Engine Purge Control for O2 Sensor Accuracy
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Solution Overview
Problem
The existing control systems for engine purge gas supply during deceleration fuel cutoff can falsely determine an O2 sensor as abnormal due to the presence of evaporated fuel in the purge gas, leading to accuracy degradation in abnormality determination.
Innovation Solution
A control system that includes a purge restricting module to limit or prohibit the supply of purge gas during abnormality determination, ensuring the air-fuel ratio in the combustion chamber exceeds a predetermined ratio to prevent false abnormality detection, and estimates the evaporated fuel concentration to adjust the purge gas supply accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If purge gas is supplied to the intake passage during deceleration fuel cutoff, then evaporated fuel overflow from the canister is suppressed, but the speed of output value change of the O2 sensor decreases causing false abnormality determination
Solution Approach 1:
The control unit determines whether to perform the purge based on the output value of the O2 sensor before actually executing the purge operation. When the O2 sensor output value indicates a state where abnormality determination should be avoided, the purge is restricted or skipped, preventing the sensor output change speed from decreasing and thus avoiding false abnormality determination.
Solution Approach 2:
The control unit continuously monitors the output value of the O2 sensor and uses this feedback information to decide whether to execute the purge operation. By checking the sensor output value before purging, the system adjusts its behavior based on real-time sensor state, preventing false readings that would occur if purge gas were supplied during abnormality determination.
2Object-generated harmful factors
If purge gas is supplied during deceleration fuel cutoff, then canister overflow is prevented, but the air-fuel ratio in the combustion chamber changes affecting sensor response
Solution Approach 1:
The control unit checks the O2 sensor output value before executing the purge operation to determine whether the air-fuel ratio is in a stable state suitable for purging. This preliminary check prevents purging when the air-fuel ratio is unstable, thereby avoiding excessive changes in combustion chamber composition that would affect sensor response.
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 effectively suppresses the degradation in accuracy of O2 sensor abnormality determination by minimizing the impact of purge gas on the sensor's output change speed, ensuring accurate assessment even when the purge is performed during abnormality determination.
Implementation Method 1
a linear O2 sensor for detecting an oxygen concentration within exhaust gas for the purpose of performing a feedback control of an air-fuel ratio within a combustion chamber is provided upstream of the exhaust emission control catalyst
Implementation Method 2
the unburned evaporated fuel can be purified by an exhaust emission control catalyst provided in the exhaust passage
Implementation Method 3
a purge gas containing evaporated fuel desorbed from a canister is supplied to an intake passage of the engine
Data Source
AI summary
A control system of an engine in which a purge gas containing evaporated fuel desorbed from a canister is supplied to an intake passage of the engine is provided. The control system includes a deceleration fuel cutoff module for performing a deceleration fuel cutoff to stop a fuel supply from an injector to the engine when a predetermined deceleration fuel cutoff condition is satisfied in a decelerating state of the engine, a purge unit for purging by supplying the purge gas to the intake passage during the deceleration fuel cutoff, an O2 sensor provided in an exhaust passage of the engine, an abnormality determining module for determining an abnormality of the O2 sensor based on a change of an output value of the O2 sensor that is caused by the deceleration fuel cutoff, and a purge restricting module for restricting the purge during the abnormality determination.