Air-Fuel Ratio Detection Device Without Analog Filters
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Solution Overview
Problem
Existing air-fuel ratio detection devices have low detection responsiveness due to the use of low-pass and high-pass filters, which slow down the detection of sensor current changes and increase device size.
Innovation Solution
An air-fuel ratio detection device that applies a direct current voltage and alternates between two different voltages at a predetermined period, using an amplification section, A/D conversion, and arithmetic calculations to detect sensor current and impedance without the need for low-pass and high-pass filters, thereby enhancing responsiveness and reducing device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If low-pass filter and high-pass filter are used to detect sensor current and impedance respectively, then measurement precision is improved, but device complexity and size increase
Solution Approach 1:
The patent extracts and eliminates the low-pass filter and high-pass filter from the traditional detection circuit. Instead of using filters to separate DC and AC components, the invention directly measures the sensor current through a simplified circuit with a current detection resistor and voltage application sections, achieving the same measurement function with reduced complexity
Solution Approach 2:
The voltage application section serves multiple functions: it applies DC voltage for normal operation, applies alternating voltage for impedance detection, and enables the same circuit to perform both sensor current measurement and temperature detection without requiring separate filter circuits for each function
2Measurement precision
If low-pass filter is used to convert amplifier output into direct current, then sensor current detection is achieved, but detection responsiveness decreases
Solution Approach 1:
The patent removes the low-pass filter that causes response delay. By directly measuring the voltage across the current detection resistor without converting to DC through filtering, the system achieves immediate response to sensor current changes while maintaining measurement accuracy through direct digital conversion of the amplified signal
Solution Approach 2:
The patent replaces the mechanical/filter-based signal conversion process (analog low-pass filtering) with a direct digital conversion approach. The amplified voltage signal is directly converted to digital data by the A/D converter, eliminating the time delay inherent in analog filter processing and achieving faster detection responsiveness
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 solution allows for quick detection of sensor current changes and eliminates the need for additional filters, resulting in improved responsiveness and a more compact device design.
Implementation Method 1
An air-fuel ratio sensor for detecting an air-fuel ratio in exhaust gas from an internal combustion engine, a resistor for electric current detection
Implementation Method 2
an amplification section that amplifies a voltage across the resistor and outputs an amplified voltage as an output voltage
Implementation Method 3
An A/D conversion section that converts the output voltage of the amplification section into digital signals
Data Source
AI summary
An air-fuel ratio detection device includes a resistor, a first voltage application section, a second voltage application section, an amplification section, an A/D conversion section, and an arithmetic section. The first voltage application section applies a direct current voltage to a first end of a series circuit constituted of an air-fuel ratio sensor and the resistor. The amplification section amplifies a voltage across the resistor and outputs an amplified voltage as an output voltage. The A/D conversion section carries out an A/D conversion of the output voltage every time before the second voltage application section switches a voltage applied to a second end of the series circuit between a first voltage and a second voltage. The arithmetic section calculates a sensor current and an impedance of the air-fuel ratio sensor using two consecutive A/D conversion results by the A/D conversion section.