulic surface


92


and opening hydraulic surface


96


are unaffected by the movement of rate shaping electronic control valve


140


. Therefore, movement of rate shaping electronic control valve


140


to its open position should not cause a non-injecting fuel injector to inject fuel at an undesirable time. It should be appreciated, however, that a switch could be included to allow rate shaping electronic control valve


140


to connect only the injecting fuel injector


160


to high pressure fuel rail


16


during the injection event without departing from the spirit of the present invention.




Referring to

FIGS. 6 and 7

, there is shown a common rail fuel injection system


200


and fuel injector


260


according to yet another embodiment of the present invention. This embodiment of the present invention is the preferred mode for carrying out the invention, as it provides an even greater control over the injection event than the previous embodiments. Fuel injection system


200


is similar to fuel injection systems


11


and


100


and fuel injector


260


shares several common features with fuel injectors


60


and


160


. Therefore, like numerals have been used to denote like components. With minor modification, fuel injection system


200


could be incorporated into engine


10


to create a complete engine. Because fuel injection system


200


and fuel injector


260


share common features with the previously disclosed embodiments, a repeated description of like components has not been provided.




In addition to the features shown and described for fuel injection system


100


, fuel injection system


200


includes a pressure build-up switch


250


which is positioned fluidly between the rail outlet


17


of high pressure fuel rail


16


and each high pressure fuel inlet


265


of the fuel injectors


260


. Pressure build-up switch


250


allows selective fluid communication between nozzle chamber


88


of a fuel injector


260


and high pressure fuel rail


16


via high pressure supply lines


253


. Pressure build-up switch


250


is preferably similar to pressure release switch


20


in both form and function. However, while pressure release switch


20


can connect one fuel injector


260


to fuel tank


13


via drain passage


21


and main passage


29


to begin an injection event, pressure build-up switch


250


can connect a high pressure fuel inlet


265


of one fuel injector


260


to high pressure fuel rail


16


to end an injection event. A pressure build-up electronic control valve


251


controls fuel flow between high pressure fuel rail


16


and fuel injectors


260


via pressure build-up switch


250


. Pressure build-up electronic control valve


251


is positioned remote from fuel injectors


260


and includes a pressure build-up electronic actuator


252


. Pressure build-up electronic control valve


251


is preferably a two position control valve and is biased to a closed position. When pressure build-up electronic actuator


252


is activated by electronic control module


33


, pressure build-up electronic control valve


251


is moved to an open position. As with pressure release electronic actuator


32


and rate shaping electronic actuator


142


, pressure build-up electronic actuator


252


is preferably a solenoid, however, other electronic actuators, such as a piezoelectric actuator, could be substituted.




Referring in addition to

FIG. 7

, unlike fuel injectors


60


and


160


, high pressure fuel passage


71


of fuel injector


260


does not include branch passages that open into both needle control chamber


88


and nozzle chamber


97


. Instead, high pressure fuel passage


71


includes only nozzle supply passage


93


which opens into nozzle chamber


97


. Injector body


261


defines a high pressure fuel passage


276


that fluidly connects high pressure fuel rail


16


to needle control chamber


88


, via high pressure fuel inlet


265


. Because high pressure fuel is entering needle control chamber


88


and nozzle chamber


97


from separate fuel inlets, it is possible to close needle control chamber


88


from high pressure fuel rail


16


without affecting fuel flow to nozzle chamber


97


or otherwise affecting injector performance. Recall that with the fuel injectors


60


,


160


of the previous embodiments, needle control chamber


88


was continuously open to high pressure fuel rail


16


via high pressure fuel passage


71


. However, in this embodiment of the present invention, pressure build-up switch


250


and pressure build-up electronic control valve


251


can be positioned and activated such that the needle control chamber


88


of a particular fuel injector


260


is closed from high pressure fuel rail


16


prior to opening needle control chamber


88


to fuel tank


13


.




