Crankshaft Angle Detection via Cylinder Pressure Harmonics
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Solution Overview
Problem
Existing engine control systems face challenges in accurately detecting the combustion state of internal combustion engines, particularly in calculating the mass burn fraction (MBF), which is essential for efficient engine control, due to the need for frequent operation processing and the high cost and limited applicability of special pressure sensors.
Innovation Solution
A detecting device and method that calculates the mass burn fraction by detecting the crank angle based on frequency components of cylinder pressure changes, including harmonic wave components, without requiring a special pressure sensor, using a calculation unit that determines frequency groups corresponding to natural number multiples or (natural number −0.5) multiples of the fundamental frequency of the crankshaft's rotational frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If operation processing is performed repeatedly according to detection intervals of 1 deg. CA to calculate state variables showing combustion state, then measurement precision of combustion state is improved, but device complexity and computational load increase making it difficult to apply to general vehicles
Solution Approach 1:
The patent extracts only the essential frequency components (fundamental wave and secondary harmonic wave) from the complete cylinder pressure waveform analysis. By focusing on these specific frequency components rather than performing full waveform analysis at every 1 deg. CA interval, the system achieves adequate combustion state detection precision while significantly reducing computational load and operation processing complexity for ECU implementation.
Solution Approach 2:
Instead of performing complete operation processing at every detection interval, the patent applies partial action by calculating only the necessary frequency components (fundamental and secondary harmonics) that provide sufficient information for combustion state detection. This partial processing approach maintains measurement precision while reducing the overall computational burden.
2Measurement precision
If a special pressure sensor is used to directly detect cylinder pressure for calculating mass burn fraction, then measurement precision is improved, but device complexity and cost increase due to high temperature and pressure resistance requirements
Solution Approach 1:
The patent introduces an intermediary approach by using a standard cylinder pressure sensor to detect pressure changes, then processing the signal through frequency analysis to extract combustion state information. This intermediary signal processing method avoids the need for complex special pressure sensors while maintaining measurement precision through mathematical extraction of relevant frequency components.
Solution Approach 2:
The patent replaces the need for mechanically complex special pressure sensors with a combination of standard sensor and signal processing. By substituting the mechanical complexity of specialized sensors with computational analysis of frequency components, the system achieves the same measurement precision with simpler hardware.
3Loss of energy
If engine control is performed during stop and start operations or motor-engine switching, then fuel efficiency is improved, but reliability of combustion control deteriorates due to great operational state changes
Solution Approach 1:
The patent implements feedback by continuously monitoring the frequency components of cylinder pressure changes and using this information to adjust combustion control during dynamic operations. The detected frequency components provide real-time feedback on combustion state, enabling the ECU to maintain reliable control even during stop-start operations or motor-engine switching when operational states change greatly.
Solution Approach 2:
The patent applies dynamics by adapting the combustion control strategy based on real-time detection of frequency component changes. During stop-start operations or motor-engine switching, the system dynamically adjusts control parameters according to the detected combustion state from frequency analysis, maintaining reliability despite great operational state changes.
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
Enables efficient detection of the crank angle and calculation of the mass burn fraction, reducing the computational load and eliminating the need for expensive pressure sensors, thereby facilitating effective engine control and improving fuel efficiency and emissions control.
Implementation Method 1
a frequency component showing a state change amount of a state change of an detection target according to a change in a cylinder pressure depending on a combustion cycle of the engine, and including a harmonic wave component of a fundamental wave
Data Source
AI summary
A detecting device (1) detects a combustion state of an internal combustion engine (2) that transmits power via a crankshaft (11). The detecting device (1) includes a calculation unit (1b) that calculates a mass burn fraction by detecting a crank angle, on the basis of a frequency component showing a state change amount of a state change of a detection target according to a change in a cylinder pressure depending on a combustion cycle of the engine (2), and including a harmonic wave component of a fundamental wave of the frequency component.