DEF Flow Channel Sensor Layout to Prevent Ammonia Permeation

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Solution Overview

Problem

DEF quality sensors (DQS) in diesel engine work machines fail due to ammonia permeation caused by prolonged immersion in DEF and high temperatures, leading to short-circuit failures.

Innovation Solution

A flow channel system with a DQS positioned to contact DEF during filling, utilizing a U-shaped section or bypass reservoir to minimize immersion time and temperature exposure, allowing quality checks outside the DEF tank.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the DQS is mounted in the DEF tank to continuously monitor quality, then the quality checking capability is improved, but the sensor reliability deteriorates due to prolonged immersion and ammonia permeation

Engineering Contradiction:

ImproveDEF quality checking capabilityVSAvoidsensor reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The DQS is extracted from the DEF tank environment and relocated to the flow channel. This allows the sensor to perform quality checking on DEF during the filling process without being continuously immersed in the tank, thereby eliminating the root cause of ammonia permeation and short-circuit failures while preserving the quality monitoring function

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The quality checking is performed preliminarily during the DEF filling process before the fluid enters the tank. By checking the quality at this earlier stage in the flow channel, the system achieves quality monitoring without requiring continuous sensor immersion in the tank environment

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the DQS is positioned in the flow channel to reduce immersion time, then the sensor reliability is improved, but the quality checking accuracy may deteriorate due to reduced contact time

Engineering Contradiction:

Improvesensor reliabilityVSAvoidquality checking accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The sensor is exposed to DEF for a partial duration - specifically during the filling process - which is sufficient to perform quality checking without requiring continuous immersion. This partial exposure provides adequate contact time for accurate measurement while significantly reducing overall immersion time to prevent ammonia permeation

Inventive Principle:

Principle #16Partial or excessive action

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

Reduces the likelihood of DQS failure by minimizing ammonia permeation, ensuring accurate and reliable DEF quality assessment with reduced sensor exposure.

Implementation Method 1

DEF breaks down into ammonia in the tank which then permeates into the sensing element causing short-circuit failures

Methodology Applied

Scientific EffectPermeation: Permeation

Data Source

PatentUS12467395B2Onboard device and method for checking diesel exhaust fluid quality

Publication Date: 2025.11.11 PERKINS ENGINES

AI summary

The present invention pertains an onboard device for checking the quality of DEF in a work machine, comprising a flow channel configured to fluidly connect a DEF inlet with a DEF tank. The flow channel comprises a DQS configured to be brought into contact with DEF passing through the flow channel. The present invention also pertains to a method of checking the quality of DEF comprising the steps of tilling DEF into a flow channel configured to fluidly connect a DEF inlet with a DEF tank; and checking, by means of a DQS, the quality of the DEF in the flow channel.