An aerosol-generating device for inductively heating an aerosol-forming substrate

Abstract

The invention relates to an aerosol-generating device for generating an aerosol by inductively heating an aerosol-forming substrate and an aerosol-generating system comprising such a device and an aerosol-generating article comprising an aerosol-forming substrate to be heated. The device comprises first and second LC resonator circuits, the first LC resonator circuit having a first resonant frequency and the second LC resonator circuit having a second resonant frequency different from the first resonant frequency. The control circuit further comprises a drive oscillator circuit comprising an oscillator coil inductively coupled to an induction coil for selectively generating an alternating magnetic oscillator field at the first resonant frequency or at the second resonant frequency such that the alternating magnetic field is selectively generated to selectively heat different sections of a susceptor or different susceptors in different sections of the device. The invention further relates to an aerosol-generating system comprising the device and the aerosol-generating article.

Description

TECHNICAL FIELD

[0001] The present invention relates to an aerosol-generating device for generating an aerosol by inductively heating an aerosol-forming substrate. The invention also relates to an aerosol-generating system comprising such a device and an aerosol-generating article, wherein the article comprises an aerosol-forming substrate to be heated. BACKGROUND

[0002] Aerosol-generating systems based on inductive heating of an aerosol-forming substrate capable of forming an inhalable aerosol are generally known from the prior art. Such systems can comprise an aerosol-generating device having a cavity for receiving a substrate to be heated. The substrate can be an integral part of an aerosol-generating article configured to be used with the device. To heat the substrate, the device can comprise an inductive heater comprising an inductive source comprising an induction coil for generating an alternating magnetic field within the cavity. The field is used for inductive heating of a susceptor arranged in thermal proximity or direct physical contact with the substrate, for example to heat the substrate. Typically, the susceptor can be an integral part of the device or an integral part of the article.

[0003] To heat different segments of the susceptor and / or the substrate, respectively, the device can comprise a plurality of induction coils for selectively generating a plurality of magnetic fields. Thus, the inductive source can be configured such that when one of the coils is actively driven to generate a varying magnetic field, the other coils are not active. Typically, this is achieved by a control circuit comprising a transistor switch for each induction coil. However, the use of multiple transistor switches requires precise control of the switching operation, in particular in time, in order to avoid severe damage to the transistors due to undesired power surges. Furthermore, it is typically not sufficiently prevented that the non-active coils carry currents induced by the active coils, so that there is still significant heating where it is not actually needed.

[0004] Therefore, it is desirable to have an aerosol-generating device and system for inductive heating of an aerosol-forming substrate having the advantages of the prior art solutions but not being limited by their drawbacks. In particular, it is desirable to have an inductive aerosol-generating device and system comprising a control circuit for selectively driving a large number of induction coils with little complexity and high reliability. SUMMARY

[0005] According to the present invention, there is provided an aerosol-generating device for generating an aerosol by inductively heating an aerosol-forming substrate. The device comprises a device housing comprising a cavity configured for removably receiving an aerosol-forming substrate to be heated. The device further comprises at least a first induction coil and a second induction coil. The first induction coil is arranged and configured to generate an alternating magnetic field within a first section of the cavity. The second induction coil is arranged and configured to generate an alternating magnetic field within a second section of the cavity. The device further comprises a control circuit for selectively driving the first induction coil and the second induction coil to selectively generate an alternating magnetic field within the first section and the second section, respectively. The control circuit comprises a first LC resonator circuit and a second LC resonator circuit, wherein the first LC resonator circuit comprises the first induction coil and a first capacitor, and wherein the second LC resonator circuit comprises the second induction coil and a second capacitor. The first LC resonator has a first resonant frequency, and the second LC resonator circuit has a second resonant frequency different from the first resonant frequency. The control circuit further comprises a drive oscillator circuit comprising an oscillator coil for selectively generating an alternating magnetic oscillator field having a frequency close to or at the first resonant frequency or close to or at the second resonant frequency. The oscillator coil is inductively coupled to the first induction coil and the second induction coil, such that when the frequency of the oscillator field is close to or at the first resonant frequency and thus close to or in resonance with the first LC resonator circuit, an alternating magnetic field is generated within the first section, and such that when the frequency of the oscillator field is close to or at the second resonant frequency and thus close to or in resonance with the second LC resonator circuit, an alternating magnetic field is generated within the second section.

[0006] According to the present invention, it has been recognized that a plurality of induction coils for selectively generating a plurality of magnetic fields can be selectively driven by having each coil portion of the respective LC resonator circuit have a different resonant frequency, and by inductively coupling each LC resonator circuit to a drive oscillator coil that can be selectively operated at the different resonant frequencies. Advantageously, due to the different resonant frequencies, when a non-active coil is detuned with respect to the current operating frequency of the oscillator coil, the non-active coil is sufficiently prevented from carrying a current induced by the active coil. Furthermore, this control circuit is less complex, in particular, no precise control of a plurality of transistor switches is required.

[0007] The frequency difference between the first resonance frequency and the second resonance frequency is preferably chosen to be at least as large as required to inductively decouple the first inductive coil and the second inductive coil from each other, such that at each time only one of the coils is operable, while the respective other coil is non-operational and sufficiently prevented from carrying a current induced by the operational coil. In general, the frequency difference between the first resonance frequency and the second resonance frequency depends on a plurality of factors. As will be described in more detail below, the frequency difference depends, inter alia, on the quality factor of the respective first LC resonator circuit and the second LC resonator circuit. The quality factor characterizes the bandwidth of the respective resonator circuit with respect to its center resonance frequency. A high quality factor is generally associated with a small bandwidth, which in turn allows for a small frequency difference between the first resonance frequency and the second resonance frequency.

[0008] Preferably, the first resonance frequency is in the range between 1 % (percent) and 20% (percent) of the second resonance frequency. For example, when the second resonance frequency is 20 MHz (megaHertz), the first resonance frequency is in the range between 200 kHz (kiloHertz) and 4 MHz (megaHertz). Of course, the first resonance frequency can also be in the range between 1 % (percent) and 20% (percent) of the second resonance frequency.

[0009] The second resonance frequency can also be in the range between 1 % (percent) and 20% (percent) of the first resonance frequency.

[0010] In absolute numbers, the first resonance frequency can differ from the second resonance frequency by at least 40 kHz (kiloHertz), in particular by at least 100 kHz (kiloHertz), preferably by at least 200 kHz (kiloHertz), more preferably by at least 500 kHz (kiloHertz) or 1 MHz (megaHertz). For example, the first resonance frequency differs from the second resonance frequency by 120 kHz (kiloHertz). The frequency difference between the first resonance frequency and the second resonance frequency in this range is particularly suitable for sufficiently inductively decoupling the first inductive coil and the second inductive coil from each other.

