Aerosol generation device comprising an induction heating arrangement comprising a first inductor coil and a second inductor coil

Abstract

The aerosol-generating apparatus comprises an induction heating arrangement configured to heat an aerosol-forming substrate, the induction heating arrangement comprising a susceptor arrangement heatable by penetration of a changing magnetic field for heating the aerosol-forming substrate, at least a first inductor coil and at least a second inductor coil, and a controller configured to drive the first inductor coil with a first alternating pulse-width modulated signal to generate a first alternating magnetic field for heating a first portion of the susceptor arrangement, the controller configured to drive the second inductor coil with a second alternating pulse-width modulated signal to generate a second alternating magnetic field for heating a second portion of the susceptor arrangement, and the controller configured to supply the first alternating pulse-width modulated signal and the second alternating pulse-width modulated signal with complementary duty cycles. The aerosol-generating system comprises an aerosol-generating device and an aerosol-generating article including the aerosol-forming substrate.

Description

[Technical field]

[0001] The present disclosure relates to an aerosol generating device having an inductive heating arrangement, a method for controlling an aerosol generating device having an inductive heating arrangement, and an aerosol generating system comprising an aerosol generating 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 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 in 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 varying magnetic field, generating eddy currents and hysteresis losses in the susceptor, which heats the susceptor and, thereby, the aerosol-forming substrate. Inductive heating allows aerosols to be generated without exposing the heater to the aerosol-generating article. This can improve the ease with which the heater can be cleaned.

[0003] Some known aerosol generating devices include two or more inductor coils, each arranged to heat a different portion of the susceptor. Such aerosol generating devices may be used to heat different portions of the aerosol-generating article at different times or to different temperatures. However, for such aerosol generating devices, it may 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 invention, there is provided an aerosol generating apparatus comprising: an induction heating arrangement configured to heat an aerosol-forming substrate, the induction heating arrangement comprising a susceptor arrangement heatable by penetration of a changing magnetic field for heating the aerosol-forming substrate; at least a first inductor coil and at least a second inductor coil; and a controller, the controller configured to drive the first inductor coil with a first alternating pulse-width modulated signal to generate a first alternating magnetic field for heating a first portion of the susceptor arrangement, the controller configured to drive the second inductor coil with a second alternating pulse-width modulated signal to generate a second alternating magnetic field for heating a second portion of the susceptor arrangement, and the controller configured to supply the first alternating pulse-width modulated signal and the second alternating pulse-width modulated signal with complementary duty cycles.

[0006] As used herein, the term "duty cycle" refers to the amount of time a signal is on and the amount of time the signal is off. Duty cycles are given as a percentage. A 60% duty cycle means that the signal is on 60% of the time and the signal is off 40% of the time.

[0007] As used herein, the term "complementary duty cycle" refers to two signals, one signal is on while the other signal is off. The signals may have a sawtooth pattern, where the second signal has an inverse sawtooth pattern than the first signal. The combined signals may result in a continuous AC current.

[0008] In some embodiments, the duty cycles of the first and second signals are gradually transitioned, i.e. the duty cycle of the first signal may decrease while the duty cycle of the second signal may increase, or vice versa.

[0009] The controller may be configured to supply a first alternating pulse-width modulated signal to the first inductor coil during a first stage to increase a temperature of a first portion of the susceptor arrangement from an initial temperature to a first operating temperature, and the controller is configured to supply the first alternating pulse-width modulated signal during the first stage with a duty cycle of greater than 50%, preferably greater than 60%, preferably greater than 70%, more preferably greater than 80%, and most preferably greater than 90%.

[0010] The controller may be configured to supply a first alternating pulse-width modulated signal to the first inductor coil during the second stage to reduce a temperature of the first portion of the susceptor arrangement from the first operating temperature to the second operating temperature, and the controller is configured to supply the first alternating pulse-width modulated signal during the second stage with a duty cycle of less than 50%, preferably less than 40%, preferably less than 30%, more preferably less than 20%, and most preferably less than 10%.

[0011] The controller may be configured to supply a second alternating pulse-width modulated signal to the second inductor coil during the first stage to raise a temperature of the second portion of the susceptor arrangement from an initial temperature to a third operating temperature lower than the first operating temperature, and the controller is configured to supply the second alternating pulse-width modulated signal during the first stage with a duty cycle lower than 50%, preferably lower than 40%, preferably lower than 30%, more preferably lower than 20%, and most preferably lower than 10%.

[0012] The controller may be configured to supply a second alternating pulse-width modulated signal to the second inductor coil during the second stage to raise a temperature of the second portion of the susceptor arrangement from the third operating temperature to a fourth operating temperature higher than the second operating temperature, and the controller is configured to supply the second alternating pulse-width modulated signal during the second stage with a duty cycle of greater than 50%, preferably greater than 60%, preferably greater than 70%, more preferably greater than 80%, and most preferably greater than 90%.

[0013] The controller may be configured to provide the first alternating pulse-width modulated signal with a duty cycle greater than 80% during the first stage, and the controller is configured to provide the second alternating pulse-width modulated signal with a duty cycle less than 20% during the first stage.

[0014] The controller may be configured to provide a first alternating pulse-width modulated signal with a duty cycle greater than 90% during the first stage, and the controller is configured to provide a second alternating pulse-width modulated signal with a duty cycle less than 10% during the first stage.

[0015] The controller may be configured to provide the first alternating pulse-width modulated signal with a duty cycle of less than 20% during the second stage, and the controller is configured to provide the second alternating pulse-width modulated signal with a duty cycle of greater than 80% during the second stage.

[0016] The controller may be configured to provide the first alternating pulse-width modulated signal with a duty cycle of less than 10% during the second stage, and the controller is configured to provide the second alternating pulse-width modulated signal with a duty cycle of greater than 90% during the second stage.

[0017] The aerosol generating device may further comprise a power supply for providing power to the induction heating arrangement.

[0018] The controller may comprise a microcontroller.

[0019] The microcontroller may be configured to utilize a clock frequency of the microcontroller as one or both of the alternating frequencies of the first alternating pulse width modulated signal and the second alternating pulse width modulated signal.

[0020] The aerosol generating device may further comprise an oscillator for generating one or both of the alternating frequencies of the first alternating pulse width modulated signal and the second alternating pulse width modulated signal.

[0021] The controller may further comprise an oscillator for generating one or both of the alternating frequencies of the first alternating pulse-width modulated signal and the second alternating pulse-width modulated signal.

[0022] The aerosol generating device may further comprise a first power stage, the first power stage comprising at least a first inductor coil and a first capacitor.

[0023] The first inductor coil and the first capacitor may be arranged as a first LC circuit.

[0024] The aerosol generating device may further comprise a second power stage, the second power stage comprising at least a second inductor coil and a second capacitor.

[0025] The second inductor coil and the second capacitor may be arranged as a second LC circuit.

[0026] According to the present invention there is also provided an aerosol generating system comprising an aerosol generating device according to the present invention and an aerosol-generating article comprising an aerosol-forming substrate.

[0027] According to the present invention there is also provided a method of controlling an aerosol generating apparatus comprising an induction heating arrangement configured to heat an aerosol-forming substrate, the induction heating arrangement comprising a susceptor arrangement heatable by penetration of a changing magnetic field for heating the aerosol-forming substrate, at least a first inductor coil and at least a second inductor coil, and a controller, the controller being configured to drive the first inductor coil and the second inductor coil, the method comprising: driving the first inductor coil with a first pulse-width modulated signal to generate a first alternating magnetic field for heating a first portion of the susceptor arrangement; driving the second inductor coil with a second pulse-width modulated signal to generate a second alternating magnetic field for heating a second portion of the susceptor arrangement; and supplying a first pulse-width modulated signal having a duty cycle complementary to a duty cycle of the second pulse-width modulated signal.

[0028] During the first stage, a first alternating pulse-width modulated signal may be supplied to the first inductor coil to raise the temperature of the first portion of the susceptor arrangement from an initial temperature to a first operating temperature, and during the first stage, the first alternating pulse-width modulated signal is supplied with a duty cycle of greater than 50%, preferably greater than 60%, preferably greater than 70%, more preferably greater than 80%, and most preferably greater than 90%.

[0029] During the second stage, a first alternating pulse-width modulated signal may be supplied to the first inductor coil to reduce the temperature of the first portion of the susceptor arrangement from the first operating temperature to the second operating temperature, and during the second stage, the first alternating pulse-width modulated signal is supplied with a duty cycle of less than 50%, preferably less than 40%, preferably less than 30%, more preferably less than 20%, and most preferably less than 10%.

[0030] During the first stage, a second alternating pulse-width modulated signal may be supplied to the second inductor coil to raise the temperature of the second portion of the susceptor arrangement from the initial temperature to a third operating temperature, the second alternating pulse-width modulated signal being supplied with a duty cycle of less than 50%, preferably less than 40%, preferably less than 30%, more preferably less than 20%, and most preferably less than 10% during the first stage.

[0031] During the second stage, a second alternating pulse-width modulated signal may be supplied to the second inductor coil to raise the temperature of the second portion of the susceptor arrangement from the third operating temperature to a fourth operating temperature, and during the second stage, the second alternating pulse-width modulated signal is supplied with a duty cycle of greater than 50%, preferably greater than 60%, preferably greater than 70%, more preferably greater than 80%, and most preferably greater than 90%.

[0032] During the first stage, the first alternating pulse width modulated signal may be provided with an 80% duty cycle, and during the first stage, the second alternating pulse width modulated signal is provided with a 20% duty cycle.

[0033] During the first stage, the first alternating pulse width modulated signal may be provided with a 90% duty cycle, and during the first stage, the second alternating pulse width modulated signal is provided with a 10% duty cycle.

[0034] During the second stage the first alternating pulse width modulated signal may be provided with a 20% duty cycle, and during the second stage the second alternating pulse width modulated signal is provided with an 80% duty cycle.

[0035] During the second stage the first alternating pulse width modulated signal may be provided with a 10% duty cycle, and during the second stage the second alternating pulse width modulated signal is provided with a 90% duty cycle.

[0036] As used herein, the term "aerosol-forming substrate" relates to a substrate capable of releasing 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.