Returning to fuel injector


260


, a flow restriction valve member


280


is movably positioned in injector body


261


and includes an internal passage


282


that can introduce a flow restriction


285


into nozzle supply passage


93


. Flow restriction valve member


280


is preferably any suitable valve member, such as a spool valve member and is biased to fully open high pressure fuel passage


71


to nozzle supply passage


93


by a biasing spring


283


. When rate shaping inlet


164


is fluidly connected to high pressure fuel rail


16


, flow restriction valve member


280


moves against the bias of spring


283


to a position in which flow restriction


285


is introduced into nozzle supply passage


93


. While flow restriction valve member


280


is preferably sized to prevent fluid flow into the area surrounding biasing spring


283


, injector body


261


also defines a drain


267


and a drain passage


277


that can vent any fuel that has migrated into the area surrounding biasing spring


283


from fuel injector


260


. Additionally, it should be appreciated that internal passage


282


is preferably sized and positioned such that a valve opening pressure can be reached in nozzle chamber


97


when flow restriction


285


is present in nozzle supply passage


93


while allowing for the desired reduction in injection pressure.




INDUSTRIAL APPLICABILITY




Referring to the

FIGS. 1-3

embodiment of the present invention and in addition to the

FIGS. 8



a-f


graphs of pressure release switch position, pressure release actuator current, pressure release valve position, net force on the needle, needle position and injection rate, respectively, versus time. Prior to an injection event, high pressure in needle control chamber


88


prevails and high pressure fuel is acting on both opening hydraulic surface


96


and closing hydraulic surface


92


of needle valve


90


such that needle valve


90


is in a downward position closing nozzle outlet


99


, as illustrated in

FIG. 8



d


. Cam


19


rotates such that a first valve member


23


moves over contact platform


22


to allow pressure release switch


20


to enable a first fuel injector


60


to be fluidly connected to fuel tank


13


via drain passage


21


, as illustrated at


1


in

FIG. 8



a


. Fuel injection from the first fuel injector


60


begins when pressure release electronic actuator


32


is activated by electronic control module


33


to move pressure release electronic control valve


31


to its open position as illustrated at


3


and


8


in

FIGS. 8



b-c


, respectively.




When pressure release electronic actuator


32


is activated, the fuel injector


60


enabled by pressure release switch


20


becomes fluidly connected to fuel tank


13


via pressure release drain


62


and drain passage


21


. However, pressure release electronic actuator


32


need not pull current for the entire injection event, and instead can be reduced to a hold level, as illustrated at


4


in

FIG. 8



b


. High pressure fuel within needle control chamber


88


can flow out of fuel injector


60


via drain passage


70


, thus reducing the pressure acting on closing hydraulic surface


92


of needle valve


90


, as illustrated at


12


in

FIG. 5



d


. Because high pressure fuel is still flowing into nozzle chamber


97


, fuel pressure acting on opening hydraulic surface


96


exceeds a valve opening pressure and needle valve


90


moves to its upward position opening nozzle outlet


99


and allowing fuel to spray into combustion chamber


19


, as illustrated at


16


in

FIG. 8



e


. The corresponding increase in injection rate toward the maximum is illustrated at


20


in

FIG. 8



f.






As illustrated in

FIG. 8

, it is possible to create a split injection, such as when the engine is operating under idle operating conditions. Note that the injection characteristics for rated operating conditions have been graphed as solid lines while those for idle operating conditions have been graphed as dashed line. For instance, when current to pressure release electronic actuator


32


is ended, pressure release electronic control valve


31


closes briefly, as illustrated at


6


and


10


in

FIGS. 8



b-c


, respectively. When pressure release electronic control valve


31


is closed, pressure can increase in needle control chamber


88


to a sufficient level to close needle valve


90


. When pressure release electronic actuator


32


is re-activated (at


7


in FIG.


