Air-Fuel Ratio Control System Cold Startup Integral Delay
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Solution Overview
Problem
Existing air-fuel ratio control systems for internal combustion engines face challenges in maintaining accurate control precision, especially during cold startup, as the integral value for PI control deviates significantly after fuel amount increase control, leading to suboptimal exhaust emission control.
Innovation Solution
Implementing a control method that delays the integration of the integral correction value until a predetermined period after cold startup, allowing for immediate feedback control while preventing large deviations in the integral value, thereby maintaining accurate air-fuel ratio control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If F/B control is started immediately after cold startup, then exhaust emission control is improved, but the integral value for PI control deviates significantly leading to control precision degradation
Solution Approach 1:
The patent applies preliminary action by performing fuel amount increase control before F/B control is fully activated. The fuel supply amount is increased from cold startup until a predetermined period elapses, ensuring stable combustion is established before the integral term of PI control begins operation. This preliminary fuel enrichment prevents the integral value from deviating significantly when F/B control starts, thereby maintaining control precision while enabling early emission control.
Solution Approach 2:
The patent implements dynamics by making the fuel supply amount variable during the transition period. The fuel injection amount is dynamically adjusted based on the elapsed time since cold startup, transitioning from increased fuel supply during the predetermined period to normal F/B controlled fuel supply afterward. This dynamic adjustment allows the system to adapt to changing operational conditions while preventing integral value deviation.
2Stability of the object's composition
If fuel supply amount is increased during cold startup, then combustion stability is improved, but the integral value for PI control deviates leading to delayed return to target air-fuel ratio
Solution Approach 1:
The patent applies preliminary action by pre-increasing the fuel supply amount during cold startup before F/B control is activated. This ensures stable combustion is established in advance, allowing the engine to transition smoothly to F/B control without delaying the return to target air-fuel ratio. The predetermined period for fuel increase is carefully selected to ensure combustion stability while minimizing the time delay.
3Power
If PI control is performed with large deviation during fuel amount increase control, then the integral value becomes excessively large, but this causes poor air-fuel ratio control after fuel increase control ends
Solution Approach 1:
The patent applies preliminary action by increasing fuel supply before F/B control activation, which prevents large deviations in the air-fuel ratio during the transition period. By establishing stable combustion in advance with increased fuel supply, the deviation between actual and target air-fuel ratio remains small when PI control begins, thereby preventing the integral value from becoming excessively large and maintaining detection precision.
Data Source
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AI summary
An air-fuel ratio control system includes an air-fuel ratio sensor (23, 24) disposed upstream or downstream of an exhaust purification catalyst, and performs feedback control of the fuel supply amount such that an output value of the air-fuel ratio sensor is controlled to the target air-fuel ratio. The feedback control is performed by calculating a correction amount by summing up the value of a proportional and the value of an integral calculated based on the deviation between the output value of the air-fuel ratio sensor and the target air-fuel ratio, and correcting the fuel supply amount based on the obtained correction amount. At cold startup of the internal combustion engine, the value of the integral is set to be a smaller value from the startup of the internal combustion engine until a predetermined period elapses.