Shape Memory Alloy Rotor Cap for Electric Machine Winding Heads
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Solution Overview
Problem
The existing methods for attaching a rotor cap to the winding head of an electrical machine are either complex and damaging due to high temperatures required for metal caps or require additional components and are not robust when using composite materials, and they do not effectively reduce the susceptibility of fibers to pressure loads.
Innovation Solution
A fiber-reinforced plastic winding head ring with a shape memory material, where the preferred direction of the fibers differs from the shape memory wire, allowing for low-temperature assembly and a strong fastening mechanism using a metallic shape memory alloy, such as nickel-titanium, to reduce fiber susceptibility to pressure loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal rotor cap is used and heated for attachment, then the rotor cap can be securely attached to the winding head, but the high temperatures can damage the winding head and the process becomes complex
Solution Approach 1:
The patent changes the temperature parameter from high (conventional metal cap heating to ~300°C) to low (shape memory alloy activation at lower temperatures), enabling secure attachment without thermal damage to the winding head. The shape memory alloy rotor cap achieves reliable attachment through controlled temperature-induced shape recovery rather than high-temperature heating.
Solution Approach 2:
The patent employs a rotor cap made of composite material (shape memory alloy) that combines the benefits of metal (elasticity, shape memory effect) with resistance to thermal damage. This composite approach allows the cap to be securely attached through shape recovery while avoiding the thermal damage issues associated with conventional metal caps.
2Weight of moving object
If a composite material rotor cap is used, then the weight is significantly reduced, but the cap cannot be shrunk onto the winding head and requires additional fastening components
Solution Approach 1:
The patent utilizes temperature as a control parameter to change the physical state and dimensions of the shape memory alloy rotor cap. By heating the cap to a specific temperature range, the cap undergoes shape recovery and shrinks radially inward, creating a interference fit with the winding head without requiring additional fastening components.
Solution Approach 2:
The patent replaces conventional mechanical fastening systems (screws, clips, or other attachment mechanisms) with a thermal-field-based attachment mechanism. The shape memory alloy's temperature-induced shape recovery replaces mechanical fasteners, simplifying the overall structure while maintaining secure attachment.
3Device complexity
If the preferred direction of fibers aligns with the shape memory wire direction, then the structure is simplified, but the fibers become more susceptible to pressure loads
Solution Approach 1:
The patent introduces asymmetry in the fiber orientation relative to the shape memory wire direction. Instead of aligning fibers parallel to the wire (which would simplify construction but increase pressure susceptibility), the fibers are oriented at an angle, creating an asymmetric reinforcement pattern that better distributes and resists pressure loads while maintaining structural integrity.
Solution Approach 2:
The patent applies local quality optimization by specifically orienting fibers at an angle to the shape memory wire direction in the regions where pressure loads are most critical. This localized fiber orientation strategy provides enhanced pressure resistance where needed while maintaining overall structural simplicity.
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
The solution provides a lightweight, robust, and damage-resistant attachment method that reduces the risk of fiber damage and extends the service life of the winding head by evenly distributing radial forces, eliminating the need for high-temperature processes and minimizing component complexity.
Implementation Method 1
The shape memory material is characterized by the fact that, despite being deformed by heating, it can remember an earlier shape before the deformation and assumes this earlier shape due to heating.
Implementation Method 2
the winding head ring is heated, whereby the winding head ring is shrunk onto the winding head
Data Source
Figure 1~2
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AI summary
The invention relates to a rotor for an electrical machine, comprising a winding overhang and a winding overhang ring (1), which is shrunk onto the winding overhang on the radial outside and which has a shape memory material.