8




b


), pressure release electronic control valve


31


is reopened (at


11


in

FIG. 8



c


). Pressure in needle control chamber


88


can again be vented, and needle valve


90


can reopen due to the fuel force exerted on opening hydraulic surface


96


. The net force on the needle valve and this movement of the needle valve during the injection event has been illustrated at


14


and


15


, and


18


and


19


in

FIGS. 8



d-e


, respectively. In addition, the injection rate, and in particular the split injection created by the movement of needle valve


90


has been graphed at


22


and


23


in

FIG. 8



f.






The injection event of a particular fuel injector


60


is ended when pressure release electronic actuator


32


is deactivated, thus blocking needle control chamber


88


from communication with fuel tank


13


(at


5


in

FIG. 8



b


). Pressure release electronic control valve


31


is now moved to its closed position, as illustrated at


9


in

FIG. 8



c


. While high pressure fuel can no longer flow from needle control chamber


88


, needle control chamber


88


is still exposed to high pressure in high pressure fuel rail


16


via first branch passage


73


and high pressure fuel inlet


63


. Pressure acting on closing hydraulic surface


92


of needle valve


90


once again begins to build and subsequently, and the high fuel pressure acting on opening hydraulic surface


96


is no longer sufficient to hold needle valve


90


in its upward, open position. Needle valve


90


is returned to its downward position under the action of biasing spring


94


to close nozzle outlet


99


and the injection event is ended, as illustrated at


13


,


17


and


21


in

FIGS. 8



d-f.






After needle valve


90


returns to its downward position to end the injection event for this fuel injector, fuel injection system


11


prepares a subsequent fuel injector


60


for fuel injection. The corresponding valve member


23


within pressure release switch


20


moves off of contact platform


22


, as cam


19


continues to rotate, to prevent pressure release electronic control valve


31


from reopening needle control chamber


88


of that particular fuel injector


60


to fuel tank


13


(at


2


in

FIG. 8



a


). Cam


19


continues to rotate and a second valve member


23


moves over contact surface


22


to enable the next fuel injector


60


to be fluidly connected to fuel tank


13


via needle control chamber


88


and drain passage


21


. It should be appreciated that because only one fuel injector


60


is capable of being fluidly connected to fuel tank


13


via drain passage


21


, fuel injection system


11


will have no more than one fuel injector


60


injecting fuel into combustion chamber


19


at any given time.




Referring now to the

FIGS. 4-5

embodiment of the present invention and in addition to the graphs of pressure release switch position, pressure release actuator current, pressure release valve position and net force of needle valve


90


, respectively, versus time of

FIGS. 9



a-h


. Prior to an injection event, high pressure in needle control chamber


88


prevails and high pressure fuel is acting on closing hydraulic surface


92


and opening hydraulic surface


96


, such that needle valve


90


is in its downward, closed position, as illustrated in

FIG. 9



d


. Rate shaping electronic actuator


142


is preferably de-activated such that rate shaping inlet


164


is not connected to high pressure fuel rail


16


, as illustrated in

FIG. 9



g


. Low pressure is acting on hydraulic surface


181


and flow restriction valve member


180


is positioned in its upward, biased position, allowing unrestricted flow of fuel from high pressure fuel passage


71


to nozzle supply passage


93


, as illustrated in

FIG. 9



h


. Cam


19


is rotating at one half the speed of the engine and valve member


23


moves onto contact surface


22


to allow pressure release switch


20


to enable a first fuel injector


60


to be fluidly connected to fuel tank


13


at


1


in

FIG. 9



a


).




Prior to activation of pressure release electronic actuator


32


, rate shaping electronic actuator


142


is preferably activated, and rate shaping electronic control valve


140


moves to its open position, as illustrated at


17


and


20


, respectively in

FIGS. 9



g-h


. Rate shaping inlet


164


is now open to nigh pressure fuel rail


16


, via high pressure fuel passage


143


exposing hydraulic surface


181


of flow restriction valve member


180


to high pressure fuel. Flow restriction valve member


180


then moves toward its advanced position, causing a flow restriction


185


between high pressure fuel passage


71


and nozzle supply passage


93


. Pressure release electronic actuator


32


is now activated to move pressure release electronic control valve


31


to its open position to allow the injection event to begin, as illustrated at


3


and


6


in

FIGS. 9



b-e


. Corresponding movement of needle valve


90


toward its open position, increase in flow area to nozzle outlet


99


and initial injection rate are illustrated at


8


,


11


and


14


in

FIGS. 9



d-f.






