Pulsed air assist fuel injector

Information

  • Patent Grant
  • 6209806
  • Patent Number
    6,209,806
  • Date Filed
    Monday, January 11, 1999
    25 years ago
  • Date Issued
    Tuesday, April 3, 2001
    23 years ago
Abstract
A fuel injector having a pulsed air assist atomizer to provide improved atomization and fuel spray targeting. The fuel injector provides a pulsed air supply, rather than a continuous air supply at the discharge of the fuel injector. The fuel injector includes an air inlet, a fuel inlet, mixing chamber and controller for controlling the simultaneous introduction of air and fuel into the mixing chamber. The controller controls an air jet to impact fuel flowing into the mixing chamber to atomize the fuel before discharge of the air-fuel mixture from the fuel injector.
Description




FIELD OF THE INVENTION




This invention relates to air assist fuel injectors used in internal combustion engines and in particular to a fuel injector with a pulsed air assist atomizer.




BACKGROUND OF THE INVENTION




It is known in the art relating to fuel injectors to atomize the fuel injected through the nozzle of a fuel injector. In such fuel injection systems, fuel is atomized into a finely divided spray of small droplets by mixing air with the fuel upon discharge of the mixture from the fuel injector. Air assist atomization of the fuel injected from the fuel injector is used to produce a homogeneous air-fuel mixture. The homogeneity of the air-fuel mixture and gasification of fuel droplets in the combustion space affect the efficiency of the combustion process. A better mixture of air and fuel will produce both a cleaner and a more efficient combustion process. Therefore, it is desirable to obtain a fuel injector that has optimum atomization and accurate fuel spray targeting.




SUMMARY OF THE INVENTION




The present invention provides a fuel injector which supplies pulsed air, rather than a continuous supply of air through the fuel injector. By supplying pulsed air, the atomization and fuel spray targeting are improved. The fuel injector includes air inlet means, fuel inlet means, a mixing chamber and control means for simultaneously controlling introduction of air and fuel into the mixing chamber.




In one embodiment, the fuel injector includes two electromagnetically actuated valves that are used to control an air jet that impacts fuel flowing into a mixing chamber. The controlled air and fuel flows provide atomization of the fuel before discharge of the air-fuel mixture from the injector. The two valves are part of an armature/valve assembly. The assembly includes an armature, air control valve head and hollow needle which forms part of a fuel control valve. The armature is connected to the hollow needle. The air control valve head is mounted on a first axial inlet end of the hollow needle.




In a closed position, the valve head and a second axial outlet end of the needle are seated against an air valve seat and fuel valve seat, respectively, to prevent air and fuel flow into the mixing chamber. Upon energization of an electromagnetic coil, the armature is attracted to a stator and the valve head and needle are lifted from their seats to allow air and fuel flow into the mixing chamber. As the fuel enters the mixing chamber, it is impacted by the air jet resulting in a finely atomized spray. Then the air-fuel mixture is discharged from the fuel injector through a central opening in the fuel valve seat.




These and other features and advantages of the invention will be more fully understood from the following detailed description of the invention taken together with the accompanying drawings.











BRIEF DESCRIPTION OF THE DRAWINGS




The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate presently preferred embodiments of the invention, and, together with a general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.





FIG. 1

is a cross-sectional view of a fuel injector in accordance with the present invention;





FIG. 2

is an enlarged schematic view of the lower end of the fuel injector, illustrating a hollow needle in an open position allowing fuel and air to mix in a mixing chamber during discharge of the fuel injector; and





FIG. 3

is an enlarged schematic view of the upper end of the fuel injector, illustrating an air control valve head in an open position.











DETAILED DESCRIPTION OF THE INVENTION




Referring now to the drawings in detail, numeral


10


generally indicates a fuel injector including a pulsed air assist atomizer. The fuel injector


10


provides a pulsed air jet that impacts the fuel when fuel is being discharged from the injector


10


, and not as a continuous air supply as in conventional air assist injectors, thereby improving the atomization of the fuel.




With reference to

FIGS. 1 and 2

, the injector


10


includes a plastic cover


12


. The plastic cover


12


surrounds upper portions of a tubular stator


14


and a coil assembly housing


16


. Coil assembly


18


surrounds a lower portion of stator


14


. Stator


14


is ferromagnetic and has an air inlet


20


at a first axial end


22


of the stator


14


connected to a pressurized air supply


23


. Below the coil assembly


18


is a valve body


24


in which an armature


26


is reciprocally disposed and positioned coaxially with a second axial end


28


of the stator


14


.




