Hybrid Vehicle Catalyst Protection via Lean Exhaust Detection
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Solution Overview
Problem
In hybrid vehicles, a persistent lean exhaust air-fuel ratio due to low fuel levels can lead to erroneous sensor judgments, damage to the exhaust purification catalyst, and deterioration of drivability, as existing solutions struggle to accurately detect the cause of leanness and timing for protective control.
Innovation Solution
A control device with an exhaust air-fuel ratio detection unit, a protective control unit that inhibits engine operation and drives the traction motor if the lean state persists, and additional units for complete explosion detection and oil supply detection to accurately determine the cause of leanness and execute catalyst protective control at suitable times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine is stopped to protect the exhaust purification catalyst from damage due to persistent lean exhaust air-fuel ratio, then the catalyst is protected from damage, but the drivability deteriorates because the vehicle cannot be propelled by the engine
Solution Approach 1:
The control device dynamically adjusts the protective control duration based on the detected cause of leanness. When fuel supply issues are detected, the engine stop duration is extended up to a predetermined maximum to ensure catalyst protection. When other causes are identified, the protective control duration is reduced or eliminated, allowing the engine to resume normal operation and maintain drivability.
Solution Approach 2:
The system changes the operational parameters of the engine based on the detected cause of lean exhaust air-fuel ratio. By identifying whether the leanness is caused by fuel supply issues or other factors, the control device adjusts the engine stop duration parameter accordingly, balancing catalyst protection with drivability requirements.
2Reliability
If the protective control duration is extended to ensure catalyst protection, then the catalyst is protected from damage, but the drivability deteriorates due to prolonged engine stoppage
Solution Approach 1:
The control device dynamically adjusts the protective control duration based on the detected cause of leanness. When fuel supply issues are detected, the engine stop duration is extended up to a predetermined maximum to ensure catalyst protection. When other causes are identified, the protective control duration is reduced or eliminated, allowing the engine to resume normal operation and maintain drivability.
3Reliability
If the engine operation is inhibited to prevent catalyst damage, then the catalyst is protected, but the exhaust air-fuel ratio detection becomes less reliable for determining the true cause of leanness
Solution Approach 1:
The control device performs preliminary detection and judgment of the cause of lean exhaust air-fuel ratio before executing protective control. By analyzing the exhaust air-fuel ratio trend and identifying the root cause (fuel supply issue vs. other factors) in advance, the system determines the appropriate protective control duration, ensuring both catalyst protection and accurate cause determination.
Data Source
AI summary
A control device for a hybrid vehicle, which can inhibit damage to an exhaust purification catalyst and also suppress deterioration of drivability, is provided. The control device exercises catalyst protective control, which inhibits operation of an engine and drives a traction motor, if a state where an exhaust air-fuel ratio detected by an exhaust air-fuel ratio detection unit is lean continues for a first predetermined time or longer.