Method of operating an inductively heated aerosol generating system

Abstract

A method for controlling an aerosol generation system, an aerosol generation system, and an aerosol generation device for the aerosol generation system. The aerosol generation system includes an induction heating arrangement configured to heat an aerosol-forming substrate and a power supply configured to supply power to the induction heating arrangement. The induction heating arrangement includes an induction heating element (10) including at least one susceptor (12, 14) heatable by transmission of a varying magnetic field to heat the aerosol-forming substrate, a first inductor coil (32), and a second inductor coil (34). The method includes driving a first varying current in the first inductor coil (32) to generate a first varying magnetic field for heating a first portion of the induction heating element (10), and controlling the first varying current to raise the temperature of the first portion of the induction heating element (10) from an initial temperature to a first operating temperature. The method further includes driving a second varying current in the second inductor coil (34) to generate a second varying magnetic field for heating a second portion of the induction heating element (10) and controlling the second varying current to raise the temperature of the second portion of the induction heating element (10) from an initial temperature to a second operating temperature, the second varying current not being driven when the first varying current is driven and the first varying current not being driven when the second varying current is driven.

Description

[Technical field]

[0001] The present disclosure relates to a method of controlling an aerosol generation system having an inductive heating arrangement, to an aerosol generation system having an inductive heating arrangement, and to an aerosol generation device having an inductive heating arrangement. [Background technology]

[0002] Numerous electrically operated aerosol generating systems have been proposed in the art in which an aerosol generating device having an electric heater is used to heat an aerosol-forming substrate, such as a tobacco plug. One purpose of such aerosol generating systems is to reduce well-known harmful smoke components of the type produced by the combustion and pyrolysis of tobacco in conventional cigarettes. Typically, the aerosol-generating substrate is provided as part of an aerosol-generating article that is inserted into a cavity of the aerosol generating device. In some known systems, a resistive heating element, such as a heating blade, is inserted into or around the aerosol-forming substrate when the article is received in the aerosol generating device in order to heat the aerosol-forming substrate to a temperature capable of releasing volatile components capable of forming an aerosol. In other aerosol generating systems, an induction heater is used rather than a resistive heating element. An induction heater typically comprises an inductor coil that forms part of the aerosol generating device and a susceptor that is disposed in thermal proximity to the aerosol-forming substrate. The inductor generates a fluctuating magnetic field that generates eddy currents and hysteresis losses in the susceptor, heating the susceptor and thereby the aerosol-forming substrate. Induction heating allows for aerosol generation without exposing the heater to an aerosol-generating article, which can improve the ease with which the heater can be cleaned.

[0003] Some known aerosol generating devices include multiple inductor coils, each arranged to heat a different portion of the susceptor. Such aerosol generating devices can be used to heat different portions of the aerosol-generating article at different times or to different temperatures. However, in such aerosol generating devices, it can be difficult to heat one portion of the aerosol-generating article without also indirectly heating adjacent portions of the aerosol-generating article.

[0004] It would be desirable to provide an aerosol generating device that reduces or overcomes these problems with known systems. Summary of the Invention

[0005] According to the present disclosure, there is provided a method of controlling an aerosol generating system, the aerosol generating system comprising an induction heating arrangement configured to heat an aerosol-forming substrate and a power source configured to supply power to the induction heating arrangement. The induction heating arrangement comprises an induction heating element including at least one susceptor heatable by transmission of a varying magnetic field to heat the aerosol-forming substrate, a first inductor coil, and a second inductor coil. The method includes driving a first varying current in the first inductor coil to generate a first varying magnetic field for heating a first portion of the induction heating element, and controlling the first varying current to increase a temperature of the first portion of the induction heating element from an initial temperature to a first operating temperature. The method further includes driving a second varying current in the second inductor coil to generate a second varying magnetic field for heating a second portion of the induction heating element, and controlling the second varying current to increase a temperature of the second portion of the induction heating element from an initial temperature to a second operating temperature. When the first varying current is driven the second varying current is not driven and when the second varying current is driven the first varying current is not driven.

[0006] In the present disclosure, the first varying current and the second varying current are not driven simultaneously. In other words, the first varying current and the second varying current are driven asynchronously. There is no overlap between ending the driving of the first varying current and starting the driving of the second varying current.

[0007] Advantageously, not driving the first varying current and the second varying current simultaneously may simplify the electronics required to provide the varying currents, which may facilitate easier and less costly manufacturing. Additionally, not driving the first varying current and the second varying current simultaneously may improve control of the temperature of the first portion of the induction heating element and the second portion of the induction heating element, which may facilitate generation of an aerosol with desirable properties.

[0008] According to the present disclosure, there is provided an aerosol generation system comprising an aerosol-forming substrate, an induction heating arrangement configured to heat the aerosol-forming substrate, a power supply configured to supply power to the induction heating arrangement, and a controller. The induction heating arrangement comprises an induction heating element including at least one susceptor heatable by transmission of a varying magnetic field to heat the aerosol-forming substrate, a first inductor coil, and a second inductor coil. The controller is configured to carry out the method steps described above.

[0009] Specifically, according to the present disclosure, an aerosol generating system is provided, comprising an aerosol-forming substrate, an induction heating arrangement configured to heat the aerosol-forming substrate, a power supply configured to supply power to the induction heating arrangement, and a controller. The induction heating arrangement includes an induction heating element including at least one susceptor heatable by transmission of a varying magnetic field to heat the aerosol-forming substrate, a first inductor coil, and a second inductor coil. The controller is configured to drive a first varying current in the first inductor coil to generate a first varying magnetic field for heating a first portion of the induction heating element, and control the first varying current to increase a temperature of the first portion of the induction heating element from an initial temperature to a first operating temperature. The controller is configured to drive a second varying current in the second inductor coil to generate a second varying magnetic field for heating a second portion of the induction heating element, and control the second varying current to increase a temperature of the second portion of the induction heating element from an initial temperature to a second operating temperature. The controller is further configured to drive the first varying current when the second varying current is not driven and to drive the second varying current when the first varying current is not driven.

[0010] According to the present disclosure, an aerosol generating device is provided, the aerosol generating device being configured to receive an aerosol-generating article comprising an aerosol-forming substrate and an induction heating element including at least one susceptor heatable by transmission of a varying magnetic field to heat the aerosol-generating substrate. The aerosol generating device comprises a first inductor coil, a second inductor coil, a power source configured to supply power to the first inductor coil and the second inductor coil, and a controller. The controller is configured to drive a first varying current in the first inductor coil to generate a first varying magnetic field for heating a first portion of the induction heating element of the aerosol-generating article received by the aerosol generating device, and control the first varying current to increase a temperature of the first portion of the induction heating element from an initial temperature to a first operating temperature. The controller is further configured to drive a second varying current in the second inductor coil to generate a second varying magnetic field for heating a second portion of the induction heating element of the aerosol-generating article received by the aerosol generating device, and control the second varying current to increase a temperature of the second portion of the induction heating element from an initial temperature to a second operating temperature. The controller is further configured to drive the first varying current when the second varying current is not driven and to drive the second varying current when the first varying current is not driven.

[0011] Specifically, according to the present disclosure, there is provided an aerosol generating apparatus comprising an induction heating arrangement configured to heat an aerosol-forming substrate, a power supply configured to supply power to the induction heating arrangement, and a controller. The induction heating arrangement includes an induction heating element including at least one susceptor heatable by transmission of a varying magnetic field to heat the aerosol-forming substrate, a first inductor coil, and a second inductor coil. The controller is configured to carry out the method steps described above.

[0012] Specifically, according to the present disclosure, an aerosol generating apparatus is provided, comprising an induction heating arrangement configured to heat an aerosol-forming substrate, a power supply configured to supply power to the induction heating arrangement, and a controller. The induction heating arrangement includes an induction heating element including at least one susceptor heatable by transmission of a varying magnetic field to heat the aerosol-forming substrate, a first inductor coil, and a second inductor coil. The controller is configured to drive a first varying current in the first inductor coil to generate a first varying magnetic field for heating a first portion of the induction heating element of an aerosol-generating article received by the aerosol generating apparatus, and control the first varying current to increase a temperature of the first portion of the induction heating element from an initial temperature to a first operating temperature. The controller is further configured to drive a second varying current in the second inductor coil to generate a second varying magnetic field for heating a second portion of the induction heating element of an aerosol-generating article received by the aerosol generating apparatus, and control the second varying current to increase a temperature of the second portion of the induction heating element from an initial temperature to a second operating temperature. The controller is further configured to drive the first varying current when the second varying current is not driven and to drive the second varying current when the first varying current is not driven.

[0013] As used herein, the term "aerosol-forming substrate" relates to a substrate having a capacity to release volatile compounds capable of forming an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. The aerosol-forming substrate is typically part of an aerosol-generating article.

[0014] As used herein, the term "aerosol-generating article" refers to an article that includes an aerosol-forming substrate capable of releasing a volatile compound capable of forming an aerosol. For example, the aerosol-generating article may be an article that generates an aerosol that can be directly inhaled by a user sucking or puffing on a mouthpiece at the proximal or user end of the system. The aerosol-generating article may be disposable. An article that includes an aerosol-forming substrate that includes tobacco may be referred to herein as a tobacco stick.

[0015] As used herein, the term "aerosol-generating device" refers to a device that interacts with an aerosol-forming substrate to generate an aerosol.

[0016] As used herein, the term "aerosol generating system" refers to the combination of an aerosol-generating article and an aerosol-generating device that work together to generate a respirable aerosol.

[0017] As used herein, the term "varying current" includes any current that changes with time to generate a varying magnetic field. The term "varying current" is intended to include alternating current. A varying current is an alternating current, and an alternating current generates an alternating magnetic field.

[0018] As used herein, the term "length" refers to the major dimension along the longitudinal axis of an aerosol-generating device, or along the longitudinal axis of an aerosol-generating article, or along the longitudinal axis of a component of an aerosol-generating device, or along the longitudinal axis of a component of an aerosol-generating article.

[0019] As used herein, the term "width" refers to the major transverse dimension of an aerosol generating device, an aerosol generating article, or a component of an aerosol generating device or an aerosol generating article, at a particular location along its length. The term "thickness" refers to the dimension in the transverse direction perpendicular to the width.

[0020] As used herein, the term "cross-section" is used to describe a cross-section along the length of an aerosol generating device or an aerosol generating article, or of a component of an aerosol generating device or an aerosol generating article, at a particular location in a direction perpendicular to the longitudinal axis.

[0021] As used herein, the term "proximal" refers to the user end or mouth end of an aerosol generating device or aerosol generating article. The proximal end of a component of an aerosol generating device or aerosol generating article is the end of the component closest to the user end or the mouth end of the aerosol generating device or aerosol generating article. As used herein, the term "distal" refers to the end opposite the proximal end.

[0022] The first varying current and the second varying current may be controlled such that in a first stage, the first varying current is supplied to the first inductor coil and in a second stage, the second varying current is supplied to the second coil.

[0023] In some embodiments, in a first stage, a first varying current and a second varying current are alternately driven to drive a first varying current in a first inductor coil and a second varying current in a second inductor coil.

[0024] In some embodiments, in the second stage, the first varying current and the second varying current are alternately driven to drive the first varying current in the first inductor coil and the second varying current in the second inductor coil.

[0025] The first stage may have a predetermined duration. The second stage may have a predetermined duration. The duration of the first stage and the duration of the second stage may be the same. The duration of the second stage may be different from the duration of the first stage. Advantageously, this may enable the system to heat the first portion of the aerosol-forming substrate and the second portion of the aerosol-forming substrate for different times. The duration of the second stage may be shorter than the duration of the first stage. The duration of the second stage may be longer than the duration of the first stage.

[0026] The duration of the first stage may be from about 50 seconds to about 200 seconds. The duration of the second stage may be from about 50 seconds to about 200 seconds. The combined duration of the first stage and the second stage may be from about 100 seconds to about 400 seconds. The combined duration of the first stage and the second stage may be from about 150 seconds to about 300 seconds.

[0027] In some embodiments, the system further comprises a puff detector configured to detect when a user puffs through the system to receive the aerosol. In these embodiments, the duration of the first stage may be based on a first predetermined number of puffs detected by the puff detector. The first predetermined number of puffs may be between 2 and 5. In these embodiments, the duration of the second stage may be based on a second predetermined number of puffs detected by the puff detector. The second predetermined number of puffs may be between 2 and 5. In these embodiments, the combined duration of the first stage and the second stage may be based on a combined predetermined number of puffs detected by the puff detector. The combined number of puffs may be between 3 and 10 user puffs.

[0028] In some preferred embodiments, the first stage is terminated after a first maximum number of puffs is detected or before a first maximum duration is reached. The first maximum number of puffs may be between 2 and 5 puffs and the first maximum duration is between 50 seconds and about 200 seconds.

[0029] In some preferred embodiments, the second stage is terminated after a second maximum number of puffs is detected or before the second maximum duration is reached. The second maximum number of puffs may be between 2 and 5, and the second maximum duration may be between 50 seconds and about 200 seconds.

[0030] The first varying current may be controlled to increase the temperature of the first portion of the induction heating element from an initial temperature according to a first operating temperature profile, the first temperature profile being a predetermined desired temperature of the first portion of the induction heating element over time, and if at any given time the actual temperature of the first portion of the induction heating element differs from the temperature of the first temperature profile at that time, the first varying current is adjusted to adjust the temperature of the first portion of the induction heating element to the temperature specified by the first temperature profile at that time.

[0031] Similarly, the second varying current may be controlled to increase the temperature of the second portion of the induction heating element from an initial temperature according to a second temperature profile, the second temperature profile being a predetermined desired temperature of the second portion of the induction heating element over time. If at any given time the actual temperature of the second portion of the induction heating element differs from the temperature of the second temperature profile at that time, the second varying current is adjusted to adjust the temperature of the second portion of the induction heating element to the temperature specified by the second temperature profile at that time.

[0032] In some embodiments, the first operating temperature profile is substantially constant. In some embodiments, the first operating temperature profile varies over time.

[0033] In some embodiments, the second operating temperature profile is substantially constant. In some embodiments, the second operating temperature profile varies with time.

[0034] In some embodiments, during at least a portion of the first stage, the first operating temperature profile is greater than the second operating temperature profile. In these embodiments, during at least a portion of the first stage, the first operating temperature profile is greater than the second operating temperature profile by at least about 50 degrees Celsius. The first operating temperature profile may be greater than the second operating temperature profile throughout the entire first stage.

[0035] In some embodiments, in the second stage, the first operating temperature profile and the second operating temperature profile are substantially the same, hi some embodiments, in the second stage, the second operating temperature profile is within about 5 degrees Celsius of the first operating temperature profile.

[0036] In some embodiments, during at least a portion of the second stage, the second operating temperature profile is greater than the first operating temperature profile. In these embodiments, during the second stage, the second operating temperature profile may be greater than the first operating temperature profile by no more than about 50 degrees Celsius.

[0037] In some embodiments, the first operating temperature profile is substantially constant during at least a portion of the first stage. The first operating temperature profile may be constant during the first stage.

[0038] In some embodiments, the first operating temperature profile is substantially constant during at least a portion of the second stage. The first operating temperature profile may be constant during the second stage.

[0039] In some embodiments, the second operating temperature profile is substantially constant during at least a portion of the second stage. The second operating temperature profile may be constant during the second stage.

[0040] The first operating temperature profile can be between about 180 degrees Celsius and about 300 degrees Celsius during at least a portion of the first stage. The first operating temperature profile can be between about 160 degrees Celsius and about 260 degrees Celsius during at least a portion of the second stage. The second operating temperature profile can be between about 180 degrees Celsius and about 300 degrees Celsius during at least a portion of the second stage.

[0041] In accordance with the present disclosure, an induction heating element for an aerosol generating system is provided.

