Fluid sprinkling – spraying – and diffusing – Fluid pressure responsive discharge modifier* or flow... – Fuel injector or burner
Reexamination Certificate
2001-11-20
2004-07-13
Hwu, Davis (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Fluid pressure responsive discharge modifier* or flow...
Fuel injector or burner
C239S533200, C239S585100, C239S585400, C239S585500, C239S088000
Reexamination Certificate
active
06761325
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hydraulically actuable dual fuel injection valve and a dual needle assembly, for injecting two different fuels into the combustion chamber of an internal combustion engine.
BACKGROUND OF THE INVENTION
Because of its ready availability, low cost and potential for reducing particulate emissions, natural gas is a promising substitute for diesel fuel for fuelling compression ignition engines, commonly known as “diesel-cycle” engines. Persons skilled in the technology involved here will understand that natural gas is just one example of a preferred fuel, and that other fuels are also suitable, such as hydrogen, propane and other fuels that are cleaner burning substitutes for diesel fuel. A cleaner burning substitute fuel for diesel is defined as a fuel that can be used in an engine to substantially match the performance of a diesel-fuelled engine with lower particulate matter and/or nitrogen oxide (NOx) emissions.
Conventional methods of introducing a gaseous fuel into an engine premix all of the gaseous fuel with the intake air, which is a method known as “fumigation”. Engines using such an approach have been unable to match the power, performance, and efficiency of diesel-fuelled engines. The applicant has found that the inherent favorable operating characteristics and high efficiency of conventional diesel-fuelled engines can be preserved when at least some of the gaseous fuel is introduced directly into the engine's combustion chamber, late in the compression stroke.
A problem with gaseous fuels such as natural gas is that, compared to diesel fuel, much higher temperatures and pressures are typically needed to auto-ignite the fuel. A solution to this problem, which allows the preservation of the major components of diesel-cycle engines is to inject a small amount of more auto-ignitable fuel such as diesel fuel, to initiate the ignition and combustion of the cleaner burning gaseous fuel.
Using a pilot fuel in addition to a main charge of gaseous fuel requires the installation of at least two independently operable injection valves, one for the pilot fuel and one for the gaseous main fuel. To avoid having to redesign and replace the cylinder head, it is preferable to employ a gaseous and liquid fuel injection valve that fits into the same opening as a conventional diesel fuel injection valve. Accordingly, there is a need for a gaseous and liquid fuel injection valve arrangement that allows independent introduction of liquid pilot fuel and gaseous main fuel directly into the combustion chamber, and that has the same exterior dimensions as a conventional diesel injection valve.
SUMMARY OF THE INVENTION
A dual fuel injection valve separately injects a main fuel and a pilot fuel into a combustion chamber of an internal combustion engine. The injection valve comprises:
(a) a hollow injection valve body comprising:
a hydraulic fluid inlet port through which pressurized hydraulic fluid can be introduced into fluid passages and a control chamber disposed within the interior of the valve body;
a hydraulic fluid drain port through which hydraulic fluid can be drained from the control chamber;
at least one control valve that is operable to selectively direct the flow of the hydraulic fluid and control hydraulic fluid pressure within the control chamber to influence movement of at least one of an outer needle and an inner needle between respective open and closed positions;
a first-fuel inlet port through which a first fuel can be introduced at injection pressure into the valve body;
a first-fuel passage provided within the valve body and extending between the first-fuel inlet port and a first-fuel cavity associated with the outer needle;
a second-fuel inlet port through which a second fuel can be introduced into the valve body;
a second-fuel passage connecting the second-fuel inlet port to a second-fuel cavity associated with the inner needle; and
(b) a dual needle assembly comprising:
the outer needle, which is hollow and disposed within the injection valve body, wherein the outer needle is movable between a closed position in which a first sealing surface associated with the outer needle contacts a first seat associated with the body and an open position in which the first sealing surface is spaced apart from the first seat, allowing the first fuel to flow from within the first-fuel cavity into the combustion chamber through at least one first-fuel ejection port; and
the inner needle, which is disposed within the hollow outer needle, wherein the inner needle is movable between a closed position in which a second sealing surface associated with the inner needle contacts a second seat associated with the outer needle and an open position in which the second sealing surface is spaced apart from the second seat, allowing the second fuel to flow from within the second-fuel cavity into the combustion chamber through at least one second-fuel ejection port.
In one embodiment, the first fuel is a main fuel and the second fuel is a pilot fuel that is more auto-ignitable than the main fuel. The hollow outer needle preferably serves as an inner valve body and the second-fuel cavity is preferably an annular cavity disposed between the inner needle and the outer needle.
The control chamber is preferably employed to influence the position of the outer needle and an inlet fluid passage connects the control chamber to the hydraulic fluid inlet port, a drain fluid passage connects the control chamber to the drain port, and the control valve is operable to selectively control the flow of hydraulic fluid between the control chamber and the drain port or the hydraulic fluid inlet port to modulate pressure within the control chamber between drain pressure, when pressure within the control chamber is associated with pressure at the drain port, and rail pressure, when pressure within the control chamber is associated with pressure at the hydraulic fluid inlet port.
The dual needle assembly is preferably dynamically disposed within the control chamber and the volume of the control chamber is preferably variable in response to movement of the dual needle assembly. Pressure within the control chamber is preferably held at rail pressure to generate a hydraulic force that contributes to maintaining the outer needle in the closed position. A spring preferably provides an additional closing force that cooperates with the hydraulic force to maintain the outer needle in the closed position. Fuel pressure within the first-fuel cavity preferably generates an opening force acting on the outer needle whereby the outer needle is movable to the open position under the influence of the opening force when pressure within the control chamber is reduced to close to drain pressure.
The outer needle is preferably biased in the closed position when pressure within the control chamber is at drain pressure or close to drain pressure (that is, the control chamber pressure has a value sufficiently near drain pressure such that the outer needle is nevertheless biased in the closed position) and the outer needle is movable to the open position when hydraulic fluid pressure within the control chamber is at rail pressure. Preferably, a spring biases the outer needle in the closed position. The outer needle preferably comprises a shoulder disposed within the first control chamber and when pressure within the first control chamber is raised to rail pressure the hydraulic force is applied to the shoulder.
In another embodiment of the present injection valve, the body preferably further comprises a second control chamber employed to influence the position of the inner needle and a second control valve is preferably operable to selectively control pressure of hydraulic fluid within the second control chamber to generate a hydraulic force that contributes to positioning the inner needle in one of the closed or open positions. The inner needle preferably comprises a shoulder that is dynamically disposed within the second-fuel cavity and the shoulder provides an area for receiving an op
Baker S. Michael
Douville Bradley D.
Lennox Tim
Mumford David
Post Adrian
Hwu Davis
McAndrews Held & Malloy Ltd.
Westport Research Inc.
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