Variable Valve Timing for Engine Start Control
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Solution Overview
Problem
Existing start control devices for internal combustion engines face challenges in starting performance, especially with alcohol mixed fuels, due to varying fuel mixture ratios and the need for additional sensors, which increases cost and unreliability.
Innovation Solution
A start control device that includes a variable valve mechanism to advance the intake valve closing timing during cranking, controlled by a unit that sets a threshold value for timing advancement based on detected fuel properties, eliminating the need for a concentration sensor and improving starting reliability with fuels hard to ignite.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the valve closing timing of the intake valve is advanced to increase the actual compression ratio for improving starting performance with alcohol mixed fuel, then the internal cylinder temperature rises and fuel ignition is facilitated, but the cranking load increases and starting reliability becomes unreliable due to unknown fuel mixture ratio
Solution Approach 1:
The valve closing timing is made dynamically adjustable during cranking operation. The ECU controls the variable valve mechanism to advance the valve closing timing progressively during cranking, allowing the system to adapt to different fuel types and conditions in real-time, thereby improving starting reliability without excessive cranking load
Solution Approach 2:
The system changes the valve closing timing parameter during cranking operation based on detected engine conditions. By dynamically adjusting this timing parameter, the system optimizes the balance between compression ratio (for ignition) and cranking load, resolving the contradiction between starting reliability and cranking force requirements
2Reliability
If a concentration sensor is provided to detect alcohol concentration in the fuel tank for determining valve closing timing, then the starting performance can be optimized for different fuel mixture ratios, but the device complexity increases and cost burden rises
Solution Approach 1:
The system uses existing engine sensors (crank angle sensor, coolant temperature sensor, etc.) to detect operating conditions and infer fuel type information. The ECU processes this existing data to determine appropriate valve timing without requiring additional concentration sensors, thereby maintaining starting performance while reducing device complexity
Solution Approach 2:
The variable valve mechanism serves multiple functions: it optimizes starting performance for different fuel types, reduces cranking load, and adapts to varying engine conditions. By making this single component multi-functional, the system eliminates the need for separate sensor systems while maintaining reliable starting across different fuel mixture ratios
3Force
If the valve closing timing is set separated toward the top dead center from the bottom dead center to reduce starting load, then the effective compression ratio is lowered and starting load is reduced, but the internal cylinder temperature decreases and fuel ignition becomes difficult
Solution Approach 1:
The valve closing timing is dynamically adjusted during cranking based on engine conditions and detected fuel type. The system can shift timing toward bottom dead center for easier starting with normal fuels, then progressively advance timing during cranking to increase temperature for difficult-to-ignite fuels, optimizing both load and temperature requirements at different stages
Solution Approach 2:
The system applies periodic adjustments to valve closing timing during the cranking process. It starts with timing that reduces cranking load, then periodically advances the timing as cranking progresses to build internal temperature, creating a staged approach that balances load reduction with ignition facilitation
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
The solution enhances starting performance by gradually advancing the intake valve closing timing, increasing the actual compression ratio and internal cylinder temperature, allowing for reliable engine starting with mixed fuels without additional sensors, reducing cranking load, and lowering costs.
Implementation Method 1
the actual compression ratio of the cylinder increases, and the internal cylinder temperature rises, so that the fuel easily ignites
Data Source
AI summary
A start control device of an internal combustion engine, the start control device includes: a starting unit, which cranks the internal combustion engine to start the internal combustion engine while opening and closing an intake valve; a variable valve mechanism, which can change a closing timing of the intake valve; and a control unit, which controls the variable valve mechanism so as to advance the closing timing of the intake valve while the starting unit cranks.