Ribbed Motor Case Structure for Lightweight Torsional Stiffness
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Solution Overview
Problem
Rotary electric machines face a challenge in achieving both weight reduction and securing torsional stiffness, leading to increased vibration and noise due to electromagnetic excitation forces, which impairs vehicle quietness.
Innovation Solution
A motor case design featuring a tubular peripheral wall with a flange portion and damping ribs formed between the outer periphery and the flange portion, where the ribs cross each other to connect linear and annular ribs, enhancing torsional stiffness while reducing weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the motor case is made lighter for weight reduction, then weight decreases, but torsional stiffness deteriorates
Solution Approach 1:
The motor case is segmented into a thin-walled peripheral wall structure with multiple ribs (linear ribs parallel to the rotating shaft, annular ribs perpendicular to the rotating shaft, and damping ribs crossing between them) that divide the structure into smaller stiffened sections. This segmentation allows the case to be lighter while maintaining torsional stiffness through the distributed rib reinforcement.
Solution Approach 2:
The invention adds ribs in multiple dimensions (axial direction with linear ribs, circumferential direction with annular ribs, and diagonal/damping directions with damping ribs) to the thin-walled peripheral wall. This multi-dimensional reinforcement approach increases torsional stiffness without requiring increased wall thickness, thus maintaining weight reduction.
2Object-affected harmful factors
If torsional stiffness is increased to reduce vibration, then vibration and noise decrease, but weight increases
Solution Approach 1:
The damping ribs are segmented into multiple configurations (linear ribs, annular ribs, and crossing damping ribs) that work together to reduce torsional vibration. This segmented approach provides effective vibration damping without requiring a solid, heavy construction.
Solution Approach 2:
The motor case employs a composite structural design combining the thin-walled peripheral wall with multiple types of ribs (linear, annular, and damping ribs) formed integrally or as separate components. This composite structure achieves high torsional stiffness and vibration resistance with reduced weight compared to a solid homogeneous structure.
Data Source
AI summary
An object of the present invention is to promote weight reduction while improving torsional stiffness of a motor case of a rotary electric machine. A motor case accommodates a stator, a rotor facing an inner periphery of the stator, and a rotating shaft coupled to the rotor. The motor case includes a peripheral wall which is formed in a tubular shape and has a space accommodating the stator and the rotating shaft on an inside, a flange portion which is formed at one end of the peripheral wall and is coupled to an outside, and damping ribs which are formed at an outer periphery of the peripheral wall, are formed between a position crossing the outer periphery of the peripheral wall and the flange portion on an extension of the rotating shaft in a radial direction from an end portion of the stator, and are constituted by a plurality of ribs.