Manual Transmission Stop-Start Engine Control Thresholds
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Solution Overview
Problem
Current Stop-in-Gear Stop-Start systems for manual transmission vehicles fail to maximize fuel economy due to conservative clutch pedal position thresholds, leading to missed engine restart opportunities and driver dissatisfaction.
Innovation Solution
A method is introduced that sets two clutch disengagement threshold limits: a more conservative first threshold for disengagement to stop the engine and a less conservative second threshold for engagement to restart, allowing for more flexible clutch pedal movement without preventing engine restarts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conservative clutch pedal position threshold is used to prevent vehicle movement during engine cranking, then vehicle stability is improved, but the number of missed engine restart opportunities increases
Solution Approach 1:
The single clutch pedal position threshold is segmented into two distinct thresholds: a first threshold for engine stop decisions and a second threshold for engine restart decisions. This segmentation allows each threshold to be optimized for its specific function, resolving the contradiction between vehicle stability and restart frequency.
Solution Approach 2:
The system dynamically selects which threshold to apply based on the current operational context (engine stop vs. engine restart). This dynamic adaptation allows the system to use a more conservative threshold when stopping to ensure stability, while using a less conservative threshold when restarting to maximize restart opportunities.
2Object-affected harmful factors
If a single conservative clutch threshold is used for both engine stop and restart decisions, then vehicle safety is improved, but fuel economy is worsened due to missed restart opportunities
Solution Approach 1:
The decision-making process is segmented into two phases with different threshold requirements. The first threshold ensures safety during engine stop, while the second threshold optimizes fuel economy during restart by being less conservative, thus reducing missed restart opportunities.
Solution Approach 2:
The clutch pedal position threshold parameter is changed based on the operational phase. A more conservative parameter value is used for engine stop decisions to ensure safety, while a less conservative parameter value is used for engine restart decisions to improve fuel economy.
3Productivity
If the clutch pedal threshold is set to allow engine restarts, then engine restart frequency is improved, but the risk of vehicle movement during cranking increases
Solution Approach 1:
The system segments the threshold requirement into two distinct values: a less conservative second threshold that allows more restart opportunities, and a more conservative first threshold that ensures vehicle stability. Each threshold is applied in its appropriate context.
Solution Approach 2:
The system dynamically adjusts the effective threshold based on whether the engine is stopping or restarting. During restart operations, the less conservative second threshold is applied to maximize restart frequency while maintaining adequate safety through contextual awareness.
4Ease of operation
If the engine stop threshold is made less conservative to allow pedal creep, then ease of operation is improved, but the reliability of engine restart permission is worsened
Solution Approach 1:
The system segments the threshold into a first threshold for stop decisions that can be less conservative (allowing pedal creep), and a second threshold for restart decisions that ensures reliability. This segmentation resolves the contradiction by applying appropriate conservatism to each decision type.
Solution Approach 2:
The system dynamically selects which threshold to apply based on the current operation. The first threshold allows greater operational freedom during engine stop, while the second threshold ensures reliable restart permission, with the system switching between them based on operational context.
Data Source
AI summary
A method of stopping and starting an engine of a vehicle having a manually operated clutch system including a clutch for driveably connecting the engine to a transmission includes controlling stopping and starting of the engine based on first and second clutch engagement thresholds selected based on whether the clutch is being engaged or disengaged. The first threshold corresponds to a more disengaged state of the clutch than the second threshold. The first threshold is used when the clutch is being disengaged to decide whether the engine can be shut down while the transmission remains in-gear. The second threshold is used when the clutch is being engaged to decide whether the engine can be started while the transmission remains in-gear. By using a less conservative threshold for starting the engine than stopping the engine, the number of inhibited restarts is reduced.