Exhaust Gas Sensor Deterioration Detection via Thermal Control

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Solution Overview

Problem

Existing exhaust gas sensors face challenges in accurately determining sensor cell deterioration due to capacitive discharge when voltage is changed, leading to prolonged determination times and potential changes in exhaust gas concentrations, which can lower measurement accuracy.

Innovation Solution

A control apparatus that uses a heater to change the temperature of the pump cell, thereby altering the oxygen flow to the sensor cell, allowing for quicker and more accurate deterioration determination by suppressing capacitive discharge and maintaining constant output current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If voltage applied to the pump cell is changed for deterioration determination, then the amount of oxygen flowing through the pump cell changes, but capacitive discharge causes output current fluctuation and prolongs determination time

Engineering Contradiction:

Improvedeterioration determination accuracyVSAvoiddeterioration determination time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent introduces a heater as an intermediary device to indirectly control the oxygen flow through the pump cell by temperature adjustment, rather than directly changing the voltage. This mediator approach avoids the capacitive discharge issue while still achieving the desired change in oxygen permeability for deterioration determination

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the electrical control method (voltage change) with a thermal control method (temperature change via heater). By substituting the electrical field approach with a thermal field approach, the capacitive discharge problem is eliminated while maintaining the ability to control oxygen flow through the pump cell

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If deterioration determination takes a long time, then capacitive discharge effects subside, but exhaust gas concentrations may change, lowering measurement accuracy

Engineering Contradiction:

Improvedeterioration determination reliabilityVSAvoidexhaust gas concentration measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The heater serves as an intermediary that enables rapid deterioration determination through thermal control, completing the process before exhaust gas concentrations have time to change significantly. This resolves the conflict between needing sufficient determination time for reliability and maintaining measurement accuracy

Inventive Principle:

Principle #24Intermediary (Mediator)

3Quantity of substance

If voltage is temporarily lowered to increase oxygen flow for deterioration determination, then sensor cell output current increases, but capacitive discharge causes current fluctuation requiring longer settling time

Engineering Contradiction:

Improveoxygen flow amountVSAvoidcurrent settling time

Core Design Contradiction:

Quantity of substanceVSDuration of action of moving object

Solution Approach 1:

The patent substitutes electrical voltage control with thermal control using a heater. By controlling the pump cell temperature rather than applying voltage changes, the system achieves increased oxygen flow without triggering capacitive discharge, thereby eliminating the current fluctuation and extending settling time

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution enables rapid and accurate determination of sensor cell deterioration without affecting exhaust gas concentrations, improving measurement precision and reducing the time required for assessments.

Implementation Method 1

a heater (180) configured to heat both the pump cell (150) and the sensor cell (160)

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

a pump cell (150) configured to remove oxygen from exhaust gas of an internal combustion engine

Methodology Applied

Scientific EffectElectrochemical reaction: Electrolysis

Implementation Method 3

a sensor cell (160) configured to output electric current depending on the concentration of a measurement target component in the exhaust gas from which oxygen has been removed by the pump cell (150)

Methodology Applied

Scientific EffectElectrochemical reaction: Electrolysis

Data Source

PatentUS10731588B2Control apparatus for exhaust gas sensor

Publication Date: 2020.08.04 DENSO CORP

AI summary

A control apparatus is provided for controlling an exhaust gas sensor. The exhaust gas sensor includes a first cell, a second cell configured to output electric current depending on the concentration of a measurement target component in exhaust gas from which oxygen has been removed by the first cell, and a heater configured to heat the first and second cells. The control apparatus includes a heater controlling unit, a current detecting unit configured to detect the electric current outputted from the second cell, and a deterioration determining unit. The deterioration determining unit causes the heater controlling unit to change output of the heater and thereby changes the temperature of the first cell. During the change in the output of the heater, the deterioration determining unit determines, based on an amount of change in the electric current detected by the current detecting unit, whether or not the second cell is deteriorated.