Reverse flow valve for fuel injectors

Information

  • Patent Grant
  • 6655603
  • Patent Number
    6,655,603
  • Date Filed
    Thursday, April 18, 2002
    22 years ago
  • Date Issued
    Tuesday, December 2, 2003
    21 years ago
Abstract
A reverse flow valve member is positioned within an injector body of a fuel injector and is movable between a closed position and an open position. When the reverse flow valve member is in its closed position, an upper portion of a nozzle supply passage is blocked from fluid communication with a lower portion of the nozzle supply passage. A compressed spring biases the reverse flow valve member to its closed position. When the reverse flow valve member is in its open position, the fuel pressurization chamber is fluidly connected to the lower portion of the nozzle supply passage. The present invention limits gas ingestion due to tip leakage, and allows an injector with trapped gas to prime itself.
Description




TECHNICAL FIELD




This invention relates generally to fuel injectors, and more specifically to reverse flow check valves within fuel injectors.




BACKGROUND




Occasionally, an injector nozzle of a fuel injector will become leaky, and after an injection event, allow hot combustion gases from the engine cylinder to leak past the nozzle outlet and travel upwards into the nozzle supply passage of the fuel injector. If the gases are permitted to continue to travel upwards and reach the fuel pressurization chamber, the fuel injector will inject less than a predicted amount of fuel, and can eventually be unable to pressurize fuel and inject it into the engine cylinder.




Typically, gases have been blocked from the fuel pressurization chamber by reverse flow check valve assemblies having a variety of structures. One example of such a check valve assembly is shown in co-owned U.S. Pat. No. 5,287,838 issued to Wells on Feb. 22, 1994. The function of the check valve assembly is to permit communication of high pressure fuel from the fuel pressurization chamber to the nozzle outlet of the fuel injector during an injection phase, but to prevent communication (i.e., reverse flow) of engine cylinder combustion gas from the nozzle to the fuel pressurization chamber at the end of an injection event and during a non-injection phase if the nozzle of the fuel injector becomes leaky.




Referring to

FIG. 1

, there is shown a partial sectioned side diagrammatic view of a fuel injector


10


according to the above identified patent. The fuel injector


10


consists of an injector body


11


that includes a barrel


33


separated from a stop component


42


by a relatively thin plate


50


. A plunger


13


is movably positioned along a centerline


12


within the injector body


11


. The plunger


13


, the barrel


33


and the plate


50


define a fuel pressurization chamber


14


that is fluidly connected to a fuel tank (not shown) via a fuel supply line


30


. When the plunger


13


is driven downward, it advances along the centerline


12


in order to pressurize fuel delivered from the fuel tank (not shown) via the fuel supply line


30


. A check valve


32


is positioned within the fuel supply line


30


. The check valve


32


is in its closed position in which it blocks fluid communication between the fuel pressurization chamber


14


and the fuel supply line


30


when the plunger


13


is advancing downward and increasing the pressure within the fuel pressurization chamber


14


. When the plunger


13


is returning to its upward position, the pressure within the pressurization chamber


14


decreases such that the check valve


32


opens and low pressure fuel within the fuel supply line


30


can flow past the check valve


32


and into the fuel pressurization chamber


14


.




The injector body


11


defines a nozzle supply passage


15


, a nozzle outlet


17


, and a guide bore


54


. A needle valve is positioned in the injector body


11


and has a needle valve member


20


that is movable between a first position, in which the nozzle outlet


17


is open, and a second position, in which the nozzle outlet


17


is closed. The needle valve member


20


has an opening hydraulic surface


21


that is exposed to fluid pressure within the nozzle supply passage


15


, but is biased toward a closed position by a compressed spring


22


. When the needle valve member


20


is in its open position, a stop surface of the needle valve member


20


is in contact with the stop component


42


, and the nozzle outlet


17


is opened to allow pressurized fuel to be injected into the engine cylinder (not shown).




The fuel pressurization chamber


14


is fluidly connected to the nozzle outlet


17


via the nozzle supply passage


15


, which includes the guide bore


54


. Positioned within the guide bore


54


, there is a reverse flow check valve assembly that includes a reverse flow check


52


, the plate


50


, and the stop component


42


. The reverse flow check


52


is preferably a flat circular plate and defines a flow passage


53


. The flow passage


53


is preferably cylindrical and centrally positioned within the reverse flow check


52


and is fluidly connected to the nozzle supply passage


15


. The plate


50


, which is preferably flat, is positioned between the barrel


33


and the stop component


42


and defines a pair of kidney-shaped or crescent-shaped holes


51


, which are fluidly connected to the fuel pressurization chamber


14


. The flow passage


53


of the reverse flow check


52


is radially inwardly spaced from the kidney holes


51


of the plate


50


and is arranged so that the nozzle supply passage


15


is blocked from the pressurization chamber


14


when the reverse flow check


52


and the plate


50


are in contact. The reverse flow check


52


is movable between an open position and closed position. When in its open position, as shown, the reverse flow check


52


is in contact with the stop component


42


, and the fuel pressurization chamber


14


is fluidly connected to the nozzle supply passage


15


via the kidney holes


51


of the plate


50


and the flow passage


53


of the reverse flow check


52


.




