Variable Compression Ratio Engine Exhaust-Based Estimation
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Solution Overview
Problem
Existing internal combustion engines with variable compression ratio mechanisms struggle to estimate the current actual mechanical compression ratio when a fuel cut operation is not performed, affecting the realization of target mechanical compression ratios and expansion ratios.
Innovation Solution
The engine measures exhaust temperature or pressure, which changes with the actual expansion ratio, and uses these measurements to estimate the current mechanical compression ratio, employing a detection device to correct the actuating amount of the variable compression ratio mechanism based on the estimated ratio, even in specific engine operating states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the current actual compression ratio is estimated using cylinder pressure at top dead center during fuel cut operation, then the estimation can be performed, but it is not possible to estimate the current actual compression ratio when fuel cut operation is not performed
Solution Approach 1:
The patent uses exhaust temperature or pressure as an intermediary parameter to estimate the mechanical compression ratio. Instead of directly measuring compression ratio (which requires fuel cut operation), the system measures exhaust temperature/pressure that changes in accordance with the actual expansion ratio, and uses this as a mediator to infer the compression ratio. This allows estimation without requiring fuel cut operation, thus resolving the contradiction between measurement precision and adaptability.
Solution Approach 2:
The patent replaces the mechanical measurement method (cylinder pressure measurement during fuel cut) with a thermal field measurement method (exhaust temperature or pressure measurement). By substituting the measurement domain from mechanical to thermal, the system can continuously estimate compression ratio without requiring specific operating conditions like fuel cut, thereby improving both measurement precision and adaptability across different operating states.
2Loss of energy
If the variable compression ratio mechanism is controlled to achieve target mechanical compression ratios, then the expansion ratio can be increased to raise thermal efficiency, but the target mechanical compression ratio is sometimes not realized in actuality
Solution Approach 1:
The patent implements a feedback control mechanism where the estimated mechanical compression ratio is continuously compared with the target mechanical compression ratio. The actuator of the variable compression ratio mechanism is controlled based on this comparison to minimize the difference between actual and target compression ratios. This feedback loop ensures reliable realization of target compression ratios while maintaining improved thermal efficiency, resolving the contradiction between energy loss reduction and reliability.
3Reliability
If the actuating amount of the variable compression ratio mechanism is corrected based on the difference between estimated and target mechanical compression ratios, then the target mechanical compression ratio can be reliably realized, but additional detection and correction mechanisms are required
Solution Approach 1:
The patent makes the exhaust temperature/pressure measurement serve multiple functions: it is used for both engine operation monitoring and mechanical compression ratio estimation. By giving this measurement universal application, the system achieves reliable target compression ratio realization without adding dedicated complex detection equipment, thus resolving the contradiction between reliability improvement and device complexity.
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 allows for accurate estimation and realization of the current mechanical compression ratio, even without a fuel cut operation, ensuring target mechanical compression ratios are achieved, enhancing thermal efficiency and preventing knocking.
Implementation Method 1
measures an exhaust temperature or an exhaust pressure which changes in accordance with an actual expansion ratio
Implementation Method 2
a supercharging pressure at a downstream side of a compressor of a turbocharger
Data Source
Figure 1
Figure 2
Figure 3(A)~3(C)
AI summary
This internal combustion engine comprising a variable compression ratio mechanism either measures an exhaust temperature or exhaust pressure which varies according to an actual expansion ratio, or measures a physical quantity which varies according to the exhaust temperature and/or the exhaust pressure (step 102), and estimates the current mechanical compression ratio on the basis of the measured value (steps 103 to 105).