Individual cylinder air/fuel ratio feedback control system
First Claim
1. A method for correcting air/fuel ratio for each of N cylinders via an oxygen sensor positioned in the exhaust of an internal combustion engine, comprising the steps of:
- sampling the sensor once each period associated with a combustion event in one of the cylinders to generate N output signals;
storing each of said N output signals;
concurrently reading each of said N output signals from said storage once each output period to define N nonperiodic signals each being related to the air/fuel ratio of a corresponding cylinder wherein said output period is defined as a predetermined number of engine revolutions required for each of the cylinders to have a single combustion event;
generating N feedback correction signals from said N nonperiodic signals; and
correcting a mixture of air and fuel supplied to each of the cylinders in response to each of said feedback correction signals for achieving a desired air/fuel ratio in each of the cylinders.
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Abstract
An air/fuel ratio control system and method for correcting the air/fuel ratio for each of N cylinders in an internal combustion engine having electronically actuated fuel injectors coupled to each cylinder. A first air/fuel controller provides a desired fuel command for maintaining an average air/fuel ratio among the cylinders in response to an exhaust gas oxygen sensor and a measurement of inducted air flow. A second air/fuel controller generates N trim signals by sampling the exhaust gas oxygen sensor once each combustion period, synchronizing the samples to generate N nonperiodic samples, correlating the samples with the corresponding combustion event and integrating. The fuel command to each fuel injector is then trimmed for operating each cylinder at a desired air/fuel ratio.
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Citations
14 Claims
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1. A method for correcting air/fuel ratio for each of N cylinders via an oxygen sensor positioned in the exhaust of an internal combustion engine, comprising the steps of:
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sampling the sensor once each period associated with a combustion event in one of the cylinders to generate N output signals; storing each of said N output signals; concurrently reading each of said N output signals from said storage once each output period to define N nonperiodic signals each being related to the air/fuel ratio of a corresponding cylinder wherein said output period is defined as a predetermined number of engine revolutions required for each of the cylinders to have a single combustion event; generating N feedback correction signals from said N nonperiodic signals; and correcting a mixture of air and fuel supplied to each of the cylinders in response to each of said feedback correction signals for achieving a desired air/fuel ratio in each of the cylinders. - View Dependent Claims (2, 3)
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4. A method for correcting air/fuel ratio for each of N cylinders via an oxygen sensor positioned in the exhaust of an internal, combustion engine, comprising the steps of:
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delivering a desired fuel charge to each of the cylinders to provide a desired average air/fuel ratio among all the cylinders in response to the oxygen sensor; sampling the oxygen sensor once each period associated with a combustion event in one of the cylinders to generate N output signals; synchronizing said N output signals once each output period for generating N nonperiodic correction signals each being related to the air/fuel ratio of a corresponding cylinder wherein said output period is defined as a predetermined number of engine revolutions required for each of the cylinders to have a single combustion event; and correcting said desired fuel charge to generate a separate corrected fuel charge for each of the cylinders in response to each of said correction signals thereby providing a desired air/fuel ratio for each of the cylinders. - View Dependent Claims (5, 6)
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7. An apparatus for correcting air/fuel ratio for each of N cylinders via an oxygen sensor positioned in the exhaust of an internal combustion engine, comprising:
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sampling means for sampling the sensor once each period associated with a combustion event in one of the cylinders to generate and store N output signals; synchronizing means for concurrently reading each of said N output signals once each output period to define N nonperiodic signals each being related to the air/fuel ratio of a corresponding cylinder wherein said output period is defined as a predetermined number of engine revolutions required for each of the cylinders to have a single combustion event; generating means for generating N feedback correction signals from said N nonperiodic signals; and correcting means for correcting a mixture of air and fuel supplied to each of the cylinders in response to each of said feedback correction signals for achieving a desired air/fuel ratio in each of the cylinders. - View Dependent Claims (8, 9)
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10. An apparatus for correcting air/fuel ratio for each of N cylinders via an oxygen sensor positioned in the exhaust of an internal combustion engine, comprising:
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a first air/fuel controller for adjusting a desired fuel charge delivered to each of the cylinders to provide a desired average air/fuel ratio among all the cylinders in response to the oxygen sensor; sampling means for sampling the oxygen sensor once each period associated with a combustion event in one of the cylinders to generate N output signals; synchronizing means for synchronizing said N output signals once each output period for generating N nonperiodic correction signals each being related to the air/fuel ratio of a corresponding cylinder wherein said output period is defined as a predetermined number of engine revolutions required for each of the cylinders to have a single combustion event; and a second air/fuel controller for correcting said desired fuel charge to generate a separate corrected fuel charge for each of the cylinders in response to each of said correction signals thereby providing a desired air/fuel ratio for each of the cylinders. - View Dependent Claims (11, 12, 13)
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14. An apparatus for correcting air/fuel ratio of each of N cylinders in an internal combustion engine having an air/fuel intake manifold with N fuel injectors coupled thereto in proximity to the N cylinders, comprising:
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an exhaust gas oxygen sensor for providing an indication of air/fuel ratio from the engine exhaust; an airflow sensor for providing a measurement of airflow inducted into the engine; first air/fuel control means responsive to both said exhaust gas oxygen sensor and said airflow sensor for providing a fuel demand signal related to a desired average air/fuel ratio among the N cylinders; sampling means for sampling the oxygen sensor once each period associated with a combustion event in one of the cylinders to generate N output signals; synchronizing means for synchronizing said N output signals once each output period for generating N nonperiodic correction signals each being related to the air/fuel ratio of a corresponding cylinder wherein said output period is defined as a predetermined number of engine revolutions required for each of the cylinders to have a single combustion event; and a second air/fuel controller for correcting said desired fuel charge to generate a separate corrected fuel charge for each of the cylinders in response to each of said correction signals thereby providing a desired air/fuel ratio for each of the cylinders.
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Specification