Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1996-10-18
1997-12-02
Moulis, Thomas N.
Internal-combustion engines
Charge forming device
Fuel injection system
123458, 137517, F02M 4100
Patent
active
056924763
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a fuel injection device for internal combustion engines. In a fuel injection device of this kind disclosed by a prior German Patent Application with the serial number P 44 142 42.0, a high pressure fuel pump delivers fuel from a low pressure chamber into a high pressure accumulation chamber, which is connected via high pressure lines to the individual injection valves that protrude into the combustion chamber of the engine to be fed, wherein this common pressure storage system (common rail) can be adjusted to a particular pressure by a pressure control device on the high pressure pump so that the injection pressure at the injection valves can be determined independent of speed over the entire operating performance graph of the engine to be fed. To control the injection times and injection quantities at the injection valve, an electrically controlled control valve is inserted into the high pressure line at each of these injection valves and with its opening and closing, controls the high pressure fuel injection at the injection valve.
Furthermore, the known fuel injection device has through flow limiting valves in the high pressure lines, which are intended to close the line in the event of a leak in order to thus reliably prevent an uncontrolled escape of fuel and the dangers connected with it. To this end, the through flow limiting valve has a movable valve member that is pressed counter to the force of a restoring spring by the fuel flowing against this valve member so that it seals against a valve seat the moment a particular pressure drop occurs in the high pressure line downstream of the through flow limiting valve and thus closes the high pressure line.
The known through flow limiting valve, though, has the disadvantage that it only reacts to relatively large leakage quantities so that smaller leakage quantities can occur unnoticed.
ADVANTAGES OF THE INVENTION
The fuel injection device according to the invention has the advantage over the prior art that even small leakage quantities in the high pressure lines are detected and result in a closing of these lines by means of the respective through flow limiting valve. Due to this detection of damages, even at very small through flow rates, injection valves which are not closing completely, for example, can also be detected and switched off from the operation of the motor so that severe resultant damages to the motor can be prevented.
The reaction of the through flow limiting valve, even when there are small leakage quantities, occurs advantageously by means of the matching, according to the invention, of the valve member throttle cross section of the through flow limiting valve and the force of the restoring spring as a function of the flow rate in the injection valve, which occurs so that throttle cross section and spring force are set so low that even during an injection at the injection valve when the high pressure line is intact, the valve member is slid toward the valve seat.
This valve member stroke produced by the pressure drop in the high pressure line between the through flow limiting valve and the injection valve, though, is smaller than its maximum stroke path until contact against the valve seat in the closed position of the through flow limiting valve.
When the high pressure line and injection valve are intact, the valve member returns to its original position once more as a result of the equal pressure increase in the high pressure line upstream and downstream of the through flow limiting valve when the injection valve is closed. In contrast, when there is damage, the valve member does not come back to its original starting position because of the pressure difference so that the subsequent stroke motion toward the valve seat is executed from an increased initial level, until the through flow limiting valve closes.
This advantageously lends the through flow limiting valve an integrating character, which makes it possible to detect even small leakage quantities and close the corresponding line. With la
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Boehland Peter
Egler Walter
Greigg Edwin E.
Greigg Ronald E.
Moulis Thomas N.
Robert & Bosch GmbH
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