ECU Air-Fuel Sensor Signal Path Switching
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Solution Overview
Problem
Existing electronic control units face challenges in accurately detecting the impedance of air-fuel ratio sensors in low-temperature environments due to signal noise from filter circuits, which affects the accuracy of temperature measurement and fuel mileage.
Innovation Solution
An electronic control unit with a microcontroller and air-fuel ratio control IC that switches between upstream and downstream power supply paths to select signals based on temperature conditions, improving signal accuracy by avoiding the influence of filter circuits in low-temperature environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the power supply path is configured to serve as a filter circuit to remove signal noise, then signal noise is reduced, but the time constant of the filter circuit changes and impedance detection accuracy deteriorates in low-temperature environments
Solution Approach 1:
The patent applies dynamics by making the signal acquisition path configurable based on operating conditions. The control unit selectively switches between acquiring signals from the upstream side (through the filter circuit) and downstream side (bypassing the filter circuit) of the air-fuel ratio sensor, depending on whether the sensor is in a low-temperature or normal-temperature environment. This dynamic adaptation resolves the contradiction by optimizing the signal path for each temperature condition.
Solution Approach 2:
The patent applies local quality by treating different parts of the signal acquisition system differently based on local conditions. Specifically, in low-temperature environments, the system uses the downstream side signal path that bypasses the filter circuit to avoid its adverse effects, while in normal-temperature environments, it uses the upstream side signal path that goes through the filter circuit for noise reduction. This localized optimization resolves the contradiction between noise filtering and measurement accuracy.
2Loss of energy
If the temperature of the air-fuel ratio sensor is lowered during engine idle or stop state to improve fuel mileage, then fuel mileage is improved, but impedance detection accuracy deteriorates due to filter circuit influence
Solution Approach 1:
The patent applies dynamics by dynamically switching the signal acquisition strategy based on engine operating state and sensor temperature. During engine idle or stop states when the sensor is in a low-temperature environment, the control unit acquires the signal from the downstream side to bypass the filter circuit and maintain accurate impedance detection. This allows the system to lower sensor temperature for fuel economy while preserving measurement accuracy through adaptive signal path selection.
3Measurement precision
If a reverse voltage is applied to the oxygen sensor to diminish voltage application influence, then sensor output accuracy is improved, but additional control complexity is introduced
Solution Approach 1:
The patent applies the taking out principle by extracting the problematic filter circuit from the signal acquisition path for low-temperature operation. Instead of using the filter circuit (power supply path) that causes measurement errors in low-temperature environments, the system separates this component out and uses an alternative downstream side signal path that bypasses the filter circuit, thereby eliminating the source of measurement errors without adding complex control mechanisms.
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
Enhances the accuracy of impedance detection and temperature measurement of air-fuel ratio sensors, even in low-temperature conditions, thereby improving fuel mileage and reducing signal noise interference.
Implementation Method 1
an air-fuel ratio sensor is used to detect an excess air amount in the exhaust gas from the internal-combustion engine... calculates an impedance of the air-fuel ratio sensor as a value ΔV/ΔI... The impedance and temperature in the air-fuel sensor are correlated to each other
Implementation Method 2
by controlling the temperature of the air-fuel ratio sensor with a heater, the air-fuel ratio sensor may be brought to have an activation temperature
Data Source
AI summary
An electronic control unit controls an air-fuel ratio sensor to detect an air-fuel ratio in an exhaust gas from an internal-combustion engine. An A/D converter and a sample value processor obtain a signal based on an impedance of the air-fuel ratio sensor in response to a power supply to the air-fuel ratio sensor via filters. A microcomputer determines an environment temperature of the air-fuel ratio sensor based on the signal. A switch or the microcomputer switches between an upstream side voltage supply path and a downstream side voltage supply path to obtain a signal depending on whether the air-fuel ratio sensor is operating in a low-temperature environment to improve the accuracy of the obtained signal.