Method and energization circuit for an induction-heated laundry dryer

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Solution Overview

Problem

Existing laundry dryers with electrical resistance heating elements face high maintenance costs due to complex and wear-prone brush contacts, and heat pump dryers have longer drying times and limited temperature range, while indirect temperature measurement methods are unreliable and costly.

Innovation Solution

An induction heater energization method that involves interrupting the heating to allow the oscillator circuit to freely oscillate, measuring the resonant frequency, and determining the drum temperature based on this frequency, using a microcontroller and additional ferromagnetic material to enhance measurement accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If electrical resistance heating elements are used to heat the drum, then heating efficiency is improved, but maintenance costs increase due to complex brush contacts

Engineering Contradiction:

Improveheating efficiencyVSAvoidmaintenance costs

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent replaces the mechanical brush contact system with an induction heating system. Instead of using electrical resistance heating elements that require sliding contacts to supply power to the rotating drum, the invention uses electromagnetic induction to heat the drum without direct electrical connection. The induction heater generates an alternating magnetic field that induces eddy currents in the ferromagnetic drum, heating it through resistive losses in the drum material itself, thereby eliminating the need for brush contacts and their associated maintenance issues.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces ferromagnetic material as an intermediary between the induction heater and the laundry. The ferromagnetic drum acts as a mediator that converts electromagnetic energy from the induction heater into thermal energy through hysteresis and eddy current losses. This intermediary approach allows efficient heat transfer to the laundry without requiring direct electrical contact with the rotating drum, solving both the efficiency and reliability problems.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If heat pump dryers are used to reduce energy consumption, then energy efficiency is improved, but drying time increases

Engineering Contradiction:

Improveenergy efficiencyVSAvoiddrying time

Core Design Contradiction:

Use of energy by moving objectVSLoss of time

Solution Approach 1:

The patent employs periodic action by alternating between induction heating phases and heat pump drying phases. The induction heater provides rapid periodic heating pulses to the drum, which quickly raises the drum temperature and accelerates evaporation. This is combined with the heat pump's continuous dehumidification function. The periodic induction heating compensates for the heat pump's slower heating rate, reducing overall drying time while maintaining energy efficiency through the heat pump's heat recovery cycle.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent uses a composite approach by combining two different heating technologies - induction heating and heat pump heating - into a single drying system. The induction heater provides rapid high-temperature heating capability, while the heat pump provides energy-efficient dehumidification and moderate heating. This composite system leverages the strengths of both technologies to achieve both short drying times and low energy consumption, overcoming the limitations of using either technology alone.

Inventive Principle:

Principle #40Composite materials

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 reduces maintenance costs, improves drying efficiency by accurately controlling drum temperature, and shortens drying times while minimizing stress on laundry, with a reliable and cost-effective solution for temperature measurement.

Implementation Method 1

an induction heater (3) adapted to heat the drum (2)

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

allowing an oscillator circuit of the induction heater to freely oscillate; measuring a resonant frequency of the oscillator circuit

Methodology Applied

Scientific EffectElectromagnetic oscillation:

Implementation Method 3

using a microcontroller and additional ferromagnetic material to enhance measurement accuracy

Methodology Applied

Scientific EffectFerromagnetism: Ferromagnetism

Data Source

PatentUS10590595B2Method and energization circuit for an induction-heated laundry dryer

Publication Date: 2020.03.17 MIELE & CO KG

AI summary

A method for energizing an induction heater of a laundry dryer includes energizing the induction heater to heat a drum of the laundry dryer; interrupting the energization of the induction heater for a time interval, allowing an oscillator circuit of the induction heater to freely oscillate; measuring a resonant frequency of the oscillator circuit during the time interval; and determining a temperature of the drum based on the measured resonant frequency.