Punching Rotor Core Bridges to Prevent Deflection
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Solution Overview
Problem
The manufacturing process of rotor core pieces for magnet-embedded motors often results in bridge deflection, leading to shape deterioration and reduced strength, which adversely affects the motor's characteristics.
Innovation Solution
A method of punching core pieces that involves forming a through hole defining the radially-outer contour of the bridge while avoiding edge coincidence with the punch, and applying counter-moments to minimize deflection, along with coining and relief holes to enhance structural integrity and magnetic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the width of the bridge is reduced to improve motor characteristics, then the motor efficiency is improved, but the bridge deflection increases significantly during manufacturing
Solution Approach 1:
The patent applies preliminary action by performing coining on the bridge region before punching operations. This pre-compression treatment strengthens the bridge structure in advance, preventing excessive deflection during subsequent punching processes while maintaining the reduced bridge width necessary for low magnetic flux leakage
Solution Approach 2:
The patent applies preliminary anti-action by introducing counter-moments during the punching process to counteract the deflection forces. By applying opposing forces that balance the deflection moments, the bridge maintains its shape accuracy despite the reduced width that makes it more susceptible to deformation
2Adaptability or versatility
If multiple punching processes are applied to form magnet insertion holes and bridges, then the core piece functionality is achieved, but cumulative deflection occurs reducing bridge width accuracy
Solution Approach 1:
The patent merges multiple punching operations into a single integrated process where magnet insertion holes and bridges are formed simultaneously. This eliminates the cumulative deflection that occurs with sequential processes, as the structure is stabilized once by the coining treatment and all subsequent operations occur without additional deflection cycles
3Loss of energy
If the bridge width is minimized for optimal motor performance, then magnetic efficiency improves, but the structural strength of the bridge deteriorates
Solution Approach 1:
The patent changes the physical state and mechanical properties of the bridge material through coining compression. This process work-hardens the steel in the bridge region, increasing its strength and stiffness parameters to compensate for the reduced cross-sectional area, thereby maintaining structural integrity while preserving the low magnetic flux leakage characteristics
Data Source
AI summary
A method of punching a core piece having a bridge formed between a radially-outer end of a magnet insertion hole and an outer region of the core piece. The method includes providing a magnetic steel sheet and a punch configured to form the core piece, punching out the magnet insertion hole from the magnetic steel sheet, and forming a through hole that defines a radially-outer contour of the bridge by punching the magnetic steel sheet. The method includes forming the bridge between the radially-outer end of magnet insertion hole and the outer region of the core piece, and blanking the core piece, from the magnetic steel sheet, in an exterior shape with the punch while avoiding an edge of the punch from coinciding with the radially-outer contour of the bridge.