Laundry Dryer Dryness Detection with Speed-Adaptive End Cycle Control
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Solution Overview
Problem
Existing laundry dryer systems inaccurately detect the end of a drying cycle due to variations in rotation speed and air stream fan speed, leading to premature cycle termination, as the conductometric system is calibrated for fixed speeds and is affected by changes in contact between electrodes and laundry at low speeds or when the drum is stopped.
Innovation Solution
The method involves dynamically adjusting the rotation speed of the laundry drum and air stream fan during the drying cycle based on estimated laundry amount, dryness level, and selected drying cycle parameters, with specific end cycle conditions defined for varying speed conditions to prevent false detections, using a system that disables or modifies end cycle condition checking when speeds fall below or exceed predetermined thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the rotation speed of the laundry drum and/or air stream fan is varied during the drying cycle, then energy consumption is reduced and drying performance is improved, but the conductometric system produces inaccurate signals leading to false end cycle detection
Solution Approach 1:
The patent applies dynamics by making the end cycle condition dynamic rather than fixed. The control unit adjusts the end cycle condition based on the actual rotation speed of the laundry drum and/or air stream fan. When rotation speed varies from the calibrated speed, the system automatically compensates by adjusting the end cycle condition threshold, thereby maintaining accurate dryness detection despite speed variations that would otherwise cause measurement errors.
Solution Approach 2:
The patent changes the parameter of the end cycle condition based on rotation speed. Instead of using a fixed end cycle condition threshold calibrated for a specific rotation speed, the system modifies this threshold dynamically according to the actual rotation speed. This parameter adaptation allows accurate dryness level detection across varying operating conditions, resolving the contradiction between energy-saving speed variations and measurement accuracy.
2Measurement precision
If the conductometric system is calibrated for a fixed rotation speed, then accurate dryness detection is achieved at that speed, but the system cannot adapt to varying rotation speeds or stopped drum conditions
Solution Approach 1:
The system transforms the static end cycle condition into a dynamic one that automatically adapts to varying rotation speeds. The control unit continuously monitors the actual rotation speed and adjusts the end cycle condition accordingly, enabling the system to maintain accurate dryness detection whether the drum is running at calibrated speed, varying speed, or stopped.
Solution Approach 2:
The patent makes the end cycle condition checking system universal by enabling it to function accurately across all rotation speed conditions. Instead of being limited to a single calibrated speed, the system now handles multiple operating modes (calibrated speed, varying speeds, stopped drum) through automatic adaptation of the end cycle condition, achieving multi-functionality without requiring multiple calibration sets.
3Reliability
If the end cycle condition checking is continuously performed, then accurate dryness monitoring is maintained, but false detections occur when rotation speed is below threshold or drum is stopped
Solution Approach 1:
The system changes the end cycle condition parameter dynamically based on rotation speed. When rotation speed drops below a predetermined threshold or the drum stops, the system adjusts the end cycle condition to prevent false detections. This parameter adaptation maintains reliable dryness monitoring while eliminating false positives that would occur with a fixed threshold under varying speed conditions.
Solution Approach 2:
The system takes preliminary anti-action by preemptively adjusting the end cycle condition when rotation speed variations are detected. Instead of waiting for false detections to occur, the control unit proactively modifies the end cycle condition threshold based on the current rotation speed, preventing false detections before they can happen during low-speed or stopped drum operations.
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 approach ensures accurate detection of dryness levels, preventing premature cycle termination and optimizing energy consumption by allowing speed adjustments based on laundry conditions, thereby enhancing drying performance and user control over drying cycles.
Implementation Method 1
The dryness level signal is estimated from the electric conductivity or the electric resistance of the laundry detected by a conductometric system
Data Source
AI summary
The present invention relates to a method for controlling a drying cycle of a laundry dryer having a laundry drum and an air stream fan for circulating drying air through said laundry drum. The method comprises the steps of: starting a drying cycle (14); performing the drying cycle (16); detecting an electric resistance and/or conductivity of the laundry during the drying cycle (16) for estimating a dryness level of the laundry; comparing the electric resistance and/or conductivity of the laundry with an end cycle condition (20; 28, 30; 36); finishing the drying cycle (16), if the end cycle condition (20; 28, 30; 36) is fulfilled. The end cycle condition (20; 28, 30; 36) depends on the rotation speed (SD) of the laundry drum and/or on the rotation speed (SF) of the air stream fan. Further, the present invention relates to a corresponding laundry dryer.