Laser-Welded Rotation Speed Sensor Housing for Waterproofing
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Solution Overview
Problem
Existing rotation speed sensors face challenges in achieving high waterproofing performance without applying pressure or heat loads to substrates or integrated circuits, particularly due to exposed terminal pins and unjoined bus bars, which can lead to liquid intrusion.
Innovation Solution
A rotation speed sensor design featuring a cable with a sheath and a housing configuration where a circuit substrate is held in a first housing and a cable is held in a second housing, with both housings welded together using laser welding, ensuring waterproofing without direct pressure or heat application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If terminal pins are exposed from the resin holder or bus bar is not joined to sensor housing, then ease of connection is improved, but waterproofing performance deteriorates due to liquid intrusion risk
Solution Approach 1:
The patent uses a resin mold (thin film/shell) to seal and protect the terminal pins and bus bar connections. The resin mold covers the exposed terminal pins and fills gaps between components, creating a waterproof barrier while maintaining the electrical connection functionality. This resolves the contradiction by providing both connection ease and waterproof protection.
2Reliability
If resin mold coating is applied to achieve waterproofing, then waterproofing performance is improved, but substrate or IC is damaged due to pressure or heat load during molding
Solution Approach 1:
The patent performs preliminary actions by pre-assembling the terminal pins, bus bar, and sensor housing in their final positions before applying the resin mold. The housing structure is prepared with predefined sealing features and mounting positions, allowing the resin mold to be applied with minimal pressure and heat, thus protecting the substrate and IC from damage while achieving waterproofing.
3Device complexity
If exposed terminal pins or unjoined bus bar are used, then device complexity is reduced, but harmful factors increase due to liquid intrusion
Solution Approach 1:
The resin mold acts as a flexible sealing shell that encapsulates the terminal pins and bus bar connections without adding significant structural complexity. It forms a continuous protective barrier that prevents liquid intrusion while maintaining the simplicity of the overall device structure. The resin mold integrates multiple functions (sealing, protection, insulation) in a single component.
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 achieves high waterproofing performance for rotation speed sensors without applying pressure or heat to substrates or integrated circuits, reducing the risk of liquid intrusion and lowering production costs by eliminating the need for high-cost waterproofing connectors.
Implementation Method 1
a first housing (31), which is configured to hold the circuit substrate (4) therein, and a second housing (32), which is configured to hold the cable (2) therein, with the first housing (31) being welded to the second housing (32), and with the second housing (32) being welded to a surface of the sheath (2a) of the cable (2)
Data Source
AI summary
A rotation speed sensor, configured to detect a rotation speed of a rotating body, is composed of a cable composed of an electric wire including a conductor wire, and a sheath provided over the electric wire, a circuit substrate mounted with an integrated circuit thereon and connected to the conductor wire being exposed from the cable, and a housing including a first housing, which is configured to hold the circuit substrate therein, and a second housing, which is configured to hold the cable therein, with the first housing being welded to the second housing, and with the second housing being welded to a surface of the sheath of the cable.