Inductive Susceptor Heating With Resistance-Based Temperature Control
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Solution Overview
Problem
Inductive heating devices for aerosol-forming substrates lack a method to efficiently measure and control the operating temperature of the substrate, as temperature measurement is not directly possible due to contactless heating.
Innovation Solution
An inductive heating device with a DC power source, power supply electronics including a microcontroller that determines the apparent ohmic resistance from DC supply voltage and current, allowing for temperature calculation and control of the susceptor, which is inductively coupled to the aerosol-forming substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If inductive heating is used to heat the aerosol-forming substrate, then contactless heating is achieved, but temperature measurement becomes impossible
Solution Approach 1:
The patent introduces an intermediary measurement approach by monitoring the electrical properties (impedance, resistance, or quality factor) of the inductor itself, which changes in response to temperature variations of the heated substrate. This indirect measurement method enables temperature monitoring without direct thermal contact, resolving the contradiction between contactless heating and temperature measurement capability
Solution Approach 2:
The system implements feedback control by continuously monitoring the inductor's electrical properties and using this information to adjust the heating power. The microcontroller processes the measured impedance or quality factor changes and modulates the heating element accordingly, enabling precise temperature control despite the contactless heating method
2Measurement precision
If a heating blade is inserted into the tobacco plug, then direct temperature measurement is possible, but the device structure becomes more complex
Solution Approach 1:
The inductor serves multiple functions simultaneously: it acts as both the heating element (generating electromagnetic fields for inductive heating) and the temperature sensor (detecting temperature changes through impedance or quality factor variations). This multi-functionality eliminates the need for separate heating and sensing components, reducing device complexity while maintaining measurement capability
Solution Approach 2:
The inductor performs self-diagnosis by monitoring its own electrical properties, which change in response to the thermal environment. The system uses the inductor's inherent electrical characteristics (impedance, resistance, quality factor) as temperature indicators, allowing the heating element to also serve as the sensing element without requiring additional external sensors
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
Enables efficient and precise temperature control of the aerosol-forming substrate, achieving temperatures between 200-400 degrees Celsius within a short time, with a compact and robust heating device design.
Implementation Method 1
The alternating magnetic field of the inductor generates eddy currents and hysteresis losses in the susceptor, causing the susceptor to heat the aerosol-forming substrate
Implementation Method 2
The alternating magnetic field of the inductor generates eddy currents and hysteresis losses in the susceptor, causing the susceptor to heat the aerosol-forming substrate
Implementation Method 3
The inductive heating device comprises an inductor arranged in thermal proximity of the aerosol-forming substrate
Implementation Method 4
the inductor of the LC load network is inductively coupled to the susceptor of the aerosol-forming substrate during operation
Data Source
AI summary
An inductive heating device heats an aerosol-forming substrate including a susceptor. The device includes a device housing, a DC power source for providing a DC supply voltage and a DC current, power supply electronics including a DC/AC converter, the DC/AC converter including an LC load network including a series connection of a capacitor and an inductor having an ohmic resistance, a cavity in the device housing for accommodating a portion of the aerosol-forming substrate to inductively couple the inductor of the LC load network to the susceptor. The inductor is embedded in the device housing at a proximal end of the device housing to surround the cavity which is also arranged at the proximal end of the device housing. A microcontroller determines from the DC supply voltage and the DC current an apparent ohmic resistance, and from the apparent ohmic resistance the temperature of the susceptor.