System and method for delivering combustible liquids

Information

  • Patent Grant
  • 6675775
  • Patent Number
    6,675,775
  • Date Filed
    Wednesday, April 10, 2002
    22 years ago
  • Date Issued
    Tuesday, January 13, 2004
    20 years ago
Abstract
A fuel injector includes a drop ejector for discretely ejecting drops of combustible liquid in a digital manner. An electronic circuit controls the operation of the drop ejector, and, in particular, the amount of fuel supplied by the drop ejector by adjusting the number of ejected drops during a given time frame.
Description




BACKGROUND




The present invention generally relates to engine fuel systems and, more particularly, to combustible fuel devices that generate combustible vapors such as internal combustion engines.




Heretofore, combustible vapors were directed into the cylinders of internal combustion engines using either carburetors or fuel injectors. Fuel injectors were either continuous or pulsed. The continuous fuel injectors directed the combustible vapor into an intake manifold, and when an intake valve opened, the vapor was drawn into the cylinder by the piston. The pulsed fuel injectors directed fuel vapor on command into either a region upstream of each intake valve or directly into the combustion chambers. Both of these fuel delivery systems are highly developed, well known, and have been in use for decades.




As environmental regulations become more and more stringent, there is an increasing need for more precise control of the fuel/air stoichiometry in the combustion chambers of an engine. Several problems continue to persist in conventional fuel delivery technology. For instance, if excessive fuel is used or too little air is mixed with the fuel, the amount of hydrocarbon emissions increases correspondingly. Also, for fuel injectors, the orifices change in size over time; they get larger due to mechanical wear and smaller due to clogging from both the constituents in the fuel and small particles that are not removed by the fuel filter. In addition, the requirement for more precise fuel and air metering to meet environmental and fuel economy regulations has caused both carburetors and fuel injectors to become more and more expensive.




There is also a need for an inexpensive, simple fuel delivery system for small industrial engines, those having about twenty-five horsepower or less. These are the engines used on lawn mowers, rotary tillers, outboards and scooters, for example. These engines are increasingly being subject to environmental regulation, but it is impractical to incorporate a conventional fuel delivery system that costs as much or more than the rest of the machine.




Further, with these conventional fuel delivery systems, reliability continues to be a problem. For example, a conventional fuel injection system requires high-pressure pumps and carefully engineered fuel conduits, tubing, and connections that must withstand constant vibration and extreme variations in operating temperature.




It is apparent from the foregoing that although there are well-developed engine fuel delivery systems, there is a need for an approach that meets increasingly stringent environmental regulations, is reliable and inexpensive, and more precisely controls the fuel-air stoichiometry in combustion chambers.




SUMMARY




Briefly and in general terms, an apparatus according to the invention includes (i) a drop ejector capable of discretely ejecting a combustible liquid in a digital manner, and (ii) a means for providing a pulse-modulated control signal to said drop ejector, wherein said pulse-modulated control signal is indicative of a desired number of drops to be ejected from said drop ejector within a given time frame.




Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.











BRIEF DESCRIPTION OF THE DRAWINGS




The invention is better understood with reference to the following drawings. The elements of the drawings are not necessarily to scale relative to each other. Rather, emphasis has instead been placed upon clearly illustrating the invention. Furthermore, like reference numerals designate corresponding similar parts through the several views.





FIG. 1

is a is a block diagram of an exemplary embodiment of the invention.





FIG. 2

is a top, side and perspective view, partially diagrammatic, of an apparatus for generating a combustible vapor for an internal combustion engine according to an exemplary embodiment of the invention.





FIG. 3

is a bottom, side and perspective view, partially diagrammatic of the apparatus of FIG.


2


.





FIG. 4

is an exploded view, partially diagrammatic, of the apparatus of FIG.


2


.





FIGS. 5-8

are perspective views of some of the components of the apparatus of FIG.


2


.





FIG. 9

is an exploded view of the micro-pump of the apparatus of FIG.


2


.





FIG. 10

is a perspective view, partially cut away, of the apparatus of FIG.


2


.





FIG. 11

illustrates an exemplary pulse train used to control an amount of fuel ejected from an embodiment of the invention.





FIG. 12

is a block diagram of the signals and the electrical control circuit illustrated in FIG.


1


.