The armature


26


is connected with a hollow needle


30


which has an air control valve head


32


mounted on a first axial inlet end


34


of the needle


30


to form an armature/valve assembly


36


. The valve head


32


may be in the form of a poppet valve. The armature/valve assembly


36


is movable between open and closed positions to permit or prevent air and fuel flow into a mixing chamber


38


at the discharge end of the fuel injector. The valve head


32


and a second axial outlet end


40


of the needle


30


are normally urged against an air valve seat


42


and a fuel valve seat


44


, respectively, in their closed positions by a spring


46


which engages the valve head


32


. The spring


46


is compressed to desired force by an adjustment tube


48


which is pressed to an axial position within the stator


14


and defines the air inlet


20


. The air valve seat


42


forms one end of a valve tube


50


which is pressed to a mounted axial position within the stator


14


. The valve tube


50


extends from the spring


46


to the second axial end


28


of the stator


14


.




The needle


30


and valve head


32


are simultaneously unseated from their seats


44


,


42


to their open positions to allow fuel and air flow in the mixing chamber


38


when the armature


26


is magnetically attracted to the stator


14


upon energization of the coil assembly


18


. The coil assembly


18


includes a plastic bobbin


52


on which an electromagnetic coil


54


is wound. Electrical terminals


56


are connected between an electrical circuit (not shown) and the coil


54


for providing energizing voltage to the coil that operates the fuel injector


10


.




The hollow needle


30


has a central air passage


60


extending from the first axial inlet end


34


of the needle


30


to the second axial outlet end


40


of the needle


30


. The air passage


60


conveys air from the air inlet


20


to the mixing chamber


38


. Air enters the air passage


60


through air holes


62


in the first axial end


34


of the needle


30


as shown in FIG.


3


. The diameter of the hollow needle


30


may be larger than a conventional valve needle to accommodate the air passage


60


. If a needle


30


with a larger diameter is used, a lower valve lift is required to pass the fuel thereby supplying a thinner fuel film which enhances atomization from the air jet.




The armature


26


is guided by an inside wall of the valve body


24


for axial reciprocation. The upper portion of the hollow needle


30


is guided within the valve tube


50


. Further, axial guidance for the needle


30


is provided by a fluid metering member


66


through which the hollow needle


30


extends. The fluid metering meter


66


is disposed within the valve body


24


upstream from the fuel valve seat


44


.




Fuel from a fuel supply


67


enters the fuel injector


10


through fuel inlets


68


in the valve body


24


. A filter assembly


70


is fitted to the fuel inlets


68


to filter particulate matter from the fuel entering the valve body


24


through the inlets


68


. Filtered fuel flows through the fluid metering member


66


which provides a thin fuel film to be impacted by the air jet from the second axial end


40


of the hollow needle


30


in the mixing chamber


38


. The fluid metering member


66


may be a swirl generator plate or an orifice plate. The member


66


is located upstream from the mixing chamber


38


. Also, the air-fuel mixture may be metered by a second metering member


72


, such as a thin orifice disk, located downstream from the fuel valve seat


44


at the discharge end of the fuel injector


10


.




In operation, fuel enters the fuel inlets


68


and passes through the filter assembly


70


into the valve body


24


and through opening


64


in the fluid metering member


66


to the fuel valve seat member


44


. When the coil


54


is not energized, the hollow needle


30


and air control valve head


32


are biased by the spring


46


into their respective closed positions and a small working gap


74


exists between the armature


26


the stator


14


.




Upon energizing of the coil


54


, the armature


26


is magnetically attracted to the second axial end


28


of the stator


14


, closing the working gap


74


. This movement simultaneously unseats the hollow needle


30


from the fuel valve seat


44


and lifts the air control valve head


50


from the air valve seat


42


, allowing fuel film to be impacted by an air jet in the mixing chamber


38


, resulting in a finely atomized spray. The atomized spray is discharged from the fuel injector through a central opening


76


in the fuel valve seat


44


. Upon deenergizing of the coil


54


, the spring


46


pushes the hollow needle


30


and air control valve head


32


back to their closed positions, shutting off fuel and air flow.




