Outer Rotor Brushless Motor Bushing for Bearing Oil Retention
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Solution Overview
Problem
Existing outer rotor brushless motors with impregnated bearings face challenges in maintaining oil levels, as they lack effective structures to recover and retain oil that leaks, leading to reduced motor efficiency and bearing lifespan.
Innovation Solution
The design incorporates a bushing with an oil-repellent finish and a washer that rotates with the shaft, creating clearances to repel and accumulate leaking oil, preventing its escape and enhancing oil retention within the motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a recessed portion with a washer is provided to recover leaked oil, then oil retention is improved, but oil loss outside the recessed portion cannot be suppressed
Solution Approach 1:
The bushing surface is selectively treated with an oil repellent finish only in specific regions (the first inner peripheral surface and first end surface), while other regions maintain oil affinity. This local differentiation enables the bushing to both repel oil from certain areas and allow oil recovery in others, resolving the contradiction between oil retention and structure complexity.
Solution Approach 2:
The oil repellent finish acts as an intermediary layer on the bushing surface that actively prevents oil adhesion in critical areas. This intermediary treatment enables the bushing to control oil flow and prevent loss without requiring additional complex mechanical structures.
2Loss of substance
If the bushing inner peripheral surface contacts the shaft, then structural simplicity is maintained, but oil leakage cannot be suppressed
Solution Approach 1:
The bushing incorporates an oil repellent finish on specific surfaces (first inner peripheral surface and first end surface) while maintaining a simple overall structure. This localized treatment allows the bushing to suppress oil leakage without requiring complex additional components.
Solution Approach 2:
The surface properties of the bushing are changed by applying an oil repellent finish, altering the interaction between the bushing surface and oil. This parameter change (surface chemistry) enables oil leakage suppression without changing the basic structural parameters of the bushing.
3Quantity of substance
If clearances are provided between the bushing and shaft, then oil accumulation is enabled, but structural precision requirements increase
Solution Approach 1:
The oil repellent finish is applied to specific surfaces of the bushing to create localized oil accumulation zones. This selective treatment allows oil to accumulate in controlled areas without requiring high-precision clearance control throughout the entire bushing-shaft interface.
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 configuration effectively suppresses oil reduction in the impregnated bearing, ensuring efficient operation and extended bearing life by preventing oil leakage and promoting oil retention within the motor.
Implementation Method 1
an oil repellent finish is applied to at least the first end surface and the first inner peripheral surface
Implementation Method 2
oil that has leaked along the shaft is splashed by the washer onto an inner peripheral surface of the recessed portion
Implementation Method 3
a viscous oil film is placed between two surfaces that slide relative to each other (that is, between an inner peripheral surface of the impregnated bearing and an outer peripheral surface of the shaft) to support the shaft by use of the pressure of the oil film
Data Source
AI summary
An outer rotor brushless motor includes: a shaft; a rotor; a stator; a tubular bushing at one side of the stator; an impregnated bearing at the other side of the bushing; and a washer rotatable integrally with the shaft. The bushing has: a fixed portion fixed to a core inner peripheral surface, the fixed portion having a first end surface facing a bearing end surface, and a first inner peripheral surface facing an outer peripheral surface with first clearance in between; and a housing having a second inner peripheral surface with a greater diameter than the first inner peripheral surface, on the one side of the fixed portion. An oil repellent finish is applied to a surface of the bushing. The washer is placed radially inward of the second inner peripheral surface. Second clearance greater than the first clearance is between the bearing end surface and the first end surface.