Prior to an injection event, the plunger


13


is driven downward by a hydraulic intensifier piston or a tappet along a centerline


12


of the fuel injector


10


toward its downward position. This greatly increases the pressure within the upper portion of the nozzle supply passage


15


which includes the fuel pressurization chamber


14


and the lower portion of the nozzle supply passage


15


. The increased pressure within the fuel pressurization chamber


14


will also close the check valve


32


, blocking fluid communication between the fuel pressurization chamber


14


and the fuel tank (not shown) via the fuel supply line


30


. The reverse flow check


52


will be in its first, or open, position, and in contact with the stop component


42


. Thus, the pressurized fuel will flow from the fuel pressurization chamber


14


through kidney holes


51


within the plate


50


and through the flow passage


53


of the reverse flow check


52


to the lower portion of the nozzle supply passage


15


. Thus, during an injection event, the fuel pressurization chamber


14


is fluid connected to the lower portion of the nozzle supply passage


15


.




Shortly before the desired amount of pressurized fuel is injected into the engine cylinder via the nozzle outlet


17


of the fuel injector


10


, the plunger


13


will stop moving downward, resulting in a fuel pressure drop to below valve closing pressure. This causes the needle valve member


20


to move to its closed position under the action of spring


22


. Towards the end of the movement of the needle valve member


20


to its closed position, there is a reverse flow of pressurized fuel within the lower portion of the nozzle supply passage


15


. The reverse flow of fuel will lift the reverse flow check


52


out of contact with the stop component


42


. The reverse flow check


52


will be lifted upward until it is in contact with the plate


50


and, thus, in its second, or closed, position. Due to the positioning and placement of the kidney holes


51


of the plate


50


and the flow passage


53


of the reverse flow check


52


, fluid communication between the fuel pressurization chamber


14


and the nozzle supply passage


15


will be blocked. Gas ingestion can occur over a brief instant as the needle valve member


20


is not yet closed while fuel pressure has dropped below cylinder pressure. If any engine cylinder combustion gases enter through the nozzle outlet


17


into the lower portion of the nozzle supply passage


15


, they will be blocked from fluid communication with the fuel pressurization chamber


14


when the reverse flow check


52


is in its closed position. Thus, the prior injector prevents gas from being trapped within the fuel pressurization chamber


14


by utilizing the reverse flow check


52


, the plate


51


, and the stop component


42


.




The hydraulic pressure acting on the plunger


13


is then reduced allowing the plunger


13


to retract along the centerline


12


to its upward position under the action of its biasing spring


16


. As the plunger


13


retracts, the pressure within the fuel pressurization chamber


14


preferably will lessen such that fuel from the fuel tank (not shown) can be drawn into the fuel pressurization chamber


14


via the fuel supply line


30


past the check valve


32


. The injection process can once again begin.




Although these reverse flow check valve assemblies have performed well, there is room for improvement. For instance, the reverse flow check valve assemblies limit combustion gases from leaking into the fuel pressurization chamber


14


through the nozzle outlet


17


by blocking fluid communication between the lower portion of the nozzle supply passage


15


and the fuel pressurization chamber


14


toward the end of an injection event. However, the reverse check valve assemblies do not prevent all gases ingested through the nozzle outlet


17


from traveling to the fuel pressurization chamber


14


. Because the reverse flow check


52


remains in the closed position only for a limited time when the reverse flow of fuel is hydraulically displacing it, there is the possibility that combustion gases can leak past the nozzle outlet


17


after the hydraulic pressure caused by the reverse flow of fuel within the nozzle supply passage has subsided. This can occur due to excessive wear on the needle valve seat. Further, the reverse control valve assembly cannot prevent gases from leaking into the fuel pressurization chambers


14


by other means than gas ingestion through the nozzle outlet


17


. Theoretically, gas trapping may occur if t hot combustion gases leak past seals on the outer surface of the fuel injector


10


and travel upward along the outer surface of the fuel injector


10


until they reach the area in the engine head where the fuel supply line


30


exists. The gases then mix with the low pressure fuel and are delivered to the fuel pressurization chamber


14


.




