BLDC Stator Terminal Layout for Shorter Power Tool Motors
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Solution Overview
Problem
Conventional brushed motors in cordless power tools face durability and efficiency issues due to brush wear and tear, and the complexity of commutation systems, which limits their performance and size efficiency, especially in compact handheld applications.
Innovation Solution
A brushless DC motor with a stator assembly featuring a lamination stack, field windings, and a bus bar system with conductive terminals and insulators, which simplifies the connection of stator windings and reduces the motor's overall length by eliminating the need for a commutator and brush system, enhancing durability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a brushed motor with commutator and brush system is used, then commutation can be achieved mechanically, but the motor suffers from brush wear and reduced 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. The sensors detect rotor position and the control circuit switches current to stator windings electronically, eliminating mechanical contact and brush wear while maintaining commutation functionality.
Solution Approach 2:
The patent introduces Hall effect sensors as intermediaries to detect rotor position and provide feedback to the control circuit. These sensors enable the electronic commutation system to determine when to switch current to different stator windings, replacing the direct mechanical contact function of brushes.
2Use of energy by moving object
If a brushless DC motor design is implemented, then energy efficiency and durability improve, but the stator assembly length increases
Solution Approach 1:
The patent merges the Hall effect sensors, control circuit, and stator windings into an integrated stator assembly design. The control circuit is positioned within the stator housing and electrically connected to the stator windings, consolidating multiple components into a compact arrangement that reduces overall length while maintaining brushless efficiency.
Solution Approach 2:
The patent arranges the stator windings and control components in a three-dimensional configuration within the stator housing, utilizing vertical and radial spaces rather than only linear extension. This dimensional optimization allows the brushless motor components to be compacted without sacrificing energy efficiency or cooling capability.
3Reliability
If a brushless motor eliminates the commutator and brush system, then mechanical failures are minimized, but the motor length increases due to extended stator assembly
Solution Approach 1:
The patent consolidates the control circuit, Hall effect sensors, and stator windings into an integrated stator assembly, eliminating the need for separate commutator and brush assemblies. This merging of functions into a single housing reduces the overall motor length while maintaining the mechanical failure resistance of brushless design.
Solution Approach 2:
The stator housing serves multiple functions: it provides structural support, houses the control circuit, mounts the Hall effect sensors, and provides thermal management pathways. This multi-functionality eliminates the need for separate dedicated components, reducing motor length while maintaining reliability.
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 improves durability and energy efficiency, reduces motor length for compact applications, and minimizes mechanical failures, enabling longer tool operation and higher torque output without stalling.
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.