Universal Motor Interpole Layout for Bidirectional Commutation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Universal motors in power tools face inefficiencies and increased heating/sparking when reversing direction due to magnetic field distortion, requiring complex solutions like rotatable brush rings for balanced performance in both forward and reverse rotations.

Innovation Solution

Incorporating interpoles between primary stator poles and reducing pole arcs in the motor design, which reduces magnetic field distortion and eliminates the need for commutation timing advance, allowing for consistent power output in both directions without mechanical brush advances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If universal motor reverses rotation direction, then operational versatility is improved, but magnetic field distortion increases causing heating and sparking

Engineering Contradiction:

Improverotation direction controlVSAvoidmagnetic field distortion

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The stator pole structure is segmented into multiple sections with different pole arc lengths. The first stator pole has a first pole arc and the second stator pole has a second pole arc, creating asymmetric magnetic field distribution that reduces distortion during direction reversal while maintaining operational versatility

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the stator are given different magnetic properties through varying pole arc lengths. The first stator pole region has one magnetic characteristic while the second stator pole region has another, optimizing the magnetic field distribution to minimize distortion and harmful effects during bidirectional operation

Inventive Principle:

Principle #3Local quality

2Reliability

If commutation timing advance is used to reduce heating and sparking, then motor reliability is improved, but device complexity increases

Engineering Contradiction:

Improvecommutation performanceVSAvoidmechanical brush advance structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The mechanical commutation timing advance mechanism is replaced with an asymmetric magnetic field design. The different pole arc lengths inherently provide the timing advance function through magnetic field distribution, eliminating the need for complex mechanical brush advance structures while maintaining improved commutation performance

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If pole arcs are reduced in motor design, then magnetic field distortion is reduced, but power output may be affected

Engineering Contradiction:

Improvemagnetic field distortionVSAvoidpower output

Core Design Contradiction:

Object-affected harmful factorsVSPower

Solution Approach 1:

Instead of uniformly reducing all pole arcs, the design applies different pole arc lengths to different stator poles. This localized differentiation reduces magnetic field distortion in critical regions while preserving sufficient magnetic flux in other regions to maintain power output

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The asymmetric pole arc configuration creates an optimized magnetic field distribution that reduces distortion effects. The first pole arc and second pole arc are deliberately made different to balance the magnetic fields during bidirectional rotation, maintaining power output while reducing harmful distortion

Inventive Principle:

Principle #4Asymmetry

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 enhances commutation, reduces heating and sparking, and maintains power performance across a range of speeds and loads, simplifying the motor structure and extending brush life while achieving balanced power in both rotational directions.

Implementation Method 1

The first stator interpole and the second stator interpole are each positioned between the first primary stator pole and the second primary stator pole

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Implementation Method 2

Inefficiencies and increased heating/sparking when reversing direction due to magnetic field distortion

Methodology Applied

Scientific EffectMagnetic field distortion: Magnetic Field

Implementation Method 3

The brushed motor is configured to receive power from the power source input

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11894754B2Power tool including universal motor having interpoles

Publication Date: 2024.02.06 MILWAUKEE ELECTRIC TOOL CORP

AI summary

A hand held power tool that includes a housing, a power source input configured to receive power from a power source, and a brushed motor located within the housing. The brushed motor is configured to receive power from the power source input. The brushed motor includes a first primary stator pole including a first pole neck and a first pole arc, a second primary stator pole including a second pole neck and a second pole arc, a first stator interpole including a first interpole neck, and a second stator interpole including a second interpole neck. The first stator interpole and the second stator interpole are each positioned between the first primary stator pole and the second primary stator pole.