[0011] For the same reason, at least one of the first and second LC resonator circuits, preferably both LC resonator circuits, can have a quality factor in the range between 2 and 50, in particular between 2 and 20, e.g. 10. As used herein, the term "quality factor" denotes a dimensionless parameter that characterizes the bandwidth of the respective resonator circuit relative to its center resonant frequency and describes how completely the respective resonator circuit is damped. That is, the quality factor relates the maximum or peak energy (reactance) stored in the circuit to the energy (resistance) dissipated each cycle of oscillation. A higher quality factor indicates a lower rate of energy loss relative to the stored energy of the resonator; the oscillations die out more slowly. Thus, increasing the quality factor of the first and second LC resonator circuits causes the bandwidth of the first and second LC resonator circuits to decrease, which advantageously suppresses the coupling of the respective LC resonator circuit to off-resonant magnetic fields. This in turn prevents the respective non-active coil from carrying the current induced by the respective active coil. Furthermore, increasing the quality factor of the first and second LC resonator circuits minimizes energy loss in the LC resonator circuits and thus improves the heating efficiency.

[0012] The first and second resonant frequencies are preferably selected to be in the range between 100 kHz (kilo-Hertz) and 30 MHz (mega-Hertz), in particular between 5 MHz (mega-Hertz) and 15 MHz (mega-Hertz), preferably between 5 MHz (mega-Hertz) and 10 MHz (mega-Hertz). The first and second resonant frequencies preferably correspond to the operating frequencies of the first and second induction coils, respectively. For example, at least one of the first and second resonant frequencies can be in the range between 100 kHz (kilo-Hertz) and 300 kHz (kilo-Hertz), in particular between 150 kHz (kilo-Hertz) and 270 kHz (kilo-Hertz).

[0013] The respective operating frequencies correspond to the frequencies of the alternating magnetic fields generated by the first and second induction coils within the first and second sections of the cavity, respectively. Preferably, the respective alternating magnetic fields are high-frequency alternating magnetic fields. As referred to herein, a high-frequency magnetic field can have a frequency in the range between 100 kHz (kilo-Hertz) and 30 MHz (mega-Hertz), in particular between 5 MHz (mega-Hertz) and 15 MHz (mega-Hertz), preferably between 5 MHz (mega-Hertz) and 10 MHz (mega-Hertz). These values have proven to be advantageous for inductive heating in an aerosol-generating device. Accordingly, the first and second resonance frequencies can be in the range between 100 kHz (kilo-Hertz) and 30 MHz (mega-Hertz), in particular between 5 MHz (mega-Hertz) and 15 MHz (mega-Hertz), preferably between 5 MHz (mega-Hertz) and 10 MHz (mega-Hertz). For example, at least one of the first and second resonance frequencies can be in the range between 100 kHz (kilo-Hertz) and 300 kHz (kilo-Hertz), in particular between 150 kHz (kilo-Hertz) and 270 kHz (kilo-Hertz).

[0014] As referred to herein, the frequency of the oscillator field is close to the first or second resonance frequency, respectively, when the difference between the frequency of the oscillator field and the first or second resonance frequency, respectively, is less than 500 kHz (kilo-Hertz), in particular less than 100 kHz (kilo-Hertz), preferably less than 50 kHz (kilo-Hertz), more preferably less than 20 kHz (kilo-Hertz), even more preferably less than 10 kHz (kilo-Hertz), most preferably less than 5 kHz (kilo-Hertz).

[0015] The oscillator coil is preferably arranged coaxially with at least one of the first and second induction coils, in particular each of them. Due to the coaxial arrangement, the magnetic field generated by the oscillator coil mostly overlaps with the first and second induction coils, respectively. Advantageously, this increases the inductive coupling between the oscillator coil and the first and second induction coils, respectively.

[0016] Likewise, the oscillator coil can at least partially surround at least one of the first and second induction coils, in particular each of them. Advantageously, this also increases the inductive coupling between the oscillator coil and the first and second induction coils, respectively.

[0017] Preferably, the oscillator coil is arranged coaxially and at least partially surrounds at least one, in particular each, of the first and second induction coils. That is, the oscillator coil can at least partially surround at least one, in particular each, of the first and second induction coils and can be arranged coaxially with at least one, in particular each, of the first and second induction coils. Advantageously, this even increases the overlap between the magnetic fields of the different coils and, thus, the inductive coupling between the oscillator coil and the first and second induction coils.

[0018] At least one, in particular each, of the oscillator coil, the first and second induction coils can be a spiral coil. A spiral coil configuration proves particularly advantageous for a coaxial arrangement, in particular a coaxial surrounding arrangement, of the oscillator coil with the first and second induction coils, respectively. Furthermore, the use of a spiral induction coil advantageously provides a substantially homogeneous field configuration inside the coil. In order to prevent deposits and / or possible corrosion on the coils, at least one, in particular each, of the oscillator coil, the first and second induction coils can comprise a protective cover or a protective layer.

[0019] In the case of a spiral coil, at least one, in particular each, of the oscillator coil, the first and second induction coils can have a substantially cylindrical shape. Likewise, the cross-section of at least one, in particular each, of the oscillator coil, the first and second induction coils - as seen along the length axis of the respective coil - can be one of circular, oval, elliptical, rectangular, square, triangular, polygonal.

[0020] The aerosol-generating device can further comprise a magnetic flux concentrator for inductively coupling the oscillator coil to at least one of the first and second induction coils. Advantageously, the flux concentrator increases the inductive coupling between these coils. As used herein, the term "flux concentrator" refers to an element that is configured to concentrate a magnetic field, i.e. to distort the magnetic field such that the magnetic field density within a particular volume is increased. Thus, the flux concentrator is preferably configured to distort the magnetic field of the oscillator coil towards at least one of the magnetic field region of the first induction coil and the region of the second induction coil. In addition, the flux concentrator can serve to reduce the extent to which the magnetic field propagates beyond the various coils. That is, the flux concentrator preferably serves as a magnetic shield. Advantageously, this can reduce undesired heating of adjacent sensitive components of the device, e.g. a metal housing, or of adjacent sensitive items outside the device. By reducing undesired heat loss, the efficiency of the aerosol-generating device can be further improved.

