Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1990-06-21
1991-06-04
Wolfe, Willis R.
Internal-combustion engines
Charge forming device
Fuel injection system
36443105, F02D 4114, F02D 4140
Patent
active
050205021
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method for controlling the quantity of fuel metered individually to each cylinder of an internal combustion engine by means of an injection device, and a device for carrying out this method.
BACKGROUND OF THE INVENTION
A known control device exhibits a precontrol timer which outputs precontrol times in dependence on rotational speed and quantity of air drawn in with a particular precontrol time applying jointly to all injection valves. A lambda control operating uniformly on all cylinders is superposed on the precontrol.
In the known control device it is a problem that variations in characteristics of the different cylinders are not taken into consideration, which can lead to an individual cylinder of the internal combustion engine delivering an exhaust gas which is relatively rich in pollutants. It has been attempted up till now to keep the cylinder variations small, particularly by designing the internal combustion engine in such a manner that very similar conditions prevail in all gas paths.
A development of such a control device is disclosed in U.S. Pat. No. 4,483,300.
This control device determines a pulse time, which is effective individually for each cylinder, for metering fuel for each cylinder based on variables which are the same for each cylinder. The control device also determines multiplicative correction factors which are specific for each cylinder.
SUMMARY OF THE INVENTION
The invention is based on the object of providing a method and a control device of the type initially mentioned which has a compensating effect with respect to cylinder variations. The invention is also based on the object of providing a method for adjusting parameters of such a device.
The method according to the invention is characterized by the fact that it compensates variations in the characteristics of the different cylinders of an internal combustion engine by modifying the known precontrol by means of individual correction values which are formed from a combination of individual factors and individual summands. Thus, the injection devices are not all driven with the same injection time but the precontrol time for each cylinder is corrected in such a manner that the exhaust gas from all individual cylinders essentially exhibits the same composition.
The method according to the invention is further characterized in that a determination is made for which cylinder the lambda value measured in the exhaust gas deviates from a predetermined value and then the corrective value or values for this cylinder are changed until the pregiven lambda value results.
In order to store the individual correction values, the device according to the invention has an individual-value memory. A logic device logically combines the common precontrol time with the individual correction values.
If a lambda probe is used for the measurement which measures from the rich to the lean range without jump characteristics, for example a probe of the pump current type with essentially linear characteristic, there are relatively few problems in detecting deviations from lambda = 1 and setting to lambda = 1. However, considerable complexity is required in processing the signal from the probe as such probes are relatively sensitive not only to fluctuations of the exhaust gas composition but also to pressure fluctuations. Nernst-type probes present fewer problems with respect to the latter. It is also recommended to use these probes because the probe frequently already installed in the vehicle, which, as a rule, is a Nernst-type probe, can then be used as measuring probe. When such a probe type is used, a method by successive approximation is proposed. In this method, the injection time is changed in such a manner that, for example, a distinctly lean exhaust gas should be achieved. If this is not the case, this indicates a deviation of the characteristics of the cylinder monitored from the characteristics of the other cylinders in the direction of a rich setting, to an extent which must be compensate
REFERENCES:
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patent: 4483300 (1984-11-01), Hosaka et al.
patent: 4627402 (1986-12-01), Saito et al.
patent: 4703430 (1987-10-01), Amano et al.
patent: 4766870 (1988-08-01), Nakajima et al.
patent: 4869222 (1989-09-01), Klassen
patent: 4934328 (1990-06-01), Ishii et al.
patent: 4939658 (1990-07-01), Sekozawa et al.
patent: 4962741 (1990-10-01), Cook et al.
Ottesen Walter
Robert & Bosch GmbH
Wolfe Willis R.
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