Air/fuel ratio control system for outboard motor engine
AssigneeHonda Motor Co., Ltd.
InventorsTomohiro Miyauchi, Kazuhiro Sato
Life of this patent
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Abstract
In an air/fuel ratio control system for an outboard motor engine, a learned correction coefficient KTIMn used in open-loop control for correcting a basic fuel injection amount to be supplied to the engine, is updated only when the manifold absolute pressure PBA (indicative of engine load) is within a predetermined range relative to the engine speed NE concerned. As a result, the air/fuel ratio can be accurately controlled to one other than the stoichiometric air/fuel ratio, even when an O2 sensor that produces an output whose property only changes near the stoichiometeic air/fuel ratio is used.
Claims10
A system for controlling an air/fuel ratio of an internal combustion engine mounted on an outboard motor, comprising:
- detectors detecting operational state of the engine including an engine speed and engine load;
- an oxygen sensor disposed at an exhaust system of the engine and producing an output whose property changes near a stoichiometric air/fuel ratio;
- a first controller controlling the air/fuel ratio of the engine to the stoichiometric air/fuel ratio by correcting a basic fuel injection quantity to be supplied to the engine determined based on the detected operational state of the engine, by a feedback correction coefficient determined based on the output of the oxygen sensor;
- a memory having a plurality of storage areas divided by the engine speed and engine load and each storing a learned correction coefficient that is used for correcting the basic fuel injection quantity;
- a learned correction coefficient calculator calculating the learned correction coefficient based on the feedback correction coefficient;
- a learned correction coefficient updater updating the leaned correction coefficient by writing the calculated learned correction coefficient over the stored learned correction coefficient, when the engine load is within a predetermined range relative to the engine speed;
- and
- a second controller retrieving the learned correction coefficient from the engine speed and engine load and controlling the air/fuel ratio to one other than the stoichiometric air/fuel ratio by correcting the basic fuel injection quantity by at least the retrieved learned correction coefficient.
3 The system according to claim 2, wherein the second controller controls the air/fuel ratio to the one other than the stoichiometric air/fuel ratio, when a difference between the feedback correction coefficient and the updated learned correction coefficient is equal to or less than a predetermined value.
A method of controlling an air/fuel ratio of an internal combustion engine mounted on an outboard motor, comprising steps of:
- (a) detecting operational state of the engine including an engine speed and engine load;
- (b) controlling the air/fuel ratio of the engine to the stoichiometric air/fuel ratio by correcting a basic fuel injection quantity to be supplied to the engine determined based on the detected operational state of the engine, by a feedback correction coefficient determined based on an output of an oxygen sensor disposed at an exhaust system of the engine and producing the output whose property changes near a stoichiometric air/fuel ratio;
- (c) preparing a memory having a plurality of storage areas divided by the engine speed and engine load and each storing a learned correction coefficient that is used for correcting the basic fuel injection quantity;
- (d) calculating the learned correction coefficient based on the feedback correction coefficient;
- (e) updating the leaned correction coefficient by writing the calculated learned correction coefficient over the stored learned correction coefficient, when the engine load is within a predetermined range relative to the engine speed;
- and
- (f) retrieving the learned correction coefficient from the engine speed and engine load and controlling the air/fuel ratio to one other than the stoichiometric air/fuel ratio by correcting the basic fuel injection quantity by at least the retrieved learned correction coefficient.
Dependencies are inferred from the claim text.