Compact Brushless Motor Assembly With Floating Stator End Insulator
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing brushless DC motor designs for power tools are too large for placement in a gripping handle and are not capable of producing high power output from a smaller-voltage DC power source, while also being prone to noise and vibration due to segmented stator designs.
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 core, end insulators, and windings, and a rotor with permanent magnets, where the motor housing is fastened to one end insulator and the other end insulator is floating to absorb axial tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a brushless DC motor is designed to output high power, then the power output is improved, but the motor diameter becomes greater than or equal to 40 mm making it unsuitable for gripping handle placement
Solution Approach 1:
The motor is divided into functionally independent modules: a fixed motor housing providing structural support and mounting, and a floating stator assembly that can move axially to accommodate tolerance variations. This segmentation allows each module to be optimized independently while maintaining overall compact dimensions suitable for gripping handle placement.
Solution Approach 2:
The floating stator design allows axial position parameter to vary within a tolerance range, absorbing cumulative manufacturing tolerances without requiring tight tolerance control on all components. This parameter flexibility enables compact motor design while maintaining high power output capability.
2Ease of manufacture
If a segmented stator design is used to form stator windings, then the manufacturing is improved, but the motor becomes prone to high noise and vibration in high torque applications
Solution Approach 1:
The stator core segments are merged with end insulators to form an integrated stator assembly. This merging provides structural rigidity that reduces vibration and noise while maintaining the manufacturing advantages of segmented construction. The unified assembly acts as a single rigid body during operation, eliminating the harmful effects of segmented designs.
3Manufacturing precision
If tight manufacturing tolerances are applied to all motor components, then the assembly precision is improved, but the difficulty of manufacture and assembly increases particularly in compact designs
Solution Approach 1:
The floating stator design incorporates tolerance absorption capability before assembly, creating a cushioning effect that accommodates cumulative tolerance variations. This beforehand cushioning allows standard manufacturing tolerances to be used without compromising final assembly precision, significantly easing the manufacturing and assembly process.
4Volume of moving object
If the motor is designed to be compact for gripping handle placement, then the volume is reduced, but the capability to produce high power output from smaller-voltage DC power source is compromised
Solution Approach 1:
The motor design optimizes the axial dimension while maintaining compact radial dimensions suitable for gripping handles. The floating stator configuration allows axial adjustment to maximize the air gap and magnetic flux path efficiency, compensating for the reduced overall volume and maintaining high power output capability from smaller-voltage DC power sources.
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 solution enables the production of high power output in a compact form, suitable for power tool applications, while minimizing noise and vibration and accommodating manufacturing tolerances.
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
Implementation Method 3
the second end insulator is not fastened directly to the motor housing so as to be floating along the axial direction and spaced apart by an axial gap from another component located within the motor housing to absorb axial tolerances associated with the stator
Data Source
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.