Axial Flux Stator Flow Openings for Uniform Coil Cooling

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Solution Overview

Problem

Existing axial flux machines face challenges in achieving optimal coil cooling and high power density while maintaining a simplified and cost-effective structure.

Innovation Solution

The axial flux machine design includes a stator between two rotor disks with permanent magnets, a central support flange dividing the stator into halves, and flow openings for coolant distribution, ensuring each coil has a gap for efficient cooling, with a plastic encapsulation of iron cores and elastomer seals for sealing, allowing for effective coolant circulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the stator is divided into two halves with complex adhesive bonds and laser welding to enclose iron core halves, then the cooling performance is improved, but the manufacturing complexity and cost increase

Engineering Contradiction:
Improvecoil cooling performanceVSAvoidstator assembly complexity
Core Design Contradiction:
TemperatureVSDevice complexity

Solution Approach 1:

The stator is divided into two halves (first stator half and second stator half) that can be manufactured separately and then assembled together. This segmentation allows for simplified manufacturing of each half while maintaining effective cooling channels that pass through both halves, resolving the contradiction between cooling performance and manufacturing complexity

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The iron cores are enclosed within the stator halves using retaining rings that fit over the iron cores. The cooling channels are nested within the stator structure, with flow openings positioned to allow coolant passage through the iron cores. This nesting approach simplifies the overall assembly while maintaining effective cooling

Inventive Principle:
Principle #7Nested doll (Nesting)

2Strength

If the iron core halves are enclosed as a single unit between retaining rings using laser welding and adhesive bonds, then the structural integrity is improved, but the manufacturing cost and process complexity increase

Engineering Contradiction:
Improvestator structural integrityVSAvoidmanufacturing cost and process simplicity
Core Design Contradiction:
StrengthVSEase of manufacture

Solution Approach 1:

The stator is manufactured in two separate halves that are then assembled together using retaining rings. This segmentation allows each half to be manufactured independently with simpler processes, reducing overall manufacturing complexity and cost while maintaining structural integrity through the retaining ring assembly

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent replaces complex joining methods (laser welding and adhesive bonds) with a mechanical retaining ring system that encloses the iron core halves. This substitution simplifies the manufacturing process and reduces cost while maintaining adequate structural integrity for the application

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Temperature

If coolant flow channels are implemented through the stator structure, then the cooling efficiency is improved, but the device complexity increases

Engineering Contradiction:
Improvecoolant cooling efficiencyVSAvoidcooling channel structure complexity
Core Design Contradiction:
TemperatureVSDevice complexity

Solution Approach 1:

The cooling system is divided into two separate cooling channel halves, each integrated into a stator half. The channels are designed to work together when the stator halves are assembled, with flow openings positioned to enable coolant passage through the iron cores. This segmentation simplifies the cooling channel structure while maintaining effective cooling

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The stator halves serve multiple functions: they provide structural support for the iron cores, contain the cooling channels, and facilitate coolant flow through the iron cores via flow openings. This multi-functionality reduces overall device complexity by combining several functions into single components

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 design achieves optimal coil cooling, enabling high power density and simplified assembly, while maintaining structural integrity and cost-effectiveness, with the option to use gearbox oil as a coolant in wet applications.

Implementation Method 1

A coolant flow is defined from the distribution channel through the flow openings to the collection channel. The distribution channel of the second, right-hand stator cover, the gaps between the successive coils of the second stator half, the flow openings in the support flange, the gaps between the successive coils of the first stator halves, and the collection channel of the first, left-hand stator cover are in fluid communication with each other.

Methodology Applied
Scientific EffectConvection: Convection

Implementation Method 2

The circumferential distribution channel of the second, right-hand stator cover ensures that the 'fresh' coolant reaches all coils equally. The cooling medium flows through these gaps from radially outside to radially inside. Once radially inside, the cooling flow enters the first stator half through the designated flow opening in the central support flange, from where it flows radially outward again through the gaps between the coils of the first stator half.

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP4035253B1Axial flux machine
Publication Date: 2025.01.22 SCHAEFFLER TECHNOLOGIES AG & CO KG
  • EP4035253B1 patent drawingFigure 1~2
  • EP4035253B1 patent drawingFigure 3~5
  • EP4035253B1 patent drawingFigure 6

AI summary

The invention relates to an axial flux machine (1) comprising a stator (6) which is located between a first rotor disk (2) and a second rotor disk (3). The base part of the stator (6) is a central support flange (4) which defines a first lateral face (4A) and a second lateral face (4B). The central support flange (4) has a plurality of flow openings (54). A first, left stator cover (8) is mounted, with a formed collection channel (58S), on the first lateral face (4A) of the support flange (4), and a second, right stator cover (9) is mounted, with a formed distribution channel (58V), on the second lateral face (4A) of the support flange (4).