Knock Detection Ionic Current Signal Noise Discrimination
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Solution Overview
Problem
Existing knock detection apparatuses for internal combustion engines face challenges in accurately distinguishing knock signals from noise components of the same frequency, leading to difficulties in precise knock signal extraction, especially when noise components with comparable amplitude and duration to knock signals are present.
Innovation Solution
A knock detection apparatus that includes an ionic current detection device, a knock signal detection section, a crank angle detection section, a window setting section, a noise component detection section, and a knock determination section, which utilize the attenuation characteristics of ionic current signals after a combustion stroke to differentiate knock signals from noise components by setting a noise detection window and analyzing frequency component intensity and ionic current amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a band-pass filter is used to extract knock vibration component, then knock signal can be extracted, but noise component having same frequency cannot be distinguished from knock
Solution Approach 1:
The detection period is divided into two distinct segments: a knock detection period (from ignition timing to predetermined crank angle) and a noise detection period (after predetermined crank angle). This temporal segmentation allows separate analysis of knock signals and noise components, enabling the system to distinguish between actual knock events and noise by comparing characteristics across different time segments.
Solution Approach 2:
The invention transitions from frequency-domain analysis alone to a two-dimensional approach combining time-domain segmentation with frequency-domain analysis. By adding the temporal dimension (different detection periods) to the frequency analysis, the system can differentiate between knock and noise that have identical frequency characteristics but different temporal patterns.
2Measurement precision
If noise component with comparable amplitude and duration to knock signal is present, then knock signal extraction becomes very difficult, but conventional methods still cannot distinguish them
Solution Approach 1:
The system performs preliminary noise characterization by detecting noise components during the noise detection period (after predetermined crank angle) before making the final knock determination. This preliminary action establishes a baseline of noise characteristics that is then used to evaluate whether signals detected during the knock detection period represent actual knock or merely noise.
Solution Approach 2:
The noise detection result from the second period feeds back into the knock determination process. The ECU uses the detected noise component characteristics to adjust or validate the knock signal determination, creating a feedback mechanism that improves accuracy by continuously comparing expected noise patterns against actual signals.
3Measurement precision
If ionic current signal attenuation speed is utilized, then knock can be detected accurately, but detection system complexity increases
Solution Approach 1:
The detection system operates in periodic cycles, alternating between knock detection periods and noise detection periods synchronized with the engine's combustion strokes. This periodic action structure simplifies the system by using time-multiplexed detection rather than requiring simultaneous multi-channel analysis, reducing hardware complexity while maintaining high detection accuracy through systematic temporal sampling.
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
Enables precise detection of knock occurrences with high efficiency, even when noise components of the same frequency as knock vibrations are present, by accurately distinguishing between noise and knock signals, thereby improving knock detection accuracy and reducing incorrect determinations.
Implementation Method 1
ions are generated when fuel is burned or combusted in cylinders of an internal combustion engine, so an ionic current can be observed by a probe installed in each cylinder
Data Source
AI summary
A knock detection apparatus for an internal combustion engine can accurately detect the occurrence of a knock without an influence of a noise component even if the noise component having the same frequency as a knock vibration superposes on an ionic current signal. The apparatus includes an ionic current detection section, a knock signal detection section for detecting a knock signal based on an ionic current, a crank angle sensor for detecting a crank angle corresponding to a rotational position of the engine, a window setting section for setting a noise detection window, a noise component detection section for detecting a noise component in the window, and a knock determination section for determining the occurrence of a knock based on a relation between the noise component and the knock signal. The window setting section sets the window after a predetermined crank angle corresponding to an end of a combustion stroke of the engine.