Misfire Detection Threshold Correction for Fuel Cut-Off Cylinders
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Solution Overview
Problem
Existing misfire determination systems for internal combustion engines face challenges in accurately detecting misfires, especially when the reference cylinder is a fuel cut-off cylinder, leading to incorrect determination results due to the influence of manufacturing variations and operational conditions.
Innovation Solution
A misfire determination apparatus and method that implements a single-cylinder fuel cut-off process, calculates instantaneous speed and rotation fluctuation amounts, and adjusts the determination threshold based on the relationship between these values to account for the fuel cut-off cylinder's influence, ensuring accurate misfire detection by using a reference cylinder that reached an earlier expansion stroke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference cylinder is used for misfire determination, then measurement precision is improved, but when the reference cylinder is a fuel cut-off cylinder, incorrect determination results occur due to operational conditions
Solution Approach 1:
The patent introduces a correction value as an intermediary element to mediate between the rotation fluctuation amount and the determination threshold. When the reference cylinder is a fuel cut-off cylinder, the correction value compensates for the influence of fuel cut-off operations, allowing accurate misfire determination despite the non-standard operational conditions of the reference cylinder
Solution Approach 2:
The patent dynamically adjusts the determination threshold by adding a correction value based on the operational state of the reference cylinder. When fuel cut-off is performed in the reference cylinder, the threshold parameter is modified to account for this condition, transforming the determination criterion to maintain accuracy under varying operational parameters
2Productivity
If single-cylinder fuel cut-off control is implemented, then productivity is improved through regeneration process, but misfire determination accuracy deteriorates when the reference cylinder undergoes fuel cut-off
Solution Approach 1:
The patent performs preliminary identification of whether the reference cylinder is a fuel cut-off cylinder before conducting misfire determination. By detecting the fuel cut-off state in advance, the system can apply appropriate correction values to the determination threshold, ensuring accurate misfire detection even when the reference cylinder is undergoing fuel cut-off for regeneration purposes
3Measurement precision
If rotation fluctuation amount is calculated from instantaneous speed, then measurement precision is improved, but manufacturing variations in crank angle sensors still influence the result
Solution Approach 1:
The patent employs feedback by continuously monitoring the rotation fluctuation amount and comparing it against a dynamically adjusted determination threshold that incorporates correction values. This feedback mechanism compensates for manufacturing variations in crank angle sensors by adapting the threshold based on observed rotational characteristics and fuel cut-off conditions
Data Source
AI summary
A CPU determines that misfires are occurring in a cylinder subject to determination of whether misfires are occurring when a value obtained by subtracting a rotation fluctuation amount ΔT30[n−2] from a rotation fluctuation amount ΔT30[n] is greater than or equal to a determination threshold. The rotation fluctuation amount ΔT30[n] is subject to the misfire determination. The rotation fluctuation amount ΔT30[n−2] is 360° CA earlier than the rotation fluctuation amount ΔT30[n]. When stopping fuel supply to a cylinder #1 and determining whether misfires are occurring in cylinder #4, the CPU determines whether misfires are occurring after executing a correcting process that corrects the determination threshold to a second determination threshold Δth2, which is less than a first determination threshold Δth1.