[0037] 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.

[0038] As used herein, the term "aerosol-generating device" refers to a device that interacts with an aerosol-forming substrate to generate an aerosol.

[0039] As used herein, the term "aerosol generating system" refers to the combination of an aerosol generating device with an aerosol generating article, in which the aerosol generating article and the aerosol generating device work together to generate a respirable aerosol.

[0040] As used herein, the term "changing current" includes any current that changes over time to generate a changing magnetic field. The term "changing current" is intended to include alternating current. When the changing current is an alternating current, the alternating current generates an alternating magnetic field.

[0041] As used herein, the term "length" refers to the major longitudinal dimension of an aerosol-generating device or article, or a component of an aerosol-generating device or article.

[0042] As used herein, the term "width" refers to the major transverse dimension of an aerosol-generating device or article, or a component of an aerosol-generating device or article, at a particular location along its length. The term "thickness" refers to the dimension in the transverse direction perpendicular to the width.

[0043] As used herein, the term "transverse cross-section" is used to describe a cross-section of an aerosol generating device or an aerosol generating article, or of a component of an aerosol generating device or an aerosol generating article, along its length in a direction perpendicular to the longitudinal axis at a particular location thereof.

[0044] As used herein, the term "proximal" refers to the user end or oral 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 oral end of the aerosol generating device or aerosol generating article. As used herein, the term "distal" refers to the end opposite the proximal end.

[0045] The first stage may have a predetermined duration. The second stage may have a predetermined duration. The duration of the first stage and the second stage may be the same. The duration of the second stage may be different to 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.

[0046] 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 and second stages may be from about 100 seconds to about 400 seconds. The combined duration of the first and second stages may be from about 150 seconds to about 300 seconds.

[0047] 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 and second stages may be based on a combined predetermined number of puffs detected by the puff detector. The combined predetermined number of puffs may be between 3 and 10 puffs of the user.

[0048] 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.

[0049] In some preferred embodiments, the second stage is terminated after a second maximum number of puffs is detected or before a 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.

[0050] The first alternating pulse-width modulated signal may be controlled to increase a temperature of the first section of the susceptor arrangement from an initial temperature according to a first operating temperature profile, the first temperature profile being a predetermined desired temperature of the first section of the susceptor arrangement over time, and if at any given time the actual temperature of the first section of the susceptor arrangement differs from the temperature of the first temperature profile at that time, the first alternating pulse-width modulated signal is adjusted to adjust the temperature of the first section of the susceptor arrangement to the temperature specified by the first temperature profile at that time.

[0051] Similarly, the second alternating pulse-width modulated signal may be controlled to increase the temperature of the second section of the susceptor arrangement from an initial temperature according to a second temperature profile, the second temperature profile being a predetermined desired temperature of the second section of the susceptor arrangement over time. If at any given time the actual temperature of the second section of the susceptor arrangement differs from the temperature of the second temperature profile at that time, the second alternating pulse-width modulated signal is adjusted to adjust the temperature of the second section of the susceptor arrangement to the temperature specified by the second temperature profile at that time.

[0052] In some embodiments, the first operating temperature profile is substantially constant. In some embodiments, the first operating temperature profile varies over time.

[0053] In some embodiments, the second operating temperature profile is substantially constant. In some embodiments, the second operating temperature profile varies over time.

[0054] In some embodiments, during at least a portion of the first stage, the first operating temperature profile is higher than the second operating temperature profile. In these embodiments, during at least a portion of the first stage, the first operating temperature profile is higher than the second operating temperature profile by at least about 50 degrees Celsius. The first operating temperature profile may be higher than the second operating temperature profile throughout the entire first stage.

[0055] In some embodiments, during the second stage, the first operating temperature profile and the second operating temperature profile are substantially the same, hi some embodiments, during the second stage, the second operating temperature profile is within about 5 degrees Celsius of the first operating temperature profile.

[0056] In some embodiments, during at least a portion of the second stage, the second operating temperature profile is higher than the first operating temperature profile. In these embodiments, during the second stage, the second operating temperature profile may be no more than about 50 degrees Celsius higher than the first operating temperature profile.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] The first operating temperature profile may be between about 180 degrees Celsius and about 300 degrees Celsius during at least a portion of a first stage. The first operating temperature profile may be between about 160 degrees Celsius and about 260 degrees Celsius during at least a portion of a second stage. The second operating temperature profile may be between about 180 degrees Celsius and about 300 degrees Celsius during at least a portion of a second stage.

[0061] The susceptor arrangement may have any suitable form. The susceptor arrangement may have a unitary non-disassembly structure. The susceptor arrangement may comprise a plurality of unitary non-disassembly structures. The susceptor arrangement may be elongated. The susceptor arrangement may have any suitable transverse cross-section. For example, the susceptor arrangement may have a circular, elliptical, square, rectangular, triangular, or other polygonal transverse cross-section.

[0062] In some embodiments, the susceptor arrangement may comprise an internal heating element. As used herein, the term "internal heating element" refers to a heating element configured for insertion into the aerosol-forming substrate.

[0063] In some embodiments, the susceptor arrangement 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 generation device comprises a device cavity for receiving the aerosol-forming substrate, the internal heating element preferably extends into the device cavity.

[0064] In some embodiments, the susceptor arrangement may be an external heating element. As used herein, the term "external heating element" refers to a heating element configured to heat an 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 susceptor arrangement may be configured to heat the outer surface of the aerosol-forming substrate when the aerosol-forming substrate is received within the susceptor arrangement recess.

[0065] The susceptor arrangement may be configured to substantially surround the aerosol-forming substrate when the aerosol-forming substrate is received by the apparatus.

[0066] The susceptor arrangement may comprise a recess for receiving the aerosol-forming substrate. The susceptor arrangement may comprise an exterior and an interior opposite the exterior. The interior may at least partially define the susceptor arrangement recess for receiving the aerosol-forming substrate. The first portion of the susceptor arrangement may be tubular and define a portion of the susceptor arrangement recess. The second portion of the susceptor arrangement may be tubular and define a portion of the susceptor arrangement recess.

[0067] In some embodiments, the susceptor arrangement comprises a plurality of internal recesses for receiving the aerosol-forming substrate, the internal recesses of a first portion of the susceptor arrangement may form the first recess of the susceptor arrangement, and the internal recesses of a second portion of the susceptor arrangement may form the second recess of the susceptor arrangement.

[0068] In some preferred embodiments, the susceptor arrangement comprises a single inner recess for receiving the aerosol-forming substrate. In these embodiments, the inner recess of the first portion of the susceptor arrangement defines a portion of the single inner recess of the susceptor arrangement, and the inner recess of the second portion of the susceptor arrangement defines a second portion of the single inner recess of the susceptor arrangement. In some preferred embodiments, the susceptor arrangement is a tubular susceptor arrangement. An inner surface of the tubular susceptor arrangement may define the susceptor arrangement recess.

[0069] In embodiments in which the aerosol-generating device comprises a device cavity for receiving the aerosol-forming substrate, the susceptor arrangement may at least partially surround the device cavity. The susceptor arrangement cavity may be aligned with the device cavity.

[0070] In some embodiments, the susceptor arrangement comprises at least one internal heating element and at least one external heating element.

[0071] The susceptor arrangement comprises at least one susceptor. The susceptor arrangement may comprise a single susceptor. The susceptor arrangement may consist of a single susceptor. A first portion of the susceptor arrangement may comprise a first susceptor. A second portion of the susceptor arrangement may comprise a second susceptor.

[0072] As used herein, the term "susceptor" refers to an element that includes a material capable of converting electromagnetic energy into heat. When a susceptor is located within a changing 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.

[0073] The susceptor may comprise any suitable material. The susceptor may be formed from any material that can 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 has a thermal conductivity of greater than 1×10 at 20 degrees Celsius. -4 It refers to a material having an electrical resistivity of less than or equal to ohm-meter (Ω·m). 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 10 watts per meter per Kelvin (W / (m·K)) at 23 degrees Celsius and 50 percent relative humidity when measured using the Modified Transient Plane Source (MTPS) method.

[0074] 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 include ferromagnetic materials, such as 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 ferromagnetic or paramagnetic material.

[0075] The susceptor is preferably formed from a material that is substantially impermeable to gases, in other words, the susceptor is preferably formed from a material that is not gas permeable.

[0076] The susceptors of the susceptor arrangement may have any suitable shape. For example, the susceptors may be elongated. The susceptors may have any suitable transverse cross-section. For example, the susceptors may have a circular, elliptical, square, rectangular, triangular, or other polygonal transverse cross-section.

[0077] The first portion of the susceptor arrangement may be a tubular susceptor. The second portion of the susceptor arrangement may be a tubular susceptor. The tubular susceptor includes an annular body defining an inner 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.

[0078] 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 changing magnetic field.

[0079] 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.

[0080] 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.

[0081] In another example, the 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.

[0082] 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.

[0083] The susceptor arrangement may comprise any suitable number of susceptors. The susceptor arrangement may comprise a plurality of susceptors. The susceptor arrangement may comprise at least two susceptors. For example, the susceptor arrangement may comprise three, four, five, or six susceptors. When the susceptor arrangement comprises three or more susceptors, an intermediate element may be disposed between each pair of adjacent susceptors.

[0084] In some preferred embodiments, the susceptor may comprise a susceptor layer provided on a support body. 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 body and a susceptor layer. Disposing the susceptor in a changing magnetic field induces eddy currents in close proximity to the susceptor surface, an effect called the skin effect. As a result, it is possible to form the susceptor from a relatively thin layer of susceptor material while ensuring that the susceptor is effectively heated in the presence of a changing magnetic field. Making the susceptor from a support body and a relatively thin susceptor layer may facilitate the manufacture of a simple, inexpensive, and robust aerosol-generating article.

[0085] The support body may be formed from a material that is not susceptible to inductive heating, which may advantageously reduce heating of the surface of the susceptor that is not in contact with the aerosol-forming substrate, where the surface of the support body forms the surface of the susceptor that is not in contact with the aerosol-forming substrate.

