In-Line Stator Terminals for Compact High-Power Brushless Motors
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Solution Overview
Problem
Existing brushless DC motor designs for power tools are too large to fit within a gripping handle due to their diameter being greater than 40 mm, and previous solutions using AC power sources or segmented stators are inefficient and prone to noise and vibration.
Innovation Solution
A compact brushless DC motor design with a stator core diameter of less than or equal to 34 mm, featuring a single-piece stator, permanent magnets, and a rotor shaft, along with a routing insulator and stator terminals that facilitate electrical connections and insulation, allowing for high power output within a smaller form factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a brushless DC motor is designed to output high power for power tool applications, then the power output is improved, but the motor diameter becomes greater than or equal to 40 mm making it unsuitable for gripping handle placement
Solution Approach 1:
The patent changes key design parameters including reducing the stator core diameter to 34 mm or less, optimizing the rotor diameter to 16 mm or less, and adjusting the axial length to maintain high power density. These parameter changes enable the motor to fit within gripping handles while maintaining high power output capability through improved magnetic circuit design and winding configurations.
2Length of stationary object
If an AC power source is used in a brushless motor for a gripping tool, then the motor can be sized for the gripping portion, but it is incapable of producing the same output levels from a smaller-voltage DC power source
Solution Approach 1:
The patent optimizes the motor's electrical parameters including wire gauge, winding turns, and magnetic circuit design to maximize power output from DC power sources. The stator windings are configured with specific resistance and inductance values, and the rotor magnets are positioned to create optimal magnetic flux density, enabling the motor to achieve high power output from compact DC battery packs typically used in power tools.
3Ease of manufacture
If a segmented stator design is used to form stator windings, then the motor can be manufactured, but it is expensive and prone to high noise and vibration in high torque applications
Solution Approach 1:
The patent merges the segmented stator components into a single integrated stator core with pre-formed winding slots. The stator core includes a yoke and multiple teeth formed as one piece, with stator windings directly embedded in the slots. This integration eliminates gaps and misalignments between segments, reducing magnetic flux leakage and mechanical vibration while maintaining manufacturing feasibility through stamping and welding processes.
4Ease of operation
If the stator terminals extend away from the stator, then electrical connections are facilitated, but the overall motor diameter increases beyond the compact envelope
Solution Approach 1:
The patent nests the stator terminals within the existing motor structure by positioning them at the axial ends of the stator core, extending in the axial direction rather than radially outward. The terminals are integrated with the stator windings and routed through the motor housing, allowing electrical connections to be made without increasing the motor's radial footprint, thus maintaining the compact diameter suitable for gripping handles.
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
The design enables a high-power output of at least 450 watts while fitting within a compact power tool handle, reducing noise and vibration, and maintaining efficiency with a DC power source.
Implementation Method 1
a rotor rotatably received within the stator and including a rotor shaft extending along a longitudinal axis and permanent magnets
Implementation Method 2
stator windings wound from the magnet wire and the magnet wire includes cross-over portions
Data Source
AI summary
A motor is provided including: a stator including a stator core, stator windings, and an end insulator; a rotor rotatably received within the stator; and stator terminals supported by the routing insulator and extending away from the stator. Each stator terminal includes a main body having a curved portion, a tang portion folded over the main body and receiving a portion of a magnet wire therein to make an electrical connection with at least one of the stator windings, and a terminal pin projecting axially away from the stator core. The stator core has a maximum diameter of less than or equal to approximately 34 mm defining an outer envelope of the stator, and the stator terminals are fully contained within the outer envelope.