Two-Part Shaft Rotor System for High-Speed Electric Machines

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Solution Overview

Problem

High-speed electrical machine rotors with high-energy rare earth permanent magnets face challenges in achieving a compact, stable, and cost-effective design that maximizes energy density while effectively absorbing centrifugal forces and tolerating temperature fluctuations.

Innovation Solution

A two-part shaft rotor system with a magnetic element receptacle in one shaft part and a connecting rod allowing the two shaft parts to be plugged together, using a material with high mechanical stability and low thermal expansion, and incorporating an elastic compensating element to manage centrifugal forces and tolerance differences.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a single-piece shaft design is used, then structural strength is improved, but manufacturing complexity and cost increase

Engineering Contradiction:
Improvestructural strengthVSAvoidmanufacturing complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The shaft is divided into two separate shaft parts that can be manufactured independently and then assembled together. This segmentation allows each part to be produced with standard manufacturing processes, reducing overall manufacturing complexity and cost while maintaining the structural integrity needed for high-speed operation.

Inventive Principle:
Principle #1Segmentation

2Reliability

If magnets are securely fixed to prevent shifting, then reliability is improved, but centrifugal force absorption capacity worsens

Engineering Contradiction:
Improvemagnet stabilityVSAvoidcentrifugal force absorption
Core Design Contradiction:
ReliabilityVSForce

Solution Approach 1:

The magnetic elements are arranged in a conical configuration rather than a flat circular pattern. This three-dimensional arrangement allows the magnets to be securely positioned while the conical structure itself helps manage and distribute centrifugal forces more effectively during high-speed rotation.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Quantity of substance

If maximum active mass of magnets is used, then energy density is improved, but structural rigidity worsens

Engineering Contradiction:
Improvemagnet massVSAvoidstructural rigidity
Core Design Contradiction:
Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The shaft parts are made from composite materials that provide both the necessary structural rigidity to support maximum magnet mass and the mechanical stability required for high-speed operation. The composite construction allows optimization of both strength-to-weight ratio and structural stiffness.

Inventive Principle:
Principle #40Composite materials

4Ease of operation

If shaft parts are designed for easy assembly, then ease of operation is improved, but connection stability worsens

Engineering Contradiction:
Improveassembly simplicityVSAvoidconnection stability
Core Design Contradiction:
Ease of operationVSStability of the object's composition

Solution Approach 1:

One shaft part is designed to be inserted into or nested within the other shaft part, creating a telescopic or nested assembly structure. This nested design enables simple push-together assembly while maintaining stable mechanical connection through the nested interface.

Inventive Principle:
Principle #7Nested doll (Nesting)

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

The solution enables a compact, stable, and cost-effective rotor system that maximizes energy density, simplifies assembly, and effectively compensates for centrifugal forces and temperature variations, enhancing the operational reliability of high-speed electrical machines.

Implementation Method 1

the shaft part, with its magnetic element receptacle, can suitably absorb the centrifugal forces generated by the at least one magnetic element when rotating a shaft that is connected to the rotor

Methodology Applied
Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 2

an at least partially elastic compensating element is provided on the inner peripheral surface of the magnetic element receptacle and/or on the outer peripheral surface of the at least one magnetic element

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 3

the connecting rod is made, for example, from a material with the greatest possible mechanical stability and the lowest possible coefficient of thermal expansion

Methodology Applied
Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentEP3261217B1Rotor system for an electric machine, electrical machine comprising the rotor system, and a method of producing the rotor system
Publication Date: 2022.09.07 ROBERT BOSCH GMBH
  • EP3261217B1 patent drawingFigure 1
  • EP3261217B1 patent drawingFigure 2
  • EP3261217B1 patent drawingFigure 3a~3b

AI summary

The invention relates to a rotor system for an electric machine (1) comprising: at least one magnetic element (5), a two-part shaft (6) with a first shaft part (12) and a second shaft part (13), wherein at least one shaft part (13) has a magnetic element receptacle (16) for receiving the at least one magnetic element (5) and a shaft part receptacle (36) for receiving at least one section of the opposite other shaft part (12).