Variable-Pitch Inductor Coil for Uniform Susceptor Heating

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Solution Overview

Problem

Conventional inductor coils in aerosol-generating devices with susceptor elements often fail to provide uniform temperature control, leading to non-uniform heating profiles and undesirable condensation/re-evaporation of sensorial mediums, which affects the performance of nicotine and acid delivery in aerosol-generating systems.

Innovation Solution

The inductor coil is designed with varying turns per unit length and cross-sectional area along its length, specifically with fewer turns and a larger cross-section in the central portion, to achieve a more uniform magnetic flux density and temperature distribution across the susceptor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a conventional inductor coil with constant turns per unit length is used, then the device structure is simple, but the temperature distribution across the susceptor is non-uniform

Engineering Contradiction:

Improvetemperature distribution uniformityVSAvoidinductor coil structure

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The inductor coil is designed with varying turns per unit length along its length, creating different magnetic field strengths in different regions. The first and second portions have higher turns density to compensate for lower magnetic flux density at the ends of the susceptor, while the central portion has lower turns density to avoid excessive heating at the center, achieving uniform temperature distribution across the entire susceptor.

Inventive Principle:

Principle #3Local quality

2Stress or pressure

If the inductor coil has uniform turns per unit length, then the manufacturing process is simple, but the magnetic flux density is non-uniform across the susceptor

Engineering Contradiction:

Improvemagnetic flux density uniformityVSAvoidinductor coil turns distribution

Core Design Contradiction:

Stress or pressureVSManufacturing precision

Solution Approach 1:

The inductor coil is divided into multiple portions along its length, with each portion having a different number of turns per unit length. The first and second portions (at the ends) have higher turns density while the central portion has lower turns density, creating a tailored magnetic flux density distribution that compensates for natural field variations and achieves uniform heating across the susceptor.

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If a conventional inductor coil is used, then the device complexity is low, but condensation and re-evaporation of sensorial mediums occur due to non-uniform heating

Engineering Contradiction:

Improvecondensation and re-evaporationVSAvoidinductor coil design

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

By varying the turns per unit length along the inductor coil, the magnetic flux density is optimized at different positions. The increased turns density at the ends compensates for the naturally lower magnetic flux density in those regions, preventing localized overheating or underheating that would cause condensation and re-evaporation of sensorial mediums in the aerosol-generating article.

Inventive Principle:

Principle #3Local quality

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 configuration ensures a uniform temperature profile along the susceptor, enhancing the performance of aerosol-generating systems by maintaining consistent nicotine and acid delivery, preventing condensation and re-evaporation issues.

Implementation Method 1

the inductor generates an alternating magnetic field to generate eddy currents and hysteresis losses in the susceptor element, causing the susceptor element to heat up

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

the inductor generates an alternating magnetic field to generate eddy currents and hysteresis losses in the susceptor element

Methodology Applied

Scientific EffectEddy currents: Eddy Currents

Implementation Method 3

the inductor generates an alternating magnetic field to generate eddy currents and hysteresis losses in the susceptor element

Methodology Applied

Scientific EffectHysteresis losses: Hysteresis

Implementation Method 4

an inductive heater is used rather than a resistive heating element. The inductive heater typically comprises an inductor forming part of the aerosol-generating device and a conductive susceptor element

Methodology Applied

Scientific EffectInductive heating: Induction Heating

Data Source

PatentUS12471190B2Variable pitch and variable radius inductor coil designs within an aerosol-generating device

Publication Date: 2025.11.11 PHILIP MORRIS PRODUCTS SA

AI summary

An aerosol-generating device is provided, including: a housing defining a chamber configured to receive at least one susceptor and at least one aerosol-forming substrate, the chamber having a length along a longitudinal axis thereof extending from a first end of the chamber to a second end of the chamber; and an inductor coil provided within the housing, disposed around the chamber, and extending along at least a portion of the length of the chamber, the inductor coil including a first portion disposed closest to the first end of the chamber, a second portion disposed closest to the second end of the chamber, and a third portion disposed between the first and the second portions, and a number of turns per unit length in the third portion is less than a number of turns per unit length in one or both of the first and the second portions.