Washing Machine Drum Speed Control for Closed Liquid Ring Prevention
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Solution Overview
Problem
The formation of a closed liquid ring at the circumferential walls of the laundry drum during high-speed rotation in washing machines interferes with accurate foam monitoring and drainage, leading to incomplete washing cycles, particularly during spinning and dewatering phases.
Innovation Solution
Defining an upper threshold value for the liquid level to prevent closed liquid ring formation by reducing the rotational speed of the laundry drum if exceeded, and implementing a foam-reducing procedure that includes temporarily switching off the drain pump and adjusting the drum speed to ensure accurate foam detection and reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the laundry drum rotates at high speed during spinning phase, then dewatering efficiency is improved, but a closed liquid ring forms at circumferential walls preventing accurate foam monitoring
Solution Approach 1:
The patent applies dynamics by making the drum rotation speed variable rather than constant. The control unit dynamically adjusts the rotation speed based on detected liquid level: maintaining high speed for efficient dewatering when liquid level is below the upper threshold, and reducing speed when the liquid level approaches the threshold to prevent closed liquid ring formation that would interfere with foam monitoring. This dynamic speed adjustment resolves the contradiction between maintaining high dewatering efficiency and ensuring accurate foam monitoring.
2Productivity
If the liquid level exceeds the upper threshold during high-speed rotation, then a closed liquid ring forms at circumferential walls, but this prevents accurate measurement of liquid level and foam amount
Solution Approach 1:
The patent implements feedback control by continuously monitoring the liquid level with a sensor and comparing it against a predetermined upper threshold. When the liquid level approaches the threshold, the control unit receives feedback and automatically reduces the drum rotation speed to prevent closed liquid ring formation. This feedback mechanism ensures that the system maintains optimal conditions for both efficient spinning and accurate liquid level measurement, resolving the contradiction between spinning efficiency and measurement accuracy.
3Reliability
If foam amount is high during spinning phase, then foam compromises drain pump functioning and obstructs liquid drainage, but foam monitoring becomes unreliable when closed liquid ring is present
Solution Approach 1:
The patent applies preliminary action by proactively preventing the formation of closed liquid rings before they can interfere with foam monitoring. By monitoring the liquid level and reducing drum speed when the level approaches the upper threshold, the system prevents the conditions that would make foam detection unreliable. This preliminary preventive measure ensures that foam monitoring remains accurate throughout the spinning phase, allowing timely detection and management of foam that could compromise drain pump functioning.
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 method effectively prevents closed liquid ring formation, allowing for accurate foam detection and reduction, ensuring uninterrupted and efficient washing cycles by maintaining proper liquid drainage and foam management.
Implementation Method 1
when the drum is rotating at a certain rotation speed there is a threshold level of the liquid level in the washing tub at which the liquid starts rotating along the circumferential walls of the drum, in such a way to create a closed liquid ring
Data Source
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AI summary
The present invention relates to a method for operating a washing machine (10) comprising a washing tub (24) containing a laundry drum (26), said method comprises the steps of: - detecting a liquid level (44) in said washing tub (24) and/or in a draining region thereof while said laundry drum (26) is rotating at a first speed, - comparing the detected liquid level (44) with an upper threshold value (48), wherein the excess of said upper threshold value (48) by the liquid level (44) while the laundry drum (26) rotates at a rotation speed equal or higher than said first speed generates a closed liquid ring at circumferential walls of the laundry drum (26), and - if the detected liquid level (44) exceeds the upper threshold value (48), then reducing the rotational speed of the laundry drum (26) below said first speed and performing a foam-detecting procedure for detecting the amount and/or presence of foam inside the washing tub (24) and/or in the draining region thereof.