Spark Ignition Engine Variable Compression Ratio Control
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Solution Overview
Problem
In spark ignition-type internal combustion engines, the mechanical compression ratio control in low engine load areas leads to poor heat efficiency and drivability issues due to frequent changes in boost pressure, causing engine load to fluctuate around the set engine load, which deteriorates performance.
Innovation Solution
Implementing a dual mechanical compression ratio control system where the first control increases expansion ratio in low engine load areas and the second control lowers it, combined with a boost pressure control that adjusts the set engine load threshold to maintain stable engine output and reduce drivability deterioration by using superchargers, waste gate valves, or variable nozzle turbochargers to increase boost pressure in a step change manner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the mechanical compression ratio is increased in the low engine load side operation area to increase the expansion ratio and improve heat efficiency, then the heat efficiency is improved, but the engine operation area to realize low fuel consumption shifts to low engine speed and high engine load side, causing frequent boost pressure changes and deteriorating drivability
Solution Approach 1:
The patent applies dynamics by implementing a variable compression ratio mechanism that dynamically adjusts the mechanical compression ratio based on engine operating conditions. The control unit switches between first and second mechanical compression ratio control modes depending on engine load and speed, allowing the system to adapt the compression ratio to match actual operating requirements rather than using a fixed ratio
Solution Approach 2:
The patent changes the parameter of mechanical compression ratio by implementing two different control strategies: first mechanical compression ratio control that increases compression ratio in low load areas to improve heat efficiency, and second mechanical compression ratio control that maintains lower compression ratio to stabilize engine operation. The control unit selectively applies these parameter changes based on operating conditions to balance efficiency and drivability
2Stability of the object's composition
If the set engine load for boost pressure control is maintained at the same level when second mechanical compression ratio control is carried out, then the boost pressure control threshold is consistent, but the engine load frequently becomes higher or lower than the set engine load causing repeated boost pressure changes and deteriorating drivability
Solution Approach 1:
The patent changes the parameter of set engine load threshold dynamically. When second mechanical compression ratio control is active, the control unit sets a higher set engine load threshold for boost pressure control compared to when first mechanical compression ratio control is active. This parameter adjustment prevents frequent trigger of boost pressure control, stabilizing engine operation and improving drivability
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 stabilizes engine load and improves drivability by maintaining engine output while reducing the frequency of boost pressure fluctuations, enhancing thermal efficiency and fuel consumption in low engine load conditions.
Implementation Method 1
the electromagnetic clutch connects the engine drive shaft and the supercharger to make the supercharger in a non-operating state operate and thus the boost pressure is increased like a step change
Implementation Method 2
the boost pressure control makes an opening degree of a waste gate valve small to increase the boost pressure like a step change by a turbocharger
Implementation Method 3
the boost pressure control makes an angle of variable nozzles of a variable nozzle-type turbocharger change to increase the boost pressure like a step change by the variable nozzle-type turbocharger
Data Source
AI summary
A spark ignition-type internal combustion is provided wherein a first mechanical compression ratio control and a second mechanical compression ratio control are alternatively carried out, the first mechanical compression ratio control makes the mechanical compression ratio in the low engine load side operation area higher than that in the high engine load side operation area to increase the expansion ratio in the low engine load side operation area, the second mechanical ratio control makes the expansion ratio in the low engine load side operation area lower than that in the low engine load side operation area made by the first mechanical compression ratio control and a boost pressure control increases the boost pressure like a step change when the engine load becomes a set engine load in the low engine load side operation area or higher.