[0086] The support body may comprise an electrically insulating material. As used herein, "electrically insulating" means having a thermal conductivity of at least 1×10 at 20 degrees Celsius. 4 Refers to a material that has an electrical resistivity in ohmmeters (Ω·m).

[0087] The support body may be thermally insulating. As used herein, the term "thermal insulating material" is used to describe a material that has a bulk thermal conductivity of about 40 watts per meter per Kelvin (W / (m·K)) or less at 23 degrees Celsius and 50 percent relative humidity when measured using the Modified Transient Plane Source (MTPS) method.

[0088] Forming the support body from an insulating material may provide an insulating barrier between the susceptor layer and other components of the induction heating arrangement, such as the inductor coil surrounding the susceptor arrangement. Advantageously, this may reduce heat transfer between the susceptor and other components of the induction heating system.

[0089] The support body may be a tubular support body and the susceptor layer may be provided on an inner surface of the tubular support body. Providing the susceptor layer on the inner surface of the support body may position the susceptor layer adjacent to the aerosol-forming substrate within a recess of the susceptor arrangement, improving heat transfer between the susceptor layer and the aerosol-forming substrate.

[0090] In some preferred embodiments having a first susceptor and a second susceptor, the first susceptor comprises a tubular support body formed from an insulating material and a susceptor layer on an inner surface of the tubular support body, hi some preferred embodiments, the second susceptor comprises a tubular support body formed from an insulating material and a susceptor layer on an inner surface of the tubular support body.

[0091] The susceptor may be provided with a protective outer layer, for example a protective ceramic or 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.

[0092] The susceptor arrangement may include a separation between the first portion of the susceptor arrangement and the second portion of the susceptor arrangement.

[0093] The separator may be of any suitable size for insulating a first portion of the susceptor arrangement from a second portion of the susceptor arrangement.

[0094] The susceptor arrangement may include an intermediate element disposed between a first portion of the susceptor arrangement and a second portion of the susceptor arrangement. The intermediate element may be disposed in a separation between the first portion of the susceptor arrangement and the second portion of the susceptor arrangement. The intermediate element may extend between the first portion of the susceptor arrangement and the second portion of the susceptor arrangement. The intermediate element may contact an end of the first portion of the susceptor arrangement. The intermediate element may contact an end of the second portion of the susceptor arrangement. The intermediate element may be fixed to an end of the first portion of the susceptor arrangement. The intermediate element may be fixed to an end of the second portion of the susceptor arrangement. The intermediate element may connect the second portion of the susceptor arrangement to the first portion of the susceptor arrangement. When the intermediate element connects the second portion of the susceptor arrangement to the first portion of the susceptor arrangement, the intermediate element may provide structural support to the susceptor arrangement. Advantageously, the intermediate element may enable the susceptor arrangement to be provided as a single, non-disassembly element that may be simple to remove and replace from the induction heating arrangement.

[0095] The intermediate element may have any suitable shape. The intermediate element may have any suitable transverse cross-section. For example, the intermediate element may have a circular, elliptical, square, rectangular, triangular, or other polygonal transverse cross-section. The intermediate element may be tubular. A tubular intermediate element comprises an annular body defining an inner cavity. The intermediate element may be configured to allow gas to permeate from the exterior of the intermediate element into the inner 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.

[0096] In some preferred embodiments, the first portion of the susceptor arrangement and the second portion of the susceptor arrangement 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 arranged end-to-end in the form of a tubular rod. The inner recesses of the tubular first susceptor, the tubular intermediate element, and the tubular second susceptor may be substantially aligned. The inner recesses of the tubular first susceptor, the tubular intermediate element, and the tubular second susceptor may define a recess of the susceptor arrangement.

[0097] The intermediate element may be formed from any suitable material.

[0098] In a preferred embodiment, the intermediate element is formed from a different material than the first portion of the susceptor arrangement and the second portion of the susceptor arrangement.

[0099] The intermediate element may include a thermal insulating material for insulating the first portion of the susceptor arrangement from the second portion of the susceptor arrangement. The intermediate element may include a material having a bulk thermal conductivity of about 100 milliwatts per meter per Kelvin (mW / (m·K)) or less at 23 degrees Celsius and 50 percent relative humidity as measured using a modified transient planar heat source (MTPS) method. Providing an intermediate element formed from a thermal insulating material at a separation between the first portion of the susceptor arrangement and the second portion of the susceptor arrangement may further reduce heat transfer between the first portion of the susceptor arrangement and the second portion of the susceptor arrangement. Advantageously, this may improve the ability of the susceptor arrangement to selectively heat individual 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 susceptor arrangement and the second portion of the susceptor arrangement, and consequently, the size of the susceptor arrangement.

[0100] The intermediate element may include an electrically insulating material for electrically insulating the first portion of the susceptor arrangement from the second portion of the susceptor arrangement. The susceptor has a thermal conductivity of at least 1×10 4 It may include materials having electrical resistivity in ohm-meters (Ωm).

[0101] The intermediate element may include at least one of a thermal insulation material for insulating a first portion of the susceptor arrangement from a second portion of the susceptor arrangement and an electrically insulating material for electrically insulating the first portion of the susceptor arrangement from the second portion of the susceptor arrangement. In some preferred embodiments, the intermediate element includes a thermal insulation material for insulating the first portion of the susceptor arrangement from the second portion of the susceptor arrangement and an electrically insulating material for electrically insulating the first portion of the susceptor arrangement from the second portion of the susceptor arrangement.

[0102] Particularly suitable materials for the intermediate element may 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).

[0103] 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 comprise 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.

[0104] 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 need not be formed from a gas permeable material. As a result, 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.

[0105] If the intermediate element is a tubular intermediate element defining an internal recess, 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 recess. 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.

[0106] The first inductor coil is configured such that a varying current supplied to the first inductor coil generates a varying magnetic field, and the first inductor coil is disposed relative to the susceptor arrangement such that a varying current supplied to the first inductor coil generates a varying magnetic field that heats a first portion of the susceptor arrangement.

[0107] The second inductor coil is configured such that a varying current supplied to the second inductor coil generates a varying magnetic field, and the second inductor coil is disposed relative to the susceptor arrangement such that a varying current supplied to the second inductor coil generates a varying magnetic field that heats a second portion of the susceptor arrangement.

[0108] 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 wound in a spiral, substantially planar manner. The inductor coil is preferably a tubular inductor coil defining an internal recess. Typically, the tubular inductor coil is wound in a spiral manner 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 transverse cross-section. For example, the inductor coil may have a circular, elliptical, square, rectangular, triangular, or other polygonal transverse cross-section.

[0109] 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.

[0110] When the inductor coil is a tubular inductor coil, a portion of the susceptor arrangement is preferably disposed within the inner recess of the inductor coil. It is particularly preferred that the first inductor coil is a tubular inductor coil, and at least a portion of the first portion of the susceptor arrangement is disposed within the inner recess 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 susceptor arrangement. It is particularly preferred that the second inductor coil is a tubular inductor coil, and at least a portion of the second portion of the susceptor arrangement is disposed within the inner recess 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 susceptor arrangement.

[0111] 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. In embodiments where the second portion of the susceptor arrangement is substantially identical to the first portion of the susceptor arrangement, it is particularly preferred that the second inductor coil is substantially identical to the first inductor coil.

[0112] 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-sectional area than the first inductor coil. In embodiments in which the second portion of the susceptor arrangement is different from the first portion of the susceptor arrangement, it is particularly preferred that the second inductor coil is different from the first inductor coil.

[0113] The first and second inductor coils may be arranged in any suitable arrangement. It is particularly preferred that the first and second inductor coils are coaxially aligned along the axis. When 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 inner recesses of the coils are aligned along the longitudinal axis.

[0114] 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.

[0115] The induction heating arrangement may comprise any suitable number of inductor coils. The susceptor arrangement comprises a plurality of inductor coils. The induction heating arrangement comprises at least two inductor coils. The number of inductor coils in the induction heating arrangement is preferably the same as the number of susceptors in the susceptor arrangement. The number of inductor coils in the induction heating arrangement may be different from the number of susceptors in the susceptor arrangement. If the number of inductor coils is the same as the number of susceptors, each inductor coil is preferably disposed around a susceptor. It is particularly preferred that each inductor coil extends substantially the length of the susceptor around which it is disposed.

[0116] The susceptor arrangement may include a magnetic flux concentrator disposed about an inductor coil of the induction heating arrangement, the magnetic flux concentrator configured to distort a changing magnetic field generated by the inductor coil toward the susceptor arrangement.

[0117] Advantageously, by distorting the magnetic field towards the susceptor arrangement, the magnetic flux concentrator can focus the magnetic field at the susceptor arrangement, which may 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 distorting the magnetic field such that the magnetic energy density of the magnetic field is increased where the magnetic field is "concentrated."

[0118] 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, "μ0", where μ0 is 4π×10 -7 Newton per square ampere (N A -2 ).

[0119] 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.

[0120] 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).

[0121] In some embodiments, the induction heating arrangement includes a magnetic flux concentrator disposed about the first inductor coil and the second inductor coil, in these embodiments, the magnetic flux concentrator is configured to distort a changing magnetic field generated by the first inductor coil toward a first portion of the susceptor arrangement and to distort a changing magnetic field generated by the second inductor coil toward a second portion of the susceptor arrangement.

[0122] In some of these embodiments, a portion of the magnetic flux concentrator extends into an intermediate element between the first portion of the susceptor arrangement and the second portion of the susceptor arrangement. Extending a portion of the magnetic flux concentrator into an intermediate element between the first portion of the susceptor arrangement and the second portion of the susceptor arrangement may further distort the magnetic field generated by the first inductor coil and the magnetic field generated by the second inductor coil. This further distortion may cause the magnetic field generated by the first inductor coil to be further concentrated toward the first portion of the susceptor arrangement and the magnetic field generated by the second inductor coil to be further concentrated toward the second portion of the susceptor arrangement. This may further improve the efficiency of the induction heating arrangement.

[0123] In some embodiments, the induction heating arrangement comprises multiple magnetic flux concentrators. In some preferred embodiments, a separate magnetic flux concentrator is disposed around each inductor coil. Providing a dedicated magnetic flux concentrator for each inductor coil 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 a modular induction heating unit may facilitate standardized manufacturing of the induction heating arrangement and allow removal and replacement of individual units.