[0021] The flux concentrator preferably has a high relative magnetic permeability, which serves to concentrate and direct the magnetic field or magnetic field lines generated by the oscillator coil. As used herein, the term "high relative magnetic permeability" refers to a relative magnetic permeability of at least 100, in particular at least 1000, preferably at least 10000, even more preferably at least 50000, most preferably at least 80000. These example values refer to the value of the relative magnetic permeability at DC and a temperature of 25 degrees Celsius. Likewise, the relative magnetic permeability is preferably 80 at a frequency between 6 MHz (megahertz) and 10 MHz (megahertz) and a temperature of 25 degrees Celsius. As used herein and within the art, the term "relative magnetic permeability" refers to the ratio of the magnetic permeability of a material or medium, such as the flux concentrator, to the magnetic permeability of free space μ_0, where μ_0 is 4π·10-7N·A-2(4·Pi·10E-07 Newton per square Ampere). Thus, the flux concentrator preferably comprises or is made of a material or materials having a relative magnetic permeability of at least 100, in particular at least 1000, preferably at least 10000, even more preferably at least 50000, most preferably at least 80000. Likewise, these example values refer to the value of the relative magnetic permeability at DC and a temperature of 25 degrees Celsius. Likewise, the relative magnetic permeability is preferably 80 at a frequency between 6 MHz (megahertz) and 10 MHz (megahertz) and a temperature of 25 degrees Celsius.

[0022] Preferably, the flux concentrator comprises a ferromagnetic material, for example a ferrite material (such as ferrite particles held in a matrix, ferrite powder), or any other suitable material comprising a ferrite material (such as ferromagnetic iron, ferromagnetic steel or stainless steel). The matrix can comprise a binder, for example a polymer, for example silicone. The ferromagnetic material can comprise at least one metal selected from iron, nickel, copper, molybdenum, manganese, silicon and combinations thereof.

[0023] To drive the oscillator coil at or close to the first resonant frequency, or at or close to the second resonant frequency, the drive oscillator circuit preferably comprises a single transistor switch which can be selectively operated at or close to the first resonant frequency or at or close to the second resonant frequency. Advantageously, using a single transistor switch to drive more than one inductive coil reduces the complexity of the drive oscillator circuit. Furthermore, using a single transistor switch is space saving, thus allowing for a very compact design of the aerosol-generating device.

[0024] The transistor switch can be any type of transistor. For example, the transistor switch can be embodied as a bipolar junction transistor (BJT). However, more preferably, the transistor switch is implemented as a field effect transistor (FET), such as a metal-oxide-semiconductor field effect transistor (MOSFET) or a metal-semiconductor field effect transistor (MESFET).

[0025] The different resonance frequencies of the first and second LC resonator circuits can be achieved in several ways. Generally, the resonance frequency of an LC circuit comprising an inductive coil and a capacitor is given by the formula f = 1 / (2-pi-sqrt[L-C]), where f is the resonance frequency in hertz, L is the inductance of the inductive coil in henry, and C is the capacitance of the capacitor in farad. Thus, a certain resonance frequency can be achieved by appropriately selecting the capacitance of the capacitor and the inductance of the inductive coil. The inductance of the inductive coil depends, inter alia, on the number of windings and, for example in the case of a spiral coil, on the axial length and diameter of the coil. Thus, a certain inductance of the inductive coil can be achieved by appropriately selecting the number of windings, the axial length and the diameter of the coil. Generally, the inductance increases with an increasing number of windings. Likewise, the inductance decreases with an increasing length or diameter of the coil.

[0026] Thus, the different resonance frequencies of the first and second LC resonator circuits can be achieved by at least one of making the inductance of the first inductive coil different, in particular greater or smaller, than the inductance of the second inductive coil, or making the capacitance of the first capacitor different, in particular greater or smaller, than the capacitance of the second capacitor.

[0027] For example, it can be preferred to make the first and second inductive coils identical, in particular to make the inductance of the first inductive coil equal to the inductance of the second inductive coil. In this case, the different resonance frequencies can be achieved by making the capacitance of the first capacitor of the first LC resonator circuit smaller than the capacitance of the second capacitor of the second LC resonator circuit. Thus, the inductance of the first inductive coil can be equal to the inductance of the second inductive coil, and the capacitance of the first capacitor can be smaller or greater than the capacitance of the second capacitor. In particular, the capacitance of the first capacitor can be 2% (percent), preferably 5% (percent), more preferably 10% (percent) smaller or greater than the capacitance of the second capacitor. Of course, the capacitance of the second capacitor can also be smaller or greater than the capacitance of the first capacitor, in particular 2% (percent), preferably 5% (percent), more preferably 10% (percent) smaller or greater than the capacitance of the first capacitor.

[0028] Alternatively, the inductance of the first induction coil can be smaller or larger, in particular smaller or larger by a factor of two, preferably by a factor of ten, than the inductance of the second induction coil, and the capacitance of the first capacitor can be equal to the capacitance of the second capacitor.

[0029] Likewise, the inductance of the first induction coil can also be different from the inductance of the second induction coil, in particular larger or smaller than the inductance of the second induction coil, and the capacitance of the first capacitor is different from the capacitance of the second capacitor, in particular larger or smaller than the capacitance of the second capacitor.

[0030] In an example, the first induction coil can comprise seven windings and the second induction coil can comprise nine windings, which results in the inductance of the first induction coil being smaller than the inductance of the second induction coil.

[0031] At least one of the first induction coil and the second induction coil can have an inductance in the range between 0.1 pH (micro Henry) and 2 mH (milli Henry), in particular between 0.1 pH (micro Henry) and 1 mH (milli Henry), preferably between 0.3 pH (micro Henry) and 1.2 pH (micro Henry), more preferably between 0.6 pH (micro Henry) and 0.9 pH (micro Henry). Depending on the frequency of the magnetic field to be achieved, the capacitance values of the first capacitor and the second capacitor can be chosen accordingly. Preferably, at least one of the first capacitor and the second capacitor has a capacitance in the range between 0.1 nF (nano Farad) and 20 pF (pico Farad), in particular between 1 nF (nano Farad) and 5 pF (pico Farad), preferably between 10 nF (nano Farad) and 1 pF (pico Farad).

[0032] As further described above, the alternating magnetic fields of the first induction coil and the second induction coil are used for inductive heating of at least one susceptor which in turn is arranged in thermal proximity or direct physical contact with a substrate, for example to heat the substrate. Generally, the at least susceptor can be an integral part of the device or an integral part of an aerosol generating article comprising an aerosol-forming substrate to be heated, and is configured to be removably received in a cavity of the aerosol generating device.

