Brushless DC Motor PCB Layout for Compact Power Tool Assembly
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Solution Overview
Problem
Brushless motor power tools face complexity in wiring layouts and assembly due to separate printed circuit boards (PCBs) for various components, leading to increased size, reduced flexibility in design, and potential thermal management issues.
Innovation Solution
A combined surfboard PCB layout that integrates FETs, motor control unit, and forward/reverse switch, along with a heat sink, to reduce wiring complexity and enhance thermal management by exposing components for better cooling, allowing for more compact and flexible tool designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If separate printed circuit boards (PCBs) are used for various components, then component functionality is achieved, but wiring complexity and assembly complexity increase
Solution Approach 1:
The patent combines multiple separate PCBs into a single integrated PCB that houses all control electronics including the motor control unit, FETs, and other components. This merging eliminates the need for complex wiring between separate boards and simplifies assembly operations.
2Temperature
If traditional motor mounting is used, then motor functionality is achieved, but thermal management effectiveness is reduced
Solution Approach 1:
The patent integrates the heat sink directly with the motor mounting structure, combining thermal management functionality with the mechanical mounting system. This eliminates the need for separate thermal management components and simplifies the overall assembly.
Solution Approach 2:
The patent introduces a thermal interface material or direct thermal coupling between the motor and heat sink to improve heat transfer efficiency. This intermediary mechanism enhances thermal management while maintaining a relatively simple mounting structure.
3Volume of moving object
If compact design is pursued, then tool size is reduced, but wiring layout flexibility is reduced
Solution Approach 1:
The patent integrates all control electronics onto a single PCB that is mounted directly within the motor housing, eliminating the need for extensive wiring layouts. This consolidation enables compact tool design while maintaining full functionality.
4Power
If FETs are cooled effectively, then current handling capability is improved, but thermal management system complexity increases
Solution Approach 1:
The patent integrates the FETs directly onto the PCB that is thermally coupled to the heat sink, combining power handling components with the thermal management system. This integration enables effective cooling of high-current components without requiring complex separate thermal management systems.
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 combined surfboard PCB layout reduces assembly complexity, enables more compact designs, improves thermal management, and allows for higher current levels and torque output by effectively cooling FETs, thus enhancing the performance and usability of brushless motor power tools.
Implementation Method 1
The heat sink and the annular metal end piece are secured together to clamp the brushless DC motor, thereby rigidly coupling the heat sink to the brushless DC motor
Implementation Method 2
improves thermal management by exposing components for better cooling
Data Source
AI summary
A power tool with a combined printed circuit board (PCB) having a doughnut shape and located coaxially with a motor shaft. The combined PCB is secured to a heat sink on one end of the motor and a metal end piece is positioned on an opposite end of the motor. The metal end cap and heat sink are secured to one another via fasteners to provide a rigid coupling. A tabbed end piece is provided between the heat sink and the motor stator and is also secured into place via the fasteners. The tabbed end piece includes wire support tabs that provide strain relief to motor coil leads. The wire support tabs extend axially from circumferential locations of the tabbed end piece and include channels to guide the motor coil leads to solder contact points on the combined PCB.