Stator Bobbin Gap-Hole Structure for Inductance and Molding Control
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Solution Overview
Problem
The rotary electrical machine's controllability is affected by varying inductance due to the distance between the segment coil and the back yoke, leading to issues such as decreased controllability and defective molding from resin stagnation during bobbin manufacturing.
Innovation Solution
Incorporating a first gap hole in the back-yoke-side side wall of the bobbin to distance the armature winding from the back yoke, reducing inductance and preventing resin stagnation, thereby enhancing controllability and preventing molding defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the side wall of the bobbin is locally increased to secure the distance between the segment coil and the back yoke, then the controllability of the rotary electrical machine is improved, but resin stagnation occurs during resin molding, leading to defective molding such as cracks and weld lines
Solution Approach 1:
The side wall of the bobbin is divided into multiple regions with different thicknesses. Specifically, the first side wall portion (adjacent to the coil insertion hole) has a greater thickness than the second side wall portion (adjacent to the back yoke), creating a stepped structure that segments the resin flow path and prevents stagnation while maintaining the required distance between the coil and back yoke.
Solution Approach 2:
Different portions of the bobbin side wall are given different thicknesses according to their specific functional requirements. The first side wall portion is made thicker to ensure proper insulation and spacing from the coil, while the second side wall portion is made thinner to facilitate resin flow and eliminate stagnation, thereby achieving local optimization of both electrical performance and manufacturing quality.
2Productivity
If the distance between the segment coil and the back yoke is reduced to improve winding occupancy, then the productivity and downsizing are improved, but the inductance increases, leading to decreased controllability
Solution Approach 1:
Instead of uniformly reducing the distance between the coil and back yoke in all directions, the invention introduces a dimensional variation in the radial direction by creating a stepped side wall structure. This allows the coil to be positioned closer to the back yoke in the axial direction (improving occupancy) while maintaining adequate radial spacing through the thicker first side wall portion, thus preserving controllability.
3Reliability
If the distance between the segment coil and the back yoke is increased to improve controllability, then the controllability is improved, but the inductance decreases, and the bobbin size increases, reducing productivity and increasing cost
Solution Approach 1:
The stepped side wall structure applies local quality by making the first side wall portion thicker only where needed for insulation and spacing, while keeping the second side wall portion thinner to minimize overall bobbin size. This localized thickness variation achieves the required controllability without unnecessarily increasing the total bobbin dimensions.
Data Source
AI summary
There included are a rotor (3), a stator core (21) having a plurality of slots (21c) between the rotor (3) and a back yoke (21a), resin bobbins (22) each of which includes a plurality of coil insertion holes (22a) arranged along a radial direction of the stator core (21) and is fit into the slot (21c), and a first gap hole (22ca) provided to a side wall (22c) that is closest to the back yoke (21a) among side walls of the bobbin (22).