Outer-Rotor DC Brushless Motor Eliminates Brush Abrasion

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Solution Overview

Problem

Conventional DC motors in ceiling fans experience high malfunction rates due to abrasion and electromagnetic interference caused by frequent contact and separation of brushes and commutators, leading to sparks and potential damage to other electronic components.

Innovation Solution

An outer-rotor type DC brushless motor is used, where a stator and rotor assembly interact without direct contact, utilizing a controller and magnetism sensors to generate an inductive magnetic field that drives the rotor assembly, eliminating the need for brushes and commutator contact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional DC motors with brushes and commutators are used, then the motor can drive the ceiling fan blades, but the frequent contact and separation of brushes and commutators cause abrasion, sparks, and electromagnetic interference leading to high malfunction rates

Engineering Contradiction:

Improvemotor reliabilityVSAvoidabrasion and electromagnetic interference

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent replaces the mechanical contact system (brushes and commutators) with an electromagnetic field-based system. The outer-rotor DC brushless motor uses a stator with coils and a rotor with permanent magnets, where electromagnetic induction creates the driving force without physical contact between moving and stationary components. This substitution eliminates abrasion, sparks, and electromagnetic interference associated with brush-commutator contact.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention extracts and removes the problematic brushes and commutators from the motor system. By using a brushless design where the rotor contains permanent magnets and the stator contains coils, the system achieves motor function without the harmful contact components, directly eliminating the source of abrasion and electromagnetic interference.

Inventive Principle:

Principle #2Taking out (Extraction)

2Use of energy by moving object

If brushes and commutators are used for power transmission, then electrical power can be delivered to the rotor, but the high frequency contact and separation causes surface abrasion and sparks

Engineering Contradiction:

Improvepower transmission to rotorVSAvoidsurface abrasion and sparks

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the mechanical electrical contact system with an electromagnetic field system. Power is transmitted to the rotor through electromagnetic induction between the stator coils and rotor magnets, eliminating the need for physical brush-commutator contact and thereby preventing surface abrasion and spark generation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention introduces electromagnetic fields as an intermediary for power transmission. Instead of direct electrical contact through brushes and commutators, the stator coils generate a magnetic field that induces current in the rotor, serving as a non-contact intermediary for energy transfer and eliminating harmful physical contact.

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 solution significantly reduces the risk of sparks, abrasion, and electromagnetic interference, enhancing the reliability and performance of ceiling fans by ensuring smooth and efficient operation without direct electrical contact between moving parts.

Implementation Method 1

The controller detects polarity of the permanent magnets through the magnetism sensors

Methodology Applied

Scientific EffectMagnetic field detection: Magnetic Field

Implementation Method 2

the controller changes current of the stator windings to produce an inductive magnetic field

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 3

The rotor assembly has permanent magnets interacting with the stator windings... produce an inductive magnetic field with poles the same to the permanent magnets to drive the rotor assembly

Methodology Applied

Scientific EffectMagnetic repulsion: Magnetism

Data Source

PatentUS7157872B1Ceiling fan with outer-rotor DC brushless motor

Publication Date: 2007.01.02 AMITY TECHNOLOGY CO LTD

AI summary

A ceiling fan with an outer-rotor type DC brushless motor has a center base with multiple blades and a DC brushless motor as a driving source for the fan. The DC brushless motor includes a controller, magnetism sensors, a stator with stator windings and a rotor assembly connected to the fan and having permanent magnets interacting with the stator windings. The controller detects polarity of the permanent magnets through the magnetism sensors. Based on the detected results, the controller changes current of the stator windings to produce an inductive magnetic field with poles the same to the permanent magnets to drive the rotor assembly. Accordingly, the blades of the fan are driven to rotate.