BLDC Stator Terminal Assembly for Compact Power Tool Motors
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Solution Overview
Problem
Existing cordless power tools driven by Permanent Magnet (PM) brushed motors face challenges in durability, efficiency, and compact design due to the mechanical commutation system, which leads to wear and tear, inefficiency, and increased length of the motor.
Innovation Solution
A brushless DC motor with a stator assembly that includes a lamination stack defining poles, field windings connected at opposite poles, and a bus bar with conductive terminals arranged along the outer surface of the lamination stack, which simplifies the motor winding process and reduces the overall length of the stator assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PM brushed motor with mechanical commutation is used, then the motor structure is conventional and easier to manufacture, but the brushes suffer from wear and tear reducing durability
Solution Approach 1:
The patent replaces the mechanical commutation system (brushes and commutator) with an electronic commutation system using Hall effect sensors and a control circuit. This substitution eliminates mechanical wear and tear on brushes, thereby improving durability and reliability while removing the limiting factor of brush lifespan.
Solution Approach 2:
The patent introduces Hall effect sensors as intermediary devices to detect rotor position and enable electronic commutation. These sensors act as mediators between the rotor magnets and the control circuit, allowing the system to switch stator windings electronically without mechanical contact, thus eliminating brush wear.
2Use of energy by moving object
If a PM brushed motor is used, then the motor can be manufactured with conventional methods, but the mechanical commutation system reduces energy efficiency
Solution Approach 1:
The patent replaces the mechanically inefficient brush-commutator system with an electronically controlled commutation system. This eliminates friction and electrical contact losses inherent in mechanical commutation, thereby improving energy efficiency while maintaining the ability to manufacture the motor with modern techniques.
3Reliability
If a brushless DC motor with conventional stator winding is used, then the motor achieves improved durability, but the winding process becomes complex and time-consuming
Solution Approach 1:
The patent segments the stator winding into discrete coils connected to a multi-terminal bus bar structure. This segmentation allows for standardized, pre-fabricated coil assemblies that can be systematically connected, greatly simplifying the winding and assembly process while maintaining the brushless motor's durability advantages.
Solution Approach 2:
The patent introduces a multi-terminal bus bar as an intermediary component that simplifies the connection of stator coils. This bus bar structure provides organized electrical connections and facilitates the winding process by serving as a centralized connection point, reducing manufacturing complexity while preserving the electronic commutation benefits.
4Use of energy by moving object
If a brushless DC motor with traditional stator assembly is used, then the motor improves efficiency, but the overall length of the motor increases
Solution Approach 1:
The patent merges the stator core, stator windings, and bus bar structure into a more compact integrated assembly. By combining these components and optimizing their spatial arrangement, the design reduces the overall motor length while maintaining the efficient electronic commutation system that provides improved energy efficiency.
Solution Approach 2:
The patent optimizes the three-dimensional arrangement of stator components, particularly the bus bar and winding layout, to reduce the axial length of the motor. By reconfiguring components in different spatial dimensions and improving packing efficiency, the design achieves compactness without compromising the efficiency benefits of brushless operation.
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 brushless DC motor design enhances durability, efficiency, and compactness by minimizing mechanical wear, improving energy efficiency, and reducing the motor's length, making it suitable for high-torque applications in handheld power tools.
Implementation Method 1
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.
Implementation Method 2
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.
Data Source
AI summary
A stator assembly for a BLDC motor includes a stator core, at least one magnet wire wound on poles of the stator core, an end insulator mounted on an end surface of the stator core, a non-conductive mount member mounted on the outer circumferential surface of the stator core, and conductive terminals mounted on the non-conductive mount member. Each conductive terminal includes: a main portion mounted on the non-conductive mount, a tang portion extending from a first longitudinal end adjacent the end insulator and folded over the main portion, and a connection tab extending angularly from a second longitudinal end. A contact portion of the magnet wire is wrapped around the tang portion and fused to make an electric connection to the conductive terminal.