Rubber-Molded Rotation Sensor Waterproofing and Durability
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Solution Overview
Problem
Conventional rotation detecting devices, such as ABS sensors, face issues with adhesion between covering materials and component parts, thermal expansion differences, external force susceptibility, lack of vibration absorption, and limited production yield due to injection molding limitations, leading to poor waterproofing and durability.
Innovation Solution
A rotation detecting device utilizing a magnetic sensor and peripheral components molded with a thermoplastic elastomer or rubber-like material for improved adhesion, thermal expansion absorption, and enhanced durability, along with a metallic fixture and cable clamp for secure sealing and reduced manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional injection molding is used to manufacture the sensor unit, then the manufacturing process is simple, but the adhesion between covering material and component parts is poor and waterproofing is compromised
Solution Approach 1:
The patent changes the material parameter from conventional resin to rubber material, which fundamentally alters the molding parameters including temperature, pressure, and curing conditions. This material substitution enables both good adhesion to metal components and excellent waterproofing while maintaining manufacturing simplicity through rubber injection molding processes.
Solution Approach 2:
The patent employs composite material construction by combining rubber covering material with metal component parts (sensor holder, magnet body, metallic parts). The rubber material serves as both structural component and sealing medium, creating a composite assembly that achieves superior adhesion and waterproofing compared to homogeneous resin molding.
2Ease of manufacture
If resinous covering material is used, then the molding process is straightforward, but thermal expansion differences cause gaps between covering material and component parts
Solution Approach 1:
The patent changes the material from resin to rubber, which has superior thermal expansion characteristics that better match the metal component parts. The rubber material's elastic modulus and thermal expansion coefficient are optimized to minimize gap formation during temperature variations, while maintaining ease of molding through standard rubber injection processes.
3Device complexity
If resinous covering material is used, then the structure is simple, but external forces cause plastic deformation and gaps leading to poor waterproofing
Solution Approach 1:
The patent changes the material parameter from resin to rubber, which fundamentally alters the mechanical response to external forces. Rubber material exhibits elastic deformation rather than plastic deformation, allowing it to recover its shape and maintain sealing contact after external forces are applied, thereby preserving waterproofing without increasing structural complexity.
Solution Approach 2:
The rubber covering material acts as a cushioning element that absorbs and distributes external forces before they reach the internal component parts. This beforehand cushioning effect prevents direct force transmission that would cause gap formation and waterproofing failure, while maintaining the simple overall structure of the sensor unit.
4Ease of manufacture
If resinous covering material is used, then the molding process is conventional, but vibration absorption capability is lacking reducing durability
Solution Approach 1:
The patent changes the material from resin to rubber, which fundamentally alters the damping characteristics. Rubber material has superior vibration absorption capability due to its viscoelastic properties, allowing it to dissipate vibrational energy while maintaining the conventional injection molding process for manufacturing.
5Ease of manufacture
If conventional injection molding is used, then the process is standard, but the number of pieces molded at one time is limited reducing productivity
Solution Approach 1:
The patent employs multi-cavity or stacked mold designs for rubber injection molding, which segment the molding space into multiple independent cavities. This allows simultaneous production of multiple sensor units in one molding cycle, significantly increasing productivity while maintaining the standardization and simplicity of the rubber injection molding process.
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 excellent waterproofing, increased durability against vibrations and external forces, and reduced manufacturing costs by allowing for a higher yield of rotation detecting devices per molding cycle.
Implementation Method 1
a gap tends to occur between the covering material and the built-in component parts due to the difference in thermal expansion thereof
Implementation Method 2
the magnetic sensor and the peripheral component parts are molded together so as to be covered by a thermoplastic elastomer or a material capable of exhibiting a rubber elasticity
Implementation Method 3
The covering material comprised of the resinous material lacks a vibration absorbing capability and, therefore, there is a problem in durability relative to external vibrations
Implementation Method 4
a magnetic sensor arranged in face-to-face relation with a magnet body or a metallic body
Data Source
AI summary
A sensor assembly is sandwiched together with a rubber material mixed with a vulcanizing agent in a mold assembly including an upper mold and a lower mold. The upper and lower molds, while completely sandwiching the sensor assembly, are heated for a predetermined length of time, and a pressure is then applied to the sensor assembly to complete a compressive molding.