Spark Ignition Engine Variable Compression Ratio Control
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Solution Overview
Problem
In spark ignition type internal combustion engines, advancing the intake valve closing timing to increase intake air at medium and high load operations leads to a decrease in mechanical compression ratio, resulting in reduced heat efficiency and increased fuel consumption due to a corresponding drop in expansion ratio.
Innovation Solution
The implementation of a control system that utilizes a supercharger to increase intake air pressure at medium load operations, allowing for a smaller decrease in mechanical compression ratio and thus maintaining heat efficiency, while also employing variable valve timing and throttle control to manage intake air and prevent knocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the closing timing of the intake valve is advanced to increase the amount of intake air at medium and high load operations, then the amount of intake air fed into the combustion chamber increases, but the mechanical compression ratio decreases, resulting in reduced heat efficiency and increased fuel consumption
Solution Approach 1:
The invention changes the mechanical compression ratio parameter dynamically based on engine load conditions. At medium and high load operations, the mechanical compression ratio is deliberately reduced to prevent knocking while maintaining adequate intake air through advanced valve closing timing. This parameter change allows the engine to operate efficiently across different load ranges without sacrificing heat efficiency for increased air intake.
2Object-affected harmful factors
If the mechanical compression ratio is lowered to prevent knocking at medium and high load operations, then knocking is suppressed, but the expansion ratio decreases, resulting in reduced heat efficiency
Solution Approach 1:
The invention implements dynamic adjustment of the mechanical compression ratio based on real-time engine load conditions. The control system continuously monitors engine operating parameters and adjusts the compression ratio accordingly - maintaining higher compression at low load for efficiency, and reducing compression at medium and high load to prevent knocking. This dynamic approach allows the engine to optimize between knocking prevention and heat efficiency across the entire operating range.
3Quantity of substance
If the closing timing of the intake valve is advanced to increase intake air at medium load operation, then the amount of intake air increases, but the expansion ratio drops, causing deterioration of fuel consumption
Solution Approach 1:
The invention dynamically changes the mechanical compression ratio parameter in response to engine load conditions. At medium load operations, the system reduces the mechanical compression ratio to prevent knocking while maintaining advanced valve closing timing for adequate air intake. This parameter adjustment ensures that fuel consumption does not deteriorate despite the increased air intake, as the lower compression ratio prevents the expansion ratio from dropping too significantly.
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 effectively suppresses the drop in heat efficiency and fuel consumption by maintaining a higher expansion ratio and preventing knocking, even at increased engine loads, by using the supercharger to raise intake air pressure and adjusting valve timing and throttle settings accordingly.
Implementation Method 1
the supercharging action of the supercharger is used to raise a pressure inside an intake pipe
Data Source
AI summary
A spark ignition type internal combustion engine of the present invention is provided with a variable compression ratio mechanism able to change a mechanical compression ratio, a variable valve timing mechanism able to control a closing timing of an intake valve, and a supercharger. At the time of engine low load operation, the mechanical compression ratio is made higher compared with at the time of engine high load operation. At the time of engine medium load operation, the supercharging action of the supercharger is used to make the pressure inside the intake pipe rise so that the intake air amount fed into a combustion chamber is increased, compared with at the time of engine low load operation, and the mechanical compression ratio is lowered to make the actual compression ratio fall.