DETAILED DESCRIPTION





FIG. 1

is a block diagram of one embodiment of the invention. Reference numeral


14


generally indicates an apparatus for generating a combustible vapor for an internal combustion engine, hereinafter called a “fuel injector” for brevity. A fuel injector


14


includes a drop ejector


30


and an airflow control valve


34


. The drop ejector


30


creates discrete numbers of drops of a substantially fixed quantum of size. The drop ejector


30


is fluidically connected, preferably under low pressure, to a fuel reservoir


18


containing combustible fuel. The fuel from the fuel reservoir


18


is preferably delivered to the drop ejector using a pressure regulator


32


and an operational standpipe


36


to prevent fuel leakage from the drop ejector


30


in non-use-situations. Preferably, the drop ejector


30


is removable and replaceable by a typical consumer. A control circuit


20


controls the drop ejector


30


and airflow control valve


34


. The control circuit


20


is preferably connected to a throttle


23


, which is controlled by a user, and a load sensor


27


that monitors and senses the load of the combustible fuel device. The airflow control valve


34


regulates the flow of air that is mixed with the fuel ejected from the drop ejector


30


to create a combustible vapor


17


used by the internal combustion engine or other combustible fuel device.





FIGS. 2-10

illustrate various views and perspectives of an embodiment of the present invention, which includes additional details of the fuel injector


14


relative to the block diagram of FIG.


1


. Referring first to

FIGS. 2 and 3

, the fuel injector


14


has a main body


15


that is mounted either on an intake manifold


16


or proximate to the intake valves (not shown) of an internal combustion engine. The main body


15


and all of the parts, unless noted otherwise in this document, are preferably made of Nylon 6, an injected molded polymer that is resistant to gasoline and other engine fuels. The fuel injector can be used on either 2 cycle or 4 cycle spark ignition engines or 2 cycle or 4 cycle compression ignition engines. A function of the fuel injector is to produce very small, metered quantum or digital drops of combustible fuel and to channel a controlled amount of air through the drops and thereby generate a combustible vapor


17


. The combustible vapor


17


is drawn into the cylinders of the engine by either the vacuum created by the motion of the piston(s) or by an exterior air pump, not shown, such as a supercharger and/or a turbocharger.




In

FIGS. 2 and 3

, connected to the main body


15


is a fuel reservoir


18


. The fuel reservoir may or may not be connected to a fuel pump (not shown) but gravity feed of the fuel is inexpensive and is preferable because only a minimal fuel pressure is required for the fuel injector. The fuel can be any type of gasoline, Diesel fuels, alcohols, fuel oils and kerosenes, in short, any combustible fuel or fuel combination that will power an internal combustion engine or other combustible fuel device such as lanterns, stove, heaters and generators.




In

FIGS. 2 and 3

, the fuel injector


14


is connected to electronic control module


20


. This module


20


and its functions are described below in connection with FIG.


12


. Reference numeral


22


indicates a throttle cable that is connected to either a manual throttle or a foot pedal (not shown). As described below, when the throttle cable


22


is pulled away from the main body


15


, the fuel injector


14


channels a greater volume of air through the apparatus and into the engine. A conventional air filter


24


removes any particulate matter in the air stream entering the fuel injector


14


thus filtering the air.




Referring to

FIG. 9

, reference numeral


26


generally indicates a slide body, preferably replaceable, that functions both as a micro-pump for the fuel and an air control valve that regulates the amount of air that is directed into the stream of fuel droplets produced by the micro-pump. The slide body


26


is constructed similar to and operates in essentially the same manner as a thermal ink jet print cartridge. However, the various properties of the desired fuel used, such as surface tension, chemical reactivity, and volatility, to name a few, require that modifications be made to the design of conventional thermal ink jet print cartridges and thus prevents simple replacing ink with fuel. Such changes include reducing the capillary sizes in the standpipe


36


between the backpressure regulator


32


and the drop ejector


30


to account for a lower surface tension. Other changes include selection of materials for the body


15


and backpressure regulator


32


that are resistant to the fuel's solubility, such as Nylon 6. Further, the backpressure regulation must be adapted to account for the higher volatility of the fuel.




In this exemplary embodiment, the slide body


26


includes a housing


28


, upon which is mounted a TAB circuit


29


. Other forms of interconnection are known to those skilled in the art and can be substituted for the TAB circuit


29


and still remain within the spirit and scope of the invention. The TAB circuit


29


is electrically connected to the electronic control module


20


described below in connection to FIG.


