Hair Straightener Thermal Control Using Temperature-Power Feedback
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Solution Overview
Problem
Hair straighteners face challenges in maintaining consistent temperature across heating plates due to thermal resistance between ceramic and aluminium components, leading to inefficient heat transfer and potential hair damage from temperature fluctuations.
Innovation Solution
A control system that combines temperature and power measurements to adjust power delivery to the heating element, using thermal resistance data to calculate the necessary power adjustments and maintain a constant temperature at the heating surface, even under thermal loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the temperature of the heating plates is increased to enable fast styling, then the styling speed is improved, but the risk of hair damage increases when the device is moved slowly through the hair
Solution Approach 1:
The patent employs a temperature sensor to continuously monitor the temperature of the heating element and uses this feedback to adjust the power delivery dynamically. The control system modifies the power supplied to the heating element based on the measured temperature, ensuring the heating plate maintains the desired temperature range. This feedback mechanism allows the system to adapt to varying thermal conditions, preventing both overheating (which causes hair damage) and insufficient heating (which reduces styling efficiency).
Solution Approach 2:
The patent implements dynamic power adjustment by varying the power supplied to the heating element in real-time based on thermal conditions. The system transitions from static power delivery to dynamic control, where the power level is continuously adapted to maintain optimal temperature. This dynamic approach enables the heating plate to quickly respond to changes in thermal load (such as when hair is applied), ensuring consistent styling performance while preventing temperature excursions that could damage hair.
2Speed
If the power to the heating element is increased to quickly heat the hair to the glass transition temperature, then the heating speed is improved, but the temperature control precision deteriorates due to thermal resistance between the ceramic heating element and the aluminium heating plate
Solution Approach 1:
The temperature sensor provides continuous feedback on the actual temperature of the heating element, which the control system uses to adjust power delivery. This closed-loop control compensates for temperature drops across the ceramic-aluminium interface by detecting the actual heating element temperature and modifying power input accordingly, maintaining precise temperature control despite thermal resistance in the interface.
Solution Approach 2:
The patent replaces direct physical temperature measurement at the heating plate surface with an indirect measurement approach. Instead of placing a temperature sensor directly on the heating plate (which would require complex isolation arrangements), the system uses a temperature sensor on the heating element combined with power measurement and thermal resistance data to calculate and infer the heating plate temperature. This substitution simplifies the system while maintaining measurement accuracy.
3Device complexity
If a temperature sensor is attached to the ceramic heating element for cost reasons, then the device complexity is reduced, but the temperature measurement accuracy deteriorates because it does not measure the actual heating plate surface temperature
Solution Approach 1:
The patent replaces direct temperature measurement at the heating plate surface with an indirect measurement and calculation approach. The system measures the temperature of the heating element and the power supplied to it, then uses the known thermal resistance of the ceramic-aluminium interface to calculate the heating plate temperature. This substitution avoids the need for complex isolated temperature sensing arrangements while providing accurate temperature information for control purposes.
Solution Approach 2:
The patent introduces power measurement as an intermediary parameter to bridge the gap between heating element temperature and heating plate temperature. By measuring both the heating element temperature and the power supplied, the system can infer the thermal conditions at the heating plate surface through the known thermal resistance relationship. This intermediary measurement approach enables accurate temperature control without direct contact sensing at the heating plate.
4Stability of the object's composition
If the thermal resistance between the ceramic heating element and the aluminium heating plate is reduced to improve heat transfer, then the temperature uniformity is improved, but the risk of overheating the ceramic element increases
Solution Approach 1:
The temperature sensor on the heating element provides continuous feedback on its temperature, allowing the control system to monitor and limit the maximum temperature reached by the ceramic element. This feedback mechanism enables the system to maintain good thermal contact (for temperature uniformity) while simultaneously preventing the ceramic element from overheating, as the control system can reduce power input when the heating element temperature approaches unsafe levels.
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 ensures consistent temperature control at the heating surface, improving styling efficiency and reducing the risk of hair damage by quickly compensating for temperature drops, thereby maintaining optimal styling conditions.
Implementation Method 1
a heater having a heating element for receiving electrical power and for converting the electrical power into heat to heat a heating surface of the heater
Implementation Method 2
Due to the thermal resistance between the ceramic heating element and the heating plate (and due to the thermal resistance of the heating plate and the ceramic heating element themselves) there is a temperature drop across the ceramic-aluminium assembly
Data Source
AI summary
The present invention provides a heating apparatus for heating a load. The heating apparatus comprises a heater having a heating element for receiving electrical power and for converting the electrical power into heat to heat a heating surface of the heater. The heating apparatus also comprises a temperature sensor for sensing and outputting a measurement of the temperature of the heating element, a power actuator for providing the electrical power to the heating element of the heater, a power sensor for sensing and outputting a measurement of the power provided to the heating element by the power actuator, and control circuitry for controlling the power actuator to control the power delivered by the power actuator to the heating element. The control circuitry is configured to receive the temperature measurement from the temperature sensor, receive the power measurement from the power sensor, combine the temperature measurement and the power measurement, and control the power actuator in dependence upon the combined temperature measurement and power measurement. This ensures that the temperature of the heating surface is constant throughout a period when the load is applied.