Dryer Drum Temperature Detection Using Resonant Circuit Frequency
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Solution Overview
Problem
Existing methods for contactless temperature detection of a rotating drum in tumble dryers or washer-dryers are either imprecise or complex, with external sensors being prone to failure and calibration issues, and alternative methods require additional equipment and effort.
Innovation Solution
A two-part oscillating circuit is used, where the active circuit is fixed on the housing and the passive circuit is on the drum, with a temperature-dependent frequency-influencing component that provides feedback to the active circuit, allowing for precise temperature measurement without external sensors or complex signal generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external infrared sensor is used to measure drum temperature, then temperature detection is achieved, but manufacturing complexity and costs increase, and reliability decreases due to sensor failure and soiling
Solution Approach 1:
The patent extracts the temperature-dependent measurement function from the mechanical drum structure and transfers it to the electromagnetic field domain. By measuring the resonant frequency of the drum shell itself (which varies with temperature), the system eliminates the need for external infrared sensors and their associated complexity, while maintaining measurement capability through the drum's own physical properties
Solution Approach 2:
The patent introduces the resonant frequency of the drum shell as an intermediary parameter between temperature and measurement. Instead of directly measuring temperature with a sensor, the system measures the drum shell's resonant frequency, which serves as a temperature-dependent intermediary that reflects temperature changes without requiring direct thermal contact or external sensing components
2Measurement precision
If a one-piece resonant circuit with stationary oscillation is used, then temperature measurement is achieved, but measurement precision deteriorates due to mechanical tolerances and aging effects
Solution Approach 1:
The patent transitions from a static, stationary oscillation system to a dynamic rotating oscillation system. By measuring the resonant frequency during drum rotation, the system continuously updates the temperature measurement, compensating for mechanical tolerances and aging effects through ongoing dynamic measurement rather than relying on initial calibration of a fixed circuit
Solution Approach 2:
The patent implements feedback by continuously monitoring the resonant frequency of the rotating drum shell and using this information to track temperature changes over time. The system compares current resonant frequency measurements with reference values to determine temperature, providing continuous feedback that maintains measurement accuracy despite mechanical variations and aging
3Measurement precision
If calibration and adjustment are performed to achieve acceptable measurement accuracy, then temperature measurement precision improves, but manufacturing effort and costs increase
Solution Approach 1:
The patent enables the drum shell to serve itself as both the object being measured and the measurement sensor. The drum shell's own resonant frequency properties are exploited to measure its temperature, eliminating the need for external calibration equipment or adjustment mechanisms. The system self-calibrates by using the drum's inherent physical properties rather than requiring external reference standards
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 solution enables precise and simple contactless temperature detection of the drum, reducing manufacturing complexity and costs, and allowing for effective control of inductive heating, while being less susceptible to aging and environmental factors.
Implementation Method 1
the active oscillating circuit part and the passive oscillating circuit part are designed to jointly form an oscillating circuit whose resonant frequency depends on the temperature-dependent, frequency-influencing component of the temperature of the drum
Implementation Method 2
the passive oscillating circuit part has a temperature-dependent, frequency-influencing component
Implementation Method 3
By means of inductive coupling, electromagnetic waves are emitted inwards from the fixed housing of the tumble dryer or washer-dryer towards the rotating drum, which leads there, comparable to an inductive hob, to inductive heating of the metallic material of the drum
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a clothes dryer (1) or a washer-dryer (1) with a drum (2) designed to hold laundry to be dried, and with a housing (1) in which the drum (2) is rotatably mounted. The clothes dryer (1) or washer-dryer (1) is characterized in that the housing (1) has an active resonant circuit section (11), and that the drum (2) has a passive resonant circuit section (21), wherein the passive resonant circuit section (21) has a temperature-dependent, frequency-influencing component (R2), and wherein the active resonant circuit section (11) and the passive resonant circuit section (21) are configured to jointly form a resonant circuit (11, 21) whose resonant frequency depends on the temperature of the drum (2) via the temperature-dependent, frequency-influencing component (R2).