External Rotor Bracket Assembly for Variable Stack Lengths
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Solution Overview
Problem
Existing methods for attaching the carrier to the stack of sheet metal in external rotor motors are costly and lack flexibility in accommodating varying stack lengths.
Innovation Solution
The use of brackets formed from two sheet metal strips with angled ends, which are welded to each other and the stack, providing a cost-effective and flexible attachment method that maintains a preload on the stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional attachment methods are used to attach the carrier to the stack of sheet metal, then reliable attachment is achieved, but the manufacturing cost increases
Solution Approach 1:
The bracket is divided into two separate sheet metal strips instead of a single monolithic component. These strips can be manufactured independently and then joined together, simplifying the manufacturing process and reducing costs while maintaining attachment reliability through the distributed welding approach.
Solution Approach 2:
The invention uses simple sheet metal strips as brackets rather than complex or expensive attachment components. The strips are welded directly to the stack, creating a cost-effective solution that achieves reliable attachment without requiring expensive specialized fasteners or complex assembly processes.
2Reliability
If brackets extend over the entire axial length of the stack, then complete coverage is achieved, but the manufacturing complexity and material usage increase
Solution Approach 1:
The sheet metal strips are designed to extend only partially along the axial length of the stack, specifically from the carrier to beyond the center of the stack. This partial coverage is sufficient to maintain the preload and ensure reliable attachment, while reducing material usage and manufacturing complexity compared to full-length brackets.
3Reliability
If welding is performed over the entire axial length of the stack, then complete bonding is achieved, but the magnetic properties of the stack are more significantly impaired
Solution Approach 1:
The welding is performed only in specific local areas where the sheet metal strips contact the stack, rather than along the entire axial length. This localized welding approach provides sufficient bonding strength at the critical attachment points while minimizing the total welded area, thereby reducing the overall impact on the soft magnetic properties of the electrical steel stack.
4Power
If the stack axial length is increased to meet performance requirements, then motor performance improves, but the bracket design and welding complexity increase
Solution Approach 1:
The sheet metal strip bracket design is universal and can be used for stacks of varying axial lengths. By positioning the strips from the carrier to beyond the center of the stack, the same basic bracket configuration works for different stack lengths, allowing motor performance to be optimized through stack length variation without requiring complex or customized bracket designs for each application.
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 solution allows for reliable and cost-effective attachment of the stack to the carrier, accommodating varying stack lengths while maintaining mechanical stability and minimizing impact on the soft magnetic properties of the stack.
Implementation Method 1
the brackets each comprise two sheet metal strips, each of which has an angled end section, lie next to each other on the outside of the stack and are welded to each other and/or to the stack
Implementation Method 2
The welding melts the material of the stack locally and generally changes the microstructure of the material there
Implementation Method 3
the stack is pressed against the carrier in an axial direction by brackets that rest against an outer side of the stack
Data Source
AI summary
A rotor for an external rotor motor is described, with an annular stack of sheets made of steel, permanent magnets which are fastened to an inner side of the stack of sheets, and a carrier which has a hub for a shaft and is fastened to the stack of sheets. Brackets are arranged on an outer side of the stack of sheets and press the stack of sheets against the carrier in the axial direction. In addition, a method for manufacturing a rotor for an external rotor motor is disclosed.