12


. The TAB circuit


29


is also electrically and physically connected to drop ejector


30


located on the bottom wall of the housing


28


. An exemplary drop ejector is described in U.S. Pat. No. 6,162,589 entitled “Direct Imaging Polymer Fluid Jet Orifice” issued on Dec. 19, 2000 to Chen et al, and herein incorporated by reference. A preferred drop ejector


30


contains a plurality of fuel firing chambers; each firing chamber has one or more nozzles, a fuel inlet channel, and an energy dissipation element, such as a resistor or flextentional device that is pulsed by the electronic control module


20


. The electronic control module


20


is preferably responsive to engine load and throttle position when embodied in an internal combustion engine application. The drop ejector


30


expels the combustible liquid drop-by-drop for each orifice vertically downward (in this embodiment, although any orientation is possible) from the firing chambers as illustrated in

FIGS. 1

,


4


and


9


. For gasoline, the drops preferably each have a Number Median Diameter (NMD) of less than about 30 microns and a volume of about 14 picoliters, although this can be tailored depending on the design of the drop ejector such as up to an NMD of 1 mm.




Within the housing


28


of

FIG. 9

is a pressure regulator


32


that can be either reticulated foam, as illustrated, or a spring bag or a flexible diaphragm. Several other pressure regulators for controlling back pressure are known to those skilled in the art and can be substituted and still fall within the scope and spirit of the invention. The pressure regulator


32


is in fluid communication with the drop ejector


30


through a slot or slots in the standpipe (not shown) located in the bottom of the housing


28


. The pressure regulator places a slight negative pressure on the backside of the drop ejector


30


so that the combustible fluid does not leak or dribble out of the drop ejector.




The slide body


26


of

FIG. 9

also includes a slide body top


35


, and the housing


28


and the top


35


are sealed with a gasket


33


so that the combustible liquid does not leak out of the slide body. The gasket is preferably made from EPDM or polyurethane. On the top wall of the slide body top


35


are two cylindrical features


37


that retain the compression return springs


46


(

FIG. 4

) in place and an arch


40


. The throttle cable


22


(

FIG. 2

) is connected to the arch


40


as described below, and the motion of the throttle cable causes the slide body


26


to move vertically up and down within a slot


38


(

FIG. 7

) within the main body


15


of the fuel injector to control the amount of air entering the fuel injector through airway


85


(see FIG.


7


).




Also located on the top wall of the slide body


26


(see

FIG. 9

) is a combustible fuel inlet conduit


41


that is in fluid communication with the fuel reservoir


18


(FIG.


2


). Within the main body


15


, the fuel inlet conduit


41


is flexible and resiliently deformable so that the slide body


26


can move up and down within the fuel injector without obstruction. The fluid inlet conduit


41


is also in fluid communication with the pressure regulator


32


(FIG.


8


).




Referring to

FIGS. 8 and 10

, reference numeral


43


indicates a rearward portion of the top wall of the main body


15


. Located on the bottom side of this wall


43


(

FIG. 8

) are two spaced apart cylindrical features


44


. After assembly of the fuel injector, these cylindrical features


44


are co-axial with the cylindrical features


37


on the slide body top


35


(FIG.


9


). The four features together engage and retain two return springs


46


(FIG.


4


). The return springs


46


are compression springs and are preferably fabricated from stainless steel. The return springs urge the slide body


26


downward into the main body


15


and into a position that blocks the flow of air through the fuel injector


14


. When the slide body


26


is pulled upward by the throttle cable


22


, the return springs


46


are compressed. Also located on the bottom side of the top wall


43


is a guide


45


for the throttle cable


22


,


54


. The function of the guide


45


is to make the throttle cable bend


54


, as illustrated in

FIGS. 3 and 9

. For clarity, the guide


45


is not illustrated in

FIGS. 4 and 10

.




Referring to

FIG. 6

, reference numeral


48


generally indicates a throttle wheel. The throttle wheel has a smaller spool


49


and a larger spool


50


rigidly mounted on an axle


51


. The throttle cable


22


(FIG.


2


), connected to the throttle, not shown, passes through a small hole


53


(

FIG. 7

) in the main body


15


and is wrapped around the larger spool


50


. There is a second cable


54


that is wrapped around the smaller spool


49


. The second cable


54


passes through the guide


45


(

FIG. 8

) and is connected to the arch


40


on the slide body top


35


(FIG.


