Air assist fuel injectors and method of assembling air assist fuel injectors

Abstract
A first air assist fuel injector configured for operation with a two stroke engine and a second air assist fuel injector configured for operation with a four stroke engine. The first air assist fuel injector and the second air assist fuel injector share one or more common items, such as a solenoid coil assembly and/or an armature, even though the air assist fuel injectors are configured for different applications.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to air assist fuel injectors, and, more particularly, to an assembly of air assist fuel injectors and a method of assembling air assist fuel injectors.




2. Description of the Related Art




Conventional fuel injectors are configured to deliver a quantity of fuel to a combustion cylinder of an engine. To increase combustion efficiency and decrease pollutants, it is desirable to atomize the delivered fuel. Generally speaking, atomization of fuel can be achieved by supplying high pressure fuel to conventional fuel injectors, or atomizing low pressure fuel with pressurized gas, i.e., “air assist fuel injection.”





FIG. 1

illustrates a conventional air assist fuel injector


20


mounted to an air/fuel rail


30


. The rail


30


houses a conventional fuel injector


40


and also defines a mount for the air assist fuel injector


20


. The conventional fuel injector


40


and the fuel rail


30


are configured such that a metered quantity of fuel is delivered from the fuel injector to the air assist fuel injector


20


. Additionally, the rail


30


includes a number of passageways


42


that deliver pressurized air to the air assist fuel injector


20


. The air assist fuel injector


20


atomizes the low pressure fuel with the pressurized air and conveys the air and fuel mixture to the combustion chamber of an engine (not illustrated).




As illustrated in

FIG. 1

, the pressurized air from the air/fuel rail


30


and the metered quantity of fuel from the conventional fuel injector


40


enter the air assist fuel injector


20


through an inlet in the center of an armature


26


. Thereafter, the fuel and air travel through the interior of a poppet


24


, and exit the poppet through small slots near the end or head of the poppet. The poppet


24


is attached to the armature


26


, which is actuated by energizing a solenoid


22


. When the solenoid


22


. is energized, the armature


26


will overcome the force of a spring


28


and move toward a leg


30


. Because the poppet


24


is attached to the armature, the head of the poppet will lift off a seat


32


so that a metered quantity of atomized fuel is delivered to the combustion chamber of an engine.




The configuration of two and four stroke engines dictate the external dimensions of the air assist fuel injector


20


. Conventionally, separate air assist fuel injectors are manufactured for two and four stroke engine applications to satisfy the different dimensional requirements of the two applications. For example, two stroke engines often require a shorter air assist fuel injector than that required for four stroke engine applications because of strict space constraints directly over the head of the two stroke engine. In contrast, four stroke engine applications often require a narrower air assist fuel injector than that required for two stroke engine applications because of strict space constraints in and around the head of the four stroke engine. Additionally, four stroke engine applications often require a longer air assist fuel injector than that required for two stroke engine applications because the air assist fuel injector must extend into the cam valley, but avoid the valve components and any water passageways. Hence, two stroke engine applications have very tight height restrictions, requiring short air assist fuel injectors, while four stroke engine applications have very tight diameter restrictions, requiring long and very small diameter air assist fuel injectors.




Because of these different dimensional requirements, a single, one-size, air assist fuel injector unfortunately cannot satisfy both two stroke and four stoke commercial applications. Hence, conventional air assist fuel injectors for two stroke engine applications and four stoke engine applications are independently manufactured and thus do not share common parts, especially solenoids. For more than a decade, this constraint has proven to be particularly problematic in attempts to economically manufacture air assist fuel injectors for both two and four stroke applications.




SUMMARY




In light of the previously described problems associated with manufacturing conventional air assist fuel injectors, one object of the many embodiments of the present invention is to provide air assist fuel injectors for both two and four stroke engines that have one or more common parts but also satisfy the dimensional and functional requirements of these applications.




In furtherance of this object, an additional aim of the many embodiments of the present invention is to provide methods of assembling air assist fuel injectors with one or more common parts for both two and four stroke engine applications.




Other objects, advantages and features associated with the embodiments of the present invention will become more readily apparent to those skilled in the art from the following detailed description. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modification in various obvious aspects, all without departing from the invention. Accordingly, the drawings and the description are to be regarded as illustrative in nature, and not limitative.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a partial cross-sectional view of a conventional air assist fuel injector mounted to a conventional air/fuel rail housing a conventional fuel injector.





FIG. 2

is a side view of an air assist fuel injector configured for a two stroke engine application in accordance with one embodiment of the present invention.





FIG. 3

is a top view of the air assist fuel injector illustrated in FIG.


2


.





FIG. 4

is a rear view of the air assist fuel injector illustrated in FIG.


2


.





FIG. 5

is a cross-sectional view of the air assist fuel injector illustrated in

FIG. 2

taken along the line


5





5


in FIG.


4


.





FIG. 6

is a side view of an air assist fuel injector configured for a four stroke engine application in accordance with one embodiment of the present invention.





FIG. 7

is a top view of the air assist fuel injector illustrated in FIG.


6


.





FIG. 8

is a rear view of the air assist fuel injector illustrated in FIG.


6


.





FIG. 9

is a cross-sectional view of the air assist fuel injector illustrated in

FIG. 6

taken along the line


9





9


in FIG.


8


.





FIG. 10

is an exploded view of FIG.


5


.





FIG. 11

is an exploded view of FIG.


9


.





FIG. 12

is an exploded assembly view of the air assist fuel injector illustrated in FIG.


2


.





FIG. 13

is an exploded assembly view of the air assist fuel injector illustrated in FIG.


6


.





FIG. 14

is a partial cross-sectional view of the air assist fuel injector illustrated in

FIG. 2

located in the head of a two stroke internal combustion engine.





FIG. 15

is a partial cross-sectional view of the air assist fuel injector illustrated in

FIG. 6

located in the head of a four stroke internal combustion engine.





FIG. 16

is a diagram illustrating one method of assembling the air assist fuel injector illustrated in FIG.


2


and/or the air assist fuel injector illustrated in FIG.


6


.





FIG. 17

is a diagram illustrating inventories of parts for assembling the air assist fuel injectors illustrated in

FIGS. 2 and 6

in accordance with embodiments of the present invention.





FIG. 18

is a cross-sectional view of an alternative embodiment of an air assist fuel injector configured for a two stroke application in accordance with one embodiment of the present invention.





FIG. 19

is a cross-sectional view of an alternative embodiment of an air assist fuel injector configured for a four stroke application in accordance with one embodiment of the present invention.











DESCRIPTION OF SPECIFIC EMBODIMENTS





FIGS. 1-17

illustrate embodiments of air assist fuel injectors


100


,


100


′. The air assist fuel injector


100


is configured for a two stroke internal combustion engine, while the air assist fuel injector


100


′ is configured for a four stroke internal combustion engine. As described further below, and contrary to conventional wisdom, the air assist fuel injectors


100


,


100


′ share a number of identical parts, greatly simplifying and economizing the commercial manufacture of the two air assist fuel injectors


100


,


100


′ as compared to conventional air assist fuel injectors configured for the same applications. Because the air assist fuel injectors


100


,


100


′ are functionally similar and share a number of similar parts, like numbered parts of the injector


100


refer to like numbered parts of the injector


100


′ in the description that follows.





FIGS. 2-5

,


10


,


12


, and


14


illustrate the components of the air assist fuel injector


100


, which is configured for operation with a two-stroke internal combustion engine.

FIGS. 6-8

,


11


,


13


, and


15


illustrate the components of the air assist fuel injector


100


′, which is configured for operation with a four-stroke internal combustion engine.

FIG. 18

illustrates an alternative embodiment of an air assist fuel injector


100


″ configured for operation with a two-stroke internal combustion engine, and

FIG. 19

illustrates an alternative embodiment of an air assist fuel injector


100


′″ configured for operation with a four-stroke internal combustion engine.




