Engine Stability Index for Adaptive Valve Overlap Control
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Solution Overview
Problem
Spark-ignition combustion engines experience overconsumption of fuel due to pumping losses at partial load, and existing calibration methods for valve overlap are imprecise, degrading engine stability and fuel efficiency, especially during transient operating phases.
Innovation Solution
A method for regulating engine stability by calculating a stability index based on the difference between measured and estimated time derivatives of engine speed, allowing for adaptive control of valve overlap, ignition advance, and fuel richness to optimize fuel consumption while maintaining stability, with a backup strategy to ensure engine reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If valve overlap is increased to reduce pumping losses and fuel consumption, then fuel efficiency improves, but engine stability deteriorates
Solution Approach 1:
The patent applies dynamics by making the valve overlap angle variable rather than fixed. The camshaft phase shifter dynamically adjusts the overlap angle based on real-time engine operating conditions (load, speed, temperature) to optimize the balance between fuel efficiency and stability. This allows the system to increase overlap when fuel savings are critical while maintaining stability when needed.
Solution Approach 2:
The patent changes the parameter of valve overlap angle from a fixed calibration value to a dynamically adjustable parameter. By continuously modifying the overlap angle based on measured engine parameters and stability assessment, the system adapts to different operating conditions, resolving the contradiction between fuel efficiency (benefiting from higher overlap) and stability (requiring controlled overlap).
2Device complexity
If fixed calibration maps are used for valve overlap settings, then device complexity is reduced, but measurement precision and optimization accuracy deteriorate
Solution Approach 1:
The patent implements feedback by continuously measuring engine parameters (speed, load, temperature), calculating a stability index, and using this information to adjust valve overlap settings in real-time. This closed-loop control system replaces fixed calibration maps with adaptive control, improving precision without requiring excessive system complexity.
Solution Approach 2:
The patent substitutes mechanical/fixed calibration approaches with electronic control and computational algorithms. Instead of relying on pre-set mechanical cam profiles, the system uses electronic camshaft phase shifters controlled by a microprocessor that calculates optimal settings based on real-time engine state, achieving higher precision while managing complexity through software-based solutions.
Data Source
Figure 1~3
AI summary
The invention relates to a method for adjusting an operating parameter of an internal combustion engine (2), including the following steps: creating a stability set value (Cs), calculating an engine stability index (Is), calculating the stability deviation (Es) which is equal to the difference between the stability setting (Cs) and the stability index (Is), and processing of the stability deviation (Es) by a controller (6) that provides an engine control set value (OA, FE) to be applied to the operating parameter of the engine (2). The invention is characterised in that the stability index (Is) is a function of the difference between the measured time derivative of the engine speed at the time of calculation, and the estimated time derivative of the engine speed according to the engine torque and the inertias that inhibit the fluctuation of the rotation speed of the engine.