Misfire Determination Device Combustion Phase Shift
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Solution Overview
Problem
Conventional misfire determination devices for internal combustion engines inaccurately determine misfires when ignition timing is controlled to a retard angle, as they fail to appropriately extract combustion components due to phase shifts in rotational speed waveforms, leading to decreased accuracy and increased costs in preparing tables to account for ignition timing and other factors.
Innovation Solution
A misfire determination device that detects combustion state parameters, retrieves extreme values of these parameters from the start of the combustion stroke to a predetermined crank angle, sets a subsequent crank angle section as the misfire determination parameter calculation section, and calculates a misfire determination parameter based on detected parameters, allowing for accurate misfire determination without pre-prepared tables or maps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ignition timing is controlled to a retard angle side, then knocking is suppressed and catalyst warm-up is promoted, but the phase of the rotational speed waveform is shifted to the retard angle side, causing the misfire determination parameter to include rotational speed before combustion starts, which decreases misfire determination accuracy
Solution Approach 1:
The patent applies dynamics by making the misfire determination parameter calculation section variable rather than fixed. The start timing of the calculation section is dynamically adjusted based on the detected combustion start timing, allowing the system to adapt to different ignition timing conditions (optimum, retard, or advance) without requiring pre-prepared tables. This dynamic adjustment ensures that the calculation section always captures the appropriate combustion phase regardless of ignition timing variations.
Solution Approach 2:
The patent changes the parameter of the calculation section timing based on combustion start timing detection. By detecting when combustion actually starts and adjusting the start timing of the misfire determination parameter calculation section accordingly, the system maintains accuracy across different operating conditions. This parameter change approach eliminates the need for fixed tables while adapting to varying ignition timing, fuel characteristics, and cylinder variations.
2Reliability
If a table representing the relationship between ignition timing and offset amount is prepared, then misfire determination accuracy can be maintained under different ignition timing conditions, but a large amount of man-hours is needed for creating the table through experiments, leading to increased cost
Solution Approach 1:
The patent implements self-service by enabling the system to automatically determine the appropriate calculation section timing through real-time detection of combustion start timing. Instead of relying on pre-prepared tables created through extensive experiments, the system autonomously adapts to different conditions by detecting combustion characteristics and adjusting its calculation parameters accordingly. This eliminates the need for manual table creation while maintaining accuracy.
Solution Approach 2:
The system dynamically adjusts the misfire determination parameter calculation section based on detected combustion start timing, replacing static tables with a dynamic adaptation mechanism. This allows the system to automatically handle different ignition timing conditions, fuel types, and cylinder variations without requiring pre-programmed offset values, significantly reducing development time and cost.
3Ease of operation
If the misfire determination parameter is calculated with the entire combustion stroke, then the calculation is simple, but the parameter includes rotational speed before combustion starts, making it impossible to appropriately extract only the combustion component, which decreases misfire determination accuracy
Solution Approach 1:
The patent applies segmentation by dividing the combustion stroke into distinct calculation sections. The misfire determination parameter calculation section is segmented to start after the detected combustion start timing rather than from the beginning of the combustion stroke. This segmentation isolates the combustion component from the pre-combustion rotational speed, maintaining calculation simplicity while improving accuracy by excluding irrelevant data.
Solution Approach 2:
The patent extracts only the relevant combustion component by adjusting the calculation section timing to start after combustion begins. By taking out the pre-combustion rotational speed data from the calculation, the system maintains ease of operation through straightforward integration while ensuring that only the combustion-related rotational speed changes are included in the misfire determination parameter.
Data Source
AI summary
A misfire determination device, for an internal combustion engine, according to the present invention detects a combustion state parameter of the internal combustion engine, retrieves an extreme value of the combustion state parameter in an extreme value retrieval section from a start timing of a combustion stroke to a predetermined crank angle (step 5), upon retrieval of the extreme value, sets a predetermined crank angle section subsequent to a crank angle corresponding to the extreme value as a misfire determination parameter calculation section (step 6, expression 5), calculates a misfire determination parameter based on the combustion state parameter that has been detected in the misfire determination parameter calculation section (step 6), and determines a misfire based on the misfire determination parameter (steps 7 to 9).