Variable Width Rotor Bridge for Stress Dispersion
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Solution Overview
Problem
Conventional rotor designs for rotating electric machines in vehicles face stress concentration issues due to temperature changes and centrifugal forces, particularly in the bridge portion of the rotor core, which can lead to reduced strength and potential failure.
Innovation Solution
The rotor design incorporates a bridge portion with sequentially arranged large-width, medium-width, and small-width sections in the radial direction, filled with a filler material that expands and contracts with temperature changes, dispersing stress generated by both temperature and centrifugal forces, and uses an insulating material with a coefficient of linear expansion similar to metal, such as polyetherimide or glass fiber-reinforced resin, to enhance strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the bridge portion width is increased to disperse stress from centrifugal force, then stress dispersion improves, but the rotor core volume and weight increase
Solution Approach 1:
The bridge portion is designed with variable width along the radial direction, creating different structural characteristics in different regions. The width increases from the magnet side toward the q-axis core portion side, providing local reinforcement exactly where stress concentration occurs during rotation, rather than uniformly increasing the entire bridge portion width.
2Ease of manufacture
If the filler material is used to fill both the magnet housing hole and flux barrier, then manufacturing simplicity improves, but stress concentration increases due to thermal expansion and contraction
Solution Approach 1:
The flux barrier region is specifically designed with a reduced width portion that provides stress relief, creating a local structural characteristic that accommodates the thermal expansion and contraction of the filler material. This localized design prevents stress concentration in the bridge portion while maintaining the simplicity of using filler material in both regions.
3Strength
If the bridge portion is reinforced to ensure sufficient strength, then mechanical strength improves, but the device complexity increases
Solution Approach 1:
The bridge portion width varies continuously along the radial direction, creating a smooth curved transition rather than abrupt geometric changes. This curved width profile provides gradual stress distribution and reinforces the bridge portion while maintaining a relatively simple overall structure that can be manufactured using conventional processes.
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 configuration effectively disperses stress across the bridge portion, ensuring sufficient strength and reducing the concentration of stress, thereby improving the durability and performance of the rotor.
Implementation Method 1
the filler material repeatedly expands and contracts in accompaniment with the change in environmental temperature during operation and stop
Implementation Method 2
concentration of stress occurring in the bridge portion based on centrifugal force during rotation of the rotor
Data Source
AI summary
A rotor includes a rotor core in which a plurality of magnet housing holes are arrayed in a circumferential direction and a plurality of magnets fixed and held in the magnet housing holes by a filler material. The rotor core includes: a q-axis core portion, an outer flux bather that is formed between the q-axis core portion and the magnet and is filled with the filler material; and a bridge portion formed between a stator-side core portion and the q-axis core portion. The bridge portion includes a large-width portion, a small-width portion and a medium-width portion that are sequentially disposed from the q-axis core portion side towards the stator-side core portion side in the circumferential direction. The large-width portion has the largest radial-direction width. The small-width portion has the smallest radial-direction width. The medium-width portion has a medium radial-direction width between the largest radial-direction width and the smallest radial-direction width.