Washing Machine Freeze Detection Using Drum-Induced Water Level Variation
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Solution Overview
Problem
Existing washing machines face issues with accurately determining whether water in the tub is frozen, especially when the machine is installed at an angle, leading to potential overheating of the heater and risk of fire due to misjudgment by temperature sensors.
Innovation Solution
A washing machine with a tub, drum, driving unit, water level sensor, and control unit that calculates water level variation during drum rotation to determine the freeze state, eliminating the need for temperature sensors and ensuring accurate freeze detection regardless of installation position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a temperature sensor is used to detect freeze state, then the detection method is simple, but the detection accuracy deteriorates when the machine is installed at an angle causing the sensor to be completely submerged in water
Solution Approach 1:
The patent replaces the temperature-based detection system with a water level-based detection system. Instead of using a temperature sensor to detect freeze state, the invention uses a water level sensor to measure water level changes during drum rotation. When water is frozen, it cannot move with the drum rotation, resulting in abnormal water level variations that indicate freeze state. This substitution eliminates the problem of temperature sensor submersion and provides accurate freeze detection regardless of installation angle.
Solution Approach 2:
The patent changes the detection parameter from temperature to water level. By monitoring water level variations during drum rotation instead of temperature, the system can accurately detect freeze state. The control unit calculates water level variations and compares them against predetermined thresholds to determine whether water is frozen, providing reliable detection independent of installation orientation.
2Ease of manufacture
If the temperature sensor is completely submerged in water due to inclined installation, then the sensor positioning is simple, but the freeze detection reliability deteriorates
Solution Approach 1:
The patent replaces the temperature sensor with a water level sensor that detects freeze state through water level changes during drum rotation. This substitution maintains the simplicity of sensor installation (the water level sensor can also be positioned without complex mounting requirements) while dramatically improving reliability, as the water level sensor can accurately detect freeze state even when completely submerged in water during inclined installation.
Solution Approach 2:
The system uses the drum rotation itself to generate the detection mechanism. During normal washing operation, the drum rotates and causes water to move; when water is frozen, it cannot move with the rotation, creating detectable water level variations. This self-service approach uses the existing operational motion to enable reliable freeze detection without requiring separate testing procedures or complex sensor positioning.
3Device complexity
If freeze detection is based on temperature sensor readings, then the control logic is simple, but the safety deteriorates due to potential overheating from misjudgment
Solution Approach 1:
The patent replaces temperature-based control logic with water level-based control logic. The control unit monitors water level variations during drum rotation and determines freeze state based on whether the variation exceeds a predetermined threshold. This substitution eliminates the risk of heater overheating from misjudgment, as water level changes provide direct evidence of freeze state regardless of installation angle or sensor positioning, while maintaining relatively simple control logic.
Solution Approach 2:
The system implements feedback by continuously monitoring water level changes during drum rotation and using this information to control heater operation. The control unit calculates water level variations and uses this feedback to determine whether to activate the heater for freeze protection, ensuring safe operation by base(ing) decisions on direct observational evidence of freeze state rather than temperature readings that may be affected by installation orientation.
Data Source
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AI summary
Provided are a washing machine and a method for controlling the same. The method for controlling a washing machine includes supplying water to a tub, driving a driving unit to perform tumbling to rotate a drum disposed in the tub, calculating a water level variation in the tub, and displaying freeze state information on a display unit when the calculated water level variation is less than a reference water level variation.