[0042] The induction heating element may have any suitable shape. The induction heating element may have a unitary structure. The induction heating element may include multiple unitary structures. The induction heating element may be elongated. The induction heating element may have any suitable cross-section. For example, the induction heating element may have a circular, elliptical, square, rectangular, triangular, or other polygonal cross-section.

[0043] In some embodiments, the induction heating element may comprise an internal heating element. As used herein, the term "internal heating element" refers to a heating element configured to be inserted within the aerosol-forming substrate.

[0044] In some embodiments, the induction heating element may form part of the aerosol-generating device and may be configured to penetrate the aerosol-forming substrate when the aerosol-forming substrate is received by the device. In these embodiments, the internal heating element is preferably configured to be insertable into the aerosol-forming substrate. The internal heating element may be in the form of a blade. The internal heating element may be in the form of a pin. The internal heating element may be in the form of a cone. When the aerosol-generating device comprises a device cavity for receiving the aerosol-forming substrate, the internal heating element preferably extends into the device cavity.

[0045] In some embodiments, the induction heating element may form part of an aerosol-generating article that includes an aerosol-forming substrate. In these embodiments, the induction heating element may be embedded within the aerosol-forming substrate. In these embodiments, the induction heating element may be at least partially surrounded by the aerosol-forming substrate.

[0046] In some embodiments, the induction heating element may be an external heating element. As used herein, the term "external heating element" refers to a heating element configured to heat the outer surface of the aerosol-forming substrate. The external heating element is preferably configured to at least partially surround the aerosol-forming substrate when the aerosol-forming substrate is received by the aerosol generating device. The induction heating element may be configured to heat the outer surface of the aerosol-forming substrate when the aerosol-forming substrate is received in the induction heating element cavity.

[0047] In embodiments in which the induction heating element forms part of the aerosol generation device, the induction heating element may be configured to substantially surround the aerosol-forming substrate when the aerosol-forming substrate is received by the device.

[0048] In embodiments in which the induction heating element forms part of an aerosol-generating article comprising an aerosol-forming substrate, the induction heating element may surround the aerosol-forming substrate, hi these embodiments, the induction heating element may take the form of a wrapper wrapped around the aerosol-forming substrate.

[0049] The induction heating element may include a cavity for receiving the aerosol-forming substrate. The induction heating element may include an exterior and an interior opposite the exterior. The interior may at least partially define the induction heating element cavity for receiving the aerosol-forming substrate. A first portion of the induction heating element may be tubular and define a portion of the induction heating element cavity. A second portion of the induction heating element may be tubular and define a portion of the induction heating element cavity.

[0050] In some embodiments, the induction heating element comprises a plurality of internal cavities for receiving the aerosol-forming substrate, The internal cavity of a first portion of the induction heating element may form the first cavity of the induction heating element, and the internal cavity of a second portion of the induction heating element may form the second cavity of the induction heating element.

[0051] In some preferred embodiments, the induction heating element includes a single internal cavity for receiving the aerosol-forming substrate. In these embodiments, the internal cavity of the first portion of the induction heating element defines a portion of the single internal cavity of the induction heating element, and the internal cavity of the second portion of the induction heating element defines a second portion of the single internal cavity of the induction heating element. In some preferred embodiments, the induction heating element is a tubular induction heating element. An inner surface of the tubular induction heating element may define the induction heating element cavity.

[0052] In embodiments where the aerosol-generating device comprises a device cavity for receiving the aerosol-forming substrate, the induction heating element may at least partially surround the device cavity. The induction heating element cavity may be aligned with the device cavity.

[0053] In some embodiments, the induction heating arrangement includes at least one internal heating element and at least one external heating element.

[0054] In some embodiments, the aerosol-generating article comprises a first portion of an induction heating element and the aerosol-generating device comprises a second portion of the induction heating element.

[0055] In some embodiments, the aerosol-generating article comprises the second portion of the induction heating element and the aerosol-generating device comprises the first portion of the induction heating element.

[0056] The induction heating element includes at least one susceptor. The induction heating element may include a single susceptor. The induction heating element may consist of a single susceptor. A first portion of the induction heating element may include a first susceptor. A second portion of the induction heating element may include a second susceptor.

[0057] As used herein, the term "susceptor" refers to an element that includes a material capable of converting magnetic energy into heat. When the susceptor is located within a fluctuating magnetic field, the susceptor heats up. Heating of the susceptor can be the result of at least one of hysteresis losses and eddy currents induced within the susceptor, depending on the electrical and magnetic properties of the susceptor material.

[0058] The susceptor may comprise any suitable material. The susceptor may be formed from any material that may be inductively heated to a temperature sufficient to aerosolize the aerosol-forming substrate. A preferred susceptor may be heated to a temperature greater than about 250 degrees Celsius. A preferred susceptor may be formed from an electrically conductive material. As used herein, "electrically conductive" refers to a material that is electrically conductive and has a thermal conductivity of greater than 1x10 at 20 degrees Celsius. -4 It refers to a material having an electrical resistivity of ohm-meter (Ω.m) or less. A preferred susceptor may be formed from a thermally conductive material. As used herein, the term "thermally conductive material" is used to describe a material having a thermal conductivity of at least about 10 watts per meter·Kelvin (W / (mK)) at 23 degrees Celsius and a relative humidity of 50 percent as measured using the Modified Transient Plane Heat Source (MTPS) method.

[0059] Suitable materials for the susceptor include graphite, molybdenum, silicon carbide, stainless steel, niobium, aluminum, nickel, nickel-containing compounds, titanium, and composites of metallic materials. Some preferred susceptors include metal or carbon. Some preferred susceptors may include ferromagnetic materials, such as, for example, ferritic iron, ferromagnetic steel or stainless steel, ferromagnetic particles, and ferrite. Some preferred susceptors are made of ferromagnetic materials. Suitable susceptors may include aluminum. Suitable susceptors may be made of aluminum. The susceptor may include at least about 5 percent, at least about 20 percent, at least about 50 percent, or at least about 90 percent of ferromagnetic or paramagnetic materials.

[0060] Preferably, the susceptor is made from a material that is substantially impermeable to gas, in other words, the susceptor is preferably made from a material that is not gas permeable.

[0061] The susceptor of the induction heating element may have any suitable shape. For example, the susceptor may be elongated. The susceptor may have any suitable cross-section. For example, the susceptor may have a circular, oval, square, rectangular, triangular, or other polygonal cross-section.

[0062] The first portion of the induction heating element may be a tubular susceptor. The second portion of the induction heating element may be a tubular susceptor. The tubular susceptor includes an annular body defining an interior cavity. The susceptor cavity may be configured to receive the aerosol-forming substrate. The susceptor cavity may be an open cavity. The susceptor cavity may be open at one end. The susceptor cavity may be open at both ends.

[0063] In some embodiments having multiple susceptors, each susceptor may be substantially identical. For example, the second susceptor may be substantially identical to the first susceptor. Each susceptor may be formed from the same material. Each susceptor may have substantially the same shape and dimensions. Making each susceptor substantially identical to the other susceptors may allow each susceptor to heat to substantially the same temperature and at substantially the same rate when exposed to a given varying magnetic field.

[0064] In some embodiments, the second susceptor differs from the first susceptor in at least one characteristic. The second susceptor may be formed from a different material than the first susceptor. The second susceptor may have a different shape and size relative to the first susceptor. The second susceptor may have a length that is greater than the length of the first susceptor. Making each susceptor different from the other susceptors may allow each susceptor to be tailored to provide optimal heat for different aerosol-forming substrates.

[0065] In one example, a first aerosol-forming substrate may need to be heated to a first temperature to generate a first aerosol having desired properties, and a second aerosol-forming substrate may need to be heated to a second temperature different from the first temperature to generate a second aerosol having desired properties. In this example, the first susceptor may be formed from a first material suitable for heating the first aerosol-forming substrate to the first temperature, and the second susceptor may be formed from a second material, different from the first material, suitable for heating the second aerosol-forming substrate to the second temperature.

[0066] In another example, an aerosol-generating article may comprise a first aerosol-forming substrate having a first length and a second aerosol-forming substrate having a second length different from the first length such that heating the second aerosol-forming substrate generates a different amount of aerosol than heating the first aerosol-forming substrate. In this embodiment, the first susceptor may have a length substantially equal to the first length and the second susceptor may have a length substantially equal to the second length.

[0067] In some preferred embodiments, the first susceptor is an elongated tubular susceptor and the second susceptor is an elongated tubular susceptor. In these preferred embodiments, the first susceptor and the second susceptor may be substantially aligned. In other words, the first susceptor and the second susceptor may be coaxially aligned.

[0068] The induction heating element may include any suitable number of susceptors. The induction heating element may include a plurality of susceptors. The induction heating element may include at least two susceptors. For example, the induction heating element may include three, four, five, or six susceptors. When the induction heating element includes more than two susceptors, an intermediate element may be disposed between each pair of adjacent susceptors.

[0069] In some preferred embodiments, the susceptor may include a susceptor layer provided on a support. In embodiments having a first susceptor and a second susceptor, each of the first susceptor and the second susceptor may be formed from a support and a susceptor layer. When the susceptor is disposed in a varying magnetic field, eddy currents are induced proximate to the susceptor surface, resulting in an effect called the skin effect. Thus, the susceptor can be formed from a relatively thin layer of susceptor material while ensuring that the susceptor is effectively heated in the presence of a varying magnetic field. Fabricating the susceptor from a support and a relatively thin susceptor layer can facilitate the manufacture of aerosol-generating articles that are simple, inexpensive, and robust.

[0070] The support may be formed from a material that is not susceptible to the effects of inductive heating. Advantageously, this can reduce the heating of the surface of the susceptor that is not in contact with the aerosol-forming substrate, where the surface of the support forms the surface of the susceptor that is not in contact with the aerosol-forming substrate.

[0071] The support may include an electrically insulating material. As used herein, "electrically insulating" refers to a material having an electrical resistivity of at least 1 x 10 4 ohm meters (Ω·m) at 20 degrees Celsius.

[0072] The support may include thermal insulation. As used herein, the term "thermally insulating material" is used to describe a material having a bulk thermal conductivity of about 40 milliwatts per meter kelvin (W / (m·K)) or less at 23 degrees Celsius and a relative humidity of 50 percent as measured using the modified transient plane source (MTPS) method.

[0073] Forming the support from a thermally insulating material can provide a thermal insulation barrier between the susceptor layer and other components of the inductive heating arrangement, such as an inductor coil surrounding the inductive heater. Advantageously, this can reduce the heat transfer between the susceptor and other components of the inductive heating system.

[0074] When the support is a tubular support, the susceptor layer may be provided on the inner surface of the tubular support. By providing the susceptor layer on the inner surface of the support, the susceptor layer can be positioned adjacent to the aerosol-forming substrate within the cavity of the induction heating element, and the heat transfer between the susceptor layer and the aerosol-forming substrate can be improved.

[0075] In some preferred embodiments having a first susceptor and a second susceptor, the first susceptor comprises a tubular support formed from a thermally insulating material and a susceptor layer on an inner surface of the tubular support, hi some preferred embodiments, the second susceptor comprises a tubular support formed from a thermally insulating material and a susceptor layer on an inner surface of the tubular support.

[0076] The susceptor may include a protective outer layer, such as a protective ceramic layer or a protective glass layer. The protective outer layer may improve the durability of the susceptor and facilitate cleaning of the susceptor. The protective outer layer may substantially surround the susceptor. The susceptor may include a protective coating formed from glass, ceramic, or an inert metal.

[0077] The induction heating element may include a separator between the first portion of the induction heating element and the second portion of the induction heating element.

[0078] The separator may be of any suitable size for insulating a first portion of the induction heating element from a second portion of the induction heating element.

[0079] The induction heating element may include an intermediate element disposed between the first portion of the induction heating element and the second portion of the induction heating element. The intermediate element may be disposed within a separation between the first portion of the induction heating element and the second portion of the induction heating element. The intermediate element may extend between the first portion of the induction heating element and the second portion of the induction heating element. The intermediate element may contact an end of the first portion of the induction heating element. The intermediate element may contact an end of the second portion of the induction heating element. The intermediate element may be secured to an end of the first portion of the induction heating element. The intermediate element may be secured to an end of the second portion of the induction heating element. The intermediate element may connect the second portion of the induction heating element to the first portion of the induction heating element. When the intermediate element connects the second portion of the induction heating element to the first portion of the induction heating element, the intermediate element may provide structural support to the induction heating element. Advantageously, the intermediate element may allow the induction heating element to be provided as a single, unitary element that may be easy to remove and replace from an induction heating arrangement.

[0080] The intermediate element may have any suitable configuration. The intermediate element may have any suitable cross-section. For example, the intermediate element may have a circular, elliptical, square, rectangular, triangular, or other polygonal cross-section. The intermediate element may be tubular. A tubular intermediate element includes an annular body that defines an interior cavity. The intermediate element may be configured to allow gas to permeate from the exterior of the intermediate element into the interior cavity. The intermediate element cavity may be configured to receive a portion of the aerosol-generating article. The intermediate element cavity may be an open cavity. The intermediate element cavity may be open at one end. The intermediate element cavity may be open at both ends.

[0081] In some preferred embodiments, the first portion of the induction heating element and the second portion of the induction heating element are tubular susceptors and the intermediate element is a tubular intermediate element. In these embodiments, the tubular first susceptor, the tubular second susceptor, and the tubular intermediate element may be substantially aligned. The tubular first susceptor, the tubular intermediate element, and the tubular second susceptor may be disposed end-to-end in the form of a tubular rod. The internal cavities of the tubular first susceptor, the tubular intermediate element, and the tubular second susceptor may be substantially aligned. The internal cavities of the tubular first susceptor, the tubular intermediate element, and the tubular second susceptor may define an induction heating element cavity.

[0082] The intermediate element may be formed from any suitable material.

[0083] In a preferred embodiment, the intermediate element is formed from a different material than the first portion of the induction heating element and the second portion of the induction heating element.

[0084] The intermediate element may include a thermally insulating material for insulating the first portion of the induction heating element from the second portion of the induction heating element. The intermediate element may include a material having a bulk thermal conductivity of about 100 milliwatts per meter·Kelvin (mW / (mK)) or less at 23 degrees Celsius and a relative humidity of 50 percent measured using a modified transient planar heat source (MTPS) method. By providing an intermediate element formed from a thermally insulating material in the separation between the first portion of the induction heating element and the second portion of the induction heating element, heat transfer between the first portion of the induction heating element and the second portion of the induction heating element may be further reduced. Advantageously, this may improve the ability of the induction heating element to selectively heat separate portions of the aerosol-forming substrate. This may also allow for a reduction in the size of the separation between the first portion of the induction heating element and the second portion of the induction heating element, which in turn may allow for a reduction in the size of the induction heating element.

[0085] The intermediate element may include an electrically insulating material for electrically insulating the first portion of the induction heating element from the second portion of the induction heating element. 4It may include materials that have an electrical resistance in ohm meters (Ωm).

[0086] The intermediate element may include at least one of a thermal insulating material for insulating the first portion of the induction heating element from the second portion of the induction heating element, and an electrically insulating material for electrically insulating the first portion of the induction heating element from the second portion of the induction heating element. In some preferred embodiments, the intermediate element includes a thermal insulating material for insulating the first portion of the induction heating element from the second portion of the induction heating element, and an electrically insulating material for electrically insulating the first portion of the induction heating element from the second portion of the induction heating element.

[0087] Particularly suitable materials for the intermediate element include polymeric materials such as polyetheretherketone (PEEK), liquid crystal polymers such as Kevlar®, certain cements, glass, and ceramic materials such as zirconium dioxide (ZrO2), silicon nitride (Si3N4), and aluminum oxide (Al2O3).

