Short-Circuit Pinpointing Device for Wide-Range Air/Fuel Sensors
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Solution Overview
Problem
Existing methods fail to accurately diagnose short-circuits in wide-range air-fuel sensors due to internal cell bias voltage, battery and ground voltage fluctuations, and large common-mode signals, especially when the sensor is at operating temperature.
Innovation Solution
A short-circuit pinpointing device with a controller and current-sink connected to the sensor terminals, using test-resistors and amplifiers to determine status-values and sensor-status, capable of identifying short-circuits at various terminals while the sensor is at operating temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional diagnostic methods are used to detect short-circuits in air-fuel sensors, then the system can identify potential issues, but the measurement precision deteriorates due to internal cell bias voltage, battery and ground voltage fluctuations, and large common-mode signals
Solution Approach 1:
The patent introduces test resistors as intermediary elements connected between sensor terminals and ground. These test resistors serve as mediators that create measurable test conditions without directly interfering with the sensor operation. By measuring voltage drops across these intermediary test resistors, the system can indirectly detect short-circuit conditions with high precision despite the presence of noise and voltage fluctuations from battery and ground connections.
Solution Approach 2:
The patent changes the electrical parameters of the diagnostic system by introducing known test resistors with specific resistance values. This parameter change allows the creation of controlled test conditions where the expected voltage drop can be calculated and compared against actual measurements. The systematic variation of test conditions (connecting test resistors to different terminals) enables precise identification of short-circuit locations while maintaining immunity to common-mode signals and voltage fluctuations.
2Measurement precision
If the sensor is tested at operating temperature for accurate diagnosis, then the diagnostic accuracy improves, but the device complexity increases due to the need for temperature-controlled testing conditions
Solution Approach 1:
The patent enables the sensor to test itself by incorporating test resistors that can be connected to sensor terminals through switching devices controlled by the same controller that manages sensor operation. The sensor system performs its own diagnostic function without requiring external testing equipment or separate testing systems. The controller alternates between sensor operation mode and diagnostic mode, allowing the sensor to be tested at its operating temperature while maintaining a relatively simple integrated system architecture.
3Measurement precision
If multiple test conditions are applied to identify short-circuit locations, then the pinpointing accuracy improves, but the loss of time increases due to sequential testing requirements
Solution Approach 1:
The patent employs periodic action by rapidly switching test resistors between different sensor terminals in a systematic sequence. The switching devices connect test resistors to different terminals (reference terminal, pump terminal, return terminal, tag terminal) in rapid succession, creating periodic test conditions. This periodic switching allows multiple test points to be evaluated sequentially but quickly, minimizing the total diagnostic time while still achieving accurate short-circuit location identification through pattern recognition of the voltage drop measurements.
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
Enables reliable and accurate pinpointing of short-circuits at any sensor terminal across all operating temperatures, immune to circuit imperfections and component mismatches, ensuring the integrity of the pinpointing function.
Implementation Method 1
The device includes a current-sink selectively connectable to one or more of the sensor terminals. The controller determines a status-value of the sensor terminal based on a voltage drop across the terminal resistance when the current-sink is connected to the sensor terminal.
Data Source
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AI summary
A short-circuit pinpointing device (10) for testing a wide-range air/fuel sensor (12) includes a current-sink (24) and a controller (26). The current-sink (24) is selectively connectable to one or more of sensor-terminals of a wide-range air/fuel sensor (12) that include a reference-terminal (16), a pump-terminal (18), a return-terminal (20), and a tag-terminal (22). The controller (26) is in communication with the current-sink (24) and the sensor-terminals. The controller (26) controls the connection of the current-sink (24) to the one or more sensor-terminals. The controller (26) also determines one or more status-values (28) based on signals present at the sensor-terminals. The controller (26) also determines a sensor-status (30) of the wide-range air/fuel sensor (12) based on the connection of the current-sink (24) and the one or more status-values (28).