Gas Sensor Control Apparatus Overvoltage Protection
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Solution Overview
Problem
Existing gas sensor control apparatuses face challenges in preventing overvoltage application to oxygen pump cells, leading to increased costs due to a larger number of parts and complexity.
Innovation Solution
A gas sensor control apparatus with a sensor drive circuit that includes terminal voltage output, anomaly detection, and a controller to compare terminal voltage with threshold values, generating signals for short circuit and overvoltage anomalies, and issuing de-energization commands to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Vp limiter is provided to prevent overvoltage application to the oxygen pump cell, then the reliability of the gas sensor is improved, but the device complexity and number of parts increase
Solution Approach 1:
The patent combines the overvoltage prevention function into the existing sensor drive circuit by utilizing the operational amplifier that is already present for controlling the oxygen pump cell current. The Vp limiter function is integrated by adding voltage comparison logic that shares the existing operational amplifier resource, rather than adding a separate dedicated limiter circuit. This merging approach maintains reliability improvement while minimizing increases in device complexity and part count.
Solution Approach 2:
The operational amplifier in the sensor drive circuit is made multi-functional by having it perform both its original current control function and the additional overvoltage limitation function. The circuit is designed so that the same operational amplifier monitors both the current flow through the oxygen pump cell and the voltage across it, allowing one component to serve multiple protective and control purposes simultaneously.
2Reliability
If the sensor drive circuit is configured to monitor terminal voltage and generate anomaly signals, then the reliability of gas sensor protection is improved, but the device complexity increases
Solution Approach 1:
The sensor drive circuit performs self-diagnosis by monitoring its own terminal voltage conditions. The operational amplifier and associated components that are already necessary for driving the oxygen pump cell also serve to detect voltage anomalies and generate protection signals. This self-service approach allows the circuit to detect wire anomalies and protect the sensor without requiring external monitoring systems, thereby improving reliability while minimizing the increase in overall system complexity.
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
Effectively prevents overvoltage application to oxygen pump cells, reducing the risk of damage and maintaining the integrity of the gas sensor system while minimizing component count and cost.
Implementation Method 1
a gas sensor element including one or a plurality of cells, each of which has a pair of electrodes formed on the surface of an oxygen ion conducting solid electrolyte
Implementation Method 2
each of these gas sensors incorporates a heater for activating the solid electrolyte
Data Source
AI summary
A gas sensor control apparatus (1) includes a gas sensor (8) having an oxygen pump cell (14); a sensor drive circuit (52) which energizes the gas sensor; terminal voltage output means (54) which detects and outputs a terminal voltage of the oxygen pump cell; anomaly detection means (58) which compares the terminal voltage and a first threshold value, and when the terminal voltage exceeds the first threshold value, outputs a short circuit anomaly signal informing of a short circuit; a controller (55) which compares the terminal voltage and a second threshold value less than the first threshold value, and when the terminal voltage exceeds the second threshold value, generates a cell voltage anomaly signal informing of an application of an overvoltage to the oxygen pump cell; and command means (9) which, when receiving the short circuit anomaly signal or cell voltage anomaly signal, outputs a de-energization command.