Electric Cooktop Temperature Control Using Rate-of-Change Criterion
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Solution Overview
Problem
Operating electric heating elements on cooktop appliances at high heat settings poses challenges in avoiding overheating while preventing unnecessary deactivation, which is difficult to control effectively.
Innovation Solution
A cooktop appliance with an electric heating element positioned below a ceramic plate, equipped with a temperature sensor offset from the center and a controller that calculates a control criterion from temperature measurements over time to selectively terminate electrical power via a relay when the criterion exceeds a threshold, ensuring safe operation and preventing overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the electric heating element operates at high heat setting, then the heating power is improved, but the temperature control reliability deteriorates due to risk of overheating
Solution Approach 1:
The controller continuously receives temperature measurements from the temperature sensor and uses this feedback to dynamically control the heating element operation. The controller calculates the control criterion based on temperature change rate and compares it to threshold values, adjusting the heating element operation accordingly to maintain safe temperatures while enabling high power operation.
Solution Approach 2:
The system proactively monitors temperature changes and calculates control criteria before dangerous overheating occurs. By detecting the rate of temperature change and predicting future temperature levels, the system can take preventive action by controlling the heating element before safety limits are exceeded, rather than merely reacting after overheating begins.
2Object-affected harmful factors
If the temperature control is made more sensitive to prevent overheating, then the safety is improved, but the false deactivation rate increases
Solution Approach 1:
The system changes the control parameter from absolute temperature threshold to temperature change rate (dT/dt). This parameter transformation allows the system to detect potential overheating conditions by monitoring how quickly temperature is rising, enabling earlier and more accurate intervention while reducing false alarms from temporary temperature fluctuations that don't represent dangerous heating trends.
Solution Approach 2:
The invention replaces simple on/off thermal control with a computational control approach. The controller calculates the control criterion using temperature change rate and compares it to threshold values, substituting mechanical thermal inertia-based protection with intelligent algorithmic control that can distinguish between normal cooking temperature variations and dangerous overheating conditions.
3Measurement precision
If a temperature sensor is positioned at the center of the heating element, then the temperature measurement accuracy is improved, but the measurement reliability deteriorates due to localized hot spots
Solution Approach 1:
The system deliberately positions the temperature sensor asymmetrically away from the center of the heating element. This asymmetric positioning avoids the localized hot spot at the center, providing a more representative measurement of the overall heating zone temperature. The offset position captures the average temperature trend without being skewed by extreme localized conditions.
Solution Approach 2:
The temperature sensor acts as an intermediary measurement point that indirectly monitors the heating element performance. By positioning it in the offset location, the sensor measures the thermal field in a representative zone that reflects overall heating conditions without directly contacting the most intense heat source, providing reliable data for control decisions.
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 regulates the heating of utensils on the cooktop, maintaining temperatures below a threshold value, such as 750° F, while minimizing unnecessary deactivation of the heating element, thus addressing the challenge of controlling high heat settings safely.
Implementation Method 1
A temperature sensor positioned above the heating element and offset from a center of the heating element
Implementation Method 2
Certain cooktop appliances include electric heating elements for heating pots, pans and other containers
Data Source
AI summary
A cooktop appliance includes an electric heating element positioned below a ceramic plate. A temperature sensor is positioned proximate a bottom surface of the ceramic plate. The temperature sensor may be offset from a center of the electric heating element. A controller is configured to receive a plurality of temperature measurements from the temperature sensor, determine a change between the plurality of temperature measurements over time, calculate a value of a control criterion with the change between the plurality of temperature measurements over time, and open a relay in response to the value of the control criterion passing a threshold value. A related method for operating a cooktop appliance is also provided.