Sensor Magnet Holder Snap-Fit Assembly for Motor Shafts
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Solution Overview
Problem
Existing motor designs face challenges in firmly mounting sensor magnets on motor shafts without requiring preliminary machining, such as knurling and grooving, which can lead to sensor magnet cracking and grease oozing issues when adjacent to worm gears.
Innovation Solution
A sensor magnet holder with a cylindrical portion, flange, and snap-fit tongues is used, allowing for a press-fit assembly that eliminates the need for conventional fixation methods, providing a secure axial and rotational positioning without applying excessive force and preventing grease oozing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional fixation methods (knurling and grooving) are used to mount sensor magnets on motor shafts, then the sensor magnets can be firmly fixed, but the sensor magnets may crack and grease may ooze towards Hall sensor boards
Solution Approach 1:
A sensor magnet holder is introduced as an intermediary component between the motor shaft and the sensor magnet. The holder has a press fit portion that mounts to the motor shaft and engagement portions that secure the sensor magnet, eliminating the need for direct knurling or grooving of the shaft. This intermediary structure prevents cracking and grease oozing while providing firm fixation.
Solution Approach 2:
The fixation system is segmented into separate functional components: the sensor magnet holder (with press fit portion and engagement portions) and the sensor magnet itself. This segmentation allows the holder to bear the mechanical stress of mounting without transmitting excessive force to the sensor magnet, preventing cracks while maintaining secure fixation.
2Reliability
If preliminary machining (knurling and grooving) is performed on motor shafts to fix sensor magnets, then the fixation is secure, but the assembly complexity and manufacturing steps increase
Solution Approach 1:
The sensor magnet holder is pre-formed with integrated press fit and engagement portions before assembly. This preliminary preparation eliminates the need for on-site machining operations (knurling and grooving) on the motor shaft, reducing assembly complexity while maintaining reliable fixation through the pre-engineered holder structure.
3Force
If excessive force is applied during sensor magnet mounting, then the sensor magnet can be firmly secured, but the sensor magnet may crack
Solution Approach 1:
The sensor magnet holder distributes mounting force across multiple localized engagement portions (front and rear engagement portions with knurling surfaces) rather than concentrating force on the sensor magnet itself. This localized force distribution secures the magnet firmly while preventing cracks by avoiding excessive stress concentration on the magnet material.
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 ensures a secure, crack-resistant sensor magnet mounting with improved resistance to relative movement and reduced assembly complexity, while preventing grease oozing towards Hall sensor boards.
Implementation Method 1
at least one of the snap fit tongues is brought into contact with at least one flat surface of the sensor magnet, by utilizing elasticity of the snap fit tongues
Implementation Method 2
a press-fit assembly that eliminates the need for conventional fixation methods
Data Source
Figure 1
Figure 2(A)~2(B)
Figure 3(A)~3(D)
AI summary
A sensor magnet holder is formed such that a cylindrical portion, a flange portion formed by increasing the diameter of one end part of the cylindrical portion, a magnet rear-end engagement portion formed at the other end part of the cylindrical portion, and four plate-like snap fit tongues are formed integral with one another. The cylindrical portion including the flange portion has, on its inner diametral side, a press fit portion to be press-fitted to a motor shaft. The four plate-like snap fit tongues have respective magnet front-end engagement portions formed on an outer diametral side of their tip portions. The four snap fit tongues are brought into contact with respective flat inner surfaces of the sensor magnet having four flat inner surfaces, by utilizing elasticity of the snap fit tongues. The sensor magnet is retained between the magnet rear-end engagement portion and the magnet front-end engagement portions.