[0033] As part of the device, the at least one susceptor can be arranged at least partially within the cavity. Likewise, as part of the aerosol generating article, the at least one susceptor can be arranged within the cavity of the aerosol generating device when the article is inserted into the cavity of the device.

[0034] In particular, the aerosol generating device can comprise at least one susceptor, in particular one (single) susceptor or two susceptors.

[0035] In case of a single susceptor, the susceptor is preferably arranged within the cavity such that a first portion of the susceptor is at least partially, preferably completely, arranged within the first section of the cavity and a second portion of the susceptor is at least partially, preferably completely, arranged within the second section. Thus, in use of the device, the first portion of the susceptor experiences the magnetic field of the first induction coil and the second portion of the susceptor experiences the magnetic field of the second induction coil.

[0036] Likewise, in case the aerosol-generating device comprises a plurality of susceptors, in particular two susceptors, the device can comprise a first susceptor and a second susceptor. The first susceptor and the second susceptor are preferably arranged within the cavity such that the first susceptor is at least partially, preferably completely, arranged within the first section of the cavity and the second susceptor is at least partially, preferably completely, arranged within the second section of the cavity. Thus, in use of the device, the first susceptor experiences the magnetic field of the first induction coil and the second susceptor experiences the magnetic field of the second induction coil.

[0037] Advantageously, the first section and the second section of the (single) susceptor, or the first susceptor and the second susceptor, can be arranged separately from each other or can be arranged within the aerosol-forming substrate, for example to heat different portions of the aerosol-forming substrate, in particular a first portion and a second portion of the aerosol-forming substrate, or to heat different aerosol-forming substrates, in particular a first aerosol-forming substrate and a second aerosol-forming substrate.

[0038] The first susceptor and the second susceptor can be formed as separate parts. In particular, the first susceptor and the second susceptor can be arranged separately from each other or can be arranged within the aerosol-forming substrate.

[0039] As used herein, the term "susceptor" refers to an element capable of converting electromagnetic energy into heat when subjected to an alternating electromagnetic field. This can be the result of magnetic hysteresis losses and / or eddy currents induced in the susceptor, depending on the electrical and magnetic properties of the susceptor material. In ferromagnetic or ferrimagnetic susceptors, magnetic hysteresis losses occur due to the switching of magnetic domains within the material under the influence of an alternating electromagnetic field. Eddy currents can be induced if the susceptor is electrically conductive. In the case of an electrically conductive ferromagnetic or ferrimagnetic susceptor, heat can be generated due to both eddy currents and magnetic hysteresis losses.

[0040] Thus, the at least one susceptor can be formed of any material capable of being inductively heated to a temperature sufficient to generate an aerosol from the aerosol-forming substrate. The at least one susceptor can comprise a metal or carbon. The at least one susceptor can comprise a ferromagnetic material, such as ferritic iron or ferromagnetic steel or stainless steel. A preferred susceptor can be formed of a 400 series stainless steel, such as a 410 grade or 420 grade or 430 grade stainless steel. Another suitable susceptor can comprise aluminium.

[0041] The at least one susceptor can comprise various geometrical configurations. The at least one susceptor can comprise or can be a susceptor pin, a susceptor rod, a susceptor blade, a susceptor strip or a susceptor plate. In case the susceptor is part of an aerosol-generating device, the susceptor pin, the susceptor pin, the susceptor rod, the susceptor blade, the susceptor strip or the susceptor plate can protrude into a cavity of the device, preferably towards an opening of the cavity for inserting an aerosol-generating article into the cavity.

[0042] The at least one susceptor can comprise or can be a filament susceptor, a mesh susceptor, a wick susceptor.

[0043] Likewise, the at least one susceptor can comprise or can be a susceptor sleeve, a susceptor cup, a cylindrical susceptor or a tubular susceptor. Preferably, the interior void of the susceptor sleeve, the susceptor cup, the cylindrical susceptor or the tubular susceptor is configured to removably receive at least a portion of the aerosol-forming substrate to be heated.

[0044] The aforementioned susceptor can have any cross-sectional shape, such as a circular, an oval, a square, a rectangular, a triangular or any other suitable shape.

[0045] As used herein, the term "aerosol-generating device" generally refers to an electrically operated device capable of interacting with at least one aerosol-forming substrate, in particular with an aerosol-forming substrate arranged within an aerosol-generating article, in order to generate an aerosol by heating the substrate. Preferably, the aerosol-generating device is a smoking device for generating an aerosol that can be directly inhaled by a user through the user's mouth. In particular, the aerosol-generating device is a hand-held aerosol-generating device.

[0046] The control circuit according to the present application can form part of the aerosol-generating device or can be an overall controller of the aerosol-generating device configured to control the operation of the device. In particular, the controller can be configured to control the operation of the inductive heating process, in particular to inductively heat the aerosol-forming substrate to a predetermined operating temperature.

[0047] The operating temperature for heating the aerosol-forming substrate can be at least 180 degrees Celsius, in particular at least 300 degrees Celsius, preferably at least 350 degrees Celsius, more preferably at least 370 degrees Celsius, most preferably at least 400 degrees Celsius. These temperatures are typical operating temperatures for heating, but not burning, the aerosol-forming substrate. For example, the operating temperature can be in the range between 180 degrees Celsius and 370 degrees Celsius, in particular between 180 degrees Celsius and 240 degrees Celsius or between 280 degrees Celsius and 370 degrees Celsius. Generally, the operating temperature can depend on at least one of the type of aerosol-forming substrate to be heated, the configuration of the susceptor and the arrangement of the susceptor relative to the aerosol-forming substrate when the system is in use. For example, in case the susceptor is configured and arranged to surround the aerosol-forming substrate, e.g. when the system is in use, the operating temperature can be in the range between 180 degrees Celsius and 240 degrees Celsius. Likewise, in case the susceptor is configured to be arranged within the aerosol-forming substrate, e.g. when the system is in use, the operating temperature can be in the range between 280 degrees Celsius and 370 degrees Celsius.

[0048] The controller can comprise a microprocessor, e.g. a programmable microprocessor, a microcontroller or an application specific integrated chip (ASIC) or other electronic circuitry capable of providing control.

[0049] The controller can be configured to generate an alternating drive signal and to provide said alternating drive signal to the oscillator circuit, in particular to the single transistor switch (more specifically to the gate of the single transistor switch) so as to operate the oscillator circuit, in particular the single transistor switch, at or close to the first resonance frequency or at or close to the second resonance frequency. That is, the controller can be configured to generate an alternating drive signal and to provide said alternating drive signal at different frequencies, in particular at a first frequency close to or equal to the first resonance frequency and at a second frequency close to or equal to the second resonance frequency. For example, the controller can comprise a clock or a voltage controlled oscillator configured to provide the respective alternating drive signals.