Occasionally, hot combustion gases are ingested through the injector tip and/or enter via the fuel supply are trapped within the fuel pressurization chamber


14


and the nozzle supply passage


15


by the check valve


32


and the direct needle control valve member


20


. The trapped gas creates pressure within the fuel pressurization chamber


14


sufficient to prohibit the check valve


32


from rising off its seat and allowing low pressure fuel into the fuel pressurization chamber


14


. Thus, the fuel pressurization chamber


14


is blocked from fluid communication with the fuel supply line


30


by the check valve


32


. The pressure caused by the trapped gas acting on the opening hydraulic surface


21


within the nozzle supply passage


15


is sometimes not great enough to overcome the biasing spring


22


of the needle valve member


20


. Thus, the nozzle supply passage


15


, is blocked from fluid communication with the nozzle outlet


17


. When this gas trapping occurs, the plunger


13


will advance downward to pressurize the fuel, but there will be little or no fuel within the fuel pressurization chamber


14


because the fuel pressurization chamber


14


is blocked from the fuel supply line


30


by the closed check valve


32


. The gas can never reach a high enough pressure to open the needle valve member


20


and the gas pressure never drops low enough to allow the check valve


32


to lift to its open position to allow fuel into the fuel pressurization chamber


14


. Thus, the plunger


13


reciprocates up and down but nothing happens with the fuel injector


10


. In these cases, the fuel injector


10


needs a means for re-priming itself.




Also, during assembly of new fuel injectors


10


, gases, other than engine cylinder gases, can be trapped within the empty space within the fuel pressurization chambers


14


. If the gas trapping occurs in a new fuel injector


10


, the fuel injector


10


is unable to prime itself and inject fuel into the engine cylinder. If the gas trapping occurs during operation of a fuel injector


10


, the fuel injector


10


is unable to re-prime itself by pushing the gases out of the nozzle outlet


17


. In either situation, once gases are in the fuel pressurization chamber


14


, the pressure within the nozzle supply passage


15


will be insufficient to open the nozzle outlet


17


and the pressure within the fuel pressurization chamber


14


will be too great for the check valve


32


to open. Thus, because the fuel injector


10


has no way of pushing the gas pressure out of the fuel pressurization chamber


14


, the plunger


13


will reciprocate up and down and nothing will happen within the fuel injector


10


.




Moreover, the plate


50


used as a stop for the reverse flow check


52


is subject to fretting, and the thin plate decreases the available height of the stop component


42


which in return increases the risk of oil to fuel transfer.




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




SUMMARY OF THE INVENTION




In one aspect of the invention, a fuel injector comprises an injector body that defines a nozzle supply passage and a nozzle outlet. Within the injector body is positioned a reverse flow valve member that has an opening hydraulic surface exposed to fluid pressure in an upper portion of the nozzle supply passage. The reverse flow valve member is moveable between a closed position in which the nozzle supply passage is blocked and an open position in which the nozzle supply passage is open. The reverse flow valve member is biased toward the closed positioned by a compressed spring.




In another aspect, a fuel injector includes an injector body defining a nozzle outlet. The injector body also includes a barrel that is in contact with a stop component. A movable plunger is at least partially positioned in the barrel. A reverse flow valve member is trapped between the barrel and the stop component, and is movable between a first position and a second position. The plunger, the reverse flow valve member, and the injector body define a nozzle supply passage that includes a fuel pressurization chamber. When the reverse flow valve member is in the second position, the nozzle supply passage is fluidly connected to a lower portion of the nozzle supply passage. A compressed spring is operably positioned in the injector body to bias the reverse flow valve member toward the first position, in which the fuel pressurization chamber is blocked from the lower portion of the nozzle supply passage.




In still another aspect, gas ingestion in a fuel injector is reduced by moving a reverse flow valve member at least in part with a spring to a position that blocks a downstream portion of a nozzle supply passage to an upstream portion of the nozzle supply passage.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a partial sectioned side diagrammatic view of a fuel injector according to the prior art;





FIG. 2

is a partial sectioned side diagrammatic view of a fuel injector according to the preferred embodiment of the present invention;





FIG. 3

is an enlarged view of the reverse flow valve member positioned within the fuel injector of

FIG. 2

;





FIG. 4

is a top view of the reverse flow valve member shown in FIG.


3


and

FIG. 2

;





FIG. 5

is a partial sectioned side diagrammatic view of a reverse flow valve member positioned within a fuel injector according to an alternative embodiment of the present invention;





FIG. 6

is a top view of the reverse flow valve member shown in

FIG. 5

;





FIG. 7

is a partial sectioned side diagrammatic view of a reverse flow valve member positioned within a fuel injector according to a second alternative embodiment of the present invention; and





FIG. 8

is a front view of the reverse flow valve member shown in FIG.


7


.











DETAILED DESCRIPTION




Referring to

FIG. 2

, there is shown a partial sectioned side diagrammatic view through a fuel injector


110


according to the present invention. The fuel injector


110


includes an injector body


111


that includes a barrel


133


and a stop component


142


. Features of fuel injector


110


that are identical to those described with respect to fuel injector


10


of

FIG. 1

have identical numbering. A plunger


13


is movably positioned along a centerline


12


within the injector body


111


. While the plunger


13


, the barrel


33


and a thin plate


50


define a pressurization chamber


14


according to the prior art as illustrated in

FIG. 1

, the injector body


111


, the plunger


13


, and a reverse flow valve member


160


define a nozzle supply passage


115


that includes a fuel pressurization chamber


114


according to the present invention as illustrated in FIG.


