Reversible Hot-Air Blower Timing to Prevent Heater Overheating
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Solution Overview
Problem
Existing cooking appliances with reversible hot-air motors face overheating issues when the direction of rotation is reversed, leading to the need for power reduction, which disrupts cooking behavior and requires additional temperature sensors or reduced heater performance.
Innovation Solution
A cooking appliance design that reverses the hot-air motor's direction of rotation predominantly during the heating off phase, with a controller managing the reversal at the start of deceleration or phase-out, allowing extended heat dissipation and preventing overheating by adjusting cycle times and threshold values based on operating modes and temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the direction of rotation of the hot-air motor is reversed, then the air flow direction can be changed, but the heating element overheats due to lack of heat dissipation
Solution Approach 1:
The controller initiates the reversal of the hot-air motor's direction of rotation at the start of the phase-out period, before the heating element needs to dissipate heat. This preliminary timing ensures that when the motor reverses and heat dissipation is reduced, the heating element is not yet generating full heat, thus preventing overheating while achieving the desired air flow direction change.
Solution Approach 2:
The system dynamically adjusts the timing of motor reversal based on the heating element's operational cycle. By synchronizing the reversal action with the phase-out period of the heating element, the system creates a dynamic coordination between heat generation and heat dissipation processes, ensuring that reversal occurs when heat load is minimal.
2Temperature
If the heating power is reduced to prevent overheating during motor reversal, then overheating is avoided, but the cooking behavior of the appliance is greatly changed
Solution Approach 1:
Instead of reducing heating power during reversal, the system performs the reversal action preliminarily at the start of the phase-out period when heating power is already being reduced or stopped. This eliminates the need for additional power reduction measures while maintaining both overheating prevention and normal cooking performance.
3Speed
If the direction of rotation is reversed during heating on phase, then air flow direction changes quickly, but the heating element overheats due to residual heat
Solution Approach 1:
The controller is configured to initiate reversal at the start of the phase-out period, which is the earliest safe moment when heating power is already reduced. This preliminary timing allows the system to achieve quick reversal while ensuring that residual heat from the heating element will not cause overheating, as the heating element is already in its cooling phase.
4Temperature
If the phase-out period is extended to allow complete motor reversal, then overheating is prevented, but the cooking operation is disrupted
Solution Approach 1:
By initiating reversal at the very start of the phase-out period rather than waiting for the phase-out to complete, the system minimizes the extension of the phase-out duration. The reversal process begins immediately when heating power is reduced, allowing the motor to complete its reversal within the existing phase-out window without requiring significant additional time, thus minimizing cooking disruption.
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 prevents overheating, allows for high-performance heater operation without additional temperature sensors, and minimizes disruptions to cooking operations by optimizing the reversal timing and phase management.
Implementation Method 1
a hot-air blower (13) with a reversible hot-air motor (15)
Implementation Method 2
a heater (16) which can be operated in a clocked manner with on and off phases
Implementation Method 3
the controller (17) is set up to initiate the reversal of the direction of rotation of the hot-air motor (15) at the start of a phase-out
Data Source
AI summary
Cooking appliance (11), having a hot-air blower (13) with a hot-air motor (15) and a heater (16) that can be operated in a clocked manner, the direction of rotation of the hot-air motor (15) being reversible, the cooking appliance (11) being set up to change the direction of rotation in particular purposefully reverse only during a phase-out (apv; ap) of the heating (16).