[0088] The intermediate element may be gas permeable. In other words, the intermediate element is configured to allow gas to permeate through the intermediate element. Typically, the intermediate element is configured to allow gas to permeate from one side of the intermediate element to the other side of the intermediate element. The intermediate element may include an exterior and an interior opposite the exterior. The intermediate element may be configured to allow gas to permeate from the exterior to the interior.

[0089] In some embodiments, the intermediate element includes an air passage configured to allow the passage of air through the intermediate element. In these embodiments, the intermediate element may not be required to be formed from a gas permeable material. Thus, in some embodiments, the intermediate element is formed from a material that is not permeable to gas and includes an air passage configured to allow the passage of air through the intermediate element. The intermediate element may include multiple air passages. The intermediate element may include any suitable number of air passages, for example, two, three, four, five, or six air passages. When the intermediate element includes multiple air passages, the air passages may be regularly spaced on the intermediate element.

[0090] If the intermediate element is a tubular intermediate element defining an internal cavity, the intermediate element may include an air passage configured to allow air to flow from an outer surface of the intermediate element into the internal cavity. The intermediate element may include an air passage extending from the outer surface to the inner surface. If the tubular intermediate element includes multiple air passages, the air passages may be regularly spaced around the circumference of the tubular intermediate element.

[0091] The induction heating element may be included in an induction heating arrangement.

[0092] The induction heating arrangement further comprises an inductor coil.Preferably, the induction heating arrangement comprises a first inductor coil and a second inductor coil.

[0093] The first inductor coil is configured such that a varying current supplied to the first inductor coil generates a varying magnetic field. The first inductor coil is disposed relative to the induction heating element such that a varying current supplied to the first inductor coil generates a varying magnetic field that heats a first portion of the induction heating element.

[0094] The second inductor coil is configured such that a varying current supplied to the second inductor coil generates a varying magnetic field. The second inductor coil is disposed relative to the induction heating element such that a varying current supplied to the second inductor coil generates a varying magnetic field that heats a second portion of the induction heating element.

[0095] The inductor coil may have any suitable form. For example, the inductor coil may be a flat inductor coil. The flat inductor coil may be helically wound in a substantially plane. The inductor coil is preferably a tubular inductor coil defining an internal cavity. Typically, the tubular inductor coil is helically wound about an axis. The inductor coil may be elongated. Particularly preferably, the inductor coil may be an elongated tubular inductor coil. The inductor coil may have any suitable cross-section. For example, the inductor coil may have a circular, elliptical, square, rectangular, triangular, or other polygonal cross-section.

[0096] The inductor coil may be formed from any suitable material. The inductor coil is formed from an electrically conductive material. Preferably, the inductor coil is formed from a metal or metal alloy.

[0097] When the inductor coil is a tubular inductor coil, a portion of the induction heating element is preferably disposed within the internal cavity of the inductor coil. Particularly preferably, the first inductor coil is a tubular inductor coil, and at least a portion of the first portion of the induction heating element is disposed within the internal cavity of the first inductor coil. The length of the tubular first inductor coil may be substantially similar to the length of the first portion of the induction heating element. Particularly preferably, the second inductor coil is a tubular inductor coil, and at least a portion of the second portion of the induction heating element is disposed within the internal cavity of the second inductor coil. The length of the tubular second inductor coil may be substantially similar to the length of the second portion of the induction heating element.

[0098] In some embodiments, the second inductor coil is substantially identical to the first inductor coil. In other words, the first and second inductor coils have the same shape, size, and number of turns. Particularly preferred, in embodiments where the second portion of the induction heating element is substantially identical to the first portion of the induction heating element, the second inductor coil is substantially identical to the first inductor coil.

[0099] In some embodiments, the second inductor coil is different from the first inductor coil. For example, the second inductor coil may have a different length, number of turns, or cross-section than the first inductor coil. In particularly preferred embodiments, the second inductor coil is different from the first inductor coil in those embodiments in which the second portion of the induction heating element is different from the first portion of the induction heating element.

[0100] The first and second inductor coils may be arranged in any suitable arrangement. Particularly preferably, the first and second inductor coils are coaxially aligned along the axis. In the case where the first and second inductor coils are elongated tubular inductor coils, the first and second inductor coils may be coaxially aligned along the longitudinal axis such that the internal cavities of the coils are aligned along the longitudinal axis.

[0101] In some embodiments, the first inductor coil and the second inductor coil are wound in the same direction. In some embodiments, the second inductor coil is wound in a different direction than the first inductor coil.

[0102] The induction heating arrangement may include any suitable number of inductor coils. The induction heating element includes a plurality of inductor coils. The induction heating arrangement includes at least two inductor coils. Preferably, the number of inductor coils of the induction heating arrangement is the same as the number of susceptors of the induction heating element. The number of inductor coils of the induction heating arrangement may be different from the number of susceptors of the induction heating element. If the number of inductor coils is the same as the number of susceptors, preferably, each inductor coil is disposed around a susceptor. Particularly preferably, each inductor coil extends substantially the length of the susceptor around which it is disposed.

[0103] The induction heating element may include a magnetic flux concentrator disposed about an inductor coil of the induction heating arrangement, the magnetic flux concentrator configured to deflect a varying magnetic field generated by the inductor coil toward the induction heating element.

[0104] Advantageously, by deflecting the magnetic field toward the induction heating element, the magnetic flux concentrator can focus the magnetic field at the induction heating element. This can increase the efficiency of the induction heating arrangement compared to embodiments in which a magnetic flux concentrator is not provided. As used herein, the phrase "concentrating the magnetic field" means deflecting the magnetic field such that the magnetic energy density of the magnetic field is increased where the magnetic field "focuses."

[0105] As used herein, the term "magnetic flux concentrator" refers to a component having a high relative permeability that acts to concentrate and guide the magnetic field or lines of force generated by an inductor coil. As used herein, the term "relative permeability" refers to the ratio of the permeability of a material or medium, such as a magnetic flux concentrator, to the permeability of free space, "μ 0 " where μ 0 is 4π×10 -7 Newton / square ampere (NA -2 ).

[0106] As used herein, the term "high relative permeability" refers to a relative permeability of at least 5 at 25 degrees Celsius, e.g., at least 10, at least 20, at least 30, at least 40, at least 50, at least 60, at least 80, or at least 100 degrees Celsius. These exemplary values ​​preferably refer to relative permeability values ​​for frequencies between 6 and 8 megahertz (MHz) and a temperature of 25 degrees Celsius.

[0107] The magnetic flux concentrator may be formed from any suitable material or combination of materials. Preferably, the magnetic flux concentrator comprises a ferromagnetic material (such as a ferrite material), a ferrite powder held in a binder, or any other suitable material including a ferrite material (such as ferritic iron, ferromagnetic steel, or stainless steel).

[0108] In some embodiments, the induction heating arrangement includes a magnetic flux concentrator disposed about the first inductor coil and the second inductor coil, the magnetic flux concentrator being configured to deflect a changing magnetic field generated by the first inductor coil toward a first portion of the induction heating element and to deflect a changing magnetic field generated by the second inductor coil toward a second portion of the induction heating element.

[0109] In some of these embodiments, a portion of the magnetic flux concentrator extends into an intermediate element between the first portion of the induction heating element and the second portion of the induction heating element. By extending a portion of the magnetic flux concentrator into an intermediate element between the first portion of the induction heating element and the second portion of the induction heating element, the magnetic field generated by the first inductor coil and the magnetic field generated by the second inductor coil may be further distorted. This further distortion may cause the magnetic field generated by the first inductor coil to be further concentrated toward the first portion of the induction heating element and the magnetic field generated by the second inductor coil to be further concentrated toward the second portion of the induction heating element. This may further improve the efficiency of the induction heating arrangement.

[0110] In some embodiments, the induction heating arrangement includes multiple magnetic flux concentrators. In some preferred embodiments, an individual magnetic flux concentrator is disposed around each inductor coil. Providing each inductor coil with its own dedicated magnetic flux concentrator may allow the magnetic flux concentrators to be optimally configured to optimally distort the magnetic field generated by the inductor coil. Such an arrangement may also allow the induction heating arrangement to be formed from modular induction heating units. Each induction heating unit may include an inductor coil and a magnetic flux concentrator. Providing modular induction heating units may facilitate standardized manufacturing of the induction heating arrangement and allow removal and replacement of individual units.

[0111] In some preferred embodiments, the induction heating arrangement includes a first magnetic flux concentrator disposed about the first inductor coil, the first magnetic flux concentrator configured to deflect a changing magnetic field generated by the first inductor coil toward a first portion of the induction heating element, and a second magnetic flux concentrator disposed about the second inductor coil, the second magnetic flux concentrator configured to deflect a changing magnetic field generated by the second inductor coil toward a second portion of the induction heating element.

[0112] In these preferred embodiments, a portion of the first magnetic flux concentrator may extend into an intermediate element between the first portion of the induction heating element and the second portion of the induction heating element. In these preferred embodiments, a portion of the second magnetic flux concentrator may extend into an intermediate element between the first portion of the induction heating element and the second portion of the induction heating element. Extending a portion of the magnetic flux concentrator into the intermediate element between the susceptors may enable the magnetic flux concentrator to further distort the magnetic field generated by the inductor coil toward the susceptors.

[0113] The induction heating arrangement may further include an induction heating arrangement housing. The housing may hold the induction heating element, the inductor coil, and the magnetic flux concentrator together. This may help to secure the relative arrangement of the components of the induction heating arrangement and improve the bonding between the components. The induction heating arrangement housing is preferably formed from an electrically insulating material.

[0114] When the induction heating arrangement includes individual induction heating units including an inductor coil and a magnetic flux concentrator, each induction heating unit may include an induction heating unit housing that may maintain the components of the induction heating unit together and improve bonding between the components. The induction heating unit housing is preferably formed from an electrically insulating material.

[0115] The induction heating arrangement may be included in the aerosol generating device.

[0116] The aerosol generating device may include a power source. The power source may be any suitable type of power source. The power source may be a DC power source. In some preferred embodiments, the power source is a battery, such as a lithium ion battery. The power source may be another form of charge storage device, such as a capacitor. The power source may require recharging. The power source may have a capacity that allows for the storage of sufficient energy for one or more uses of the device. For example, the power source may have a capacity sufficient to allow for continuous generation of aerosol for about 6 minutes, or a multiple of 6 minutes, corresponding to the typical time it takes to smoke one conventional cigarette. In another example, the power source may have a capacity sufficient to allow for a given number of uses of the device, or for discontinuous activation. In one embodiment, the power source is a DC power source having a DC supply voltage in the range of about 2.5 volts to about 4.5 volts, and a DC supply current in the range of about 1 amp to about 10 amps (corresponding to a DC power source in the range of about 2.5 watts to about 45 watts).

[0117] The aerosol generating device may include a controller connected to the induction heating arrangement and the power source. Specifically, the aerosol generating device may include a first inductor coil and a second inductor coil, and a controller connected to the power source. The controller is configured to control the supply of power from the power source to the induction heating arrangement. The controller may include a microprocessor, which may be a programmable microprocessor, a microcontroller, or an application specific integrated circuit chip (ASIC) or other electronic circuit capable of providing control. The controller may include further electronic components. The controller may be configured to regulate the supply of current to the induction heating arrangement. The current may be supplied to the induction heating arrangement continuously after activation of the aerosol generating device, or may be supplied intermittently (e.g., after every puff).

[0118] The aerosol generating device may advantageously comprise a DC / AC inverter, which may include a class C, class D or class E power amplifier. The DC / AC converter may be arranged between the power supply and the induction heating arrangement.

[0119] The aerosol generating device may further comprise a DC / DC converter between the power supply and the DC / AC converter. The controller may be configured to control the first varying current by controlling the amplitude of the first varying current using the DC / DC converter. The controller may be configured to control the second varying current by controlling the amplitude of the second varying current using the DC / DC converter.

[0120] In some embodiments, the controller may be configured to drive the first varying current in multiple pulses. In these embodiments, the controller may be configured to control the first varying current by pulse width modulation.

[0121] In some embodiments, the controller may be configured to drive the second varying current in multiple pulses. In these embodiments, the controller may be configured to control the second varying current by pulse width modulation.

[0122] The aerosol generating device may include a first switch between the power source and the first inductor coil, and a second switch between the power source and the second inductor coil. The controller may be configured to turn the first switch on and off at a first switching rate to drive a first varying current in the first inductor coil when the second switch remains off. The controller may be configured to turn the second switch on and off at a second switching rate to drive a second varying current in the second inductor coil when the first switch remains off.

[0123] The controller may be configured to supply a varying current to the induction heating arrangement having any suitable frequency. The controller may be configured to supply a varying current to the induction heating arrangement having a frequency of about 5 kilohertz to about 30 megahertz. In some preferred embodiments, the controller is configured to supply a varying current to the induction heating arrangement of about 5 kilohertz to about 500 kilohertz. In some embodiments, the controller is configured to supply a high frequency varying current to the induction heating arrangement. As used herein, the term "high frequency varying current" refers to a varying current having a frequency of about 500 kilohertz to about 30 megahertz. The high frequency varying current may have a frequency of about 1 megahertz to about 30 megahertz, such as about 1 megahertz to about 10 megahertz, or such as about 5 megahertz to about 8 megahertz.

[0124] The aerosol generating device may comprise a device housing. The device housing may be elongated. The device housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics, or composites containing one or more of these materials, or thermoplastics suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), and polyethylene. Preferably, the material is light and not brittle.

[0125] The device housing may define a device cavity for receiving the aerosol-forming substrate. The device cavity may be configured to receive at least a portion of the aerosol-generating article. The device cavity may have any suitable shape and size. The device cavity may be substantially cylindrical. The device cavity may have a substantially circular cross-section.

[0126] The induction heating element may be disposed within the device cavity. The induction heating element may be disposed around the device cavity. If the induction heating element is a tubular induction heating element, the induction heating element may surround the device cavity. The inner surface of the induction heating element may form the inner surface of the device cavity.

[0127] The first inductor coil and the second inductor coil may be disposed within the device cavity. The first inductor coil and the second inductor coil may be disposed around the device cavity. The first inductor coil and the second inductor coil may surround the device cavity. An inner surface of the first inductor coil and the second inductor coil may form an inner surface of the device cavity.

[0128] The device may have a proximal end and a distal end opposite the proximal end. The device cavity is preferably disposed at the proximal end of the device.

[0129] The device cavity may have a proximal end and a distal end opposite the proximal end. The proximal end of the device cavity may be substantially open for receiving an aerosol-generating article.

[0130] In some embodiments, the aerosol generating device further comprises a movable cover over the proximal end of the device cavity to prevent insertion of an aerosol generating article into the device cavity.

[0131] In some preferred embodiments, the first inductor coil is disposed toward a proximal end of the device cavity and the second inductor coil is disposed toward a distal end of the device cavity. In these preferred embodiments, the controller may be configured to initiate heating of the aerosol-forming substrate by driving a first varying current in the first inductor coil and then driving a second varying current in the second inductor coil. Such action heats a proximal portion of the device cavity before heating a distal portion of the device cavity.

[0132] The device housing may include an air inlet. The air inlet may be configured to allow ambient air to enter the device housing. The device housing may include any suitable number of air inlets. The device housing may include multiple air inlets.

[0133] The device housing may include an air outlet. The air outlet may be configured to allow air to enter the device cavity from within the device housing. The device housing may include any suitable number of air outlets. The device housing may include multiple air outlets.

[0134] If the intermediate element of the induction heating element is gas permeable, the aerosol generating device may define an airflow path extending from the air inlet to the intermediate element of the induction heating element. Such an airflow path may allow air to be drawn from the air inlet through the aerosol generating device, through the intermediate element, and into the device cavity.

