Capacitive Cooktop Touch Control With Cancel Electrodes
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Solution Overview
Problem
Conventional cooking devices experience poor usability due to unintentional heating operation changes when water droplets or cleaning occurs around touch switches, leading to erroneous detections and unintended operation transitions.
Innovation Solution
A cooking device with capacitance-type touch switches and a cancel electrode near the key electrodes, which detects capacitance changes to differentiate between intended operations and unintended conditions like water or food adhesion, preventing erroneous heating turn-offs and improving usability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a peripheral-condition detection section is used to detect objects around the operation section, then heating operations are prevented from being unintentionally turned on, but heating operations are unintentionally turned off when water droplets or cleaning occurs
Solution Approach 1:
The detection function is segmented into two independent detection sections: a peripheral-condition detection section for detecting objects around the operation section, and a cancel electrode section for detecting objects near the key electrodes. Each section independently monitors its specific area, allowing the system to distinguish between legitimate operations and unintended activations caused by water or cleaning activities.
Solution Approach 2:
The cancel electrode acts as an intermediary detection element positioned between the heating section and the key electrodes. It mediates the detection process by providing additional information about the presence of objects near the touch switches, enabling the control unit to make more accurate judgments about whether a detected object represents a legitimate operation or an unintended activation.
2Speed
If capacitance-type touch switches are used for operation input, then operation responsiveness is improved, but erroneous detections occur when water or food adheres to the switches
Solution Approach 1:
The detection area is segmented into multiple zones monitored by different electrodes: the key electrodes for operation input and the cancel electrode for peripheral monitoring. This segmentation allows the system to differentiate between capacitance changes caused by intentional touch operations and those caused by water or food adhesion, maintaining both responsiveness and accuracy.
Solution Approach 2:
The control unit continuously monitors capacitance values from both the key electrodes and the cancel electrode, using this feedback to dynamically adjust its judgment. When the cancel electrode detects capacitance changes indicative of water or food presence, the control unit uses this feedback to prevent erroneous interpretations of key electrode signals, thereby maintaining detection accuracy under contamination conditions.
3Measurement precision
If the touch switch detection sensitivity is increased to improve operation detection, then operation detection accuracy is improved, but false positives increase when objects are placed near the switches
Solution Approach 1:
The detection system is divided into functionally independent detection zones: the key electrode detection zone for operation input and the cancel electrode detection zone for peripheral monitoring. This spatial segmentation allows the system to maintain high detection sensitivity in the key electrode zone while using the cancel electrode zone to filter out false positives caused by objects placed near but not on the switches.
Solution Approach 2:
The control unit dynamically adjusts its detection logic based on real-time capacitance readings from both electrodes. When the cancel electrode detects significant capacitance changes, the control unit dynamically modifies its interpretation of key electrode signals, reducing sensitivity to prevent false positives while maintaining operation detection capability. This dynamic adjustment allows the system to adapt to different operational contexts.
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 effectively prevents unintentional heating operation changes and enhances usability by accurately distinguishing between intended and unintended touch switch activations, ensuring stable cooking conditions even during cleaning or food placement.
Implementation Method 1
capacitance-type touch switches, each of which includes a key electrode provided on a back surface of the top plate; and a control unit operable to detect capacitances formed between the key electrodes and a ground
Implementation Method 2
the control unit detects a capacitance formed between the cancel electrode and the ground, when the control unit continuously detects, for a time equal to or more than a second predetermined time but less than a third predetermined time, that the capacitance of the cancel electrode is increased
Data Source
AI summary
There is provided a cooking device capable of preventing heating operations from being unintentionally turned on and off and the setting of heating operations from being changed even when water droplets are scattered around touch switches or the vicinity of the touch switches is wiped with a damp cloth or the like. Left and right cancel electrodes (5a, 5b) are provided near the key electrodes between the positions of left and right heating coils (3a, 3b) and the positions of the key electrodes (4a1, 4a2, 4a3, 4b1, 4b2, 4b3). A control unit (6) changes over between validity and invalidity of inputting through the key electrodes based on whether or not a change of capacitances of the left and right cancel electrodes (5a, 5b) is equal to or more than a predetermined amount.