Air-Fuel Ratio Imbalance Detection in Hybrid Engines
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Solution Overview
Problem
Existing air-fuel ratio imbalance detecting devices for internal combustion engines struggle to accurately detect imbalances, especially when intake air amounts are low, leading to reduced detection accuracy or false positives due to decreased output from air-fuel ratio sensors.
Innovation Solution
The system includes a rich imbalance detecting unit that adjusts intake air amounts and power consumption by the rotating electrical machine to increase exhaust gas emission, enhancing detection accuracy by increasing the difference between balanced and imbalanced air-fuel ratio sensor outputs, and incorporates a control unit to suppress drivability influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the intake air amount is kept small, then the power consumption of the rotating electrical machine is reduced, but the detection accuracy of air-fuel ratio imbalance deteriorates
Solution Approach 1:
The system dynamically adjusts the operating condition of the internal combustion engine by changing the intake air amount from a first detection region to a second detection region based on the detected air-fuel ratio variation. This dynamic adjustment allows the system to optimize between power consumption and detection accuracy by temporarily increasing air intake only when detection is needed.
Solution Approach 2:
The system changes the operating parameter (intake air amount) of the internal combustion engine to improve detection accuracy. By adjusting the intake air amount from a smaller first detection region to a larger second detection region, the system increases the output signal from the air-fuel ratio sensor, thereby improving the difference between balanced and imbalanced states without permanently increasing power consumption.
2Measurement precision
If the intake air amount is increased to improve detection accuracy, then the detection accuracy of air-fuel ratio imbalance is improved, but the power consumption increases and drivability is influenced
Solution Approach 1:
The system performs periodic detection cycles where the intake air amount is temporarily increased only when air-fuel ratio detection is required, then returned to the normal operating condition. This periodic adjustment allows accurate detection without continuously affecting drivability or increasing power consumption.
Solution Approach 2:
The control unit dynamically adjusts the intake air amount based on detection needs, temporarily transitioning to a second detection region when detection is required and returning to the first detection region when detection is complete. This dynamic control minimizes the impact on drivability while ensuring accurate detection when needed.
3Loss of energy
If the intake air amount is small, then the power consumption is reduced, but the difference between sensor output values becomes small making detection difficult
Solution Approach 1:
The system changes the operating parameter (intake air amount) to a second detection region that is higher than the first detection region when detection is needed. This parameter change increases the absolute output value from the air-fuel ratio sensor and amplifies the difference between balanced and imbalanced air-fuel ratio states, making detection possible without permanently increasing power consumption.
Data Source
AI summary
When a detected value for detecting a rich imbalance in air-fuel ratio among cylinders, in a state where an intake air amount of an engine falls within a low amount region, is lower than a first threshold corresponding to the intake air amount and is higher than or equal to a second threshold corresponding to the intake air amount, a hybrid electronic control unit controls the engine such that the intake air amount falls within a high amount region, and controls a motor generator such that electric power corresponding to a power increase amount is consumed. When the intake air amount falls within the high amount region, the hybrid electronic control unit detects a rich imbalance in air-fuel ratio among the cylinders by comparing the detected value with a third threshold corresponding to the intake air amount.