Microwave Oven Field Sensor Regulation for Uniform Heating

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Solution Overview

Problem

Existing microwave heating devices face challenges in achieving uniform heating due to hot and cold spots, which traditional solutions like turntables and mode stirrers do not fully address, and require complex designs with moving parts or non-standard cavity structures.

Innovation Solution

A microwave heating device with at least two microwave sources and field sensors to measure microwave field strengths, allowing for regulation of the sources to control heating patterns, eliminating the need for moving parts and achieving uniform heating through sequential or simultaneous feeding of microwaves.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If turntable or mode stirrer is used to eliminate hot and cold spots, then heating uniformity is improved, but device complexity increases due to moving parts

Engineering Contradiction:
Improveheating uniformityVSAvoidstructure complexity
Core Design Contradiction:
TemperatureVSDevice complexity

Solution Approach 1:

The patent replaces mechanical moving parts (turntable, mode stirrer) with electromagnetic field control. Multiple microwave sources with independently controllable amplitude and phase create synthetic mode patterns that eliminate hot and cold spots through field interference, not mechanical motion. This substitutes electromagnetic control for mechanical systems, reducing device complexity while maintaining heating uniformity.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the parameters of microwave sources (amplitude and phase) to control the electromagnetic field distribution. By adjusting these parameters, the system creates desired mode patterns (e.g., rotating patterns, standing waves) that achieve uniform heating without mechanical movement. This parameter control approach replaces physical manipulation with electrical control.

Inventive Principle:
Principle #35Parameter changes

2Temperature

If quadratic arrangement with phase-shift is used to produce rotating microwave pattern, then heating uniformity is improved, but device complexity increases due to advanced feeding structure

Engineering Contradiction:
Improveheating uniformityVSAvoidfeeding structure complexity
Core Design Contradiction:
TemperatureVSDevice complexity

Solution Approach 1:

The patent segments the microwave generation into multiple independent sources (at least two), each fed through separate waveguides. This segmentation allows independent control of amplitude and phase for each source, enabling flexible mode synthesis without complex mechanical or structural arrangements. The feeding structure becomes simpler because each source operates independently with standard waveguide connections.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent creates a multi-functional microwave heating system where multiple sources can generate different mode patterns (rotating, standing wave, uniform distribution) by controlling amplitude and phase relationships. This universal approach eliminates the need for specialized feeding structures designed for specific patterns, as the same segmented source configuration can adapt to various heating requirements.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Temperature

If multiple magnetrons with directional couplers are used, then heating uniformity is improved, but device complexity and energy loss increase

Engineering Contradiction:
Improveheating uniformityVSAvoidfeeding system complexity
Core Design Contradiction:
TemperatureVSDevice complexity

Solution Approach 1:

The patent replaces mechanical mode stirrers and complex coupling mechanisms with electromagnetic field synthesis using multiple independent sources. Each source is controlled electronically to create the desired field distribution, eliminating the need for directional couplers and complex mechanical synchronization mechanisms. This reduces both device complexity and energy losses associated with multiple coupling stages.

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 solution provides improved heating uniformity and energy efficiency by regulating microwave sources based on field sensor measurements, reducing the risk of field cancellation and unwanted frequency components, and optimizing heating patterns without requiring advanced or non-standard designs.

Implementation Method 1

at least two field sensors for measuring the field strengths of the microwave energy in the cavity

Methodology Applied
Scientific EffectElectromagnetic field sensing: Electromagnetic Induction

Implementation Method 2

at least two microwave sources for feeding microwave energy into the cavity

Methodology Applied
Scientific EffectMicrowave heating: Dielectric Heating

Data Source

PatentEP2239994B1A microwave oven with a regulation system using field sensors
Publication Date: 2018.11.28 WHIRLPOOL CORP
  • EP2239994B1 patent drawingFigure 1
  • EP2239994B1 patent drawingFigure 2~3
  • EP2239994B1 patent drawingFigure 4

AI summary

A microwave heating device and a method for heating a load using microwaves are provided. The microwave heating device (100) comprises a cavity (150) adapted to receive a load and at least two microwave sources (110, 112) for feeding microwave energy into the cavity through at least two feeding ports (110, 112), respectively. The microwave heating device further comprises at least two field sensors (160, 162) adapted to measure field strengths of the microwave energy in the cavity. A first field sensor (160) is arranged at a first location for measuring the field strength representative of a mode fed from a first feeding port (120) and a second field sensor (162) is arranged at a second location for measuring the field strength representative of a mode fed from a second feeding port (122). The microwave heating device further comprises a control unit (180) connected to the microwave sources and the field sensors for regulating the microwave sources based on the measured field strengths. The present invention is advantageous in that it enables uniform heating of the load in the cavity.