Internal-combustion engines – Charge forming device – Diverse fuel supply
Patent
1999-06-22
2000-07-25
Miller, Carl S.
Internal-combustion engines
Charge forming device
Diverse fuel supply
123447, F02B 1300
Patent
active
060925140
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a fuel injection system for an internal combustion engine for an internal combustion engine.
Such fuel injection systems are known for instance from German Patent DE 43 37 048 C2. In it, on the one hand a dual-substance nozzle is provided, which serves to provide layered injection of fuel and a supplementary fluid, such as Diesel fuel and water, in order to reduce pollutant emissions from the engine and optionally increase efficiency. On the other hand, in the known injection system the so-called common rail technique is realized, in which all the injection nozzles serving the engine are supplied with high-pressure fuel from a common rail pressure reservoir.
A disadvantage of the known fuel injection system is that for each individual injector, for metering the supplementary fluid, a complicated and relatively expensive 3/2-way valve is needed, and a further 3/2-way valve is needed to control the Diesel injection quantity. To prestore the supplementary fluid, the fuel delivery from the common rail pressure reservoir to the injection nozzle is interrupted with the first 3/2-way valve, and at the same time a pressure chamber, which surrounds the injection nozzle and in which fuel is stored at high pressure, is drained to the fuel low-pressure side through a corresponding position of the first 3/2-way valve. As a result of the attendant pressure drop in the pressure chamber, supplementary fluid is pumped into the pressure chamber via a suitable line and positively displaces the corresponding volume of fuel. After that, the first 3/2-way valve is returned to a position which establishes a communication between the common rail pressure reservoir and the pressure chamber in the injection valve. For accurate-quantity metering of the fuel quantity to be injected, which quantity should follow the prestored supplementary fluid in the injection surge brought about by the next valve opening, a further 3/2-way magnet valve is provided, which selectively connects the back side of the nozzle needle, which is held in the closing position by a spring, selectively with either the common rail pressure reservoir or the fuel low-pressure side and as a result controls the timing of the stroke of the valve needle, the opening and closing of the valve, and thus the desired injection quantity.
In principle, the known fuel injection system requires the two precise-action and thus complicated 3/2-way control magnet valves for each individual injector, so that the injector can precisely meter both the desired fuel quantity and the required quantity of supplementary fluid.
ADVANTAGES OF THE INVENTION
The fuel injection system of the invention, for the sake of structural simplification and thus more economical manufacture, has been set forth hereinafter. As a result, the two complicated and expensive 3/2-way magnet control valves can be replaced by simpler and less expensive 2/2-way valves, and at the same time the possibility is afforded of shifting the metering for the supplementary fluid to a single, precisely acting metering valve that is capable of serving an entire group of injectors. While the second 2/2-way valve determines only the opening and closing time for the supplementary fluid prestorage, the metering for the fuel quantity to be injected is accomplished by a suitable timing control of the first 2/2-way valve in the injection line between the common rail pressure reservoir and the pressure chamber.
In order to assure constant pressure conditions in the line system and, particularly also at high temperatures, to prevent outgassing of the supplementary fluid, as a rule water, when the boiling point is exceeded, it is recommended that a check valve be used between the second 2/2-way valve and the fuel low-pressure side.
It is also advantageous if the nozzle needle, at the blunt of its injector tappet, in the radial extension, has a small piston which protrudes into a chamber acted upon by high pressure from the common rail pressure reservoir, which chamber is in turn sealed off in pre
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patent: 5438966 (1995-08-01), Teegan
patent: 5529024 (1996-06-01), Wirbeleit
patent: 5601067 (1997-02-01), Wirbeleit
patent: 5651346 (1997-07-01), Remmels
patent: 5722377 (1998-03-01), Schoenfeld
patent: 5979410 (1999-11-01), Grieshaber
Harndorf Horst
Ruoff Manfred
Greigg Edwin E.
Greigg Ronald E.
Miller Carl S.
Robert & Bosch GmbH
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