Knock Control Device Using Variable Filter Coefficient
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Solution Overview
Problem
Existing knock detection methods in internal combustion engines face challenges in accurately distinguishing between continuous knock generation and non-generation states, leading to incorrect knock determination and potential engine damage, especially when the load changes or during stationary conditions, due to increased CPU loads and costs associated with additional hardware and complex data measurement requirements.
Innovation Solution
A knock control device that calculates a background level using primary filter calculation and sets a maximum value for the variation of the output signal from the knock sensor when no knock is generated, allowing for correct knock detection without requiring new data or increased man-hours, and minimizing CPU loads by avoiding the need for additional hardware like envelope detection circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If smoothing processing is continued to stabilize the background level, then the background level is stabilized, but the background level is not immediately increased when load increases, causing knock determination value to become excessively small and knock to be erroneously determined
Solution Approach 1:
The patent applies dynamics by making the filter coefficient variable rather than fixed. The filter coefficient is dynamically adjusted based on the variation of the output signal from the knock sensor - when variation is large, a larger filter coefficient is used for stronger smoothing; when variation is small, a smaller filter coefficient is used for faster response. This resolves the contradiction between stability and responsiveness.
Solution Approach 2:
The patent changes the parameter of the filter coefficient based on signal variation characteristics. By monitoring the variation of the knock sensor output and adjusting the filter coefficient accordingly, the system adapts its smoothing strength to match actual operating conditions, preventing both over-smoothing and under-smoothing problems.
2Speed
If the upper limit value of updating quantity is increased to follow background level immediately when load changes, then the background level follows load changes, but even very strong knock signals cannot be detected during continuous knock generation state
Solution Approach 1:
The patent dynamically adjusts the filter coefficient based on signal variation to resolve this contradiction. When the engine is in a continuous knock generation state, the signal variation is large, causing the system to use a larger filter coefficient for stronger smoothing, which enables detection of even very strong knock signals while maintaining fast response to load changes.
Solution Approach 2:
The system uses feedback from the knock sensor output variation to adjust the filter coefficient. The variation information is fed back to control the smoothing strength, creating a closed-loop system that adapts to continuous knock conditions and maintains detection capability throughout.
3Measurement precision
If envelope detection circuit is added to detect knock by inclination of envelope, then knock detection accuracy is improved, but CPU load and costs increase
Solution Approach 1:
The patent extracts the essential knock detection function from complex envelope detection hardware. Instead of using an envelope detection circuit, the system extracts knock information by analyzing the variation of the raw knock sensor output signal and comparing it against dynamically adjusted thresholds, achieving the same detection accuracy with much simpler hardware and lower CPU load.
Solution Approach 2:
The patent replaces the mechanical/envelope-based detection approach with a direct signal variation analysis method. By substituting the envelope detection circuitry with a simpler variation-based comparison system, the patent achieves knock detection without the hardware complexity and CPU overhead associated with envelope detection.
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
This approach enables accurate and cost-effective knock detection with reduced processing and no additional hardware requirements, preventing engine damage by correctly identifying knock generation states and adjusting ignition timing accordingly.
Implementation Method 1
a knock sensor which sends an a vibration waveform signal based on the vibration of the internal combustion engine
Data Source
AI summary
In a knock control device of an internal combustion engine equipped with a control unit which updates a background level based on an output signal from a knock sensor and detects the generation of a knock by comparing a variation of the background level with a knock determination value, a determination as to whether the knock is generated is performed by((variation of first filter value of peak hold value)>((1−filter coefficient)/(1+filter coefficient)×(predetermined value larger than maximum value of variation of peak hold value in case where knock is not generated))).