Brushless Motor Stator Layout for Compact Power Tool Assembly
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Solution Overview
Problem
Cordless power tools driven by conventional brushed motors face issues with durability, efficiency, and cost due to brush wear and tear, and complex assembly processes, while brushless DC motors offer advantages but are expensive and challenging to manufacture, especially in compact designs for hand-held tools.
Innovation Solution
A brushless DC motor design for power tools with a stator and rotor arrangement, including Hall sensors and optimized stator winding configurations, and a compact control unit placement within the handle to reduce size and complexity, along with improved heat management and assembly alignment features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brushless DC motor is used instead of brushed motor, then durability and efficiency are improved, but manufacturing cost and complexity increase
Solution Approach 1:
The patent integrates the control circuit board directly into the motor assembly, merging the control electronics with the motor structure. This integration reduces the number of separate components and simplifies the overall assembly process, addressing the manufacturing complexity issue while maintaining the durability benefits of brushless technology
Solution Approach 2:
The motor assembly is designed to serve multiple functions: the stator assembly provides both magnetic field generation and structural support, while the integrated control circuit board handles both motor control and sensor signal processing. This multi-functionality reduces the need for additional separate components, simplifying manufacturing
2Use of energy by moving object
If brushless DC motor is used instead of brushed motor, then energy efficiency is improved, but device complexity increases
Solution Approach 1:
The motor assembly includes integrated sensors (such as Hall effect sensors) that automatically detect rotor position and provide feedback to the control circuit board. This self-sensing capability eliminates the need for external position detection systems, reducing overall system complexity while maintaining high energy efficiency through precise commutation control
3Volume of moving object
If compact motor design is implemented, then tool size is reduced, but heat management becomes more challenging
Solution Approach 1:
The patent employs a thermally conductive material layer between the stator windings and the motor housing. This thin film material provides an efficient thermal pathway that conducts heat away from the compact motor components to the outer housing, which then dissipates heat to the environment. This approach enables effective heat management in a compact design by utilizing thermal conduction through strategically placed material layers
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 enhances the durability, efficiency, and cost-effectiveness of brushless DC motors for power tools by simplifying assembly, reducing size, and improving thermal performance, while maintaining high performance and reliability.
Implementation Method 1
When power is applied to a winding, the resulting current in the winding generates a magnetic field that couples to the rotor. The magnetic field associated with the PM in the rotor assembly attempts to align itself with the stator generated magnetic field resulting in rotational movement of the rotor.
Implementation Method 2
A set of sense magnets coupled to the PMs in the rotor assembly are sensed by a sensor, such as a Hall Effect sensor, to identify the current position of the rotor assembly.
Data Source
AI summary
A Brushless Direct-Current (BLDC) motor is provided for a power tool, including a stator comprising a set of coils, a rotor configured to rotate with respect to the stator, power supply lines, terminals secured to the stator outer surface of the stator, and a Hall circuit board. The terminals extend axially on the outer surface of the stator. A radial member is oriented radially adjacent a second side of stator proximate an axial end of the of coils, the radial member including a through-hole through which the rotor shaft extends, and discrete conductive routings electrically coupled to the coils and making electric contact with the coils at at least three distinct contact points to electrically connect the coils in a delta configuration.