For purposes of comparison:

FIGS. 2 and 6

illustrate the air assist fuel injectors


100


,


100


′ at the same dimensional scale;

FIGS. 3-5

and


7


-


9


illustrate the air assist fuel injectors


100


,


100


′ at the same dimensional scale;

FIGS. 10 and 11

illustrate the air assist fuel injectors


100


,


100


′ at the same dimensional scale;

FIGS. 12 and 13

illustrate the air assist fuel injectors


100


,


100


′ at the same dimensional scale; and

FIGS. 18 and 19

illustrate the air assist fuel injectors


100


″,


100


′″ at the same dimensional scale.




As is apparent by comparing

FIGS. 2-5

with

FIGS. 6-8

, the external dimensions, i.e., periphery, of the air assist fuel injectors


100


,


100


′ are significantly different. This is because two stroke and the four stroke internal combustion engines dictate different dimensional requirements for air assist fuel injectors. For example, the dimensions of a two stroke internal combustion engine typically require that the air assist fuel injector


100


be shorter or more compact than that required for a four stroke internal combustion engine. Likewise, the dimensions of a four stroke internal combustion engine typically require that the air assist fuel injector


100


′ be longer and have a smaller diameter than that required for a two stroke internal combustion engine. Hence, as illustrated by comparing

FIGS. 2 and 6

, the air assist fuel injector


100


is generally more compact, i.e., shorter, than the air assist fuel injector


100


′ as measured along a longitudinal axis y, y′ of each air assist fuel injector


100


,


100


′. Accordingly, the air assist fuel injector


100


′ has a longer length L′ as measured along the longitudinal axis y′ of the air assist fuel injector


100


′ than the length L of the air assist fuel injector


100


as measured along the longitudinal axis y, y′ of the air assist fuel injector


100


. As described further below, various components of the air assist fuel injectors


100


,


100


′ contribute to the overall length L, L′ of the air assist fuel injectors. The items, i.e., components or parts, of the air assist fuel injectors


100


,


100


′ are now briefly described, followed by an explanation of the operation of the air assist fuel injectors, and then a description of the assembly of the air assist fuel injectors.




The air assist fuel injectors


100


,


100


′ are configured to utilize pressurized gas to atomize low pressure liquid fuel, which together travel through the respective air assist fuel injectors


100


,


100


′ along a direction of flow f, f′, as indicated in

FIGS. 2 and 6

. As best illustrated by

FIGS. 10 and 11

, the air assist fuel injectors


100


,


100


′ each include two primary assemblies: a solenoid assembly


110


,


110


′ and a valve assembly


160


,


160


′. The air assist fuel injectors


100


,


100


′ also each include a cap


200


,


200


′ that defines an inlet to the air assist fuel injector for the pressurized gas and liquid fuel. Each cap


200


,


200


′ includes at least one fuel passageway


210


,


210


′ that receives liquid fuel and at least one gas passageway


212


,


212


′ that receives pressurized gas. In the preferred embodiment of the respective air assist fuel injectors


100


,


100


′, each cap


200


,


200


′ includes only one cylindrical liquid fuel passageway


210


,


210


′ located along the center axis of the cap, and four cylindrical gas passageways


212


,


212


′ circumferentially and equally spaced about the respective liquid fuel passageway


210


,


210


′. In alternative embodiments, the air assist fuel injectors


100


,


100


′ do not include the respective caps


200


,


200


′ or include alternatively configured caps. For example, the liquid fuel and pressurized gas may enter each air assist fuel injector


100


,


100


′ through an armature


172


,


172


′ of each air assist fuel injector, as opposed to the caps


200


,


200


′. Alternatively, each cap


200


,


200


′ may include only one passageway that receives liquid fuel and pressurized gas for eventual or immediate delivery to the interior of the respective air assist fuel injectors


100


,


100


′.




As illustrated by

FIGS. 10-13

, the solenoid assemblies


110


,


110


′ each at least include a coil


114


,


114


′ of conductive wire wrapped around a tubular bobbin


112


,


112


′. Each coil


114


,


114


′ preferably includes a winding of insulated conductor that is wound helically around the respective bobbin


112


,


112


′. The coils


114


,


114


′ each have two ends


116


,


116


′ (see

FIGS. 12 and 13

) which are each electrically connected, such as soldered, to a terminal


122


,


122


′. Each coil


114


,


144


′ is energized by providing current to respective connectors


123


,


123


′, which are electrically connected to the respective terminals


122


,


122


′.




Each coil


114


,


114


′ and bobbin


112


,


112


′ together define a respective solenoid coil assembly


120


,


120


′ of each respective solenoid assembly


110


,


110


′ (see FIGS.


12


and


13


). The solenoid coil assembly


120


,


120


′ of each solenoid assembly


110


,


110


′ is that portion of the respective solenoid assemblies that produces a magnetic field when electric current is applied to the respective coils


114


,


114


′. As illustrated by

FIGS. 12 and 13

, the solenoid coil assembly


120


of the air assist fuel injector


100


and the solenoid coil assembly


120


′ of the air assist fuel injector


100


′ are identical, despite the fact that the air assist fuel injector


100


is configured for operation with a two stroke internal combustion engine and the air assist fuel injector


100


′ is configured for operation with an four stroke internal combustion engine. Because the solenoid coil assembly


120


and the solenoid coil assembly


120


′ are identical, they are interchangeable between the two differently configured air assist fuel injectors


100


,


100


′.




In the preferred embodiments of the air assist fuel injectors


100


,


100


′, the identical solenoid coil assemblies


120


,


120


′ are pre-manufactured such that they have the same shape, size and content. Each pre-manufactured and identical solenoid coil assembly


120


,


120


′ includes the respective bobbin


112


,


112


′, coil


114


,


114


′, and ends


116


,


116


′. Because the solenoid coil assemblies


120


,


120


′ are identical, the bobbin


112


and the bobbin


112


′ are identical, the coil


114


and the coil


114


′ are identical, and the ends


116


and the ends


116


′ are identical.




One reason why the solenoid coil assemblies


120


,


120


′ are identical is because the Applicants discovered that a common solenoid coil assembly


120


,


120


′ could satisfy the strict dimensional requirements of many two stroke engine and four stroke engine applications, while still satisfying as the functional design requirements of both applications. As illustrated in

FIGS. 2 and 6

, this is achieved by each solenoid height h, h′ being small enough to fit both two stroke and four stroke applications, and each solenoid diameter Ø, Ø′ being small enough to fit four stroke applications. In accordance with one embodiment of the present invention, each solenoid height h, h′ equals approximately 20 mm and each solenoid diameter Ø, Ø′ equals approximately 20 mm. Although these dimensions are preferred, it will be realized that other dimensions for each solenoid height h, h′ and each solenoid diameter Ø, Ø′ will also suffice, depending upon the dimensional and functional requirements of the specific two stroke engine and four stroke engine applications. Exemplary solenoid coil assemblies


120


,


120


′ suitable for the present invention include those commercially available from Trans Era, located in Ontario, Canada. The preferred identical solenoid coil assemblies


120


,


120


′ have the following specifications: turns=189, wire gauge=27, and resistance=1.36 Ohm. The normal applied operating voltage is, for example, approximately 14 volts and the minimum operating voltage is approximately 6 volts.