[0124] In some preferred embodiments, the induction heating arrangement comprises a first magnetic flux concentrator disposed about the first inductor coil, the first magnetic flux concentrator configured to distort a changing magnetic field generated by the first inductor coil toward a first portion of the susceptor arrangement, and a second magnetic flux concentrator disposed about the second inductor coil, the second magnetic flux concentrator configured to distort a changing magnetic field generated by the second inductor coil toward a second portion of the susceptor arrangement.

[0125] In these preferred embodiments, a portion of the first magnetic flux concentrator may extend into an intermediate element between the first portion of the susceptor arrangement and the second portion of the susceptor arrangement. In these preferred embodiments, a portion of the second magnetic flux concentrator may extend into an intermediate element between the first portion of the susceptor arrangement and the second portion of the susceptor arrangement. Extending a portion of the magnetic flux concentrator into the intermediate element between the susceptors may allow the magnetic flux concentrator to further distort the magnetic field generated by the inductor coil toward the susceptors.

[0126] The induction heating arrangement may further comprise an induction heating arrangement housing. The housing may hold the susceptor arrangement, the inductor coil, and the magnetic flux concentrator together. This may serve to fix the relative arrangement of the components of the induction heating arrangement and improve the coupling between the components. The induction heating arrangement housing is preferably formed from an electrically insulating material.

[0127] 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 holds the components of the induction heating unit together and may improve coupling between the components. The induction heating unit housing is preferably formed from an electrically insulating material.

[0128] 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 rechargeable 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).

[0129] 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 continuously supplied to the induction heating arrangement after activation of the aerosol generating device, or may be intermittently supplied (such as after every puff).

[0130] The aerosol generating device may advantageously comprise a DC / AC inverter, which may comprise 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.

[0131] The aerosol generating device may further include a DC / DC converter between the power supply and the DC / AC converter.

[0132] 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 alternating pulse width modulated signal 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 alternating pulse width modulated signal in the second inductor coil when the first switch remains off.

[0133] The controller may be configured to provide an alternating pulse-width modulated signal having any suitable frequency to the induction heating arrangement. The controller may be configured to provide an alternating pulse-width modulated signal having a frequency of about 5 kilohertz to about 30 megahertz to the induction heating arrangement. In some preferred embodiments, the controller is configured to provide an alternating pulse-width modulated signal to the induction heating arrangement of about 5 kilohertz to about 500 kilohertz. In some embodiments, the controller is configured to provide a high frequency alternating pulse-width modulated signal to the induction heating arrangement. As used herein, the term "high frequency alternating pulse-width modulated signal" refers to an alternating pulse-width modulated signal having a frequency of about 500 kilohertz to about 30 megahertz. The high frequency alternating pulse-width modulated signal 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).

[0134] 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.

[0135] 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 transverse cross-section.

[0136] The susceptor arrangement may be disposed within the device cavity. The susceptor arrangement may be disposed around the device cavity. If the susceptor arrangement is a tubular susceptor arrangement, the susceptor arrangement may surround the device cavity. An inner surface of the susceptor arrangement may form an inner surface of the device cavity.

[0137] 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.

[0138] The device may have a proximal end and a distal end opposite the proximal end. The device recess is preferably disposed in the proximal end of the device.

[0139] 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 the aerosol-generating article.

[0140] In some embodiments, the aerosol generating device further comprises a movable cover outside the proximal end of the device cavity to prevent insertion of an aerosol-generating article into the device cavity.

[0141] 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 into the first inductor coil and thereafter driving a second varying current into the second inductor coil. Such action heats a proximal portion of the device cavity before heating a distal portion of the device cavity.

[0142] 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.

[0143] 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.

[0144] If the intermediate element of the susceptor arrangement is gas permeable, the aerosol-generating device may define an airflow path extending from the air inlet to the intermediate element of the susceptor arrangement. 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.

[0145] In some embodiments, the device cavity comprises a proximal end and a distal end opposite the proximal end. In these embodiments, the device cavity may be open at the proximal end to receive the aerosol-generating article. In these embodiments, the device cavity may be substantially closed at the distal end. The device housing may comprise 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 in the device cavity. This may reduce the volume of air drawn into the device cavity through any gaps that exist between the outer surface of the aerosol-generating article and the inner surface of the device cavity in use. This may increase the volume of air drawn into the aerosol-generating article through the permeable intermediate element.

[0146] In some embodiments, the device housing comprises a mouthpiece. The mouthpiece may comprise at least one air inlet and at least one air outlet. The mouthpiece may comprise two or more air inlets. One or more of the air inlets may reduce the temperature of the aerosol before it is delivered to the user and may reduce the concentration of the aerosol before it is delivered to the user.

[0147] In some embodiments, a mouthpiece is provided as part of the aerosol-generating article. As used herein, the term "mouthpiece" refers to a portion of an aerosol-generating system that is placed into a user's mouth to directly inhale aerosol generated by the aerosol-generating system from an aerosol-generating article received by the aerosol-generating device.

[0148] 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 susceptor arrangement based on the monitored current. The controller may be configured to monitor a first changing current and determine a temperature of a first portion of the susceptor arrangement based on the monitored first changing current. The controller may be configured to monitor a second changing current and determine a temperature of a second portion of the susceptor arrangement based on the monitored second changing current.

[0149] The aerosol generating device may include a temperature sensor. The temperature sensor may be arranged to sense a temperature of the susceptor arrangement. The controller may be configured to control the first varying current based on the temperature of the susceptor arrangement sensed by the temperature sensor. The controller may be configured to control the second varying current based on the temperature of the susceptor arrangement sensed by the temperature sensor.

[0150] 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.

[0151] In some preferred embodiments, the aerosol generating apparatus may include a first temperature sensor arranged to sense a temperature of the first portion of the susceptor arrangement, 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 susceptor arrangement sensed by the first temperature sensor.

[0152] In some preferred embodiments, the aerosol generating apparatus may include a second temperature sensor arranged to sense a temperature of the second portion of the susceptor arrangement, 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 susceptor arrangement sensed by the second temperature sensor.

[0153] 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.

[0154] The aerosol generating device may be equipped with a display to indicate the status of the device or the aerosol-forming substrate.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] The aerosol-forming substrate detector and the aerosol-generating article detector may comprise any suitable type of detector, for example the detector may be an optical detector, an acoustic detector, a capacitive detector, or an inductive detector.

[0159] 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.

[0160] 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.

[0161] The aerosol generating device may form part of an aerosol generating system.

[0162] The aerosol-generating system may further comprise an aerosol-generating article. The aerosol-generating article may comprise an aerosol-forming substrate. 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.

[0163] A susceptor arrangement, which forms part of the induction heating arrangement of the aerosol-generating device, is configured to heat the aerosol-forming substrate.

[0164] The aerosol-forming substrate may comprise nicotine. The nicotine-containing aerosol-forming substrate may be a nicotine salt matrix.

[0165] 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.

[0166] 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 that 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" means a sheet having a plurality of substantially parallel ridges or corrugations.

[0167] 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 and stable aerosol in 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), 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 (such as 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.

[0168] 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.

[0169] 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.

[0170] 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 susceptor arrangement, and similarly, the number of aerosol-forming substrates may be the same as the number of inductor coils in the induction heating arrangement.

[0171] The aerosol-generation segment may be substantially cylindrical in shape. 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.

[0172] Where the aerosol-generation segment comprises multiple aerosol-forming substrates, 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.

[0173] 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 may have 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.

[0174] 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 about 12 millimeters.

[0175] 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.

[0176] 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.

[0177] The first part of the susceptor arrangement may be arranged to heat a first part of the aerosol-forming substrate. The first part of the susceptor arrangement may be arranged to substantially surround the first part of the aerosol-forming substrate. The second part of the susceptor arrangement may be arranged to heat a second part of the aerosol-forming substrate. The second part of the susceptor arrangement may be arranged to substantially surround the second part of the aerosol-forming substrate.

[0178] The aerosol-generating article may comprise an outer wrapper. The outer wrapper may be formed from paper. The outer wrapper may be gas permeable in the aerosol-generating segment. In particular, in embodiments comprising a plurality of aerosol-forming substrates, the outer wrapper may comprise perforations or other air inlets at the interface between adjacent aerosol-forming substrates. When a separation is provided between adjacent aerosol-forming substrates, the outer wrapper may comprise 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.

[0179] 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 be in the range of about 5 millimeters to about 25 meters.

[0180] It will also be appreciated that particular combinations of the various features described above may be implemented, provided and used independently.

[0181] 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]

[0182] [Figure 1] FIG. 1 shows a schematic diagram of a susceptor arrangement according to an embodiment of the present disclosure disposed between a pair of inductor coils. [Diagram 2] FIG. 2 shows a schematic diagram of a susceptor arrangement according to an embodiment of the present disclosure disposed between a pair of inductor coils. [Diagram 3] FIG. 3 illustrates an exploded perspective view of a susceptor arrangement according to an embodiment of the present disclosure. [Figure 4] FIG. 4 shows a perspective view of the susceptor arrangement of FIG. [Diagram 5] FIG. 5 shows a cross-sectional view of an aerosol generation system according to an embodiment of the present disclosure, 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 with an aerosol-generating article received within the aerosol generating device. [Figure 8] FIG. 8 shows a schematic diagram of a susceptor arrangement according to an embodiment of the present disclosure disposed between a pair of inductor coils. [Figure 9] FIG. 9 shows a cross-sectional view of an aerosol generation system according to another embodiment of the present disclosure, comprising an aerosol generating article and an aerosol generating device having an inductive heating arrangement. [Figure 10] FIG. 10 shows a graph of temperature over time for the susceptor arrangement of FIG. [Figure 11] FIG. 11 shows an exemplary circuit for an induction heating arrangement. [Figure 12] FIG. 12 illustrates an exemplary circuit for controlling an induction heating arrangement. [Figure 13] FIG. 13 shows a diagram of a pulse width modulated signal for driving an induction heating arrangement.