2


. The fuel pressurization chamber


114


is fluidly connected to a fuel tank (not shown) via a fuel supply line


130


. When plunger


13


is hydraulically-activated, it advances downward along the centerline


12


in order to pressurize fuel delivered from the fuel tank (not shown) via the fuel supply line


130


. A check valve


32


is positioned within the fuel supply line


130


. The check valve


32


is in its closed position in which it blocks fluid communication between the fuel pressurization chamber


114


and the fuel supply line


130


when the plunger


13


is advancing downward and increasing the pressure within the pressurization chamber


114


. When the plunger


13


is returning to its upward position, the pressure within the pressurization chamber


114


decreases such that the check valve


32


opens and low pressure fuel within the fuel supply line


130


can flow past the check valve


32


and into the pressurization chamber


114


.




The injector body


111


defines a nozzle outlet


17


and a nozzle supply passage


115


, which includes a guide bore


154


. A direct control needle valve is positioned in the injector body


11


and has a direct control needle valve member


20


that is movable between a first position, in which the nozzle outlet


17


is open, and a second position, in which the nozzle outlet


17


is closed. When the direct control needle valve member


20


is in the second, or open, position, the direct control needle valve member


20


is in contact with the stop component


142


. The direct control needle valve member


20


has an opening hydraulic surface


21


that is exposed to fluid pressure within the nozzle supply passage


115


and a closing hydraulic surface


23


that is exposed to fluid pressure within a needle control chamber


24


. A pressure communication passage


25


is in fluid communication with the needle control chamber


24


and controls fluid pressure within the same. The closing hydraulic surface


23


and the opening hydraulic surface


21


are preferably sized such that even when a valve opening pressure is attained in the nozzle supply passage


115


, the direct control needle valve member


20


will not lift open when the needle control chamber


24


is fluidly connected to a source of high pressure actuation fluid. However, it should be appreciated that the relative sizes of the closing hydraulic surface


23


and the opening hydraulic surface


21


should be such that when the closing hydraulic surface


23


is exposed to low pressure in the needle control chamber


24


, the high pressure fuel acting on the opening hydraulic surface


21


should be sufficient to move the direct control needle valve member


20


upward against the force of its biasing spring


22


to open the nozzle outlet


17


. Those skilled in the art should appreciate that while direct control needle valve is the preferred method of controlling the nozzle outlet


17


, a nozzle outlet valve solely controlled by the biasing spring


22


and the hydraulic pressure within the nozzle supply passage


115


may also be used in the present invention.




The injector body


111


, the plunger


13


, and a reverse flow valve member


160


define the nozzle supply passage


115


, which includes the fuel pressurization chamber


114


. Although the described fuel injector


110


includes a fuel pressurization chamber


114


, those skilled in the art will appreciate that the present invention could be utilized in a common rail fuel injector in which there is no fuel pressurization chamber. Rather than the plate


50


being positioned between the barrel


33


and the stop component


42


as it is in the fuel injector


10


according to the prior art, a barrel


133


and a stop component


142


are in contact in the fuel injector


110


according to the present invention. It should also be appreciated that, by removing the plate


50


, the height of the stop component


142


can be increased, which should reduce the oil to fuel transfer and prevent fretting that sometimes occurs in plate


50


. Further, by removing the plate


50


from the present invention, the plate breakage that could occur over time is no longer a concern. A reverse flow valve member


160


is positioned within the guide bore


154


and is trapped between the barrel


133


and the stop component


142


. Although it could be positioned at any point along the nozzle supply passage


115


, the reverse flow valve member


160


preferably is positioned as close to the plunger


13


as possible so that the reverse flow valve member


160


can aid in priming a new fuel injector


110


in the event gas is trapped within its fuel pressurization chamber


114


upon assembly. The reverse flow valve member


160


member is movably positioned along a line parallel to and offset a distance, from the centerline


12


of the injector body


111


. The reverse flow valve member


160


is movable between a first position, or closed position, in which the lower portion of the nozzle supply passage


115


is blocked from fluid communication with the fuel pressurization chamber


114


, and a second position, or open position, in which the lower portion of the nozzle supply passage


115


is open to fluid communication with the fuel pressurization chamber


114


. The reverse flow valve member


160


is biased to its first position by a compressed spring


161


operably positioned in the injector body




Referring to FIG.


