Brushless Motor Assembly for Compact Power Tool Handles
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Solution Overview
Problem
Existing brushless DC motors are too large for placement in the gripping handle of power tools, and they struggle to produce high power output from smaller-voltage DC power sources while maintaining compactness and minimizing noise and vibration.
Innovation Solution
A compact brushless DC motor assembly with a single-piece stator and small diameter, featuring a motor housing with a cylindrical body, a stator with a stator core, end insulators, and stator windings, and a rotor with permanent magnets. The motor design includes elastic elements to absorb manufacturing tolerances, ensuring proper assembly and operation within the power tool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a brushless DC motor is designed to output high power, then the power output increases, but the motor diameter becomes greater than or equal to 40mm making it unsuitable for gripping handles
Solution Approach 1:
The patent changes key design parameters including using a single-piece stator construction instead of segmented, optimizing magnetic circuit geometry, and employing specific winding configurations to achieve high power density in a compact diameter under 40mm
Solution Approach 2:
The motor utilizes composite construction combining a single-piece stator core with optimized magnetic materials and winding structures to maximize power output while minimizing diameter, achieving superior power density compared to conventional segmented designs
2Ease 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 stator core and windings into a single-piece construction where the stator core itself is formed with integrated winding paths, eliminating the need for separate segmented stator pieces and reducing noise and vibration while maintaining manufacturability
Solution Approach 2:
The single-piece stator is manufactured using segmented molding or machining processes that are later joined, allowing complex winding geometries to be created without assembling multiple stator segments, thereby reducing vibration while keeping manufacturing feasible
3Volume of moving object
If compact motor components are assembled in small spaces such as a gripping portion, then the motor fits in the tool, but stack-up tolerances become problematic for assembly
Solution Approach 1:
The patent incorporates tolerance compensation features in the design of motor components, such as flexible mounting structures and adjustable positioning elements, that absorb stack-up tolerances before they affect assembly, enabling reliable installation in compact gripping portions
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 compact motor assembly achieves high power output while maintaining a small diameter, reducing noise and vibration, and effectively accommodating manufacturing tolerances, making it suitable for use in power tool gripping handles.
Implementation Method 1
a rotor rotatably received within the stator and including a rotor shaft extending along a longitudinal axis and a plurality of permanent magnets
Implementation Method 2
an elastic element made of elastically deformable material at least partially provided between the rigid body of the end insulator and the inner surface of the motor housing to absorb radial tolerances associated with the stator
Data Source
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AI summary
An electric motor is provided, including a motor housing having a substantially cylindrical body; a stator disposed within the motor housing, the stator including a stator core, a first end insulator mounted to one end of the stator core, a second end insulator mounted to another end of the stator core, and stator windings wound around the stator core and the first and second end insulators; and a rotor rotatably received within the stator and including a rotor shaft extending along a longitudinal axis and a plurality of permanent magnets. The motor housing is fastened to the first end insulator via at least one fastener received into a threaded opening of the first end insulator. The second end insulator is not fastened directly to the motor housing so as to be axially unconstrained relative to the motor housing to accommodate for axial tolerances associated with the stator.