External Rotor Assembly With Tie Rods for Torque Transfer
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Solution Overview
Problem
Existing rotor designs for external rotor motors face challenges in reliably and cost-effectively transferring torque from the ferromagnetic stack to the carrier while preventing axial movement of the stack relative to the carrier.
Innovation Solution
The use of tie rods that protrude through the carrier and the stack of sheets in the axial direction, with suitable openings created during sheet punching, to pull the stack against the carrier, and the incorporation of removable end pieces on the tie rods to enhance stability and assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tie rods are used to connect the stack of sheets to the carrier, then torque transfer and axial movement prevention are improved, but device complexity increases
Solution Approach 1:
The connection structure is segmented into multiple tie rods distributed around the rotor, each independently connecting the stack to the carrier. This segmentation allows torque to be distributed across multiple connection points, improving reliability while keeping each individual tie rod simple in design.
Solution Approach 2:
The tie rods are pre-installed in the carrier before the stack of sheets is assembled. The openings for the tie rods are created in advance during the carrier manufacturing process, allowing the stack to be simply placed onto the pre-prepared connection structure, thereby reducing overall assembly complexity.
2Ease of manufacture
If tie rod openings are created during sheet punching, then manufacturing cost is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The creation of tie rod openings is merged with the existing sheet punching process. The same punching equipment and tooling used for creating the ferromagnetic sheets themselves is utilized to create the tie rod openings, eliminating the need for separate operations and reducing manufacturing costs.
Solution Approach 2:
The punching process serves multiple functions: it creates the ferromagnetic sheets, forms the tie rod openings, and establishes precise alignment features all in one operation. This multi-functionality reduces the need for additional specialized equipment or processes.
3Ease of operation
If end pieces are made removable, then ease of assembly and disassembly is improved, but device complexity increases
Solution Approach 1:
The end pieces are designed with threaded holes that allow them to be dynamically adjusted or removed after initial installation. This dynamic feature enables easy maintenance and assembly/disassembly operations while the threaded connection provides a simple, standardized structure rather than a complex mechanism.
Solution Approach 2:
The threaded holes in the end pieces act as intermediaries that simplify the connection between the tie rods and the stack/carrier assembly. Instead of requiring complex locking mechanisms, the threaded interface provides a simple, standardized way to attach and detach end pieces.
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 effectively transfers torque and prevents axial movement, ensuring reliable operation while maintaining cost-effectiveness by utilizing existing sheet punching processes to create tie rod openings.
Implementation Method 1
the tie rods can be designed as pins which protrude through these openings in the sheets and matching openings in the carrier and have an end piece at at least one end which is wider than the channel formed by the openings
Data Source
AI summary
A rotor for an external rotor motor is described, comprising a stack of annular sheets made of steel, permanent magnets which are attached to an inner side of the stack of sheets, and a carrier which has a hub for a shaft and is attached to the stack of sheets. Tie rods are provided which project in the axial direction through the carrier and the stack of sheets and pull the stack of sheets against the carrier.