Variable Compression Ratio Control for Sailing Stop Engine Restart
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Solution Overview
Problem
Existing control methods for internal combustion engines with variable compression ratio mechanisms fail to appropriately manage compression ratios during sailing stop and idle stop, leading to inadequate engine restart performance, particularly in terms of torque control and responsiveness.
Innovation Solution
The method sets distinct target compression ratios for sailing stop and idle stop restarts, adjusting the compression ratio of the variable compression ratio mechanism to optimize engine restarts, ensuring appropriate torque control and responsiveness based on the specific conditions of each stop type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single target compression ratio is set for all engine stop conditions, then the control system is simple, but the engine restart performance is inadequate for different stop types
Solution Approach 1:
The patent segments the engine stop conditions into distinct categories (sailing stop and idle stop) and assigns different target compression ratios to each category. The control device determines the stop type and selects appropriate compression ratio settings, enabling optimized restart performance for each condition while maintaining manageable control complexity through clear classification.
Solution Approach 2:
The patent implements dynamic adjustment of the target compression ratio based on the detected stop type. The control device varies the compression ratio setting in real-time according to whether the engine stopped due to sailing stop or idle stop conditions, allowing the system to adapt optimally to different operational contexts rather than using a fixed compression ratio.
2Use of energy by moving object
If the compression ratio is increased to improve thermal efficiency, then thermal efficiency improves, but knockings occur in high engine load region
Solution Approach 1:
The patent changes the compression ratio parameter dynamically based on engine operating conditions. By adjusting the compression ratio according to engine load and stop type, the system achieves high thermal efficiency during coasting travel (sailing stop) while preventing knockings during high load conditions through appropriate compression ratio reduction.
Solution Approach 2:
The variable compression ratio mechanism enables dynamic adjustment of the compression ratio in response to changing engine conditions. The control device monitors engine load and stop type, then varies the compression ratio in real-time to optimize thermal efficiency when conditions permit while avoiding knockings when load increases.
3Speed
If the engine restarts with high torque immediately after sailing stop, then acceleration responsiveness improves, but torque control becomes difficult
Solution Approach 1:
The patent applies preliminary action by setting the target compression ratio before engine restart occurs. The control device determines the appropriate compression ratio based on the detected sailing stop condition and configures it in advance, ensuring optimal torque control and acceleration responsiveness from the moment of restart without causing sudden torque shocks.
Data Source
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AI summary
An internal combustion engine (1) for a vehicle is equipped with a variable compression ratio mechanism (2) capable of changing the mechanical compression ratio. An idle stop, which is for automatically stopping the internal combustion engine (1) when the vehicle stops, and a sailing stop, which is for stopping the internal combustion engine (1) in conjunction with the release of a forward clutch (8) during inertial travel, are carried out. A target compression ratio during normal travel is set on the basis of the load and rotation speed of the internal combustion engine (1). During an idle stop the target compression ratio is set to an idle stop restart compression ratio (εis). During a sailing stop the target compression ratio is set to a sailing stop restart compression ratio (εss). The sailing stop restart compression ratio (εss) is lower than the idle stop restart compression ratio (εis).