In-Wheel Motor Cooling Unit Using Bubble-Pump Phase Change

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Solution Overview

Problem

Existing cooling methods for in-wheel motors of electric vehicles suffer from poor cooling effects, low integration, and high equipment weight, which restrict the development of in-wheel motor technology due to overheating issues.

Innovation Solution

An integrated cooling unit for in-wheel motors utilizing an airtight container with a bubble pump and phase change heat transfer, where a cooling working medium boils, vaporizes, and is conveyed to an upper portion by bubble rising, efficiently cooling the motor and its components through indirect heat conduction and circulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If air cooling method is used for in-wheel motor, then equipment structure is simple, but cooling effect is poor

Engineering Contradiction:
Improvecooling system structureVSAvoidcooling effect
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent employs phase change cooling by introducing a phase change material into the cooling chamber that contacts the motor coil. The PCM absorbs heat from the motor coil through phase transition (solid-liquid or liquid-gas), providing efficient cooling. This resolves the contradiction by achieving superior cooling effect through phase change mechanism while maintaining relatively simple system structure compared to complex liquid cooling circuits.

Inventive Principle:
Principle #36Phase transitions

2Reliability

If liquid cooling method is used for in-wheel motor, then cooling effect is improved, but equipment weight increases

Engineering Contradiction:
Improvecooling effectVSAvoidsystem weight
Core Design Contradiction:
ReliabilityVSWeight of moving object

Solution Approach 1:

The patent uses phase change material to absorb heat from the motor coil, replacing traditional liquid cooling systems. The PCM provides high heat absorption capacity during phase transition, achieving effective cooling while reducing system weight by eliminating complex liquid cooling circuits, pumps, and large radiators.

Inventive Principle:
Principle #36Phase transitions

Solution Approach 2:

The patent integrates the cooling function directly into the motor structure by placing the phase change material in thermal contact with the motor coil within the motor housing. This merging of cooling functionality with the motor structure itself eliminates separate cooling system components, thereby reducing overall system weight while maintaining effective cooling.

Inventive Principle:
Principle #5Merging (Combining)

3Reliability

If traditional cooling systems are added to in-wheel motor, then cooling function is provided, but integration is low

Engineering Contradiction:
Improvecooling functionVSAvoidintegration level
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the cooling function with the motor structure by integrating the phase change material directly into the motor housing or stator structure. The cooling chamber is formed within the existing motor structure, and the PCM is positioned to directly contact the motor coil. This integration eliminates separate cooling systems and achieves high integration, resolving the contradiction between providing cooling function and maintaining low device complexity.

Inventive Principle:
Principle #5Merging (Combining)

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 enhances cooling performance, improves integration, and reduces the overall system weight while uniformly cooling the in-wheel motor, including the electric control chip and motor coil, by leveraging phase change heat transfer and bubble pump-driven circulation.

Implementation Method 1

efficient cooling of the in-wheel motor (comprising an electric control chip and a motor coil) is realized by utilizing phase change heat transfer of the cooling working medium

Methodology Applied
Scientific EffectPhase change heat transfer: Phase Change

Implementation Method 2

The working medium in the cooling unit boils and generates vapor

Methodology Applied
Scientific EffectBoiling: Boiling

Implementation Method 3

the vapor is led out to a condenser from a vapor guide port to condense into a liquid

Methodology Applied
Scientific EffectCondensation: Condensation

Implementation Method 4

the bubble pump drives the cooling working medium to be conveyed to an upper portion by utilizing a rising flow induced by bubble rising

Methodology Applied
Scientific EffectBubble rising induced flow: Bubble

Implementation Method 5

Heating elements such as the electric control chip and the motor coil of the in-wheel motor are mounted in different positions on an outer surface of the airtight container, and indirectly transfer heat to the cooling working medium through heat conduction of the wall surface of the container

Methodology Applied
Scientific EffectHeat conduction: Conduction (thermal)

Data Source

PatentEP4589825B1Integrated cooling unit for in-wheel motor
Publication Date: 2026.02.18 TIANJIN UNIV
  • EP4589825B1 patent drawingFigure 1
  • EP4589825B1 patent drawingFigure 2
  • EP4589825B1 patent drawingFigure 3

AI summary

Provided is an integrated cooling unit for an in-wheel motor, which belongs to the technical field of cooling devices. The integrated cooling unit for the in-wheel motor comprises an airtight container arranged inside the in-wheel motor, used for packaging a cooling working medium, and provided with a steam outlet and a liquid return port; a bubble pump laid on an inner wall surface of the airtight container, and used for driving the cooling working medium to be conveyed to an upper portion of the airtight container; a motor coil laid on an outside outer wall surface of the airtight container; and an electric control chip arranged on the wall surface of the airtight container, and the cooling working medium reaching a mounting position of the electric control chip.