Misfire Detection in Irregular Interval Engines
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Solution Overview
Problem
In engines with irregular explosion intervals, conventional misfire determination methods based on instantaneous angular velocity are inaccurate due to reduced decrease in crankshaft angular velocity, making it difficult to detect misfires.
Innovation Solution
A misfire determination device calculates an average torque correlation amount using angular position signals and performs misfire determination at specific optimal angles for each cylinder, setting thresholds based on crank angle intervals to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional misfire determination method using instantaneous angular velocity is applied to engines with irregular explosion intervals, then the method is simple to implement, but the measurement precision of misfire detection deteriorates due to reduced decrease in crankshaft angular velocity
Solution Approach 1:
The patent changes the parameter from instantaneous angular velocity to average angular velocity calculated over a predetermined period. This transformation allows the system to smooth out the effects of irregular explosion intervals while preserving the ability to detect misfire conditions, thereby maintaining measurement precision without increasing device complexity
Solution Approach 2:
The patent introduces an intermediary calculation process that computes average angular velocity as a mediator between the raw instantaneous velocity data and the misfire determination. This intermediary average value filters out the irregularities caused by unequal explosion intervals while still reflecting true misfire conditions when they occur
2Device complexity
If misfire determination is performed at a common angular position for all cylinders, then the control logic is simplified, but the measurement precision deteriorates because optimal determination angles differ for each cylinder in irregular interval engines
Solution Approach 1:
The patent applies local quality by setting different angular positions for misfire determination for each cylinder based on its specific characteristics. Instead of using a uniform approach for all cylinders, the system tailors the determination angle to each cylinder's position in the firing sequence, thereby optimizing detection accuracy for each individual cylinder while managing complexity through systematic variation
Data Source
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AI summary
A misfire determination device of an engine in which explosion occurs at unequal intervals, the engine including a plurality of cylinders and a crankshaft which is angularly displaced at a different angle between expansion strokes, is configured to calculate generated torque correlation amount correlated with generated torque, based on an angular position signal of the crankshaft, and perform misfire determination, based on an average value of the generated torque correlation amount in an interval less than one cycle of the engine, at an angular position of the crankshaft which is different from an angular position of the crankshaft at an ignition timing.