Engine Controller Exhaust Gas Sensor Abnormality Detection
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Solution Overview
Problem
Existing engine controllers fail to reliably detect sky short circuit, ground, and disconnection abnormalities in exhaust gas sensors, particularly when the ground abnormality of the negative terminal wiring is generated, leading to incomplete abnormality judgment and potential operational disruptions.
Innovation Solution
The engine controller employs a microprocessor with multi-channel AD converters and a program memory that applies an offset voltage to the negative terminals of exhaust gas sensors, using pull-down and pull-up resistors to digitally convert terminal potentials, enabling the detection of various abnormality modes and avoiding false ground abnormality judgments by differential arithmetic calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If offset voltage is applied to negative terminal wiring for abnormality detection, then ground abnormality of negative line can be detected, but sky short circuit abnormality and ground abnormality of positive line cannot be detected
Solution Approach 1:
The patent divides the abnormality detection function into separate detection paths: one for negative terminal abnormalities (using offset voltage) and another for positive terminal abnormalities (using pull-down/pull-up resistors). This segmentation allows each detection method to specialize in detecting specific abnormality types without interference, resolving the contradiction by ensuring comprehensive coverage of all abnormality modes including sky short circuit and positive line ground abnormalities.
Solution Approach 2:
The patent implements preliminary abnormality inspection by temporarily connecting pull-down and pull-up resistors before normal operation. This preliminary action enables the system to detect sky short circuit and ground abnormalities of the positive signal line in advance, complementing the offset voltage method and ensuring complete abnormality judgment without missing any abnormality types.
2Reliability
If pull-down resistor is connected to positive signal line for abnormality detection, then disconnection abnormality can be detected, but sky short circuit abnormality and ground abnormality cannot be discriminated
Solution Approach 1:
The patent introduces temporary pull-up resistors as intermediary elements that work in conjunction with the permanent pull-down resistors. By temporarily connecting pull-up resistors during inspection, the system creates distinct electrical states that enable discrimination between disconnection abnormalities, sky short circuit abnormalities, and ground abnormalities. This intermediary approach resolves the contradiction by providing clear diagnostic differentiation without permanently increasing device complexity.
3Reliability
If offset voltage is applied to negative line, then ground abnormality of negative line can be detected, but false judgment of positive line ground abnormality may occur
Solution Approach 1:
The patent implements a feedback mechanism where the microprocessor monitors the detecting voltage and compares it against expected ranges. When offset voltage is applied to the negative line, the system feedback-checks whether the positive signal line voltage remains within normal parameters. This feedback approach resolves the contradiction by preventing false judgments of positive line ground abnormalities while maintaining accurate detection of negative line ground abnormalities.
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 solution allows for reliable detection of sky short circuit, ground, and disconnection abnormalities, ensuring continuous normal operation and timely maintenance inspection even when ground abnormalities occur, thereby preventing control performance damage.
Implementation Method 1
generates a detecting voltage Vs according to oxygen concentration within exhaust gas
Implementation Method 2
A value provided by adding the above offset voltage is digitally converted and is then inputted to a microprocessor
Data Source
AI summary
Respective positive terminal electric potentials of exhaust gas sensors are sequentially selectively inputted to an analog input terminal of a multi-channel AD converter through a multiplexer. An offset voltage is applied to respective negative terminals of the exhaust gas sensors. This offset voltage is inputted to another input terminal of the multi-channel AD converter. A microprocessor detects a generating voltage of the exhaust gas sensors by the difference between a digital converting value of the positive terminal electric potential and a digital converting value of the negative terminal electric potential. The microprocessor also individually judges that each of the digital converting values is excessively small and excessively large. Thus, the microprocessor judges the existence of ground, sky short circuit and disconnection abnormalities of the negative terminal and the positive terminal.