[0135] In some embodiments, the device cavity includes a proximal end and a distal end opposite the proximal end. In these embodiments, the device cavity may be open at the proximal end for receiving an aerosol-generating article. In these embodiments, the device cavity may be substantially closed at the distal end. The device housing may include an air outlet at the distal end of the device cavity. The aerosol-generating device may further comprise an annular seal towards the proximal end of the device cavity. The annular seal may extend into the device cavity. The annular seal may provide a substantially airtight seal between the device housing and the outer surface of the aerosol-generating article received within the device cavity. Thereby, the volume of air drawn into the device cavity during use may be reduced through any gap present between the outer surface of the aerosol-generating article and the inner surface of the device cavity. This may increase the volume of air drawn into the aerosol-generating article through the permeable intermediate element.

[0136] In some embodiments, the device housing includes a mouthpiece. The mouthpiece may include at least one air inlet and at least one air outlet. The mouthpiece may include two or more air inlets. One or more of the air inlets may reduce the temperature of the aerosol and may also reduce the concentration of the aerosol before the aerosol is delivered to the user.

[0137] In some embodiments, the mouthpiece is provided as part of the aerosol-generating article. As used herein, the term "mouthpiece" refers to a part of the aerosol-generating system that is placed in the user's mouth to directly inhale the aerosol generated by the aerosol-generating system from the aerosol-generating article received by the aerosol-generating device.

[0138] In some embodiments, the controller may be configured to monitor a current supplied to the induction heating arrangement. The controller may be configured to determine a temperature of the induction heating element based on the monitored current. The controller may be configured to monitor a first varying current and determine a temperature of a first portion of the induction heating element based on the monitored first varying current. The controller may be configured to monitor a second varying current and determine a temperature of a second portion of the induction heating element based on the monitored second varying current.

[0139] The aerosol generating device may include a temperature sensor. The temperature sensor may be arranged to sense a temperature of the induction heating element. The controller may be configured to control the first varying current based on the temperature of the induction heating element sensed by the temperature sensor. The controller may be configured to control the second varying current based on the temperature of the induction heating element sensed by the temperature sensor.

[0140] The temperature sensor may be any suitable type of temperature sensor, for example, the temperature sensor may be a thermocouple, a negative temperature coefficient resistance temperature sensor, or a positive temperature coefficient resistance temperature sensor.

[0141] In some preferred embodiments, the aerosol generating device may include a first temperature sensor disposed to sense a temperature of the first portion of the induction heating element, and in these embodiments, the controller may be configured to control the first varying current based on the temperature of the first portion of the induction heating element sensed by the first temperature sensor.

[0142] In some preferred embodiments, the aerosol generating device may include a second temperature sensor disposed to sense a temperature of the second portion of the induction heating element, and in these embodiments, the controller may be configured to control the second varying current based on the temperature of the second portion of the induction heating element sensed by the second temperature sensor.

[0143] The aerosol generating device may include a user interface for activating the device, for example a button to initiate heating of the aerosol generating article.

[0144] The aerosol generating device may include a display that indicates the status of the device or the aerosol-forming substrate.

[0145] The aerosol-generating device may comprise a detector for detecting the presence of the aerosol-forming substrate. If the aerosol-generating device comprises a device cavity for receiving an aerosol-forming substrate, the aerosol-generating device may comprise a detector for detecting the presence of the aerosol-forming substrate in the device cavity. If the aerosol-generating device is configured to receive at least a portion of an aerosol-generating article, the aerosol-generating device may comprise an aerosol-generating article detector configured to detect the presence of the aerosol-generating article in the device cavity.

[0146] When the aerosol-forming substrate detector detects the presence of an aerosol-forming substrate, the controller may be configured to initiate heating by driving a first varying current in the first inductor coil.

[0147] When the aerosol-generating article detector detects the presence of an aerosol-generating article in the device cavity, the controller may be configured to initiate heating by driving a first varying current in the first inductor coil.

[0148] The aerosol-forming substrate detector and the aerosol-generating article detector may include any suitable type of detector, for example, the detector may be an optical detector, an acoustic detector, a capacitive detector, or an inductive detector.

[0149] In some embodiments, the aerosol-generating article comprises an inductive heating element. In these embodiments, the aerosol-generating device may comprise an aerosol-generating article detector including an inductor. In these embodiments, the aerosol-generating article detector may be configured to detect a change in inductance when the aerosol-generating article is received within the device cavity to detect the presence of the aerosol-generating article within the device cavity.

[0150] The aerosol generating device may include a puff detector configured to detect when a user puffs on the aerosol generating system. As used herein, the term "puff" is used to refer to a user puffing on the aerosol generating system to receive an aerosol.

[0151] The aerosol generating device is preferably portable. The aerosol generating device may have a size comparable to a conventional cigar or cigarette. The aerosol generating device may have a total length of about 30 mm to about 150 mm. The aerosol generating device may have an outer diameter of about 5 mm to about 30 mm.

[0152] The aerosol generating device may form part of an aerosol generating system.

[0153] The aerosol-generating system may further comprise an aerosol-generating article. The aerosol-generating article may comprise a first aerosol-forming substrate and a second aerosol-forming substrate. When the aerosol-generating article is received in the device cavity, at least a portion of the first aerosol-forming substrate may be received in a first portion of the device cavity and at least a portion of the second aerosol-forming substrate may be received in a second portion of the device cavity.

[0154] An induction heating element forming part of the induction heating arrangement of the aerosol generating device is configured to heat the aerosol-forming substrate.

[0155] The aerosol-forming substrate may comprise nicotine. The nicotine-containing aerosol-forming substrate may be a nicotine salt matrix.

[0156] The aerosol-forming substrate may be a liquid. The aerosol-forming substrate may comprise a solid component and a liquid component. The aerosol-forming substrate is preferably a solid.

[0157] The aerosol-forming substrate may comprise a plant-derived material. The aerosol-forming substrate may comprise tobacco. The aerosol-forming substrate may comprise a tobacco-containing material comprising volatile tobacco flavour compounds which are released from the aerosol-forming substrate upon heating. The aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may comprise a homogenised plant-derived material. The aerosol-forming substrate may comprise a homogenised tobacco material. The homogenised tobacco material may be formed by agglomerating particulate tobacco. In a particularly preferred embodiment, the aerosol-forming substrate comprises an assembly of crimped sheets of homogenised tobacco material. As used herein, the term "crimped sheet" refers to a sheet having a plurality of substantially parallel ridges or corrugations.

[0158] The aerosol-forming substrate may include at least one aerosol former. The aerosol former is any suitable known compound or mixture of compounds that facilitates the formation of a dense, stable aerosol during use and is substantially resistant to thermal decomposition at the operating temperature of the system. Suitable aerosol formers are well known in the art and include, but are not limited to, polyhydric alcohols (such as triethylene glycol, 1,3-butanediol, glycerin, etc.), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, or triacetate, etc.), and aliphatic esters of mono-, di-, or polycarboxylic acids (such as dimethyl dodecanedioate, dimethyl tetradecanedioate, etc.). A preferred aerosol former may include a polyhydric alcohol or mixtures thereof (such as triethylene glycol, 1,3-butanediol, etc.). The aerosol former is preferably glycerin. When present, the homogenized tobacco material may have an aerosol former content of 5 weight percent or more on a dry weight basis (e.g., from about 5 weight percent to about 30 weight percent on a dry weight basis). The aerosol-forming substrate may contain other additives and ingredients, such as flavourants.

[0159] The aerosol-forming substrate may be comprised within an aerosol-generating article. An aerosol generating device comprising an inductive heating arrangement may be configured to receive at least a portion of the aerosol-generating article. The aerosol-generating article may have any suitable form. The aerosol-generating article may be substantially cylindrical in shape. The aerosol-generating article may be substantially elongated. The aerosol-generating article may have a length and a circumference substantially perpendicular to the length.

[0160] The aerosol-forming substrate may be provided as an aerosol-generation segment containing the aerosol-forming substrate. The aerosol-generation segment may comprise a plurality of aerosol-forming substrates. The aerosol-generation segment may comprise a first aerosol-forming substrate and a second aerosol-forming substrate. In some embodiments, the second aerosol-forming substrate is substantially identical to the first aerosol-forming substrate. In some embodiments, the second aerosol-forming substrate is different from the first aerosol-forming substrate.

[0161] When the aerosol-generation segment comprises multiple aerosol-forming substrates, the number of aerosol-forming substrates may be the same as the number of susceptors in the induction heating element, similarly, the number of aerosol-forming substrates may be the same as the number of inductor coils in the induction heating arrangement.

[0162] The aerosol-generation segment may be substantially cylindrical. The aerosol-generation segment may be substantially elongated. The aerosol-generation segment may also have a length and a circumference substantially perpendicular to the length.

[0163] Where the aerosol-generation segment comprises more than one aerosol-forming substrate, the aerosol-forming substrates may be arranged end-to-end along the axis of the aerosol-generation segment, hi some embodiments, the aerosol-generation segment may comprise separations between adjacent aerosol-forming substrates.

[0164] In some preferred embodiments, the aerosol-generating article may have an overall length of about 30 millimeters to about 100 millimeters. In some embodiments, the aerosol-generating article has an overall length of about 45 millimeters. The aerosol-generating article may have an outer diameter of about 5 millimeters to about 12 millimeters. In some embodiments, the aerosol-generating article may have an outer diameter of about 7.2 millimeters.

[0165] The aerosol-generation segment may have a length of about 7 millimeters to about 15 millimeters, in some embodiments, the aerosol-generation segment may have a length of about 10 millimeters or 12 millimeters.

[0166] The aerosol-generation segment preferably has an outer diameter approximately equal to the outer diameter of the aerosol-generating article. The outer diameter of the aerosol-generation segment may be from about 5 millimeters to about 12 millimeters. In one embodiment, the aerosol-generation segment may have an outer diameter of about 7.2 millimeters.

[0167] The aerosol-generating article may include a filter plug. The filter plug may be located at a proximal end of the aerosol-generating article. The filter plug may be a cellulose acetate filter plug. In some embodiments, the filter plug may have a length of about 5 millimeters to about 10 millimeters. In some preferred embodiments, the filter plug may have a length of about 7 millimeters.

[0168] As mentioned above, the aerosol-generating article may comprise at least a portion of an induction heating element. In some embodiments, the aerosol-generating article comprises the entire induction heating element. A first portion of the induction heating element may be arranged to heat a first portion of the aerosol-forming substrate. A first portion of the induction heating element may be embedded within the first portion of the aerosol-forming substrate. A first portion of the induction heating element may substantially surround the first portion of the aerosol-forming substrate. A second portion of the induction heating element may be arranged to heat a second portion of the aerosol-forming substrate. A second portion of the induction heating element may be embedded within the second portion of the aerosol-forming substrate. A second portion of the induction heating element may substantially surround the second portion of the aerosol-forming substrate.

[0169] The aerosol-generating article may include an outer wrapper. The outer wrapper may be formed from paper. The outer wrapper may be gas permeable at the aerosol-generating segment. In particular, in embodiments with multiple aerosol-forming substrates, the outer wrapper may include perforations or other air inlets at the interface between adjacent aerosol-forming substrates. If a separation is provided between adjacent aerosol-forming substrates, the outer wrapper may include perforations or other air inlets at the separation. This may allow the aerosol-forming substrate to be provided directly with air that has not been drawn through another aerosol-forming substrate. This may increase the amount of air received by each aerosol-forming substrate. This may improve the properties of the aerosol generated from the aerosol-forming substrate.

[0170] The aerosol-generating article may also include a separation between the aerosol-forming substrate and the filter plug, which may be about 18 millimeters, but may range from about 5 millimeters to about 25 meters.

[0171] It should also be understood that particular combinations of the various features described above may be implemented, provided or used independently.

[0172] Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0173] [Figure 1] FIG. 1 shows a schematic diagram of an induction heating element according to one embodiment of the present disclosure disposed between a pair of inductor coils. [Diagram 2] FIG. 2 shows a schematic diagram of an induction heating element according to one embodiment of the present disclosure disposed between a pair of inductor coils. [Diagram 3] FIG. 3 illustrates an exploded perspective view of an induction heating element according to one embodiment of the present disclosure. [Figure 4] FIG. 4 shows a perspective view of the induction heating element of FIG. [Diagram 5]FIG. 5 shows a cross-sectional view of an aerosol generation system according to one embodiment of the present invention, comprising an aerosol-generating article and an aerosol generating device having an inductive heating arrangement. [Figure 6] FIG. 6 is a cross-sectional view of the proximal end of the aerosol generating device of FIG. [Figure 7] FIG. 7 shows a cross-sectional view of the aerosol generating system of FIG. 5, in which the aerosol-generating article is received within the aerosol generating device. [Figure 8] FIG. 8 shows a schematic diagram of an induction heating element according to one embodiment of the present disclosure disposed between a pair of inductor coils. [Figure 9] FIG. 9 shows a graph of the temperature over time of the induction heating element of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0174] FIG. 1 shows a schematic diagram of an induction heating element 10 according to one embodiment of the present disclosure. The induction heating element 10 is an elongated tubular element having a circular cross-section. The induction heating element 10 includes a first susceptor 12, a second susceptor 14, and a separation 15 between the first susceptor 12 and the second susceptor 14. The first susceptor 12 and the second susceptor 14 are each an elongated tubular element having a circular cross-section. The first susceptor 12 and the second susceptor 14 are coaxially aligned end-to-end along a longitudinal axis AA.

[0175] The induction heating element 10 includes a cylindrical cavity 20 that is open at both ends and defined by the inner surfaces of a first susceptor 12 and a second susceptor 14. The cavity 20 is configured to receive a portion of a cylindrical aerosol-generating article (not shown) comprising an aerosol-forming substrate such that the outer surface of the aerosol-generating article can be heated by the first susceptor and the second susceptor, thereby heating the aerosol-forming substrate.

[0176] The cavity 20 includes three portions: a first portion 22 at a first end defined by the inner surface of the tubular first susceptor 12, a second portion 24 at a second end defined by the inner surface of the tubular second susceptor 14 opposite the first end, and an intermediate portion 26 bounded by a separation 15 between the first susceptor 12 and the second susceptor 14. The first susceptor 12 is arranged to heat a first portion of an aerosol-generating article received in the first portion 22 of the cavity 20, and the second susceptor 14 is arranged to heat a second portion of an aerosol-generating article received in the second portion 24 of the cavity 20.

[0177] The first inductor coil 32 is disposed about and extends substantially the length of the first susceptor 12. Thus, the first susceptor 12 is surrounded by the first inductor coil 32 substantially along its length. When a varying current is supplied to the first inductor coil 32, the first inductor coil 32 generates a varying magnetic field concentrated in the first portion 22 of the cavity 20. Such a varying magnetic field generated by the first inductor coil 32 induces eddy currents in the first susceptor 12, causing the first susceptor 12 to heat up.

[0178] The second inductor coil 34 is disposed about and extends substantially the length of the second susceptor 14. Thus, the second susceptor 14 is surrounded by the second inductor coil 34 substantially along its length. When a varying current is supplied to the second inductor coil 34, the second inductor coil 34 generates a varying magnetic field concentrated in the second portion 24 of the cavity 20. Such a varying magnetic field generated by the second inductor coil 34 induces eddy currents in the second susceptor 14, causing the second susceptor 14 to heat up.

[0179] The separator 15 between the first susceptor 12 and the second susceptor 14 provides a space between the first susceptor 12 and the second susceptor 14 that is not heated by induction when exposed to the varying magnetic fields generated by either the first inductor coil 32 or the second inductor coil 34. Additionally, the separator 15 insulates the second susceptor 14 from the first susceptor 12 such that the rate of heat transfer between the first susceptor 12 and the second susceptor 14 is reduced as compared to an induction heating element in which the first and second susceptors are disposed adjacent to one another in direct thermal contact. As a result, providing a separation 15 between the first susceptor 12 and the second susceptor 14 allows selective heating of the first portion 22 of the cavity 20 by the first susceptor 12 while minimizing heating of the second portion 24 of the cavity 20, and also allows selective heating of the second portion 24 of the cavity 20 by the second susceptor 14 while minimizing heating of the first portion 22 of the cavity 20.

