Sintered Magnet Holder Undercut Forming for Lower-Cost Retention
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Solution Overview
Problem
The manufacturing of magnet holders with undercut shapes is costly due to the need for post-processing methods like lathe machining, which increases the number of steps and manufacturing costs.
Innovation Solution
Integrally forming the magnet holding portion and shaft attachment portion with sintered metal and using plastic deformation to create the undercut portion, allowing for high surface accuracy and reduced processing costs through a one-shot molding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the undercut portion is formed by machining such as lathe machining, then the magnet can be locked and prevented from falling off, but the number of steps increases and manufacturing cost increases
Solution Approach 1:
The invention combines the sizing process and undercut portion formation into a single integrated operation. The sizing die simultaneously performs the sizing function and creates the undercut portion through its specific structure (with a portion having a smaller diameter in the axial direction), eliminating the need for separate machining steps and reducing manufacturing cost while ensuring magnet retention.
Solution Approach 2:
The undercut portion is formed in advance during the sizing process before the magnet is installed. The sizing die is designed with a specific structure that creates the undercut portion as part of the initial sizing operation, so the magnet retention feature is already in place before magnet installation, avoiding subsequent machining operations.
2Reliability
If the holder member is molded by die molding with undercut shape, then the magnet can be retained, but it is difficult to integrally mold the undercut shape and requires post-processing
Solution Approach 1:
The invention merges the sizing operation and undercut portion formation into one simultaneous process. The sizing die structure (with a portion having a smaller diameter in the axial direction) enables both functions to be performed in a single step, making the holder member manufacturable by die molding without requiring post-processing machining operations.
Solution Approach 2:
The invention changes the design approach by making the holder member suitable for die molding with integral undercut formation. Through proper selection of material (sintered metal with plastic fluidity) and sizing die design, the undercut portion can be formed as part of the sizing process rather than as a separate machining operation.
3Manufacturing precision
If the inner peripheral surface accuracy is increased, then the press-fitting margin can be controlled and attachment accuracy improves, but the manufacturing process becomes more complex
Solution Approach 1:
The invention combines high-precision surface formation and undercut portion creation in the single sizing operation. The sizing die simultaneously produces the precise inner peripheral surface needed for press-fitting and the undercut portion for magnet retention, achieving high attachment accuracy without adding processing complexity.
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
Reduces manufacturing costs and improves attachment accuracy of the magnet holder, enhancing the reliability and precision of rotation angle detection devices by preventing magnet detachment and improving coaxiality.
Implementation Method 1
The sintered metal is rich in plastic fluidity, so that high surface accuracy can be obtained by sizing. Therefore, as in the above-described configuration of the present invention, by integrally forming the magnet holding portion and the shaft attachment portion with sintered metal and sizing the inner peripheral surface of the shaft attachment portion, the inner peripheral surface with high accuracy can be molded by one shot without requiring a plurality of steps.
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
In a magnet holder 4 including: a shaft attachment portion 41 to which a shaft 2 is press-fitted and fixed; and a magnet holding portion 42 that is provided on one side in an axial direction of the shaft attachment portion 41 and holds a periphery of a magnet 5, and provided with an undercut portion 50 that engages with the magnet 5 in the axial direction on an inner peripheral surface 43 of the magnet holding portion 42 facing the magnet 5, the magnet holding portion 42 and the shaft attachment portion 41 are integrally formed of sintered metal, an outer peripheral surface and an end surface of the magnet holding portion 42 and an inner peripheral surface of the shaft attachment portion 41 are sized, and the undercut portion 50 is formed by plastic deformation of the magnet holding portion 42.