Vehicle Motor Cover Air Gap Design

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Solution Overview

Problem

Conventional surface-mounted permanent magnet (SPM) motors experience reduced torque density due to increased air gaps caused by molding, which increases the distance between the permanent magnet and the stator.

Innovation Solution

The motor design sets the distance between the cover and the stator equal to the distance between the magnet and the stator, with a shaft member having a separation prevention member and a cover that fixes the magnet, allowing for a consistent air gap and improved torque density by maintaining the magnetic and mechanical air gaps equal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If molding is used to cover the permanent magnet, then the magnet is protected and fixed, but the air gap between the magnet and stator increases, reducing torque density

Engineering Contradiction:

Improvemagnet protection and fixationVSAvoidtorque density

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

A cover is introduced as an intermediary component between the magnet and stator. The cover is designed with a specific thickness that compensates for the space occupied by molding, ensuring that the outer surface of the cover maintains the same distance from the stator as the magnet would have without molding. This resolves the contradiction by allowing magnet protection through molding while preventing torque density reduction.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The thickness of the cover is specifically designed and adjusted as a parameter to compensate for the presence of molding. By changing the cover thickness parameter, the total air gap distance is maintained at the optimal value, thereby preserving torque density while enabling the use of molding for magnet protection and fixation.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the air gap is increased for magnet protection, then the magnet is better protected, but the magnetic flux and torque density are reduced

Engineering Contradiction:

Improvemagnet protectionVSAvoidtorque output

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The cover serves as a mediator that provides magnet protection without increasing the functional air gap. By positioning the cover's outer surface at the same distance from the stator as the magnet's outer surface would be without molding, the magnetic flux path is preserved while still providing mechanical protection.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The protection function is segmented between the molding (which protects the magnet from damage) and the cover (which maintains the correct air gap distance). This segmentation allows each component to fulfill its specific function without compromising the other, protecting the magnet while maintaining torque output.

Inventive Principle:

Principle #1Segmentation

3Reliability

If a cover is added to fix the magnet, then the magnet positioning is improved, but the motor weight and volume increase

Engineering Contradiction:

Improvemagnet positioningVSAvoidmotor weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The cover is designed to perform multiple functions simultaneously: it provides mechanical protection for the magnet, maintains precise positioning, and controls the air gap distance. By consolidating these functions into a single component, the need for additional separate parts is eliminated, thereby avoiding excessive weight and volume increase.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The cover integrates the functions of protection, positioning, and air gap control that would otherwise require separate components. By merging these functions into one element, the overall motor weight and volume are minimized while still achieving reliable magnet fixation and protection.

Inventive Principle:

Principle #5Merging (Combining)

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 torque density and reduces weight, volume, and manufacturing costs by ensuring a consistent air gap, thereby improving the motor's performance and efficiency.

Implementation Method 1

a coil for generating magnetism using electricity

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

magnetic torque is generated by the permanent magnet

Methodology Applied

Scientific EffectMagnetic torque: Magnetic Field

Implementation Method 3

reluctance torque is generated by the structure of the rotor

Methodology Applied

Scientific EffectReluctance torque: Magnetic Reluctance

Data Source

PatentUS11569720B2Motor for vehicle

Publication Date: 2023.01.31 HYUNDAI MOBIS CO LTD

AI summary

A motor for a vehicle may include: a shaft member rotatably installed; a magnet attached to the outside of the shaft member; a cover covering the magnet, and fixing the magnet on the shaft member; and a stator disposed outside the cover and the magnet. A distance between the cover and the stator may be equal to a distance between the magnet and the stator.