[0183] 1 shows a schematic diagram of a susceptor arrangement 10 according to an embodiment of the present disclosure. The susceptor arrangement 10 is an elongated tubular element having a circular transverse cross section. The susceptor arrangement 10 comprises 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 transverse cross section. The first susceptor 12 and the second susceptor 14 are coaxially aligned end-to-end along a longitudinal axis AA.

[0184] The susceptor arrangement 10 comprises a cylindrical recess 20 that is open at both ends and is defined by the inner surfaces of the first susceptor 12 and the second susceptor 14. The recess 20 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 may be heated by the first susceptor and the second susceptor, thereby heating the aerosol-forming substrate.

[0185] The cavity 20 comprises three portions: a first portion 22 defined by the inner surface of the tubular first susceptor 12 at a first end, a second portion 24 defined by the inner surface of the tubular second susceptor 14 at a second end 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.

[0186] The first inductor coil 32 is disposed around 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 (preferably an AC current) is supplied to the first inductor coil 32, the first inductor coil 32 generates a varying magnetic field that is concentrated in the first portion 22 of the recess 20. This 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.

[0187] 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 (preferably an AC current) is supplied to the second inductor coil 34, the second inductor coil 34 generates a varying magnetic field that is concentrated in the second portion 24 of the recess 20. This 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.

[0188] 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 inductively heated when exposed to the changing 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, thereby reducing the rate of heat transfer between the first susceptor 12 and the second susceptor 14 compared to a susceptor arrangement 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 enables selective heating of the first portion 22 of the recess 20 by the first susceptor 12 while minimizing heating of the second portion 24 of the recess 20, and also enables selective heating of the second portion 24 of the recess 20 by the second susceptor 14 while minimizing heating of the first portion 22 of the recess 20.

[0189] The first susceptor 12 and the second susceptor 14 may be heated simultaneously by simultaneously supplying a varying current (preferably an AC 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 (preferably an AC current) to the first inductor coil 32 without supplying a current to the second inductor coil 34, and then supplying a varying current (preferably an AC 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 (preferably an AC current) may be supplied to the first inductor coil 32 and the second inductor coil 34 in sequence.

[0190] Figure 2 shows a schematic diagram of a susceptor arrangement according to another embodiment of the present disclosure. The susceptor arrangement shown in Figure 2 is substantially identical to the susceptor apparatus shown in Figure 1, and like reference numbers are used to describe like features.

[0191] The susceptor arrangement 10 of Fig. 2 is an elongated tubular element having a circular transverse cross section. The susceptor arrangement 10 comprises a first susceptor 12 and a second susceptor 14. The difference between the susceptor arrangement 10 of Fig. 1 and the susceptor arrangement 10 of Fig. 2 is that the susceptor arrangement 10 of Fig. 2 comprises 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 also to an end of the second susceptor 14. Securing the intermediate element 16 to an end of the first susceptor 12 and securing the intermediate element 16 to an end of the second susceptor 14 indirectly connects the first susceptor 12 to the second susceptor 14. Advantageously, indirectly securing the first susceptor 12 to the second susceptor 14 allows the susceptor arrangement to form a unitary structure that cannot be disassembled.

[0192] The intermediate element 16 includes a thermal insulating material. The thermal 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 changing 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, thereby reducing the rate of heat transfer between the first susceptor 12 and the second susceptor 14 compared to a susceptor arrangement in which the first susceptor and the second susceptor 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 separating portion 15 of the susceptor arrangement 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 with minimal heating of the second portion 24 of the cavity 20, and also allows for selective heating of the second portion 24 of the cavity 20 by the second susceptor 14 with minimal heating of the first portion 22 of the cavity 20.

[0193] 3 to 7 show schematic diagrams of an aerosol generation system according to an embodiment of the present disclosure. The aerosol generation system comprises an aerosol generation device 100 and an aerosol-generating article 200. The aerosol generation device 100 comprises an induction heating arrangement 110 according to the present disclosure. The induction heating arrangement 110 comprises a susceptor arrangement 120 according to the present disclosure.

[0194] 3 and 4 show schematic diagrams of a susceptor arrangement 120. The susceptor arrangement 120 comprises 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.

[0195] 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 inner recess. Each susceptor, and its corresponding inner recess, is substantially cylindrical and has a circular transverse cross-section that is constant along the length of the susceptor. The inner recess of the first susceptor 122 defines a first region 134. The inner recess of the second susceptor 124 defines a second region 136. The inner recess of the third susceptor defines a third region 138.

[0196] Similarly, the first intermediate element 128 and the second intermediate element 130 are identical. The intermediate elements 128, 130 are tubular and define an inner recess. 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 identical to the outer diameter of the susceptors 122, 124, 126 such that the outer surfaces of the intermediate elements 128, 130 may be aligned flush with the outer surfaces of the susceptors 122, 124, 126. The inner diameter of the intermediate elements 128, 130 is also identical to the inner diameter of the susceptors 122, 124, 126 such that the inner surfaces of the intermediate elements 128, 138 may be aligned flush with the inner surfaces of the susceptors 122, 124, 126.

[0197] 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 susceptor arrangement 120 according to one embodiment of the present disclosure.

[0198] The elongated tubular susceptor arrangement 120 includes an internal recess 140. The susceptor arrangement recess 140 is defined by the internal recesses of the susceptors 122, 124, 126 and the internal recesses of the intermediate elements 128, 130. The susceptor arrangement recess 140 is configured to receive an aerosol-generating segment of the aerosol-generating article 200, as described in more detail below.

[0199] The intermediate elements 128, 130 are formed from an electrically insulating and thermally insulating material. In this manner, 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 susceptor arrangement 120 is substantially impermeable to gas from its outer surface to the inner surface defining the susceptor arrangement recess 140.

[0200] 5, 6 and 7 show schematic cross-sectional views of an aerosol generating device 100 and an aerosol-generating article 200.

[0201] 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 an opposite distal end. The device cavity 104 is configured to receive the aerosol-generating segment 210 of the aerosol-generating article 200. As a result, 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.

[0202] 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.

[0203] The controller 108 is configured to control the supply of power from the power source 106 to the induction heating device 110. The controller 108 further comprises a DC / AC inverter including a class D power amplifier and is configured to supply a varying current (preferably an AC current) to the induction heating arrangement 110. Additionally or alternatively, the DC / AC inverter may include at least one of a class C and a class E power amplifier. The controller 108 is also configured to control the recharging of the power source 106 from the electrical connector 109. In addition, the controller 108 comprises a puff sensor (not shown) configured to sense when a user puffs on an aerosol-generating article received in the device cavity 104.

[0204] 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.

[0205] The first induction heating unit 112 comprises a cylindrical tubular first inductor coil 150, a cylindrical tubular first magnetic flux concentrator 152 arranged around the first inductor coil 150, and a cylindrical tubular first inductor unit housing 154 arranged around the first magnetic flux concentrator 152.

[0206] The second induction heating unit 114 includes a cylindrically tubular second inductor coil 160, a cylindrically tubular second magnetic flux concentrator 162 disposed around the second inductor coil 160, and a cylindrically tubular second inductor unit housing 164 disposed around the second magnetic flux concentrator 162.

[0207] The third induction heating unit 116 includes a cylindrically tubular third inductor coil 170, a cylindrically tubular third magnetic flux concentrator 172 disposed around the third inductor coil 170, and a cylindrically tubular third inductor unit housing 174 disposed around the third magnetic flux concentrator 172.

[0208] As a result, each induction heating unit 112, 114, 116 forms a substantially tubular unit having a circular transverse cross section. In each induction heating unit 112, 114, 116, the magnetic flux concentrator extends over the proximal and distal ends of the inductor coil such that the inductor coil is disposed within an annular recess of the magnetic flux concentrator. Similarly, each induction heating unit housing extends over the proximal and distal ends of the magnetic flux concentrator such that the magnetic flux concentrator and the inductor coil are disposed within an annular recess of the induction heating unit housing. This arrangement allows the magnetic flux concentrator to concentrate the magnetic field generated by the inductor coil within the inner recess of the inductor coil. This arrangement also allows the inductor unit housing to retain the magnetic flux concentrator and the inductor coil within the inductor unit housing.

[0209] The induction heating arrangement 110 further comprises a susceptor arrangement 120. The susceptor arrangement 120 is disposed about an inner surface of the device cavity 104. In this embodiment, the device housing 102 defines the inner surface of the device cavity 104. However, it is contemplated that in some embodiments, the inner surface of the device cavity is defined by the inner surface of the susceptor arrangement 120.

[0210] The induction heating units 112, 114, 116 are disposed about the susceptor arrangement 120 such that the susceptor arrangement 120 and the induction heating units 112, 114, 116 are disposed concentrically about the device well 104. The first induction heating unit 112 is disposed about the first susceptor 122 at a distal end of the device well 104. The second induction heating unit 114 is disposed about the second susceptor 124 at a central portion of the device well 104. The third induction heating unit 116 is disposed about the third susceptor 126 at a proximal end of the device well 104. It is contemplated that in some embodiments, the magnetic flux concentrator may also extend into an intermediate element of the susceptor arrangement to further distort the magnetic field generated by the inductor coil toward the susceptor.

[0211] The first inductor coil 150 is connected to the controller 108 and the power supply 106, and the controller 108 is configured to supply a varying current (preferably an AC current) to the first inductor coil 150. When a varying current (preferably an AC current) is supplied to the first inductor coil 150, the first inductor coil 150 generates a changing magnetic field, which heats the first susceptor 122 by induction.

[0212] 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 (preferably an AC current) to the second inductor coil 160. When a varying current (preferably an AC current) is supplied to the second inductor coil 160, the second inductor coil 160 generates a changing magnetic field, which heats the second susceptor 124 by induction.

[0213] 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 (preferably an AC current) to the third inductor coil 170. When a varying current (preferably an AC 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.

[0214] The device housing 102 also defines an air inlet 180 in close proximity to the distal end of the device well 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 well 104 to allow air to be drawn from the air inlet 180 into the device well 104.

[0215] 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 by an outer wrapper 220 of cigarette paper.

[0216] 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.