Although the invention has been described by reference to a specific embodiment, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiment, but that it have the full scope defined by the language of the following claims.



Claims
  • 1. A fuel injector for an internal combustion engine, comprising:an air supply inlet; a fuel supply inlet; a mixing chamber located at a discharge end of the fuel injector for mixing air and fuel; a control member for controlling the simultaneous introduction of air and fuel into said mixing chamber, the control member including: an armature/valve assembly movable between valve open and closed positions to admit or prevent air and fuel flow into the mixing chamber, the armature/valve assembly including: a fuel control valve having a hollow needle defining a central air passage for conveying air from a first axial end of said needle to a second axial end of said needle, said hollow needle being movable between valve open and closed positions to unseat or seat the second axial end of the needle from or against a valve seat to admit or prevent fuel flow into the mixing chamber; an air control valve head mounted on the first axial end of the hollow needle and said valve head being movable with the needle between open and closed positions to unseat or seat the valve head from or against an air valve seat to admit or prevent air flow into the central air passage; and an armature connected with said hollow needle and movable toward and away from a tubular stator to simultaneously open or close the fuel and air control valves and admit or prevent fuel and air flow into the mixing chamber; a coil assembly surrounding the tubular stator for generating electromagnetic forces to magnetically attract the armature/valve assembly to the stator to allow air and fuel to flow into the mixing chamber; and biasing means for biasing the armature/valve assembly away from the stator toward the valve closed position to prevent air and fuel from flowing into the mixing chamber.
  • 2. A fuel injector as in claim 1 wherein the air control valve is a poppet valve and the first axial end of the hollow needle has air holes for allowing air to flow into the central air passage.
  • 3. A fuel injector as in claim 1 wherein the biasing means is a spring acting between a head of the air control valve and an adjustment tube fixed in said air inlet means.
  • 4. A fuel injection system comprising:an air supply providing a flow of assist air; a fuel supply providing a supply of fuel; a fuel injector having a mixing chamber receiving assist air and fuel; and a control member controlling the simultaneous introduction of air and fuel into said mixing chamber, the control member including: an armature/valve assembly movable between valve open and closed positions to admit or prevent air and fuel flow into the mixing chamber, the armature/valve assembly including: a fuel control valve having a hollow needle defining a central air passage for conveying air from a first axial end of said needle to a second axial end of said needle, said hollow needle being movable between valve open and closed positions to unseat or seat the second axial end of the needle from or against a fuel valve seat to admit or prevent fuel flow into the mixing chamber; an air control valve head mounted on the first axial end of the hollow needle and said valve head being movable with the needle between open and closed positions to unseat or seat the valve head from or against an air valve seat to admit or prevent air flow into the central air passage; and an armature connected with said hollow needle and movable toward and away from a tubular stator to simultaneously open of close the fuel and air control valves and admit or prevent fuel and air flow into the mixing chamber; a coil assembly surrounding the tubular stator for generating electromagnetic forces to magnetically attract the armature/valve assembly to the stator to allow air and fuel to flow into the mixing chamber; and biasing means for biasing the armature/valve assembly away from the stator toward the valve closed position to prevent air and fuel from flowing into the mixing chamber.
  • 5. A fuel injection system as in claim 4 wherein the air control valve is a poppet valve and the first axial end of the hollow needle has air holes for allowing air to flow into the central air passage.
  • 6. A fuel injection system comprising:an air supply providing a flow of assist air; a fuel supply providing a supply of fuel; a fuel injector having a mixing chamber receiving assist air and fuel; and a control member controlling the simultaneous introduction of air and fuel into said mixing chamber, the control member including: an armature/valve assembly movable between valve open and closed positions to admit or prevent air and fuel flow into the mixing chamber; a coil assembly surrounding a tubular stator for generating electromagnetic forces to magnetically attract the armature/valve assembly to the stator to allow air and fuel to flow into the mixing chamber; and biasing means for biasing the armature/valve assembly away from the stator toward the valve closed position to prevent air and fuel from flowing into the mixing chamber, wherein the biasing means is a spring acting between a head of the air control valve and an adjustment tube fixed in said air inlet means.
US Referenced Citations (5)
Number Name Date Kind
1402749 Du Pont Jan 1922
1627727 Charter May 1927
4971254 Daly et al. Nov 1990
5048497 Kishida et al. Sep 1991
5119792 Gu Jun 1992