METHOD FOR REDUCING CYLINDER AIR-FUEL RATIO IMBALANCE
First Claim
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1. A method comprising:
- sampling an engine speed signal synchronous with engine firing;
filtering the sampled engine speed signal via a Notch filter; and
indicating a cylinder air/fuel imbalance based on an output of the Notch filter relative to a threshold.
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Abstract
Methods and systems are described for monitoring air/fuel imbalance in cylinders of an engine. Engine speed signals are sampled and then run through a notch filter set to the sampling frequency. Based on a first frequency content of the resulting filtered engine speed, cylinder imbalance is detected and addressed.
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Citations
20 Claims
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1. A method comprising:
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sampling an engine speed signal synchronous with engine firing; filtering the sampled engine speed signal via a Notch filter; and indicating a cylinder air/fuel imbalance based on an output of the Notch filter relative to a threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for an engine, comprising:
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sampling crankshaft acceleration during a power stroke of a firing cylinder; normalizing the sampled acceleration based on a time of the sampling within the power stroke; filtering the normalized sampled acceleration via a band stop filter; and when noise at the filter is lower, indicating cylinder air/fuel imbalance based on the output of the band stop filter relative to a threshold. - View Dependent Claims (13, 14, 15, 16, 17)
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18. An engine system, comprising:
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an engine including a plurality of cylinders; a fuel injector for delivering fuel to at least one of the plurality of cylinders; an intake throttle coupled to an intake passage of the engine; a crankshaft sensor coupled to a crankshaft tooth wheel; and a controller with computer-readable instructions stored on non-transitory memory for; sampling an output of the crankshaft sensor synchronous with a cylinder firing event; correcting the sampled output based on a learned tooth wheel profile; normalizing the corrected sampled output based on a timing of the sampling relative to a power stroke of the cylinder firing event; filtering the corrected output via a Notch filter, a parameter of the Notch filter based on a frequency of the sampling; estimating a cylinder air/fuel imbalance based on the filtering; and adjusting one or more of the intake throttle and the fuel injector based on the estimated cylinder air/fuel imbalance. - View Dependent Claims (19, 20)
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Specification