Gas Sensor Offset Current Correction for Reference Gas Contamination
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Solution Overview
Problem
Existing gas sensors face measurement accuracy issues due to contamination of the reference gas, which affects the reference potential and leads to inaccurate measurement of gas components, particularly when exposed to high-temperature exhaust environments.
Innovation Solution
A gas sensor design with an oxygen-ion conductive solid electrolyte sensor element, incorporating internal spaces and electrodes, and a controller that corrects gas component concentration using a correlation between offset current values and measurement pump current fluctuations to maintain accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gas sensor is used in high-temperature exhaust environments, then the sensor can detect gas components in real-time, but contaminated gas is generated due to volatilization of oil content and generation of gas from the rubber plug, which contaminates the reference gas and deteriorates measurement accuracy
Solution Approach 1:
The patent applies preliminary action by introducing a heating device that heats the outer tube before the sensor starts measuring. This pre-heating prevents contaminated gas generation at the source by volatilizing oil content and preventing rubber plug degradation before they can contaminate the reference gas, thereby maintaining measurement accuracy while enabling real-time detection
Solution Approach 2:
The patent converts the harmful effect of high temperature (which causes contamination) into a beneficial pre-heating process. By intentionally heating the outer tube before operation, the harmful volatilization and gas generation from the rubber plug are prevented, transforming the high-temperature environment from a source of contamination to a protective measure that ensures measurement accuracy
2Ease of manufacture
If the reference gas space is sealed with a rubber plug, then the assembly is simplified and sealing is achieved, but gaps between through holes and lead lines allow air to enter and contaminate the reference gas
Solution Approach 1:
The patent introduces an intermediate sealing structure - a sealing ring or O-ring - that fits between the rubber plug and the outer tube. This intermediary component fills the gaps between through holes and lead lines, preventing air leakage and contamination while maintaining the simple rubber plug sealing approach
Solution Approach 2:
The patent segments the sealing function by dividing it into multiple components: the rubber plug provides primary sealing, while additional sealing rings or gaskets provide secondary sealing at critical gaps. This segmentation allows each component to focus on specific sealing tasks, maintaining assembly simplicity while ensuring reference gas purity
3Measurement precision
If the sensor element is heated by a heater to high temperature, then gas detection sensitivity is improved, but contaminated gas is generated from volatilization of oil content and rubber plug, affecting reference potential
Solution Approach 1:
The patent applies preliminary action by implementing a two-stage heating process: first, the outer tube is heated to a moderate temperature to prevent contamination generation; second, the sensor element is heated to high temperature for sensitive detection. This sequential approach prevents contaminated gas generation before it can affect the reference potential, while still achieving high detection sensitivity
Solution Approach 2:
The patent segments the heating function into two independent heating zones: one for the outer tube (to prevent contamination) and another for the sensor element (for sensitive detection). This segmentation allows each zone to be optimized for its specific function, preventing contaminated gas generation while maintaining high detection sensitivity
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 design effectively suppresses the deterioration of measurement accuracy by correcting for contaminated gases, ensuring precise detection of gas components like NOx even in high-temperature exhaust environments.
Implementation Method 1
a sensor element including an elongated planar base part formed of an oxygen-ion conductive solid electrolyte
Implementation Method 2
a measurement pump cell to which a predetermined pump voltage is applied to allow a measurement pump current to flow between the measurement electrode and the out-of-space pump electrode in accordance with a concentration of the predetermined gas component
Implementation Method 3
a porous diffusion resistance layer disposed at a gas inlet to the measurement gas chamber
Data Source
AI summary
A controller of a gas sensor includes: a concentration identification part identifying a concentration of a predetermined gas component based on a measurement pump current flowing between a measurement electrode and an out-of-space pump electrode in accordance with the concentration of the predetermined gas component due to application of a predetermined pump voltage; and a correction processing part correcting the concentration of the predetermined gas component identified by the concentration identification part, the correction processing part corrects the concentration of the predetermined gas component based on a correlation identified in advance between an offset current value as a magnitude of the measurement pump current when a measurement gas not containing the predetermined gas component flows or a normalized value of the offset current value and output fluctuations of the measurement pump current at startup of the gas sensor.