Reducing Agent Tank Sensor Layout for Frozen Fill Level Detection
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Solution Overview
Problem
Existing tank systems for liquid urea-water solutions in vehicles face challenges in determining the fill level and state of the reducing agent, particularly at low temperatures, where the solution can freeze, leading to inaccurate measurements and potential depletion of the reserve level, which is critical for exhaust-gas purification.
Innovation Solution
A tank design with a sensor system featuring closely spaced electrical contacts that extend through the tank wall, allowing for conductance measurements to determine the presence and state of the reducing agent, including a heater for managing ice cavities and temperature sensors for distribution analysis, ensuring accurate fill level determination and reserve level monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor is used to determine fill level in the tank, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The sensor is divided into multiple electrical contacts (first electrical contact and second electrical contact) spaced less than 5 cm apart, allowing segmental measurement of the reducing agent properties at different positions within the tank, thereby improving fill level determination accuracy without requiring a single complex sensor
Solution Approach 2:
The patent replaces complex mechanical fill level sensors with a simplified electrical conductance measurement system. By measuring the electrical conductance between multiple contacts through the tank wall, the system determines fill level and state of the reducing agent without mechanical moving parts, reducing device complexity while maintaining measurement precision
2Measurement precision
If electrical contacts are placed closer together (less than 5 cm spacing), then measurement precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a parameter range for contact spacing (less than 5 cm) that balances measurement precision with manufacturing feasibility. This parameter change allows accurate differentiation between liquid and frozen states while accommodating normal manufacturing tolerances, avoiding overly stringent precision requirements
3Reliability
If a heater is added to manage ice cavities, then reliability is improved, but device complexity increases
Solution Approach 1:
The heater is positioned to preemptively prevent ice cavity formation or to rapidly melt existing ice cavities when detected by the sensor system. This preliminary action ensures the reducing agent remains in liquid state for reliable dosing, improving low temperature operation reliability without requiring complex active control systems
Solution Approach 2:
The heater acts as an intermediary element between the tank wall and the reducing agent, providing localized thermal management. This intermediary approach allows reliable operation in cold temperatures by controlling the thermal state of the reducing agent near the sensor and dosing points, without heating the entire tank contents
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
The sensor system provides reliable and accurate fill level and state determination of the reducing agent, reducing errors and ensuring the exhaust-gas treatment system's effectiveness by maintaining the desired purification action even at low temperatures.
Implementation Method 1
The first electrical contact and the second electrical contact communicate in an electrically conductive manner with the interior, extend through the tank wall from the interior to the outer side of the tank wall
Implementation Method 2
A device for delivering and/or dosing liquid reducing agent is then no longer capable of delivering the urea-water solution. Such low temperatures may occur in motor vehicles, in particular as a result of long standstill periods.
Data Source
AI summary
A tank for a reducing agent includes a tank wall having an outer side and an interior at least partially delimited by the tank wall. A sensor is disposed at the tank wall and has a first electrical contact and a second electrical contact. The first electrical contact and the second electrical contact communicate in an electrically conductive manner with the interior, extend through the tank wall from the interior to the outer side of the tank wall and are disposed at a first spacing of less than 5 cm from one another. A motor vehicle having the tank is also provided.