Two-Piece End Ring for Motor Stator Power Density
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Solution Overview
Problem
Conventional power tools face limitations in increasing motor output power without compromising ergonomics or increasing tool size, as higher motor speeds lead to vibration and gear stress, and extending stator stack length or armature diameter results in cumbersome tools.
Innovation Solution
A method for forming a stator with field coils wound to a predetermined shape, using bondable magnet wires and encapsulating them with elastomeric thermoplastic or thermoset plastic for enhanced abrasion protection and packing density, allowing the coils to extend beyond pole tips and be assembled with a two-piece end ring for improved thermal characteristics and power output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If motor speed is increased to boost output power, then power output increases, but vibration levels increase and gear stress increases
Solution Approach 1:
The patent changes the physical parameters of the motor by increasing stack length and armature diameter, which allows power output to increase without requiring higher motor speeds, thereby avoiding the harmful effects of increased vibration and gear stress
2Power
If stator stack length is increased to increase motor output power, then power output increases, but tool length increases making it cumbersome to use
Solution Approach 1:
The patent transitions from increasing power through speed (one dimension) to increasing power through stack length and armature diameter (other dimensions), allowing power increase while maintaining acceptable tool length for ergonomics
3Power
If armature diameter is increased to increase motor output power, then power output increases, but stator diameter increases adversely affecting ergonomics
Solution Approach 1:
The patent optimizes the relationship between armature diameter and stator diameter by using a smaller stator diameter with a proportionally larger armature diameter, achieving higher power output while improving ergonomics through reduced overall motor size
4Stability of the object's composition
If magnet wires are bonded with heat activated adhesive, then coil stability increases, but thermal management becomes more challenging
Solution Approach 1:
The patent utilizes the phase transition of thermoplastic adhesive from solid to molten state during heat treatment, allowing the adhesive to flow and penetrate between magnet wires, then re-solidifies to create strong mechanical interlocking and stable bonding
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 approach enables a higher slot fill factor and packing density, resulting in at least 10% more output power with better thermal management, allowing for a smaller stator diameter for the same power or maintaining power with a reduced stator diameter, and improving tool ergonomics by reducing size and weight.
Implementation Method 1
Bondable magnet wires are magnet wires layered with a heat activated thermoplastic or thermoset polymer adhesive
Implementation Method 2
encapsulating them with elastomeric thermoplastic or thermoset plastic for enhanced abrasion protection
Data Source
Figure 1~2
Figure 3~3A
Figure 3B
AI summary
A power tool is provided including a housing and an electric motor disposed in the housing. The motor includes a stator having a lamination stack having separately-formed pole pieces and field coils disposed on the pole pieces, and an armature disposed in the stator. An end ring is disposed at an end of the lamination stack, the end ring including at least two ring pieces mated together around a portion of the field coils extending beyond pole tips of the pole pieces.