3


and

FIG. 4

, there is shown an enlarged view and a top view of the reverse flow valve member


160


of

FIG. 2

, respectively. In the preferred embodiment, the reverse flow valve member


160


has a cupped shape and defines a hollow interior in which a compressed spring


161


is operably positioned to bias the reverse flow valve member


160


toward its upward, closed position. The reverse flow valve member


160


has an opening hydraulic surface


164


exposed to fluid pressure within the fuel pressurization chamber


114


that is part of the upstream portion of the nozzle supply passage


115


. When the plunger


13


advances downward to pressurize fuel within the fuel pressurization chamber


114


, the increased pressure within the fuel pressurization chamber


114


acting on the opening hydraulic surface


164


moves the reverse flow valve member


160


against the action of its compressed spring


161


to its open position in which it is not in contact with a flat valve seat


163


of the barrel


133


. In its open position or its second position, as shown, the reverse flow valve member


160


defines a groove


153


that fluidly connects the fuel pressurization chamber


114


that is included in the upper portion of the nozzle supply passage


115


to the lower portion of the nozzle supply passage


115


. Toward the end of an injection event, the decreased pressure acting on the opening hydraulic surface


164


permits the reverse flow valve member


160


to return in its closed, or first, position, in which the reverse flow valve member


160


is in contact with the flat valve seat


163


of the barrel


133


and, thus, blocks fluid communication between the fuel pressurization chamber


114


and the nozzle supply passage


115


, and vice versa. The size of the groove


153


is preferably selected such that it is large enough to communicate a portion of the required fuel to flow past the reverse flow valve member


160


during an injection event but small enough that there is no leakage between the reverse flow valve member


160


and the valve seat


163


of the barrel


133


during a non injection period.




While the prior art solely relied on of the pressure gradient between the fuel pressurization chamber


14


and the lower portion or the nozzle supply passage


15


to control the movement of the reverse flow check


52


, the present invention uses the compressed spring


161


positioned underneath the reverse flow valve member


160


and the pressure within the fuel pressurization chamber


114


to control the movement of the reverse flow valve member


160


. The strength of the compressed spring


161


is great enough that the reverse flow valve member


160


will remain in its first position for a time sufficient to prevent gas ingestion into the fuel pressurization chamber


114


during peak cylinder pressure. However, the strength of the compressed spring


161


is limited such that the reverse flow valve member


160


remains in its second position for a time sufficient to allow pressurized fuel to flow into the nozzle supply passage


115


before the next injection event. The present invention allows for better control over the movement of the reverse flow valve member


160


, which helps prevent fuel leakage into the engine cylinder. In the preferred embodiment, a pin


162


is operably positioned within the guide bore


154


between the reverse flow valve member


160


and the stop component


142


. Because the pin


162


is received in the guide bore


154


and into the stop component


142


, the pin


162


prevents the reverse flow valve member


160


from rotating with respect to the injector body


111


.




Referring to FIG.


5


and

FIG. 6

, there is shown a partial sectioned side diagrammatic view and a front view of a reverse flow valve member


260


according to an alternate embodiment of the present invention, respectively. Similarly as the preferred embodiment of the present invention, the reverse flow valve member


260


is trapped between a stop component


242


and a barrel


233


and is movable between a first position, or a closed position, and a second position, or an open position. The difference between the fuel injector


110


of the preferred embodiment and the fuel injector


210


of the alternate version is the shape of the reverse flow valve members


160


,


260


. Rather than having a cupped-shape and a hollow interior as does the reverse flow valve member


160


of the preferred embodiment, the reverse flow valve member


260


is a solid disc under which a compressed spring


261


is positioned. Just as in the preferred embodiment, a pin


262


is operably positioned within a guide bore


254


between the reverse flow valve member


260


and the stop component


242


so to prevent the reverse flow valve member


260


from rotating with respect to its injector body


211


.




Referring to FIG.


7


and

FIG. 8

, there is shown a partial sectioned side diagrammatic view and a front view of a reverse flow valve member


360


according to a second alternate embodiment of the present invention, respectively. The second alternate embodiment works similar to the preferred embodiment of the present invention except for the shape of a reverse control flow valve member


360


, the shape of a valve seat


364


and the interaction between the reverse flow valve member


360


and its injector body


311


. Rather than having a circular shape, the reverse flow valve member


360


is rectangular. Because the reverse flow valve member


360


is solid, a compressed spring


361


is operably positioned below the reverse flow valve member


360


in order to bias the reverse flow valve member


360


to its closed position. Further, a valve seat


363


of a barrel


333


is flat and slanted rather than flat and horizontal like in the other embodiments of the present invention. Because the reverse flow valve member


360


and a guide bore


354


are rectangular, there is no need for a pin to prevent the reverse flow valve member


360


from rotating.




INDUSTRIAL APPLICABILITY




Referring to

FIG. 2

, operation of the present invention will be discussed for fuel injectors that pressurize fuel within their injector bodies. It should be appreciated that the present invention can operate in common rail fuel injectors in which the fuel is pressurized outside the body of the fuel injectors. Moreover, it should be appreciated that while different fuel injectors within the engine operate at different stages, the present invention operates in the same manner for each fuel injector and can be applied in an engine with any number of fuel injectors.




