Oven Broil Preheating Control for Cold-Start Temperature Accuracy
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Solution Overview
Problem
Oven appliances often prematurely turn off the broil heating element during preheating due to discrepancies between sensed and actual center oven temperatures, especially when starting from a cold condition, leading to suboptimal cooking performance.
Innovation Solution
A control algorithm that differentiates between 'cold start' and 'hot start' preheating cycles, allowing the broil heating element to operate longer by using alternative temperature thresholds and cycling routines to maintain the center oven temperature within desired limits, ensuring the broil heating element remains active even after the sensed temperature exceeds a certain threshold during cold starts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control algorithm turns off the heating element when the sensed temperature exceeds the maximum desired temperature threshold, then the center oven temperature is prevented from exceeding the threshold, but the heating element is turned off prematurely during cold-start preheat cycles, harming cooking performance
Solution Approach 1:
The control algorithm identifies cold-start conditions before normal temperature control begins, and applies a different temperature threshold strategy during the preheat phase. This preliminary action allows the heating element to remain on longer during cold starts, improving cooking performance while still preventing overheating once the oven reaches normal operating temperature.
Solution Approach 2:
The system dynamically adjusts the temperature threshold based on the oven's current state. During cold-start preheat cycles, a higher temperature threshold is permitted, allowing the heating element to operate longer. Once the oven reaches steady-state operation, the threshold reverts to the maximum desired temperature. This dynamic adaptation resolves the contradiction between maintaining temperature control accuracy and improving cooking performance.
2Ease of operation
If the sensed temperature is used as the control parameter, then the control algorithm can monitor temperature easily, but the sensed temperature differs significantly from the actual center oven temperature during cold-start preheating, leading to premature shutdown
Solution Approach 1:
The system changes the interpretation of the temperature parameter based on the operational phase. During cold-start preheat, the control algorithm recognizes that the sensed temperature reading does not accurately reflect the center oven temperature, and adjusts the control strategy accordingly by permitting higher sensed temperatures. This parameter adaptation maintains measurement simplicity while compensating for the measurement inaccuracy.
3Reliability
If the heating element is turned off early to maintain temperature limits, then temperature safety is ensured, but the preheating time and cooking efficiency are reduced
Solution Approach 1:
The preheating process is segmented into distinct phases: cold-start preheat and steady-state operation. During the cold-start phase, the system permits higher temperatures and longer heating element operation to reduce preheat time. Once the oven reaches steady-state, the system transitions to a more conservative temperature control mode to ensure safety. This segmentation allows the system to optimize for speed during preheat while maintaining safety during cooking.
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 approach improves cooking performance by maintaining the center oven temperature within desired limits and extending the broil heating element's operation time during preheating, especially when starting from a cold condition, thereby enhancing overall cooking efficiency.
Implementation Method 1
Heating elements are positioned within the cooking chamber to provide heat to food items located therein. The heating elements can include a bake heating element positioned at a bottom of the cooking chamber and/or a broil heating element positioned at a top of the cooking chamber.
Implementation Method 2
Oven appliances may also include a convection heating assembly, which may include a convection heating element and fan or other mechanism for creating a flow of heated air within the cooking chamber.
Implementation Method 3
The temperature of the cooking chamber is often measured by a temperature sensor placed on the top or in the back of the cooking chamber.
Data Source
AI summary
A system and method for preheating a cooking chamber of an oven appliance is provided. The oven appliance may include one or more heating elements that operate according to a control algorithm that prevents the center oven temperature from exceeding a maximum desired temperature threshold. The control algorithm accounts for discrepancies between the measured oven temperature and the actual center oven temperature, particularly when preheating a cold oven. As a result, the control algorithm selectively operates one or more of the heating elements after the measured oven temperature is above the maximum desired temperature threshold. Preheating the cooking chamber in this manner will improve overall cooking performance.