[0180] The first susceptor 12 and the second susceptor 14 may be heated simultaneously by simultaneously supplying a varying current to the first inductor coil 32 and the second inductor coil 34. Alternatively, the first susceptor 12 and the second susceptor 14 may be heated independently or alternately by supplying a varying current to the first inductor coil 32 without supplying a current to the second inductor coil 34, and then supplying a varying current to the second inductor coil 34 without supplying a current to the first inductor coil 32. It is also contemplated that a varying current may be supplied to the first inductor coil 32 and the second inductor coil 34 in sequence.

[0181] Figure 2 shows a schematic diagram of an induction heating element according to another embodiment of the present disclosure. The induction heating element shown in Figure 2 is substantially identical to the induction heating element shown in Figure 1, and like reference numbers have been used to denote like features.

[0182] The induction heating element 10 of FIG. 2 is an elongated tubular element having a circular cross section. The induction heating element 10 includes a first susceptor 12 and a second susceptor 14. The difference between the induction heating element 10 of FIG. 1 and the induction heating element 10 of FIG. 2 is that the induction heating element 10 of FIG. 2 includes an intermediate element 16 disposed between the first susceptor 12 and the second susceptor 14. In the embodiment of FIG. 2, the separation between the first susceptor 12 and the second susceptor 14 still exists, but the separation is filled by the intermediate element 16. In this embodiment, the intermediate element 16 is fixed to an end of the first susceptor 12 and is also fixed to an end of the second susceptor 14. By fixing the intermediate element 16 to an end of the first susceptor 12 and fixing the intermediate element 16 to an end of the second susceptor 14, the first susceptor 12 is indirectly connected to the second susceptor 14. Advantageously, indirectly fastening the first susceptor 12 to the second susceptor 14 allows the induction heating element to form a unitary structure.

[0183] The intermediate element 16 includes a thermally insulating material. The thermally insulating material is also electrically insulating. In this embodiment, the intermediate element 16 is formed from a polymeric material such as PEEK. Thus, the intermediate element 16 between the first susceptor 12 and the second susceptor 14 provides a space between the first susceptor 12 and the second susceptor 14 that is not heated by induction when exposed to a fluctuating magnetic field generated by either the first inductor coil 32 or the second inductor coil 34. Furthermore, the intermediate element 16 insulates the second susceptor 14 from the first susceptor 12 such that the rate of heat transfer between the first susceptor 12 and the second susceptor 14 is reduced compared to an induction heating element in which the first susceptor 12 and the second susceptor 14 are disposed adjacent to each other in direct thermal contact. The intermediate element 16 may also further reduce the rate of heat transfer between the first susceptor 12 and the second susceptor 14 as compared to the separation portion 15 of the induction heating element 10 of Figure 1. As a result, providing the intermediate element 16 between the first susceptor 12 and the second susceptor 14 allows for selective heating of the first portion 22 of the cavity 20 by the first susceptor 12 while minimizing heating of the second portion 24 of the cavity 20, and allows for selective heating of the second portion 24 of the cavity 20 by the second susceptor 14 while minimizing heating of the first portion 22 of the cavity 20.

[0184] 3-7 show schematic diagrams of an aerosol generating system according to one embodiment of the present disclosure. The aerosol generating system comprises an aerosol generating device 100 and an aerosol generating article 200. The aerosol generating device 100 comprises an induction heating arrangement 110 according to the present disclosure. The induction heating arrangement 110 includes an induction heating element 120 according to the present disclosure.

[0185] 3 and 4 show schematic diagrams of the induction heating element 120. The induction heating element 120 includes a first susceptor 122, a second susceptor 124, a third susceptor 126, a first intermediate element 128, and a second intermediate element 130. The first intermediate element 128 is disposed between the first susceptor 122 and the second susceptor 124. The second intermediate element 130 is disposed between the second susceptor 124 and the third susceptor 126.

[0186] In this embodiment, each of the first susceptor 122, second susceptor 124, and third susceptor 126 are identical. Each susceptor 122, 124, 126 is an elongated tubular susceptor defining an internal cavity. Each susceptor, and its corresponding internal cavity, is substantially cylindrical and has a circular cross-section that is constant along the length of the susceptor. The internal cavity of the first susceptor 122 defines a first region 134. The internal cavity of the second susceptor 124 defines a second region 136. The internal cavity of the third susceptor defines a third region 138.

[0187] Similarly, the first intermediate element 128 and the second intermediate element 130 are identical. The intermediate elements 128, 130 are tubular and define an internal cavity. Each intermediate element 128, 130 is substantially cylindrical and has a circular cross-section that is constant along the length of the intermediate element. The outer diameter of the intermediate elements 128, 130 is the same as the outer diameter of the susceptors 122, 124, 126 such that the outer surfaces of the intermediate elements 128, 130 can be aligned flush with the outer surfaces of the susceptors 122, 124, 126. The inner diameter of the intermediate elements 128, 130 is also the same as the inner diameter of the susceptors 122, 124, 126 such that the inner surfaces of the intermediate elements 128, 138 can be aligned flush with the inner surfaces of the susceptors 122, 124, 126.

[0188] The first susceptor 122, the first intermediate element 128, the second susceptor 124, the second intermediate element 130 and the third susceptor 126 are arranged end-to-end and coaxially aligned on an axis BB. In this arrangement, the susceptors 122, 124, 126 and the intermediate elements 128, 130 form a tubular elongated cylindrical structure. This structure forms the induction heating element 120 according to one embodiment of the present disclosure.

[0189] The elongated tubular induction heating element 120 includes an interior cavity 140. The induction heating element cavity 140 is defined by the interior cavities of the susceptors 122, 124, 126 and the interior cavities of the intermediate elements 128, 130. The induction heating element cavity 140 is configured to receive an aerosol-generating segment of the aerosol-generating article 200, as described in more detail below.

[0190] The intermediate elements 128, 130 are formed from an electrically insulating and thermally insulating material. Thus, the susceptors 122, 124, 126 are substantially electrically and thermally insulated from one another. The material of the intermediate elements 128, 130 is also substantially impermeable to gas. In this embodiment, the tubular induction heating element 120 is substantially impermeable to gas from its outer surface to the inner surface that defines the induction heating element cavity 140.

[0191] 5, 6 and 7 show schematic cross-sectional views of an aerosol generating device 100 and an aerosol-generating article 200.

[0192] The aerosol-generating device 100 comprises a substantially cylindrical device housing 102 having a shape and size similar to a conventional cigar. The device housing 102 defines a device cavity 104 at a proximal end. The device cavity 104 is substantially cylindrical, open at the proximal end and substantially closed at a distal end opposite the proximal end. The device cavity 104 is configured to receive an aerosol-generating segment 210 of the aerosol-generating article 200. Thus, the length and diameter of the device cavity 104 are substantially similar to the length and diameter of the aerosol-generating segment 210 of the aerosol-generating article 200.

[0193] The aerosol generation device 100 further comprises a power source 106 in the form of a rechargeable nickel-cadmium battery, a controller 108 in the form of a printed circuit board including a microprocessor, an electrical connector 109, and an inductive heating arrangement 110. The power source 106, the controller 108, and the inductive heating arrangement 110 are all contained within the device housing 102. The inductive heating arrangement 110 of the aerosol generation device 100 is disposed at a proximal end of the device 100 and is generally disposed about the device cavity 104. The electrical connector 109 is disposed at a distal end of the device housing 109 opposite the device cavity 104.

[0194] The controller 108 is configured to control the supply of power from the power source 106 to the induction heating arrangement 110. The controller 108 further includes a DC / AC inverter including a class D power amplifier and is configured to provide a varying current to the induction heating arrangement 110. The controller 108 is also configured to control recharging of the power source 106 from an electrical connector 109. In addition, the controller 108 includes a puff sensor (not shown) configured to sense when a user puffs on an aerosol-generating article received in the device cavity 104.

[0195] The induction heating arrangement 110 includes three induction heating units, including a first induction heating unit 112, a second induction heating unit 114, and a third induction heating unit 116. The first induction heating unit 112, the second induction heating unit 114, and the third induction heating unit 116 are substantially identical.

[0196] The first induction heating unit 112 includes a tubular-cylindrical first inductor coil 150, a tubular-cylindrical first magnetic flux concentrator 152 disposed around the first inductor coil 150, and a tubular-cylindrical first inductor unit housing 154 disposed around the first magnetic flux concentrator 152.

[0197] The second induction heating unit 114 includes a tubular cylindrical second inductor coil 160, a tubular cylindrical second magnetic flux concentrator 162 disposed around the second inductor coil 160, and a tubular cylindrical second inductor unit housing 164 disposed around the second magnetic flux concentrator 162.

[0198] The third induction heating unit 116 includes a tubular cylindrical third inductor coil 170, a tubular cylindrical third magnetic flux concentrator 172 disposed around the third inductor coil 170, and a tubular cylindrical third inductor unit housing 174 disposed around the third magnetic flux concentrator 172.

[0199] Thus, each of the induction heating units 112, 114, 116 forms a substantially tubular unit having a circular cross-section. In each of the induction heating units 112, 114, 116, the magnetic flux concentrator extends across the proximal and distal ends of the inductor coil such that the inductor coil is disposed within the annular cavity of the magnetic flux concentrator. Similarly, each inductor unit housing extends across the proximal and distal ends of the magnetic flux concentrator such that the magnetic flux concentrator and the inductor coil are disposed within the annular cavity of the inductor unit housing. This arrangement enables the magnetic flux concentrator to concentrate the magnetic field generated by the inductor coil within the internal cavity of the inductor coil. Also, this arrangement enables the inductor unit housing to hold the magnetic flux concentrator and the inductor coil within the inductor unit housing.

[0200] The induction heating arrangement 110 further includes an induction heating element 120. The induction heating element 120 is disposed around the inner surface of the device cavity 104. In this embodiment, the device housing 102 defines the inner surface of the device cavity 104. However, in some embodiments, it is contemplated that the inner surface of the device cavity is defined by the inner surface of the induction heating element 120.

[0201] The induction heating units 112, 114, 116 are disposed around the induction heating element 120 such that the induction heating element 120 and the induction heating units 112, 114, 116 are disposed concentrically around the device cavity 104. The first induction heating unit 112 is disposed around the first susceptor 122 at a distal end of the device cavity 104. The second induction heating unit 114 is disposed around the second susceptor 124 at a central portion of the device cavity 104. The third induction heating unit 116 is disposed around the third susceptor 126 at a proximal end of the device cavity 104. In some embodiments, a magnetic flux concentrator may also extend into the middle element of the induction heating element to further deflect the magnetic field generated by the inductor coil towards the susceptor.

[0202] The first inductor coil 150 is connected to the controller 108 and the power source 106, and the controller 108 is configured to supply a varying current to the first inductor coil 150. When the varying current is supplied to the first inductor coil 150, the first inductor coil 150 generates a varying magnetic field, which heats the first susceptor 122 by induction.

[0203] The second inductor coil 160 is connected to the controller 108 and the power supply 106, and the controller 108 is configured to supply a varying current to the second inductor coil 160. When the varying current is supplied to the second inductor coil 160, the second inductor coil 160 generates a varying magnetic field, which heats the second susceptor 124 by induction.

[0204] The first inductor coil 170 is connected to the controller 108 and the power supply 106, and the controller 108 is configured to supply a varying current to the third inductor coil 170. When the varying current is supplied to the third inductor coil 170, the third inductor coil 170 generates a varying magnetic field, which heats the third susceptor 126 by induction.

[0205] The device housing 102 also defines an air inlet 180 proximate the distal end of the device cavity 106. The air inlet 180 is configured to allow ambient air to be drawn into the device housing 102. An airflow path 181 is defined through the device between the air inlet 180 and an air outlet at the distal end of the device cavity 104 to allow air to be drawn from the air inlet 180 into the device cavity 104.

[0206] The aerosol-generating article 200 is generally in the form of a cylindrical rod having a diameter similar to the inner diameter of the device cavity 104. The aerosol-generating article 200 comprises a cylindrical cellulose acetate filter plug 204 and a cylindrical aerosol-generating segment 210 wrapped together with an outer wrapper 220 of cigarette paper.

[0207] A filter plug 204 is disposed at the proximal end of the aerosol-generating article 200 and forms the mouthpiece of the aerosol-generating system against which a user draws to receive the aerosol generated by the system.

[0208] The aerosol-generating segment 210 is disposed at the distal end of the aerosol-generating article 200 and has a length substantially equal to the length of the device cavity 104. The aerosol-generating segment 210 comprises a plurality of aerosol-forming substrates, including a first aerosol-forming substrate 212 at the distal end of the aerosol-generating article 200, a second aerosol-forming substrate 214 adjacent to the first aerosol-forming substrate 212, and a third aerosol-forming substrate 216 adjacent to the second aerosol-forming substrate 216 at the proximal end of the aerosol-generating segment 210. Of course, in some embodiments, two or more of the aerosol-forming substrates may be formed from the same material. However, in this embodiment, each of the aerosol-forming substrates 212, 214, 216 are different. The first aerosol-forming substrate 212 comprises an assembly of crimped sheets of homogenized tobacco material that does not contain added flavorants. The second aerosol-forming substrate 214 comprises an assembly of crimped sheets of homogenized tobacco material containing a flavorant in the form of menthol. The third aerosol-forming substrate may contain a flavorant in the form of menthol and does not contain any other source of tobacco material or nicotine. Each of the aerosol-forming substrates 212, 214, 216 also contains one or more aerosol formers and further components such as water, such that heating the aerosol-forming substrate generates an aerosol having an organic irritant, where desirable.

[0209] The proximal end of the first aerosol-forming substrate 212 is exposed as it is not covered by the outer wrapper 220. In this embodiment, air can be drawn into the aerosol-generation segment 210 at the proximal end of the article 200 through the proximal end of the first aerosol-forming substrate 212.

[0210] In this embodiment, the first aerosol-forming substrate 212, the second aerosol-forming substrate 214, and the third aerosol-forming substrate 216 are arranged in end-to-end contact. However, in other embodiments, it is envisioned that a separation portion may be provided between the first aerosol-forming substrate and the second aerosol-forming substrate, and a separation portion may be provided between the second aerosol-forming substrate and the third aerosol-forming substrate.

[0211] As shown in FIG. 7, when the aerosol-generating segment 210 of the aerosol-generating article 200 is received within the device cavity 104, the length of the first aerosol-forming substrate 212 is such that the first aerosol-forming substrate 212 extends from the distal end of the device cavity 104, through the first region 134 of the first susceptor 122, to the first intermediate member 128. The length of the second aerosol-forming substrate 214 is such that the second aerosol-forming substrate 214 extends from the first intermediate member 128, through the second region 136 of the second susceptor 124, to the second intermediate member 130. The length of the third aerosol-forming substrate 216 is such that the third aerosol-forming substrate 216 extends from the second intermediate member 130 to the proximal end of the device cavity 104.

[0212] In use, when the aerosol-generating article 200 is received within the device cavity 104, the user may draw on the proximal end of the aerosol-generating article 200 to inhale the aerosol generated by the aerosol-generating system. When the user draws on the proximal end of the aerosol-generating article 200, air is drawn into the device housing 102 at the air inlet 180 and into the device cavity 104 along the airflow path 181. The air is drawn into the aerosol-generating article 200 at the proximal end of the first aerosol-forming substrate 212 through the outlet at the distal end of the device cavity 104.

