Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1990-10-02
1992-03-24
Argenbright, Tony M.
Internal-combustion engines
Charge forming device
Fuel injection system
123 73C, F02D 1702, F02D 300, F02M 6910, F02B 110
Patent
active
050978110
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for operating a two-stroke internal combustion engine with an electronically controlled direct injection of the fuel into the cylinder, wherein the fuel injection is performed intermittently in the no-load and in the lower underload mode.
For two-stroke Otto engines it is known that by forming a mixture within the cylinder, i.e. by a fuel injection after the closing of the exhaust channels, the consumption values and the HC proportions in the exhaust gas can substantially be improved. By such a direct injection of the fuel a layering of the loading in the interior of the cylinder can be obtained in that, namely, the fuel is injected by means of the injection nozzle into defined areas of the cylinder and thus, in the moment of ignition, is in the region of the spark. However, it has been found that in the lower underload mode, in the thrust mode as well as in the no-load mode there are still ignition irregularities, which in these modes are assumed to result from the high proportion of old gas in the cylinder. It is assumed that the reason for this is that the fuel, although being injected into the correct area, does not mix sufficiently up to the moment of ignition within the large amount of old gas to form an explosive mixture with the fresh air introduced in relatively small amounts due to the throttle being closed in the underload, thrust and no-load modes. Only after several gas changes have occurred, the old gas is dislodged by fresh air such that the injected fuel can burn.
In DE-PS 913 835 this phenomenon of the no longer regular ignition is discussed and it is assumed that the cylinders of the two-stroke Otto engine are supplied with a too weak mixture and that therefrom the ignition difficulties result. For removing these difficulties it is suggested at the change-over from full load mode to underload mode to proceed from a control with diminishing gas pressure with a constant opening time of the injection valves to a control with increased constant gas pressure with reduced opening times of the injection valves. Thereby, the fuel supply to the cylinders is performed intermittently, and this only at each second third, fourth or fifth revolution or cycle. By this intermittent fuel supply the capability of the mixture to ignite is improved by the twofold repeated supply of fresh air between the injection intervals. These improvements by the intermittent operation are only possible by a comparatively high expenditure, because two control pumps are required, one of which is provided with a sloping edge control. The described design permits only an injection at each second cycle; it must be questioned whether thereby already a reliable ignition can be achieved.
From the journal "Kraftfahrzeugtechnik", Berlin 35 (1985), volume 7, pages 201 to 203, there is also known a two-stroke Otto engine with intermittent injection in the underload mode. By means of control electronics the amount of fuel as well as the moment in time are determined at which this amount of fuel is injected into the cylinder. For this a special pump-nozzle-system is being used. Thereby, the consumption and the exhaust gas values shall be improved.
The invention, thus, is based on the problem to provide a two-stroke combustion engine in which--particularly in the underload mode as well as in the no-load and the thrust modes--good circulation or running properties and a low underload consumption are guaranteed as well as increased requirements for low exhaust gas values can safely be obtained.
The inventive solution of this problem is to be seen in that there is provided a process for operating a two-stroke combustion engine with an electronically controlled direct fuel injection into the cylinder, wherein the fuel injection in the no-load and the lower underload mode is performed intermittently, characterized in that the electronic control for the intermittent operation of the injection nozzle additionally opens the throttle beyond the no-load or underload condition in order to supply a larger amount
REFERENCES:
patent: 2018426 (1935-10-01), Taber
patent: 2771867 (1956-11-01), Peras
patent: 4509488 (1985-04-01), Forster et al.
patent: 4768474 (1988-09-01), Fujimoto et al.
patent: 4991558 (1991-02-01), Daly et al.
Argenbright Tony M.
Ficht GmbH
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