Motor Casing Contact Area Reduction for Axial Strength and Noise Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing motor driving devices for electric power steering systems face challenges in achieving sufficient mechanical strength in the axial direction while minimizing noise generated by vibration, particularly due to the difficulty in uniformly contacting the cover member with the motor housing, which can lead to noise and reduced mechanical strength.
Innovation Solution
The proposed driving device consists of a cylindrical casing with a bearing holding portion, an electric rotating machine, and a frame member, where the casing and frame member are designed with specific contacting portions to reduce the contact area, allowing for increased mechanical strength and reduced noise. The frame member is made of high thermal conductivity materials like aluminum for effective heat dissipation, and the casing is made of soft magnetic materials to minimize magnetic flux leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cover member is brought into contact with the motor housing at its whole surface area to increase mechanical strength, then mechanical strength in the axial direction is improved, but noise may be generated by vibration due to difficulty in uniform contact
Solution Approach 1:
The patent applies local quality by transitioning from uniform full-surface contact to localized contact through protrusions. The cover member and motor housing each have protrusions that create discrete contact points, concentrating the mechanical strength function at specific locations while reducing vibration-induced noise across the overall contact interface.
Solution Approach 2:
The contact interface is segmented into multiple discrete contact points formed by protrusions rather than a continuous full-surface contact. This segmentation allows the system to achieve sufficient mechanical strength through concentrated contact points while reducing the area susceptible to vibration-induced noise.
2Weight of moving object
If the cover member is made of thin metal plate to reduce weight, then weight is reduced, but mechanical strength in the axial direction becomes insufficient
Solution Approach 1:
The thin metal plate cover member compensates for its reduced weight by implementing local quality through protrusions. These localized structural features concentrate mechanical strength at critical contact points, allowing the overall component to remain lightweight while maintaining sufficient axial strength through strategically positioned reinforcement.
3Object-affected harmful factors
If the contact area between casing and frame member is reduced to reduce noise, then noise from vibration is reduced, but mechanical strength may be compromised
Solution Approach 1:
The frame member and casing implement local quality by featuring protrusions that create localized contact areas. This design concentrates mechanical strength at specific protrusion contact points while minimizing the overall contact area, thereby reducing the surface from which vibration-induced noise can originate while maintaining structural integrity.
Solution Approach 2:
The contact interface between frame member and casing is segmented into discrete contact points through protrusions. This segmentation reduces the continuous contact area that generates noise while concentrating load-bearing capacity at the segmented contact points, simultaneously achieving noise reduction and maintaining mechanical strength.
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 mechanical strength in the axial direction, reduces noise from vibrations, and allows for precise assembly and effective heat management, improving the overall performance and robustness of the motor driving device.
Implementation Method 1
when the frame member is made of material having high thermal conductivity, such as aluminum, it is possible to effectively radiate heat generated in the control unit
Implementation Method 2
when the casing is made of soft magnetic material, such as iron, it is possible to reduce leakage of magnetic flux from the electric rotating machine
Data Source
AI summary
A motor casing of a driving device has a cylindrical wall portion, a bottom wall portion and a bearing holding portion formed in the bottom wall portion. An electric motor has a stator, a shaft and a rotor. A motor control unit controls operation of the electric motor. A first frame, to which the motor control unit is fixed, is provided between the motor control unit and the bottom wall portion of the motor casing. A first contacting portion is formed in the bottom wall portion and projected toward the first frame. The first contacting portion is in contact with the first frame at a front-side surface of the first contacting portion. A contacting surface area between the motor casing and the first frame is limitedly reduced, to thereby reduce noise caused by vibration. In addition, since a sufficient surface pressure can be obtained, strength of the driving device in its axial direction is increased.