Linear Motor Pitch Ratio to Cut Cogging and Raise Thrust Density

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Solution Overview

Problem

The existing linear transport systems face issues with cogging thrust and thrust density due to inappropriate combinations of magnet pitch and tooth pitch, leading to reduced performance.

Innovation Solution

A linear transport system is designed with a stator module featuring an iron core and coils wound around teeth, where the magnet pitch and tooth pitch are optimized such that 1.3≤Lm/Lt≤1.4, and a motor drive control device supplies single-phase alternating current to the coils, ensuring efficient electromagnetic propulsion of magnets along a linear guide.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the magnet pitch and tooth pitch combination is inappropriate, then the device complexity is reduced, but the cogging thrust increases and thrust density decreases

Engineering Contradiction:

Improvemagnet pitch and tooth pitch combinationVSAvoidcogging thrust

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The patent applies parameter changes by optimizing the ratio between magnet pitch (Lm) and tooth pitch (Lt) to fall within the specific range of 1.3≤Lm/Lt≤1.4. This parameter optimization simultaneously reduces cogging thrust while improving thrust density, resolving the technical contradiction between ease of manufacture and harmful factors generated by the system.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If the magnet pitch and tooth pitch combination is inappropriate, then the device complexity is reduced, but the thrust density decreases

Engineering Contradiction:

Improvemagnet pitch and tooth pitch combinationVSAvoidthrust density

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

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 improves thrust density while reducing cogging thrust, maintaining maximum thrust and minimizing the size of the motor unit, thus enhancing the overall efficiency and reducing manufacturing costs.

Implementation Method 1

a movable element to be propelled by an electromagnetic force from the coil

Methodology Applied

Scientific EffectElectromagnetic force: Electromagnetic Propulsion

Implementation Method 2

a coil wound around a tooth of a stator is energized to generate thrust in a movable element in the use of an attractive force and a repulsive force between a magnet and the coil

Methodology Applied

Scientific EffectAttractive force and repulsive force between magnet and coil: Lorentz Force

Data Source

PatentUS12199488B2Linear transport system

Publication Date: 2025.01.14 MITSUBISHI ELECTRIC CORP

AI summary

A linear transport system includes: a stator module including an iron core that includes a plurality of teeth and a coil wound around the iron core; a movable element that includes a plurality of identical magnets disposed on a side surface parallel to a moving direction, and is propelled by an electromagnetic force from the coil; and a motor drive control device that controls the movable element by supplying an independent current of single-phase AC individually to the coil included in the stator module. When Lm is a magnet pitch that is a pitch of the magnets disposed in the movable element, and Lt is a tooth pitch that is a pitch of the teeth, 1.3≤Lm/Lt≤1.4 is satisfied.