Although each solenoid coil assembly


120


,


120


′ includes the respective bobbin


112


,


112


′, coil


114


,


114


′, and ends


116


,


116


′, alternative embodiments of the solenoid coil assemblies may include other items of the solenoid assembly


110


,


110


′. For example, the identical solenoid coil assemblies


120


,


120


′ may also include a casing


118


,


118


′, one or more retainers


124


,


124


′,


126


,


126


′, or other items of the respective solenoid assemblies


110


,


110


′. Additionally, although the preferred embodiments of each solenoid assembly


110


,


110


′ include the items illustrated in

FIGS. 10-13

and further described below, it will be appreciated that alternative embodiments of the solenoid assemblies


110


,


110


′ may include more or less of these items, so long as each solenoid assembly includes a coil and a bobbin. For example, each solenoid assembly


110


,


110


′ may only include the respective coil


114


,


114


′ bobbin


112


,


112


′ ends


116


,


116


′ and casing


118


,


118


′.




Each bobbin


112


,


112


′ of each solenoid coil assembly


120


,


120


′ is essentially a spool on which the conductor of the coil


114


,


114


′ is wound. Each bobbin


112


,


112


′ also defines a throughole


111


,


111


′ in which an armature


172


,


172


′ is electromagnetically actuated, as further described below. Each bobbin


112


,


112


′ and coil


114


,


114


′ are located at least partially within a tubular casing


118


,


118


′ of soft magnetic steel. Hence, the respective tubular casing


118


,


118


′ at least partially encases the respective coil


114


,


114


′. In the preferred embodiments, the respective casings


118


,


118


′ are identical such that they have the same shape, size and content.




The solenoid assemblies


110


,


110


′ also each include an upper retainer


126


,


126


′ and a lower retainer


124


,


124


′, which are annular bodies that partially close-off the ends of the casing


118


,


118


′. Each upper retainer


126


,


126


′ and each lower retainer


124


,


124


′ include a cylindrical passageway coincident with the respective throughole


111


,


111


′ of the corresponding bobbin


112


,


112


′. The retainers


126


,


126


′,


124


,


124


′ of each solenoid assembly


110


,


110


′ retain the respective bobbin


112


,


112


′ and coil


114


,


114


′ in the respective casing


118


,


118


′. The cylindrical passageway of each upper retainer


126


,


126


′ receives at least a portion of the respective cap


200


,


200


′. Each cap


200


,


200


′ is preferably press fit into the respective armature guide


168


,


168


′. The cylindrical passageway of each lower retainer


124


,


124


′ receives at least a portion of the respective valve assembly


160


,


160


′. Each solenoid assembly


110


,


110


′ also includes an overmold


128


,


128


′ of insulative material, such as glass-filled nylon, that houses the respective casing


118


,


118


′ and at least a portion of the respective upper and lower retainers


126


,


126


′,


124


,


124


′. The respective overmolds


128


,


128


′ also house the terminals


122


,


122


′ and a portion of the connectors


123


,


123


′, as illustrated in

FIGS. 10 and 11

.




Referring again to

FIGS. 10 and 11

, the valve assembly


160


,


160


′ of each air assist fuel injector


100


,


100


′ defines the dynamic portion of the air assist fuel injector that functions as a valve to deliver the atomized quantity of liquid fuel and gas. As illustrated in

FIGS. 10 and 11

, the preferred embodiments of the valve assemblies


160


,


160


′ each include an armature


172


,


172


′, a poppet


162


,


162


′, a seat


164


,


164


′, a leg


166


,


166


′, a spring


170


,


170


′, and an armature guide


168


,


168


′. The armatures


172


,


172


′ are each formed of a ferromagnetic material, such as


430


FR stainless steel or similar, and each function as the moving part of an electromagnetic actuator, defined by each solenoid coil assembly


120


,


120


′ and respective armature


172


,


172


′ combination. Each armature weighs approximately 3.91 grams. As illustrated in

FIGS. 5 and 9

, each armature


172


,


172


′ of the respective air assist fuel injector


100


,


100


′ is located relative to the respective solenoid coil assembly


120


,


120


′ such that each armature is subject to the lines of flux generated by the respective solenoid coil assembly. Hence, each armature


172


,


172


′ is actuated when the respective solenoid coil assembly


120


,


120


′ is energized. In the preferred embodiments, each armature


172


,


172


′ is located partially within the respective throughole


111


,


111


′ of the respective bobbin


112


,


112


′.




Each armature


172


,


172


′ includes a passageway


180


,


180


′ that conveys a mixture of liquid fuel and gas to a respective inlet


182


,


182


′ of the respective poppet


162


,


162


′. In the preferred embodiment, the passageway


180


,


180


′ of each armature


172


,


172


′ includes a conical conduit extending from a first end of each armature


172


,


172


′ adjacent the respective cap


200


,


200


′ to the respective inlet


182


,


182


′ of the respective poppet


162


,


162


′. Each inlet


182


,


182


′ is located at an approximate midpoint along the length of the respective armature


172


,


172


′. However, the passageways


180


,


180


′ may take other forms. For example, the passageways


180


,


180


′ may each be one cylindrical passageway extending the entire length of each armature


172


,


172


′, a plurality of passageways, or other configurations, as will be apparent.




In the preferred embodiments, each armature


172


,


172


′ also includes grooves


169


,


169


′ in the cylindrical exterior surface of the respective armature and grooves


173


,


173


′ in the bottom face of the respective armature. As illustrated in

FIGS. 10-13

, the grooves


169


,


169


′ extend the entire length of the respective armature


172


,


172


′. The grooves


169


,


169


′,


173


,


173


′ serve to relieve any pressure differential between an area upstream of the respective armature


172


,


172


′ and an area downstream of the respective armature. The grooves


169


,


169


′,


173


,


173


′ also help reduce surface adhesion between the respective armature


172


,


172


′ and corresponding leg


166


,


166


′.




As illustrated by

FIGS. 12 and 13

, the armature


172


of the air assist fuel injector


100


and the armature


172


′ of the air assist fuel injector


100


′ are identical, despite the fact that the air assist fuel injector


100


is configured for operation with a two stroke internal combustion engine and the air assist fuel injector


100


′ is configured for operation with an four stroke internal combustion engine. That is, the armature


172


and the armature


172


′ have the same shape and size, and are thus interchangeable between the two differently configured air assist fuel injectors


100


,


100


′.




Each poppet


162


,


162


′ is attached to the corresponding armature


172


,


172


′, which is actuated by energizing the solenoid coil assembly


120


,


120


′. As illustrated in

FIGS. 10 and 11

, in the preferred embodiments, each armature


172


,


172


′ includes a cylindrical passageway located downstream of the respective passageways


180


,


180


′ and that matingly receives a first end portion


184


,


184


′ of the respective poppets


162


,


162


′. Hence, each inlet


182


,


182


′ is located immediately downstream of the respective passageway


180


,


180


′ with respect to the direction of flow f, f′ of the mixture of liquid fuel and gas. In the preferred embodiments, the end portion


184


,


184


′ of the respective poppets


162


,


162


′ are each attached to the respective armatures


172


,


172


′ with a welded connection, preferably a YAG laser weld. However, alternative attachments are also contemplated. For example, the poppet


162


,


162


′ may be attached to the armature


172


,


172


′ at any variety of locations with an interference fit, an adhesive, a threaded or screwed attachment, a lock and key attachment, a retaining ring attachment, an electron beam weld, an ultrasonic weld, or other known attachments. Because each poppet


162


,


162


′ is attached to the respective armature


172


,


172


′, each poppet


162


,


162


′ will move with the armature when the armature is actuated by energizing the solenoid assembly


110


,


110


′. In alternative embodiments, each passageway


180


,


180


′ extends between the upstream end face and the opposing, downstream end face of the respective armature


172


,


172


′, i.e., the entire length of the respective armature, and the first end portion


184


,


184


′ of the each poppet is attached to the respective armature at the downstream end face of the corresponding armature.




