Misfire Detection Device Using Crank Angle Interval Comparison
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Solution Overview
Problem
Existing misfire detection systems in internal combustion engines face inaccuracies due to manufacturing variations in crank angle sensors and the stopping process, leading to erroneous misfire determinations when calculating rotation fluctuation amounts based on instantaneous rotation speed.
Innovation Solution
A misfire detection device that determines whether a misfire has occurred by comparing the relative value of the determination subject rotation fluctuation amount with a comparison subject rotation fluctuation amount, and adjusts this comparison based on the angular interval between crank angles at which compression top dead center occurs, thereby limiting errors caused by tolerance and the stopping process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotation fluctuation amount corresponding to the preceding 360° CA is calculated based on the instantaneous rotation speed during the stopping process, then the misfire detection can be performed, but an erroneous determination of misfire may result due to the stopping process affecting the rotation fluctuation amount
Solution Approach 1:
The patent extracts and removes the stopping process period from the misfire detection calculation. Specifically, it identifies when the stopping process is occurring (when shaft torque is not zero and combustion control is stopped) and excludes this period's rotation fluctuation data from the misfire determination, thereby preventing erroneous detections while maintaining accurate misfire detection capability
Solution Approach 2:
The patent performs preliminary identification of the stopping process condition before executing misfire detection. By detecting whether shaft torque is not zero and whether combustion control has been stopped, the system prepares and flags the stopping process period in advance, allowing the misfire detection algorithm to properly handle or exclude this period's data
2Manufacturing precision
If the threshold value is compared with a relative value obtained by subtracting the rotation fluctuation amount from the preceding 360° CA, then the effects of manufacturing variations in crank angle sensors are limited, but the stopping process introduces errors that counteract this benefit
Solution Approach 1:
The patent dynamically adjusts the misfire detection methodology based on engine operating conditions. It continuously monitors shaft torque and combustion control status to determine when the stopping process is active, and adaptively changes the detection approach - using relative comparison when normal operation and direct comparison when stopping process is active - thereby maintaining accuracy across varying conditions
Data Source
AI summary
A misfire detection device includes processing circuitry configured to execute a stopping process stopping combustion control of an air-fuel mixture in one or more cylinders and a determination process determining whether a misfire has occurred based on a value of a determination subject rotation fluctuation amount, that is, a rotation fluctuation amount of a determination subject cylinder for misfire. A comparison subject rotation fluctuation amount is a rotation fluctuation amount corresponding to a crank angle separated by a predetermined angular interval from a crank angle corresponding to the determination subject rotation fluctuation amount. The determination process includes a process determining the misfire based on a value of the determination subject rotation fluctuation amount when the predetermined angular interval equals an angular interval between crank angles at which compression top dead center appears in the one or more of the cylinders and the determination subject cylinder during the stopping process.