Knock Sensor Signal Processing for Ignition Timing Control

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Solution Overview

Problem

Existing methods for determining knocking in internal combustion engines are not always precise, leading to inappropriate ignition timing control due to initial determination value discrepancies with actual engine vibration magnitudes, resulting in potential ignition timing retardation or advancement issues.

Innovation Solution

A device with a knock sensor and operation unit that calculates knock magnitude and adjusts ignition timing based on comparisons with determination values, correcting these values using median and standard deviation calculations to quickly approximate actual engine vibration, thereby preventing undue ignition timing adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a fixed initial determination value is used for knocking detection, then the device complexity is reduced, but the measurement precision of knocking detection deteriorates during the initial period

Engineering Contradiction:

Improvedetermination value adjustment mechanismVSAvoidknocking detection precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The determination value is transformed from a fixed parameter to a dynamic one that automatically adjusts based on vibration magnitude measurements. The system performs preliminary measurements to calculate the mean and standard deviation, then sets the determination value as mean plus a coefficient times standard deviation, allowing the threshold to adapt to actual engine conditions rather than remaining static

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Before formal knocking detection begins, the system performs preliminary vibration magnitude measurements to establish the baseline characteristics of engine vibration. This preliminary action includes calculating the mean and standard deviation of initial measurements, which are then used to set an appropriate determination value that accounts for the specific engine's vibration characteristics

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the determination value is corrected based on occurrence frequency of knocking, then the reliability of ignition timing control is improved, but the loss of time for determination value correction increases

Engineering Contradiction:

Improveignition timing control reliabilityVSAvoiddetermination value correction time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system implements feedback by continuously monitoring whether knocking occurs and using this information to adjust the determination value. When knocking is detected, the system recalculates the determination value based on updated vibration measurements, creating a closed-loop control system that improves reliability over time while the correction occurs in the background during normal operation

Inventive Principle:

Principle #23Feedback

3Measurement precision

If statistical processing is used to calculate determination value, then the measurement precision is improved, but the device complexity and processing time increase

Engineering Contradiction:

Improvedetermination value accuracyVSAvoidprocessing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system changes the parameter of determination value from a fixed predetermined value to a statistically derived value based on measured vibration magnitudes. By calculating the mean and standard deviation from preliminary measurements and setting the determination value as mean plus coefficient times standard deviation, the system achieves adaptive precision without requiring complex real-time statistical processing during knocking detection

Inventive Principle:

Principle #35Parameter changes

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 allows for precise control of ignition timing, reducing the likelihood of ignition timing being unduly retarded or advanced, thus improving engine output and knocking suppression by rapidly adjusting determination values based on occurrence frequency.

Implementation Method 1

a knock sensor detecting magnitude of vibration occurring in the internal combustion engine

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS7392788B2Device and method for controlling ignition timing of internal combustion engine

Publication Date: 2008.07.01 TOYOTA JIDOSHA KK

AI summary

An engine ECU executes a program including a step of, when an absolute value of a difference between median value V(50) of magnitude values LOG(V), which is obtained by logarithmically converting a magnitude V detected based on a signal sent from a knock sensor, and a determination value V(KX) used for determining presence or absence of knocking is greater than the product of a standard deviation σ and a coefficient U(3) in a frequency distribution of magnitude values LOG(V) for N cycle(s), setting a value obtained by adding the product of the standard deviation σ and the coefficient U(3) to the median value V(50) of magnitude values LOG(V) as the determination value V(KX).