Operation of fuel injection system


100


, and fuel injector


160


, would be identical to that of fuel injection system


11


and fuel injector


60


if rate shaping electronic actuator


142


was not activated during fuel injection. As with pressure release electronic actuator


32


, rate shaping electronic actuator


142


need not pull current for the duration of the injection event, and can instead be reduced to a hold level as illustrated at


4


and


1


) in

FIGS. 9



b


and


9




g


. At the desired point during the injection event, rate shaping electronic actuator


142


is deactivated and rate shaping electronic control valve


140


moves to its closed position to end fluid communication between rate shaping inlet


164


and high pressure fuel rail


16


(at


19


and


21


in

FIGS. 9



9-h


). Flow restriction valve member


180


can now return to its biased, retracted position under the action of biasing spring


183


. As flow restriction valve member


180


retracts, annulus


182


retracts in a corresponding manner such that fuel flow between high pressure fuel passageway


71


and nozzle supply passage


93


is unrestricted. This unrestricted flow into nozzle supply passage


93


increases the amount of fuel flowing into nozzle chamber


97


, therefore increasing the pressure being exerted on opening hydraulic surface


96


and raising the pressure of fuel being injected by fuel injector


160


(at


9


,


12


and


15


in

FIGS. 9



d-f


). By varying the timing of rate shaping electronic actuator


142


, it should be appreciated that a number of rate shapes, such as boot shapes, can be accomplished with fuel injection system


100


. However, it should also be appreciated that at certain operating conditions it may be undesirable to have front end rate shaping. In these instances, rate shaping electronic actuator need not be activated, such that rate shaping electronic control valve remains in its closed position throughout the injection event.




As described for the

FIGS. 1-3

embodiment of the present invention, fuel injection from fuel injector


160


is ended when current to pressure release electronic actuator


32


is ended and pressure release electronic control valve


31


returns to its closed position, as illustrated at


5


and


7


, respectively, in

FIGS. 9



b-c


. Needle control chamber


88


is now blocked from fluid communication with fuel tank


13


and pressure within needle control chamber


88


acting on closing hydraulic surface


92


can rise. Because of the size differential between closing hydraulic surface


92


and opening hydraulic surface


96


, the high pressure acting on opening hydraulic surface


96


is no longer sufficient to hold needle valve


90


in its upward position, and needle valve


90


returns to its downward position under the action of biasing spring


94


(at


10


in

FIG. 9



d


). Needle valve


90


is moved toward its downward movement by the increased pressure acting on closing hydraulic surface


92


. The corresponding decrease in flow area to nozzle outlet


99


and in injection rate has been illustrated at


13


and


16


in

FIGS. 9



e-f


, respectively. As with fuel injection system


11


, after needle valve


90


returns to its downward position to end the injection event for this fuel injector


160


, fuel injection system


100


prepares a subsequent fuel injector


160


for fuel injection. Cam


19


continues to rotate and first valve member


23


moves off of contact surface


22


to close pressure release switch


20


from enabling this fuel injector


160


from being fluidly connected to fuel tank


13


via needle control chamber


88


and drain passage


21


, as illustrated at


2


in

FIG. 9



a


. A second valve member


23


moves over contact surface


22


to enable the needle control chamber of the next fuel injector


160


to be fluidly connected to fuel tank


13


.




