Method of cylinder-selective control of an internal combustion e

Details Method of cylinder-selective control of an internal combustion e Method of cylinder-selective control of an internal combustion e

1998-04-16

2000-07-04

Kwon, John

Internal-combustion engines

Charge forming device

Including means responsive to instantaneous change in engine...

731173, F02M 700

Patent

active

060823305

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a method for the cylinder-selective control of a multi-cylinder, self-ignition, four-stroke internal combustion engine with cylinder-selective fuel injection, in which method is based on the rotational crankshaft angle and the instantaneous rotational crankshaft speed, as well as a device for carrying out this method.
When compared to an internal combustion engine with spark ignition, e.g. an Otto engine, an internal combustion engine with self-ignition, e.g. a diesel engine, offers fewer options for influencing the combustion method. Thus, the mixture preparation options of an Otto engine are not applicable at all. The operating principle for the diesel engine only permits influencing the start of the injection and the amount of fuel that is injected. Unavoidable differences in the components result in undefined variations in the behavior of the individual cylinders, which can lead to shortcomings with respect to fuel consumption, emission of harmful substances, vibration behavior, synchronizing behavior, acoustics and service life.
All of the component differences here must be understood to be deviations of the diesel engine components from their theoretical ideal value. Said component differences result from unavoidable production tolerances, as well as can be caused during the operation of the internal combustion engine through abrasion, deformation, deposits etc.
The shortcomings caused by the component differences above all concern the differences in those components diesel engine, which play a part in the fuel feed or the combustion operation.
Particularly encumbered with problems are the injection nozzles, for example, which have to meet the requirement that all injection nozzles of a diesel engine must have the exact same hydraulic flow rate for the fuel. This requirement is difficult to realize, owing to the strong dependence of the hydraulic flow rate on the condition of the injection nozzle bore or the fuel temperature or the injection nozzle temperature. A reduction in the hydraulic fuel flow rate for an injection nozzle of a diesel engine during the combustion cycle here leads to a reduction of the mean pressure in the respective cylinder and thus also to irregularities in the crankshaft rotations. The mean pressure is a value that includes the course of the combustion chamber pressure during the combustion cycle of a cylinder, and which can serve as a measure for the energy converted in this cylinder.
The differences in the mean pressure for the individual cylinders lead to different effects in the various operational ranges of the diesel engine. As a result of irregularities in the crankshaft rotation, vehicle parts such as steering wheel, mirror, etc. are stimulated to vibrate during the idling. In the partial load range, this causes an increased emission of pollutants or an increase in the fuel consumption, while in the full load range, the diesel engine does not reach its maximum performance level. The increased stress on the individual cylinders leads to a decrease in the service life of the diesel engine.
It is the object of the invention to specify a method for the control of self-igniting, four-stroke internal combustion engines of the aforementioned type, which method minimizes the effects of differences in the components for the fuel feed and the combustion system to make possible further improvements in the engine characteristics, e.g., the fuel consumption.
This object is achieved in accordance in that the invention with different parameters are derived in dependence on the rotational speed from the course of the curve of the rotational crankshaft speed, which parameters are correlated as closely as possible with the respective mean pressure in the combustion chambers of the internal combustion engine, and from which cylinder-selective correction values for the cylinder-selective equalizing of the mean pressures are determined and used.
In a modification of the invention, correction values can be determined, following the equa

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