Conductive Plastic Capacitive Tank Level Sensing
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Solution Overview
Problem
Existing operating fluid tanks, such as fuel and urea tanks, face challenges with large space requirements and interference issues due to mechanical lever indicators, especially when handling aqueous solutions that can freeze and damage components.
Innovation Solution
An operating fluid tank equipped with a capacitive level detection system featuring electrodes made of electrically conductive plastic materials, where the di-electric constant is determined to accurately measure the fill level and physical state of the fluid, allowing for reduced interference and increased manufacturing simplicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical lever indicators are used to determine fill level, then the fill level can be determined mechanically, but the device requires large space and is prone to interference and damage
Solution Approach 1:
The patent replaces mechanical lever indicators with a capacitive sensor system that uses electrical fields to detect fill level. The capacitive sensor comprises a sensor electrode and reference electrode that measure capacitance changes caused by the dielectric properties of the operating fluid, eliminating moving mechanical parts that require space and are vulnerable to damage from frozen fluid.
Solution Approach 2:
The patent utilizes changes in dielectric constant (permittivity) of the operating fluid to determine fill level. As the fluid level changes, the capacitance between electrodes changes due to the different dielectric properties of the fluid versus air/vapor space, providing a non-mechanical means of measurement that is insensitive to physical interference.
2Measurement precision
If conventional electrodes are used in capacitive sensors, then fill level can be measured contactlessly, but manufacturing complexity increases and reliability decreases
Solution Approach 1:
The patent employs electrodes made from electrically conductive plastic materials, which combine the electrical conductivity needed for sensing with the chemical resistance and manufacturability of plastic. This composite approach allows the electrodes to be manufactured using injection molding or extrusion processes integrated with the tank production, eliminating separate electrode installation steps and improving reliability.
Solution Approach 2:
The patent integrates the capacitive sensor electrodes directly into the tank wall structure during the molding process. The sensor electrode and reference electrode are formed as integral parts of the tank, merging the sensing function with the structural component, which simplifies manufacturing and ensures proper sealing and positioning.
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 capacitive system provides improved accuracy and long-term stability in determining the fill level and fluid properties, with reduced risk of interference and easier manufacturing, as the electrodes are less prone to damage and can be produced alongside the tank wall.
Implementation Method 1
an operating fluid tank (1) with a capacitor (9) having a first electrode (10) and a second electrode (20), wherein a clearance (30) is formed between the first electrode (10) and the second electrode (20) which is fluid-connected to an operating fluid tank interior (2)
Implementation Method 2
The di-electric constant between the electrodes of the capacitor can be determined by determining the capacity of the capacitor based on the well-known geometry of the capacitor
Data Source
AI summary
An operating fluid tank includes a capacitor. The capacitor includes a first electrode and a second electrode. Between the first electrode and the second electrode, a clearance is formed which is fluid-connected to an operating fluid tank interior. The fluid tank also includes an evaluator electrically connected to the capacitor for determining a capacity of the capacitor by means of measurement signals determined by the capacitor. The first electrode and the second electrode include an electrically conductive plastic material.