Referring to the

FIGS. 6-7

embodiment of the present invention and in addition to the

FIGS. 10



a-i


graphs of pressure release switch position, pressure release actuator current, net force on the needle, flow area to the nozzle, injection rate, rate shaping valve position, pressure build-up actuator current, pressure build-up valve position and pressure build-up switch position, respectively, versus time. Prior to an injection event, high pressure in needle control chamber


88


prevails, high pressure inlet


63


is open to high pressure fuel rail


16


to expose opening hydraulic surface


96


to high pressure and residual high pressure is acting on closing hydraulic surface


92


such that needle valve


90


is in a downward position closing nozzle outlet


99


. Rate shaping inlet


164


is preferably not connected to high pressure fuel rail


16


, such that low pressure acting on hydraulic surface


281


allows flow restriction valve member


280


to remain in its biased, retracted position, allowing an unrestricted flow path between high pressure fuel passage


71


and nozzle supply passage


93


. Just prior to the initiation of an injection event, pressure build-up switch


250


enables the high pressure fuel inlet


265


of a first fuel injector


260


to be fluidly connected to high pressure fuel rail


16


, as illustrated at


20


in FIG.


101


. However, because pressure build-up electronic control valve


251


remains in its closed position, as illustrated in

FIG. 10



h


, high pressure fuel inlet


265


is not opened to high pressure fuel rail


16


at this time. Cam


19


now rotates such that pressure release switch


20


enables a first fuel injector


260


to be fluidly connected to fuel tank


13


, as illustrated at


1


in

FIG. 10



a.






Prior to activation of pressure release electronic control valve


31


, rate shaping electronic actuator


142


is preferably activated to move rate shaping electronic control valve


140


to an open position to fluidly connect rate shaping inlet


164


with high pressure fuel rail


16


(at


14


in

FIG. 10



f


). Recall that at certain operating conditions, front end rate shaping may not be desirable. Therefore, it should be appreciated that fuel injection can take place if rate shaping electronic control valve


140


remains in its closed position. With high pressure now acting on hydraulic surface


281


, flow restriction valve member


280


can move toward its advanced position against the action of biasing spring


283


. The corresponding movement of internal passage


282


creates a flow restriction


285


in nozzle supply passage


93


that will create a lower injection pressure at the beginning of the injection event. The injection event is initiated by the brief activation of pressure release electronic actuator


32


, as illustrated at


3


in

FIG. 10



b


, which fluidly connects pressure release drain


62


to fuel tank


13


. It should be appreciated that pressure release electronic actuator


32


does not need to receive current for the duration of the injection event, as it did for fuel injection systems


11


and


100


, because it only takes a short amount of time to vent the residual pressure in needle control chamber


88


. Also, only a small fixed amount of fuel must be displaced from needle control chamber


88


for fuel injection to proceed. Therefore, pressure release electronic control valve


31


need only be moved to its open position for a relatively short amount of time. Recall that in fuel injection systems


11


and


100


, the needle control chambers


88


of the fuel injectors


60


,


160


were continuously open to high pressure fuel rail


16


, and as a result, pressure release electronic control valve


31


remained in an open position to allow fuel pressure above needle valve


90


to be vented for the duration of the injection event.




Once residual pressure within needle control chamber


88


has been vented, the high fuel pressure acting on opening hydraulic surface


96


can exceed a valve opening pressure defined by biasing spring


94


. Needle valve


90


then moves to its upward, open position to commence fuel spray from nozzle outlet


99


, as illustrated at


5


in

FIG. 10



c


. Note, however, that flow area to nozzle outlet


90


increases only to a restricted amount due to flow restriction


185


, as illustrated at


8


in

FIG. 10



d


. The corresponding initial injection rate has been illustrated at


11


in

FIG. 10



e


. Pressure release electronic actuator


142


is then deactivated (at


4


in FIG.


10


(


b


)) to return electronic control valve


31


to its closed position to block needle control chamber


88


from fluid communication with fuel tank


13


. Operation of fuel injector


260


and fuel injection system


200


progresses in a similar manner as that described for fuel injector


160


and fuel injection system


100


, until just prior to the end of the injection event. At that time, pressure build-up electronic actuator


252


is activated briefly to move pressure build-up electronic control valve


251


to its open position, as illustrated at


16


and


18


, respectively, in

FIGS. 10



g-h


. High pressure fuel inlet


265


is once again fluidly connected to high pressure fuel rail


16


and high pressure fuel flows into needle control chamber


88


via high pressure fuel supply line


253


. Because closing hydraulic surface


92


is again exposed to high pressure within nozzle chamber


88


, needle valve


90


is moved to its downward, closed position to close nozzle outlet


99


and end the injection event, as illustrated at


7


in

FIG. 10



c


. The corresponding decrease in flow area to nozzle outlet


99


and injection rate has been illustrated at


10


and


13


, respectively, in

FIGS. 10



d-e.






