Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
2000-02-11
2001-01-30
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C417S385000
Reexamination Certificate
active
06178951
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to pumps designed to inject fuel directly into the combustion chambers of a spark ignition engine. Unlike the diesel fuel used with diesel engines, the fuels used in spark ignition engines (gasoline and liquefied petroleum gas) do not lubricate the surfaces with which they are in contact. Piston-operated positive displacement pumps compress the fuel directly, incurring a risk of seizing. Furthermore, the only way of controlling the pressure of these pumps, the cylinder capacity of which is fixed, is by dissipating energy in a return path, which impairs the energy yield, heats the fuel and can give rise to cavitation.
In order to reduce the risk of seizing, a pump has already been proposed (FR-A-2 603 347) which has fuel compression chambers, each of which is bounded by a diaphragm separated by hydraulic fluid from a piston driven by a rotating plate. The stroke of the piston and the volume of liquid occupying the compartment defined by the piston and the diaphragm is constant, which does not resolve the problem of regulating the delivery rate and injection pressure.
An injection pump is also known (U.S. Pat. No. 5,520,523) which has a supply chamber for feeding an injection circuit, separated by a diaphragm from a compartment defined by a bore in the housing and by a piston arranged to be reciprocated during operation. The chamber is connected to a fuel supply and to the injection circuit by non-return valves. The pressure of the liquid occupying the compartment can be adjusted.
SUMMARY OF THE INVENTION
The purpose of the present invention is to provide a high-pressure injection pump which better meets practical requirements than those previously known, in particular because it allows the volume displaced by the pump to be regulated in a simple manner by means of a structure which practically eliminates the risk of seizing.
In particular, the invention proposes a pump comprising a plurality of modules in a housing each having at least one chamber for supplying a fuel injection circuit, each of said chambers being separated by a deformable diaphragm from a compartment defined by a respective bore in the housing and by a piston activated reciprocably mounted in said bore. A common member drives all pistons. Each chamber is connected to a fuel supply by an inlet and non-return valves for connect the chambers to the injection circuit. Means are provided for independently adjusting a liquid pressure in each of said compartments.
It will be seen that the invention imparts to each intermediate chamber occupied by a hydraulic fluid, which has a lubricating effect, an adjustment action in addition to its anti-seizing action. This adjusting action may be applied gradually or on an all or nothing basis.
In the latter case, it is sufficient to connect one of the compartments to discharge to suppress delivery of a flow by the corresponding module.
In the first case, a gradual action can be produced by adjusting the cross-section of a return leakage of the hydraulic fluid to the discharge by means of an analogue or step by step controlled solenoid. The presence of a leakage reduces the amount of displacement of the diaphragm by the piston.
Each of the modules may be assigned to a combustion chamber of the engine. However, it is more advantageous to provide several injectors individually controlled, generally by electromagnetic means, which will permit the use of a single supply of pressurized fuel.
The modules may be connected to a common injection rail supplying all the injectors, the number of units in service being selected as a function of the operating speed of the engine.
Any one of the units can be put out of operation , simply by connecting the compartment to the discharge.
Pump operation can consequently be adjusted in a very simple manner to take account of the load conditions of the engine and in particular to provide an easy means of obtaining a lean mixture at nominal speed, produced by direct injection, and a rich mixture when starting the engine or during transitory conditions. This all or nothing adjustment may be used in conjunction with the gradual adjustment by continuously adjusting the pressure or substituted to it.
It is of particular advantage to use several modules with supply compartments having different cross-sections and/or different capacities. A graded system of this type enables the global yield and the regularity of the mechanical drive torque to be optimised by an appropriate selection of the modules activated.
The above features and others will become more apparent from the following description of specific embodiments, given by way of example and not restrictive in any respect. The description is given with reference to the appended drawings.
REFERENCES:
patent: 2960936 (1960-11-01), Dean et al.
patent: 3433161 (1969-03-01), Vetter
patent: 3918846 (1975-11-01), Winkler
patent: 5249932 (1993-10-01), Van Bork
patent: 5421710 (1995-06-01), Yorita
patent: 5520523 (1996-05-01), Yorita et al.
patent: 5899671 (1999-05-01), Horn
patent: 6113361 (2000-09-01), Djordjevic
Doreau Jean
Piaton J{acute over (e)}r{circumflex over (o)}me
Poirier Michel
Larson & Taylor PLC
Moulis Thomas N.
Sagem SA
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