[0050] The aerosol-generating device can comprise a power source, in particular a DC power source, configured to provide a DC power source voltage and a DC power source current to the controller. In particular, the DC voltage can be applied to the drain input and the source input of the single transistor switch. Preferably, the power source is a battery, such as a lithium iron phosphate battery. As an alternative, the power source can be another form of charge storage device, such as a capacitor. The power source can need to be charged, i.e. the power source can be rechargeable. The power source can have a capacity that allows storing sufficient energy for one or more user experiences. For example, the power source can have sufficient capacity to allow for the continuous generation of aerosol for a period of about six minutes or a whole multiple of six minutes. In another example, the power source can have sufficient capacity to allow for a predetermined number of puffs or discrete activations of the inductive heating device.

[0051] The aerosol-generating device can comprise a body, which preferably comprises at least one of the control circuit, in particular the first and second inductive coils, the first and second capacitors, the drive oscillator circuit, the oscillator coil, the single transistor switch if present, the flux concentrator if present, the at least one susceptor if present, the controller, the power source and at least a portion of the cavity.

[0052] In addition to the body, the aerosol-generating device can comprise a mouthpiece, in particular in the case that the aerosol-generating article to be used with the device does not comprise a mouthpiece. The mouthpiece can be mounted to the body of the device. The mouthpiece can be configured to close the cavity when the mouthpiece is mounted to the body. For attaching the mouthpiece to the body, the proximal end portion of the body can comprise a magnetic or mechanical mount, for example a bayonet mount or a snap-fit mount, which engages with a corresponding counterpart at the distal end portion of the mouthpiece. In the case that the device does not comprise a mouthpiece, the aerosol-generating article to be used with the aerosol-generating device can comprise a mouthpiece, for example a filter segment.

[0053] The aerosol-generating device can comprise at least one air outlet, for example an air outlet in the mouthpiece if present.

[0054] Preferably, the aerosol-generating device comprises an air path extending from the at least one air inlet through the cavity and, if present, further possibly to the air outlet in the mouthpiece. Preferably, the aerosol-generating device comprises at least one air inlet in fluid communication with the cavity. Thus, the aerosol-generating system can comprise an air path extending from the at least one air inlet into the cavity and possibly further through the aerosol-forming substrate within the article and the mouthpiece into the user’s mouth.

[0055] The first induction coil, the second induction coil, the first capacitor, the second capacitor, the oscillator coil and the flux concentrator, if present, can be part of an induction module which is arranged within the device housing and which forms at least part of the cavity of the device or is arranged circumferentially around at least part of the cavity of the device, in particular removably.

[0056] According to the present application, there is also provided an aerosol-generating system comprising an aerosol-generating device according to the present application and as described herein. The system further comprises an aerosol-generating article for use with the device, wherein the article comprises an aerosol-forming substrate to be inductively heated by the device. The aerosol-generating article is at least partially received or receivable in the cavity of the device.

[0057] As used herein, the term "aerosol-generating system" refers to the combination of an aerosol-generating article as further described herein and an aerosol-generating device according to the present application and as described herein. In the system, the article and the device cooperate to generate an inhalable aerosol.

[0058] As used herein, the term "aerosol-generating article" refers to an article comprising at least one aerosol-forming substrate which, when heated, releases volatile compounds from which an aerosol can be formed. Preferably, the aerosol-generating article is a heated-type aerosol-generating article. That is, the aerosol-generating article comprises at least one aerosol-forming substrate which is intended to be heated rather than combusted in order to release volatile compounds from which an aerosol can be formed. The aerosol-generating article can be a consumable, in particular a consumable which will be discarded after a single use. For example, the article can be a cartridge comprising a liquid aerosol-forming substrate to be heated. Alternatively, the article can be a rod-shaped article, in particular a tobacco article, similar to a conventional cigarette.

[0059] As used herein, the term "aerosol-forming substrate" means a substrate formed from or comprising aerosol-forming material, which is capable of releasing volatile compounds to generate an aerosol upon heating. The aerosol-forming substrate is intended to be heated, rather than combusted, in order to release the volatile compounds that form the aerosol. The aerosol-forming substrate can be a solid or liquid aerosol-forming substrate or a gel-like aerosol-forming substrate or any combination thereof. For example, the aerosol-forming substrate can comprise solid and liquid components, or liquid and gel-like components, or solid and gel-like components, or liquid, solid and gel-like components. The aerosol-forming substrate can comprise a tobacco-containing material, which contains volatile tobacco flavour compounds that are released from the substrate upon heating. Alternatively or additionally, the aerosol-forming substrate can comprise a non-tobacco material. The aerosol-forming substrate can also comprise an aerosol former. Examples of suitable aerosol formers are glycerol, triacetin (glyceryl triacetate) and propylene glycol. The aerosol-forming substrate can also comprise other additives and ingredients, such as nicotine or flavourings. The aerosol-forming substrate can also be a paste-like material, a small pouch of porous material comprising the aerosol-forming substrate, or loose tobacco, for example mixed with a gelling or binding agent, which can include a common aerosol former such as glycerol, and which is compressed or moulded into a rod.

[0060] As previously mentioned, the at least one susceptor for inductively heating the aerosol-forming substrate can be an integral part of the aerosol-generating article, rather than a part of the aerosol-generating device. Thus, the aerosol-generating article can comprise at least one susceptor positioned in thermal proximity or thermal contact with the aerosol-forming substrate, such that in use, when the article is received in the cavity of the device, the susceptor can be inductively heated by the inductive heating device. In particular, the aerosol-forming substrate can comprise one (single) susceptor or two susceptors.

[0061] In the case of a single susceptor, the susceptor can be arranged within the article such that, upon insertion of the article into the cavity of the device, a first portion of the susceptor is arranged at least partially, preferably entirely, within the first section of the cavity, and a second portion of the susceptor is arranged at least partially, preferably entirely, within the second section. Thus, in use of the system, the first portion of the susceptor is subjected to the magnetic field of the first induction coil, and the second portion of the susceptor is subjected to the magnetic field of the second induction coil.

[0062] Likewise, in case the aerosol-generating article comprises a plurality of susceptors, in particular two susceptors, the article can comprise a first susceptor and a second susceptor. The first susceptor and the second susceptor can be arranged within the article such that upon insertion of the article into the cavity of the device, the first susceptor is at least partially, preferably completely, arranged within the first section of the cavity and the second susceptor is at least partially, preferably completely, arranged within the second section of the cavity. Thus, upon use of the system, the first susceptor experiences the magnetic field of the first induction coil and the second susceptor experiences the magnetic field of the second induction coil. The first susceptor and the second susceptor can be formed as separate parts.

