Internal-combustion engines – Combustion chamber means having fuel injection only – Having a particular relationship between injection and...
Patent
1998-09-02
2000-07-11
Wolfe, Willis R.
Internal-combustion engines
Combustion chamber means having fuel injection only
Having a particular relationship between injection and...
123 73C, F02B 500, F02B 3304, F02M 4500, F02D 4134
Patent
active
06085720&
DESCRIPTION:
BRIEF SUMMARY
SCOPE OF APPLICATION
The invention relates to a method for controlling an injection valve in a high-speed two-stroke internal combustion engine with fuel injection.
In addition, the invention relates to a device for the performance of such a method.
STATE OF THE ART
Whereas four-stroke engines in general, over the entire engine speed and load range, possess a relatively uniform running of the engine, two-stroke engines show significant differences between the engine speed ranges (idling) and "operative range". When idling (low engine speed), a considerable rough running takes place which always calls for an exact injection. When starting from a certain trigger signal, a computation of the injection start is effected, the same has to take place in the immediate proximity of the trigger signal since otherwise significant errors with regard to the desired injection start may occur. These--as already mentioned--depend substantially on the degree of uniformity of the running of the engine and may differ considerably from revolution to revolution so that the running of the engine becomes uncontrollable. That is why the injection has to take place close to the trigger point or trigger signal.
As is illustrated in the FIG. 1 in an angle diagram of the engine crankshaft (KW) relative to the top dead center (OT), for low engine speeds, the injection starts (ESB) in dependence upon the respective engine configuration, are within a first (hatched) range (ESB1) between 180 and 240.degree. KW (angles W4 and W3) before the top dead center (OT) of the engine. At higher engine speeds (several revs/min), all other injection starts, according to the respective load states, are necessary. Usually a displacement of the injection start in the direction of "early" within a second (hatched) range (ESB2) is necessary that is located between 270 and 350.degree. KW (angles W2 and W1) before the top dead center.
For low engine speeds (e.g. when idling), according to the foregoing explanations it is expedient and advantageous to place the trigger point at which the trigger signal is generated close to the beginning of the first range (ESB1), thus e.g. at the point identified with (TP) in FIG. 1. In this way only a short angular distance exists between (TP) and the beginning of the injection range (W3). If, with increasing numebrs of revolutions, the injection start is brought forward from the range (ESB1) into the range (ESB2), in such a case also the trigger point (TP) ought to be correspondingly brought forward. A (virtual) displacement of the trigger point is expediently carried out in that the computation of the injection start for the next revolution is effected (long arrow from TP via the angles W5 and W6 of the ignition range ZB after W1 in FIG. 1). On account of the requsitite computation time as wella s on account of the time required for controlling the opening time of the injection valve, it may happen in dependence of the required injection start, that the trigger signal (e.g. from a Hall transmitter) employed for the idling range cannot be evaluated. The injection for the next revolution would not be possible or only subject to serious flaws.
TECHNICAL PROBLEM, SOLUTION, ADVANTAGES
The technical problem of the invention is now to state a method for controlling a high-speed two-stroke engine, which overcomes these disadvantages and ensures for each revolution of the engine in dependence upon load and speed an optimal injection start in connection with the requisite duration of the injection.
The technical problem is resolved in a method of the type stated in the beginning in that, to each of the two ranges, a trigger point of its own is allocated and in that, when changing over between low and high engine speeds, starting from a predetermined threshold number of revolutions, a changeover of the control takes place between the two trigger points. In this manner it is possible, when changing over to higher engine speeds and, thereby, to a brought-forward injection start, to switch over to a new trigger point optimally
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Klare Hartmut
Loeffler Klaus
Lukomski Jan
Matthees Klaus
Mehlhose Uwe
Dolmar GmbH
Wolfe Willis R.
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