O2 Sensor Diagnosis Delay for SCR Ammonia Slip Control

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Solution Overview

Problem

Existing exhaust systems with selective catalytic reduction (SCR) units face challenges in maintaining optimal NOx conversion efficiency due to issues like slow reduction reaction rates and ammonia slip, which can occur from either insufficient or excessive ammonia levels, and are further complicated by conditions such as idling or high altitudes leading to false O2 sensor diagnostic errors.

Innovation Solution

An emissions control system that includes an oxidation device, an O2 diagnosis module, and a controller to manage the O2 diagnosis module by detecting high hydrocarbon regions and measuring upstream temperatures, delaying the O2 diagnosis module's operation for a signal rationality delay time when certain conditions are met, such as idling or low fueling rates, to prevent false diagnostic errors and optimize ammonia dosing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the O2 diagnosis module operates continuously to monitor oxidation performance, then diagnostic coverage is improved, but false diagnostic errors occur under high hydrocarbon conditions such as idling or high altitudes

Engineering Contradiction:

Improvediagnostic accuracyVSAvoidfalse diagnostic errors

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system changes the operational state of the O2 diagnosis module based on detected conditions. When high hydrocarbon conditions are detected (through temperature and fueling rate monitoring), the diagnosis module is delayed or inhibited, preventing false diagnostics during problematic operating conditions while maintaining diagnostic functionality during normal conditions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The controller acts as an intermediary between the O2 diagnosis module and the monitoring systems. It receives temperature and fueling rate data, determines whether high hydrocarbon conditions exist, and accordingly controls whether the O2 diagnosis module should operate, thereby mediating between continuous monitoring needs and false error prevention

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If ammonia dosing is increased to improve NOx conversion efficiency, then NOx reduction is improved, but ammonia slip increases causing harmful emissions

Engineering Contradiction:

ImproveNOx conversion efficiencyVSAvoidammonia slip

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The system uses feedback from the O2 diagnosis module and operating condition monitoring to adjust ammonia dosing strategies. By detecting high hydrocarbon conditions and delaying O2 diagnosis, the system prevents false readings that could lead to incorrect ammonia dosing decisions, thereby maintaining optimal dosing levels that maximize NOx conversion while minimizing ammonia slip

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system dynamically adjusts its diagnostic and control behavior based on real-time operating conditions. The O2 diagnosis module is selectively activated or delayed based on temperature and fueling rate conditions, allowing the system to adapt ammonia management strategies to current operating states, optimizing the balance between NOx conversion and ammonia slip prevention

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 NOx conversion efficiency by preventing ammonia slip and reducing false diagnostic signals, thereby improving the overall performance of the SCR system, especially under conditions like idling or high altitudes.

Implementation Method 1

an oxidation device, an O2 diagnosis module for diagnosing the oxidation device

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

The SCR device includes a substrate having an SCR catalyst disposed thereon to reduce the amount of NOx in the exhaust gas

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 3

selective catalytic reduction (SCR) devices. An SCR device includes a substrate having an SCR catalyst disposed thereon to reduce the amount of NOx in the exhaust gas

Methodology Applied

Scientific EffectSelective catalytic reduction:

Data Source

PatentUS10450933B2Downstream oxygen sensor performance for selective catalytic reduction

Publication Date: 2019.10.22 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

Technical solutions are described for an emissions control system for a motor vehicle including an internal combustion engine. An example computer-implemented method for controlling an exhaust system of an internal combustion engine, includes detecting a high hydrocarbon region in the operation of the internal combustion engine. The method further includes responsively, measuring an upstream temperature of an oxidation device of the exhaust system. Further yet, the method includes in response to the upstream temperature being equal to or above a predetermined threshold, delaying an O2 diagnosis of the exhaust system for a signal rationality delay time.