In the present invention, the plunger


13


is biased to its upward position under the action of its biasing spring


16


. When plunger


13


is in its upward position, the pressure within the upper portion of the nozzle supply passage


115


that includes the fuel pressurization chamber


114


is at relatively low fuel supply pressure and, thus, permits the check valve


32


to open and low pressure fuel to flow from the fuel tank (not shown) to the fuel pressurization chamber


114


via the fuel supply line


130


. When the plunger


13


is in its upward position, the pressure within the lower portion of the nozzle supply passage


115


acting on the opening hydraulic surface


21


of the direct control needle valve member


20


is also low. Thus, the direct control needle valve member


20


will remain in its closed position under the action of its biasing spring


22


and the hydraulic pressure within the direct control chamber


24


, blocking fluid communication between the nozzle outlet


17


and the fuel pressurization chamber


114


.




Prior to an injection event, the plunger


13


is driven downward by a hydraulic intensifier piston or a tappet to move along a centerline


12


of the fuel injector


110


toward its downward position. This greatly increases fuel pressure within the upper portion of the nozzle supply passage


115


which includes the fuel pressurization chamber


114


and the lower portion of the nozzle supply passage


115


. The increased pressure within the fuel pressurization chamber


114


will close the check valve


32


, blocking fluid communication between the fuel pressurization chamber


114


and the fuel tank (not shown) via the fuel supply line


130


. The pressurized fuel will act on the opening hydraulic surface


164


of the reverse flow valve member


160


and move the reverse flow valve member


160


downward against the action of the compressed spring


161


to its second, or open, position. The reverse flow valve member


160


will move out of contact with the valve seat


163


of the barrel


133


so that the pressurized fuel can flow through to the lower portion of the nozzle supply passage


115


via the groove


153


defined by the reverse flow valve member


160


when in its second position. The direct control needle valve member


20


remains in its closed position blocking fluid communication between the nozzle outlet


17


and the nozzle supply passage


115


until the pressurized fuel acting on the opening hydraulic surface


21


of the direct control needle valve member


20


reaches a valve opening pressure sufficient to overcome the bias of the biasing spring


22


and the needle control chamber


24


is connected to low pressure via the pressure communication line


25


. When the direct control needle valve member


20


moves to its open position, a stop surface of the nozzle outlet valve member


20


is in contact with the stop component


142


, and the nozzle outlet


17


is opened to allow pressurized fuel to be injected into the engine cylinder (not shown).




Shortly before the desired amount of pressurized fuel is injected into the engine cylinder via the nozzle outlet


17


of the fuel injector


110


, the pressure communication line


25


will connect the needle control chamber


24


with a source of high pressure actuation fluid. The direct control needle valve member


20


will close under the hydraulic force within the needle control chamber


24


and the bias of its spring


22


. In its closed position, the direct control needle valve member


20


is blocking fluid communication between the nozzle outlet


17


and the nozzle supply passage


115


. Those skilled in the art should appreciate that the direct needle control valve is the preferred method for operating the nozzle outlet


17


. The direct needle control valve allows the nozzle outlet


17


to be closed under high pressure within the needle control chamber


24


even when there is high pressure within the nozzle supply passage


115


. Thus, the nozzle outlet


17


can remain blocked despite the pressure within the nozzle supply passage


115


. Although a nozzle outlet valve that is controlled solely by a biasing spring and


4


the pressure within the nozzle supply passage


115


can be used, the timing of the reverse flow valve member


160


can be important. When a nozzle outlet valve is used, if the reverse flow valve member


160


moves too quickly to its closed position, gases will be trapped within the nozzle supply passage


115


causing pressure on the hydraulic surface


21


of the nozzle valve outlet member such that it slows the closing of nozzle outlet


17


. Fuel will be able to leak past the open nozzle outlet


17


and dribble into the engine cylinder causing smoke from the engine. If the reverse flow valve member


160


moves too slowly into its closed position, then the nozzle outlet


17


will close approximately at the same time as the reverse flow valve member


160


moves to its closed position. Thus, if the pressure within the engine cylinder is greater than the pressure within the nozzle supply passage


115


at the time the nozzle outlet


17


closes, some of the combustion gases will enter into the injector tip.




The hydraulic pressure acting on the plunger


13


is then reduced allowing the plunger


13


to retract along the centerline


12


to its upward position under the action of its biasing spring


16


, causing the pressure within the fuel pressurization chamber


114


to decrease. The decreased pressure within the fuel pressurization chamber


114


acting on the opening hydraulic surface


164


of the reverse flow valve member


160


will be insufficient to overcome the action of the compressed spring


161


. Thus, the reverse flow valve member


160


will move to its first, or closed position, under the action of the compressed spring


161


. When in the first position, the reverse flow valve member


160


is in contact with a valve seat


163


of the barrel


133


and is blocking fluid communication between the fuel pressurization chamber


114


and the lower portion of the nozzle supply passage


115


. In the event of gas ingestion through the tip of the fuel injector


110


, the gases moving up the lower portion of the nozzle supply passage


115


will be blocked from the fuel pressurization chamber


114


by the reverse flow valve member


160


, which is preferably already in its closed position due to the low pressure within the fuel pressurization chamber


114


acting on its opening hydraulic surface


164


. Thus, the present invention blocks fluid communication between the fuel pressurization chamber


114


and the lower portion of the nozzle supply passage


115


during a non-injection event. This limits gas ingestion due to tip leakage to the relatively small volume below the reverse flow control valve member


160


.




