Cylinder air/fuel ratio estimation system of internal combustion engine
AssigneeHonda Giken Kogyo Kabushiki Kaisha
InventorsMasaki Ueno, Yasunori Ehara, Masahiro Sato, Ken Ogawa
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Abstract
In a direct injection spark ignition engine which is operable in three operation modes including a stoichiometric air/fuel ratio operation mode, a pre-mixture combustion mode and a stratified combustion operation mode which are different in the desired air/fuel ratio and a single air/fuel ratio sensor installed downstream of the exhaust manifold, the sensor output is successively sampled and one from among the sampled data is selected based on the engine speed and engine load and selected one of the operation modes such that the air/fuel ratio at each cylinder can be accurately estimated for the selected operation mode under the engine operating conditions.
Claims28
A system for estimating an air/fuel ratio of each cylinder of an internal combustion engine having a plurality of cylinders which are connected to an exhaust system having an exhaust manifold, including:
- an air/fuel ratio sensor installed at or downstream of a confluence point of the exhaust manifold and generating an output indicative of an air/fuel ratio exhausted from the cylinders;
- air/fuel ratio sensor output sampling module which A/D converts the output of the air/fuel ratio sensor and stores successively as sampled data;
- engine operating condition detecting module which detects operating conditions of the engine including at least an engine speed and an engine load;
- sampled data selecting module which selects one from among the sampled data based on at least the engine speed and the engine load in the detected operating conditions of the engine, and estimates the air/fuel ratio of each cylinder from the selected sampled data based on a model describing a behavior of the exhaust manifold and designed based on assumption that the output of the air/fuel ratio sensor comprises a weight-average obtained by multiplying past firing histories of the cylinders by a weight coefficient and an observer for observing an internal state of the model,
- wherein the improvement comprises:
- the system includes:
- operation mode selecting module which selects an operation mode of the engine from at least a first operation mode in which a desired air/fuel ratio is set to be a stoichiometric air/fuel ratio, a second operation mode in which the desired air/fuel ratio is set to be an air/fuel ratio leaner than the stoichiometric air/fuel ratio and a third operation mode in which the desired air/fuel ratio is set to be an air/fuel ratio leaner than that of the second operation mode;
- and the sampled data selecting module selects the one from among the sampled data based on at least the engine speed, the engine load and the selected operation mode, and estimates the air/fuel ratio of each cylinder from the selected sample, based on the model and the observer, for the selected operation mode of the engine.
A system for estimating an air/fuel ratio of each cylinder of a direct injection spark ignition internal combustion engine having a plurality of cylinders which are connected to an exhaust system having an exhaust manifold, comprising:
- an air/fuel ratio sensor installed at or downstream of a confluence point of the exhaust manifold and generating an output indicative of an air/fuel ratio exhausted from the cylinders;
- air/fuel ratio sensor output sampling module which A/D converting the output of the air/fuel ratio sensor and stores successively as sampled data;
- engine operating condition detecting module which detects operating conditions of the engine including at least an engine speed and an engine load;
- operation mode selecting module which selects an operation mode of the engine from at least a first operation mode in which a desired air/fuel ratio is set to be a stoichiometric air/fuel ratio, a second operation mode in which the desired air/fuel ratio is set to be an air/fuel ratio leaner than the stoichiometric air/fuel ratio and a third operation mode in which the desired air/fuel ratio is set to be an air/fuel ratio leaner than that of the second operation mode;
- sampled data selecting module which selects one from among the sampled data based on at least the engine speed and the engine load in the detected operating conditions of the engine and the selected operation mode, and
- cylinder air/fuel ratio estimating module which estimates the air/fuel ratio of each cylinder for the selected operation mode from the selected sampled data, based on a model describing a behavior of the exhaust manifold and designed based on assumption that the output of the air/fuel ratio sensor comprises a weight-average obtained by multiplying past firing histories of the cylinders by a weight coefficient and an observer for observing an internal state of the model.
A system for estimating an air/fuel ratio of each cylinder of a direct injection spark ignition internal combustion engine having a plurality of cylinders which are connected to an exhaust system having an exhaust manifold, comprising:
- an air/fuel ratio sensor installed at or downstream of a confluence point of the exhaust manifold and generating an output indicative of an air/fuel ratio exhausted from the cylinders;
- air/fuel ratio sensor output sampling module which A/D converts the output of the air/fuel ratio sensor and stores successively as sampled data;
- engine operating condition detecting module which detects operating conditions of the engine including at least an engine speed and an engine load;
- operation mode selecting module which selects an operation mode of the engine from at least a first operation mode in which a desired air/fuel ratio is set to be a stoichiometric air/fuel ratio, a second operation mode in which the desired air/fuel ratio is set to be an air/fuel ratio leaner than the stoichiometric air/fuel ratio and a third operation mode in which the desired air/fuel ratio is set to be an air/fuel ratio leaner than that of the second operation mode;
- sampled data selecting module which selects one from among the sampled data based on at least the engine speed and the engine load in the detected operating conditions of the engine, and
- cylinder air/fuel ratio estimating module which estimates the air/fuel ratio of each cylinder from the selected sampled data, based on a model describing a behavior of the exhaust manifold and designed based on assumption that the output of the air/fuel ratio sensor comprises a weight-average obtained by multiplying past firing histories of the cylinders by a weight coefficient and an observer for observing an internal state of the model;
- wherein the cylinder estimating module includes:
- model weight coefficient changing module which changes the weight coefficient of the model and a gain matrix of the observer in response to the selected operation mode;
- and estimates the air/fuel ratio of each cylinder from the selected sample, based on the changed coefficient of the model and the changed gain matrix of the observer, for the selected operation mode of the engine.