After needle valve


90


moves to its downward position to end fuel injection from fuel injector


250


, fuel injection system


200


prepares a subsequent fuel injector


260


to begin injection. Cam


19


, which has been rotating throughout the previous injection event, rotates such that valve member


23


within pressure release switch


20


, corresponding to the previously injecting fuel injector


260


, moves off contact platform


22


, and valve member


23


corresponding to the fuel injector that is about to inject moves on to platform


22


(at


2


in

FIG. 10



a


). Preferably, at about the same time, the contact platform within pressure build-up switch


250


is rotated such that the valve member


23


corresponding to the previously injecting fuel injector


260


returns to its biased position, and the valve member


23


for the fuel injector


260


about to inject moves onto the contact platform (at


21


in

FIG. 10



i


). The subsequent fuel injector


260


can now inject fuel in the manner described above.




Referring now to

FIG. 11

, total fuel consumption for fuel injection systems


11


,


100


and


200


have been graphed versus time for both idle operating conditions, at


1


, and for rated operating conditions, at


2


. Note that the total amount of fuel consumed by fuel injection system


200


, graphed as a solid line, is substantially less than that used by fuel injection systems


11


and


100


, where these systems are represented by dashed and dotted lines, respectively. This result should be expected because pressure build-up switch


250


and pressure build-up electronic control valve


251


allow each fuel injector to be blocked from fluid communication with high pressure rail


16


prior to being fluidly connected to fuel tank


13


. Therefore, in fuel injection system


200


, high pressure fuel rail


16


is preferably not fluidly connected to fuel tank


13


at any time during the injection event. It should be appreciated that the total fuel consumed by fuel injection system


200


is still higher than the total fuel injected because an amount of fuel from high pressure fuel rail


16


is not injected, but instead acts on needle valve


90


within needle control chamber


88


.




The fuel injection systems of the present invention have a number of advantages over prior art systems. Because the electronic control valves used in the present invention are located remote from the individual fuel injectors, the number of electronic control valves used in the fuel injection system can be reduced. For instance, because nozzle chamber


97


is always fluidly connected to high pressure fuel rail


16


, injection can begin at full pressure. This is unlike those systems where the needle valve opens at a valve opening pressure that is well below a maximum injection pressure. With regard to fuel injection system


11


, only one electronic control valve is used to control the injection of each fuel injector, instead of utilization of as many electronic control valves as the number of fuel injectors. In addition, fuel injection systems


100


and


200


allow for flexible rate shaping of the injection event. Further, because fuel injection system


200


has the ability to block fluid communication between the high pressure fuel rail and the fuel drain during an injection event, fuel injection system


200


consumes, and therefore wastes, less fuel than prior art fuel injection systems of this nature.




It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present invention in any way. For instance, while the present invention does not include a switch between the pressure build-up electronic control valve and the fuel injectors, it should be appreciated that such a switch could be utilized. Further, while the fuel injection systems of the present invention include electronic control valves that are preferably solenoids, it should be appreciated that other suitable actuators, such as a piezoelectric actuator, could be substituted. 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.



