Skip Fire Misfire Detection Using Adjacent Cylinder Analysis
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Solution Overview
Problem
Existing misfire detection systems are not suited for skip fire engine control systems, as they rely on consistent crankshaft acceleration patterns, which are disrupted by the skipping of cylinders, leading to inaccurate misfire detection and increased false positives.
Innovation Solution
A method that assigns windows to target firing opportunities and measures engine parameters like crankshaft angular acceleration, taking into account the skip/fire status of adjacent cylinders to determine if a misfire has occurred, using a torque model to verify the presence of a misfire and adjust firing sequences accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional misfire detection systems are used in skip fire engine control, then the system structure remains simple, but misfire detection accuracy deteriorates due to disrupted crankshaft acceleration patterns
Solution Approach 1:
The detection window is segmented into multiple sub-windows corresponding to different cylinder firing opportunities. By dividing the analysis into discrete segments and evaluating each independently while considering the skip/fire status of adjacent cylinders, the system achieves accurate misfire detection without requiring complex global analysis of the entire engine cycle.
Solution Approach 2:
The system performs preliminary determination of skip/fire status for adjacent cylinders before conducting the misfire detection analysis. This preliminary action allows the detection algorithm to pre-adjust expectations for crankshaft acceleration patterns based on known skip events, thereby improving detection accuracy without adding complex real-time adjustments.
2Use of energy by moving object
If cylinders are skipped during operation to improve fuel efficiency, then energy consumption decreases, but misfire detection reliability deteriorates due to inconsistent firing patterns
Solution Approach 1:
The detection system dynamically adapts to skip fire operation by adjusting detection thresholds and analysis methods based on the real-time skip/fire status of cylinders. This dynamic adaptation maintains reliable misfire detection despite the inconsistent firing patterns inherent in skip fire operation, allowing the system to remain reliable while preserving fuel efficiency benefits.
Solution Approach 2:
The system uses feedback from the engine control system regarding which cylinders are skipped or fired during each cycle. This feedback information is integrated into the misfire detection algorithm, allowing the system to distinguish between intentional skips and actual misfires, thereby maintaining high detection reliability while preserving the fuel efficiency gains from skip fire operation.
3Loss of energy
If adjacent cylinders are deactivated to reduce pumping losses, then energy efficiency improves, but crankshaft acceleration measurement accuracy deteriorates due to reduced torque variation
Solution Approach 1:
The detection system applies local quality analysis by examining the specific contribution of each cylinder to crankshaft acceleration based on its skip/fire status. Instead of relying on overall torque variation from all cylinders, the system focuses on local acceleration changes attributable to individual cylinder events, maintaining measurement accuracy even when adjacent cylinders are deactivated and overall torque variation is reduced.
Solution Approach 2:
The system transitions from analyzing one-dimensional overall crankshaft acceleration to examining acceleration patterns across multiple dimensions including temporal sequencing of cylinder firings and the specific timing relationships between adjacent cylinders. This dimensional expansion allows accurate misfire detection even when pumping losses are reduced through cylinder deactivation, as the system can distinguish misfire patterns from normal skip fire operation through multi-dimensional pattern recognition.
Data Source
AI summary
A variety of methods and arrangements for detecting misfire in a skip fire engine control system are described. In one aspect, a window is assigned to a target firing opportunity for a target working chamber. A change in an engine parameter is measured during the window. A determination is made as to whether a firing opportunity before the target firing opportunity is a skip or a fire and/or whether a firing opportunity after the target firing opportunity is a skip or a fire. Based at least in part on this skip/fire determination, a determination is made as to whether the target working chamber has misfired. In various embodiments, if the target working chamber is identified as persistently misfiring, the firing sequence is modified so that the target working chamber is deactivated and excluded from the firing sequence. In still other embodiments, a torque model is used to detect engine-related problems.