Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1999-03-24
2000-08-01
Moulis, Thomas N.
Internal-combustion engines
Charge forming device
Fuel injection system
123447, 123456, 123506, F02M 3704
Patent
active
060951184
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a fuel injection system for an internal combustion engine. In one such fuel injection system, known from European Patent Disclosure EP B1 0 243 871, an in-line injection pump that has three pump pistons with corresponding pump work chambers is provided for supplying pressure to the high-pressure fuel reservoir. Each of these pump pistons pumps fuel into the high-pressure fuel reservoir with a regulated quantity, and the high-pressure pumping of fuel injection quantities is effected by one magnet valve for each cylinder, controlled by an electric control unit, each valve being disposed in a relief line of the respective pump work chamber and on closing determining the phase of the high-pressure pumping. In the intake stroke, the applicable pump work chamber is made to communicate with a fuel inlet by means of a control edge moved by the piston, so that the pump work chamber at bottom dead center is entirely filled with fuel. The pump pistons are driven by multiple cams, in such a way that they have their high-pressure pumping phase in synchronism with the applicable fuel injection point of the individual fuel injection valves, and thus an approximately equal pressure in the high-pressure fuel reservoir can be established. With the aid of a pressure sensor, this pressure is detected, and in accordance with a set-point value, the electric control unit outputs a control signal to the respective magnet valves.
This arrangement has the disadvantage of requiring very complicated and expensive control for each pump element of the high-pressure pump. Changing the pressure in the high-pressure reservoir can then be done only whenever high-pressure fuel injection is taking place, so that a spontaneous change to a higher pressure level in the high-pressure fuel reservoir can be accomplished with a delay. To effect a change of pressure in the reservoir, the pressure can rise only during the injection. This results in an undefined status of the reservoir pressure during injection, making it difficult to determine the correct injection quantity as a summation effect of pressure prevailing at a particular metering cross section and of time.
ADVANTAGES OF THE INVENTION
By means of the fuel injection system of the invention, the advantage is obtained that by operating the pump elements on and off, this second pump element being operated at a constant high-pressure pumping quantity, very simple regulation of the pressure in the high-pressure fuel reservoir can be attained. In particular, by turning on the pump element that operates at a constant high-pressure pumping quantity, a fast and spontaneous pressure increase in the high-pressure fuel reservoir is attained, so that changing operating conditions can be reacted to quickly. It is particularly advantageous that when the second of the pump elements, in a period of time located between the fuel injection events of the individual fuel injection valves, is already pumping, the pressure level can be changed from a first value to a second value early, and that then by means of the pump elements that pump fuel with a variable fuel pumping quantity, the pressure level can be kept constant in the operating range within which the injections take place. A stable reservoir pressure during injection is thus attained. To carry out the pressure increase, the second pump element is operated for only a relatively short portion of the total operating time of the fuel injection pump under operating conditions and can advantageously be designed for a shorter service life.
Moreover, pressure fluctuations in the high-pressure reservoir are advantageously avoided both in the version set forth herein. It is also advantageous if the drive cams driven in synchronism with the engine are embodied as multiple cams, in particular triple cams, so that a high number of strokes per revolution is attainable even if there are only a few pump elements.
BRIEF DESCRIPTION OF THE DRAWING
One exemplary embodiment of the invention is shown in the drawings and will be d
REFERENCES:
patent: 4777921 (1988-10-01), Miyaki et al.
patent: 5058553 (1991-10-01), Kondo et al.
patent: 5197438 (1993-03-01), Yamamoto
patent: 5201294 (1993-04-01), Osuka
patent: 5277156 (1994-01-01), Osuka et al.
Klinger Horst
Kuhn Uwe
Loesch Gerd
Rosenau Bernd
Soccol Sandro
Greigg Edwin E.
Greigg Ronald E.
Moulis Thomas N.
Robert & Bosch GmbH
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