Variable Compression Ratio Engine Control for Knock Prevention
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Solution Overview
Problem
In spark ignition type internal combustion engines, the synchronization of mechanical compression ratio and intake valve closing timing with changing intake air demand is challenging, leading to issues such as knocking, poor combustion, and inadequate acceleration response due to differences in the speed of change between these parameters.
Innovation Solution
A spark ignition type internal combustion engine with a variable compression ratio mechanism and a variable valve timing mechanism that sets a no-entry region for combinations of mechanical compression ratio and intake valve closing timing, calculating a target operating point that avoids this region to ensure rapid and coordinated changes in mechanical compression ratio and intake valve timing in response to changing intake air demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the closing timing of the intake valve is advanced rapidly to increase intake air amount, then the response to acceleration demand is improved, but the compression end pressure becomes excessively high causing knocking
Solution Approach 1:
The patent applies dynamics by making the mechanical compression ratio variable rather than fixed. The variable compression ratio mechanism allows the compression ratio to be dynamically adjusted in coordination with intake valve timing changes, enabling the system to accommodate rapid intake air amount changes without excessive compression end pressure that causes knocking.
Solution Approach 2:
The patent changes the parameter of mechanical compression ratio from a static value to a dynamically adjustable parameter. By changing the compression ratio parameter in response to intake air demand and valve timing, the system can prevent knocking while maintaining good combustion across different operating conditions.
2Use of energy by moving object
If the mechanical compression ratio is maintained high to ensure good combustion, then combustion efficiency is improved, but the compression end pressure becomes excessively high when intake air amount increases causing knocking
Solution Approach 1:
The variable compression ratio mechanism enables the mechanical compression ratio to be dynamically adjusted based on operating conditions. When intake air amount increases, the compression ratio can be reduced to prevent knocking, while under other conditions it can be maintained high for good combustion efficiency.
Solution Approach 2:
The patent changes the compression ratio parameter from a fixed high value to a variable parameter that can be adjusted according to intake air demand and valve timing, allowing optimization of both combustion efficiency and knocking prevention.
3Object-affected harmful factors
If the closing timing of the intake valve is retarded slowly to maintain low compression end pressure, then knocking is prevented, but the intake air amount increases slowly reducing acceleration response
Solution Approach 1:
The variable compression ratio mechanism provides an additional dynamic control parameter to manage compression end pressure. This allows the intake valve timing to advance more rapidly for better response, while the compression ratio is simultaneously adjusted to prevent excessive compression end pressure and knocking.
4Speed
If the mechanical compression ratio is changed rapidly to match intake air demand, then the response to load changes is improved, but the mechanical system requires more time to change compared to valve timing
Solution Approach 1:
The control system uses feedback from intake air amount sensors and operating conditions to continuously adjust both valve timing and compression ratio. This coordinated feedback control ensures that changes in compression ratio are synchronized with valve timing changes, optimizing the overall response to load changes despite the mechanical system's inherent time requirements.
Data Source
AI summary
An internal combustion engine which is provided with a variable compression ratio mechanism which can change a mechanical compression ratio and a variable valve timing mechanism which can control a closing timing of an intake valve. A target operating point which can be reached after a fixed time without entering no-entry regions from the current operating point toward an operating point which satisfies the demanded intake air amount is calculated for an operating point which shows a combination of the mechanical compression ratio and the closing timing of the intake valve when the demanded intake air amount changes, and the mechanical compression ratio and the closing timing of the intake valve are made to change toward this target operating point.