Engine Misfire Detection via Dynamic High Pass Filter
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Solution Overview
Problem
Existing internal combustion engine systems face challenges in accurately detecting engine misfires across varying rotation speeds due to resonance interference from distortional elements, leading to inaccurate detection and potential false readings.
Innovation Solution
An internal combustion engine system with a rotational position detector, rotation speed detector, and a high pass filter with a time constant set according to the engine's rotation speed, which eliminates resonance frequencies by applying the high pass filter to the rotational variation, ensuring accurate misfire detection irrespective of engine speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high pass filter is applied to eliminate low frequency noise at low engine rotation speed, then misfire detection accuracy is improved, but resonance interference from the distortional element cannot be eliminated
Solution Approach 1:
The patent applies a high pass filter with a dynamically adjusted time constant that varies with engine rotation speed. At low rotation speeds, a longer time constant is used to eliminate low frequency noise from engine swing back, while at high rotation speeds, a shorter time constant eliminates resonance interference from the distortional element. This dynamic adjustment allows the system to adapt to different operating conditions and eliminate different types of interference appropriately.
Solution Approach 2:
The patent changes the parameter of the high pass filter (time constant) based on engine rotation speed. By setting different time constant values according to the rotation speed, the filter characteristics are optimized for different operating conditions, enabling effective elimination of both low frequency noise at low speeds and resonance interference at high speeds, thereby improving misfire detection accuracy across the entire rotation speed range.
2Measurement precision
If a low pass filter is applied to eliminate high frequency noise at high engine rotation speed, then misfire detection accuracy is improved, but resonance interference from the distortional element cannot be eliminated
Solution Approach 1:
The system dynamically switches between high pass and low pass filter applications based on engine rotation speed. At high rotation speeds where resonance interference occurs, the system applies a low pass filter with an appropriately set time constant to eliminate the high frequency resonance components while preserving the misfire detection signal, thus improving detection accuracy without being affected by resonance interference.
3Measurement precision
If multiple different filters are applied corresponding to different rotation speed levels, then misfire detection accuracy across all rotation speeds is improved, but device complexity increases
Solution Approach 1:
The patent employs a single high pass filter that serves multiple functions across different rotation speed ranges. By dynamically adjusting the time constant parameter, the same filter structure can eliminate low frequency noise at low speeds and resonance interference at high speeds, eliminating the need for multiple separate filters and reducing system complexity while maintaining detection accuracy across all operating conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves highly accurate misfire detection by eliminating resonance interference, preventing false alarms and ensuring reliable engine performance across different rotation speeds.
Implementation Method 1
a rotational variation of the crankshaft by the occurrence of an engine misfire causes resonance of the distortional element. Generation of the resonance interferes with accurate detection of the occurrence of an engine misfire
Implementation Method 2
In the condition of the low engine rotation speed, there is a low frequency noise caused by an 'engine swing back' in the process of detecting a rotational variation of a crankshaft. The high pass filter is thus applied for engine misfire detection in the condition of the low engine rotation speed to eliminate the low frequency noise
Implementation Method 3
In the condition of the high engine rotation speed, on the other hand, there is a high frequency noise caused by a distortional vibration or 'rattling' of the crankshaft in the process of detecting the rotational variation of the crankshaft. The low pass filter is thus applied for engine misfire detection in the condition of the high engine rotation speed to eliminate the high frequency noise
Data Source
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AI summary
The internal combustion engine system of the invention calculates a time constant T of a high pass filter for eliminating a resonance component of a damper as a distortional element from a rotation speed Ne of an engine, and sets the high pass filter with computation of a transfer function from the time constant T (steps S110 and S120). The set high pass filter is applied to a 30-degree rotation time T30 representing a rotational variation of the engine to obtain a filtered 30-degree rotation time F30 with elimination of the resonance component of the damper 28 (step S130). The occurrence of an engine misfire is detected, based on a 30-degree rotation time difference D30 and a misfire detection base difference J30 computed from the filtered 30-degree rotation times F30 (step S140). This arrangement ensures highly-accurate detection of the occurrence of a misfire in the engine constructed to output power via the damper as the distortional element, irrespective of the rotation speed Ne of the engine.