Urea SCR Diagnostic Device for Clogging Detection
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Solution Overview
Problem
Current urea SCR systems lack effective means to detect clogging or sticking issues in the dosing valve and pressurized urea water feed line, and inaccurately measure urea water consumption due to the stepwise detection of urea water levels, especially when the vehicle inclines or urea water fluctuates.
Innovation Solution
A urea water consumption diagnostic device that calculates cumulative consumption volumes and compares them to instructed spray volumes, using a urea water sensor to detect abnormalities such as clogging or continuous spraying, with a determination volume set between several liters and nineteen liters to ensure accurate detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional urea water sensor with stepwise detection is used to detect urea level changes, then the device complexity is low, but the measurement precision of urea water consumption is insufficient
Solution Approach 1:
The detection process is segmented into multiple measurement points (initial level S0, intermediate levels S1, S2, ..., final level Sn) taken at different key switch cycles. This segmentation allows cumulative consumption calculation by summing individual consumption amounts, thereby improving measurement precision without requiring a single complex high-precision sensor
Solution Approach 2:
The initial urea water level S0 is detected and stored in advance at the start of the diagnostic period (when key switch is first turned on). This preliminary measurement establishes a baseline against which subsequent levels are compared, enabling accurate calculation of cumulative consumption over multiple key switch cycles
2Reliability
If urea water level detection is performed only at key switch cycles, then the ease of operation is improved, but the reliability of detecting small consumption amounts is reduced
Solution Approach 1:
The diagnostic system continuously accumulates urea water consumption data across multiple key switch cycles rather than making a single judgment. By continuously adding instructed spray volumes and comparing cumulative consumption against cumulative instructions, the system maintains reliable detection capability even when individual measurement intervals are long
Solution Approach 2:
The system performs more measurements than strictly necessary by detecting levels at every key switch cycle and accumulating data over multiple cycles. This excessive measurement approach ensures that even small consumption amounts or abnormal patterns (like clogging) are reliably detected through cumulative analysis
3Reliability
If the dosing valve is controlled to spray urea water based on NOx sensor feedback, then the productivity of NOx reduction is improved, but the ability to detect valve clogging or sticking is reduced
Solution Approach 1:
The system implements a feedback mechanism by comparing the cumulative instructed spray volume (from DCU control based on NOx levels) with the cumulative actual consumption volume (from sensor measurements). This feedback loop enables detection of abnormalities such as clogging or sticking when the instructed and actual volumes diverge significantly, while maintaining normal NOx reduction productivity through the original DCU control logic
Data Source
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AI summary
Provided is a urea water consumption diagnostic device for urea SCR, capable of detecting if a pressurized fluid feed line or a dosing valve has been clogged or stuck with a foreign matter, or if the urea water has been left to continue spraying from the dosing valve. The urea water consumption diagnostic device for urea SCR includes a urea water sensor (22) that detects a level of the urea water (U) in a urea water tank (15), spray volume instruction means (30) that instructs a volume of urea water to be sprayed from the dosing valve (12) in accordance with NOx in an exhaust gas, instructed spray volume addition means (31) that adds up the instructed spray volumes instructed by the spray volume instruction means (30), consumption volume calculation means (32) that calculates a cumulative consumption volume (D) from a detection value input from the urea water sensor (22), and abnormality diagnostic means (33) that compares a cumulative instructed spray volume (P) from the instructed spray volume addition means (31) to the cumulative consumption volume (D) from the consumption volume calculation means (32) and determines whether the urea water spraying by the dosing valve (12) is normal or abnormal.