A method of estimating an air/fuel ratio of each cylinder of an internal combustion engine having a plurality of cylinders which are connected to an exhaust system having an exhaust manifold and an air/fuel ratio sensor installed at or downstream of a confluence point of the exhaust manifold and generating an output indicative of an air/fuel ratio exhausted from the cylinders, including the steps of:
- (a) A/D converting the output of the air/fuel ratio sensor and storing successively as sampled data;
- (b) detecting operating conditions of the engine including at least an engine speed and an engine load;
- (c) selecting one from among the sampled data based on at least the engine speed and the engine load in the detected operating conditions of the engine, and for estimating the air/fuel ratio of each cylinder from the selected sampled data based on a model describing a behavior of the exhaust manifold and designed based on assumption that the output of the air/fuel ratio sensor comprises a weight-average obtained by multiplying past firing histories of the cylinders by a weight coefficient and an observer for observing an internal state of the model,
- wherein the improvement comprises:
- the method includes the step of:
- (d) selecting an operation mode of the engine from at least a first operation mode in which a desired air/fuel ratio is set to be a stoichiometric air/fuel ratio, a second operation mode in which the desired air/fuel ratio is set to be an air/fuel ratio leaner than the stoichiometric air/fuel ratio and a third operation mode in which the desired air/fuel ratio is set to be an air/fuel ratio leaner than that of the second operation mode;
- and the step (c) selects the one from among the sampled data based on at least the engine speed, the engine load and the selected operation mode, and estimating the air/fuel ratio of each cylinder from the selected sample, based on the model and the observer, for the selected operation mode of the engine.
A method of estimating an air/fuel ratio of each cylinder of a direct injection spark ignition internal combustion engine having a plurality of cylinders which are connected to an exhaust system having an exhaust manifold an air/fuel ratio sensor installed at or downstream of a confluence point of the exhaust manifold and generating an output indicative of an air/fuel ratio exhausted from the cylinders, comprising the steps of:
- (a) A/D converting the output of the air/fuel ratio sensor and storing successively as sampled data;
- (b) detecting operating conditions of the engine including at least an engine speed and an engine load;
- (c) selecting an operation mode of the engine from at least a first operation mode in which a desired air/fuel ratio is set to be a stoichiometric air/fuel ratio, a second operation mode in which the desired air/fuel ratio is set to be an air/fuel ratio leaner than the stoichiometric air/fuel ratio and a third operation mode in which the desired air/fuel ratio is set to be an air/fuel ratio leaner than that of the second operation mode;
- (d) selecting one from among the sampled data based on at least the engine speed and the engine load in the detected operating conditions of the engine and the selected operation mode, and
- (e) estimating the air/fuel ratio of each cylinder for the selected operation mode from the selected sampled data, based on a model describing a behavior of the exhaust manifold and designed based on assumption that the output of the air/fuel ratio sensor comprises a weight-average obtained by multiplying past firing histories of the cylinders by a weight coefficient and an observer for observing an internal state of the model.
A method of estimating an air/fuel ratio of each cylinder of a direct injection spark ignition internal combustion engine having a plurality of cylinders which are connected to an exhaust system having an exhaust manifold and an air/fuel ratio sensor installed at or downstream of a confluence point of the exhaust manifold and generating an output indicative of an air/fuel ratio exhausted from the cylinders, comprising the steps of;
- (a) A/D converting the output of the air/fuel ratio sensor and storing successively as sampled data;
- (b) detecting operating conditions of the engine including at least an engine speed and an engine load;
- (c) selecting an operation mode of the engine from at least a first operation mode in which a desired air/fuel ratio is set to be a stoichiometric air/fuel ratio, a second operation mode in which the desired air/fuel ratio is set to be an air/fuel ratio leaner than the stoichiometric air/fuel ratio and a third operation mode in which the desired air/fuel ratio is set to be an air/fuel ratio leaner than that of the second operation mode;
- (d) selecting one from among the sampled data based on at least the engine speed and the engine load in the detected operating conditions of the engine, and
- (e) estimating the air/fuel ratio of each cylinder from the selected sampled data, based on a model describing a behavior of the exhaust manifold and designed based on assumption that the output of the air/fuel ratio sensor comprises a weight-average obtained by multiplying past firing histories of the cylinders by a weight coefficient and an observer for observing an internal state of the model;
- wherein the step (e) includes the step of:
- (f) changing the weight coefficient of the model and a gain matrix of the observer in response to the selected operation mode;
- and estimates the air/fuel ratio of each cylinder from the selected sample, based on the changed coefficient of the model and the changed gain matrix of the observer, for the selected operation mode of the engine.
Dependencies are inferred from the claim text.