Stator Cooling via Transverse Impact Surfaces

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Solution Overview

Problem

Existing drive devices with brushless motors have a relatively low cooling effect, necessitating either reduced power or a powerful fan to manage heat, which is inefficient.

Innovation Solution

The implementation of transverse impact surfaces and longitudinal ribs on the outer surface of the stator to enhance airflow turbulence and heat exchange, combined with slot insulation and thermally conductive material filling to improve heat transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a fan is used to generate cooling air flow along the outside of the stator, then the stator is cooled, but the cooling effect is relatively low requiring either reduced power or a powerful fan

Engineering Contradiction:
Improvestator cooling effectVSAvoidfan power requirement
Core Design Contradiction:
TemperatureVSPower

Solution Approach 1:

The stator outer surface is segmented into multiple longitudinal ribs, creating divided flow paths for the cooling air. This segmentation increases the surface area and extends the flow path length, improving heat exchange efficiency without requiring higher fan power.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Impact surfaces are added transverse to the longitudinal extent of the stator, creating a three-dimensional flow pattern with diversions and turbulences. This dimensional addition extends the cooling air flow path and enhances heat exchange between the stator and cooling air.

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

2Reliability

If the receiving space is completely encapsulated by the stator and closing elements, then metallic particles are prevented from entering, but the cooling effect is reduced

Engineering Contradiction:
Improveprotection from metallic particlesVSAvoidcooling effect
Core Design Contradiction:
ReliabilityVSTemperature

Solution Approach 1:

The stator design incorporates longitudinal ribs and impact surfaces that create localized turbulence and extended flow paths in specific regions. This allows the cooling air to effectively cool the stator through enhanced heat exchange while maintaining the encapsulated structure that protects against metallic particles.

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

This configuration significantly enhances cooling efficiency by extending the airflow path and improving heat exchange between the stator and cooling air, allowing for effective cooling without the need for high-powered fans or reduced device power.

Implementation Method 1

a fan is provided, which is coupled for movement to the drive axle. By means of this fan, a flow of cooling air can be generated between an inner surface of the drive housing and an outer surface of the stator along the longitudinal extension of the stator

Methodology Applied
Scientific EffectConvection: Convection

Implementation Method 2

a plurality of impact surfaces are formed on the outer surface of the stator, which extend transversely to the longitudinal extent of the stator. In this way, diversions and turbulences of the cooling air flow are generated on the outer surface of the stator, resulting in an extension of the flow path and an improved heat exchange between the stator and the cooling air flow

Methodology Applied
Scientific EffectTurbulence: Turbulence

Implementation Method 3

the stator has a stator winding held on a plurality of webs, with the intermediate spaces formed by the stator winding and the webs being partially filled with a thermally conductive material. In this way, good heat transfer from the stator winding to a stator core can be ensured, as a result of which adequate cooling of the stator winding can also be ensured

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP2015426B1Drive device for a hand tool
Publication Date: 2011.08.31 HILTI AG
  • EP2015426B1 patent drawingFigure 1
  • EP2015426B1 patent drawingFigure 2
  • EP2015426B1 patent drawingFigure 3

AI summary

The device has a stator (8) mounted in a drive housing (6) and including a longitudinal extension between stator ends (10). A termination element (12) is arranged at the ends. A rotor (14) is arranged in a receiving chamber bordered by the stator and the termination element. The rotor is rotatably mounted at the termination element over a drive axle. A fan (22) is movably coupled with the axle to produce cooling air flow between a housing inner surface (26) and a stator outer surface (28). Deflector surfaces are formed at the outer surface and extend transverse to the extension.