Plastic Magnet Coating for Corrosion Resistance in Liquid Level Sensors
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Solution Overview
Problem
Liquid level detecting devices face accuracy issues in corrosive environments due to the rusting of magnetic particles in plastic magnets, leading to weakened magnetic fields and potential rotation failures.
Innovation Solution
A plastic magnet with a mixed magnetic powder and resin, coated with a plated layer, is embedded in a holder using insert molding, with positioning projections for secure retention, ensuring high corrosion resistance and maintaining magnetic field strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a plastic magnet with magnetic powder and resin is used, then cost is reduced and size is minimized, but corrosion resistance deteriorates causing magnetic field weakening and rotation failure
Solution Approach 1:
The invention uses a composite structure consisting of a plastic magnet (magnetic powder + resin) combined with a metal coating layer. The plastic magnet provides cost-effectiveness and size reduction, while the metal coating layer (such as nickel or chrome plating) provides corrosion resistance. This composite material approach resolves the contradiction by combining materials with complementary properties.
2Ease of manufacture
If a plastic magnet with magnetic powder and resin is used, then cost is reduced and size is minimized, but magnetic field strength deteriorates due to rusting of magnetic particles
Solution Approach 1:
The metal coating layer acts as a protective barrier that prevents rusting of the magnetic particles inside the plastic magnet. By sealing the magnetic powder from moisture and oxygen exposure, the coating maintains the magnetic field strength over time while allowing the use of cost-effective plastic magnet materials.
3Volume of moving object
If a plastic magnet with magnetic powder and resin is used, then size is reduced, but corrosion resistance deteriorates causing rotation failure of the holder
Solution Approach 1:
The small-sized plastic magnet is equipped with a metal coating layer that provides corrosion resistance. This coating prevents rust-induced friction and binding that would cause rotation failure, thereby maintaining reliable holder rotation despite the reduced size and use of plastic materials.
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 provides a liquid level detecting device with enhanced corrosion resistance, preventing magnetic field weakening and rotation failures, thus ensuring high detection accuracy even in corrosive environments.
Implementation Method 1
a Hall element which is provided in the sensor housing and detects a displacement of the magnet of the holder
Implementation Method 2
the coating layer is a plated layer that is formed on the surface of the plastic magnet
Data Source
AI summary
A liquid level detecting device includes a sensor housing, a holder which is held rotatably by the sensor housing, a float arm which is fixed to the holder, a float which is attached to a tip portion of the float arm and varies in position following a surface level of liquid stored in a tank, a magnet provided in the holder, and a Hall element which is provided in the sensor housing and detects a displacement of the magnet of the holder. The magnet is a plastic magnet in which magnetic powder and a resin are mixed. A surface of the plastic magnet is coated by a coating layer.