Internal combustion engine cylinder air-fuel ratio imbalance detection and controls
AssigneeCummins Inc.
InventorsAvra Brahma, Yongsoon Yoon
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Abstract
A system for detecting and controlling air-fuel ratio imbalance conditions between cylinders of an internal combustion engine having a plurality of cylinders is disclosed.
Claims13
A method for diagnosing an air-fuel ratio (AFR) imbalance condition during operation of an internal combustion engine, comprising:
- determining one or more enable conditions for diagnosing the AFR imbalance condition are met;
- in response to one or more enable conditions being met, determining a first fundamental frequency of a lambda control feedback correction input using a time domain method;
- determining a second fundamental frequency of a sensed output lambda in an exhaust flow from one or more cylinders of the internal combustion engine using a time domain method;
- determining a monitoring parameter associated with the AFR imbalance condition in response to the first fundamental frequency and the second fundamental frequency;
- comparing the monitoring parameter to a pre-defined threshold;
- and
- if the monitoring parameter is greater than the pre-defined threshold, determine and/or output of an AFR imbalance fault or otherwise declare an AFR imbalance pass.
A method for diagnosing an air-fuel ratio (AFR) imbalance condition during operation of an internal combustion engine, comprising:
- determining one or more monitoring conditions are met to enable detection of an AFR imbalance condition;
- in response to one or more enable conditions being met, filling a buffer with a plurality of inputs to use in a sliding discrete fourier transform (SDFT) analysis, the plurality of inputs including a sensed output lambda in an exhaust flow from one or more cylinders of the internal combustion engine;
- determining SDFTs at various frequency components including cycle frequency and its harmonics;
- determining a group energy from the determined SDFTs;
- determining a monitoring parameter in response to a mean value of the group energy around the cycle frequency during the monitoring period;
- and
- comparing the monitoring parameter to a pre-defined threshold and if the monitoring parameter is greater than the threshold, declare a fault relating to the AFR imbalance or otherwise declare an AFR imbalance pass.
A method for diagnosing an air-fuel ratio (AFR) imbalance condition during operation of an internal combustion engine, comprising:
- determining if one or more monitoring conditions are met to enable detection of an AFR imbalance condition;
- initializing and executing a Kalman Filter or an RLS estimator to estimate time-varying auto-regressive (TV AR) model coefficients;
- determining a power spectral density (PSD) at cycle frequency from identified (TV AR) model coefficients;
- determining a monitoring parameter from a mean value of the time-varying PSD at cycle frequency over a monitoring period;
- and
- comparing the monitoring parameter to a pre-defined threshold and in response to the monitoring parameter being greater than the threshold declare a fault.
A method for diagnosing an air-fuel ratio (AFR) imbalance condition during operation of an internal combustion engine, comprising:
- determining if one or more monitoring conditions are met to enable detection of an AFR imbalance condition;
- determining a monitoring parameter based on a sensed lambda output from an oxygen sensor measuring an exhaust oxygen of the internal combustion engine;
- and
- comparing the monitoring parameter to a pre-defined threshold and in response to the monitoring parameter being greater than the threshold declare a fault.
Dependencies are inferred from the claim text.