Misfire Detection via Crankshaft Speed Sampling
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Solution Overview
Problem
Existing engine misfire detection methods face inaccuracies due to torque resonance, drive line induced speed fluctuations, and increased engine speed variability, leading to decreased signal-to-noise ratios and potential engine damage or unwanted emissions.
Innovation Solution
A method that detects engine misfires by measuring engine speeds at specific crankshaft positions corresponding to top dead center compression and subsequent positions, improving the signal-to-noise ratio through differential analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If engine speed data is collected throughout the complete travel of the piston, then more data is available for analysis, but the signal-to-noise ratio decreases due to torque resonance and drive line induced speed fluctuations
Solution Approach 1:
The patent divides the continuous piston travel into discrete sampling points at specific crankshaft positions (top dead center and predetermined subsequent positions). This segmentation allows selective collection of data only at critical combustion-related positions, filtering out noise from other positions where torque resonance and drive line fluctuations occur.
Solution Approach 2:
The patent applies different sampling strategies to different portions of the piston travel. High-frequency sampling is applied locally at top dead center where combustion events are most indicative, while other portions of the cycle are sampled less frequently or not at all, optimizing the signal-to-noise ratio by focusing measurement resources where they provide maximum diagnostic value.
2Reliability
If engine speed variability is measured throughout complete piston travel, then comprehensive combustion analysis is possible, but detection accuracy decreases around idle engine speed
Solution Approach 1:
The patent performs preliminary identification of top dead center position and predetermined crankshaft positions before conducting misfire detection. By pre-establishing these reference points, the system can accurately target sampling at the most diagnostic positions even during idle conditions where overall engine speed variability is high, thereby maintaining detection accuracy.
3Measurement precision
If crankshaft position sensor is used to measure speed variation, then engine misfire detection is enabled, but inaccuracies occur due to torque resonance and drive line induced fluctuations
Solution Approach 1:
The patent extracts only the speed variation data that occurs at specific crankshaft positions related to combustion events (top dead center and predetermined subsequent positions). By taking out only this relevant subset of data and discarding measurements taken at other positions where torque resonance and drive line fluctuations dominate, the system achieves accurate misfire detection while eliminating the harmful effects of these fluctuations.
Data Source
AI summary
The present invention generally includes a method of detecting a misfire in an internal combustion engine. The method includes detecting a first engine speed at a first crankshaft position that corresponds to about a top dead center compression position of a first piston within a first cylinder and detecting a second engine speed at a second crankshaft position that corresponds to about a position subsequent to the top dead center compression position. The method determines whether the misfire occurred in the first cylinder based on the first engine speed and the second engine speed. The method provides an improved signal to noise ratio for engine misfire detection.