Dual Mass Flywheel Misfire Detection Threshold Control
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Solution Overview
Problem
Existing methods for detecting combustion misfires in internal combustion engines with dual mass flywheels often incorrectly identify drive train oscillations as misfires, leading to unnecessary cylinder shut-off and emergency running programs, due to the inability to differentiate between misfires and oscillations caused by dual mass flywheel bounce.
Innovation Solution
A method that detects dual mass flywheel bounce simultaneously with combustion misfires and reduces or completely shuts off injection to relieve stress on the bow springs, thereby avoiding incorrect misfire detection by increasing the threshold value during critical operating points and reducing injection before misfire fault detection is triggered.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the threshold value for misfire detection is kept low to ensure accurate misfire detection, then combustion misfires can be reliably detected, but drive train oscillations are incorrectly detected as misfires
Solution Approach 1:
The system performs preliminary detection of dual mass flywheel bounce conditions by monitoring specific operating parameters (torque, rotational speed, and bounce frequency) before misfire detection occurs. When bounce conditions are detected, the system proactively increases the misfire detection threshold to prevent incorrect fault detection, rather than reacting after a false misfire signal is generated
Solution Approach 2:
The misfire detection threshold is made dynamic rather than static. The threshold value is continuously adjusted based on real-time operating conditions, specifically increasing when dual mass flywheel bounce is detected and returning to normal when bounce conditions subside. This dynamic adaptation allows the system to maintain high misfire detection accuracy while avoiding false positives during bounce events
2Object-affected harmful factors
If additional hardware (internal damper) is added to the dual mass flywheel to eliminate bounce oscillations, then incorrect misfire detection is prevented, but cost and weight increase
Solution Approach 1:
The system replaces the mechanical solution (internal damper) with an electronic control solution. Instead of adding physical damping elements to the dual mass flywheel, the system uses sensors to detect bounce conditions and a control unit to dynamically adjust the misfire detection threshold, thereby eliminating the need for additional mechanical components while achieving the same goal of preventing incorrect misfire detection
Solution Approach 2:
The system changes the detection parameter (threshold value) rather than modifying the physical system. By adjusting the threshold parameter based on operating conditions, the system prevents incorrect detection without requiring physical modifications to the dual mass flywheel structure, thus avoiding increased weight and cost
Data Source
AI summary
A method is provided for avoiding incorrect combustion misfire fault detection in an internal combustion engine in a motor vehicle with a dual mass flywheel. In order to detect combustion misfiring, a characteristic variable, which is dependent on the acceleration of the internal combustion engine, is determined continuously during the ongoing operation of the internal combustion engine and compared with a predefined irregular running threshold value. When the irregular running threshold value is exceeded, a combustion misfire is detected, wherein the frequency of detected combustion misfiring, for example at a specific number of crank shaft revolutions, is detected. When a defined frequency threshold is exceeded, a combustion misfire fault detection is activated. When a dual mass flywheel bounce is detected with the simultaneous detection of combustion misfiring, the injection of at least one cylinder is reduced or switched off for a predefined frequency or for a predefined time.