[0217] 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, and 216 are different. The first aerosol-forming substrate 212 comprises a gathered and crimped sheet of homogenized tobacco material without additional flavorants. The second aerosol-forming substrate 214 comprises an aggregated and crimped sheet of homogenized tobacco material containing a flavorant in the form of menthol. The third aerosol-forming substrate contains 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 of the aerosol-forming substrate produces an aerosol having desirable organoleptic properties.

[0218] 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.

[0219] In this embodiment, the first aerosol-forming substrate 212, the second aerosol-forming substrate 214 and the third aerosol-forming substrate 216 are arranged end-to-end. However, it is envisaged that in other embodiments a separation may be provided between the first aerosol-forming substrate and the second aerosol-forming substrate and a separation may be provided between the second aerosol-forming substrate and the third aerosol-forming substrate.

[0220] 7, when the aerosol-generating segment 210 of the aerosol-generating article 200 is received in 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.

[0221] In use, when the aerosol-generating article 200 is received in the device cavity 104, a user may suck on the proximal end of the aerosol-generating article 200 to inhale the aerosol generated by the aerosol generation system. When a user sucks on the proximal end of the aerosol-generating article 200, air is drawn into the device housing 102 at the air inlet 180 and along the airflow path 181 into the device cavity 104. Air is drawn through an outlet at the distal end of the device cavity 104 and into the aerosol-generating article 200 at the proximal end of the first aerosol-forming substrate 212.

[0222] 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 device 110 in a predetermined sequence. The predetermined sequence includes supplying a varying current (preferably AC current) to the first inductor coil 150 during a first inhalation from the user, then supplying a varying current (preferably AC current) to the second inductor coil 160 during a second inhalation from the user after the first inhalation is completed, and then supplying a varying current (preferably AC current) to the third inductor coil 170 during a third inhalation from the user after the second inhalation is completed. In the fourth inhalation, the sequence starts again with the first inductor coil 150. This sequence results in heating of the first aerosol-forming substrate 212 in the first inhalation, heating of the second aerosol-forming substrate 214 in the second inhalation, and heating of the third aerosol-forming substrate 216 in the third inhalation. Because the aerosol-forming substrates 212, 214, 216 of the article 100 are all different, this sequence creates a different experience for the user with each puff of the aerosol generating system.

[0223] 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.

[0224] 8 shows a schematic diagram of a susceptor arrangement 310 according to an embodiment of the present disclosure. The susceptor arrangement 310 is an elongated tubular element having a circular transverse cross-section. The susceptor arrangement 310 comprises 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 transverse cross-section. The first portion 312 and the second portion 314 are coaxially aligned end-to-end along a longitudinal axis AA.

[0225] The susceptor arrangement 310 comprises a cylindrical recess 320 that is open at both ends and defined by the inner surfaces of a first portion 312 and a second portion 314. The recess 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 may be heated by the first and second susceptors, thereby heating the aerosol-forming substrate.

[0226] The recess 320 is configured to receive a portion of an aerosol-generating article that comprises an aerosol-forming substrate.

[0227] The recess 320 comprises two portions: a first portion 322 at a first end defined by an inner surface of the first portion 312 of the susceptor arrangement 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 susceptor arrangement 310. The first portion 312 of the susceptor arrangement 310 is arranged to heat a first portion of an aerosol-generating article received in the first portion 322 of the recess 320, and the second portion 314 of the susceptor arrangement 310 is arranged to heat a second portion of an aerosol-generating article received in the second portion 324 of the recess 320.

[0228] The first inductor coil 332 is disposed around and extends substantially the length of the first portion 312 of the susceptor arrangement 310. Thus, the first portion 312 of the susceptor arrangement 310 is surrounded by the first inductor coil 332 substantially along its length. When a varying current (preferably an AC 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 recess 320. The varying magnetic field generated by the first inductor coil 332 induces eddy currents in the first portion 312 of the susceptor arrangement 310, causing the first portion 312 of the susceptor arrangement 310 to heat.

[0229] The second inductor coil 334 is disposed around the second portion 314 of the susceptor arrangement 310 and extends substantially the length of the second portion 314 of the susceptor arrangement 310. Thus, the second portion 314 of the susceptor arrangement 310 is surrounded by the second inductor coil 334 of the susceptor arrangement 310 substantially along its length. When a varying current (preferably an AC 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 recess 320. The varying magnetic field generated by the second inductor coil 334 induces eddy currents in the second portion 314 of the susceptor arrangement 310, causing the second susceptor 314 to heat.

[0230] The first portion 312 of the susceptor arrangement 310 and the second portion 314 of the susceptor arrangement 310 may be heated simultaneously by simultaneously supplying a varying current (preferably an AC current) to the first inductor coil 332 and the second inductor coil 334. Alternatively, the first portion 312 of the susceptor arrangement 310 and the second portion 314 of the susceptor arrangement 310 may be heated independently or alternately by supplying a varying current (preferably an AC current) to the first inductor coil 332 without supplying a current to the second inductor coil 334, and then supplying a varying current (preferably an AC 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 (preferably an AC current) may be supplied to the first inductor coil 332 and the second inductor coil 334 in sequence.

[0231] Temperature sensors in the form of thermocouples are also provided on the outer surface of the susceptor arrangement 310. A first thermocouple 342 is provided on the outer surface of the first portion 312 of the susceptor arrangement 310 to sense the temperature of the first portion 312 of the susceptor arrangement 310. A second thermocouple 344 is provided on the outer surface of the second portion 314 of the susceptor arrangement 310 to sense the temperature of the second portion 314 of the susceptor arrangement 310.

[0232] Figure 9 shows a cross-sectional view of an aerosol generation system 600 according to another embodiment of the present disclosure. The aerosol generation system 600 comprises an aerosol generation device 602 comprising the susceptor arrangement 310 of Figure 8, the first inductor coil 332 and the second inductor coil 334. The aerosol generation device 602 is similar to the aerosol generation device 100 of Figure 5, and like reference numbers are used to designate like parts.

[0233] The aerosol-generating system 600 also includes an aerosol-generating article 700. The aerosol-generating article 700 includes an aerosol-forming substrate 702 in the form of a cylindrical rod and including tobacco strands made from homogenized tobacco and an aerosol former. The cylindrical rod of the aerosol-forming substrate 702 has a length substantially equal to the length of the device cavity 104. The aerosol-generating article 700 also includes a tubular cooling segment 704, a filter segment 706, and an oral end segment 708. The aerosol-forming substrate 702, the tubular cooling segment 704, the filter segment 706, and the oral end segment 708 are held together by an outer wrapper 710.

[0234] In one embodiment, the aerosol-forming substrate 702 is between 34 millimeters and 50 millimeters long, more preferably, the aerosol-forming substrate 702 is between 38 millimeters and 46 millimeters long, and more preferably still, the aerosol-forming substrate 702 is 42 millimeters long.

[0235] In one embodiment, the overall length of article 700 is between 71 millimeters and 95 millimeters, more preferably, the overall length of article 700 is between 79 millimeters and 87 millimeters, and more preferably still, the overall length of article 700 is 83 millimeters.

[0236] In one embodiment, the cooling segment 704 is an annular tube and defines a gap therein. The gap provides a chamber for the flow of heated volatilized components produced from the aerosol-forming substrate 702. The cooling segment 704 is hollow, providing a chamber for aerosol accumulation, yet is rigid enough to withstand axial compressive forces and bending moments that may occur during manufacturing and while the article 700 is inserted into the aerosol generating device 602 in use. In one embodiment, the wall thickness of the cooling segment 704 is approximately 0.29 millimeters.

[0237] The cooling segment 704 provides a physical displacement between the aerosol-forming substrate 702 and the filter segment 706. The physical displacement provided by the cooling segment 704 provides a thermal gradient across the length of the cooling segment 704 during use. In one embodiment, the cooling segment 704 is configured to provide a temperature difference of at least 40 degrees Celsius between the heated volatilized components entering the distal end of the cooling segment 704 and the heated volatilized components exiting the proximal end of the cooling segment 704. In one embodiment, the cooling segment 704 is configured to provide a temperature difference of at least 60 degrees Celsius between the heated volatilized components entering the distal end of the cooling segment 704 and the heated volatilized components exiting the proximal end of the cooling segment 704. This temperature differential across the length of the cooling segment 704 protects the temperature sensitive filter segment 706 from the high temperatures of the aerosol formed from the aerosol-forming substrate 702.

[0238] In one embodiment, the length of the cooling segment 704 is at least 15 millimeters. In one embodiment, the length of the cooling segment 704 is between 20 millimeters and 30 millimeters, more specifically between 23 millimeters and 27 millimeters, more specifically between 25 millimeters and 27 millimeters, and more specifically 25 millimeters.

[0239] The cooling segment 704 is made of paper. In one embodiment, the cooling segment 704 is manufactured from a spirally wound paper tube that provides a hollow interior chamber and yet maintains mechanical rigidity. A spirally wound paper tube can meet the stringent dimensional accuracy requirements of high speed manufacturing processes for tube length, outer diameter, roundness, and straightness. In another embodiment, the cooling segment 704 is a recess created from stiff plug wrap or tipping paper. The stiff plug wrap or tipping paper is manufactured to have sufficient rigidity to withstand axial compressive forces and bending moments that may occur during manufacturing and while the article 700 is inserted into the aerosol generating device 602 during use.

[0240] For each of the embodiments of the cooling segment 704, the dimensional accuracy of the cooling segment is sufficient to meet the dimensional accuracy requirements of rapid manufacturing processes.

[0241] Filter segment 706 may be formed of any filter material sufficient to remove one or more volatilized compounds from the heated volatilized components from aerosol-forming substrate 702. In one embodiment, filter segment 706 is made of a monoacetate material, such as cellulose acetate. Filter segment 706 provides cooling and reduced irritation from the heated volatilized components without depleting the amount of the heated volatilized components to an unsatisfactory level for the user.

[0242] The density of the cellulose acetate tow material of the filter segment 706 controls the pressure drop across the filter segment 706, which in turn controls the resistance to withdrawal of the article 700. Thus, the selection of material for the filter segment 706 is important in controlling the resistance to withdrawal of the article 700. In addition, the filter segment performs a filtration function in the article 700.

