Stepped Injection Channel for Stator Plastic Coating
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Solution Overview
Problem
Current injection molding processes for stator/rotor devices in electric motors face limitations in achieving large package heights with minimal wall thickness, leading to weld line and air pocket issues that compromise insulation quality and mechanical integrity, particularly in thin-walled winding groove areas.
Innovation Solution
The design incorporates a stator/rotor device with alternating first and second recesses on individual laminations, forming a continuous stepped injection channel that allows for extended flow paths and flexible sheet metal cutting patterns, enabling the creation of injection channels without completely penetrating pole elements, thus avoiding weld lines and air pockets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If injection molding process is used to create plastic coating on stator/rotor devices, then electrical insulation and mechanical support are improved, but weld lines and air pockets form in thin-walled winding groove areas compromising insulation quality
Solution Approach 1:
The injection molding process is divided into multiple sequential injection stages, with each stage targeting specific regions of the stator/rotor device. This segmentation allows thick-walled areas to be filled first and cooled, then thin-walled winding groove areas to be filled in subsequent stages with controlled pressure and temperature, preventing weld lines and air pockets from forming in critical insulation regions
Solution Approach 2:
Mold inserts with cooling channels and temperature control systems are pre-installed before injection molding begins. The mold is pre-cooled to optimal temperatures and pressure control systems are pre-configured to deliver staged injection profiles, ensuring that when plastic is injected into thin-walled winding groove areas, the conditions are already optimized to prevent defects
2Productivity
If package height is increased to improve motor performance, then power density is improved, but structural integrity and insulation quality deteriorate due to longer flow paths causing weld lines and air pockets
Solution Approach 1:
Instead of increasing package height in a single vertical dimension, the design distributes injection channels and molding stages across multiple dimensional planes. Multiple injection points are positioned at different heights and radial positions, allowing the plastic to flow through shorter paths in each direction while still achieving complete coverage of tall stator/rotor packages, thereby maintaining structural integrity
Solution Approach 2:
The injection molding process for tall packages is segmented into multiple stages with different injection pressures, temperatures, and flow rates for different height zones. Lower sections are filled and cooled first, then upper sections are filled in subsequent stages, preventing air entrapment and weld line formation even in high-power-density designs with large package heights
3Productivity
If wall thickness is minimized to increase copper wire filling in winding grooves, then motor efficiency is improved, but mechanical strength and insulation reliability deteriorate due to formation of weld lines and air pockets
Solution Approach 1:
Injection molding parameters such as temperature, pressure, and injection rate are dynamically adjusted based on wall thickness. For thin-walled winding groove areas, lower injection pressures and slower injection rates are used to allow proper filling without trapping air or forming weld lines. Mold temperature is locally controlled to optimize filling behavior in thin sections while maintaining mechanical strength
Solution Approach 2:
Different regions of the stator/rotor device receive different injection conditions tailored to their specific wall thickness and functional requirements. Winding groove areas with minimal wall thickness receive low-pressure, slow-fill injection to prevent defects, while thicker structural areas receive higher pressure for complete filling, ensuring both mechanical strength and insulation reliability are maintained
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 enables reliable, high-quality plastic coating with improved mechanical and electrical insulation, allowing for increased package heights while maintaining structural integrity and reducing the risk of defects like weld lines and air pockets.
Implementation Method 1
The stator/rotor stack devices are coated with plastic in an injection molding process
Data Source
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AI summary
A stator/rotor device for electric motors having at least one or more stator/rotor stack assemblies stacked one above the other, characterised in that the stator/rotor stack assembly has at least one first lamination sub-stack (54) and at least one second lamination sub-stack (56) arranged on the upper side or lower side of the first lamination sub-stack, each lamination sub-stack comprising a plurality of individual laminations (12.21) which are arranged one above the other and which, in the outwardly/inwardly facing inner region of the base of the winding groove (16), each comprise at least one first and one second outwardly/inwardly open recess (50/52) having a first/second depth (t1/t2) in the radial direction (r), the first recesses (50) of each individual lamination of the first/second lamination sub-stack (54/56) being arranged congruently one above the other, the first and second lamination sub-stacks (54, 56) being arranged relative to one another such that the first and second recesses (50, 52) are arranged at the same circumferential angular position and the depths (t1) and (t2) of the first and second recesses (50, 52) are of such a size that some regions of the first and second recesses (50, 52) overlap, when viewed in a plan view, thus forming a stepped injection channel (28), running continuously from the interior outwards or from the exterior inwards, for the plastic coating (18).