Internal-combustion engines – Charge forming device – Diverse fuel supply
Reexamination Certificate
1999-08-02
2001-05-01
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Charge forming device
Diverse fuel supply
Reexamination Certificate
active
06223734
ABSTRACT:
PRIOR ART
The invention is based on a fuel injection system 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 that serves the purpose of laminated injection of fuel and a supplementary liquid, such as diesel fuel and water, so as to reduce pollutant emissions from the engine and possibly to increase its efficiency. On the other hand, in the known injection system, the so-called common rail technique is employed, in which all the injection nozzles serving the engine are charged with fuel at high pressure from a common rail pressure reservoir.
It is disadvantageous in the known fuel injection system that one complicated and relatively expensive 3/2-way valve is needed for each individual injector for metering the quantity of supplementary liquid, as well as one further 3/2-way valve for controlling the diesel injection quantity. For prestorage of the supplementary liquid, the fuel delivery from the common rail pressure reservoir to the injection nozzle is disrupted using the first 3/2-way valve and at the same time a pressure chamber surrounding the md and in which fuel at high pressure is stored is drained off to the low- pressure fuel side by means of a suitable position of the first 3/2-way valve. By means of the resultant pressure drop in the pressure chamber, supplementary liquid is fed via a suitable line into the pressure chamber and positively displaces the equivalent volume of fuel. Next, the first 3/2-way valve is returned to a position that establishes a communication between the common rail pressure reservoir and the pressure chamber in the injection valve. For quantitatively precise metering of the fuel quantity to be injected and that is intended to follow the prestored supplementary liquid in the injection surge caused by the next valve opening, the further 3/2-way magnet valve is provided, which selectively connects the back end of the nozzle needle, which is held in the closing position by a spring, selectively with either the common rail pressure reservoir or the low-pressure fuel side and as a result chronologically controls the valve needle stroke, the opening and closing of the valve, and thus the desired injection quantity.
In principle, the known fuel injection system for each individual injector requires the two precise and thus complicated 3/2-way control magnet valves, so that both the desired fuel quantity and the required quantity of supplementary liquid can be metered exactly.
ADVANTAGES OF THE INVENTION
The fuel injection system according to the invention, to simplify its structure and thus make it more economical to produce, will be set forth herein after. As a result, the two complicated and expensive 3/2-way magnet control valves can be replaced with a single, simpler and less expensive 2/2-way valve, and at the same time the possibility is afforded of shifting the quantitative metering for the supplementary liquid to a single, precision metering valve, which can serve an entire group of injectors. While the second 2/2-way valve determines solely the opening and closing time for the supplementary liquid prestorage, the quantitative metering for the fuel quantity to be injected is effected by means of a suitable timing control of the second 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 especially to prevent outgassing of the supplementary liquid, as a rule water, at high temperatures if the boiling point is exceeded, it is recommended that a check valve be used between the second 2/2-way valve and the low-pressure fuel side.
It is also advantageous if the nozzle needle on the butt end of its injector tappet, in a radial extension, has a small piston which protrudes into a chamber acted up by high pressure from the common rail pressure reservoir; this chamber is in turn sealed off in pressure proof fashion from the chamber surrounding the nozzle needle. By subjecting the constant piston area to the common rail pressure, the control motions of the nozzle needle in the injection event become independent of the absolute pressure conditions in the common rail pressure reservoir, because for the motion of the injector tappet, it is always the same resistance, namely the force of the valve spring, that needs to be overcome, and thus The motion forces remain constant. The result is constant switching times, which are favorable from a control standpoint and are each determined by the applicable time of motion of the injector tappet.
An embodiment of the fuel injection system according to the invention in which the high-pressure pump for pumping the fuel is part of a high-pressure pump unit that can accomplish the quantitative metering for both the fuel injection and the injection of supplementary liquid is especially preferred. In this way, on the one hand, the M pump usually used for metering the supplementary liquid can be dispensed with, and on the other the overall system can be designed more compactly. The high-pressure pump unit, which as before supplies the common rail pressure reservoir, now via a further hydraulic line also drives a divider piston unit, with which the volumetric quantity of supplementary liquid specified by the high-pressure pump unit is dispensed into the dual-substance nozzle.
To that end, in a special feature, the high-pressure pump unit of the invention has one or more high-pressure pistons, which counter-to the pressure of compression springs compress fuel in a compression chamber to a pressure level of over 1000 bar, and as a rule even to nearly 2000 bar. The high-pressure pistons are preferably disposed in line and are driven by a camshaft. On one end of the compression chamber outside the path of reciprocation of the high-pressure pistons, a longitudinally movable gap-sealed first piston is disposed, which is braced by a compression spring against a likewise longitudinally movable gap-sealed second piston. The backside face of the second piston is rounded or beveled, so that a longitudinally displaceable dimensioning wedge can rest on it in force-locking fashion and can longitudinally arrest the second piston in a-variable relative axial position with respect to the first piston. To adjust the relative position of the two pistons, a triggerable electric motor is preferably provided, which drives a spindle that engages a thread of the dimensioning wedge.
It is also possible according to the invention for the divider piston unit to have a special design, namely instead of a conventional divider piston a diaphragm, which is braced firmly in the divider piston unit and sealingly partitions off one inner chamber having fuel from the other inner chamber having supplementary liquid. As a result, the never entirely avoidable, albeit slight mixing, when conventional divider pistons are used, of the operating fluid of the divider piston with the fluid (in this case supplementary liquid) to be pumped is reliably avoided. To prevent the diaphragm from rupturing in the event of very forceful pressure deflections, a mechanical stop is preferably provided in the inner chamber of the divider piston unit charged with supplementary liquid, and the diaphragm can run up against this stop, which defines its maximal expansion.
REFERENCES:
patent: 4520774 (1985-06-01), Sitter
patent: 4524033 (1985-06-01), Elledge
patent: 4590904 (1986-05-01), Wannenwetsch
patent: 4612905 (1986-09-01), Dietrich
patent: 4693227 (1987-09-01), Satou
patent: 4705010 (1987-11-01), Baranescu
patent: 5174247 (1992-12-01), Tosa
patent: 5732679 (1998-03-01), Takahashi
patent: 5862793 (1999-01-01), Jay
patent: 5979410 (1999-11-01), Grieshaber
patent: 6067964 (2000-05-01), Ruoff et al.
Harndorf Horst
Ruoff Manfred
Benton Jason
Greigg Edwin E.
Greigg Ronald E.
McMahon Marguerite
Robert & Bosch GmbH
LandOfFree
Fuel injection system for an internal combustion engine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fuel injection system for an internal combustion engine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fuel injection system for an internal combustion engine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2562372