Internal-combustion engines – Water and hydrocarbon
Reexamination Certificate
2000-01-05
2001-07-31
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Water and hydrocarbon
C123S02500R, C123S575000
Reexamination Certificate
active
06267086
ABSTRACT:
This invention relates to a fuel system, and in particular to a fuel system of the type in which a unit pump/injector is used to supply both fuel and an auxiliary fluid, for example water, under pressure to a combustion space of an associated compression ignition internal combustion engine, and in which the auxiliary fluid is supplied to the injector independently of the supply of fuel, in use.
BACKGROUND OF THE INVENTION
A number of fuel systems of the type in which water is supplied to the combustion spaces of engines are known. For example, systems are known in which separate fuel and water injectors are associated with each combustion space. In a further known arrangement, water and fuel are supplied, independently, to a common injector used to deliver the fuel and the water to an engine combustion space.
Where the fuel and water are supplied to the injector separately, the water is typically supplied using a remote low pressure pump, the water flowing to the injector when the pressure within the injector is low. In such an arrangement, the timing of water supply to the injector and the quantity of water supplied are not controlled accurately. Where the pump is located remotely, if a water metering facility is provided, the large volume of pressurized water may result in the quantity of water delivered to the injector being difficult to control accurately.
SUMMARY OF THE INVENTION
According to the present invention there is provided a fuel system comprising a unit pump/injector, and a cam actuated plunger pump arranged to supply an auxiliary fluid to the injector, the plunger pump being located adjacent the unit pump/injector.
By locating the plunger pump adjacent the unit pump/injector, the plunger pump can be actuated by a cam mounted on the cam shaft, and thus can be made to deliver the auxiliary fluid, for example water, at predetermined points in the engine operating cycle. Further, by locating the plunger pump adjacent the injector, a reduced quantity of pressurized auxiliary fluid is present between the pump and the injector, thus metering can be improved.
The plunger pump is preferably provided with a metering device. The metering device may comprise an arrangement controlling the quantity of the auxiliary fluid supplied to the plunger pump, for example a shuttle metering system or an electromagnetically controlled valve arranged to permit fluid flow towards the plunger pump for a period of duration dependent upon the quantity of auxiliary fluid to be delivered to the injector.
In order to reduce corrosion and improve lubrication, the system may further comprise a piston member moveable under the influence of the pressure within a control chamber defined, in part, by the plunger of the plunger pump, the auxiliary fluid to be supplied to the injector being supplied, in use, to a pump chamber defined, in part, by a surface of the piston member, wherein the control chamber is arranged to be supplied with a control fluid to control the delivery of the auxiliary fluid to the injector. The control fluid may be supplied through a metering device, the quantity of control fluid determining the rest position of the piston member to control the volume of auxiliary fluid to be delivered. Alternatively, a spill valve may be provided to control the pressure of the control fluid within the control chamber, hence controlling when fluid is delivered to the injector.
To further reduce the risk of corrosion, the fuel system is conveniently provided with means permitting the auxiliary fluid to be purged from the system.
REFERENCES:
patent: 1848380 (1932-03-01), Parks
patent: 4351289 (1982-09-01), Renda
patent: 5529024 (1996-06-01), Wirbeleit et al.
patent: 5762033 (1998-06-01), Rembold et al.
patent: JP-8246979 (1996-09-01), None
Dingle Philip John Gregory
Greeves Godfrey
Delphi Technologies Inc.
Gimie Mahmoud
Ohlandt Greeley Ruggiero & Perle L.L.P.
Yuen Henry C.
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