Tubular Rotor Shaft Keyway Structure for Consistent Wall Thickness

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Solution Overview

Problem

In electric vehicle powertrains, rotor shafts with keyways face challenges in maintaining consistent wall thickness while minimizing weight and optimizing manufacturing efficiency, as the formation of keyways reduces wall thickness, leading to unnecessary weight increase.

Innovation Solution

A tubular rotor shaft with internal features, where the wall thickness is maintained consistently throughout, and keyways are formed on the outer surface with a thickness equal to or greater than the non-keyway portions, minimizing weight and optimizing manufacturing efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If keyways are formed in the outer surface of the rotor shaft, then coupling functionality is improved, but wall thickness at keyway locations is reduced below minimum requirements

Engineering Contradiction:

Improvecoupling functionalityVSAvoidwall thickness consistency

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent moves the keyway functionality from the outer surface to the inner surface of the rotor shaft. By forming keyways on the inner circumference rather than the outer circumference, the design maintains consistent outer wall thickness while achieving the necessary coupling function through internal keyway structures that engage with corresponding keys on the outer surface.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent inverts the traditional keyway location by placing them on the inner surface instead of the outer surface. This inversion allows the shaft to maintain its outer dimensions and wall thickness consistency while still providing the required keyway coupling function through the inverted configuration.

Inventive Principle:

Principle #13The other way round (Inversion)

2Manufacturing precision

If wall thickness is increased at non-keyway portions to compensate for keyway depth, then minimum wall thickness requirement is met, but shaft weight increases undesirably

Engineering Contradiction:

Improveminimum wall thickness requirementVSAvoidshaft weight

Core Design Contradiction:

Manufacturing precisionVSWeight of moving object

Solution Approach 1:

By relocating keyways to the inner surface, the patent eliminates the need to increase wall thickness at non-keyway portions. The consistent wall thickness is maintained throughout the shaft because the keyway depth no longer reduces the effective wall thickness at the outer surface, thereby avoiding unnecessary weight increase.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Weight of moving object

If rotor shafts are formed as hollow shafts, then weight is minimized, but wall thickness consistency becomes difficult to maintain at keyway locations

Engineering Contradiction:

Improveshaft weightVSAvoidwall thickness consistency

Core Design Contradiction:

Weight of moving objectVSManufacturing precision

Solution Approach 1:

The patent resolves the conflict between hollow shaft weight minimization and wall thickness consistency by forming keyways on the inner surface. This allows the hollow shaft structure to maintain its weight advantage while the inner keyways are formed without compromising the outer wall thickness consistency, as the keyway material removal occurs internally rather than externally.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS20250030305A1Rotor shaft with localized splines for keyways

Publication Date: 2025.01.23 METAL FORMING & COINING CORP

AI summary

A rotor shaft includes a tubular shaft having an inner surface, an outer surface, a first end, and an opposing second end. At least one keyway is formed in the outer surface of the tubular shaft. An inner diameter of the tubular shaft is aligned with the at least one keyway is less than an inner diameter of the tubular shaft not radially with the at least one keyway.