Bearing Protective Cover Sensor Holder Injection Molding
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Solution Overview
Problem
The existing protective covers for magnetic encoders in bearing devices suffer from reduced air tightness and strength due to thin division walls, which can lead to charging failures and uneven thickness, affecting the sealing and detection accuracy.
Innovation Solution
A cup-shaped protective cover with a sensor holder part and a division wall that is thinner than the main body, formed by injection molding with a thick part acting as a flow path for the molten resin to prevent charging end welds, and using a main and sub gate injection molding technique to ensure even resin distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the division wall is made thin (0.3 to 0.5 mm) to improve detection accuracy by reducing air gap, then the detection precision improves, but the air tightness and strength of the division wall are reduced
Solution Approach 1:
The patent applies local quality by creating a thick part (1.2 to 3 times thicker than surrounding areas) in the disc-shaped member at the resin flow path location. This local thickening provides structural reinforcement and ensures proper resin charging without affecting the overall thin division wall design needed for detection accuracy.
2Measurement precision
If the division wall is made thin to reduce air gap between magnetic sensor and magnetic encoder, then detection precision improves, but charging failure and uneven thickness occur during injection molding
Solution Approach 1:
The patent applies preliminary action by designing a thick part that acts as a resin flow path before the actual charging process. This pre-designed flow path guides the molten resin to fill the thin division wall area first, ensuring uniform thickness and preventing charging failures during injection molding.
3Device complexity
If main body part and division wall are integrally molded with thin division wall, then device complexity is reduced, but charging end weld is generated on the division wall
Solution Approach 1:
The patent maintains integral molding while preventing charging end welds by creating a local thick part that serves as a resin flow path. This thick part ensures molten resin reaches the division wall area with proper flow control, filling it completely before the charging end, thus preventing weld formation and maintaining air tightness.
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 enhances the air tightness and strength of the division wall, preventing reduction in sealing effectiveness and improving detection accuracy by eliminating charging end welds and ensuring uniform thickness.
Implementation Method 1
the thick part serves as a flow path for a molten resin during injection molding of the disc-shaped member in a bearing device
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
The present invention is intended to provide a protective cover having a reliable sensor holder part that prevents reduction in air tightness and strength of a division wall between a magnetic sensor and a magnetic encoder. A protective cover 1 is press-fitted into an outer ring to seal one axial end portion of a bearing, and has a sensor holder part 3B holding a magnetic sensor A. In the protective cover, a disc-shaped member 3 has a thick part 6 as a flow path for preferentially charging a molten resin into a thin part for forming a division wall B in a cavity of a molding die for use in injection molding between a position corresponding to a gate of the molding die and the division wall.