Recall that, with the prior art, gases occasionally are trapped within the fuel pressurization chamber


14


and the nozzle supply passage


15


by the check valve


32


and the direct control needle valve member


20


. The trapped gas creates pressure within the fuel pressurization chamber


14


sufficient to prohibit the check valve


32


from rising off its seat and allowing low pressure fuel into the fuel pressurization chamber


14


. Thus, the fuel pressurization chamber


14


is blocked from fluid communication with the fuel supply line


30


by the check valve


32


. The pressure caused by the trapped gas acting on the opening hydraulic surface


21


within the nozzle supply passage


15


is not great enough to open the needle valve member


20


. Thus, the nozzle supply passage


15


is blocked from fluid communication with the nozzle outlet


17


. The plunger


13


will advance downward to pressurize the fuel, but there will be no fuel within the fuel pressurization chamber


14


because the fuel pressurization chamber


14


is blocked from the fuel supply line


30


by the closed check valve


32


. The gas can never reach a high enough pressure to open the direct needle control valve member


20


and the gas pressure never drops low enough to allow the check valve


32


to lift to its open position to allow fuel into the fuel pressurization chamber


14


. The plunger


13


reciprocates up and down but nothing happens with the fuel injector


10


. While this gas trapping exists in the prior art, it is eliminated in the present invention. Because the movement of the reverse flow valve member


160


is controlled by pressure within the fuel pressurization chamber


114


, the pressure caused by gases that travel into the fuel pressurization chamber


114


will act on the opening hydraulic surface


164


and move the reverse flow valve member


160


to its open position. The gases will flow through the groove


153


and into the nozzle supply passage


115


. Thus, even if gases travel into the fuel pressurization chamber


114


, they will not accumulate and be trapped.




If gases, other than combustion gases, become trapped within the fuel pressurization chamber


114


of a new fuel injector during assembly, the present invention also includes a priming feature that pushes the gas through the fuel injector


110


and out the nozzle outlet


17


. The pressure caused by the gases will act on the opening hydraulic surface


164


of the reverse flow valve member


160


causing the reverse flow valve member


160


to move downward against the action of the compressed spring


161


and open fluid communication between the fuel pressurization chamber


114


and the lower portion of the nozzle supply passage


115


. When the plunger


13


advances, it will push the gases through the groove


153


and into the lower portion of the nozzle supply passage


115


. If there is still gas within the fuel pressurization chamber


114


sufficient to keep the check valve


32


in its closed position when the plunger


13


retracts to its upward position, fuel will not flow into the fuel pressurization chamber


114


from the fuel tank (not shown). However, the plunger


13


will again be hydraulically activated to move downwards against the action of its biasing spring


16


and increase the pressure within the fuel pressurization chamber


114


. The gases will again act on the opening hydraulic surface


164


of the reverse flow control valve member


160


and open fluid communication between the fuel pressurization chamber


114


and the lower portion of the nozzle supply passage


115


. The gases will once again be pushed through the groove


153


and into the nozzle supply passage


115


. The reciprocating plunger


13


will continue pushing the gases out of the fuel pressurization chamber


114


into the lower portion of the nozzle supply passage


115


until the pressure within the fuel pressurization chamber


114


is low enough to allow the check valve


32


to open. Fuel can then flow from the fuel tank (not shown) to the fuel pressurization chamber


114


via the fuel supply line


130


past the check valve. As fuel flows in, repeated plunger movements will eventually achieve needle valve opening pressure allowing the compressed gas and the fuel to exit via the nozzle outlet


17


. Thus, the present invention not only prevents gas trapping within the fuel pressurization chamber


114


by blocking fluid communication between the lower portion of the nozzle supply passage


115


and the fuel pressurization chamber


114


, the present invention also allows fuel injector


110


to prime itself if gas trapping does occur within the fuel pressurization chamber


114


.




Referring to

FIGS. 5 through 8

, there is shown sectioned side diagrammatic illustrations and top views of the reverse flow valve members


260


,


360


according to the two alternate versions of the present invention. The reverse flow valve member


260


,


360


according to the alternate versions of the present invention perform in the same manner as the reverse flow valve member


160


according to the preferred embodiment of the present invention. The difference between the three embodiments are the shapes of the reverse flow valve members


160


,


260


,


360


and the shape of the valve seats


163


,


263


,


363


. For a discussion on these differences, see the Detailed Discussion section of this Application.