[0213] In this embodiment, the controller 108 of the aerosol generating device 100 is configured to supply power to the inductor coils of the induction heating arrangement 110 in a predetermined sequence. The predetermined sequence includes supplying a varying current to the first inductor coil 150 during a first draw from the user, then supplying a varying current to the second inductor coil 160 during a second draw from the user after the first draw is over, and then supplying a varying current to the third inductor coil 170 during a third draw from the user after the second draw is over. At the fourth draw, the sequence begins again with the first inductor coil 150. This sequence results in heating of the first aerosol-forming substrate 212 in the first puff, heating of the second aerosol-forming substrate 214 in the second puff, and heating of the third aerosol-forming substrate 216 in the third puff. Because the aerosol-forming substrates 212, 214, 216 of the article 100 are all different, this sequence results in a different experience for the user with each puff on the aerosol generating system.

[0214] Of course, the controller 108 may be configured to power the inductor coils in different orders or simultaneously depending on the desired delivery of the aerosol to the user. In some embodiments, the aerosol generating device may be controllable by the user to change the order.

[0215] 8 shows a schematic diagram of an induction heating element 310 according to one embodiment of the present disclosure. The induction heating element 310 is an elongated tubular element having a circular cross-section. The induction heating element 310 includes a single elongated susceptor having a first portion 312 and a second portion 314. The first portion 312 and the second portion 314 are each an elongated tubular element having a circular cross-section. The first portion 312 and the second portion 314 are coaxially aligned end-to-end along a longitudinal axis AA.

[0216] The induction heating element 310 includes a cylindrical cavity 320 that is open at both ends and defined by the inner surfaces of a first portion 312 and a second portion 314. The cavity 320 is configured to receive a portion of a cylindrical aerosol-generating article (not shown) comprising an aerosol-forming substrate such that an outer surface of the aerosol-generating article can be heated by the first and second susceptors, thereby heating the aerosol-forming substrate.

[0217] It will be appreciated that the induction heating element 310 may form part of an aerosol-generating device or may form part of an aerosol-generating article. In embodiments in which the induction heating element 310 forms part of an aerosol-generating device, the cavity 320 is configured to receive a portion of the aerosol-generating article that comprises an aerosol-forming substrate. In embodiments in which the induction heating element 310 forms part of an aerosol-generating article, the induction heating element 310 surrounds the portion of the aerosol-generating article that contains the aerosol-forming substrate. In these embodiments, the induction heating element 310 may take the form of a wrapper around the outer surface of the aerosol-forming substrate.

[0218] The cavity 320 includes two portions, a first portion 322 at a first end defined by an inner surface of the first portion 312 of the induction heating element 310, and a second portion 324 at a second end opposite the first end defined by an inner surface of the second portion 314 of the induction heating element 310. The first portion 312 of the induction heating element 310 is arranged to heat a first portion of an aerosol-generating article received in the first portion 322 of the cavity 320, and the second portion 314 of the induction heating element 310 is arranged to heat a second portion of an aerosol-generating article received in the second portion 324 of the cavity 320.

[0219] The first inductor coil 332 is disposed around the first portion 312 of the induction heating element 310 and extends substantially the length of the first portion 312 of the induction heating element 310. Thus, the first portion 312 of the induction heating element 310 is surrounded by the first inductor coil 332 substantially along its length. When a varying current is supplied to the first inductor coil 332, the first inductor coil 332 generates a varying magnetic field that is concentrated in the first portion 322 of the cavity 320. Such a varying magnetic field generated by the first inductor coil 332 induces eddy currents in the first portion 312 of the induction heating element 310, causing the first portion 312 of the induction heating element 310 to heat up.

[0220] The second inductor coil 334 is disposed around the second portion 314 of the induction heating element 310 and extends substantially the length of the second portion 314 of the induction heating element 310. Thus, the second portion 314 of the induction heating element 310 is surrounded by the second inductor coil 334 of the induction heating element 310 substantially along its length. When a varying current is supplied to the second inductor coil 334, the second inductor coil 334 generates a varying magnetic field that is concentrated in the second portion 324 of the cavity 320. Such a varying magnetic field generated by the second inductor coil 334 induces eddy currents in the second portion 314 of the induction heating element 310, heating the second susceptor 314.

[0221] The first portion 312 of the induction heating element 310 and the second portion 314 of the induction heating element 310 may be heated simultaneously by simultaneously supplying a varying current to the first inductor coil 332 and the second inductor coil 334. Alternatively, the first portion 312 of the induction heating element 310 and the second portion 314 of the induction heating element 310 may be heated independently or alternately by supplying a varying current to the first inductor coil 332 without supplying a current to the second inductor coil 334, and then by supplying a varying current to the second inductor coil 334 without supplying a current to the first inductor coil 332. It is also contemplated that a varying current may be supplied to the first inductor coil 332 and the second inductor coil 334 in sequence.

[0222] Temperature sensors in the form of thermocouples are also provided on the outer surface of the induction heating element 310. A first thermocouple 342 is provided on the outer surface of the first portion 312 of the induction heating element 310 to sense the temperature of the first portion 312 of the induction heating element 310. A second thermocouple 344 is provided on the outer surface of the second portion 314 of the induction heating element 310 to sense the temperature of the second portion 314 of the induction heating element 310.

[0223] 9 shows a graph of temperature 402 as a function of time 404 during one heating cycle of a first portion 312 of the induction heating element 310 using readings from a first thermocouple 342, and of a second portion of the induction heating element 310 using readings from a second thermocouple 344. In FIG. 9, the temperature of the first portion 312 of the induction heating element 310 from the first thermocouple 342 is shown by a solid line 406. In FIG. 9, the temperature of the second portion 314 of the induction heating element 310 from the second thermocouple 344 is shown by a dashed line 408.

[0224] As shown in FIG. 9, when heating is initiated, the first portion 312 of the induction heating element 310 heats up rapidly during a first stage 410 and reaches the operating temperature after a first period 414 of about 60 seconds. The second portion 314 of the induction heating element 310 heats up during the first stage 410, but at a much slower rate than the first portion 312. The temperature of the first portion 312 of the induction heating element 310 is greater than the temperature of the second portion 314 of the induction heating element 310 throughout the first stage 410. The second portion 314 of the induction heating element 310 does not reach the operating temperature during the first stage 410. In this embodiment, the operating temperature refers to the desired temperature at which the most desirable aerosol is emitted from the aerosol-forming substrate.

[0225] 9, after a second period 416 of about 150 seconds from the start of heating, the first phase 410 ends and a second phase 412 begins. In the second phase 412, the first portion 312 of the induction heating element 310 is heated to a lower temperature, but still within about 50 degrees Celsius of the operating temperature. Also in the second phase 412, the second portion 314 of the induction heating element 310 is rapidly heated to the operating temperature, reaching the operating temperature after a third period 418 of about 210 seconds from the start of heating.

[0226] Specifically, FIG. 9 shows a desirable temperature profile of the aerosol generation system. The first portion 312 of the induction heater 310 is arranged to heat the proximal portion of the aerosol forming substrate, and the second portion 314 of the induction heater 310 is arranged to heat the distal portion of the aerosol forming substrate. The proximal portion of the aerosol forming substrate is close to the mouthpiece end of the aerosol generating article comprising the aerosol forming substrate. Such a temperature profile across the aerosol forming substrate enables the generation of an aerosol having desired properties throughout an extended aerosol generation period. By heating the proximal portion of the aerosol forming substrate before heating the distal portion of the substrate, optimal delivery of the generated aerosol to the user is facilitated. Specifically, this is because the hot aerosol from the heated proximal portion of the aerosol forming substrate does not interact with the unheated distal portion of the aerosol forming substrate during the first stage, and thus it is considered that the hot aerosol from the proximal portion does not release volatile compounds from the distal portion.

[0227] Such a temperature profile can be achieved by driving the varying currents in the first induction coil 312 and the second induction coil 314 in various ways. For example, in the first stage, a first varying current can be driven in the first induction coil 312 with a first duty cycle, and a second varying current can be driven in the second induction coil 314. The duty cycle of the second varying current is less than the duty cycle of the first varying current such that the current driven in the first induction coil 312 during the first stage is greater than the current driven in the second induction coil 314. Of course, in some embodiments, during the first stage 410, no varying current is supplied to the second induction coil 314. In the second stage, the opposite may be true, i.e., the duty cycle of the first varying current may be less than the duty cycle of the second varying current.

[0228] It will be understood that the above-described embodiments are only specific examples and other embodiments are contemplated in accordance with the present disclosure.