9


). The function of the two spools


49


,


50


, of different diameters is to reduce the overall height of the fuel injector


14


. Also, connected to the axle


51


is a throttle position sensor


52


, preferably a potentiometer. This sensor measures the radial position of the throttle wheel


48


that corresponds to the vertical position of the slide body


26


within the fuel injector


14


. The sensor sends a position signal


68


to the control circuit (see

FIG. 12

) described below. The throttle wheel


48


is mounted for rotation on four forks


56


in

FIGS. 4 and 6

. Two of the forks


56


are located on the bottom of the forward portion


57


of the top wall of the main body


15


. The other two forks


48


are located on a medial wall


58


within the main body


15


.




According to a preferred embodiment of the invention, the amount of fuel delivered from the fuel injector is controlled by adjusting the number of fuel drops that are delivered by the fuel injector for a given fixed time period. Thus, the fuel drops are delivered according to a pulse-modulated scheme.

FIG. 11

illustrates an exemplary pulse-modulated fuel drop delivery scheme according to a preferred embodiment of the present invention. As shown in

FIG. 11

, a pulse stream is established wherein a fuel drop is delivered from the fuel injector for each pulse in the pulse stream. For any given fixed time frame τ


1


, a variable number of pulses (n) can be applied. Each pulse has a fixed period of τ


2


, which represents the time period during which the fuel injector is delivering one or more fuel droplets of a fixed quantum size.

FIG. 11

illustrates three different time frames, each having a period of τ


1


. In the first time frame, two pulses are applied; in the second time frame, six pulses are applied; and in the third time frame, eight pulses are applied. The greater the number of pulses in a given time frame, the more fuel that is delivered from the fuel injector, and thus, the richer the fuel/air mixture that is delivered to the engine. In this way, a preferred method of controlling the amount of fuel delivered from the fuel injector is according to a pulse-modulated scheme.





FIG. 12

illustrates an exemplary electronic control circuit and the flow of signals within the electronic control module


20


(

FIG. 1

) that implements the above-described methodology for controlling the amount of fuel delivered to the engine. The electronic control circuit may be designed and built using analog, digital, or any combination thereof of electrical circuits, including microprocessors. The circuit includes a twelve-volt DC power supply


60


that supplies power to all of the electronics for the fuel injector


14


. The power supply may be a battery or a generator driven by the engine. Arrows


61


-


65


inclusive indicate the twelve-volt DC power distributed to the various sub-circuits.




The throttle wheel


48


illustrated in

FIGS. 6 and 10

turns in response to the movement of the throttle cable


22


,


54


, and the position of the axle


51


is indicated by the arrow


67


. The radial position of the throttle wheel


48


and, in turn, the vertical location of the slide body


26


(FIG.


9


), within the main body


15


is measured by the throttle position sensor


52


, typically and preferably a positioning potentiometer. Arrow


68


is a variable voltage corresponding to the vertical position of the slide body


26


in the fuel injector, and, in turn, the size of the opening of the airway in the fuel injector. This variable voltage is an input to an electronic controller


76


.




Reference numeral


72


of

FIG. 12

indicates an engine load sensor. The load sensor


72


can take many forms depending on the application. In one application, the load sensor


72


is a tachometer that measures the revolutions per minute of the engine. In another application, the load sensor


72


is an airflow meter that measures the quantity of air entering the fuel injector. On an air-cooled engine, the load sensor


72


is a flow meter measuring the amount of air being moved by the fan. The output voltage signal from the engine load sensor


72


is indicated by arrow


73


and is a second input to the electronic controller


76


.




The electronic controller


76


controls the amount of combustible fuel that is ejected from the drop ejector based upon the input signals


68


and


73


from the throttle position sensor


52


and the engine load sensor


72


, respectively. Further, while not shown in

FIG. 12

, other parameters known in the art to be relevant to the desired amount of fuel to be supplied to an engine can also be used as inputs to the electronic controller


76


for this purpose. Collectively, the engine load, throttle position, and other known parameters are referred to herein as “operation conditions” of the apparatus receiving the fuel delivery. Generally, the higher the engine load and/or the more that the throttle is actuated, the greater the amount of fuel that should be ejected from the drop ejector


30


. Thus, the greater the desired number of drops that should be ejected from the drop ejector


30


within a given time frame τ


1


. The electronic controller


76


and the pulse counter


79


create a pulse train appropriate to eject the desired number of fuel drops within a given time frame.