Each poppet


162


,


162


′ is an elongated hollow tube for conveying the mixture of liquid fuel and pressurized gas, and each include a stem


163


,


163


′ (see

FIGS. 12 and 13

) and a head


174


,


174


′. Each inlet


182


,


182


′ of each poppet


162


,


162


′ opens into a tubular passageway


178


,


178


′, which extends from the inlet


182


,


182


′ to outlets


176


,


176


,′ which are located just prior to the respective head


174


,


174


′ of each poppet. In the preferred embodiments, each poppet


162


,


162


′ includes four slot-shaped outlets


176


,


176


′ that are equally spaced from each other and located approximately transverse to the longitudinal axis of the poppet. Although preferred that each poppet


162


,


162


′ have four slot-shaped outlets


176


,


176


′, other configurations will suffice. For example, each poppet


162


,


162


′ may include one slot shaped outlet, two circular outlets, five oval outlets, or ten pin sized outlets.




Each head


174


,


174


′ is located downstream of the respective outlets


176


,


176


′ and is roughly mushroom shaped with a conical or angled face that seats against the seat


164


,


164


′ when the solenoid assembly is not energized. When each armature


172


,


172


′ is actuated by energizing the respective solenoid coil assembly


120


,


120


′, the respective poppet


162


,


162


′ moves with the corresponding armature such that the respective head


174


,


174


′ is lifted off the corresponding seat


164


,


164


′ in a direction away from the air assist fuel injector. When the respective head


174


,


174


′ is lifted off the corresponding seat


164


,


164


′, a seal is broken between the respective head and seat such that liquid fuel and gas exiting the respective outlets


176


,


176


′ exits each air assist fuel injector


100


,


100


′.




As also illustrated in

FIGS. 10 and 11

, movement of each poppet


162


,


162


′ is guided at a bearing


175


,


175


′ between the respective poppet


162


,


162


′ and the corresponding seat


164


,


164


′. Each bearing


175


,


175


′ is located just prior to the outlets


176


,


176


′ with respect to the direction of flow f, f′ of the liquid fuel and gas through the injector. Hence, each poppet


162


,


162


′ and each seat


164


,


164


′ include a bearing surface for guiding movement of the poppet near the head end of each poppet


162


,


162


′. Because each seat


176


,


176


′ serves as a bearing for poppet movement and also absorbs the impact of the respective head


174


,


174


′ when the poppet valve assembly


160


,


160


′ opens and closes, the seat is preferably fabricated from a wear and impact resistant material, such as hardened


440


stainless steel. It will be appreciated that the air assist fuel injectors


100


,


100


′ need not include a separate seat. For example, each leg


166


,


166


′ may define the respective seat


164


,


164


′ and bearing


175


,


175


′.




The poppets


162


,


162


′ are elongated because when installed, the air assist fuel injectors


100


,


100


′ each protrude through the head of an engine to reach a combustion chamber. As is illustrated in

FIGS. 12 and 13

, a length l of the poppet


162


of the air assist fuel injector


100


is less than a length l′ of the poppet


162


′ of the air assist fuel injector


100


′. The poppet


162


′ of the air assist fuel injector


100


′ is longer than the poppet


162


of the air assist fuel injector


100


because the air assist fuel injector


100


′ is configured for operation with a four stroke internal combustion engine, which generally requires that the air assist fuel injector


100


′ extend into a cam valley of the four stroke engine. Because two stroke engines generally do not have an elaborate cam valley as do four stroke engines, it is not necessary that the poppet


162


be as long as the poppet


162


′. Moreover, it is preferable that the air assist fuel injector


100


, and hence the poppet


162


, be as short as possible because of the strict space constraints directly over the head of two stroke engines.




As further illustrated in

FIGS. 10 and 11

, each poppet


162


,


162


′ moves within the elongated channel


165


,


165


′ of the respective leg


166


,


166


′. Each leg


166


,


166


′ is an elongated body through which the respective poppet


162


,


162


′ moves and which supports the respective seat


164


,


164


′. The interior channel of each leg


166


,


166


′ through which the respective poppet


162


,


162


′ moves may also serve as a secondary flow path for the pressurized gas. Hence, when each head


174


,


174


′ lifts off the respective seat


164


,


164


′, pressurized gas flows outside the respective poppet but inside the leg


166


,


166


′ to help atomize the liquid fuel and gas exiting the respective outlets


176


,


176


′. As illustrated in

FIGS. 10-13

, each leg


166


,


166


′ has a different length for the same reasons set forth above in regard to the poppets


162


,


162


′. Poppet


162


weighs approximately 1.4 grams and poppet


162


′ weighs approximately 2.82 grams.




The spring


170


,


170


′ of each valve assembly


160


,


160


′ is located between the respective armature


172


,


172


′ and leg


166


,


166


′. More particularly, each spring


170


,


170


′ sits within a recessed bore


171


,


171


′ that is concentric with the elongated channel


165


,


165


′ of the leg. Each bore


171


,


171


′ faces the respective armature


172


,


172


′ and defines a seat for the corresponding spring


170


,


170


′. Each spring


171


,


171


′ is a compression spring having a first end that abuts the respective armature


172


,


172


′ and a second end that abuts the respective leg


166


,


166


′. The bottom of each bore


171


,


171


′ defines the seat for the downstream end of the respective spring


170


,


170


′ and a recess


183


,


183


′ defines a seat for the upstream end of the respective spring. The spring


170


,


170


′ functions to bias the respective armature


172


,


172


′ away from the respective leg


166


,


166


′. When the solenoid coil assembly


120


,


120


′ is not energized, each spring


170


,


170


′ biases the respective armature


172


,


172


′ away from the respective leg


166


,


166


′ and thus the corresponding poppet


162


,


162


′ is maintained in a closed position where the respective head


174


,


174


′ abuts against the corresponding seat


164


,


164


′. However, when each solenoid coil assembly


120


,


120


′ is energized, the electromagnetic force causes the respective armature


172


,


172


′ to overcome the biasing force of the corresponding spring


170


,


170


′ such that the armature moves toward the leg until it abuts a stop surface


167


,


167


′ of the respective leg


166


,


166


′. When the solenoid coil assembly


120


,


120


′ is de-energized, the electromagnetic force is removed and the respective spring


170


,


170


′ again forces the corresponding armature


172


,


172


′ away from the respective stop surface


167


,


167


′.




As illustrated by

FIGS. 12 and 13

, the spring


170


of the air assist fuel injector


100


and the spring


170


′ of the air assist fuel injector


100


′ are identical, despite the fact that the air assist fuel injector


100


is configured for operation with a two stroke internal combustion engine and the air assist fuel injector


100


′ is configured for operation with a four stroke internal combustion engine. That is, the spring


170


and the armature


170


have the same shape and size, and are thus interchangeable between the two differently configured air assist fuel injectors


100


,


100


′. In the preferred embodiments, the springs


170


,


170


′ have the following specifications: Spring Rate=3.1 N/mm; Load at 8.24 mm=13.80 N±0.5 N.




As also illustrated in

FIGS. 10 and 11

, movement of each armature


172


,


172


′ is guided by a bearing


161


,


161


′ between the respective outer surface of each armature and the inner surface of the corresponding armature guide


168


,


168


′. The armature guide


168


,


168


′ is essentially a tube that extends at least a portion of the length of the respective armature


172


,


172


′ to act as a guide for the armature. In the preferred embodiments, each armature guide


168


,


168


′ has a first end


151


,


151


′ located upstream of the respective armature


172


,


172


′ with respect to the direction of flow f, f′ and a second end


153


,


153


′ located downstream of the armature with respect to the direction of flow f, f′ such that each armature guide


168


,


168


′ also seals the solenoid coil assembly


120


,


120


′ from the liquid fuel and gas flowing through the valve assembly


160


,


160


′. Hence, the second end


153


,


153


′ of each armature guide


168


,


168


′ is sealingly attached to the respective leg,


166


,


166


′ such as by a laser weld or otherwise, and the outer surface of each armature guide near the respective first end


151


,


151


′ serves as a sealing surface for an upper seal


202


,


202


′ (see FIGS.