[0229] Additionally, the following numbered items are provided in accordance with this disclosure: Item 1. 1. A method of controlling an aerosol generation system, the method comprising: 1. An induction heating arrangement configured to heat an aerosol-forming substrate, comprising: an induction heating element including at least one susceptor heatable by transmission of a fluctuating magnetic field to heat an aerosol-forming substrate; A first inductor coil; and a second inductor coil; and a power source configured to provide power to the induction heating arrangement; The method is driving a first varying current in a first inductor coil to generate a first varying magnetic field for heating a first portion of the induction heating element, and controlling the first varying current to increase a temperature of the first portion of the induction heating element from an initial temperature to a first operating temperature; driving a second varying current in the second inductor coil to generate a second varying magnetic field to heat a second portion of the induction heating element, and controlling the second varying current to raise a temperature of the second portion of the induction heating element from an initial temperature to a second operating temperature; the second varying current is not driven when the first varying current is driven; The method, wherein the first varying current is not driven when the second varying current is driven. Item 2. The first varying current and the second varying current In a first stage, a first varying current is supplied to a first inductor coil; 2. The method of claim 1, wherein in a second stage, a second varying current is controlled to be supplied to the second coil. Item 3. 3. The method of claim 2, wherein in a first stage, a first varying current and a second varying current are alternately driven to drive a first varying current in a first inductor coil and a second varying current in a second inductor coil. Item 4. 4. The method of claim 2 or 3, wherein in a second stage, the first varying current and the second varying current are alternately driven to drive the first varying current in the first inductor coil and the second varying current in the second inductor coil. Item 5. 5. The method according to any one of items 2, 3 or 4, wherein the first step has a predetermined duration. Item 6. 6. The method according to any one of items 2 to 5, wherein the second step has a predetermined duration. Item 7. 7. The method according to any one of items 2 to 6, wherein the duration of the second stage is shorter than the duration of the first stage. Item 8. 7. The method according to any one of items 2 to 6, wherein the duration of the second stage is longer than the duration of the first stage. Item 9. 9. The method according to any one of items 2 to 8, wherein the duration of the first step is from about 50 seconds to about 200 seconds. Item 10. 10. The method according to any one of items 2 to 9, wherein the duration of the second step is from about 50 seconds to about 200 seconds. Item 11. 11. The method according to any one of items 2 to 10, wherein the combined duration of the first and second steps is from about 100 seconds to about 400 seconds. Item 12. 12. The method of any one of claims 2 to 11, wherein the system further comprises a puff detector configured to detect when a user puffs on the system and receives the aerosol. Item 13. 13. The method of claim 12, wherein the duration of the first stage is based on a first predetermined number of puffs detected by the puff detector. Item 14. Item 14. The method according to item 13, wherein the first predetermined number of puffs is 2 to 5 puffs. Item 15. 15. The method of any one of items 12 to 14, wherein the duration of the second stage is based on a second predetermined number of puffs detected by the puff detector. Item 16. Item 16. The method according to item 15, wherein the second predetermined number of puffs is 2 to 5 puffs. Item 17. 17. The method according to any one of items 12 to 16, wherein the combined duration of the first stage and the second stage is based on a combined predetermined number of puffs detected by a puff detector. Item 18. 18. The method of claim 17, wherein the combined predetermined number of puffs is between 3 and 10 user puffs. Item 19. 13. The method of claim 12, wherein the first stage is terminated after a first maximum number of puffs is detected or earlier if a first maximum duration is reached. Item 20. 20. The method according to item 19, wherein the first maximum number of puffs is 2 to 5, and the first maximum duration is 50 seconds to about 200 seconds. Item 21. 21. The method of any one of items 12, 19 or 20, wherein the second stage is terminated after a second maximum number of puffs is detected or before a second maximum duration is reached. Item 22. 22. The method according to item 21, wherein the second maximum number of puffs is 2 to 5, and the second maximum duration is 50 seconds to about 200 seconds. Item 23. the first varying current is controlled to increase a temperature of a first portion of the induction heating element from an initial temperature according to a first operating temperature profile; 23. The method of any one of items 2 to 22, wherein the second varying current is controlled to increase the temperature of the second portion of the induction heating element from an initial temperature according to a second operating temperature profile. Item 24. 24. The method of claim 23, wherein the first operating temperature profile is substantially constant. Item 25. 24. The method of claim 23, wherein the first operating temperature profile varies with time. Item 26. 26. The method of any one of items 23, 24 and 25, wherein the second operating temperature profile is substantially constant. Item 27. 26. The method of any one of items 23, 24 and 25, wherein the second operating temperature profile varies with time. Item 28. 24. The method of claim 23, wherein during at least a portion of the first stage, the first operating temperature profile is greater than the second operating temperature profile. Item 29. 29. The method of claim 28, wherein during at least a portion of the first stage, the first operating temperature profile is at least about 50 degrees Celsius greater than the second operating temperature profile. Item 30. 30. The method of claim 28 or 29, wherein the first operating temperature profile is greater than the second operating temperature profile throughout the first stage. Item 31. 31. The method according to any one of items 23 to 30, wherein in the second stage, the first operating temperature profile and the second operating temperature profile are substantially the same. Item 32. 31. The method of any one of items 23 to 30, wherein in the second stage, the second operating temperature profile is within 5 degrees Celsius of the first operating temperature profile. Item 33. 31. The method according to any one of items 23 to 30, wherein during at least a portion of the second stage, the second operating temperature profile is greater than the first operating temperature profile. Item 34. Item 34. The method of item 33, wherein in the second stage, the second operating temperature profile is no more than about 50 degrees Celsius greater than the first operating temperature profile. Item 35. 35. The method of any one of items 23 to 34, wherein the first operating temperature profile is substantially constant during at least a portion of the first stage. Item 36. Item 36. The method of item 35, wherein the first operating temperature profile is constant during the first stage. Item 37. 37. The method of any one of items 23 to 36, wherein the first operating temperature profile is substantially constant during at least a portion of the second stage. Item 38. Item 38. The method of item 37, wherein the first operating temperature profile is constant during the second stage. Item 39. 29. The method of any one of items 23 to 28, wherein the second operating temperature profile is substantially constant during at least a portion of the second stage. Item 40. 40. The method of claim 39, wherein the second operating temperature profile is constant during the second stage. Item 41. 41. The method of any one of items 23 to 40, wherein the first operating temperature profile is between about 180 degrees Celsius and about 300 degrees Celsius during at least a portion of the first stage. Item 42. 42. The method of any one of items 23 to 41, wherein the first operating temperature profile is between about 160 degrees Celsius and about 260 degrees Celsius during at least a portion of the second stage. Item 43. 43. The method of any one of items 23 to 42, wherein the second operating temperature is between about 180 degrees Celsius and about 300 degrees Celsius during at least a portion of the second stage. Item 44. 44. The method of any one of items 1 to 43, further comprising: monitoring the first varying current; and determining a temperature of the first portion of the induction heating element based on the monitored first varying current. Item 45. 45. The method of any one of items 1-44, further comprising: monitoring the second varying current; and determining a temperature of the second portion of the induction heating element based on the monitored second varying current. Item 46. Item 44. The method of any one of items 1 to 43, wherein the system further comprises a temperature sensor configured to sense a temperature of the induction heating element. Item 47. Item 47. The method of item 46, wherein the first varying current is controlled based on a temperature of the induction heating element sensed by a temperature sensor. Item 48. 48. The method of claim 46 or 47, wherein the second varying current is controlled based on a temperature of the induction heating element sensed by a temperature sensor. Item 49. The system, a first temperature sensor configured to sense a temperature of a first portion of the induction heating element; and a second temperature sensor configured to sense a temperature of a second portion of the induction heating element. Item 50. 50. The method of claim 49, wherein the first varying current is controlled based on a temperature of the first portion of the induction heating element sensed by a first temperature sensor. Item 51. 51. The method of claim 49 or 50, wherein the second varying current is controlled based on a temperature of the second portion of the induction heating element sensed by a second temperature sensor. Item 52. Item 52. The method according to any one of items 1 to 51, wherein the power supply is a DC power supply and the system further comprises a DC / AC converter between the power supply and the induction heating arrangement. Item 53. Item 53. The method according to any one of items 1 to 52, wherein the first varying current is driven with a plurality of pulses, and the first varying current is controlled by pulse width modulation. Item 54. 54. The method according to any one of items 1 to 53, wherein the second varying current is driven with a plurality of pulses, and the second varying current is controlled by pulse width modulation. Item 55. Item 53. The method of item 52, wherein the system further comprises a DC / DC converter between the power supply and the DC / AC converter. Item 56. Item 56. The method of item 55, wherein the first varying current is controlled by controlling the amplitude of the first varying current using a DC / DC converter. Item 57. 57. The method of claim 55 or 56, wherein the second varying current is controlled by controlling the amplitude of the second varying current using a DC / DC converter. Item 58. Item 58. The method according to any one of items 1 to 57, wherein the system further comprises an aerosol-forming substrate detector configured to detect the presence of an aerosol-forming substrate at a location heated by the induction heating element. Item 59. The method is detecting the presence of an aerosol-forming substrate using an aerosol-forming substrate detector; Item 59. The method of item 58, further comprising driving a first varying current in the first inductor coil when an aerosol-forming substrate is detected. Item 60. 1. An aerosol generating system, comprising: an aerosol-forming substrate; 1. An induction heating arrangement configured to heat an aerosol-forming substrate, comprising: an induction heating element including at least one susceptor heatable by transmission of a fluctuating magnetic field to heat an aerosol-forming substrate; A first inductor coil; and a second inductor coil; and a power source configured to provide power to the induction heating arrangement; 60. An aerosol generating system comprising: a controller configured to carry out the method steps according to any one of items 1 to 59. Item 61. 1. An aerosol generating system, comprising: an aerosol-forming substrate; 1. An induction heating arrangement configured to heat an aerosol-forming substrate, comprising: an induction heating element including at least one susceptor heatable by transmission of a fluctuating magnetic field to heat an aerosol-forming substrate; A first inductor coil; and a second inductor coil; and a power source configured to provide power to the induction heating arrangement; A controller, driving a first varying current in a first inductor coil to generate a first varying magnetic field for heating a first portion of the induction heating element, and controlling the first varying current to increase a temperature of the first portion of the induction heating element from an initial temperature to a first operating temperature; driving a second varying current in the second inductor coil to generate a second varying magnetic field for heating a second portion of the induction heating element, and controlling the second varying current to increase a temperature of the second portion of the induction heating element from an initial temperature to a second operating temperature; driving the first varying current when the second varying current is not driven; and a controller configured to drive a second varying current when the first varying current is not driven. Item 62. 62. The aerosol generating system of claim 60 or 61, wherein the induction heating element comprises a first portion, a second portion, and a separation portion between the first portion and the second portion. Item 63. Item 63. The aerosol generating system of item 62, wherein the first portion is a first susceptor and the second portion is a second susceptor. Item 64. Item 64. The aerosol generation system according to item 62 or 63, wherein the intermediate element is disposed in the separation between the first part and the second part. Item 65. Item 65. The aerosol generating system according to item 64, wherein the intermediate element comprises a thermally insulating material. Item 66. 66. An aerosol generation system according to item 64 or 65, wherein the intermediate element comprises an electrically insulating material. Item 67. 62. The aerosol generating system of claim 60 or 61, wherein the induction heating element comprises an elongated susceptor, the first portion of the induction heating element comprises a first portion of the susceptor, and the second portion of the induction heating element comprises a second portion of the susceptor. Item 68. The aerosol generating system an aerosol-generating article comprising an aerosol-forming substrate; 68. The aerosol generating system according to any one of items 60 to 67, comprising an aerosol generating device including a device cavity configured to receive an aerosol-generating article. Item 69. Item 69. The aerosol generation system of item 68, wherein the aerosol generation device comprises a power source and a controller. Item 70. 70. An aerosol generation system according to item 68 or 69, wherein the aerosol generation device comprises a first inductor coil and a second inductor coil. Item 71. 71. The aerosol generation system of item 70, wherein a first inductor coil is disposed around the device cavity and a second inductor coil is disposed around the device cavity. Item 72. 72. The aerosol generating system of claim 71, wherein the device cavity has a proximal end and a distal end opposite the proximal end, the proximal end being substantially open for receiving an aerosol generating article. Item 73. 73. The aerosol generation system of claim 72, wherein the first inductor coil is disposed toward a proximal end of the device cavity and the second inductor coil is disposed toward a distal end of the device cavity. Item 74. Item 74. The aerosol generating system of item 73, wherein the controller is configured to initiate heating of the aerosol-forming substrate when the aerosol-generating article is received within the device cavity by driving a first varying current in the first inductor coil and thereafter driving a second varying current in the second inductor coil. Item 75. 75. The aerosol generating system according to items 70 to 74, wherein the aerosol generating device comprises an induction heating element. Item 76. 76. The aerosol generation system of claim 75, wherein the induction heating element is a tubular induction heating element defining an interior cavity, and the device cavity is disposed within the induction heating element interior cavity. Item 77. 77. An aerosol generation system as described in item 75 or 76, wherein an induction heating element is disposed around the device cavity, a first portion of the induction heating element is disposed between the first inductor coil and the device cavity, and a second portion of the induction heating element is disposed between the second inductor coil and the device cavity. Item 78. Item 76. An aerosol generating system according to item 75, wherein the induction heating element is configured to extend into the device cavity and penetrate the aerosol-forming substrate of the aerosol-generating article when the aerosol-generating article is received in the device cavity. Item 79. 80. The aerosol generation system of claim 78, wherein the induction heating element is in the form of a blade or pin. Item 80. 75. The aerosol generating system according to any one of claims 70 to 74, wherein the aerosol generating article comprises an induction heating element. Item 81. 81. An aerosol generating system according to item 80, wherein the induction heating element substantially surrounds the aerosol-forming substrate such that the induction heating element is arranged to heat an outer surface of the aerosol-forming substrate. Item 82. 82. The aerosol generating system according to item 80 or 81, wherein the induction heating element is a tubular induction heating element defining an internal cavity, and the aerosol-forming substrate is disposed within the induction heating element internal cavity. Item 83. 83. The aerosol generating system according to any one of items 80, 81 or 82, wherein the induction heating element comprises a metal wrapper substantially surrounding the aerosol-forming substrate. Item 84. 81. The aerosol generating system according to item 80, wherein the induction heating element is disposed within the aerosol-forming substrate such that the induction heating element is substantially surrounded by the aerosol-forming substrate. Item 85. 85. The aerosol generating system according to item 84, wherein the induction heating element comprises an elongated susceptor substantially surrounded by the aerosol-forming substrate. Item 86. 85. The aerosol generating system according to item 84, wherein the induction heating element comprises a plurality of susceptors disposed within the aerosol-forming substrate. Item 87. 87. An aerosol generating system according to items 80 to 86, wherein the aerosol-generating article is in the form of a rod having a proximal end and a distal end, the mouthpiece being provided at the proximal end and the aerosol-forming substrate being provided at the distal end. Item 88. 88. The aerosol generating system according to item 87, wherein a first portion of the induction heating element is disposed towards a proximal end of the aerosol-forming substrate, and a second portion of the induction heating element is disposed towards a distal end of the aerosol-forming substrate. Item 89. 75. The aerosol generating system according to any one of items 70 to 74, wherein the aerosol generating article comprises a first portion of an induction heating element and the aerosol generating device comprises a second portion of an induction heating element. Item 90. 75. The aerosol generating system according to any one of items 70 to 74, wherein the aerosol generating article comprises the second portion of the induction heating element and the aerosol generating device comprises the first portion of the induction heating element. Item 91. An aerosol generating system as described in items 80 to 90, wherein the aerosol generating device further comprises an aerosol-generating article detector configured to detect the presence of an aerosol-generating article in the device cavity, the aerosol-generating article detector configured to detect a change in inductance when an aerosol-generating article is received in the device cavity. Item 92. Item 92. The aerosol-generating system of item 91, wherein the controller is further configured to initiate heating of the aerosol-forming substrate when it detects the presence of an aerosol-generating article in the device cavity. Item 93. An aerosol generation system as described in any one of items 60 to 92, wherein the system further comprises a puff detector configured to detect when a user puffs on the system and receives an aerosol, and the controller is configured to drive a first varying current in the first coil when it detects a puff on the system. Item 94. 94. The aerosol-generating system according to any one of items 68 to 93, wherein the aerosol-generating article comprises an aerosol-generation segment, the aerosol-generation segment comprising a first aerosol-forming substrate and a second aerosol-forming substrate. Item 95. Item 95. An aerosol generating system according to item 94, wherein the first aerosol-forming substrate is arranged to be heated by a first portion of the induction heating element when the aerosol-generating article is received by the aerosol generating device, and the second aerosol-forming substrate is arranged to be heated by a second portion of the induction heating element when the aerosol-generating article is received by the aerosol generating device. Item 96. 96. An aerosol-generating system according to item 94 or 95, wherein the composition of the second aerosol-forming substrate is substantially identical to the composition of the first aerosol-forming substrate. Item 97. 96. An aerosol generating system according to item 94 or 95, wherein the composition of the second aerosol-forming substrate is different from the composition of the first aerosol-forming substrate. Item 98. A method for operating an aerosol generating system according to any one of items 60 to 97, the method comprising a method step according to any one of items 1 to 59. Item 99. An aerosol generating device for the aerosol generating system according to any one of Items 60 to 97. Item 100. 1. An aerosol generating device configured to receive an aerosol-generating article comprising an aerosol-forming substrate and an induction heating element including at least one susceptor heatable by transmission of a fluctuating magnetic field to heat the aerosol-forming substrate, the aerosol generating device comprising: A first inductor coil; and A second inductor coil; a power source configured to provide power to the first inductor coil and the second inductor coil; A controller, driving a first varying current in a first inductor coil to generate a first varying magnetic field for heating a first portion of an induction heating element of an aerosol-generating article received by the aerosol generating device, and controlling the first varying current to increase a temperature of the first portion of the induction heating element from an initial temperature to a first operating temperature; driving a second varying current in the second inductor coil to generate a second varying magnetic field for heating a second portion of the induction heating element of an aerosol-generating article received by the aerosol generating device, and controlling the second varying current to increase the temperature of the second portion of the induction heating element from an initial temperature to a second operating temperature; driving the first varying current when the second varying current is not driven; and a controller configured to drive a second varying current when the first varying current is not driven. Item 101. An aerosol generating device, comprising: 1. An induction heating arrangement configured to heat an aerosol-forming substrate, comprising: an induction heating element including at least one susceptor heatable by transmission of a fluctuating magnetic field to heat an aerosol-forming substrate; A first inductor coil; and a second inductor coil; and a power source configured to provide power to the induction heating arrangement; 60. An aerosol generating device comprising: a controller configured to carry out the method steps according to any one of items 1 to 59. Item 102. An aerosol generating device, comprising: 1. An induction heating arrangement configured to heat an aerosol-forming substrate, comprising: an induction heating element including at least one susceptor heatable by transmission of a fluctuating magnetic field to heat an aerosol-forming substrate; A first inductor coil; and a second inductor coil; and a power source configured to provide power to the induction heating arrangement; A controller, driving a first varying current in a first inductor coil to generate a first varying magnetic field for heating a first portion of the induction heating element, and controlling the first varying current to increase a temperature of the first portion of the induction heating element from an initial temperature to a first operating temperature; driving a second varying current in the second inductor coil to generate a second varying magnetic field for heating a second portion of the induction heating element, and controlling the second varying current to increase a temperature of the second portion of the induction heating element from an initial temperature to a second operating temperature; driving the first varying current when the second varying current is not driven; and a controller configured to drive a second varying current when the first varying current is not driven. Item 103. Item 103. An aerosol generating device according to item 101 or 102, wherein the induction heating element comprises a first portion, a second portion, and a separation portion between the first portion and the second portion. Item 104. Item 104. The aerosol generating device of item 103, wherein the first portion is a first susceptor and the second portion is a second susceptor. Item 105. Item 105. An aerosol generating device according to item 103 or 104, wherein the intermediate element is disposed within the separation between the first part and the second part. Item 106. Item 106. An aerosol generating device according to item 105, wherein the intermediate element comprises a thermally insulating material. Item 107. 107. An aerosol generating device according to item 105 or 106, wherein the intermediate element comprises an electrically insulating material. Item 108. 103. The aerosol generating apparatus of claim 101 or 102, wherein the induction heating element comprises an elongated susceptor, the first portion of the induction heating element comprises a first portion of the susceptor, and the second portion of the induction heating element comprises a second portion of the susceptor. Item 109. Item 109. An aerosol generating device according to any one of items 101 to 108, wherein the aerosol generating device comprises a device cavity configured to receive an aerosol-forming substrate, a first inductor coil is arranged around the device cavity, a second inductor coil is arranged around the device cavity, a first portion of the induction heating element is arranged between the first inductor coil and the device cavity, and a second portion of the induction heating element is arranged between the second inductor coil and the device cavity. Item 110. Item 109. The aerosol generation system of item 109, wherein the induction heating element is a tubular induction heating element defining an internal cavity, and the device cavity is disposed within the induction heating element internal cavity. Item 111. 109. An aerosol generating system according to any one of items 101 to 108, wherein the aerosol generating device comprises a device cavity configured to receive an aerosol-forming substrate, and the induction heating element extends into the device cavity and is configured to penetrate the aerosol-forming substrate of the aerosol-generating article when the aerosol-generating article is received in the device cavity. Item 112. Item 112. The aerosol generation system according to item 111, wherein the induction heating element is in the form of a blade or pin. Item 113. 109. An aerosol generation device according to any one of items 100 to 108, wherein the aerosol generation device comprises a device cavity configured to receive an aerosol-forming substrate. Item 114. 114. An aerosol generating device according to any one of items 111 to 113, wherein a first inductor coil is disposed around the device cavity and a second inductor coil is disposed around the device cavity. Item 115. 115. An aerosol generating device according to items 109 to 114, wherein the device cavity has a proximal end and a distal end opposite the proximal end, the proximal end being substantially open for receiving an aerosol generating article. Item 116. Item 116. An aerosol generating device according to item 115, further comprising a cover movable over a proximal end of the device cavity to prevent insertion of an aerosol-generating article into the device cavity. Item 117. Item 117. An aerosol generating device according to item 115 or 116, wherein the first inductor coil is disposed towards a proximal end of the device cavity and the second inductor coil is disposed towards a distal end of the device cavity. Item 118. Item 117. An aerosol generating device as described in Item 117, wherein when an aerosol-generating article is received in the device cavity, the controller is configured to initiate heating of the aerosol-forming substrate by driving a first varying current in the first inductor coil and thereafter driving a second varying current in the second inductor coil. Item 119. Item 119. An aerosol generating device according to any one of items 109 to 118, further comprising an aerosol-generating article detector configured to detect the presence of an aerosol-generating article within the device cavity. Item 120. Item 119. An aerosol generating device as described in Item 119, wherein the aerosol-generating article detector includes an inductor and is configured to detect a change in inductance when an aerosol-generating article is received in the device cavity to detect the presence of an aerosol-generating article in the device cavity. Item 121. An aerosol generating device as described in item 119 or 120, wherein when the aerosol-generating article detector detects the presence of an aerosol-generating article in the device cavity, the controller is configured to initiate heating by driving a first varying current in the first inductor coil and then driving a second varying current in the second inductor coil. Item 122. 122. The aerosol generating device according to any one of items 100 to 121, further comprising a puff detector configured to detect when a user puffs through the system to receive the aerosol. Item 123. Item 123. An aerosol generating device as described in item 122, wherein when the smoke detector detects smoke in the system, the controller is configured to initiate heating by driving a first varying current in the first inductor coil and then driving a second varying current in the second inductor coil. Item 124. An aerosol generating device according to any one of items 100 to 123, wherein the controller is configured to monitor the first varying current and determine a temperature of the first portion of the induction heating element based on the monitored first varying current. Item 125. An aerosol generating device according to any one of items 100 to 124, wherein the controller is configured to monitor the second varying current and determine the temperature of the second portion of the induction heating element based on the monitored second varying current. Item 126. 124. The aerosol generating device according to any one of items 100 to 123, further comprising a temperature sensor configured to sense the temperature of the induction heating element. Item 127. Item 127. An aerosol generating device as described in item 126, wherein the controller is configured to control the first varying current based on the temperature of the induction heating element sensed by the temperature sensor. Item 128. Item 128. An aerosol generating device according to item 126 or 127, wherein the controller is configured to control the second varying current based on the temperature of the induction heating element sensed by the temperature sensor. Item 129. The aerosol generating device is a first temperature sensor configured to sense a temperature of a first portion of the induction heating element; The aerosol generating device according to any one of items 100 to 123, further comprising a second temperature sensor configured to sense the temperature of the second portion of the induction heating element. Item 130. Item 130. An aerosol generating device as described in item 129, wherein the controller is configured to control the first varying current based on the temperature of the first portion of the induction heating element sensed by the first temperature sensor. Item 131. Item 131. An aerosol generating device as described in item 129 or 130, wherein the controller is configured to control the second varying current based on the temperature of the second portion of the induction heating element sensed by the second temperature sensor. Item 132. 132. The aerosol generating apparatus according to any one of items 100 to 131, wherein the power source is a DC power source and the system further comprises a DC / AC converter between the power source and the induction heating arrangement. Item 133. An aerosol generating device described in any one of items 100 to 132, wherein the controller is configured to drive the first varying current in a plurality of pulses, and the controller is configured to control the first varying current by pulse width modulation. Item 134. An aerosol generating device according to any one of items 100 to 133, wherein the controller is configured to drive the second varying current in a plurality of pulses, and the controller is configured to control the second varying current by pulse width modulation. Item 135. Item 133. An aerosol generating device according to item 132, further comprising a DC / DC converter between the power supply and the DC / AC converter. Item 136. Item 136. An aerosol generating device as described in item 135, wherein the controller is configured to control the first varying current by controlling the amplitude of the first varying current using a DC / DC converter. Item 137. Item 137. An aerosol generating device as described in item 135 or 136, wherein the controller is configured to control the second varying current by controlling the amplitude of the second varying current using a DC / DC converter. Item 138. An aerosol generating device described in any one of items 100 to 137, further comprising a first switch between the power source and the first inductor coil and a second switch between the power source and the second inductor coil, wherein the controller is configured to turn the first switch on and off at a first switching rate when the second switch remains off to drive a first varying current in the first inductor coil, and wherein the controller is configured to turn the second switch on and off at a second switching rate when the first switch remains off to drive a second varying current in the second inductor coil. Item 139. Item 139. The aerosol generating device according to any one of items 100 to 138, wherein the first inductor coil and the second inductor coil are wound in the same direction. Item 140. 139. The aerosol generating device according to any one of items 100 to 138, wherein the second coil is wound in a different direction than the first coil. Item 141. The controller In a first stage, a first varying current is supplied to a first inductor coil; 141. The aerosol generating device according to any one of items 100 to 140, further configured such that in a second stage, a second varying current is supplied to the second coil. Item 142. Item 142. The aerosol generating device of item 141, wherein the controller is further configured such that in a first stage, the first varying current and the second varying current are alternately driven to drive a first varying current in the first inductor coil and a second varying current in the second inductor coil. Item 143. An aerosol generating device as described in item 141 or 142, wherein the controller is further configured such that in a second stage, the first varying current and the second varying current are alternately driven to drive a first varying current in the first inductor coil and a second varying current in the second inductor coil. Item 144. 144. An aerosol generating device according to any one of items 141, 142 or 143, wherein the first stage has a predetermined duration. Item 145. 145. The aerosol generating device according to any one of items 141 to 144, wherein the second stage has a predetermined duration. Item 146. 146. The aerosol generating device according to any one of items 141 to 145, wherein the duration of the second stage is shorter than the duration of the first stage. Item 147. 146. The aerosol generating device according to any one of items 141 to 145, wherein the duration of the second stage is longer than the duration of the first stage. Item 148. 148. The aerosol generating apparatus according to any one of items 141 to 147, wherein the duration of the first stage is from about 50 seconds to about 200 seconds. Item 149. 149. The aerosol generating apparatus according to any one of items 141 to 148, wherein the duration of the second stage is from about 50 seconds to about 200 seconds. Item 150. 150. The aerosol generating apparatus according to any one of items 141 to 149, wherein the combined duration of the first and second stages is from about 100 seconds to about 400 seconds. Item 151. 151. The aerosol generating device according to any one of items 141 to 150, further comprising a puff detector configured to detect when a user puffs through the system to receive the aerosol. Item 152. Item 152. The aerosol generating device of item 151, wherein the duration of the first stage is based on a first predetermined number of puffs detected by the puff detector. Item 153. Item 153. The aerosol generating device according to item 152, wherein the first predetermined number of puffs is 2 to 5 puffs. Item 154. 154. The aerosol generating device according to any one of items 151 to 153, wherein the duration of the second stage is based on a second predetermined number of puffs detected by the puff detector. Item 155. Item 155. The aerosol generating device according to item 154, wherein the second predetermined number of puffs is 2 to 5 puffs. Item 156. 156. The aerosol generating device according to any one of items 151 to 155, wherein the combined duration of the first and second stages is based on a combined predetermined number of puffs detected by a puff detector. Item 157. Item 157. The aerosol generating device according to item 156, wherein the combined predetermined number of puffs is between 3 and 10 user puffs. Item 158. Item 152. The aerosol generating device of item 151, wherein the first stage is terminated after a first maximum number of puffs is detected or earlier if a first maximum duration is reached. Item 159. Item 159. The aerosol generating apparatus according to item 158, wherein the first maximum number of puffs is 2 to 5, and the first maximum duration is 50 seconds to about 200 seconds. Item 160. 159. An aerosol generating device according to any one of items 151, 158 or 159, wherein the second stage is terminated after a maximum number of puffs has been detected or earlier if a second maximum duration has been reached. Item 161. Item 161. The aerosol generating apparatus according to item 160, wherein the second maximum number of puffs is 2 to 5, and the second maximum duration is 50 seconds to about 200 seconds. Item 162. The controller the first varying current is controlled to increase a temperature of a first portion of the induction heating element from an initial temperature according to a first operating temperature profile; Item 162. An aerosol generating device according to any one of items 141 to 161, wherein the second varying current is controlled to increase the temperature of the second portion of the induction heating element from an initial temperature according to a second operating temperature profile. Item 163. Item 163. An aerosol generating device according to item 162, wherein the first operating temperature profile is substantially constant. Item 164. Item 163. An aerosol generating device as described in item 162, wherein the first operating temperature profile varies over time. Item 165. 165. An aerosol generating device according to any one of items 162, 163 and 164, wherein the second operating temperature profile is substantially constant. Item 166. An aerosol generating device according to any one of items 162, 163 and 164, wherein the second operating temperature profile varies over time. Item 167. Item 163. An aerosol generating device as described in item 162, wherein during at least a portion of the first stage, the first operating temperature profile is greater than the second operating temperature profile. Item 168. Item 168. An aerosol generating device as described in item 167, wherein during at least a portion of the first stage, the first operating temperature profile is at least 50 degrees Celsius greater than the second operating temperature profile. Item 169. 169. An aerosol generating device according to item 167 or 168, wherein the first operating temperature profile is greater than the second operating temperature profile throughout the first stage. Item 170. 169. The aerosol generating apparatus according to any one of items 162 to 169, wherein in the second stage, the first operating temperature profile and the second operating temperature profile are substantially the same. Item 171. 169. An aerosol generating apparatus according to any one of items 162 to 169, wherein in the second stage, the second operating temperature profile is within 5 degrees Celsius of the first operating temperature profile. Item 172. 169. An aerosol generating device according to any one of items 162 to 169, wherein during at least a portion of the second stage, the second operating temperature profile is greater than the first operating temperature profile. Item 173. Item 173. The aerosol generating device of item 172, wherein in the second stage, the second operating temperature profile is no more than about 50 degrees Celsius greater than the first operating temperature profile. Item 174. 174. An aerosol generating device according to any one of items 162 to 173, wherein the first operating temperature profile is substantially constant during at least a portion of the first stage. Item 175. Item 175. An aerosol generating device according to item 174, wherein the first operating temperature profile is constant during the first stage. Item 176. 176. An aerosol generating device according to any one of items 162 to 175, wherein the first operating temperature profile is substantially constant during at least a portion of the second stage. Item 177. Item 177. The aerosol generating device of item 176, wherein the first operating temperature profile is constant during the second stage. Item 178. 168. An aerosol generating device according to any one of items 162 to 167, wherein the second operating temperature profile is substantially constant during at least a portion of the second stage. Item 179. Item 179. The aerosol generating device of item 178, wherein the second operating temperature profile is constant during the second stage. Item 180. 179. An aerosol generating device according to any one of items 162 to 179, wherein the first operating temperature profile is between about 180 degrees Celsius and 300 degrees Celsius during at least a portion of the first stage. Item 181. 181. An aerosol generating device according to any one of items 162 to 180, wherein the first operating temperature profile is between about 160 degrees Celsius and about 260 degrees Celsius during at least a portion of the second stage. Item 182. 182. The aerosol generating device according to any one of items 162 to 181, wherein the second operating temperature is between about 180 degrees Celsius and about 300 degrees Celsius during at least a portion of the second stage. Item 183. An aerosol generating system comprising the aerosol generating device according to any one of Items 100 to 182 and an aerosol-generating article including an aerosol-forming substrate.