The electronic controller


76


provides a frame clocking signal


96


to pulse counter


79


every τ


1


seconds. In this way, the period between frame clocking signals is τ


1


. The frame clocking signal


96


functions to trigger the pulse counter


79


. Controller


76


also provides a τ


2


clocking signal


95


to pulse counter


79


every τ


2


seconds. As a result, a pulse train is established having a period of τ


2


. Finally, controller


76


provides a load counter signal


77


to pulse counter


79


, which represents the number of fuel drops that should be ejected from the drop ejector


30


. Based upon the load counter signal


77


, the pulse counter


79


provides a certain number (n) of pulses


80


to drive circuits


91


. In operation, the frame clocking signal


96


triggers the pulse counter


79


, which, in turn, passes a pulse to the drive circuits


91


each time the pulse counter


79


receives a τ


2


clocking signal. The pulse counter


79


continues this process until it has delivered (n) pulses, at which time it stops providing pulses until it receives the next frame clocking signal


96


.




The pulses


80


are provided to drive circuits


91


, which amplify the pulses


80


sufficiently to activate the drop ejector


30


. Each time the drop ejector receives a pulse, it ejects a drop of fuel. Thus, the more pulses that the drop ejector receives during a given fixed time period τ


1


, the greater the amount of fuel that is delivered to the engine.




Now, a preferred operation of the system will be described in more detail. In operation, the flow path of air through the fuel injector


14


(

FIG. 2

) begins at the air filter


24


. Air is drawn into the fuel injector either by an air pump (not shown) or by the vacuum created by the motion of the pistons in the engine. Air flows through the air filter


24


, down the airway


85


(

FIG. 7

) in the main body


15


, beneath the drop ejector


30


(

FIGS. 4 and 9

) on the slide body


26


, out of the main body


15


, and into the intake manifold


16


(FIG.


2


). The airflow is from right to left in FIG.


2


.




The flow path of the combustible liquid begins at the fuel reservoir


18


(FIG.


2


). The liquid flows in a low pressure conduit (e.g. less than about 3 psi) from the reservoir to the main body


15


, then through a resiliently deformable conduit at a low pressure (e.g. again less than about 3 psi) to the fuel inlet


41


on the slide body


26


(FIG.


9


). The liquid flows through the pressure regulator


32


, through several slots in the standpipe (not shown) in the bottom of the housing


28


to the drop ejector


30


. The exemplary pressure regulator, preferably foam, maintains a slight negative pressure (relative to gauge thus creating a backpressure) at the back of the drop ejector so that the combustible liquid does not drool or run out of the drop ejector


30


during non-use. The liquid fuel is drawn out of the foam and into the drop ejector because of the capillary action of the fluid within the drop ejector and standpipe slots to replace the ejected volume. The drop ejector


30


fires the liquid drop-by-drop vertically downward into a fast flow of air channeled beneath the slide body


26


. When the drops reach the air stream, their flight path changes from vertical to horizontal in this example. The drops are sufficiently small due to their discretely ejected quantum size. The airflow is designed such that mixing occurs between the air and the quantum drops of fuel, and a combustible vapor


17


(

FIG. 2

) is formed.




Referring to

FIG. 10

, motion of throttle cable


22


, as indicated by the arrow


87


, causes the throttle wheel


48


to rotate, as indicated by the arrow


88


, and the slide body


26


to move up and down, as indicated by the arrow


89


. The slide body


26


normally sits at the bottom of the slot


38


(FIG.


7


), blocking the airway


85


and is urged downward by the return springs


46


(FIG.


4


). When the throttle cable


22


is pulled away from the main body


15


, the cable


22


causes the throttle wheel


48


to rotate and, in turn, pull the slide body


26


upward with the second throttle cable


54


. The second throttle cable passes through the guide


45


(

FIG. 8

) and its motion is redirected from horizontal to vertical as illustrated in FIG.


10


. The second throttle cable is attached to the arch


40


on the slide body top wall


35


(FIG.


9


). When the slide body moves upward, more of the airway


85


is uncovered and more air is permitted to flow into the fuel injector


14


. In addition, the return springs


46


are compressed. The rotation of the throttle wheel


48


also actuates the throttle position sensor


52


that sends a signal


68


to the electronic control module


20


indicating that more of the airway


85


is open and more air is flowing into the fuel injector.




