Gas Sensor Deterioration Judgment via Oxygen Partial Pressure Control

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Solution Overview

Problem

Conventional methods fail to detect deteriorated states in gas sensors, as the values of currents, voltages, and impedances of deteriorated sensors remain within normal ranges, making it difficult to differentiate between normal and deteriorated states, which can lead to reduced gas detection accuracy.

Innovation Solution

A sensor deterioration judging apparatus and method that includes a first and second oxygen ion pump cell, a reference oxygen chamber, and an oxygen partial pressure detection cell, with a pump current detecting unit, status judging unit, pump stopping unit, and deterioration judging unit to determine the oxygen partial pressure and assess the state of the gas sensor by comparing it to preset reference values.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional methods measure currents, voltages, and impedances to detect sensor failure, then fatal failure states can be detected, but deteriorated states with reduced sensitivity cannot be differentiated from normal states

Engineering Contradiction:

Improvesensor state detection precisionVSAvoiddifficulty in discriminating deteriorated state

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The system performs preliminary oxygen pumping through the first oxygen ion pump cell to establish a known reference oxygen partial pressure in the first measurement chamber before conducting the actual sensor deterioration detection. This preliminary action creates a controlled initial state that enables subsequent accurate measurement and comparison.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces a second measurement chamber and first measurement chamber as intermediary spaces between the sensor elements and the gas sample. These chambers allow for controlled oxygen partial pressure establishment and measurement, serving as mediators that enable precise detection of sensor deterioration by comparing expected versus actual oxygen partial pressures.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a gas sensor operates in a deteriorated state, then it continues to function, but gas detection accuracy is reduced

Engineering Contradiction:

Improvesensor operational reliabilityVSAvoidgas detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The system continuously monitors the oxygen partial pressure in the second measurement chamber and compares it against expected values based on the known first measurement chamber conditions. This feedback mechanism enables real-time detection of sensor deterioration, allowing the system to identify when detection accuracy is compromised while the sensor remains operational.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the operational parameters by stopping the oxygen pumping through the first oxygen ion pump cell at specific intervals and measuring the resulting oxygen partial pressure changes. By varying the pumping state and measuring the system's response, the method can detect subtle deteriorations in sensor performance that would not be apparent under constant operating conditions.

Inventive Principle:

Principle #35Parameter changes

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

Accurately judges the deteriorated state of the gas sensor by stopping oxygen pumping and measuring the resulting oxygen partial pressure, allowing for precise differentiation between normal and deteriorated states, thereby enhancing gas detection accuracy.

Implementation Method 1

a first oxygen ion pump cell having a first oxygen ion conductor and first and second electrodes provided on the first oxygen ion conductor wherein the first electrode is arranged in the first measurement chamber which pumps oxygen into or out of the gas that has been introduced into the first measurement chamber to be measured

Methodology Applied

Scientific EffectIon pumping:

Implementation Method 2

a first oxygen ion pump cell having a first oxygen ion conductor and first and second electrodes provided on the first oxygen ion conductor

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 3

a first measurement chamber into which a gas to be measured is introduced through a first diffusion resistor portion

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS8187436B2Sensor deterioration judging apparatus and sensor deterioration judging method

Publication Date: 2012.05.29 NITERRA CO LTD

AI summary

A gas sensor controller 190 stops an operation of pumping in or out oxygen that is being performed by a first pump cell 111 in a state that the oxygen concentration (oxygen partial pressure) of a gas to be measured is equal to a status judgment reference value (20%). The gas sensor controller 190 calculates an oxygen pressure in a second measurement chamber 161 on the basis of a second pump current Ip2. If the oxygen pressure in the second measurement chamber 161 is equal to a deterioration judgment reference value, the gas sensor controller 190 judges that the second pump cell 113 is in a normal state. If the oxygen pressure in the second measurement chamber 161 is different from the deterioration judgment reference value, the gas sensor controller 190 judges that the second pump cell 113 is in a deteriorated state.