Integrated Sensor Arrangement for Tank Fill Level and Temperature
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Solution Overview
Problem
Existing sensor arrangements for vehicles with internal combustion engines, particularly those using selective catalytic reduction systems, face challenges in compactly and reliably measuring multiple variables like temperature and filling levels in reducing agent tanks, especially when exposed to chemically aggressive substances like aqueous urea solutions, which can lead to malfunctions and corrosion.
Innovation Solution
A compact multi-sensor arrangement is proposed, where the temperature sensor is integrated within a tubular area inside the carrier, and the measuring electrodes are protected by a carrier with a primary and secondary encapsulation, ensuring resistance to chemical influences and prompt temperature fluctuation detection, utilizing a two-stage manufacturing process with good thermal conductivity and sealing to prevent liquid exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple sensors are arranged separately in the reducing agent tank, then each sensor can perform its measurement function, but the device complexity increases and the chemical resistance is compromised due to multiple exposure points
Solution Approach 1:
The patent combines multiple sensors (filling level sensor with measuring electrodes and temperature sensor) into a single integrated sensor arrangement. The measuring electrodes and temperature sensor are arranged in close proximity within a unified structure that is collectively encapsulated, reducing the number of separate components exposed to the chemically aggressive reducing agent and simplifying the overall device complexity.
Solution Approach 2:
The sensor arrangement serves multiple functions simultaneously: it measures both the filling level (via measuring electrodes detecting liquid contact) and the temperature (via the temperature sensor) of the reducing agent. This multi-functional design eliminates the need for separate sensor systems, thereby reducing complexity while maintaining comprehensive monitoring capability.
2Measurement precision
If the temperature sensor is exposed directly to the reducing agent for accurate temperature measurement, then temperature detection precision is improved, but the reliability decreases due to chemical corrosion and malfunctions
Solution Approach 1:
The patent introduces an encapsulation material as an intermediary between the temperature sensor and the reducing agent. This encapsulation allows thermal energy to pass through (maintaining temperature measurement accuracy) while providing a protective barrier that prevents direct chemical contact between the reducing agent and the sensor components, thereby ensuring long-term reliability.
Solution Approach 2:
The encapsulation is implemented as a thin-walled structure that is sufficiently transparent to thermal conduction for accurate temperature sensing, yet provides adequate chemical protection. The thin-walled encapsulation allows the temperature sensor to respond promptly to temperature fluctuations in the reducing agent while maintaining reliability through chemical resistance.
3Reliability
If the sensor components are protected with thick encapsulation for chemical resistance, then reliability is improved, but the response time to temperature fluctuations increases
Solution Approach 1:
The encapsulation is designed with thin walls that provide sufficient chemical protection while minimizing thermal resistance. This thin-walled structure allows thermal energy to conduct through rapidly, ensuring the temperature sensor responds promptly to temperature fluctuations in the reducing agent, while still maintaining adequate reliability through chemical resistance.
Solution Approach 2:
The encapsulation material and thickness are optimized to achieve the right balance between chemical protection and thermal conduction. By carefully selecting the material properties and thickness parameters, the design ensures both chemical resistance and rapid temperature response without requiring thick encapsulation.
4Ease of operation
If measuring electrodes are exposed to detect filling level, then measurement function is achieved, but corrosion and malfunctions occur due to direct contact with aggressive reducing agent
Solution Approach 1:
The encapsulation material serves as an intermediary that allows the measuring electrodes to detect the filling level (by detecting changes in electrical properties when liquid contacts the electrodes) while protecting the electrodes from direct chemical corrosion. The encapsulation maintains the electrodes' functionality while ensuring their long-term durability in the chemically aggressive environment.
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 solution provides a reliable, compact, and chemically resistant sensor arrangement capable of accurately measuring filling levels and temperatures, preventing malfunctions and corrosion, thus ensuring safe and efficient operation of reducing agent tanks.
Implementation Method 1
the temperature sensor is integrated within a tubular area inside the carrier... can also react promptly to temperature fluctuations in the tank
Implementation Method 2
measuring electrodes of different lengths injected into plastic... for the measuring electrodes for filling level
Data Source
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AI summary
The invention relates to a sensor arrangement for determining a tank fill level of a liquid (7), especially a reducing agent for removing nitrogen from the exhaust gases of an internal combustion engine, which liquid is contained in a tank (5), at least two electrically conductive measuring electrodes (14, 16) being at least partially embedded in a carrier (8, 32) that is produced of an electrically non-conductive material. The sensor arrangement comprises a temperature sensor (44), especially a resistor (74) with negative temperature coefficient being used as a temperature sensor, which is integrated into the carrier.