Referring to the circuit in

FIG. 12

, when the throttle cable


22


(

FIG. 2

) is pulled away from the fuel injector, the output signal


68


from the throttle position sensor


52


increases. In turn, the electronic controller


76


increases load counter output signal


77


, which is indicative of the number of fuel drops (n) to be ejected from the drop ejector


30


. The higher load counter output signal


77


causes the pulse counter


79


to provide more pulses


80


to the drive circuits


91


within the given time frame τ


1


. Accordingly, the drive circuits


91


provide more pulses to the drop ejector


30


, thus resulting in more fuel drops being ejected from the drop ejector


30


, and ultimately more fuel being provided to the engine.




When the engine is running at steady state and an increased load is placed on the engine, the speed of the engine slows and also the flow of air through the fuel injector decreases. Either the decrease in revolutions of the engine or the decrease in airflow or both are sensed by the engine load sensor


72


and the output voltage signal


73


from the engine load sensor


72


changes to reflect the increased load. Based upon the increased input voltage


73


, the electronic controller


76


increases the load counter output signal


77


, indicative of the number of fuel drops to eject. As more combustible liquid is ejected into the air stream, the engine typically produces more torque up to a certain point where the combustible mixture becomes too rich, and it does not increase torque any longer. This process all occurs without moving the throttle cable


22


. Alternatively, the load sensor may also affect the throttle position. If the increased load is removed, the engine typically speeds up since excess power is being generated, and the circuit operates to reduce the number of fuel drops ejected during the next time frame τ


1


. This is just the reverse of the process described immediately above.




Referring to

FIG. 12

, the electronic controller


76


receives inputs


68


and


73


from the throttle position sensor


52


and engine load sensor


72


, respectively, which, in turn, causes the circuit to increase or decrease the number of fuel drops ejected from the drop ejector


30


. In particular, at steady state, the position of the slide body


26


(

FIG. 10

) within the fuel injector determines the primary stoichiometric ratio of the air stream and the air charge going into the engine. During acceleration and deceleration, the controller


76


modifies the stoichiometric ratio based on the signal from the load sensor


27


.




Under conditions of a very small load, as the slide body


26


opens the airway


85


, more air is permitted to enter the fuel injector


14


. Because there is very little load on the engine, the speed of the engine responds very quickly, and the revolutions of the engine come up to speed very easily. In this situation of low load, the output signal


73


from the engine load sensor


72


has very little affect on the number of fuel drops ejected from the drop ejector


30


during any given time period τ


1


.




Under conditions of increased load—as the engine load increases and without changing the throttle position—the output voltage signal


73


from the engine load sensor


72


changes the voltage input to the controller


76


. In response, the electronic controller


76


causes the load counter signal


77


, i.e., the number of desired fuel drops (n), to increase. More drops of combustible liquid are injected into the air stream, and the stoichiometric ratio is changed to increase the torque produced by the engine. The engine thus responds to the load, and equilibrium is reestablished.




The inventive apparatus offers an inexpensive, simple, reliable, electro-mechanical fuel delivery system for precisely controlling the fuel/air stoichiometry in the cylinders of an internal combustion engine or other combustible fuel devices such as lamps, stoves, generators and portable heaters to name a few. The inventive apparatus has the capability of precisely metering how much fuel is being delivered to the cylinders or devices with a resolution in a range of nanograms because both the size and weight of the drops of fuel being delivered by the micro-pump are precisely controlled in a discrete drop-by-drop manner. These features allow the engine or device to reduce the amount of hydrocarbons released into the atmosphere, in particular during start-up, and to meet increasingly stringent environmental regulations. The apparatus differs from conventional fuel injectors in that rather than forming a spray of fuel having varying drop sizes, a drop-by-drop generator in the micro-pump creates one or more quantums of fuel in fixed sized drops that are discretely ejected and that are readily vaporized when mixed with air. This ability to provide a fixed amount of fuel made up of a various amount of quantum sized drops creates a method of digitally delivering fuel to an engine, thus allowing for enhanced automated and preferably computerized control. By being able to efficiently blend the fuel and air, one benefit is that for a given application, lower grade fuels may be used thus leading to further economy.




In addition, the apparatus includes a low pressure, e.g. less than about 3 pounds per square inch, fuel supply system. This low-pressure fuel supply system operates far below the high pressures found in conventional fuel injection systems. The drop ejector includes micro nozzles and capillary channels within a standpipe that are custom designed and sized for the type of fuel used. By adding a back pressure regulator between the drop ejector/standpipe and the low pressure fuel delivery system, fuel is prevented from leaking into the engine. Preferably, the apparatus is designed to allow the drop ejector to be easily replaceable by a consumer. This exchangeability of the drop ejector allows for easy maintenance of a fuel injection system, such as when the nozzles become clogged due to impurities in the fuel. Also, by allowing for removal and replacement of the drop ejector, various fuel types can be used in a given device and the proper drop ejector for the fuel type selected is simply exchanged and installed.




