Consequent Pole Rotor Layout for Lighter Power Tool Motors
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Solution Overview
Problem
Existing power tool motors face challenges in achieving efficient performance and mass reduction while maintaining torque and speed capabilities, particularly in designs that incorporate permanent magnets and lamination stacks.
Innovation Solution
The implementation of a consequent pole motor design featuring a rotor with a lamination stack, rare earth permanent magnets, and non-magnetic consequent poles, along with injection molded air gaps and axial support structures, which allows for a reduction in magnet mass without compromising performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If traditional internal permanent magnet motor design is used, then torque and speed capabilities are maintained, but mass is higher
Solution Approach 1:
The patent extracts the magnetic flux path function from the permanent magnets themselves by introducing separate consequent poles. The permanent magnets are positioned only to generate flux, while the consequent poles (made of non-magnetic material) form the actual magnetic circuits and flux paths. This separation allows reduction of permanent magnet material while maintaining motor performance.
Solution Approach 2:
The rotor employs a composite structure combining permanent magnets with non-magnetic consequent poles. The consequent poles are constructed from non-magnetic materials such as aluminum, aluminum alloys, or aluminum-lithium alloys, creating a hybrid magnetic circuit system that reduces reliance on heavy rare earth magnets while preserving torque generation capability.
2Weight of moving object
If magnet mass is reduced, then motor mass decreases, but performance may be compromised
Solution Approach 1:
The consequent poles act as intermediary elements between the permanent magnets and the air gap. These non-magnetic poles serve as flux conduits that guide and concentrate the magnetic flux generated by reduced-mass permanent magnets, ensuring consistent and reliable performance despite the reduction in magnet material.
Solution Approach 2:
The patent optimizes geometric parameters of the consequent poles (dimensions, positioning, spacing) to compensate for reduced permanent magnet mass. By carefully adjusting these parameters, the magnetic circuit is tuned to maintain flux density and distribution, ensuring performance consistency across the motor's operating range.
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 design achieves a significant mass reduction of up to 36% compared to traditional internal permanent magnet motors while maintaining similar performance within target operating regions, indicating improved efficiency and output power.
Implementation Method 1
The motor includes a stator including a plurality of stator teeth configured to receive a plurality of stator windings, and a rotor configured to rotate with respect to the stator. The rotor includes a first permanent magnet within the rotor, a second permanent magnet within the rotor
Implementation Method 2
The consequent pole is located between the first permanent magnet and the second permanent magnet. The consequent pole has a length and a width. The consequent pole is made of a non-magnetic material
Data Source
AI summary
A power tool including a battery pack interface and a consequent pole motor. The battery pack interface is configured to receive a removable and rechargeable battery pack. The consequent pole motor includes a stator including a plurality of stator teeth configured to receive a plurality of stator coils, and a rotor configured to rotate with respect to the stator. The rotor includes a first permanent magnet positioned within the rotor, a second permanent magnet positioned within the rotor, and a consequent pole located between the first permanent magnet and the second permanent magnet. The consequent pole has a length and a width. The consequent pole is made of a non-magnetic material.