Fuel injection system for an internal combustion engine

Details Fuel injection system for an internal combustion engine Fuel injection system for an internal combustion engine

2001-06-04

2003-02-18

Argenbright, Tony M. (Department: 3747)

Internal-combustion engines

Charge forming device

Fuel injection system

C123S446000, C123S467000

Reexamination Certificate

active

06520152

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a 35 USC 371 application of PCT/DE 00/02553 filed on Aug. 2, 2000.
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention is based on fuel injection system for an internal combustion engine and more particularly to such a fuel injection system capable of injecting fuel at at least two different pressures.
DESCRIPTION OF THE PRIOR ART
One injection system of the type with which this invention is concerned has been disclosed by European Patent Disclosure EP 0 711 914 A1.
For better comprehension of the ensuing description, several terms will first be defined in more detail: In a pressure-controlled fuel injection system, a valve body (such as a nozzle needle) is opened counter to the action of a closing force by the fuel pressure prevailing in the nozzle chamber of an injector, and thus the injection opening is uncovered for an injection of the fuel. The pressure at which fuel emerges from the nozzle chamber into the cylinder is called the injection pressure. The term stroke-controlled fuel injection system is understood in the context of the invention to mean that the opening and closing of the injection opening of an injector takes place with the aid of a displaceable valve member on the basis of the hydraulic cooperation of the fuel pressures in a nozzle chamber and in a control chamber. An arrangement is furthermore described below as central when it is provided jointly for all the cylinders, and as local if it is intended for only a single cylinder.
In the pressure-controlled fuel injection system known from EP 0 711 914 A1, with the aid of a high-pressure pump, fuel is compressed to a first, high fuel pressure of about 1200 bar and stored in a first pressure reservoir. The fuel that is at high pressure is also pumped into a second pressure reservoir, in which by regulation of its fuel delivery using a 2/2-way valve, a second high fuel pressure of about 400 bar is maintained. Via a central valve control unit and a central distributor device, either the lower or the higher fuel pressure is carried into the nozzle chamber of an injector. There, by means of the pressure, a spring-loaded valve body is lifted from its valve seat, so that fuel can emerge from the nozzle chamber.
In this known fuel injection system, the fuel for an injection from the applicable central pressure reservoir is split via the central valve unit and the central distributor device to the individual injectors. The maximum possible injection window in each case is determined jointly by the valve unit and the distributor device.
From International Patent Disclosure WO98/09068, a stroke-controlled injection system is also known in which once again two pressure reservoirs for storing the two fuel pressures are provided. Once again, the metering of the applicable fuel pressure takes place via central valve units.
SUMMARY OF THE INVENTION
According to the invention in order to achieve improved metering of the lower fuel pressure, it is proposed that the lower fuel pressure be controlled not centrally but rather locally for each injector, via a valve unit. Because of the short line between a local valve unit and the nozzle chamber of the injector, line losses are reduced to a minimum. In addition to the better metering capability, further advantages reside in the ability to accurately replicate the pre- and post-injection at the lower fuel pressure, as well as a reduced influence of component tolerances on the pre- and post-injection events.


REFERENCES:
patent: 4712528 (1987-12-01), Schaffitz
patent: 5642714 (1997-07-01), Buckley
patent: 5711274 (1998-01-01), Drummer
patent: 5732679 (1998-03-01), Takahashi et al.
patent: 6112721 (2000-09-01), Kouketsu et al.
patent: 6-93936 (1994-04-01), None

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