Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1999-04-30
2000-02-08
Miller, Carl S.
Internal-combustion engines
Charge forming device
Fuel injection system
123446, F02M 4100
Patent
active
06021760&
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 type which has been disclosed by DE-C1-195 19 192, the control valve is embodied as a simply functioning flat seat valve which, with its sealing surface, controls the exit of the outflow conduit from the control chamber. The valve member of this control valve is actuated in this connection by means of a piston that has the pressure shoulder. The piston is supported by a compression spring against a second piston, which for its part can be adjusted by the piezoelectric drive device and with its end face disposed next to the pressure shoulder, defines the hydraulic pressure chamber. This known control valve functions so that the valve either opens or closes the outflow conduit. Accordingly, the injection valve member of the fuel injection valve assumes either an open or closed position.
ADVANTAGES OF THE INVENTION
The fuel injection device according to the invention has the advantage over the prior art that two valve seats are provided in the course of the outflow conduit and the closing body is moved with its sealing surfaces from one valve seat to the other upon actuation by the piezoelectric drive device in a single movement sequence, wherein after the outflow conduit is initially closed, it is opened for the meantime by way of the valve chamber and is then closed once more. In the movement sequence of the closing body, this leads to a very short-term relief of the control chamber, which results in an opening of the fuel injection valve member with a likewise very short fuel injection. Very small injection quantities can advantageously be controlled in this manner, which is determined by the movement sequence of the closing body from one valve seat to the other. This movement sequence is essentially dependent on a single excitation of the piezoelectric drive device and can therefore be limited to a very short period of time. The time requirement for this injection can for technical reasons be kept significantly smaller than when, with a fuel injection device of the type as defined herein after, the control valve is opened twice for the same event of the pre-injection, with a first excitation of the piezoelectric drive device and is then closed by a reduction in the excitation. Every time, this switching requires a time-consuming movement reversal of the control valve member and a further time component must be reckoned with, which is required for the respective changing of the excitation state of the piezoelectric drive device. Consequently, the lost time for the control of the injection sequence of the pre-injection and main injection is significantly less in the embodiment according to the invention.
By means of the fuel injection device according to the invention, it is possible here, through appropriate metering of the excitation of the piezoelectric drive device, to keep the closing body in an intermediate position in which, because of the above-mentioned operation, a relief of the control chamber takes place over a prolonged period of time, and through which the desired main injection quantity can then be injected, following the pre-injection quantity, which is introduced in the above-described manner, and after a pause in the injection process. With the fuel injection device according to the invention, an injection can consequently be produced in an extremely precise manner, in which very small pre-injection fuel quantities can be exactly injected, a time period between the pre-injection and the main injection can be exactly maintained, and as a result, the main injection is produced in the customary fashion in a likewise very precisely metered manner.
In an advantageous manner the stroke of the closing body is matched to the adjusting speed by means of the piezoelectric drive device so that the desired pre-injection quantity is produced.
Advantageous improvements of the invention will be explained in more detail in conjunction with the drawings and the subsequent desc
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patent: 5915361 (1999-06-01), Heinz
Greigg Edwin E.
Greigg Ronald E.
Miller Carl S.
Robert & Bosch GmbH
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