Claims
  • 1. An engine comprising:an engine housing; a high pressure fuel rail; a low pressure fuel drain; a fuel injection system including a plurality of fuel injectors positioned in said engine housing and fluidly connected to said fuel rail; each of said plurality of fuel injectors including an injector body defining a nozzle outlet and a nozzle supply passage, and including a needle valve member movably positioned in said injector body adjacent said nozzle outlet; a fluid switch having a plurality of positions; an electronically controlled valve being positioned remote from said plurality of fuel injectors and fluidly between said fluid switch and said fuel drain; and a different one of said plurality of fuel injectors being fluidly connected to said electronically controlled valve at each of said plurality of positions.
  • 2. The engine of claim 1 wherein said electronically controlled valve is a two position valve.
  • 3. The engine of claim 1 wherein said injector body defines a needle control chamber; andsaid needle valve member includes a closing hydraulic surface exposed to fluid pressure in said needle control chamber.
  • 4. The engine of claim 1 wherein said electronically controlled valve is a first electronically controlled valve and said fuel injection system also includes a second electronically controlled valve positioned remote from said plurality of fuel injectors; andsaid second electronically controlled valve has a closed position in which said nozzle supply passage is relatively unrestricted and an open position in which said nozzle supply passage is relatively restricted.
  • 5. The engine of claim 1 wherein each of said plurality of fuel injectors further includes a flow restriction valve member; andsaid flow restriction valve member is movable between a first position in which said nozzle supply passage is relatively restricted and a second position in which said nozzle supply passage is relatively unrestricted.
  • 6. The engine of claim 1 wherein said high pressure rail is fluidly connected to said low pressure fuel drain via said plurality of fuel injectors for a portion of an injection event.
  • 7. The engine of claim 1 wherein said fluid switch is a first fluid switch and said fuel injection system further includes a second fluid switch; andsaid second fluid switch is positioned fluidly between said high pressure rail and said plurality of fuel injectors.
  • 8. The engine of claim 7 wherein said electronically controlled valve is a first electronically controlled valve and said fuel injection system also includes a second electronically controlled valve and a third electronically controlled valve;said second fluid switch having a plurality of positions; and a different one of said plurality of fuel injectors being fluidly connected to said third electronically controlled valve at each of said plurality of positions of said second fluid switch.
  • 9. A fuel injection system comprising:a high pressure fuel rail; a low pressure fuel drain; a plurality of fuel injectors; each of said plurality of fuel injectors including an injector body defining a needle control chamber, nozzle outlet, at least one high pressure fluid inlet, at least one low pressure fluid drain, at least one fluid passageway and a nozzle supply passage, and including a direct control needle valve member movably positioned in said injector body adjacent said nozzle outlet; said direct control needle valve member including a closing hydraulic surface exposed to fluid pressure in said needle control chamber; a first of said at least one fluid passageways being fluidly connected to said high pressure fuel rail; a second of said at least one fluid passageways being fluidly connected to said low pressure fuel drain; a fluid switch having a plurality of positions; an electronically controlled valve being positioned remote from said plurality of fuel injectors fluidly between said fluid switch and said fuel drain; and a different one of said plurality of fuel injectors being fluidly connected to said electronically controlled valve at each of said plurality of positions.
  • 10. The fuel injection system of claim 9 wherein said high pressure rail is fluidly connected to said low pressure fuel drain via said plurality of fuel injectors for a portion of an injection event.
  • 11. The fuel injection system of claim 9 wherein said electronically controlled valve is a first electronically controlled valve and said fuel injection system further includes a second electronically controlled valve positioned remote from said plurality of fuel injectors;each of said plurality of fuel injectors further includes a flow restriction valve member; said second electronically controlled valve is fluidly positioned between a source of fluid and said flow restriction valve member; said second electronically controlled valve has a first position in which said flow restriction valve member is in an advanced position in which said nozzle supply passage is relatively restricted; and said second electronically controlled valve has a second position in which said flow restriction valve member is in a retracted position in which said nozzle supply passage is relatively unrestricted.
  • 12. The fuel injection system of claim 11 wherein said fluid switch is a first fluid switch and said fuel injection system further includes a second fluid switch; andsaid second fluid switch is positioned fluidly between said high pressure rail and said needle control chambers of each of said plurality of fuel injectors.
