Motor Shaft Bushing Alignment for Low-Vibration Washing Machines
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Solution Overview
Problem
In drum-type washing machines, increased eccentricity between the motor shaft and bushing leads to abnormal rotation, vibration, and noise, as well as faulty motor control due to improper Hall sensor detection, caused by uneven clearance and lack of firm support.
Innovation Solution
A motor design with minimal clearance between the motor shaft and bushing, utilizing a fastening member and guides to maintain high concentricity and secure the connection, including a serrated portion on the motor shaft and bushing for precise alignment and a doughnut-shaped cap as an outer fastening guide to prevent slippage and deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the motor shaft is supported by a resin bushing, then the structure is simple and easy to manufacture, but the concentricity deteriorates over time due to bushing wear
Solution Approach 1:
The patent uses a composite structure combining a resin bushing with a metal reinforcing member (sleeve). The resin bushing provides ease of manufacture and corrosion resistance, while the metal sleeve embedded within it provides high strength and maintains concentricity over time by preventing wear-induced deformation of the motor shaft support structure.
2Reliability
If the motor shaft contact length with the bushing is increased, then the reliability improves, but the device complexity increases
Solution Approach 1:
Instead of simply increasing the contact length by making the bushing longer, the patent embeds a metal reinforcing member (sleeve) within the resin bushing. This composite structure enhances reliability by providing superior wear resistance and maintaining concentricity, while avoiding the need to significantly increase the overall length of the bushing-motor shaft assembly.
Solution Approach 2:
The metal sleeve is strategically positioned at the critical contact region between the motor shaft and bushing. This local reinforcement provides enhanced wear resistance and concentricity maintenance precisely where needed, without unnecessarily increasing the overall device complexity or length throughout the entire bushing structure.
3Duration of action of moving object
If clearance between motor shaft and bushing increases, then wear is reduced, but eccentricity increases causing vibration and noise
Solution Approach 1:
The metal sleeve embedded in the resin bushing creates a composite bearing structure that optimizes the clearance characteristics. The metal sleeve provides a precise, wear-resistant surface that maintains consistent clearance over time, preventing both excessive wear and the development of harmful eccentricity that would cause vibration and noise during extended service life.
Solution Approach 2:
The patent carefully controls the clearance parameter between the motor shaft and the composite bushing-sleeve structure. By using the metal sleeve with precise dimensional tolerances, the clearance is maintained within an optimal range that balances wear reduction with prevention of eccentricity-induced vibration and noise.
4Device complexity
If the rotor is directly connected to the motor shaft, then the structure is simplified, but Hall sensor detection accuracy deteriorates due to position instability
Solution Approach 1:
The metal sleeve embedded in the resin bushing provides a stable, precise reference surface that maintains the rotor's positional relationship with the motor shaft. This stability ensures accurate Hall sensor detection while keeping the overall structure relatively simple through the composite bushing design, rather than requiring complex positioning mechanisms.
Data Source
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AI summary
Disclosed is a washing machine which includes a tub which holds laundry, a drum which is disposed in and rotates within the tub, a stator which is fixed to the tub, and a rotor which is fixed to the drum. The rotor includes a frame, a bushing installed on the frame, a motor shaft having an end which is inserted in and fixed to the bushing, a bearing interposed between the motor shaft and the tub, and at least one guide disposed between the motor shaft and the bushing at an end of the bushing.