Microwave Heating Circuit Using Reflected Power Between Dual Chambers

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Solution Overview

Problem

Conventional microwave heating apparatuses using semiconductor elements for microwave generation face inefficiencies as a significant portion of the generated microwave power is consumed non-heating energy, leading to energy wastage and potential thermal destruction of the semiconductor elements due to reflected power.

Innovation Solution

The apparatus employs a configuration with two heating chambers, where microwaves are transmitted between them via a circulator, ensuring that all supplied microwave power is absorbed by lossy materials, either the article being heated or a microwave absorber, thereby achieving 100% energy utilization. This includes using a microwave absorber in one chamber to absorb reflected power and transfer heat to the other chamber, along with a control system to adjust frequency based on power detection signals for optimal heating modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a circulator is used to prevent reflected microwave power from returning to the semiconductor element, then the semiconductor element is protected from thermal destruction, but a significant portion of the generated microwave power is consumed as non-heating energy

Engineering Contradiction:

Improvethermal durability of semiconductor elementVSAvoidmicrowave power consumption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The invention converts the harmful reflected microwave power into useful heating energy by directing it to a microwave absorber that converts it to heat, which is then transferred to the heating chamber. This resolves the contradiction by making the previously wasted energy (reflected power) beneficial for the heating process.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The invention introduces a microwave absorber as an intermediary component between the circulator and the heating chamber. This absorber receives the reflected microwave power, converts it to heat, and transfers it to the heating chamber, thereby eliminating energy waste while protecting the semiconductor element.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Temperature

If reflected power is consumed by a dummy resistance plate, then heat is retained in the heating chamber, but energy efficiency is reduced due to power consumption without direct heating contribution

Engineering Contradiction:

Improveheat retention in heating chamberVSAvoidreflected power consumption

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

The invention transforms the previously wasted reflected power (harmful to the semiconductor element) into beneficial heating energy by using a microwave absorber to convert it to heat, which is then transferred to the heating chamber. This eliminates energy loss while achieving the desired heat retention effect.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Productivity

If microwave power is increased to improve heating efficiency, then heating speed increases, but the risk of thermal destruction to semiconductor elements increases due to reflected power

Engineering Contradiction:

Improveheating efficiencyVSAvoidthermal durability of semiconductor element

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention converts reflected microwave power (which becomes more significant at higher power levels) into useful heating energy through the microwave absorber. This allows the semiconductor element to operate at higher power levels for improved heating efficiency while the converted reflected power provides additional heating, eliminating the reliability risk.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 configuration ensures that nearly all microwave power is consumed as heating energy, enhancing energy-saving performance and preventing thermal damage to semiconductor elements by effectively managing reflected power.

Implementation Method 1

a circulator forming a circulation type non-reciprocal circuit is used so that high-frequency power amplified in the microwave generation part is supplied to a heating chamber and the high-frequency power is not returned to the microwave generation part

Methodology Applied

Scientific EffectCirculator (non-reciprocal circuit):

Implementation Method 2

reflected power returned from a heating chamber is consumed by a dummy resistance plate provided on an outer wall surface in an upper part of the heating chamber, and is utilized for retaining heat in the heating chamber

Methodology Applied

Scientific EffectMicrowave absorption: Absorption (EM radiation)

Implementation Method 3

the microwave supplied to the first heating chamber or the second heating chamber is absorbed by a microwave lossy material (such as an accommodated article to be heated) placed in the heating chamber

Methodology Applied

Scientific EffectDielectric heating: Dielectric Heating

Implementation Method 4

Embedded within the base member are a plurality of rods of a heat conductive material arranged in a preselected pattern which will convey the heat generated within the microwave energy absorptive base material in the presence of microwave energy to an oven load

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP2306785B1Microwave heating device

Publication Date: 2019.04.03 PANASONIC HOLDINGS CORP

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AI summary

A microwave heating apparatus includes a microwave generation part 10 using a semiconductor element, and first and second heating chambers 100a, 100b to each of which a microwave generated in the microwave generation part is fed. A reflected microwave returned from at least one of the first and second heating chambers 100a, 100b to the microwave generation part is transmitted to the other heating chamber by a circulation type non-reciprocal circuit 118, so that generated power of the microwave generation part is substantially completely consumed upon heating of an article to be heated.