[0243] The presence of filter segment 706 provides an insulating effect by providing additional cooling to the heated volatilized components exiting cooling segment 704. This additional cooling effect reduces the contact temperature of the user's lips on the surface of filter segment 706.

[0244] One or more flavorants may be added to filter segment 706 either by injecting a flavored liquid directly into filter segment 706 or by embedding or disposing one or more flavored frangible capsules or other flavored carriers within the cellulose acetate tow of filter segment 706. In one embodiment, filter segment 706 is between 6 millimeters and 10 millimeters in length, more preferably 8 millimeters in length.

[0245] The mouth end segment 708 is an annular tube and defines a cavity within the mouth end segment 708. The cavity provides a chamber for the heated volatilized components flowing from the filter segment 706. The mouth end segment 708 is hollow to provide a chamber for aerosol accumulation, yet is rigid enough to withstand axial compressive forces and bending moments that may occur during manufacturing and while the article is inserted into the aerosol generating device 602 in use. In one embodiment, the wall thickness of the mouth end segment 708 is approximately 0.29 millimeters.

[0246] In one embodiment, the length of the oral end segment 708 is between 6 millimeters and 10 millimeters, and more preferably is 8 millimeters.

[0247] The mouth end segment 708 may be manufactured from a spiral wound paper tube that provides a hollow interior chamber and yet maintains mechanical stiffness. Spiral wound paper tubes can meet the stringent dimensional accuracy requirements of high speed manufacturing processes for tube length, outer diameter, roundness, and straightness.

[0248] Mouth end segment 708 serves the function of preventing any liquid condensate that accumulates at the outlet of filter segment 706 from coming into direct contact with the user.

[0249] Of course, in one embodiment, the mouth end segment 708 and the cooling segment 704 may be formed from a single tube, and the filter segment 706 is positioned within that tube separating the mouth end segment 708 and the cooling segment 704.

[0250] Vents 707 are located within cooling segment 704 to aid in cooling article 700. In one embodiment, vents 707 comprise one or more rows of holes, and preferably each row of holes is disposed circumferentially around article 700 in a cross section substantially perpendicular to the longitudinal axis of article 700.

[0251] In one embodiment, there are 1-4 rows of vent holes 707 to provide ventilation for article 700. Each row of vent holes 707 may have 12-36 vent holes 707. The vent holes 707 may be, for example, 100-500 micrometers in diameter. In one embodiment, the axial separation between rows of vent holes 707 is 0.25 millimeters to 0.75 millimeters, and more preferably, the axial separation between rows of vent holes 707 is 0.5 millimeters.

[0252] In one embodiment, the vent holes 707 are of uniform size. In another embodiment, the vent holes 707 vary in size. The vent holes 707 can be made using any suitable technique, for example, one or more of the following techniques: laser techniques, mechanical drilling of the cooling segment 704, or pre-drilling of the cooling segment 704 before it is formed into the article 700. The vent holes 707 are positioned to provide effective cooling to the article 700.

[0253] In one embodiment, the row of vent holes 707 is located at least 11 millimeters from the proximal end of article 700, and more preferably, the vent holes 707 are located 17-20 millimeters from the proximal end of article 700. The location of the vent holes 707 is such that the user does not block the vent holes 707 when article 700 is in use.

[0254] Advantageously, providing a row of vent holes 707 17-20 mm from the proximal end of article 700 allows the vent holes 707 to be located on the exterior of the aerosol generation device 602 when article 700 is fully inserted into the aerosol generation device 602. By locating the vent holes 707 on the exterior of the device 602, unheated air can enter article 700 from outside the device 602 through the vent holes 707 to assist in cooling article 700.

[0255] 10 shows a graph of temperature 404 as a function of time 402 during one heating cycle of a first portion 312 of the susceptor arrangement 310 using readings from a first thermocouple 342, and a second portion of the susceptor arrangement 310 using readings from a second thermocouple 344. In FIG. 10, the temperature of the first portion 312 of the susceptor arrangement 310 from the first thermocouple 342 is shown by a solid line 406. In FIG. 10, the temperature of the second portion 314 of the susceptor arrangement 310 from the second thermocouple 344 is shown by a dashed line 408.

[0256] 10, when heating begins, a first portion 312 of the susceptor arrangement 310 heats up quickly during a first phase 410 and reaches an operating temperature after a first period 414 of about 60 seconds. A second portion 314 of the susceptor arrangement 310 heats up during the first phase 410, but at a much slower rate than the first portion 312. The temperature of the first portion 312 of the susceptor arrangement 310 is higher than the temperature of the second portion 314 of the susceptor arrangement 310 throughout the first phase 410. The second portion 314 of the susceptor arrangement 310 does not reach an operating temperature during the first phase 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.

[0257] 10, 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 susceptor arrangement 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 susceptor arrangement 310 is quickly heated to the operating temperature as well, and reaches the operating temperature after a third period 418 of about 210 seconds from the start of heating.

[0258] Specifically, FIG. 10 illustrates a desired temperature profile for an aerosol-generating system, where a first portion 312 of the susceptor arrangement 310 is arranged to heat a proximal portion of the aerosol-forming substrate, and a second portion 314 of the susceptor arrangement 310 is arranged to heat a distal portion of the aerosol-forming substrate. The proximal portion of the aerosol-forming substrate is closer to the mouthpiece end of the aerosol-generating article comprising the aerosol-forming substrate. Such a temperature profile across the aerosol-forming substrate allows for the generation of an aerosol having desired properties throughout the extended aerosol-generation period. Heating the proximal portion of the aerosol-forming substrate before heating the distal portion of the substrate facilitates optimal delivery of the generated aerosol to the user. 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 therefore, it is believed that the hot aerosol from the proximal portion does not release volatile compounds from the distal portion.

[0259] Such a temperature profile can be achieved by driving varying currents (preferably AC currents) in the first inductor coil 312 and the second inductor coil 314 in various ways. For example, in a first stage, a first varying current (preferably AC current) can be driven in the first inductor coil 312 with a first duty cycle and a second varying current (preferably AC current) can be driven in the second inductor coil 314, the duty cycle of the second varying current being smaller than the duty cycle of the first varying current, such that the current driven in the first inductor coil 312 during the first stage is greater than the current driven in the second inductor coil 314. Of course, in some embodiments, in the first stage 410, no varying current is provided to the second inductor coil 314. In the second stage, the opposite may apply, such that the duty cycle of the first varying current is smaller than the duty cycle of the second varying current.

[0260] 11, an induction heating arrangement 501 is shown. The induction heating arrangement 501 comprises a first LC circuit 510. The first LC circuit 510 comprises a first inductor coil 512 and a first capacitor 514. The first inductor coil 512 has a first inductance. The first capacitor 514 has a first capacitance. The resonant frequency of the first LC circuit 510 is determined by the first inductance and the first capacitance.

[0261] Fig. 11 further illustrates a first transistor 516, such as a FET, connected to the first LC circuit 510. Also illustrated in Fig. 11 are terminals 518 of a DC power supply. The terminals 518 of the DC power supply are connected to a power source for the apparatus, preferably a battery. The first LC circuit 510 is configured to inductively heat a first portion of the susceptor arrangement. The first portion of the susceptor arrangement may be disposed adjacent to the first inductor coil such that the first inductor coil may heat the first portion of the susceptor element by one or both of eddy currents and hysteresis.

[0262] 11 also includes a second LC circuit 520 comprising a second inductor coil 522 and a second capacitor 524. A second transistor 526 is associated with the second LC circuit 520.

[0263] The first transistor 516 is configured to control the operation of the first LC circuit 510. The second transistor 526 is configured to control the operation of the second LC circuit 520.

[0264] The components of the second LC circuit 520 may be similar to the components of the first LC circuit 510. In other words, the second inductor coil 522 may have a second inductance, the second capacitor 524 may have a second capacitance, and the second transistor 526 may be a FET. The two LC circuits 510, 520 may be connected in parallel to a DC power source.

[0265] FIG. 12 shows a controller 527 in addition to a power stage 528. The power stage 528 may include a first LC circuit 510 and a first transistor 516 as shown in FIG. 11. The power stage 528 may alternatively be all of the components shown in FIG. 11. The controller 527 shown in FIG. 12 may include an oscillator 530. The oscillator 530 may be connected to one or both of the first transistor 516 and the second transistor 526. A DC power supply 532 is also shown in FIG. 12. The DC power supply 532 may be utilized to provide power to the elements shown in FIG. 11. Additionally, the DC power supply 532 may be utilized to provide power to the controller 527, and preferably the oscillator 530.

[0266] The controller 527 further comprises a pulse width modulation module 534. The pulse width modulation module 534 may be configured to modulate a signal used to drive the LC circuits 510, 520. The controller 527 may be configured to drive the LC circuits 510, 520. In other words, the controller 527 may be configured to provide an electrical signal to the LC circuits 510, 520.

[0267] The controller 527 may be configured to drive the first LC circuit 510 with an AC current at a first frequency. The first frequency may correspond to a resonant frequency of the first LC circuit 510. The controller 527 may be configured to drive the second LC circuit 520 with an AC current at a second frequency. The second frequency may correspond to a resonant frequency of the second LC circuit 520.

[0268] The resonant frequency of the first LC circuit 510 may be the same as the resonant frequency of the second LC circuit 520. In this situation, during a first stage, the controller 527 may be configured to supply an AC current to the first LC circuit 510 at a frequency corresponding to the resonant frequency of the first LC circuit 510. The first stage may be a stage in which a first portion of the aerosol-forming substrate is heated primarily by a first portion of the susceptor arrangement. During the first stage, the controller 527 may be configured to supply an AC current to the second LC circuit 520 at a frequency different from the resonant frequency of the second LC circuit 520. The second LC circuit 520 will consequently be heated to a lower temperature than the first LC circuit 510. In a second stage in which a second portion of the aerosol-forming substrate is heated primarily by a second portion of the susceptor arrangement, complementary AC currents may be supplied by the controller to the LC circuits 510, 520. In a second stage, an AC current corresponding to the resonant frequency of the second LC circuit 520 may be supplied to the second LC circuit 520, and an AC current having a frequency different from the resonant frequency of the first LC circuit 510 may be supplied to the first LC circuit 510.

