Electric Power Steering Motor Controller Positioning

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Solution Overview

Problem

Conventional electric power steering motors experience vibrations and noises due to the heavy controller being mounted on the side surface, causing the center of gravity to be radially eccentric from the output shaft.

Innovation Solution

The controller is positioned between the coupling and the motor section to surround the output shaft, reducing the eccentricity of the motor's center of gravity and preventing vibrations and noises by minimizing the amplification of electromagnetic forces that deform the stator core into an ellipsoidal shape.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the controller is mounted on the side surface portion of the motor section, then the controller can be easily installed and connected, but the center of gravity of the motor becomes radially eccentric from the output shaft, causing vibrations and noises

Engineering Contradiction:

Improveease of installationVSAvoidvibrations and noises

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The controller is relocated from the radial direction (side surface) to the axial direction (between coupling and motor section), changing the spatial dimension of mounting. This dimensional transition allows the controller to be positioned closer to the rotational axis, reducing radial eccentricity while maintaining installation accessibility through the axial approach.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The controller is strategically positioned to act as a counterweight that balances the rotating assembly. By placing the heavy controller between the coupling and motor section, its weight compensates for the eccentricity of rotating components, reducing the overall radial eccentricity and minimizing vibrations and noises during operation.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

2Object-affected harmful factors

If the controller is positioned to surround the output shaft, then the center of gravity eccentricity is reduced and vibrations are suppressed, but the structural complexity of the motor increases

Engineering Contradiction:

Improvevibrations and noisesVSAvoidstructural complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The controller is integrated with the coupling structure, merging two previously separate components (controller housing and coupling) into a unified assembly. This integration allows the controller to surround the output shaft while utilizing the existing coupling space, thereby reducing structural complexity compared to adding a separate mounting structure.

Inventive Principle:

Principle #5Merging (Combining)

3Device complexity

If the controller is mounted on the side surface, then the motor structure remains simple, but electromagnetic forces deform the stator core into an ellipsoidal shape, amplifying vibrations and noises

Engineering Contradiction:

Improvestructural simplicityVSAvoidstator core deformation

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The controller positioned between the coupling and motor section serves as a counterweight that balances the rotating assembly. By placing the heavy controller in this location, its weight compensates for the eccentricity of rotating components, reducing the overall radial eccentricity and minimizing vibrations and noises during operation.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 effectively suppresses vibrations and noises while maintaining a balanced center of gravity, allowing for efficient torque generation with reduced torque ripple and eddy current loss, enhancing motor performance and reducing costs.

Implementation Method 1

three-phase stator windings obtained by winding conductors around the slots

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

an electromagnetic force for deforming the stator core into an ellipsoidal shape is exerted on the stator core

Methodology Applied

Scientific EffectElectromagnetic force: Lorentz Force

Implementation Method 3

an electromagnetic force for deforming the stator core into an ellipsoidal shape is exerted on the stator core

Methodology Applied

Scientific EffectElectromagnetic force deformation: Lorentz Force

Data Source

PatentUS9035505B2Motor for an electric power steering apparatus

Publication Date: 2015.05.19 MITSUBISHI ELECTRIC CORP

AI summary

Provided is a motor for an electric power steering apparatus, in which vibrations and noises are suppressed. The motor for an electric power steering apparatus includes: a motor section (1) for outputting an assist torque to a handle of a vehicle; and a controller (2) for controlling driving of the motor section (1). The motor section (1) includes: a rotor (14, 14A) having P poles; and a stator (15, 15A) provided so as to surround the rotor (14, 14A), the stator including: a stator core (23) provided with n slots formed thereon and housed in a frame (4); and three-phase stator windings (25) wound around the slots (22). The controller (2) is provided between a boss (18) and the motor section (1) so as to surround the output shaft (12).