NOx Sensor Purification via Variable Pump Current

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Solution Overview

Problem

NOx sensors in internal combustion engines face reliability issues due to disturbances such as changes in oxygen concentration, moisture, and hydrocarbon entry, leading to control failures and deterioration of the sensor components.

Innovation Solution

A NOx sensor purification program that adjusts the current flowing in the reference pump cell to a higher purification pump current than the reference pump current at predetermined times, maintaining an oxygen concentration higher than the reference concentration to purify the sensor and improve durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the reference pump current is increased to improve tolerance against disturbance, then the reliability of the NOx sensor is improved, but the deterioration of the reference electrode is promoted and the durability of the sensor is reduced

Engineering Contradiction:

Improvereliability of NOx sensorVSAvoiddurability of NOx sensor

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent applies periodic action by implementing a purification procedure that is executed at predetermined intervals (e.g., every 500 hours or 10,000 km). During these periodic purification cycles, the reference pump current is temporarily increased to a purification pump current to remove contaminants from the reference air chamber, while during normal operation between purification cycles, a lower reference pump current is used to minimize electrode deterioration. This periodic high-current purification resolves the contradiction by providing reliability enhancement only when needed rather than continuously.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies dynamics by making the reference pump current adjustable and variable rather than fixed. The control unit dynamically switches between two operational modes: normal operation mode with a lower reference pump current to preserve electrode life, and purification mode with a higher purification pump current to maintain sensor reliability. This dynamic adjustment allows the system to optimize both reliability and durability at different operational phases.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the reference pump current is increased to maintain oxygen concentration in the reference air chamber, then the robustness against disturbance is improved, but the oxygen promotes deterioration of the heater and the sensor element is not sufficiently heated

Engineering Contradiction:

Improverobustness against disturbanceVSAvoidtemperature of sensor element

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent applies periodic action by scheduling purification procedures at predetermined intervals rather than continuously operating at high pump current. This periodic approach allows the heater to receive adequate oxygen supply during normal operation for proper heating, while still achieving purification of the reference air chamber at specific maintenance intervals when the accumulated contaminants reach problematic levels.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies dynamics by dynamically controlling the reference pump current based on operational phase. During normal operation, a lower pump current is used that allows sufficient oxygen to reach the heater for proper heating. During purification cycles, the pump current is temporarily increased to remove contaminants, accepting temporary heating impact but restoring optimal conditions afterward. This dynamic control resolves the contradiction between robustness and temperature maintenance.

Inventive Principle:

Principle #15Dynamics

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

This approach enhances the robustness and reliability of the NOx sensor against disturbances without compromising its durability, maintaining the sensor in an excellent state for normal use.

Implementation Method 1

a sensor element configured by an oxygen ion-conductive solid electrolyte layer such as zirconia

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Implementation Method 2

a reference pump cell configured to maintain an oxygen concentration inside the reference air chamber to the reference oxygen concentration from the reference electrode and a pump electrode

Methodology Applied

Scientific EffectElectrochemical pumping: Pump

Implementation Method 3

an oxygen ion-conductive solid electrolyte layer such as zirconia

Methodology Applied

Scientific EffectOxygen ion conduction: Conduction (electrical)

Data Source

PatentUS10774707B2NOx sensor purification program, internal combustion engine, and NOx sensor purification method

Publication Date: 2020.09.15 ISUZU MOTORS LTD

AI summary

A non-transitory computer-readable medium having a NOx sensor purification instructions for a NOx sensor causes: an on-vehicle electronic computer mounted in the vehicle, when it comes to a predetermined purification time, to execute a start procedure to send a start command to perform a purification control to the control unit; and control unit, in response to the start command, to execute a purification procedure to perform the purification control which causes the current flowing in the reference pump cell from the reference pump current to be a purification pump current, which is set to a current value larger than the reference pump current.