BLDC Motor Compliant Mount for Misalignment
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Solution Overview
Problem
Inside-out BLDC motors used in air-conditioning units face challenges in aligning the fan, rotor, and stator on a common rotational axis due to their compact size and length, requiring effective vibration isolation and misalignment accommodation to maintain performance and quiet operation.
Innovation Solution
A motor design featuring an annular stator core with stator poles and phase windings, a rotor with facing poles and an axial rotor axle, and a single bearing element positioned radially within the annular core, along with a compliant mount such as an elastomeric sleeve or ball joint to allow for misalignment between the stator and rotor axes, and a bearing locating member that integrates with the insulator to secure the bearing element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact motor design is used, then the motor size is reduced, but alignment between fan, rotor, and stator becomes difficult
Solution Approach 1:
The motor is divided into functionally independent segments: the stator assembly with its own bearing, the rotor assembly with its own bearing, and a flexible coupling mechanism. This segmentation allows each component to be manufactured and assembled separately with standard tolerances, avoiding the need for complex multi-component alignment while maintaining compact overall dimensions.
Solution Approach 2:
The flexible coupling mechanism employs composite material construction, combining rigid elements for structural support with flexible elements (such as elastomeric materials or spring-loaded components) that provide tolerance compensation. This composite approach enables the compact motor design to accommodate misalignment between fan, rotor, and stator without requiring high-precision manufacturing.
2Object-affected harmful factors
If vibration isolation is implemented, then quiet operation is achieved, but device complexity increases
Solution Approach 1:
Vibration isolation functionality is merged into the existing bearing arrangements and mounting structures. The stator bearing and rotor bearing are integrated with the housing and fan support structures, providing vibration damping without requiring separate isolation components. This combining approach achieves quiet operation while avoiding additional complexity.
Solution Approach 2:
Flexible coupling elements and compliant mounting structures serve as intermediary components between the motor and the fan housing. These intermediaries absorb and isolate vibrations generated by the motor, preventing their transmission to the fan and housing, thereby achieving quiet operation without significantly increasing overall device complexity.
3Adaptability or versatility
If misalignment accommodation is allowed, then alignment tolerance is improved, but structural rigidity decreases
Solution Approach 1:
The mounting structure incorporates dynamic elements that allow controlled movement and adjustment to accommodate misalignment between the motor shaft and fan hub. These dynamic features include flexible couplings and compliant mounts that can adapt to dimensional variations while maintaining sufficient structural rigidity for operational strength through their material selection and geometric design.
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
This design enables efficient vibration isolation and misalignment accommodation, ensuring quiet operation and compact size while reducing the number of components, thereby improving manufacturability and maintaining a consistent air gap between stator and rotor poles.
Implementation Method 1
a compliant mount positioned between the bearing element and the bearing locating member or between the rotor axle and the bearing element to allow for misalignment between the stator and rotor axes
Implementation Method 2
only one bearing element, being positioned between the rotor axle and the stator, radially within the annular core, to rotationally couple the rotor to the stator
Implementation Method 3
a stator comprising an annular core, stator poles extending from the annular core, and phase windings wound on the stator poles
Implementation Method 4
an external rotor with permanent magnet poles arranged circumferentially and facing outer ends of the stator poles
Data Source
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AI summary
A BLDC motor for driving a cross flow fan in an air-conditioning application comprises an external rotor and an internal stator. The stator is a salient pole stator with insulated pole teeth and conductor coils. The inner diameter of the stator supports a single bearing. An electronic PCBA for control of the BLDC motor is optionally attached to the stator, all of which is encapsulated in a thermoset resin. The rotor comprises permanent magnet component(s) and a rotor frame. The rotor frame includes a stub axle that engages with the bearing element and features to provide torsional or rotational compliance between the rotor magnets and the fan. A level of compliance is provided between the bearing element and the stator to allow for angular misalignment between the rotational axis of the fan and the stator.