Electric Machine Rotor Pole Piece Axial Coil Locking
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Solution Overview
Problem
Conventional alternator rotor designs face issues with field coil movement due to engine speed variations, leading to coil failures, and existing locking solutions compromise magnetic saturation, heat transfer, and cost efficiency.
Innovation Solution
The design incorporates pole pieces with a finger support structure and axial protrusions or depressions to axially compress and deform the coil, ensuring rotational fixation without radial deformation, allowing for various coil sizes and improved heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If locking features (protrusions or epoxy fillers) are used to prevent field coil rotation, then coil stability is improved, but magnetic saturation increases and heat transfer deteriorates
Solution Approach 1:
The invention transitions from radial locking features to axial locking features. Instead of using protrusions extending radially from the pole pieces, the patent uses axial extensions of the pole fingers that contact the coil assembly in the axial direction. This dimensional change eliminates the need for thick radial protrusions, improving heat transfer paths while maintaining rotational stability through axial interference fit and deformation.
2Stability of the object's composition
If locking features are used to prevent field coil rotation, then coil stability is improved, but power density decreases
Solution Approach 1:
By moving the locking mechanism from the radial dimension to the axial dimension, the invention eliminates the need for thick radial protrusions that consume valuable space. The axial extensions of pole fingers provide effective locking without reducing the radial space available for field coils, thereby maintaining higher power density while ensuring coil stability.
3Stability of the object's composition
If interference between pole fingers and coil windings is used to prevent rotation, then coil stability is improved, but manufacturing flexibility decreases
Solution Approach 1:
The axial extensions of the pole fingers serve multiple functions: they provide the primary locking action to prevent coil rotation, guide the coil assembly during installation, and accommodate variations in coil dimensions. This universal design allows the same pole piece structure to work with different coil sizes and configurations, improving manufacturing flexibility while maintaining effective rotational prevention.
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 prevents field coil movement, enhances heat transfer, reduces magnetic saturation, and offers cost savings by allowing interchangeable pole pieces and improved durability.
Implementation Method 1
at least one of a protrusion or a depression having an axial component of extension relative to the coil contact surface... axially compress and deform the coil, ensuring rotational fixation without radial deformation
Implementation Method 2
enhances heat transfer... preventing good heat transfer from the coil to the cooler poles
Data Source
AI summary
The apparatus disclosed herein relates to a pole piece for an electric machine comprising, a pole piece with a finger support structure, a plurality of fingers having an axial component of extension relative to the finger support structure, a coil contact surface and at least one of a protrusion or a depression having an axial component of extension relative to the coil contact surface. Further disclosed is a method that relates to assembling a coil to pole pieces comprising, axially compressing a coil between coil contact surfaces of a pair of opposing pole pieces and deforming the coil axially and without radial deformation with at least one of protrusions and depressions in the coil contact surfaces of the pole pieces thereby rotationally fixing the coil to the pole pieces.