Claims

1. 1. A method of controlling an aerosol generation system, the system comprising: a device cavity configured to receive an aerosol-forming substrate; 1. An induction heating arrangement configured to heat an aerosol-forming substrate, comprising: an induction heating element including at least one susceptor heatable by transmission of a varying magnetic field to heat said aerosol-forming substrate; a first inductor coil disposed about the device cavity, a first portion of the induction heating element being disposed between the first inductor coil and the device cavity; and an induction heating arrangement including a second inductor coil disposed about the device cavity, a second portion of the induction heating element being disposed between the second inductor coil and the device cavity, the second inductor coil having a different number of turns than the first inductor coil; a power source configured to provide power to the induction heating arrangement; An aerosol generating device comprising: the device cavity having a proximal end and a distal end opposite the proximal end, the proximal end being substantially open for receiving the aerosol-forming substrate; the first inductor coil is disposed toward the proximal end of the device cavity and the second inductor coil is disposed toward the distal end of the device cavity; The method further comprising: when the aerosol-forming substrate is received in the device cavity, initiating heating of the aerosol-forming substrate by driving a first varying current in the first inductor coil to generate a first varying magnetic field for heating a first portion of the induction heating element, and controlling the first varying current to raise a temperature of the first portion of the induction heating element from an initial temperature to a first operating temperature; thereafter, driving a second varying current in the second inductor coil to generate a second varying magnetic field to heat a second portion of the induction heating element, and controlling the second varying current to raise a temperature of the second portion of the induction heating element from an initial temperature to a second operating temperature; the second varying current is not driven when the first varying current is driven; The method, wherein the first varying current is not driven when the second varying current is driven.

2. The method of claim 1, wherein the second inductor coil is wound in a different direction than the first inductor coil.

3. the first varying current and the second varying current In a first stage, the first varying current is supplied to the first inductor coil; 3. The method of claim 1 or 2, wherein in a second stage, the second varying current is controlled to be supplied to the second coil.

4. 4. The method of claim 3, wherein in the first stage, the first varying current and the second varying current are alternately driven to drive the first varying current into the first inductor coil and the second varying current into the second inductor coil.

5. 5. The method of claim 3 or 4, wherein in the second stage, the first varying current and the second varying current are alternately driven to drive the first varying current into the first inductor coil and the second varying current into the second inductor coil.

6. 6. The method of claim 3, 4 or 5, wherein the first stage has a predetermined duration and the second stage has a predetermined duration.

7. 7. The method of claim 6, wherein the duration of the second stage is shorter than the duration of the first stage.

8. the first varying current is controlled to increase a temperature of the first portion of the induction heating element from an initial temperature according to a first operating temperature profile; 8. The method of claim 3, wherein the second varying current is controlled to increase a temperature of the second portion of the induction heating element from an initial temperature according to a second operating temperature profile.

9. The method of claim 8 , wherein the first operating temperature profile is greater than the second operating temperature profile throughout the first stage.

10. 10. The method of claim 8 or 9, wherein during at least a portion of the second stage, the second operating temperature profile is greater than the first operating temperature profile.

11. 11. The method of claim 10, wherein in the second stage, the second operating temperature profile is no more than about 50 degrees Celsius greater than the first operating temperature profile.

12. An aerosol generating device, comprising: a device cavity configured to receive an aerosol-forming substrate; 1. An induction heating arrangement configured to heat an aerosol-forming substrate, comprising: an induction heating element including at least one susceptor heatable by transmission of a varying magnetic field to heat said aerosol-forming substrate; a first inductor coil disposed about the device cavity, a first portion of the induction heating element being disposed between the first inductor coil and the device cavity; and an induction heating arrangement including a second inductor coil disposed about the device cavity, a second portion of the induction heating element being disposed between the second inductor coil and the device cavity, the second inductor coil having a different number of turns than the first coil; a power source configured to provide power to the induction heating arrangement; A controller configured to carry out the steps of the method according to any one of claims 1 to 14, the device cavity having a proximal end and a distal end opposite the proximal end, the proximal end being substantially open for receiving the aerosol-forming substrate; An aerosol generation device, wherein the first inductor coil is disposed toward the proximal end of the device cavity and the second inductor coil is disposed toward the distal end of the device cavity.

13. 13. The aerosol generating device of claim 12, wherein the second inductor coil is wound in a different direction than the first inductor coil.

14. 14. The aerosol generating device of claim 12 or 13, wherein the controller is configured to drive the first varying current in a plurality of pulses, and the controller is configured to control the first varying current by pulse width modulation.

15. 15. An aerosol generating device as described in any one of claims 12, 13 or 14, wherein the controller is configured to drive the second varying current in a plurality of pulses, and the controller is configured to control the second varying current by pulse width modulation.

16. 16. The aerosol generating device of any one of claims 12 to 15, further comprising a first switch between the power source and the first inductor coil and a second switch between the power source and the second inductor coil, the controller being configured to turn the first switch on and off at a first switching rate when the second switch remains off to drive the first varying current in the first inductor coil, and the controller being configured to turn the second switch on and off at a second switching rate when the first switch remains off to drive the second varying current in the second inductor coil.

17. an aerosol-generating article comprising an aerosol-forming substrate; An aerosol generating system comprising the aerosol generating device according to any one of claims 12 to 16.

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