Sensor Unit Gate Positioning to Prevent Weld Lines
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Solution Overview
Problem
Existing sensor units face issues with resin flow and weld line formation during molding, leading to inadequate resin supply and potential corrosion or insulation problems when exposed to road de-icing agents, particularly when used in vehicle wheel applications.
Innovation Solution
The sensor unit design includes a resin casing with a charging position deviated from the central axis, utilizing a main and auxiliary casing with specific thickness and through-bore configurations to control resin flow and prevent weld lines, ensuring a sufficient resin supply to the sensing surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the gate is formed in a position remote from the sensing surface, then the molding process is simplified, but the resin may not flow sufficiently into the sensing surface area, causing short shot or weld line formation
Solution Approach 1:
The gate is positioned asymmetrically at a corner of the sensing surface rather than at the center or remote position. This asymmetric placement allows the resin to flow along the diagonal from the corner gate through the entire sensing surface area, ensuring complete filling without forming weld lines while maintaining manufacturing simplicity.
2Quantity of substance
If the gate is positioned to allow resin flow into the sensing surface from all directions, then the sensing surface can be fully filled, but weld lines are formed where resin streams converge and solidify
Solution Approach 1:
Instead of allowing resin to flow from multiple directions in a two-dimensional plane (which causes weld lines at convergence points), the gate is positioned at a corner to create a unidirectional flow path that utilizes the diagonal dimension of the sensing surface. This eliminates weld line formation while ensuring complete resin coverage of the sensing surface area.
3Measurement precision
If the sensing surface thickness is reduced to enhance detecting sensibility, then the detection accuracy improves, but the resin may crack when exposed to de-icing agents like calcium chloride
Solution Approach 1:
The gate positioning is optimized to control the resin flow pattern and distribution within the sensing surface. By placing the gate at the corner, the resin flows more uniformly through the sensing surface thickness, reducing internal stress concentrations and improving the resin's resistance to cracking from de-icing agent exposure, while maintaining the thin profile needed for detection sensitivity.
Data Source
AI summary
A sensor unit with a sensing surface molded properly on an outer surface of a sensor receiving part is provided. The sensor unit includes a resin casing formed with an annular fixing member, and a sensor receiving part formed in the casing for receiving a sensor housed. A sensing surface that faces a target object is formed within the sensor receiving part. A resin charging position in molding the casing is set to a position deviated circumferentially from a central position in a width of the sensing surface. In particular, resin is charged into the fixing member from a gate arranged on an extending line of a first through-bore formed in a position corresponding to the charging position.