Bearing Protective Cover Venting for Thin Sensor Separation Walls
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Solution Overview
Problem
The existing protective covers for magnetic encoders in bearing devices suffer from defects such as burning and short shots during injection molding, leading to reduced detection accuracy and strength due to air accumulation in thin separation walls, which lowers the non-defective rate and requires frequent die maintenance.
Innovation Solution
A cup-shaped protective cover with a gas drainage pin mechanism in the injection molding die to discharge air from the separation wall area, preventing burning and short shots by ensuring air is released outside the die, thus maintaining the separation wall's integrity and extending die maintenance intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thickness of the separation wall is reduced to improve magnetic sensor detection accuracy, then detection accuracy is improved, but air accumulation occurs during injection molding causing burning and short shots
Solution Approach 1:
The separation wall is divided into multiple thin layers (first separation wall and second separation wall) with different thicknesses. The first separation wall has thickness of 0.3 to 1.0 mm for detection accuracy, while the second separation wall has thickness of 1.5 to 3.0 mm to prevent air accumulation during injection molding. This segmentation allows each part to fulfill its specific function without compromising the other.
Solution Approach 2:
Different regions of the separation wall structure are assigned different thicknesses based on their functional requirements. The region closer to the magnetic sensor (first separation wall) has thinner thickness for optimal detection accuracy, while the region closer to the injection molding cavity (second separation wall) has thicker thickness to prevent air trapping and burning during the molding process.
2Measurement precision
If the thickness of the separation wall is reduced, then detection accuracy is improved, but the strength and rigidity of the separation wall decrease
Solution Approach 1:
The separation wall is segmented into two parts with different thicknesses. The first separation wall (thinner, 0.3-1.0 mm) provides the necessary proximity for accurate magnetic field detection, while the second separation wall (thicker, 1.5-3.0 mm) provides the required structural strength and rigidity to support the overall structure and resist mechanical loads.
Solution Approach 2:
The separation wall structure functions as a composite system where two different thickness regions work together. The thinner first separation wall optimized for magnetic field penetration and detection accuracy is combined with the thicker second separation wall optimized for mechanical strength and rigidity, achieving both detection precision and structural integrity.
3Reliability
If air is not discharged during injection molding, then burning and short shots occur, but adding gas drainage function increases device complexity
Solution Approach 1:
The gas drainage function is merged with the existing ejector pin structure. The ejector pin is designed with a gas drainage hole through which air can be discharged during injection molding. This integration allows the same component to serve dual functions: ejecting the molded product and draining air during molding, thereby avoiding the need for separate gas drainage mechanisms and reducing overall device complexity.
Solution Approach 2:
The ejector pin is given multi-functionality by incorporating both the ejection function and the gas drainage function. The gas drainage hole in the ejector pin allows it to serve as both an ejection mechanism and an air vent during the injection molding process, eliminating the need for dedicated gas drainage components and simplifying the overall die structure.
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 effectively prevents defects in the separation wall, maintaining the non-defective rate of the protective cover and reducing maintenance needs by ensuring accurate detection and strength without air combustion or residue in the molding die.
Implementation Method 1
a gas drainage pin at a position where the separation wall is molded... air in a cavity of an injection molding die is easily accumulated in the separation wall. If the air is not discharged outside the die, burning or short shot may be caused
Data Source
AI summary
The protective cover having a cup shape is mounted to an outer ring of a bearing so as to seal an inward-side end portion of the bearing. A protective cover includes: a disc part made of a synthetic resin; and a sensor holder part that is made of the synthetic resin and protrudes inward from the disc part. The disc part is provided with a separation wall which separates the magnetic encoder and the magnetic sensor from each other. The separation wall has a surface facing the magnetic encoder and a surface facing the magnetic sensor, and one of the surfaces has a mark of a gas drainage pin of an injection molding die.