5


and


9


). This arrangement helps prevent any liquid fuel and gas from exiting the air assist fuel injectors


100


,


100


′. Although the armature guide


168


,


168


′ is preferred, it will be appreciated that the air assist fuel injectors


100


,


100


′ need not include the armature guide. For example, a portion of the respective solenoid assembly


110


,


110


′ or a separate insert may function as a guide for the respective armature


172


,


172


′. Additionally, the respective solenoid coil assembly


120


,


120


′ may be sealed from the liquid fuel and gas with multiple o-rings, rather than with the aid of each armature guide


168


,


168


′, as will be apparent. Moreover, caps


200


,


200


′ slidably engage each respective armature guide


168


,


168


′ when assembled.




Although in the illustrated embodiment of each air assist fuel injector


100


,


100


′ the armature guides


168


,


168


′ and other portions of each air assist fuel injector are not identical, it will be appreciated that alternative embodiments may include identical armature guides


168


,


168


′, solenoid assemblies, and other parts. For example,

FIG. 18

illustrates an air assist fuel injector


100


″ configured for operation with a two stroke engine and

FIG. 19

illustrates an air assist fuel injector


100


′″ configured for operation with a four stroke engine. Besides having identical solenoid coil assemblies, armatures


172


″,


172


′″, and springs


170


″,


170


′″, the air assist fuel injectors


100


″,


100


′″ also include identical armature guides


168


″,


168


′″, lower seals


204


″,


204


′″, lower retainers


124


″,


124


′″, casings


118


′,


118


′″, terminals


122


″,


122


′″, connectors


123


″,


123


′″ (not illustrated), overmolds


128


″,


128


′″, upper retainers


126


″,


126


′″, upper seals


202


″,


202


′″ and caps


200


″.


200


′″. The air assist fuel injector


100


″ is identical in every respect to the air assist fuel injector


100


, and the air assist fuel injector


100


′″ is identical in every respect to the air assist fuel injector


100


′, except that the armature guides


168


″,


168


′″, lower seals


204


″,


204


′″, seats


164


″,


164


′″, lower retainers


124


″,


124


′″, casings


118


″,


118


′″, terminals


122


″,


122


′″, connectors


123


″,


123


′″, overmolds


128


″,


128


′″, upper retainers


126


″,


126


′″, upper seals


202


″,


202


′″ and caps


200


″.


200


′″ of the respective air assist fuel injectors


100


″,


100


′″ are also identical, whereas these parts are not identical in air assist fuel injectors


100


,


100


′. Hence, the respective poppets


162


″,


162


′″, legs


166


″,


162


′″, carbon damns


206


″,


206


′″, and seats


164


″,


164


′″ are the only parts that are not identical in the air assist fuel injectors


100


″,


100


′″. In alternative embodiments, the air assist fuel injectors


100


″,


100


′″ also have identical seats. As will be apparent, the description of the air assist fuel injectors


100


,


100


′ and the description of the method of assembling the air assist fuel injectors


100


,


100


′ is equally applicable to the air assist fuel injectors


100


″,


100


′″.




The air assist fuel injectors


100


,


100


′ utilize pressurized air to atomize low pressure fuel. When installed in an engine, the air assist fuel injectors


100


,


100


′ are located such that the atomized low pressure fuel that exits the air assist fuel injectors is delivered to the internal combustion chamber of an engine, i.e., the part of an engine in which combustion takes place, normally the volume of the cylinder between the piston crown and the cylinder head, although the combustion chamber may extend to a separate cell or cavity outside this volume. For example, as illustrated by

FIGS. 14 and 17

, the air assist fuel injector


100


is located in a cavity


704


of a two stroke internal combustion engine head


702


such that the air assist fuel injector can deliver a metered quantity of atomized liquid fuel to a combustion cylinder


703


of the two stroke internal combustion engine


700


, where it is ignited by a spark plug or otherwise. Likewise, as illustrated by

FIGS. 15 and 17

, the air assist fuel injector


100


′ is located in a cavity


704


′ of a four stroke internal combustion engine head


702


′ such that the air assist fuel injector can deliver a metered quantity of atomized liquid fuel to a combustion cylinder


703


′ of a four stroke internal combustion engine


700


′, where it is ignited by a spark plug or otherwise.




As illustrated by

FIGS. 14

,


15


, and


17


the air assist fuel injectors


100


,


100


′ are each located adjacent a conventional fuel injector


600


,


600


′. The fuel injector


600


is located at least partially in a cavity of an air/fuel rail


500


configured for the two stroke engine


700


, and the fuel injector


600


′ is located at least partially in a cavity of an air/fuel rail


500


′ configured for the four stroke engine


700


′. Examples of fuel injectors


600


,


600


′ that are suitable for delivering liquid fuel to the air assist fuel injectors include any top or bottom feed manifold port injector, commercially available from Bosch, Siemens, Delphi, Nippondenso, Keihen, Sagem, or Magneti Morelli. The air/fuel rails


500


,


500


′ each include one or more internal passageways or external lines (not illustrated) that deliver liquid fuel to the respective fuel injector


600


,


600


′, as well as one or more passageways


502


,


502


′ that deliver pressurized gas, preferably air, to the respective air assist fuel injector


100


,


100


′.




The air assist fuel injectors


100


,


100


′ are termed “air assist” fuel injectors because each preferably utilizes pressured air to atomize liquid fuel. In the preferred embodiments, the pressure of the air is at roughly 550 KPa for two stroke applications and at roughly 650 KPa for four stroke applications, while the pressure of the liquid fuel is roughly between 620-800 KPa. Although it is preferred that the air assist fuel injectors atomize liquid gasoline with-pressurized air delivered by the air/fuel rail, it will be realized that the air assist fuel injectors


100


,


100


′ may atomize many other liquid combustible forms of energy with any variety of gases. For example, the air assist fuel injectors


100


,


100


′ may atomize liquid kerosene or liquid methane with pressurized gaseous oxygen, propane, or exhaust gas. Hence, the term “air assist” is a term of art, and as used herein is not intended to dictate that the air assist fuel injectors


100


,


100


′ be used only with pressurized air.




Each rail


500


,


500


′ also defines a mount for the respective air assist fuel injector


100


,


100


′. That is, the respective air/fuel rail


500


,


500


′ abuts against at least one surface of the respective air assist fuel injector


100


,


100


′ to retain the air assist fuel injector in place in the respective cavities


704


,


704


′ of the respective heads


500


,


500


′. In an alternative embodiment not illustrated, an o-ring defines a seal between the air assist fuel injector and the air/fuel rail. Such an o-ring may be considered part of the air assist fuel injector


100


or the air/fuel rail


202


. The conventional fuel injectors


600


,


600


′ are configured and located such that they each deliver a metered quantity of liquid fuel directly to the inlet at the respective cap


200


,


200


′ of the air assist fuel injectors


100


,


100


′. Hence, each cap


200


,


200


′ receives the pressurized gas from the respective air/fuel rail


500


,


500


′ as well as the liquid fuel from the respective conventional fuel injector


600


,


600


′. Because of the proximity of the outlet of the respective fuel injector


600


,


600


′ with respect to the respective cap


200


,


200


′, the majority of the liquid fuel exiting from the respective fuel injector


600


,


600


′ will enter the respective fuel passageway


210


,


210


′ (see FIGS.


