Electric Motor Rotor Core Axial Hole Forming Method
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Solution Overview
Problem
Existing methods for manufacturing rotor cores in electric rotating machines face challenges such as reduced shaping accuracy, high productivity costs, and decreased fitting strength due to large pressing loads and displacement between molds, leading to increased resistance loads during shaft insertion.
Innovation Solution
A method involving preliminary shaping, punch-through, ironing, and sizing steps to form a rotor core with a cylindrical boss section and axial hole, where the billet is forged with a boss section-side hole and punched through using a center hole punch to create a disk section-side hole, reducing the resistance load and maintaining fitting strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the axial hole is formed in one pressing step using a punch, then the manufacturing process is simplified, but the shaping accuracy is lowered due to large slide movement
Solution Approach 1:
The axial hole formation process is divided into two separate steps: first forming a preliminary hole, then punching through to complete the axial hole. This segmentation allows each step to be optimized independently, with the punch-through step using a smaller diameter punch that requires less slide movement, thereby improving shaping accuracy while maintaining manufacturing simplicity.
Solution Approach 2:
A preliminary hole is formed in the boss section before the final punch-through step. This preliminary action creates a guide path for the subsequent punch-through operation, reducing the required slide movement and improving the accuracy of the final axial hole formation.
2Ease of manufacture
If the axial hole is formed in one pressing step, then the process is simplified, but a large pressing load is required which reduces productivity
Solution Approach 1:
The hole formation process is segmented into two steps with different pressing loads. The first step forms a preliminary hole with a smaller load, and the second step completes the axial hole. This segmentation reduces the peak pressing load required, allowing the use of smaller, more productive equipment while maintaining process simplicity.
3Adaptability or versatility
If the boring punch is part of the upper mold and the shaping punch is part of the lower mold, then the molding is flexible, but displacement between centers increases causing misalignment
Solution Approach 1:
The preliminary hole formation step creates a reference feature that guides the subsequent punch-through operation. This preliminary action ensures that the final axial hole is properly aligned with the boss section center, compensating for any potential displacement between upper and lower mold centers.
4Ease of manufacture
If excess metal flows into the smaller diameter portion and hole edge during pressing, then the hole is formed, but the resistance load of shaft insertion increases and fitting strength is lowered
Solution Approach 1:
The hole formation is segmented into two steps with different punch diameters. The first step uses a punch that forms a preliminary hole with controlled metal flow, and the second step uses a smaller punch to complete the axial hole. This segmentation prevents excessive metal flow into the final hole area, reducing interference with shaft insertion and maintaining fitting strength.
Solution Approach 2:
Different regions of the hole formation process are treated differently: the preliminary hole formation allows controlled metal flow, while the final punch-through step creates a clean hole edge with minimal excess metal. This local quality control ensures that the hole edge does not interfere with shaft insertion, maintaining both manufacturability and fitting strength.
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
This method enhances the accuracy and fitting strength of the rotor core, reducing the resistance load of shaft insertion while maintaining necessary assembly strength, and allows for precise alignment of the axial hole's axis centers.
Implementation Method 1
the billet is formed with the boss section-side hole by plastic deformation in the preliminary shaping step
Implementation Method 2
the remaining part of the axial hole on the side of the disk section as a disk section-side hole; the axial hole is constituted of the boss section-side hole, the disk section-side hole and a step portion between the boss section-side hole and the disk section-side hole
Implementation Method 3
an ironing step of bending the preliminary shape portions of the claw sections to form claw bent portions and claw tip portions, and taper-shaping the claw tip portions
Data Source
AI summary
The method is for manufacturing a rotor core having a cylindrical boss section formed with an axial hole, a disc section radially extending from one end of the boss section, and a plurality of claw sections provided along an outer periphery of the disk section. A boss section-side hole as a part of the axial hole is formed by plastic deformation in a preliminary shaping step. The remaining part of the axial hole of the billet disposed on a die is punched through using a center hole punch having a diameter smaller than an inner diameter of the boss section-side hole to form the disk section-side hole in the flush/punch through step, so that the axial hole is constituted of the boss section-side hole, the disk section-side hole and a step portion between the boss section-side hole and the disk section-side hole.