Motor Drive Housing Screw Alignment for Vibration Reduction

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Solution Overview

Problem

Conventional motor drive apparatuses for electric power steering systems face challenges in achieving compact size and low vibration/noise due to design issues such as protruding support members, complex machining requirements, high material costs, and poor rigidity, which lead to increased vibration and noise.

Innovation Solution

The motor drive apparatus features screw holes in the circumferential direction for coupling the frame, heat sink, and housing, ensuring proper alignment and rigidity, with an abutment surface between the housing and heat sink on a single plane intersecting the motor's rotation axis, facilitating easier machining and reducing vibration and noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the support member of the housing protrudes in the direction parallel with the rotation axis of the motor, then the motor can be integrated with the motor drive control apparatus, but the machining becomes difficult and material cost increases

Engineering Contradiction:
Improveintegrated size of motor and control apparatusVSAvoidmachining difficulty and material cost
Core Design Contradiction:
Volume of moving objectVSEase of manufacture

Solution Approach 1:

The invention repositions the abutment surface from a protruding support member structure (parallel to rotation axis) to a surface on the housing that intersects with the rotation axis direction. This dimensional change eliminates the need for complex protruding structures, simplifying machining while maintaining the integrated compact design.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Volume of moving object

If two or more separate components are placed in the axis direction, then the apparatus can be compact, but the assembled components have poor rigidity, increasing vibration and noise

Engineering Contradiction:
Improveapparatus sizeVSAvoidrigidity of assembled components
Core Design Contradiction:
Volume of moving objectVSStability of the object's composition

Solution Approach 1:

The invention merges the motor and motor drive control apparatus into a single integrated unit with a unified housing structure. The frame is coupled to the housing, and the heat sink is coupled to both the frame and housing, creating a rigid assembled structure that reduces vibration and noise while maintaining compact dimensions.

Inventive Principle:
Principle #5Merging (Combining)

3Ease of manufacture

If the position and number of screws for fixing motor frame to housing are not appropriate, then assembly is simplified, but electromagnetic exciting force increases vibration

Engineering Contradiction:
Improveassembly simplicityVSAvoidvibration from electromagnetic exciting force
Core Design Contradiction:
Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The invention provides specific guidance on the local quality of screw hole positioning - the screw holes are arranged at positions that correspond in the circumferential direction between the frame, heat sink, and housing. This localized optimization of screw placement ensures rigid coupling that counteracts electromagnetic exciting force vibrations while maintaining assembly simplicity.

Inventive Principle:
Principle #3Local quality

4Ease of manufacture

If the abutment surface between housing and heat sink is on a single plane intersecting with the rotation axis, then machining is easier and material cost decreases, but sealability must be ensured

Engineering Contradiction:
Improvemachining ease and material costVSAvoidsealability
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The invention incorporates seal members in advance at the coupling interfaces between the frame and housing, and between the heat sink and housing. This preliminary inclusion of sealing elements ensures that the simplified single-plane abutment surface structure maintains reliable sealability while achieving easier machining and lower material costs.

Inventive Principle:
Principle #10Preliminary action

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 enhances the mechanical rigidity of the apparatus, reduces vibration and noise, and allows for a more compact design while minimizing material costs and improving sealability, effectively addressing the limitations of existing systems.

Implementation Method 1

a heat sink 70 for dissipating heat from the power board 41 and the like

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

a heat sink 70 for dissipating heat from the power board 41 and the like

Methodology Applied
Scientific EffectConvection: Convection

Data Source

PatentEP2683061B1Motor drive device
Publication Date: 2020.01.08 MITSUBISHI ELECTRIC CORP
  • EP2683061B1 patent drawingFigure 1
  • EP2683061B1 patent drawingFigure 2
  • EP2683061B1 patent drawingFigure 3

AI summary

A motor drive control apparatus 30, on which a switching element 73 for performing drive control of the motor 10 is mounted, includes: a heat sink 50 placed on the front side or rear side of the motor; and a housing 40 that is coupled to the heat sink and couples the heat sink to the frame or that covers the switching element mounted on the heat sink, and wherein an abutment surface 110 between the housing and the heat sink is located on a single plane intersecting with the direction of the rotation axis of the motor, and screw holes 42 and 52 for coupling the frame, the heat sink and the housing to each other are provided such that the positions in the circumferential direction of the screw holes 42 and 52 correspond to each other.