Microwave Heating Reflected Wave Detection for Load Measurement
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Solution Overview
Problem
Conventional microwave ovens face challenges in evenly heating objects due to the presence of incident and reflected waves within the waveguide, and they often lack accurate load detection mechanisms, especially when objects are not placed directly on a table plate, leading to inefficient heating and potential measurement errors.
Innovation Solution
A microwave heating apparatus that employs a reflected wave detector to determine the quantity of an object by measuring changes in reflected waves within the waveguide, eliminating the need for a load detector and allowing for efficient heating control based on the detected quantity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a directional coupler is used to detect incident and reflected waves in the waveguide, then the heating control accuracy is improved, but the device size becomes considerably large
Solution Approach 1:
The patent extracts only the necessary detection function from a complete directional coupler system. Instead of using a full directional coupler that separates incident and reflected waves, the invention uses a simplified detection device that only detects the reflected wave, achieving adequate heating control with much reduced size.
Solution Approach 2:
The patent introduces a detection device as an intermediary between the waveguide and the control system. This intermediary device provides sufficient measurement capability for heating control without requiring the complex structure of a complete directional coupler, thus resolving the size-precision contradiction.
2Device complexity
If a weight detector is used to determine object quantity, then the heating control is simplified, but the measurement accuracy deteriorates when the tray is not placed directly on the table plate
Solution Approach 1:
The patent replaces the mechanical weight detection system with an electromagnetic detection system. Instead of measuring the mechanical load on the table plate, the invention detects changes in the reflected wave characteristics caused by the object's presence and quantity, eliminating the need for direct mechanical contact and improving measurement reliability.
Solution Approach 2:
The reflected wave serves as an intermediary that indirectly indicates the object quantity. Rather than directly measuring the object's weight or mass, the system detects changes in the microwave reflected wave, which are influenced by the object's dielectric properties and quantity, providing accurate measurement without direct contact.
3Ease of operation
If the tray load is applied to a shelf instead of the table plate, then the object can be heated, but the weight detection fails leading to inaccurate quantity determination
Solution Approach 1:
The patent replaces the mechanical load-based detection system with an electromagnetic field-based detection system. The reflected wave detection method does not depend on the mechanical support structure or tray placement position, allowing flexible operation while maintaining accurate object quantity determination through electromagnetic interaction with the object.
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 determination of the object's quantity and optimized heating time, ensuring even heating and energy efficiency by utilizing the reflected wave detection to control microwave absorption, thereby improving heating performance and accuracy.
Implementation Method 1
a reflected wave detector that detects the at least part of the reflected wave inside the waveguide
Implementation Method 2
a magnetron that generates a microwave to be supplied to a heating chamber; a waveguide through which the microwave generated by the magnetron propagates to the heating chamber
Implementation Method 3
When the object is present, the reflected wave is weak, because the microwave is absorbed by the object
Implementation Method 4
a controller that controls an output of the magnetron and a direction in which the radiation antenna faces, based on the quantity determined by the quantity determiner
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3C
AI summary
The present invention includes directional coupler (30) that detects at least part of a reflected wave inside waveguide (4). When object (21) to be heated is absent, a reflected wave is strong, because there is nothing to absorb a microwave. When object (21) is present, the reflected wave is weak, because the microwave is absorbed by object (21). As a quantity of object (21) becomes greater, a larger amount of microwave is absorbed by object (21), and thus the reflected wave is weakened. It is thus possible to determine the quantity of object (21) from a reflected wave detection amount detected by directional coupler (30) without using a detector that detects a load.