Air/fuel imbalance monitor using an oxygen sensor
AssigneeFors Global Technologies, LLC
InventorsKen John Behr, Has R Patel, Michael Igor Kluzner, Bob Roy Jentz
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Abstract
Air/fuel imbalance monitoring systems and methods for monitoring air/fuel ratio imbalance of an internal combustion engine are disclosed. In one embodiment, an oxygen sensor is sampled above cylinder firing frequency and a ratio of data from at least one window over a total number of windows is determined. The approach can be used to indicate imbalances between engine cylinders.
Claims20
A method for monitoring air/fuel of an engine, comprising:
- routing exhaust gas from a group of cylinders to an oxygen sensor;
- and
- sampling the oxygen sensor above a firing frequency of the group of cylinders;
- determining a difference between the samples over a window interval;
- and
- indicating an air/fuel imbalance in the group of cylinders when a ratio of at least the window interval over a total number of window intervals exceeds a threshold.
A system for monitoring air/fuel ratio imbalance of an internal combustion engine having a first group of engine cylinders and a second group of engine cylinders, comprising:
- a first exhaust gas oxygen sensor coupled downstream of, and receiving exhaust gas from, only the first group of engine cylinders;
- and
- a controller configured to, during selected operating conditions including when engine speed is below a threshold speed, sample an oxygen sensor signal above a firing frequency of said first group of engine cylinders, separate higher frequencies from the oxygen sensor signal forming a high frequency oxygen sensor signal, determine a difference between samples of the high frequency oxygen sensor signal, indicate that air/fuel of at least one cylinder in the first group is imbalanced based on the high frequency oxygen sensor signal, and adjust fuel injection to the first group based on the high frequency oxygen sensor signal.
A method for monitoring air/fuel ratio imbalance of an internal combustion engine having one or more engine cylinder banks, each of the one or more engine cylinder banks including a plurality of engine cylinders and a proportional oxygen sensor positioned at or downstream of a confluent point of an exhaust manifold of the internal combustion engine where various sub-branches of the exhaust manifold leading from individual engine cylinders of the plurality of engine cylinders gather but upstream of a confluent point where branches of the exhaust manifold leading from individual engine cylinder banks gather, the method comprising:
- receiving a signal detected by the proportional oxygen sensor, the signal containing a high frequency component that is related to cylinder-to-cylinder air/fuel ratio dispersion among the plurality of engine cylinders;
- determining the high frequency component of the signal that is related to cylinder-to-cylinder air/fuel ratio dispersion among the plurality of engine cylinders, which includes determining a hash of the first signal by taking a difference between consecutive samples of the signal and producing a difference signal;
- determining air/fuel ratio imbalance of the internal combustion engine based on the high frequency component of the signal, which includes comparing the difference signal with a predetermined threshold, integrating the difference signal over an engine revolution window that includes 100 engine revolutions to obtain an integrated difference signal if the difference signal is beyond the predetermined threshold, recording a failed engine revolution window with air/fuel ratio imbalance if the integrated difference signal is beyond a second predetermined threshold, determining an air/fuel ratio imbalance index based on a fraction of failed engine revolution windows out of a total number of engine revolution windows monitored, and indicating a detected air/fuel ratio imbalance for the plurality of engine cylinders if the air/fuel ratio imbalance index is greater than the second predetermined threshold;
- and
- determining whether the detected air/fuel ratio imbalance is leaning towards fuel rich or fuel lean based on a comparison of the signal and a commanded air/fuel ratio.
Dependencies are inferred from the claim text.