  • 13. The fuel injection system of claim 12 further comprising a third electronically controlled valve positioned remote from said plurality of fuel injectors between said second fluid switch and said needle control chambers of each of said plurality of fuel injectors;said second fluid switch having a plurality of positions; and a different one of said plurality of fuel injectors being fluidly connected to said third electronically controlled valve at each of said plurality of positions of said second fluid switch.
  • 14. The fuel injection system of claim 13 wherein an opening hydraulic surface of said direct control needle valve member is exposed to fluid pressure in a nozzle chamber defined at least in part by said injector body; andsaid injector body defines a first fluid inlet that fluidly connects said high pressure rail to said needle control chamber and a second fluid inlet that fluidly connects said nozzle chamber to said high pressure rail.
  • 15. The fuel injection system of claim 14 wherein said third electronically controlled valve has a first position in which said high pressure rail is fluidly connected to said needle control chamber and a second position in which said high pressure rail is blocked from fluid communication with said needle control chamber.
  • 16. A method of injecting fuel comprising:providing an engine including a fuel injection system that includes a high pressure fuel rail, a low pressure fuel drain, a plurality of fuel injectors that each include an injector body that defines a needle control chamber, a fluid switch having a plurality of positions and an electronically controlled valve positioned remote from said plurality of fuel injectors between said fluid switch and said low pressure fuel drain; enabling one of said plurality of fuel injectors to be fluidly connected to said electronically controlled valve, in part by moving said fluid switch to a first position; moving said electronically controlled valve to an open position opening said needle control chamber of said one fuel injector to fluid communication with said low pressure fuel drain; injecting an amount of fuel from said one fuel injector; moving said electronically controlled valve to a closed position blocking said needle control chamber of said one fuel injector from fluid communication with said low pressure fuel drain; and preventing said one fuel injector from being open to said electronically controlled valve and enabling an other of said plurality of fuel injectors to be fluidly connected to said electronically controlled valve, in part by moving said fluid switch to a second position.
  • 17. The method of claim 16 wherein a flow restriction control valve member is movably mounted in each of said plurality of fuel injectors, said injector body of each of said plurality of fuel injectors defines a nozzle outlet and a nozzle supply passage, said electronic control valve is a first electronic control valve and said fuel injection system further includes a second electronic control valve positioned remote from said plurality of fuel injectors fluidly between said plurality of fuel injectors and said high pressure fuel rail; andfurther including the step of restricting fuel flow to said nozzle outlet by moving said flow restriction control valve member to a first position in which said nozzle supply passage is restricted relative to said nozzle outlet, by moving said second electronic control valve to an open position prior to said step of injecting fuel.
  • 18. The method of claim 17 wherein said step of injecting fuel includes moving said flow restriction control valve member to a second position in which said nozzle supply passage is relatively unrestricted by moving said second electronic control valve to a closed position.
  • 19. The method of claim 18 wherein said fluid switch is a first fluid switch and said fuel injection system further includes a second fluid switch having a plurality of positions; andfurther including the step of enabling said needle control chamber of said one fuel injector to be fluidly connected to said high pressure fuel rail, in part by moving said second fluid switch to a first position, prior to the step of injecting fuel.
  • 20. The method of claim 19 wherein said fuel injection system further includes a third electronic control valve positioned remote from said plurality of fuel injectors between said second fluid switch and said high pressure fuel rail;further including the step of moving said third electronic control valve to an open position opening said needle control chamber of said one fuel injector to fluid communication with said high pressure fuel rail after sand step of moving said first electronic control valve to a closed position; and moving said third electronic control valve to a closed position blocking said needle control chamber from said high pressure fuel rail.
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Entry
Heavy Duty Diesel Engines—The Potential of Injection Rate Shaping for Optimizing Emissions and Fuel Consumption, presented by Messrs. Bernd Mahr, Manfred Dürnholz, Wilhelm Polach, and Hermann Grieshaber, Robert Bosch GmbH, Stuttgart, Germany, at the 21st International Engine Symposium, May 4-5, 2000, Vienna, Austria.