[0063] Advantageously, the first section and the second section of the (single) susceptor, or the first susceptor and the second susceptor, can be arranged within the aerosol-forming substrate separately from each other, for example to heat different portions of the aerosol-forming substrate, in particular a first portion and a second portion of the aerosol-forming substrate, or to heat different aerosol-forming substrates, in particular a first aerosol-forming substrate and a second aerosol-forming substrate arranged at different positions within the article.

[0064] Thus, the aerosol-generating article can comprise a first aerosol-forming substrate and a second aerosol-forming substrate arranged at different positions within the article. In particular, the first aerosol-forming substrate and the second aerosol-forming substrate can differ from each other in at least one of content, composition, flavour, texture and state of matter (solid, gel-like, liquid).

[0065] Further features and advantages of the aerosol-generating system according to the present application have been described with respect to the aerosol-generating device and will not be repeated.

[0066] Of course, the aerosol-generating device according to the present invention and as described herein can be configured to heat more than two aerosol-forming substrates or more than two portions of an aerosol-forming substrate, respectively. Accordingly, the aerosol-generating device according to the present invention and as described herein can comprise more than two induction coils, for example three, four, five or more induction coils, for generating respective alternating magnetic fields within more than two segments of the cavity, for example three, four, five or more segments. Accordingly, the aerosol-generating device can comprise more than two LC resonator circuits, one for each coil, wherein each LC resonator circuit comprises one of the coils and a respective capacitor and has a resonant frequency that is different from each of the resonant frequencies of the respective other LC resonator circuits. Likewise, the drive oscillator circuit comprising the oscillator coil can be configured for selectively generating an alternating magnetic oscillator field at more than two frequencies, i.e. at the respective resonant frequencies of the different LC resonator circuits. Accordingly, the aerosol-generating article according to the present invention and as described herein can comprise more than two portions of an aerosol-forming substrate, for example three, four, five or more portions. Likewise, such an article can comprise more than two aerosol-forming substrates, for example three, four, five or more aerosol-forming substrates. Accordingly, when the susceptor is part of an aerosol-generating device, the device can comprise a susceptor having more than two portions, for example three, four, five or more portions. Likewise, the device can comprise more than two susceptors, for example three, four, five or more susceptors. Vice versa, when the susceptor is part of an aerosol-generating article, the article can comprise a susceptor having more than two portions, for example three, four, five or more portions. Likewise, the article can comprise more than two susceptors, for example three, four, five or more susceptors. BRIEF DESCRIPTION OF DRAWINGS

[0067] The present invention will be further described, by way of example only, with reference to the accompanying drawings in which:

[0068] Figure 1 a schematic cross-sectional view of an aerosol-generating system according to a first embodiment of the present invention is shown;

[0069] Figure 2 an exemplary embodiment of a control circuit that can be used within an aerosol-generating system according to Figure 1 the present invention is schematically shown;

[0070] Figure 3 a schematic cross-sectional view of an aerosol-generating system according to a second embodiment of the present invention is shown;

[0071] Figure 4 a schematic cross-sectional view of an aerosol-generating system according to a third embodiment of the present invention is shown; and

[0072] Figure 5 A schematic cross-sectional view of an aerosol-generating system according to a fourth embodiment of the application is shown. DETAILED DESCRIPTION

[0073] Figure 1 A first exemplary embodiment of an aerosol-generating system 1 according to the application is schematically shown. The system 1 is configured for generating an aerosol by inductively heating an aerosol-forming substrate 91, in particular inductively heating the aerosol-forming substrate section by section or portion by portion. The system 1 comprises two main components: an aerosol-generating article 90 comprising the aerosol-forming substrate to be heated; and an aerosol-generating device 10 for use with the article 90. The device 10 comprises a cavity 20 for receiving the article 90, and an inductive heating arrangement 30 for heating the substrate within the article 90 when the article 90 is inserted into the cavity 20.

[0074] The article 90 has a rod shape that is substantially similar to the shape of a conventional cigarette. In the present embodiment, the article 90 comprises four elements arranged in coaxial alignment: a substrate segment 91, a support segment 92, an aerosol-cooling segment 94, and a filter segment 95. The substrate segment is arranged at the distal end of the article 90 and comprises the aerosol-forming substrate 91 to be heated. The aerosol-forming substrate can comprise, for example, a rolled sheet of homogenized tobacco material comprising glycerol as an aerosol-former. The support segment 92 comprises a hollow core forming a central air passage 93. The aerosol-cooling segment 94 is for cooling the volatile components of the aerosol-forming substrate. The filter segment 95 serves as a mouthpiece and can comprise, for example, cellulose acetate fibers. All four elements are substantially cylindrical elements arranged sequentially one after the other. The segments have substantially the same diameter and are delimited by an outer wrapper 99 made of cigarette paper, for example, to form a cylindrical rod.

[0075] The device 10 comprises a substantially rod-shaped main body 11 formed by a substantially cylindrical device housing. Within a distal portion 13, the device 10 comprises a power source 16, for example a lithium-ion battery, and a control circuit 17 for controlling the operation of the device 10, in particular for controlling the inductive heating process.

[0076] Within a proximal portion 14 opposite the distal portion 13, the device 10 comprises a cavity 20. The cavity 20 is open at the proximal end 12 of the device 10, thereby allowing the article 90 to be easily inserted into the cavity 20. A bottom portion 25 of the cavity 20 separates the distal portion 13 of the device 10 from the proximal portion 14 of the device 10, in particular from the cavity 20. Preferably, the bottom portion 25 is made of a thermally insulating material, for example PEEK (polyether ether ketone). Thus, the electrical components of the control circuit 17 within the distal portion 13 can be separated from the heat, aerosol or residues generated within the cavity 20 during heating of the substrate 91.

[0077] The aerosol-generating device 10 according to the present embodiment is configured to heat the aerosol-forming substrate within the substrate segment 91 in segments, i.e. to heat different portions of the aerosol-forming substrate separately. In the present embodiment, the device 10 is configured to heat the first portion 96 and the second portion 97 of the aerosol-forming substrate separately. Figure 1 The dashed line 98 in Fig. 1 indicates that the aerosol-forming substrate is hypothetically divided into the first portion 96 and the second portion 97.

