Urea Water Temperature Sensor Diagnosis Preventing Misdiagnosis
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Solution Overview
Problem
Conventional competence diagnosis systems for urea water temperature sensors misdiagnose failures when urea water is replenished, leading to incorrect identification of sensor failures due to temperature differences between the urea water and ambient temperatures.
Innovation Solution
Incorporating a urea water level condition determination unit that stores the urea water level before key-off and compares it with the current level after key-on to determine if the level difference is within a predetermined threshold, allowing temperature comparison only when the level difference is minimal, thereby preventing misdiagnosis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature comparison diagnosis is performed immediately after engine starting, then sensor failure can be detected, but misdiagnosis occurs when urea water is replenished with temperature differences
Solution Approach 1:
The system performs preliminary action by storing the urea water level immediately before key-off in a storage unit. This preliminary storage of level data enables subsequent comparison with current level after key-on, allowing the system to determine whether replenishment has occurred before performing temperature comparison diagnosis, thus preventing misdiagnosis
Solution Approach 2:
The urea water level serves as an intermediary indicator to determine the appropriateness of performing temperature comparison diagnosis. By using level changes as a mediating condition, the system decides whether to allow temperature-based failure detection, thereby preventing false positives when replenished urea water with different temperatures is introduced
2Ease of manufacture
If ambient temperature is used for comparison without direct measurement, then cost is reduced, but diagnosis accuracy decreases due to temperature differences
Solution Approach 1:
The urea water level acts as an intermediary condition that gates the temperature comparison process. By checking level stability first, the system ensures that temperature comparisons are only performed when urea water has not been replenished, maintaining diagnosis accuracy while continuing to use the cost-effective approach of comparing with ambient temperature rather than direct urea water temperature measurement
Data Source
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AI summary
Provided is a competence diagnosis system for a urea water temperature sensor that can prevent a misdiagnosis when urea water is replenished in a urea tank. A competence diagnosis system for a urea water temperature sensor 129 includes a competence diagnosis unit 127 that diagnoses a failure of a temperature sensor 121 provided in a urea tank 105 by comparing a urea water temperature measured by the temperature sensor 121 with an ambient temperature. The competence diagnosis system for a urea water temperature sensor 129 includes a urea water level condition determination unit 128 that stores a urea water level, which is measured by a level sensor 120 provided in the urea tank 105, in a storage unit 130 immediately before key-off, obtains a level difference between the urea water level stored in the storage unit 130 and a current urea water level after key-on, and allows a diagnosis by the competence diagnosis unit 127 through temperature comparison when the level difference is less than or equal to a predetermined threshold value.