Method for air/fuel imbalance detection
AssigneeFord Global Technologies, LLC
InventorsJohn Eric Rollinger, Robert Roy Jentz, Michael Igor Kluzner
Life of this patent
Estimating the term…
Abstract
Methods and systems are described for monitoring air/fuel imbalance in cylinders of an engine. In one example method, air/fuel ratio of a cylinder is modulated to produce a series of rich, lean, and stoichiometric conditions in the cylinder and corresponding crank accelerations are measured to calculate a peak function indicating an air/fuel ratio in the cylinder. The peak function is calculated over a plurality of modulations to provide a more reliable computation of the air/fuel ratio of the cylinder and its deviation from a pre-determined air/fuel ratio.
Claims20
A system, comprising:
- an engine with a first cylinder and a second cylinder;
- a crankshaft sensor;
- a first fuel injector coupled to the first cylinder and a second fuel injector coupled to the second cylinder;
- and
- a controller configured with instructions stored in non-transitory memory and executable by a processor for:
- modulating air/fuel ratio of the first cylinder in a series of rich, lean, and stoichiometric conditions by varying fuel injected by the first fuel injector;
- modulating air/fuel ratio of the second cylinder in a series of lean, rich, and stoichiometric conditions by varying fuel injected by the second fuel injector;
- measuring crank accelerations via the crankshaft sensor generated by the modulating;
- learning a first air/fuel ratio of the first cylinder and learning a second air/fuel ratio of the second cylinder based on the crank accelerations;
- computing a weighted average of air/fuel ratio based on learned air/fuel ratios for each of the first cylinder and second cylinder;
- and
- indicating degradation of the first cylinder responsive to a deviation of the first air/fuel ratio from the weighted average being higher than a threshold deviation.
A method for an engine, comprising:
- modulating an air/fuel ratio in a cylinder to produce a series of lean, rich, and stoichiometric conditions of the cylinder;
- identifying a potential air/fuel imbalance in the cylinder based on crank accelerations generated during the modulating;
- and
- responsive to a purge operation in the engine, disabling the modulating and ceasing the identifying of the potential air/fuel imbalance.
A method, comprising:
- modulating an air/fuel ratio in a cylinder of an engine to generate a series of rich, lean, and stoichiometric conditions;
- and
- identifying potential air/fuel imbalance in the cylinder based on a peak function, the peak function determined over a plurality of modulations of the air/fuel ratio, wherein the peak function is computed as a reciprocal of a sum of squares of crank accelerations over the plurality of modulations.
Dependencies are inferred from the claim text.