[0078] To heat the first portion 96 and the second portion 97 separately, the induction heating device 30 comprises a first induction coil 31 and a second induction coil 32. The first induction coil 31 is arranged and configured to generate an alternating magnetic field within the first segment 21 of the cavity 20, while the second induction coil 32 is arranged and configured to generate an alternating magnetic field within the second segment 22 of the cavity. When the aerosol-generating article 90 is received in the cavity 20, the first segment 21 and the second segment 22 of the cavity 20 are assigned to the location of the first portion 96 and the second portion 97 of the aerosol-forming substrate.

[0079] The induction heating device 30 further comprises a susceptor 60 which is arranged within the cavity 20 such that a first portion 61 of the susceptor 60 is subjected to the electromagnetic field generated by the first induction coil 31 and such that a second portion 62 of the susceptor 60 is subjected to the electromagnetic field generated by the second induction coil 32.

[0080] In the present embodiment, the susceptor 60 is a susceptor blade, the distal end of which is attached to the bottom portion 25 of the cavity 20. From there, the susceptor blade extends into the interior void of the cavity 20 towards the opening of the cavity 20 at the proximal end 12 of the device 10. The other end of the susceptor blade 60, i.e. the distal free end, is tapered, for example to allow the susceptor blade to easily penetrate the aerosol-forming substrate within the distal end portion of the article 90. As can be seen in Fig. 1, when the aerosol-generating article 90 is received in the cavity 20, the first portion 61 of the susceptor 60 is arranged within the first portion 96 of the aerosol-forming substrate, while the second portion 62 of the susceptor 60 is arranged within the second portion 97 of the substrate. Instead of a blade, the susceptor can also be a susceptor pin or a susceptor rod. Figure 1

[0081] ​Hence, when the first induction coil 31 is activated, an alternating electromagnetic field is generated substantially only within the first section 21 of the cavity 20. As a result, depending on the magnetic and electric properties of the susceptor material, a heat generating eddy current and / or a hysteresis loss is induced substantially only in the first portion 61 of the susceptor 60. Hence, when the second induction coil 32 is not active, substantially only the first portion 61 of the susceptor 60 is heated, while the second portion 62 of the susceptor 60 remains substantially unheated. As a result, only the first portion 96 of the substrate is heated, e.g. to form an aerosol, which can be drawn downstream through the aerosol-generating article 90 for inhalation by a user. Likewise, when the second induction coil 32 is activated, an alternating electromagnetic field is generated substantially only within the second section 22 of the cavity 20, so that only the second portion 62 of the susceptor 60 is inductively heated, while the first portion 61 of the susceptor 60 remains substantially unheated. As a result, only the second portion 97 of the substrate is heated, so that an aerosol is formed, which can be drawn downstream through the aerosol-generating article 90 for inhalation by a user.

[0082] To allow the first induction coil 31 and the second induction coil 32 to be activated independently from each other, and hence to selectively generate an alternating magnetic field within the first section 21 or the second section 22 of the cavity 20, each coil 31, 32 forms part of an LC resonator circuit having a different resonant frequency. Each LC resonator circuit is inductively coupled to a (common) drive oscillator coil 32, which can be operated selectively at or close to the different resonant frequencies. That is, the present application is based on inductive driving of the first induction coil 31 and the second induction coil 32, however, at different drive frequencies of each coil, e.g. to inductively decouple the operation of the first induction coil 31 and the second induction coil 32 from each other.

[0083] Figure 2 An exemplary embodiment of a control circuit 18 that can be used within an aerosol-generating system according to Figure 1 is schematically shown. In accordance with the basic idea described above, the control circuit 18 comprises a first LC resonator circuit 51 and a second LC resonator circuit 52, wherein the first LC resonator circuit 51 comprises the first induction coil 31 and a first capacitor 41, and wherein the second LC resonator circuit 52 comprises the second induction coil 32 and a second capacitor 42. The first LC resonator circuit 51 has a first resonant frequency, while the second LC resonator circuit 52 has a second resonant frequency f2 different from the first resonant frequency f1. The control circuit 18 further comprises a drive oscillator circuit 35, which comprises an oscillator coil 33 (also in Figure 1The oscillator coil 33 is inductively coupled to both the first 31 and second 32 induction coils. However, due to the difference between the first 1 and second 2 resonance frequencies, the alternating magnetic oscillator field generated by the oscillator coil 33 is substantially only coupled into the first induction coil 31 or the first LC resonator circuit 51, respectively, when the frequency of the magnetic oscillator field is close to or equal to the first resonance frequency 1 of the first LC resonator circuit 51. The other way around is also true, the alternating magnetic oscillator field generated by the oscillator coil 33 is substantially only coupled into the second induction coil 32 or the second LC resonator circuit 52, respectively, when the frequency of the magnetic oscillator field is close to or equal to the second resonance frequency 2 of the second LC resonator circuit 52.

[0084] Thus, with reference to Figure 1 When the oscillator field is close to or at the first resonance frequency 1 and thus close to or in resonance with the first LC resonator circuit 51, an alternating magnetic field is generated within the first section 21 of the cavity 20. Likewise, when the oscillator field is close to or at the second resonance frequency 2 and thus close to or in resonance with the second LC resonator circuit, an alternating magnetic field is generated within the second section 22 of the cavity 21.

[0085] Advantageously, the difference between the first 1 and second 2 resonance frequencies also prevents the respective non-active coil from carrying the current induced by the active coil, as the non-active coil is sufficiently detuned with respect to the current operating frequency of the oscillator coil 33.

[0086] Preferably, the difference between the first 1 and second 2 resonance frequencies is at least 40 kHz (kiloHertz), in particular at least 100 kHz (kiloHertz), preferably at least 100 kHz (kiloHertz), more preferably at least 500 kHz (kiloHertz), or at least 1 MHz (megaHertz). For example, the first resonance frequency and the second resonance frequency differ by 120 kHz (kiloHertz). The first resonance frequency and the second resonance frequency are preferably selected in the range between 100 kHz (kiloHertz) and 30 MHz (megaHertz), in particular between 5 MHz (megaHertz) and 15 MHz (megaHertz), preferably between 5 MHz (megaHertz) and 10 MHz (megaHertz). For example, the first resonance frequency can be 150 kHz (kiloHertz) and the second resonance frequency can be 270 kHz (kiloHertz).

