Permanent-Magnet Rotor Fiber Binding for Thermal Expansion Stability

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Solution Overview

Problem

Existing permanent-magnet rotors fail to withstand high rotational speeds and axial thermal expansion due to adhesive bonding failure and differential material expansion, leading to delamination of the retaining sleeve.

Innovation Solution

A rotor design featuring a binding band with crossed windings of reinforcing fibers and a retaining sleeve with unidirectional fiber winding, along with a nonmagnetic metal sheath, to enhance mechanical stability and resist delamination under thermal stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If adhesive bonding is used to hold permanent magnets on the assembly hub, then the rotor can operate at moderate speeds, but the adhesive bonding fails under excessive centrifugal force from high rotational speeds

Engineering Contradiction:

Improverotational speedVSAvoidadhesive bonding reliability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The rotor structure is segmented into distinct functional components: assembly hub, permanent magnets, binding band with crossed windings, and retaining sleeve. This segmentation allows each component to address specific mechanical challenges independently, with the binding band and retaining sleeve providing structural support without relying on adhesive bonding alone.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention employs composite material structures including the binding band made of reinforcing fibers and the retaining sleeve made of carbon fiber. These composite materials provide the necessary mechanical strength and stiffness to withstand high centrifugal forces, replacing the insufficient adhesive bonding system.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If a carbon fiber retaining sleeve is used to prevent radial separation of magnets, then radial stability is improved, but axial thermal expansion causes differential material expansion leading to delamination

Engineering Contradiction:

Improveradial stability of magnetsVSAvoidaxial thermal expansion

Core Design Contradiction:

Stability of the object's compositionVSTemperature

Solution Approach 1:

The invention changes the structural parameters of the retaining system by introducing crossed windings in the binding band and a unidirectional winding in the retaining sleeve. This parameter change allows the structure to accommodate thermal expansion differently, with the unidirectional carbon fiber winding providing thermal stability while maintaining radial constraint.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Different regions of the retaining structure have different fiber orientations optimized for their specific functions: the binding band has crossed windings to handle multi-directional stresses, while the retaining sleeve has unidirectional winding optimized for radial stability and thermal performance in its specific location.

Inventive Principle:

Principle #3Local quality

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 design effectively maintains the integrity of the rotor by preventing radial separation of permanent magnets and enhancing mechanical performance under axial deformation, ensuring stability at high speeds and thermal conditions.

Implementation Method 1

The retaining sleeve is made of carbon fiber and formed by a unidirectional winding around the rotor

Methodology Applied

Scientific EffectTensile strength: Tension

Implementation Method 2

the rotor may be subjected to temperatures which are sufficiently high so as to cause axial thermal expansion of all the materials of the rotor with the exception of the carbon fiber of the retaining sleeve

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

excessive rotation speed of the rotor, and therefore too high of a centrifugal force, means that the adhesive bonding between the permanent magnets and the assembly hub cannot be guaranteed to hold the magnets on the hub

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentUS12587051B2Permanent-magnet rotor resistant to thermal expansion and method of manufacture thereof

Publication Date: 2026.03.24 SKF MAGNETIC MECHATRONICS SAS

AI summary

A rotor includes an assembly hub intended to be fixed to a shaft, a plurality of permanent magnets which are supported by the assembly hub, and a binding band holding the plurality of permanent magnets in place. The binding band includes crossed windings of reinforcing fibers arranged around the plurality of permanent magnets. Preferably, the rotor further includes a retaining sleeve formed of a unidirectional winding of a reinforcing fiber arranged around the binding band.