Washing Machine Foam Control Using Drum Speed Feedback
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Solution Overview
Problem
Existing washing machine technologies face challenges in controlling foam generation during the washing process, leading to inefficient energy use and potential overheating, as well as issues with foam escaping or not forming sufficiently, due to unpredictable parameters like laundry type and detergent dosage.
Innovation Solution
A method involving sensors to detect hydrostatic pressure and adjust the drum speed to maintain a specified foam concentration range, using a detergent solution drainage system with a rotating drum and heating device, ensuring adequate foam development while preventing excessive foam formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the amount of free liquor is reduced to decrease energy consumption, then energy efficiency is improved, but the heat transport capability from heater to laundry deteriorates
Solution Approach 1:
The patent changes the physical state parameter of the washing medium from liquid to foam. Foam has different thermal properties than liquid, allowing heat transport with reduced free liquor volume. The foam structure maintains thermal contact between heater and laundry while requiring less free liquid, thus resolving the contradiction between energy efficiency and heat transport capability.
Solution Approach 2:
The patent utilizes phase transition by generating foam from liquid detergent solution through mechanical agitation. The foam phase (gas-liquid mixture) provides effective heat transport medium with reduced liquid content. This phase transition enables the system to maintain reliable heat transport while significantly reducing the amount of free liquor required, thereby improving energy efficiency.
2Productivity
If foam is generated to improve cleaning efficiency and reduce water usage, then cleaning performance is improved, but the risk of foam escaping from the washing machine increases
Solution Approach 1:
The patent employs feedback control by monitoring foam level in the washing drum and adjusting drum rotation speed accordingly. When foam level approaches the escape threshold, the system reduces drum speed to prevent foam overflow. This closed-loop control maintains high cleaning efficiency through adequate foam generation while preventing the harmful effect of foam escape.
Solution Approach 2:
The patent applies dynamic adjustment of drum rotation speed based on real-time foam conditions. The drum speed is not fixed but varies dynamically to optimize foam generation while preventing overflow. This dynamic control allows the system to maintain productive foam levels for cleaning while adapting to prevent harmful foam escape, resolving the contradiction between cleaning efficiency and foam containment.
3Quantity of substance
If drum speed is increased to enhance foam generation, then foam concentration is improved, but the risk of foam overflow increases
Solution Approach 1:
The system uses feedback control where foam level sensors monitor the quantity of foam in the drum and provide signals to the control unit. Based on this feedback, the control unit adjusts drum speed to maintain optimal foam concentration while preventing overflow. This closed-loop control resolves the contradiction by dynamically balancing foam generation against foam containment.
Solution Approach 2:
The patent applies preliminary anti-action by reducing drum speed before foam overflow occurs. The control system anticipates potential overflow by monitoring foam level and proactively adjusts drum speed downward when foam approaches the critical level, preventing the harmful effect before it occurs. This allows the system to achieve high foam concentration during normal operation while preventing foam escape.
4Use of energy by moving object
If foam concentration is maintained at optimal levels for heat transport, then energy efficiency is improved, but the control complexity increases due to multiple influencing parameters
Solution Approach 1:
The patent uses feedback control with foam level sensors and control units to automatically monitor and adjust foam concentration. This automated feedback system manages the complexity of multiple influencing parameters (temperature, water amount, drum speed, detergent type) by providing real-time adjustments without requiring complex manual intervention. The system maintains optimal foam concentration for energy efficiency while the control complexity is managed through automated sensing and actuation.
Solution Approach 2:
The control system operates autonomously by self-monitoring foam levels and self-adjusting drum speed and other parameters to maintain optimal foam concentration. This self-service capability allows the system to manage the complexity of multiple parameters automatically, maintaining energy efficiency through optimal foam control without requiring complex user intervention or manual adjustments.
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 allows for stable operation of the washing machine by promoting desirable foam development while preventing foaming over, ensuring adequate heating device cooling and preventing overheating.
Implementation Method 1
the foam takes over the heating and cleaning of laundry to be cleaned
Implementation Method 2
Sufficient foam development is necessary to ensure sufficient energy transport from a heating device in a washing machine into the laundry
Implementation Method 3
foam, which can be generated by introducing mechanical energy into a wash liquor
Data Source
Figure 1
AI summary
The invention relates to a method for controlling the generation of suds during the treatment of washing with suds consisting of an aqueous surfactant solution in a programme-controlled washing machine. Said machine comprises a solution drain system that is situated on the base of an outer tub (1), a solution pump, a rotating drum (2) and a heating unit (13). The method comprises the following steps: a) detecting the suds contained in the outer tub (1) and/or in the drum (2); and b) setting and/or maintaining a predefined range for the concentration of the suds between c1 and c2, the detection (a) of the suds being carried out by means of one or several sensors (15), which track a hydrostatic pressure p, a temporal gradient (Δp/Δt) of the hydrostatic pressure p and/or a conductance k in the outer tub (1) and/or in the drum (2). A measured hydrostatic pressure p is compared to a predetermined lower value p1 for the hydrostatic pressure and a predetermined upper value p2 for the hydrostatic pressure and if pp2, the speed U of the drum (2) is decreased. The invention also relates to a washing machine that is suitable for carrying out said method.