10


and


11


). The pressurized gas is delivered to the respective cap


200


,


200


′ via an annular passageway


501


,


501


′ in the respective air/fuel rail


500


,


500


′. The majority of the pressurized gas conveyed by the respective air/fuel rail


500


,


500


′ will thus enter the gas passageways


212


,


212


′ of the corresponding cap


200


,


200


′. Hence, each cap


200


,


200


′ functions as an inlet to the respective air assist fuel injector


100


,


100


′ for the pressurized gas and liquid fuel.




The pressurized gas and the liquid fuel mixture exits the respective cap


200


,


200


′ and then enters the respective armature


172


,


172


′ located immediately downstream of the corresponding cap with respect to the direction of flow f, f′. The liquid fuel and pressurized gas mix in the respective passageway


182


,


182


′ of each armature


172


,


172


′ and are conveyed to the respective inlet


182


,


182


′ of each poppet


162


,


162


′. Thereafter, the liquid fuel and gas travel through the respective tubular passageway


178


,


178


′ of each poppet


162


,


162


′. When the solenoid coil assemblies


120


,


120


′ are energized, the respective armature


172


,


172


′ overcomes the biasing force of the respective spring


170


,


170


′ and moves toward the corresponding leg


166


,


166


′ until it seats against the respective stop surface


167


,


167


′. Because each poppet


162


,


162


′ is attached to the respective armature


172


,


172


′, each head


174


,


174


′ of the respective poppet lifts off of the seat in the direction of flow f, f′ when the respective armature is actuated. When each head


174


,


174


′ lifts off of the respective seat


164


,


164


′, a seal between the head and the seat is broken and the gas and fuel mixture exits the outlets


176


,


176


′. The mixture exiting each set of outlets


176


,


176


′ is then forced out of each air assist injector


100


,


100


′ over the respective head


174


,


174


′ such that a metered quantity of atomized liquid fuel is delivered to the respective combustion chamber


703


,


703


′.




When the previously described solenoid coil assembly


120


,


120


′ is de-energized, the biasing force of the respective spring


170


,


170


′ returns the armature


172


,


172


′ to its original position. Because each poppet


162


,


162


′ is attached to the respective armature


172


,


172


′, the corresponding head


174


,


174


′ of each poppet


162


,


162


′ returns to the respective seat


164


,


164


′ to define a seal that prevents further gas and fuel from exiting the respective air assist fuel injector


100


,


100


′. Hence, the air assist fuel injectors


100


,


100


′ each atomize the liquid fuel supplied by the respective conventional fuel injector


600


,


600


′ with the pressurized gas supplied via the respective air/fuel rail


500


,


500


′. The atomized fuel is then delivered to the respective combustion chamber


703


,


703


′ of the respective engine


700


,


700


′, where it is ignited to power the respective engine


700


,


700


′.




One preferred embodiment of assembling the air assist fuel injector


100


is now described in reference to

FIGS. 12

,


13


,


16


, and


17


. As will be appreciated, the following assembly method is applicable to the air assist fuel injector


100


as well as the air assist fuel injector


100


′. Hence, the following description of one method of assembling the air assist fuel injector


100


is also one method of assembling the air assist fuel injector


100


′. As illustrated by

FIG. 16

, the assembly process begins by assembling the valve assembly


160


or the solenoid assembly


110


. The valve assembly


160


may also be assembled in parallel with the solenoid assembly


110


, i.e., at the same time.




First, considering the assembly of the valve assembly


160


, at a step


1000


, the armature guide


168


is fitted to the leg


166


, preferably by press-fitting the armature guide


168


onto the reduced portion of the leg


166


, at the upstream end of the leg


166


. Thereafter, at a step


1002


, the armature guide


168


and leg


166


combination are placed onto a fixture, such as a rotatable chuck, collet, sleeve, ferrule, etc. At a step


1004


, the seat


164


is fitted to the leg


166


, preferably by slip-fitting the seat


164


into a cavity in the downstream end of the leg


166


. As illustrated by

FIG. 16

, at a step


1006


, the seat


164


and the armature guide


168


are then attached to the leg


166


, preferably by one or more hermetic YAG laser welds, although other attachments are also contemplated as described earlier.




After the armature guide


168


and the seat


164


are attached to the leg


166


they are removed from the fixture, and, at a step


1008


, the upstream end (seat side) of the poppet


162


is inserted into the tubular passageway


178


of the leg


166


until the poppet head


174


abuts against the seat


164


. At a step


1010


, the spring


170


is then inserted into the annular area


171


between the poppet


162


and the interior surface of the leg


166


at the upstream end of the leg. Then, at a step


1012


, the armature


172


is fitted to the poppet, preferably by a press-fitting the armature over the proximal end of the poppet


162


. The armature


172


is press-fit to such an extent that the armature compresses the spring


170


and the armature abuts the stop surface


167


of the leg


166


. At a step


1014


, a pin or rod is inserted into the passageway


180


of the armature from the upstream side of the armature to push the poppet


162


back out of the armature


172


(in the direction of flow f) to set the stroke or lift of the armature, i.e., the amount of axial movement of the armature during operation. A dial indicator is used on the end of the poppet


162


to measure the stroke during step


1014


. After the stroke of the armature


172


, and thus the stroke of the poppet


162


, are set at step


1014


, the assembly of the valve assembly


160


is completed by attaching the poppet


162


to the armature


172


at a step


1016


, preferably by hermetically YAG laser welding the armature to the poppet, roughly at the intersection or joint between the passageway


180


and the inlet


182


of the poppet.




The assembly of the solenoid assembly


110


begins with assembling the solenoid coil assembly


120


. At a step


1018


, the solenoid coil assembly


120


is assembled by winding the conductor of the coil


114


on the bobbin


112


and attaching the ends


116


′ to the coil. The coil


128


can optionally be encapsulated in a insulative material after being wound on the bobbin


112


. At a step


1020


, the solenoid coil assembly


120


is encased, preferably by pressing the lower retainer


124


into the solenoid casing


118


, placing the solenoid coil assembly


120


into the casing


118


, pressing the top retainer


126


into the casing


118


, and then welding the retainers


124


,


126


to the casing


118


. In the preferred embodiment, the solenoid coil assembly


120


is preassembled, i.e., pre-manufactured, and thus the assembly of the solenoid assembly


110


begins at step


1020


.




At a step


1022


, the terminals


122


and/or the connectors


123


are attached to the ends


116


. At a step


1024


, the solenoid assembly


110


is completed by overmolding with the overmold


128


. To perform the overmold process retainers


124


,


126


are welded to the casing


118


. Connectors


123


are then welded to terminals


122


. Overmold


128


is formed by placing a mold around the solenoid assembly


110


. The mold die is placed around the solenoid assembly


110


to form the geometry of overmold


128


. Overmold


128


encapsulates the outer diameter of solenoid assembly


110


and seals off around connectors


123


.




After the valve assembly


160


and the solenoid assembly


110


are complete, at a step


1026


, the solenoid assembly is fitted to the valve assembly, preferably by pressing the solenoid assembly over the valve assembly. Then, at a step


1028


, the solenoid assembly is attached to the valve assembly, preferably by a laser weld. After the solenoid assembly


110


and the valve assembly


160


are attached, the upper seal


202


is placed. over the upstream end of the sleeve guide


168


and then, at a step


1030


, the cap


200


is fitted to the remainder of the injector, preferably by press-fitting the cap


200


into the upstream end of the armature guide


168


. To complete the assembly of the air assist fuel injector


200


, at a step


1032


, a lower seal


204


and a carbon dam


206


are positioned in place. In the preferred embodiment, the lower seal


204


is a viton O ring, and the carbon dam


206


is a Teflon dam.




Although

FIG. 16

illustrates the preferred method of assembly of the present invention, it will be appreciated that additional steps may be added and some of the previously described steps may be removed in alternative embodiments of the present invention, depending upon the specific configuration of the air assist fuel injector being assembled. Additionally, it will be appreciated that the order of the steps illustrated in

FIG. 16

can vary and still be within the confines of the present invention.




