Axial Gap Motor Structure Without Permanent Magnets

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Solution Overview

Problem

Existing axial gap motors using permanent magnets experience back electromotive force and increased electric power consumption during high-speed rotation, leading to reduced fuel efficiency and increased electric power consumption, particularly in hybrid vehicles.

Innovation Solution

An axial gap motor design that eliminates the use of permanent magnets by employing a rotor and stator cores made of soft magnetic materials with aligned end faces, generating magnetic flux to rotate the rotor without back electromotive force, and utilizing a non-magnetic rotor and stator bases to prevent deflection and contact between rotor and stator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If permanent magnets are used in the rotor, then the motor can generate magnetic flux to rotate the rotor, but back electromotive force is generated in the coils during high-speed rotation, increasing electric power consumption

Engineering Contradiction:

Improvemotor output powerVSAvoidelectric power consumption

Core Design Contradiction:

PowerVSUse of energy by moving object

Solution Approach 1:

The patent removes permanent magnets from the rotor structure entirely. Instead of using magnets to generate magnetic flux, the invention employs electromagnetic induction by positioning conductor bars (aluminum or copper) within the rotor core, which generates the necessary magnetic flux through induced currents during rotation, thereby eliminating back electromotive force and associated power losses.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the magnetic field generation mechanism (permanent magnets) with an electromagnetic induction mechanism (conductor bars generating flux through induced currents). This substitution transforms the motor from a magnet-based system to an induction-based system, eliminating the harmful back electromotive force effect while maintaining motor functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Speed

If permanent magnets are used in the rotor, then the motor achieves high-speed rotation capability, but fuel efficiency is reduced due to increased electric power consumption

Engineering Contradiction:

Improverotor rotation speedVSAvoidfuel efficiency

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the fundamental operating principle of the motor from magnet-based field generation to induction-based field generation. By using conductor bars that generate magnetic flux through induced currents rather than permanent magnets, the system achieves high-speed rotation without the energy losses associated with back electromotive force, thereby improving fuel efficiency.

Inventive Principle:

Principle #35Parameter changes

3Power

If rotor cores are made of soft magnetic material, then magnetic flux can be generated effectively, but the rotor and stator may come into contact due to magnetic attraction forces

Engineering Contradiction:

Improvemagnetic flux generationVSAvoidgap maintenance between rotor and stator

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent employs a non-magnetic material structure for the rotor base (opposed to the stator base) that acts as a mechanical counterbalance or support structure. This non-magnetic base prevents the rotor from being excessively attracted to the stator by providing a non-magnetic barrier or support that maintains the air gap, while the soft magnetic rotor cores still generate effective magnetic flux for motor operation.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

The patent applies different material properties to different parts of the rotor structure. The rotor cores are made of soft magnetic material to effectively generate magnetic flux, while the rotor base (the part facing the stator) is made of non-magnetic material to prevent excessive magnetic attraction and maintain the air gap. This local differentiation of material properties resolves the contradiction between flux generation and gap maintenance.

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

The design prevents back electromotive force and reduces electric power consumption, maintaining fuel efficiency and torque output while minimizing the need for field weakening, thus enhancing performance and efficiency.

Implementation Method 1

When current is passed through the coils 43, magnetic flux is generated in the stator core 42

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

Each of the rotor cores 32 is made of a soft magnetic material, and has a first end face 32a and a second end face 32b

Methodology Applied

Scientific EffectMagnetic flux generation in soft magnetic material: Magnetic Field

Data Source

PatentEP3896823B1Axial gap motor

Publication Date: 2026.03.04 TOYOTA JIDOSHA KK

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AI summary

In an axial gap motor, a rotor (3) includes a plurality of rotor cores (32) fixed in a circumferential direction of a rotor base (31), and a stator (4) includes a plurality of stator cores (42) fixed in a circumferential direction of a stator base (41), and coils (43) wound around the stator cores (42). End faces (32a, 32b) of each of the rotor cores (32) and end faces (42a, 42b) of the corresponding stator core (42) are opposed to each other while being exposed to each other.