[0269] The resonant frequency of the first LC circuit 510 may be different from the resonant frequency of the second LC circuit 520. In this case, during the first stage, the controller 527 may be configured to supply an AC current to the first LC circuit 510 at a frequency corresponding to the resonant frequency of the first LC circuit 510. An AC current of the same frequency may be supplied to the second LC circuit 520. Due to the resonant frequency of the second LC circuit 520 being different from the resonant frequency of the first LC circuit 510, the second LC circuit 520 may heat the second portion of the susceptor arrangement to a lower temperature than the first portion of the susceptor arrangement heated by the first LC circuit 510. In the second stage, when heating of the second portion of the susceptor arrangement is desired, the controller 527 may be configured to supply an AC current at a frequency corresponding to the resonant frequency of the second LC circuit 520, which, in turn, will result in less heating of the first portion of the susceptor arrangement by the first LC circuit 510.

[0270] FIG. 13 illustrates an embodiment in which the first LC circuit 510 is primarily heated in the first stage, while the second LC circuit 520 is heated to a lower temperature during the first stage. This is reversed in the second stage, with the first LC circuit 510 heated to a lower temperature than the second LC circuit 520. To facilitate this, pulse width modulation is employed. More specifically, the top of FIG. 13 illustrates the complementary duty cycles of a first alternating pulse width modulated signal (top left) and a second alternating pulse width modulated signal (top right). The first alternating pulse width modulated signal is herein denoted as a first signal 536. The second alternating pulse width modulated signal is herein denoted as a second signal 538. Duty cycle refers to the percentage of on time of each signal. As seen in FIG. 13, the first signal 536 has a high duty cycle of approximately 80%, while the second signal 538 has a low duty cycle of approximately 20%. The embodiment shown in Figure 13 corresponds to a first stage in which a first portion 541 of the susceptor arrangement 540 is primarily heated, while a second portion 542 of the susceptor arrangement 540 is heated to a lower temperature. Below the signal shown in Figure 13, a first inductor coil 512 and a second inductor coil 522 are shown. Below the inductor coils 512, 522, a susceptor arrangement 540 is shown with a first portion 541 and a second portion 542. Below the susceptor arrangement 540, an aerosol-generating article 542 is shown, which includes an aerosol-forming substrate. Below the aerosol-generating article 542, a diagram 544 showing heat versus distance is shown. The heat is primarily higher in the first portion 541 of the susceptor arrangement 540, while the heat is lower in the second portion 542 of the susceptor arrangement 540. During the second stage, the heating of the susceptor arrangement 540 is different. During the second stage, the second LC circuit 520 heats the second portion 542 of the susceptor arrangement 540 to a higher temperature, and the temperature of the first portion 541 of the susceptor arrangement 540 is lower than in the first stage. To facilitate this, pulse width modulation may be used similar to the first stage. The duty cycle of the second signal 538 may be increased while the duty cycle of the first signal 536 may be decreased. The degree may be gradual from the first stage to the second stage.The duty cycles of the first signal 536 and the second signal 538 may add up to a total of 100%. Alternatively, the duty cycles of the first signal 536 and the second signal 538 may add up to a total amount less than 100%. Illustratively, in a first stage, the duty cycle of the first signal 536 may be greater than 50%, such as 80%, and the duty cycle of the second signal 538 may be close to or at 0%, and vice versa during a second stage.

[0271] Of course, the above-described embodiments are only specific examples and other embodiments are contemplated in accordance with this disclosure.

Claims

1. An aerosol generating device, comprising:

1. An induction heating arrangement configured to heat an aerosol-forming substrate, comprising: a susceptor arrangement heatable by penetration of a varying magnetic field for heating said aerosol-forming substrate; at least a first inductor coil; an induction heating arrangement comprising at least a second inductor coil; A controller, the controller is configured to drive the first inductor coil with a first alternating pulse width modulated signal to generate a first alternating magnetic field to heat a first portion of the susceptor arrangement; the controller is configured to drive the second inductor coil with a second alternating pulse width modulated signal to generate a second alternating magnetic field for heating a second portion of the susceptor arrangement; An aerosol generating device, wherein the controller is configured to provide the first alternating pulse width modulated signal and the second alternating pulse width modulated signal with complementary duty cycles.

2. 2. The aerosol generating device of claim 1, wherein the controller is configured to supply the first alternating pulse-width modulated signal to the first inductor coil during a first stage to raise the temperature of the first portion of the susceptor arrangement from an initial temperature to a first operating temperature, and the controller is configured to supply the first alternating pulse-width modulated signal with a duty cycle greater than 50% during the first stage.

3. 3. The aerosol generating device of claim 2, wherein the controller is configured to supply the first alternating pulse-width modulated signal to the first inductor coil during a second stage to reduce the temperature of the first portion of the susceptor arrangement from the first operating temperature to a second operating temperature, and the controller is configured to supply the first alternating pulse-width modulated signal with a duty cycle of less than 50% during the second stage.

4. 4. The aerosol generating device of claim 3, wherein the controller is configured to supply the second alternating pulse-width modulated signal to the second inductor coil during the first stage to raise the temperature of the second portion of the susceptor arrangement from an initial temperature to a third operating temperature lower than the first operating temperature, and the controller is configured to supply the second alternating pulse-width modulated signal with a duty cycle lower than 50% during the first stage.

5. 5. The aerosol generating device of claim 4, wherein the controller is configured to supply the second alternating pulse-width modulated signal to the second inductor coil during the second stage to raise the temperature of the second portion of the susceptor arrangement from the third operating temperature to a fourth operating temperature higher than the second operating temperature, and the controller is configured to supply the second alternating pulse-width modulated signal with a duty cycle higher than 50% during the second stage.

6. 6. An aerosol generating device according to any one of claims 1 to 5, further comprising a power supply for providing power to the induction heating arrangement.

7. An aerosol generating device according to any one of claims 1 to 6, wherein the controller comprises a microcontroller.

8. The aerosol generating device of claim 7, wherein the microcontroller is configured to utilize a clock frequency of the microcontroller as one or both of the frequency of the first alternating pulse-width modulated signal and the frequency of the second alternating pulse-width modulated signal.

9. An aerosol generating device according to any one of claims 1 to 7, further comprising an oscillator for generating one or both of the frequency of the first alternating pulse-width modulated signal and the frequency of the second alternating pulse-width modulated signal.

10. An aerosol generating device according to any one of claims 1 to 9, further comprising a first power stage, the first power stage comprising at least the first inductor coil and a first capacitor.

11. The aerosol generating device of claim 10 , wherein the first inductor coil and the first capacitor are arranged as a first LC circuit.

12. An aerosol generating device according to any one of claims 1 to 11, further comprising a second power stage, the second power stage comprising at least the second inductor coil and a second capacitor.

13. 13. The aerosol generating device of claim 12, wherein the second inductor coil and the second capacitor are arranged as a second LC circuit.

14. 14. An aerosol generating device according to any one of claims 1 to 13, wherein the second inductor coil is wound in a different direction to the first inductor coil.

15. 15. An aerosol generating device according to any preceding claim, wherein the second inductor coil has a different number of turns relative to the first inductor coil.

16. 16. An aerosol generating device according to any preceding claim, wherein the second inductor coil has a different length relative to the first inductor coil.

17. 17. The aerosol generating device according to any one of claims 1 to 16, wherein the aerosol generating device comprises a device cavity configured to receive an aerosol-forming substrate, the first inductor coil being disposed around the device cavity, and the second inductor coil being disposed around the device cavity.

18. 18. The aerosol generating device of claim 17, wherein the device cavity has a proximal end and a distal end opposite the proximal end, and the proximal end of the device cavity is substantially open for receiving an aerosol generating article.

19. 19. The aerosol generating device of claim 18, 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.

20. An aerosol generating system comprising an aerosol generating device according to any one of claims 1 to 19 and an aerosol-generating article comprising an aerosol-forming substrate.

21. 1. A method for controlling an aerosol generating device, the aerosol generating device comprising:

1. An induction heating arrangement configured to heat an aerosol-forming substrate, comprising: a susceptor arrangement heatable by penetration of a varying magnetic field for heating said aerosol-forming substrate; at least a first inductor coil; an induction heating arrangement comprising at least a second inductor coil; a controller configured to drive the first inductor coil and the second inductor coil; driving the first inductor coil with a first alternating pulse width modulated signal to generate a first alternating magnetic field for heating a first portion of the susceptor arrangement; driving the second inductor coil with a second alternating pulse width modulated signal to generate a second alternating magnetic field for heating a second portion of the susceptor arrangement; providing the first alternating pulse width modulated signal having a complementary duty cycle to a duty cycle of the second alternating pulse width modulated signal.

22. 22. The method of claim 21, wherein during a first stage, the first alternating pulse-width modulated signal is supplied to the first inductor coil to raise a temperature of the first portion of the susceptor arrangement from an initial temperature to a first operating temperature, and wherein during the first stage, the first alternating pulse-width modulated signal is supplied at a duty cycle greater than 50%.

23. 23. The method of claim 22, wherein during a second stage, the first alternating pulse-width modulated signal is supplied to the first inductor coil to reduce the temperature of the first portion of the susceptor arrangement from the first operating temperature to a second operating temperature, and wherein during the second stage, the first alternating pulse-width modulated signal is supplied at a duty cycle less than 50%.

24. 24. The method of claim 23, wherein during the first stage, the second alternating pulse-width modulated signal is supplied to the second inductor coil to raise a temperature of the second portion of the susceptor arrangement from an initial temperature to a third operating temperature, and wherein the second alternating pulse-width modulated signal is supplied with a duty cycle of less than 50% during the first stage.

25. 25. The method of claim 24, wherein during the second stage, the second alternating pulse-width modulated signal is supplied to the second inductor coil to raise the temperature of the second portion of the susceptor arrangement from the third operating temperature to a fourth operating temperature, and wherein the second alternating pulse-width modulated signal is supplied with a duty cycle greater than 50% during the second stage.

26. The method according to any one of claims 21 to 25, wherein the aerosol generating device is an aerosol generating device according to any one of claims 1 to 19.

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