Misfire Detection in Engines with Partial EGR Circuits
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for detecting generalized misfires in internal combustion engines fail to distinguish between malfunctions in the exhaust gas recirculation circuit and poor fuel quality, as both can cause misfires, complicating diagnosis and maintenance.
Innovation Solution
A device and method that calculate a diagnostic criterion by comparing theoretical and apparent engine stability terms, allowing for differentiation between misfires caused by fuel quality issues and those due to exhaust gas recirculation circuit faults, using a module to determine apparent stability from engine output parameters and calculate a diagnostic criterion proportional to the difference between theoretical and apparent stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If exhaust gas recirculation is activated to improve combustion efficiency, then combustion stability is improved, but the ability to detect fuel quality issues is degraded because EGR masks misfire symptoms
Solution Approach 1:
The system performs a preliminary diagnostic test by temporarily deactivating the EGR circuit before conducting misfire detection. This preliminary action removes the masking effect of recirculated exhaust gases, allowing accurate detection of fuel quality issues. The EGR circuit is then restored to its normal operating state after diagnosis.
Solution Approach 2:
The diagnostic system dynamically adjusts the EGR valve position during the diagnostic phase, transitioning from the normal recirculation mode to a closed or partially closed position. This dynamic change in EGR flow rate enables the system to create different operating conditions that reveal fuel quality problems which are masked during normal EGR operation.
2Measurement precision
If traditional misfire detection methods are used, then generalized misfire can be detected, but the cause of misfire cannot be distinguished between fuel quality and EGR circuit malfunction
Solution Approach 1:
The diagnostic system segments the misfire detection process into distinct phases: normal operation phase with EGR active, diagnostic phase with EGR deactivated, and result analysis phase. By separating the detection process into these segments, the system can compare combustion characteristics under different EGR conditions to determine whether misfire is caused by fuel quality or EGR circuit issues.
Solution Approach 2:
The system changes the EGR flow rate parameter during diagnosis, switching from the normal recirculation flow rate to a reduced or zero flow rate. This parameter change affects the combustion characteristics, and by comparing the misfire signals before and after the parameter change, the system can identify the root cause of the misfire.
3Loss of substance
If EGR circuit malfunction is treated as the default cause of misfire, then unnecessary fuel drainage is avoided, but actual fuel quality issues remain undetected
Solution Approach 1:
The system uses feedback from comparing misfire detection results under different EGR conditions to determine the cause of misfire. If misfire detection signals change significantly when EGR is deactivated, the feedback indicates fuel quality issues. If the signals remain similar, the feedback suggests EGR circuit problems. This feedback mechanism prevents both unnecessary fuel drainage and missed fuel quality diagnoses.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
This device (58) for detecting a failure in an internal combustion engine associated with a partial exhaust gas recirculation circuit at the engine intake includes a means for detecting a generalized misfire in a plurality of engine cylinders. This device includes a receiving module (64) for a theoretical engine stability term for a selected combustion efficiency point without exhaust gas recirculation, a determining module (66) for an apparent engine stability term for said combustion efficiency point, a calculation module (68) for a diagnostic criterion based on the theoretical stability term and the apparent stability term, and a comparison module (70) capable of comparing the diagnostic criterion calculated by the calculation module (68) with a predetermined threshold.