Hub Motor Thermal Grease Conduction Path

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Solution Overview

Problem

Conventional drive devices for electric vehicles, such as electric bicycles and mobility aid vehicles, with motors housed in hubs suffer from poor heat dissipation due to inadequate thermal management.

Innovation Solution

A drive device design featuring a hollow hub with a motor and speed reducer, where thermal grease is used to thermally connect the hub and motor housing, facilitating efficient heat transfer and dissipation from the motor to the hub's outer surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the motor is housed in the hub, then the drive device has a compact structure, but the heat dissipation performance deteriorates

Engineering Contradiction:

Improvecompact structureVSAvoidheat dissipation performance

Core Design Contradiction:

Volume of moving objectVSTemperature

Solution Approach 1:

Thermal grease is introduced as an intermediary substance between the motor housing and hub to facilitate heat transfer. The thermal grease fills the gap and provides a thermal conduction path, allowing heat to be efficiently transferred from the motor housing to the hub while maintaining the compact integrated structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The physical state and thermal properties of the interface between motor housing and hub are changed by applying thermal grease. This modifies the thermal conductivity parameter of the interface, transforming it from a poor thermal contact to an efficient heat transfer path while preserving the compact design.

Inventive Principle:

Principle #35Parameter changes

2Temperature

If thermal grease is used to connect hub and motor housing, then heat dissipation improves, but thermal grease leakage may occur

Engineering Contradiction:

Improveheat dissipationVSAvoidthermal grease leakage

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

A seal member is installed beforehand between the hub and motor housing to create a barrier that prevents thermal grease from leaking. This cushioning measure is implemented in advance to contain the thermal grease within the intended space while still allowing effective heat transfer.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

A flexible seal member (such as an O-ring or gasket) is used to create a flexible barrier that prevents thermal grease leakage. The seal member conforms to the mating surfaces and maintains containment under varying thermal and mechanical conditions.

Inventive Principle:

Principle #30Flexible shells and thin films

3Temperature

If thermal grease is applied between hub and motor housing, then thermal connection improves, but lubrication for speed reducer may be affected

Engineering Contradiction:

Improvethermal connectionVSAvoidlubrication

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The space between hub and motor housing is segmented into distinct functional zones: a thermal grease application area for heat transfer, and a sealed lubrication area for the speed reducer. The seal member creates this segmentation, ensuring thermal grease remains in the heat transfer zone and cannot contaminate the lubrication system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The seal member acts as an intermediary barrier that separates the thermal grease function from the lubrication function. It allows thermal grease to perform its heat transfer role while preventing it from interfering with the speed reducer lubrication, thus protecting the lubrication system from contamination.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration enhances heat discharging performance, ensuring effective thermal management and preventing overheating issues in the motor, while minimizing the risk of thermal grease leakage and maintaining lubrication for the speed reducer.

Implementation Method 1

thermal grease thermally connecting the hub and the motor housing to each other

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS11063497B2Drive device

Publication Date: 2021.07.13 NIDEC CORP(JP)

AI summary

A drive device includes a hollow hub rotatable about hub shafts extending parallel to a center axis, a motor housed in the hub and fixed to the hub shafts, and a speed reducer connected to the motor and the hub. The motor includes a rotor including a motor shaft extending parallel to the hub shafts, a stator disposed outside the rotor in a radial direction, and a motor housing holding the stator therein. The drive device includes thermal grease thermally connecting the hub and the motor housing to each other.