Variable Compression Ratio Engine Cylinder Calibration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Variable Compression Ratio (VCR) engines face challenges due to manufacturing tolerances leading to cylinder-to-cylinder variations in compression ratio, resulting in unstable combustion, noise, vibration, and reduced efficiency, which existing calibration methods based on prototype engines cannot optimally address without increasing costs.
Innovation Solution
Calibrate the compression ratio schedule of each cylinder based on fuel flow and peak torque at each setting, and adjust the Exhaust Gas Recirculation (EGR) and Variable Cam Timing (VCT) schedules dynamically to account for actual cylinder variations, using mapping data to optimize engine performance and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If prototype engine calibration is used for VCR engines, then calibration process is simplified, but cylinder-to-cylinder variation in compression ratio causes unstable combustion and reduced efficiency
Solution Approach 1:
The patent applies local quality by transitioning from a global prototype-based calibration approach to individual cylinder-specific calibration. Each cylinder's compression ratio is measured and calibrated separately based on its actual performance characteristics, allowing tailored optimization for each cylinder rather than applying a uniform calibration across all cylinders. This resolves the contradiction by maintaining simplicity through automated measurement while achieving reliability through cylinder-specific adjustments.
2Ease of manufacture
If manufacturing tolerances are relaxed to reduce costs, then ease of manufacture improves, but cylinder-to-cylinder variation in compression ratio increases leading to NVH and misfire issues
Solution Approach 1:
The patent applies self-service by implementing automated measurement and calibration systems that allow each engine to self-adjust its compression ratio settings after assembly. The system automatically measures actual compression ratios in each cylinder and adjusts VCR mechanisms accordingly, eliminating the need for expensive pre-selection or manual adjustment during manufacturing. This resolves the contradiction by maintaining relaxed manufacturing tolerances while achieving precise compression ratio control through post-assembly automation.
3Manufacturing precision
If VCR mechanism components are selected with tighter tolerances to control CR differences, then compression ratio uniformity improves, but manufacturing cost increases significantly
Solution Approach 1:
The patent applies preliminary action by performing compression ratio measurement and calibration as a standard post-assembly step for every engine before delivery. Rather than relying on expensive pre-selection of components during manufacturing, the system proactively measures and adjusts each cylinder's compression ratio after assembly, ensuring uniformity is achieved through calibration rather than component selection. This resolves the contradiction by maintaining cost-effective manufacturing while achieving precise compression ratio uniformity through automated post-assembly calibration.
Data Source
AI summary
Methods and systems are provided for improving calibration of a variable compression ratio engine. Cylinder-to-cylinder compression ratio variations are detected and accounted for by comparing cylinder fuel flow and IMEP at each compression ratio setting. Dilution parameters including EGR and VCT schedule are also calibrated to account for the cylinder-to-cylinder compression ratio variations.