Because of the different configurations of the two stroke internal combustion engine


700


and the four stroke internal combustion engine


700


′, the air assist fuel injectors


100


,


100


′, as described above, have different external dimensions. Nevertheless, in accordance with the embodiments of the present invention, the air assist fuel injectors


100


,


100


′ are configured such that they share a number of identical parts. As illustrated in

FIG. 17

, these identical parts are stored in a common parts inventory


4000


when assembling the air assist fuel injectors


100


,


100


′ in the manner described above. When assembling the air assist fuel injectors


100


,


100


′, the common parts inventory


4000


includes one or more of the following: (1) an inventory of identical solenoid coil assemblies


120


,


120


′; (2) an inventory of identical armatures


172


,


172


′; and (3) an inventory of identical springs


170


,


170


′. The remainder of parts for the air assist fuel injector


100


that are not held in the inventory


4000


are stored in a two stoke air assist fuel injector inventory


4002


, and the remainder of parts for the air assist fuel injector


100


′ that are not held in the inventory


4000


are stored in a four stroke air assist fuel injector inventory


4004


. Hence, the two stroke air assist injector inventory


4002


for the two stroke air assist fuel injector


100


includes one or more of the following: carbon dam


206


, lower seal


204


, seat


164


, leg


166


, armature guide


168


, lower retainer


124


, casing


118


, terminal


122


, connector


123


, overmold


128


, upper retainer


126


, upper seal


202


, poppet


162


, and cap


200


. Likewise, the four stroke injector inventory


4004


for the four stroke air assist fuel injector


100


′ includes one or more of the following: carbon dam


206


′, lower seal


204


′, seat


164


′, leg


166


′, armature guide


168


′, lower retainer


124


′, casing


118


′, terminal


122


′, connector


123


′, overmold


128


′, upper retainer


126


′, upper seal


202


′, poppet


162


′ and cap


200


′.




Hence, when assembling the air assist fuel injector


100


as illustrated in

FIG. 16

, the solenoid coil assembly


120


, the armature


172


, and the spring


170


are retrieved from the common parts inventory


4000


and the remainder of the parts (carbon dam


206


, lower seal


204


, seat


164


, leg


166


, armature guide


168


, lower retainer


124


, casing


118


, terminal


122


, connector


123


, overmold


128


, upper retainer


126


, upper seal


202


, poppet


162


and cap


200


) for the air assist fuel injector are retrieved from the two stroke air assist fuel injector inventory


4002


. When assembling the air assist fuel injector


100


′, the solenoid coil assembly


120


′, the armature


172


′, and the spring


170


′ are retrieved from the common parts inventory


4000


and the remainder of the parts (carbon dam


206


′, lower seal


204


′, seat


164


′, leg


166


′, armature guide


168


′, lower retainer


124


′, casing


118


′, terminal


122


′, connector


123


′, overmold


128


′, upper retainer


126


′, upper seal


202


′, poppet


162


′ and cap


200


′) for the air assist fuel injector


100


′ are retrieved from the four stroke air assist fuel injector inventory


4004


.




In alternative embodiments, the common parts inventory


4000


also includes an inventory of one or more of the following: armature guides, casings, carbon dams, seats, lower retainers, upper retainers, and upper seals. For example, a common parts inventory for the air assist fuel injectors


100


″,


100


′″ illustrated in

FIGS. 18 and 19

includes identical solenoid coil assemblies, identical armatures


172


″,


172


′″, identical springs


170


″,


170


′″, identical armature guides


168


″,


168


′″, identical carbon dams


206


″,


206


′″, identical lower seals


204


″,


204


′″, identical lower retainers


124


″,


124


′″, identical casings


118


″,


118


′″, identical terminals


122


′,


122


′″, identical connectors


123


′,


123


′″, identical overmolds


128


″,


128


′″, identical upper retainers


126


″,


126


′″, identical upper seals


202


″,


202


′″ and identical caps


200


″.


200


′″. Hence, when assembling the air assist fuel injector


100


″, the remainder of parts (seat


164


″, leg


166


″, and poppet


162


″) for the air assist fuel injector


100


″ are retrieved from the two stroke air assist fuel injector inventory. Likewise, when assembling the air assist fuel injector


100


′″, the remainder of parts (seat


164


′″, leg


166


′″, and poppet


162


′″) for the air assist fuel injector


100


′″ are retrieved from the four stroke air assist fuel injector inventory.




As set forth above, the configuration of the two stroke engine


700


and the four stroke engine


700


′ dictate the external dimensions of the air assist fuel injectors


100


,


100


′. More specifically, two stroke engine applications have very tight height restrictions, requiring short air assist fuel injectors, while four stroke engine applications have very tight diameter restrictions, requiring long and very small diameter air assist fuel injectors. To satisfy the different dimensional requirements of these two applications, it was conventionally thought to separately manufacture two different air assist fuel injectors having no common parts. However, as set forth above, the embodiments of the present invention strive to address this problem by providing air assist fuel injectors


100


,


100


′ that share a number of common parts, especially the solenoid coil assembly


120


,


120


′ and/or armature


172


,


172


′. The solenoid coil assemblies


120


,


120


′ satisfy the strict dimensional requirements of many two stroke engine and four stroke engine applications, while still satisfying the functional design requirements of the air assist fuel injectors


100


,


100


′ for both applications. That is, each solenoid height h, h′ is small enough to fit two stroke engine applications, each solenoid diameter Ø, Ø′ is small enough to fit four stroke applications, and the configuration of each solenoid assembly


110


,


110


′ is sufficient to actuate the different length and weight armature/poppet combinations of the two air assist fuel injectors


100


,


100


′. Hence, the air assist fuel injector


100


is short enough to satisfy two stroke engine applications and the air assist fuel injector


100


′ is long and narrow enough to satisfy four stroke engine applications, while the solenoid assembly


110


,


110


′ of each air assist fuel injector is sized and configured to fit both two stroke and four stroke applications; this significantly simplifies the manufacture of the air assist fuel injectors


100


,


100


′ as compared to conventional air assist fuel injectors configured for the same applications.




The principles, preferred embodiments, and modes of operation of the present invention have been described in the foregoing description. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims be embraced thereby.



