Internal-combustion engines – Charge forming device – Fuel flow regulation between the pump and the charge-forming...
Reexamination Certificate
2000-03-17
2001-07-31
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel flow regulation between the pump and the charge-forming...
C123S179170, C123S527000
Reexamination Certificate
active
06267104
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of engines with direct or indirect injection of liquid fuel into at least one combustion chamber.
The fuel can be liquefied petroleum or liquefied natural gas, dimethylether (DME), ethylal, methylal or diethylether (DEE).
BACKGROUND OF THE INVENTION
It is well-known to use these fuels in admixture with the intake air. Patent application WO 96/35,863 describes a system based on this concept where air and liquefied fuel are mixed upstream from the combustion chambers as a complement to a conventional gasoline injection system (of “common rail” type here). However, fuel vaporization problems are observed with this type of supply. To overcome this problem, this prior art proposes mixing the liquid fuel with the intake air in a place relatively distant from the combustion chamber; the temperatures are thus less high and better vaporization can be performed.
Recent developments have allowed to introduce the fuel in liquid form, directly or mixed with air, into the combustion chamber. This requires pressure maintenance in all the supply system, from the tank to the vaporization point: combustion chamber in the case of direct injection or intake pipes for indirect injection.
An important problem then consists in maintaining and controlling the liquid state by means of the pressure in all of the supply system, whatever the running conditions of the engine and the outside conditions. In fact, the liquefaction pressure variation can range from 1 to 18 bars according to the working temperature of the fuel.
The fuel tank is generally designed to withstand this type of pressures so that storage in the liquid state does not pose problems at this level of the supply circuit.
However, this is not the case in the other parts of the supply circuit and notably between the tank and the injectors.
More precisely, a problem arises when the engine is restarted after prolonged stoppage of the engine.
This phenomenon can be explained as follows: the injectors being permeable to the fluid, a slight liquid leak occurs when the engine is stopped, which lowers the pressure in the supply system and therefore changes the state of the fuel that goes from the liquid to the gaseous state. The leak is thus sustained.
After a more or less long period of immobilization of the vehicle, which depends on the storage conditions and on the structure of the injectors, the (originally liquid) fuel contained in the supply system can thus be vaporized and transferred to the engine, either directly into the combustion chamber or via the intake.
When the engine is restarted, the vaporized fuel is present in large amounts in the combustion chamber, which generates a non-flammable mixture (case of liquefied petroleum gas LPG) or self-ignition (case of dimethylether DME).
A known solution consists in isolating each injector of the rail by a solenoid valve when the vehicle is stopped. However, this solution is complex, bulky and expensive.
SUMMARY OF THE INVENTION
In order to solve the problems linked with bad pressure maintenance in the supply system of such engines, the present invention proposes an innovative solution, both simple and reliable.
It consists, when the engine is stopped, to isolate the part of the supply system comprising the injectors by any suitable means. The liquid fuel contained in the part thus isolated can then be drained into a suitable storage system (liquid or gaseous).
This concept thus prevents any liquid fuel leak into the engine and therefore allows good starting of the engine after a certain stoppage.
The object of the present invention thus is a system intended for pressure supply of liquid fuel to at least one combustion chamber of an internal-combustion engine, comprising a tank intended for pressure storage of the liquid fuel, means allowing pressure injection of the fuel into at least one combustion chamber, a line between said tank and said injection means, a pump placed in the tank or on said line, a pressure regulator placed in said tank or on said line, a capacity (canister) placed on a by-pass of the line towards an intake system (A) of the engine and intended for storage of the gaseous fuel, fuel injection being performed directly or not into the combustion chamber(s).
According to the invention, the system further comprises a means for isolating the injection means in relation to the tank and means for draining the injection means, placed on said by-pass, upstream from said capacity.
According to an embodiment of the invention, the injection means consists of at least one rail comprising each several injectors.
According to a particular embodiment of the invention, the system further comprises a return line between the injection means and the tank.
More precisely, the isolation means can consist of at least two solenoid valves placed respectively on the line and on the return line, on either side of the injection means.
Without departing from the scope of the invention, the isolation means can consist of a solenoid valve placed on the line between the tank and the by-pass.
In accordance with the invention, the system further comprises means for controlling the isolation means according to the engine stoppage time and conditions, such as the pressure and/or the surrounding temperature.
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patent: 0200663 (1982-12-01), None
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patent: 9635863 (1996-11-01), None
Antonelii, Terry, Stout & Kraus, LLP
Institut Francais du Pe'trole
Miller Carl S.
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