Engine Air-Fuel Ratio Control for Stall Prevention
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Solution Overview
Problem
In vehicles equipped with a torque converter and a lock-up clutch, there is a risk of engine stall during deceleration due to the disparity in rotational speeds between the engine and transmission sides, and lean-burn control near idle speed complicates accurate engine output control, potentially leading to stalls or surges.
Innovation Solution
An engine air-fuel ratio control device that executes fuel injection feedback control to maintain a lean air-fuel ratio after releasing the lock-up state during deceleration, predicts engine stalls based on deceleration indicators, and cancels lean-burn control when a stall is predicted to prevent engine stalling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lean-burn control is executed during deceleration to reduce fuel consumption, then fuel efficiency is improved, but engine stability deteriorates and risk of stall increases
Solution Approach 1:
The engine stall predictor performs preliminary assessment of stall risk using deceleration indicators before the actual deceleration event fully develops. By predicting potential stall conditions in advance, the system can proactively adjust air-fuel ratio control strategies, transitioning from lean-burn to stoichiometric control before the stall occurs, thus preventing the harmful effect while maintaining fuel efficiency during safe deceleration periods
Solution Approach 2:
The control system continuously monitors deceleration indicators and engine operating parameters, using this feedback to dynamically adjust the air-fuel ratio. When the predictor detects stall risk through feedback from deceleration measurements, the system responds by modifying fuel injection quantities to maintain stable engine operation, creating a closed-loop control that balances fuel efficiency and reliability
2Reliability
If lock-up clutch is released during deceleration to prevent engine stall, then engine stability is improved, but power transmission efficiency deteriorates
Solution Approach 1:
The system dynamically changes the air-fuel ratio parameter based on predicted deceleration conditions. By adjusting the air-fuel ratio from lean to stoichiometric in advance of severe deceleration events, the system modifies combustion characteristics to provide more stable engine operation during clutch release, enabling the clutch to remain engaged longer while maintaining reliability
Solution Approach 2:
The engine controller performs preliminary adjustment of fuel injection quantities based on predicted deceleration magnitude. This advance preparation allows the engine to maintain stable operation when the lock-up clutch is released, reducing the frequency and duration of clutch releases needed for stall prevention, thereby maintaining higher power transmission efficiency
Data Source
AI summary
An engine air-fuel ratio control device is configured to be used in a vehicle including a power transmission device configured to transmit power between an output shaft of an engine and an input shaft of a transmission and to execute a lean-burn control that puts an air-fuel ratio of the engine into a lean state. An engine controller executes a fuel injection feedback control such that the air-fuel ratio becomes a lean target value after the power transmission device is released during a deceleration of the vehicle. An engine stall predictor predicts a stall of the engine on a basis of a deceleration indicator that is correlated with a deceleration degree of the vehicle in a state in which the power transmission device is released. A lean-burn control canceler cancels the lean-burn control in a case in which the engine is predicted to stall.