Position Detector Resin Thickness Design for Injection Molding
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Solution Overview
Problem
Position detector apparatuses face dislocation issues during injection molding, leading to faulty pre-assembly modules and compromised position detection accuracy due to dynamic pressure from melted resin, which can result in exposure and corrosion of Hall IC components.
Innovation Solution
The position detector apparatus features a resin thickness design where the wiring side has a thicker resin mold than the opposite side, with a slope portion connecting the thick and thin molded portions, and a metal mold with large and small capacity cavities to apply pressure and maintain the detector element's intended position, preventing dislocation and exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the detector element, wiring, and terminal are resin-molded together to improve rigidity, then the rigidity of the molded product is improved, but the dynamic pressure of the melted resin may cause dislocation of the detector element during injection molding
Solution Approach 1:
The resin thickness is made non-uniform: thicker on the wiring side and thinner on the detector element side. This local variation in resin thickness allows the melted resin to apply pressure selectively, pushing the detector element against the mold wall to prevent dislocation while maintaining overall structural rigidity.
Solution Approach 2:
The mold design includes a protrusion that preliminarily positions the detector element before resin injection. This preliminary anti-action counteracts the potential dislocation force that will be applied during injection molding, ensuring the detector element remains in its correct position.
2Measurement precision
If a very thin resin wall is molded around the Hall IC to form the first pre-assembly module, then the position accuracy of the Hall IC against the outer wall is guaranteed, but the Hall IC may be dislocated from the intended position during injection molding due to contact with the inner wall of the metal mold
Solution Approach 1:
The resin wall thickness is varied locally: thin on the detector element side to maintain position accuracy and prevent mold contact, and thick on the wiring side to provide structural support and prevent dislocation during injection molding.
Solution Approach 2:
The mold includes a protrusion that preliminarily positions the detector element before resin injection. This preliminary positioning action ensures the Hall IC is correctly placed before the resin is injected, preventing dislocation while maintaining the thin wall design for position accuracy.
3Reliability
If the detector element is dislocated during injection molding, then a faulty pre-assembly module is produced, but water or liquid may intrude through the exposure part to corrode the lead frame and terminal, deteriorating position detection accuracy
Solution Approach 1:
The resin thickness is made thicker on the wiring side to provide better protection against water intrusion and corrosion, while maintaining thinner resin on the detector element side to prevent dislocation and maintain position accuracy.
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
This design effectively prevents dislocation of the detector element during injection molding, enhances position detection accuracy, and prevents water intrusion, ensuring reliable operation of the position detector apparatus.
Implementation Method 1
a dynamic pressure of the melted resin that is injected into the mold during injection molding may be applied to the detector element
Implementation Method 2
a position detector apparatus has dual Hall ICs that function together as a detector element for detecting a magnetic field of a magnet
Data Source
AI summary
A position detector apparatus includes a detector part, wiring, a resin part, a resin body, a terminal, and a lead frame. The resin part has a thickness at a wiring side portion of the detector part that is greater than a thickness on a side opposite to the wiring side portion. Therefore, when injection-molding the resin part, due to a thickness change of the resin part, the detector part is pressed against a metal mold and a position of the detecting part is fixed. Further, the resin body has a thick-resin portion and a thin-resin portion. The thickness of the thin-resin portion allows a predetermined amount of dislocation of the detector part. Therefore, if the detector part is exposed, water is prevented from intruding the lead frame and the terminal.