Wound Wire Rotor Sleeve for Electric Motors
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Solution Overview
Problem
Existing electric motor rotors with permanent magnets and steel sleeves face challenges such as increased inertia, eddy current circulation, and handling difficulties with fiberglass or epoxy yarn sleeves, which complicate production and performance.
Innovation Solution
Adopting a wire winding technique similar to that used for induction or excitation coils, where a conductive metal wire with an insulating layer and heat-adhesive sheath is wound around the rotor core and magnets, with the heat-adhesive material polymerizing to secure the turns and adhere to the core, eliminating the need for a steel sleeve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a steel sleeve is used to enclose the core and magnets, then the magnets are securely held against centrifugal force, but the rotor inertia increases and eddy currents are facilitated
Solution Approach 1:
The patent changes the material parameters of the sleeve from steel to a composite material (fiberglass or aramid yarn embedded in resin). This material substitution maintains the mechanical clamping function while significantly reducing density and inertia, and eliminates electrical conductivity to prevent eddy currents.
Solution Approach 2:
The patent employs composite materials consisting of reinforcing yarn (fiberglass or aramid) embedded in a resin matrix. This composite structure provides the necessary mechanical strength and clamping force to hold magnets against centrifugal force, while the non-conductive resin matrix prevents eddy current circulation and reduces overall density compared to solid steel.
2Strength
If a steel sleeve is used to enclose the core and magnets, then the magnets are securely held, but the manufacturing process becomes complex requiring precise machining of internal and external diameters
Solution Approach 1:
The patent replaces the traditional mechanical machining process with a molding process. Instead of machining the sleeve's internal and external diameters, the composite sleeve is molded directly to the required dimensions, eliminating complex machining operations and reducing manufacturing complexity.
Solution Approach 2:
The patent changes the manufacturing method from mechanical machining to composite molding. This parameter change in the manufacturing process allows the sleeve to be formed directly with the required geometry, eliminating the need for precise machining of internal and external diameters and simplifying the overall manufacturing process.
3Ease of manufacture
If fiberglass or aramid yarn pre-impregnated with resin is used, then the sleeve can be formed, but the wire is difficult to handle and requires extra steps for resin distribution
Solution Approach 1:
The patent applies the resin to the yarn before winding, but optimizes this preliminary impregnation process to ensure proper resin distribution without making the yarn difficult to handle. The resin application is controlled to provide adequate coating while maintaining yarn flexibility and ease of winding.
Solution Approach 2:
The patent adopts the proven wire winding technique from coil manufacturing, where the wire is pre-impregnated with resin in a controlled manner. This established process ensures proper resin distribution and bonding while maintaining ease of handling during the winding operation.
4Strength
If the sleeve thickness is increased to maintain air gap, then the clamping force increases, but the rotor inertia increases further
Solution Approach 1:
The patent uses composite materials with high specific strength (strength-to-density ratio). The fiberglass or aramid yarn embedded in resin provides adequate clamping force with much lower density than steel, allowing sufficient thickness to maintain air gap without excessive weight or inertia increase.
Solution Approach 2:
The patent changes the material density parameter from steel to composite materials. This parameter change allows the sleeve to achieve the required clamping force and air gap maintenance with reduced thickness and significantly lower mass, thereby reducing rotor inertia while maintaining functional requirements.
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 method simplifies the production of electric motor rotors, reduces inertia, prevents eddy currents, and maintains the magnets securely on the core while allowing for easier handling and reduced thermal expansion issues.
Implementation Method 1
heat the wire to fix the turns to each other by adhesion of the portions of outer sheath in contact with each other
Implementation Method 2
the wire comprises a metallic core surrounded by an electrically insulating layer itself covered with an outer sheath of thermo-adhesive material
Implementation Method 3
the sleeve has a lower coefficient of thermal expansion than the core so that the heating of the rotor will lead to an increase in the clamping force exerted by the sleeve on the core
Data Source
Figure 1~4
Figure 5~7
AI summary
The invention relates to a rotor (3) of an electric motor, comprising a core (4), magnets (5) set around the periphery of the core, and a wire (6) with joining coils wound around the core (4) and the magnets (5). The wire (6) comprises a metal core element surrounded by an electrically insulating layer covered, in turn, by an outer sheath consisting of a thermo-adhesive material, the coils being attached to each other by adhesion between the outer sheath portions that are in contact with each other. The invention also relates to a method for producing such a rotor, and to an electric motor comprising such a rotor.