Both the prior art and the present invention limit the trapping of combustion gases within the fuel pressurization chambers


14


,


114


by blocking fluid communication between the nozzle supply passage


15


,


115


and the fuel pressurization chamber


114


. However, unlike the prior art, in the event that gases, other than combustion gasses, are trapped within the fuel pressurization chamber


114


of a new fuel injector


110


, the present invention can prime itself by pushing the gases out of the fuel pressurization chamber


114


and decreasing the pressure such that the check valve


32


can lift and allow fuel to flow into the fuel pressurization chamber


114


. Also, this priming feature will eliminate the need for the fuel injector


110


to re-prime itself because any gas that travels into the fuel pressurization chamber


114


should eventually be pushed out of the chamber


114


by the downward strokes of the plunger


13


. Moreover, unlike the prior art in which the reverse flow check


52


may not stay closed during the entire non-injection event, the reverse flow control valve member


160


of the present invention will remain closed during the entire non-injection event. Therefore, the present invention does not just reduce, but prevents, gas trapping in the fuel pressurization chamber


114


caused by gas ingestion in the injector tip. Any gases that are ingested through the tip of the fuel injector


110


will always remain in the portion of the nozzle supply passage


115


below the reverse flow valve member


160


. The present invention removes the plate


50


from between the stop component


142


and the barrel


133


. Thus, the seal between the stop component


142


and the barrel


133


is improved and should reduce oil to fuel transfer. Moreover, the removal of the plate


50


eliminates the potential for excessive wear and plate breakage over time.




It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present invention in any way. Thus, those skilled in the art will appreciate that other aspects, objects, and advantages of the invention can be obtained from a study of the drawings, the disclosure and the appended claims.



Claims
  • 1. A fuel injector comprising:an injector body defining a nozzle supply passage and a nozzle outlet; a reverse flow valve member positioned in the injector body and including an opening hydraulic surface exposed to fluid pressure in an upper portion of the nozzle supply passage, and being moveable between a closed position in which the nozzle supply passage is blocked, and an open position in which the nozzle supply passage is open; a compressed spring operably positioned to bias the reverse flow valve member toward the closed position; the injector body defines a guide bore; the reverse flow valve member being positioned in the guide bore and having a guide clearance in the guide bore; an interaction between the reverse flow valve member and the injector body, and being operable to prevent the reverse flow valve member from rotating with respect to the injector body.
  • 2. The fuel injector of claim 1 wherein the interaction includes a pin in contact with the injector body and the reverse flow valve member.
  • 3. A fuel injector comprising:an injector body defining a nozzle outlet and including a barrel in contact with a stop component; a reverse flow valve member trapped between the barrel and the stop component, and being movable between a first position and a second position; a movable plunger at least partially positioned in the barrel; a nozzle supply passage, which includes a fuel pressurization chamber, being defined by the injector body, the plunger and the reverse flow valve member; the fuel pressurization chamber being fluidly connected to a lower portion of the nozzle supply passage when the reverse flow valve member is in the second position; a compressed spring operably positioned in the injector body to bias the reverse flow valve member toward the first position, in which the fuel pressurization chamber is blocked from the lower portion of the nozzle supply passage; the barrel includes a valve seat; the reverse flow valve member being in contact with the valve seat when in the first position.
  • 4. The fuel injector of claim 3 wherein the reverse flow valve member being moveable along a line parallel to a centerline of the plunger.
  • 5. The fuel injector of claim 4 wherein the reverse flow valve member defines a groove that fluidly connects the plunger bore to the nozzle supply passage when in the second position.
  • 6. The fuel injector of claim 4 including an interaction between the reverse flow valve member and the injector body, and being operable to prevent the reverse flow valve member from rotating with respect to the injector body.
  • 7. The fuel injector of claim 6 wherein the interaction includes a pin in contact with the injector body and the reverse flow valve member.
  • 8. A method of reducing gas ingestion in a fuel injector, comprising the step of:moving a non-spherical reverse flow valve member at least in part with a spring to a position that blocks a downstream portion of a nozzle supply passage to an upstream portion of the nozzle supply passage; and wherein the moving step includes a step of moving the reverse flow valve member into contact with a barrel.
  • 9. The method of claim 8 including a step of moving a stop surface of a nozzle outlet valve member out of contact with a stop component.
  • 10. The method of claim 9 includes a step of moving the nozzle outlet valve member to a closed position.
RELATION TO OTHER PATENT APPLICATION

This application is a continuation of application Ser. No. 10/029,411, filed Dec. 20, 2001, which is now abandoned.

US Referenced Citations (4)
Number Name Date Kind
3115304 Humphries Dec 1963 A
5287838 Wells Feb 1994 A
5505384 Camplin Apr 1996 A
5641121 Beck et al. Jun 1997 A
Continuations (1)
Number Date Country
Parent 10/029411 Dec 2001 US
Child 10/125262 US