Electrostatic Capacitance Fluid Level Sensor With Deformable Connecting Terminals
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Solution Overview
Problem
Existing electrostatic capacitance fluid level sensors face challenges in precise detection of subtle changes in fluid levels due to electrode tilt during welding, deformation, and stress concentration, which affect sensitivity and performance, especially when mounted on electrically driven compressors.
Innovation Solution
An electrostatic capacitance fluid level sensor with hermetic terminals and deformable connecting terminals that disperse stress and maintain a fixed positional relationship between electrodes, using insulating spacers and flexible connecting terminals to prevent deformation and ensure consistent sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrodes are made long to increase area for electrostatic capacitance, then sensitivity is improved, but electrode tilt during welding has larger influence on interelectrode distance
Solution Approach 1:
The electrode assembly is divided into three parts: the electrode plate itself, the connecting terminal, and the conductive pin. The connecting terminal acts as a separate flexible element that can deform independently to absorb welding-induced tilts, preventing these tilts from affecting the electrode plate's position and the interelectrode distance.
Solution Approach 2:
The connecting terminal is designed with flexible properties, allowing it to dynamically adjust its position during welding and assembly. This flexibility enables the connecting terminal to absorb tilts and deformations through elastic deformation, maintaining stable electrode positioning despite manufacturing variations.
2Strength
If electrodes are thickened to prevent deformation, then strength is improved, but stress concentrates on welded parts which are relatively weaker
Solution Approach 1:
Different parts of the electrode assembly have different thicknesses and strengths tailored to their specific functions. The electrode plate is thickened to prevent deformation during use, while the connecting terminal is made thinner and more flexible to absorb stress. This local differentiation of properties allows the system to achieve both strength and reliability without stress concentration issues.
3Volume of moving object
If sensor is small-sized to reduce dimensions, then compactness is improved, but interelectrode spacing becomes slenderer and thinner making welding difficult
Solution Approach 1:
The connecting terminal serves as an intermediary element between the electrode plate and the conductive pin. It provides a sufficient welding surface area for reliable joint formation, while the electrode plate itself can be made small for compact sensor design. The connecting terminal acts as a buffer that maintains welding feasibility even when the overall sensor size is reduced.
4Measurement precision
If base is adjusted to proper positional relationship in manufacture, then measurement precision is improved, but increase in internal pressure expands the base changing angle between conductive pins
Solution Approach 1:
The flexible connecting terminal is designed in advance to compensate for future pressure-induced base expansion. When internal pressure increases and the base expands, the connecting terminal deforms elastically to absorb the resulting angular changes between conductive pins, preventing these changes from affecting the electrode positional relationship and maintaining measurement precision.
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 solution allows for easier adjustment and handling of electrode positions, reduces stress concentration, and maintains sensor performance under varying conditions, such as increased pressure in compressor applications, by using flexible and stiff connecting terminals to absorb deformation and maintain interelectrode distance stability.
Implementation Method 1
electrostatic capacitance sensors have been proposed as means for detecting an amount of electrically nonconductive fluid such as oil. This sensor detects the presence of fluid and an amount of the fluid, using changes in electrostatic capacitance between electrodes
Implementation Method 2
at least one of the two connecting terminals is deformable by a weaker force than a force causing the electrodes to deform
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
In an electrostatic capacitance fluid level sensor (1) including fluid level detection electrode plates (7) mounted on conductive pins (6) mounted on a hermetic terminal (2), a fluid level detection part mounted on the hermetic terminal (2) is constituted into a detection unit (3) including two electrodes (7), electrically insulating spacers (8) fixing a positional relationship between the electrodes (7), and at least one connecting terminal (9) configured to connect and fix the detection unit (3) to the conductive pins (6). The connecting terminal (9) is deformable by a weaker force than a force causing the electrodes (7) to deform. As a result, stress applied to the electrodes (7) of the detection unit (3) is dispersed/relaxed. Since the detection unit (3) is further connected and fixed to the hermetic terminal (2) for a motor compressor, a work for mounting the sensor (1) to the hermetic motor compressor can be rendered easier as well as the handling of the sensor (1).