Claims
  • 1. An assembly of items comprising:a first air assist fuel injector configured for a two stroke internal combustion engine, said first air assist fuel injector having a solenoid assembly, a poppet, a poppet seat, and an armature attached to said poppet; and a second air assist fuel injector configured for a four stroke internal combustion engine, said second air assist fuel injector having a solenoid assembly, a poppet, a poppet seat, and an armature attached to said poppet of said second air assist fuel injector; said solenoid assembly of said first air assist fuel injector and said solenoid assembly of said second air assist fuel injector being identical, said armature of said first air assist fuel injector and armature of said second air assist fuel injector being identical, said poppet of said first air assist fuel injector being shorter than said poppet of said second air assist fuel injector as measured along a longitudinal axis of said poppet of said first air assist fuel injector and as measured along a longitudinal axis of said poppet of said second air assist fuel injector.
  • 2. An assembly of items comprising:a first air assist fuel injector configured for a two stroke internal combustion engine, said first air assist fuel injector having a solenoid assembly and a poppet, said poppet having a length as measured along a longitudinal axis of said poppet; and a second air assist fuel injector configured for a four stroke internal combustion engine, said second air assist fuel injector having a solenoid assembly and a poppet, said poppet of said second air assist fuel injector having a length as measured along a longitudinal axis of said poppet of said second air assist fuel injector, said length of said poppet of said first air assist fuel injector being shorter than said length of said poppet of said second air assist fuel injector, said solenoid assembly of said first air assist fuel injector and said solenoid assembly of said second air assist fuel injector being identical.
  • 3. The assembly of items of claim 2,said solenoid assembly of said first air assist fuel injector and said solenoid assembly of said second air assist fuel injector each including a casing and a cylindrical coil of wire wound on a bobbin, said casing of said first air assist fuel injector housing said cylindrical coil and said bobbin of said first air assist fuel injector, said casing of said second air assist fuel injector housing said cylindrical coil and said bobbin of said second air assist fuel injector.
  • 4. The assembly of items of claim 3, said solenoid assembly of first air assist fuel injector and said solenoid assembly of second air assist fuel injector each including an overmold, each of said overmolds having a height h of substantially 20 millimeters and a diameter of substantially 20 millimeters.
  • 5. The assembly of items of claim 3,said first air assist fuel injector including an armature attached to said poppet of said first air assist fuel injector, said second air assist fuel injector including an armature attached to said poppet of said second air assist fuel injector, said armature of said first air assist fuel injector and said armature of said second air assist fuel injector being identical.
  • 6. The assembly of items of claim 5,said first air assist fuel injector having an armature guide for guiding movement of said armature of said first air assist fuel injector, said armature guide having a first end located upstream of said armature of said first air assist fuel injector with respect to a direction of flow of a mixture of liquid fuel and gas through said second air assist fuel injector and a second end located downstream of said armature of said first air assist fuel injector with respect to said direction of flow of said mixture through said second air assist fuel injector, said second air assist fuel injector having an armature guide for guiding movement of said armature of said second air assist fuel injector, said armature guide of said second air assist fuel injector guide having a first end located upstream of said armature of said second air assist fuel injector with respect to a direction of flow of a mixture of liquid fuel and gas and a second end located downstream of said armature of said second air assist fuel injector with respect to said direction of flow of said mixture, said armature guide of said first air assist fuel injector and said armature guide of said second air assist fuel injector being identical.
  • 7. The assembly of items of claim 2, in combination with said two stroke internal combustion engine.
  • 8. The assembly of items of claim 7, said two stroke internal combustion engine having a head, said head having an opening that receives at least a portion of said first air assist fuel injector.
  • 9. The assembly of items of claim 2, in combination with said four stroke internal combustion engine.
  • 10. The assembly of items of claim 9, said four stroke internal combustion engine having a head, said head having an opening that receives at least a portion of said second air assist fuel injector.
  • 11. An assembly of items comprising:a first air assist fuel injector configured for a two stroke internal combustion engine, said first air assist fuel injector having a poppet and an armature attached to said poppet, said poppet having a length as measured along a longitudinal axis of said poppet; and a second air assist fuel injector configured for a four stroke internal combustion engine, said second air assist fuel injector having a poppet and an armature attached to said poppet, said poppet of said second air assist fuel injector having a length as measured along a longitudinal axis of said poppet of said second air assist fuel injector, said length of said poppet of said first air assist fuel injector being shorter than said length of said poppet of said second air assist fuel injector, said armature of said first air assist fuel injector and said armature of said second air assist fuel injector being identical.
  • 12. The assembly of items of claim 11,said first air assist fuel injector having an armature guide for guiding movement of said armature of said first air assist fuel injector, said armature guide having a first end located upstream of said armature of said first air assist fuel injector with respect to a direction of flow of a mixture of liquid fuel and gas through said first air assist fuel injector and a second end located downstream of said armature of said first air assist fuel injector with respect to said direction of flow of said mixture, said second air assist fuel injector having an armature guide for guiding movement of said armature of said second air assist fuel injector, said armature guide of said second air assist fuel injector guide having a first end located upstream of said armature of said second air assist fuel injector with respect to a direction of flow of a mixture of liquid fuel and gas through said second air assist fuel injector and a second end located downstream of said armature of said second air assist fuel injector with respect to said direction of flow of said mixture through said second air assist fuel injector, said armature guide of said first air assist fuel injector and said armature guide of said second air assist fuel injector being identical.
  • 13. The assembly of items of claim 11, in combination with said two stroke internal combustion engine.
  • 14. The assembly of items of claim 13, said two stroke internal combustion engine having a head, said head having an opening that receives at least a portion of said first air assist fuel injector.
  • 15. The assembly of items of claim 11, in combination with said four stroke internal combustion engine.
  • 16. The assembly of items of claim 15, said four stroke internal combustion engine having a head, said head having an opening that receives at least a portion of said second air assist fuel injector.
  • 17. An assembly of items comprising:a first air assist fuel injector configured for a two stroke internal combustion engine, said first air assist fuel injector having a poppet, an armature attached to said poppet, and an armature guide for guiding movement of said armature, said armature guide having a first end located upstream of said armature with respect to a direction of flow of a mixture of liquid fuel and gas through said first air assist fuel injector and a second end located downstream of said armature with respect to said direction of flow of said mixture, said poppet having a length as measured along a longitudinal axis of said poppet; and a second air assist fuel injector configured for a four stroke internal combustion engine, said second air assist fuel injector having a poppet, an armature attached to said poppet of said second air assist injector, and an armature guide for guiding movement of said armature of said second air assist fuel injector, said armature guide of said second air assist fuel injector guide having a first end located upstream of said armature of said second air assist fuel injector with respect to a direction of flow of a mixture of liquid fuel and gas through said second air assist fuel injector and a second end located downstream of said armature of said second air assist fuel injector with respect to said direction of flow of said mixture through said second air assist fuel injector, said poppet of said second air assist fuel injector having a length as measured along a longitudinal axis of said poppet of said second air assist fuel injector, said length of said poppet of said first air assist fuel injector being shorter than said length of said poppet of said second air assist fuel injector, said armature guide of said first air assist fuel injector and said armature guide of said second air assist fuel injector being identical.
  • 18. The assembly of items of claim 17,said armature of said first air assist fuel injector and said armature of said second air assist fuel injector being identical.
  • 19. The assembly of items of claim 17, in combination with said two stroke internal combustion engine.
  • 20. The assembly of items of claim 19, said two stroke internal combustion engine having a head, said head having an opening that receives at least a portion of said first air assist fuel injector.
  • 21. The assembly of items of claim 17, in combination with said four stroke internal combustion engine.
  • 22. The assembly of items of claim 21, said four stroke internal combustion engine having a head, said head having an opening that receives at least a portion of said second air assist fuel injector.
  • 23. An assembly of items comprising:a first air assist fuel injector configured for a two stroke internal combustion engine, said first air assist fuel injector having a solenoid assembly and a poppet, said poppet having a length as measured along a longitudinal axis of said poppet, said solenoid assembly having a diameter and a length as measured along a center axis of said solenoid assembly; and a second air assist fuel injector configured for a four stroke internal combustion engine, said second air assist fuel injector having a solenoid assembly and a poppet, said poppet of said second air assist fuel injector having a length as measured along a longitudinal axis of said poppet of said second air assist fuel injector, said solenoid assembly of said second air assist fuel injector having a diameter and a length as measured along a center axis of said solenoid assembly of said second air assist fuel injector, said length of said poppet of said first air assist fuel injector being shorter than said length of said poppet of said second air assist fuel injector, said diameter of said solenoid assembly of said first air assist fuel injector being substantially the same as said diameter of second solenoid assembly of said second air assist fuel injector, said length of said solenoid assembly of said first air assist fuel injector being substantially the same as said length of second solenoid assembly of said second air assist fuel injector.
  • 24. The assembly of items of claim 23, said diameter of said solenoid assembly of said first air assist fuel injector being 20 mm.
  • 25. The assembly of items of claim 24, said length of said solenoid assembly of said first air assist fuel injector being 20 mm.
  • 26. The assembly of items of claim 23, said length of said solenoid assembly of said first air assist fuel injector being 20 mm.
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