Capacitive Sensing for Reliable Drying Cycle Humidity Detection

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Solution Overview

Problem

Existing solutions for providing reliable drying information in appliances, such as tumble dryers, are unreliable due to unpredictable drying processes, inaccurate load humidity detection, and noise/signal biases in sensing devices.

Innovation Solution

An appliance equipped with a capacitive sensing arrangement that generates an electric signal indicative of the humidity of the load, allowing for accurate estimations of load mass, residual humidity, residual time to the end of the drying cycle, and end cycle detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional humidity sensors are used, then the appliance can perform drying cycles, but the drying information is unreliable due to unpredictable drying processes and inaccurate load humidity detection

Engineering Contradiction:

Improvereliability of drying informationVSAvoidaccuracy of load humidity detection

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent replaces conventional mechanical/contact-based humidity sensing with electromagnetic radiation detection. The sensor detects humidity by measuring the attenuation of electromagnetic waves (microwave or millimeter wave) as they pass through the laundry load, eliminating the need for physical contact with the load and avoiding the reliability issues of conventional sensors.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the measurement parameter from electrical conductivity or capacitance (conventional methods) to electromagnetic wave attenuation. By measuring how much the electromagnetic wave is attenuated as it passes through the load, the system obtains accurate humidity information without direct contact, resolving the contradiction between reliability and measurement precision.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If contact-based humidity sensors are used, then humidity can be detected, but noise and signal biases affect the accuracy of drying information

Engineering Contradiction:

Improvehumidity detection accuracyVSAvoidnoise and signal biases in sensing devices

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent substitutes contact-based electrical sensing with non-contact electromagnetic wave transmission. The sensor transmits electromagnetic waves through the load and measures attenuation without physical contact, thereby eliminating noise and signal biases that plague conventional contact-based sensors.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If drying cycle assumptions and predetermined conditions are used, then drying information can be provided, but the information is unreliable due to unpredictable factors such as clothes wrapping in the drum

Engineering Contradiction:

Improvesimplicity of drying cycle controlVSAvoidreliability of drying information

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent implements real-time feedback by continuously measuring electromagnetic wave attenuation through the load during the drying cycle. This actual measurement feedback replaces unreliable assumptions and predetermined conditions, allowing the system to adapt to unpredictable factors like clothes wrapping and provide accurate drying information throughout the cycle.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces assumption-based control logic with direct electromagnetic measurement. By measuring the actual attenuation of electromagnetic waves passing through the load, the system obtains reliable humidity data regardless of unpredictable drying conditions, resolving the contradiction between operational simplicity and information reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The capacitive sensing arrangement provides reliable and accurate drying information, overcoming the limitations of existing technologies by accurately detecting load humidity and estimating drying cycle parameters.

Implementation Method 1

a capacitive sensing arrangement arranged for generating an electric signal indicative of a degree of humidity of a load contained in the drying chamber

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

the at least one emitting element is adapted to emit ultrasonic waves having at least one frequency or a frequency range that is responsive to water absorbed by laundry

Methodology Applied

Scientific EffectUltrasonic vibration: Ultrasonic Vibration

Data Source

PatentEP3562990B1Appliance with reliable information of a drying cycle

Publication Date: 2025.05.21 ELECTROLUX APPLIANCES

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Figure 3A~3B

AI summary

An appliance (100) is proposed. The appliance (100) comprises: - a drying chamber (120) for performing a drying cycle, - within the drying chamber (120), a capacitive sensing arrangement (410) arranged for generating an electric signal indicative of a degree of humidity of a load contained in the drying chamber (120), and - a control unit (150) arranged for carrying out at least one among: estimating (905) a mass of the load; estimating (915-920) a residual humidity of the load; estimating (910-935) a residual time to the end of the drying cycle, and detecting (940) an end of the drying cycle according to the electric signal.