Dynamic Idle Stop Threshold for Engine Restart Reliability
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Solution Overview
Problem
Existing idle stop control systems for internal combustion engines face challenges in determining the optimal engine speed threshold for restarting, as the deceleration rate changes with braking, leading to restricted combustion start regions when deceleration is normal.
Innovation Solution
The system adjusts the rotational speed threshold for restarting by fuel injection based on the deceleration rate, allowing restart by fuel injection if the engine speed is above a predetermined threshold and using an electric motor if it's below, and prioritizes starter motor use during braking to avoid stalling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotational speed threshold is set high to ensure reliable combustion start during sudden braking, then the reliability of engine restart is improved, but the region where fuel injection-only restart is possible is restricted
Solution Approach 1:
The patent applies dynamics by making the rotational speed threshold adjustable rather than fixed. The control unit dynamically sets different threshold values based on detected deceleration rates: a higher threshold during sudden braking to ensure reliable combustion, and a lower threshold during normal deceleration to expand the fuel injection-only restart region. This dynamic adjustment resolves the contradiction between reliability and adaptability.
Solution Approach 2:
The patent changes the parameter of rotational speed threshold based on the deceleration rate parameter. When the deceleration rate exceeds a threshold (sudden braking), the rotational speed threshold is set to a higher value. When the deceleration rate is within normal range, the rotational speed threshold is set to a lower value. This parameter change strategy allows the system to adapt to different operating conditions, resolving the contradiction between ensuring reliable restart during braking and expanding the fuel injection-only restart region during normal conditions.
2Adaptability or versatility
If the rotational speed threshold is set low to expand the fuel injection-only restart region, then the adaptability of restart methods is improved, but the reliability of combustion start during sudden braking deteriorates
Solution Approach 1:
The system dynamically adjusts the rotational speed threshold based on real-time deceleration detection. During sudden braking (high deceleration rate), the threshold is raised to ensure reliable combustion. During normal deceleration (low deceleration rate), the threshold is lowered to expand the fuel injection-only restart region. This dynamic behavior resolves the contradiction between adaptability and reliability.
Solution Approach 2:
The control unit changes the rotational speed threshold parameter according to the deceleration rate. When deceleration rate > threshold, use high threshold value for reliability. When deceleration rate ≤ threshold, use low threshold value for expanded adaptability. This conditional parameter change resolves the technical contradiction.
3Device complexity
If a fixed rotational speed threshold is used for engine restart, then the device complexity is reduced, but the ability to adapt to different deceleration conditions deteriorates
Solution Approach 1:
The control unit automatically detects the deceleration rate and self-adjusts the rotational speed threshold without requiring external intervention or complex manual configuration. The system serves itself by monitoring its own operating conditions (deceleration rate) and autonomously selecting appropriate threshold values, thereby maintaining simplicity while achieving adaptability.
Solution Approach 2:
The system uses feedback from the deceleration rate detection to adjust the rotational speed threshold. The control unit continuously monitors the deceleration rate and uses this feedback information to dynamically set the appropriate threshold value, enabling the system to adapt to different conditions while maintaining a relatively simple control structure.
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 expands the region where the engine can be restarted by fuel injection alone, ensuring reliable restarts without stalling, even during normal braking conditions.
Implementation Method 1
the internal combustion engine is caused to rotate and started using an electric motor
Implementation Method 2
the internal combustion engine is started by resuming fuel injection if the engine speed is equal to or greater than a predetermined rotational speed threshold
Implementation Method 3
the internal combustion engine is started by resuming fuel injection
Data Source
AI summary
In an internal combustion engine, fuel injection is stopped to automatically stop the engine when automatic stop conditions are met. When there is a request to restart the engine while an engine speed is decreasing due to automatic stoppage, the engine is started by resuming fuel injection if the engine speed is equal to or greater than a combustion recoverable rotational speed threshold, at which restarting is possible only by fuel injection. When there is a request to restart the engine while an engine speed is decreasing due to automatic stoppage, the engine is started using a starter motor if the engine speed is less than the combustion recoverable rotational speed threshold. When there is a request to restart the engine in a brake ON state, the engine is not started by resuming fuel injection, but rotated and started using the starter motor.