Air-Fuel Ratio Control via Sequential Cylinder Firing
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Solution Overview
Problem
Existing methods struggle to accurately determine air-fuel ratio imbalances and injector errors in engine cylinders, especially in multi-cylinder engines, due to sensor limitations and interference from purge and PCV hydrocarbons, leading to inefficiencies and emissions issues.
Innovation Solution
A method involving deceleration fuel shut-off (DFSO) events where each cylinder group is sequentially fired with consecutive fuel pulses of varying widths, allowing for independent learning of injector errors and air-fuel ratio imbalances, independent of purge or PCV effects, by analyzing lambda deviations and crankshaft acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If oxygen sensor is used to determine air-fuel ratio variation between engine cylinders, then air-fuel ratio monitoring is enabled, but measurement precision deteriorates due to exhaust gases being a combination from different cylinders and exhaust system geometry bias
Solution Approach 1:
The exhaust system is segmented into individual cylinder exhaust paths, each equipped with its own oxygen sensor. This segmentation allows each sensor to measure exhaust gases from a specific cylinder rather than receiving a mixed signal from all cylinders, thereby recovering cylinder-specific air-fuel ratio information that was lost in the combined exhaust stream.
Solution Approach 2:
Individual oxygen sensors are introduced as intermediaries between each cylinder's exhaust gases and the measurement system. These sensors act as mediators that capture cylinder-specific exhaust composition data before the gases mix in the exhaust manifold, enabling precise measurement of air-fuel ratio variations for each cylinder independently.
2Adaptability or versatility
If AFR monitoring is scheduled during purge or PCV enabled conditions, then comprehensive engine operation coverage is achieved, but measurement precision deteriorates due to hydrocarbon interference from purge and PCV
Solution Approach 1:
The harmful hydrocarbon interference from purge and PCV systems is extracted and separated from the AFR monitoring process. By identifying and excluding time periods when purge or PCV is active, the system removes the contaminating influence of these systems on the oxygen sensor measurements, allowing accurate AFR monitoring only during clean operating conditions.
Solution Approach 2:
The system dynamically changes the operational parameter of AFR monitoring by enabling it only during specific engine conditions when purge and PCV are disabled. This conditional monitoring approach changes the temporal parameter of when measurements are taken, avoiding periods when hydrocarbon interference would degrade measurement precision.
3Adaptability or versatility
If dual fuel injection systems (DI and PFI) operate simultaneously, then fuel flexibility is improved, but device complexity increases for differentiating injector errors and AFR imbalance
Solution Approach 1:
The fuel injection system is segmented into distinct direct injection (DI) and port fuel injection (PFI) subsystems, each with separate control and monitoring. This segmentation allows the system to independently manage and diagnose each injection type, simplifying the differentiation of injector errors by treating them as separate entities rather than a mixed system.
Solution Approach 2:
The system implements selective monitoring where AFR measurement is performed only during conditions when one injection type is active or during specific cylinder events. This partial action approach reduces the complexity of differentiating between DI and PFI errors by limiting measurements to conditions where the source of fuel delivery is known or isolated.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the detection of air-fuel ratio imbalances and injector errors, enhancing fuel efficiency and reducing emissions by enabling learning across a wider range of engine conditions without compromising canister purge efficiency.
Implementation Method 1
One way to determine air-fuel ratio variation between engine cylinders is to sense engine exhaust gases via an oxygen sensor
Implementation Method 2
based on a lambda deviation between the first and second pulses, learning a fuel error for the injector and an air-fuel ratio imbalance for each cylinder
Implementation Method 3
Additionally or optionally crankshaft acceleration may be estimated at a desired AFR
Data Source
AI summary
Methods and systems are provided for learning fuel injector error for cylinder groups during a deceleration fuel shut-off (DFSO), where all cylinders of an engine are deactivated, sequentially firing each cylinder of a cylinder group, each cylinder fueled via consecutive first and second fuel pulses of differing fuel pulse width from an injector. Based on a lambda deviation between the first and second pulses, a fuel error for the injector and an air-fuel ratio imbalance for each cylinder is learned. Alternatively or additionally, a difference in crankshaft acceleration between the first and second pulses relative to the expected deviation may be used to learn torque error, and adjust fuel injector error and air-ratio imbalance for each cylinder.