Further, the described method for ejecting drops of fuel (and the circuit to implement this method) according to a pulse-modulated scheme is beneficial because it is a non-complicated method for digitally controlling the drop ejector in a precise manner. The use of the circuitry to implement the pulse-modulated scheme allows for precise control of the fuel drops being ejected.




While the present invention has been particularly shown and described with reference to the foregoing preferred and alternative embodiments, those skilled in the art will understand that many variations may be made therein without departing from the spirit and scope of the invention as defined in the following claims. This description of the invention should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. The foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application. Where the claims recite “a” or “a first” element of the equivalent thereof, such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. The invention is limited by the following claims.



Claims
  • 1. A fuel delivery system, comprising:a drop ejector having a nozzle capable of digitally ejecting discrete drops of a combustible liquid; and a means for providing a pulse-modulated control signal to said drop ejector, wherein said pulse-modulated control signal is indicative of a desired number of drops to be ejected from said drop ejector during a given time frame.
  • 2. The fuel delivery system of claim 1, wherein said pulse-modulated control signal means is adapted to adjust said desired number of drops ejected within a given time frame in response to an operation condition input.
  • 3. The fuel delivery system of claim 2, wherein the fuel delivery system is in fluid communication with an internal combustion engine, and said operation condition input relates to a load on said engine.
  • 4. The fuel delivery system of claim 2, wherein said operation condition input relates to a throttle position.
  • 5. The fuel delivery system of claim 1, wherein said pulse-modulated control signal means comprises:an electronic controller responsive to an input signal indicative of an operation condition, wherein said electronic controller is adapted to provide an output signal indicative of a desired number of drops to eject from said drop ejector; and a pulse counter responsive to said electronic controller output signal.
  • 6. A fuel delivery system, comprising:a drop ejector having a nozzle capable of digitally ejecting discrete drops of a combustible liquid; and an electronic controller adapted to cause a desired number of drops to be ejected from said drop ejector during a given time frame.
  • 7. The fuel delivery system of claim 6, wherein said electronic controller is adapted to adjust said desired number of drops ejected within a given time frame in response to an operation condition input.
  • 8. The fuel delivery system of claim 7, wherein the fuel delivery system is in fluid communication with an internal combustion engine, and said operation condition input relates to a load on said engine.
  • 9. The fuel delivery system of claim 7, wherein said operation condition input relates to a throttle position.
  • 10. A method of delivering a combustible liquid to a fuel-powered apparatus, comprising the steps:digitally ejecting discrete drops of the combustible liquid from a drop ejector; and adjusting a number of said drops ejected from said drop ejector during a given time frame in response to an operation condition of the apparatus.
  • 11. The method of claim 10, wherein said operation condition is related to a throttle position.
  • 12. The method of claim 10, wherein:the apparatus is an internal combustion engine; said operation condition is related to engine load; and said adjusting step comprises increasing said number of drops ejected from said drop ejector during a given time frame in response to an increased engine load.
  • 13. A fuel injector, comprising:a drop ejector having a nozzle capable of digitally ejecting discrete drops of a combustible liquid; and an electronic circuit in electronic communication with said drop ejector, wherein said electronic circuit determines a desired number of drops to be ejected by said drop ejector during a given time frame and provides a pulse-modulated control signal to said drop ejector indicative of said desired number of drops.
  • 14. The fuel injector of claim 13, wherein said electronic circuit determines said desired number of drops based upon a signal indicative of an operation condition of a fuel-consuming apparatus, wherein said operation condition is selected from the group: (i) load on said fuel-consuming apparatus; and (ii) a throttle position of said fuel-consuming apparatus.
US Referenced Citations (7)
Number Name Date Kind
3717875 Arciprete et al. Feb 1973 A
5099815 Yamauchi et al. Mar 1992 A
5165373 Cheng Nov 1992 A
6162589 Chen et al. Dec 2000 A
6213099 Calvas et al. Apr 2001 B1
6257205 Calvas et al. Jul 2001 B1
6405936 Ganan-Calvo Jun 2002 B1