[0087] The first 31 and second 32 induction coils can have an inductance in the range of, for example, between 0.3 μΗ (micro henry) and 1.2 μΗ (micro henry), preferably between 0.6 μΗ (micro henry) and 0.9 μΗ (micro henry). Depending on the frequency of the magnetic field to be achieved, the capacitance values of the first 41 and second 42 capacitors can be chosen accordingly. Preferably, the first 41 and second 42 capacitors have a capacitance in the range between 1 nF (nano farad) and 10 μΡ (micro farad), in particular between 10 nF (nano farad) and 2 μΡ (micro farad).

[0088] In order to drive the oscillator coil 33 at or near the first resonance frequency fi or at or near the second resonance frequency f2, the drive oscillator circuit 35 according to the embodiment shown in Figure 2 comprises a single transistor switch 70 which can be selectively operated at or near the first resonance frequency fi or at or near the second resonance frequency f2. In the present embodiment, the switch 70 is a field effect transistor (FET) having a gate input 71 of a control gate terminal. The source input 72 and drain output 73 of the field effect transistor are connected in series with the oscillator coil 33 and a power supply 16 which can correspond to the power supply 16 shown in Figure 1 . Thus, by applying an alternating drive signal to the gate input 71 - having a drive frequency at or near the first resonance frequency fi or the second resonance frequency f2 - the oscillator coil 33 is alternately switched on and off at that drive frequency. This switching on and off causes the oscillator coil 32 to generate a magnetic oscillator field at or near the first resonance frequency fi or the second resonance frequency f2 due to the varying magnetic flux inside the oscillator coil 33. The alternating drive signal is schematically shown in Figure 2 by two square wave signals having frequencies fi and f2. Preferably, the alternating drive signal is generated by means of the controller 17 shown in Figure 1 and provided to the oscillator circuit 35.

[0089] As can be seen in Figure 1 , the first 31 and second 32 induction coils are helical coils which circumferentially encircle the first 21 and second 22 sections of the cylindrical cavity 20, respectively. The first 31 and second 32 induction coils are each formed by a plurality of wire windings which extend along a length axis of the respective coil 31. The wire can have any suitable cross-sectional shape, such as square, oval or triangular. In the present embodiment, the wire has a circular cross-section. In other embodiments, the wire can have a flat cross-sectional shape. This basically applies to the oscillator coil 33 as well.

[0090] As can be seen in Figure 1As can also be seen, the oscillator coil 33 is arranged coaxially with and partially around each of the first induction coil 31 and the second induction coil 32. Advantageously, this increases the overlap between the magnetic fields of the different coils, and thus increases the inductive coupling between the oscillator coil and the first and second induction coils, respectively.

[0091] Figure 3 A schematic cross-section of an aerosol generation system 101 according to a second embodiment of the present invention is shown. Figure 3 System 101 is very similar to... Figure 1 System 1. Therefore, the same or similar features are indicated by the same reference numerals but incremented by 100. Compared with the aerosol generation system 1 according to the first embodiment, the system 101 according to the second embodiment includes an aerosol generation article 190, which includes a first aerosol forming matrix 196 and a second aerosol forming matrix 197 arranged sequentially at the distal portion of the article 190. The first aerosol forming matrix 196 and the second aerosol forming matrix 197 differ from each other in their compositions and ingredients for enriching the user experience.

[0092] In addition, according to Figure 1 Compared to System 1, according to Figure 3 System 101 includes two sensors that are not part of the aerosol generating apparatus 110, but rather part of the aerosol generating article 190. A strip-shaped first sensor 161 is disposed within a first aerosol forming matrix 196. Similarly, a strip-shaped second sensor 162 is disposed within a second aerosol forming matrix 197. The two sensors 161 and 162 are centrally disposed within respective aerosol forming matrices extending substantially along the longitudinal axis of the aerosol generating article 190. Specifically, the sensors 161 and 162 are formed as separate portions spaced apart from each other, which thermally decouples the two sensors 161 and 162 from each other.

[0093] When the article 190 is inserted into the cavity 120 of the device 110, the first sensor 161 and the first aerosol forming matrix 196 are arranged in the first section 121 of the cavity 120. Similarly, the second sensor 162 and the second aerosol forming matrix 197 are arranged in the second section 122 of the cavity 120. Therefore, when using the system 101, the first sensor 161 experiences the magnetic field of the first induction coil 131, while the second sensor 162 experiences the magnetic field of the second induction coil 132, thereby allowing the first aerosol forming matrix 196 and the second aerosol forming matrix 197 to be heated separately from each other.

[0094] The aerosol generating apparatus 110 according to the second embodiment differs from the apparatus 10 according to the first embodiment in that it has a flux concentrator 180 arranged coaxially around the first induction coil 131, the second induction coil 132, and the oscillator coil 133. In this embodiment, the flux concentrator 180 is a cylindrical element made of a material with high relative permeability, such as ferromagnetic stainless steel. The flux concentrator 180 is arranged and configured to distort the magnetic field of the oscillator coil 133 toward the magnetic field regions of the first induction coil 131 and the second induction coil 132, thereby increasing the magnetic coupling between the oscillator coil 133 and the first and second induction coils 131 and 132. Additionally, as described above, the flux concentrator also serves as a magnetic shield.

[0095] besides, Figure 3 The aerosol generation device at the location and according to Figure 1 The devices are the same.

[0096] Figure 4 A schematic cross-section of an aerosol generation system 201 according to a third embodiment of the present invention is shown. Figure 4 System 201 is very similar to... Figure 3 System 101. Therefore, identical or similar features are represented by the same reference numerals but incremented by 100. Compared to the aerosol generation system 101 according to the second embodiment, system 201 according to the third embodiment includes a first receptor 261 and a second receptor 262, which are part of the aerosol generation apparatus 210, but not part of the article 290. In this embodiment, the first receptor 261 and the second receptor 262 are receptor sleeves.

[0097] A sleeve-shaped first sensor 261 is disposed on the inner surface of cavity 220, in the outer periphery of the first section 221 of cavity 220. When using device 210, the first sensor 261 experiences essentially only the magnetic field of the first induction coil 231. Similarly, a sleeve-shaped second sensor 262 is disposed on the inner surface of cavity 220, in the outer periphery of the second section 222 of cavity 220. When using device 210, the second sensor 262 experiences essentially only the magnetic field of the second induction coil 232. Specifically, the first sensor 261 and the second sensor 262 are formed as separate, spaced-apart portions, which thermally decouples the two sensors 261 and 262 from each other.

[0098] As mentioned above Figure 3The first aerosol forming matrix 296 and the second aerosol forming matrix 297 are arranged within the article 290 such that when the article 290 is inserted into the cavity 220 of the device 210, the first aerosol forming matrix 296 is arranged in the first section 221 of the cavity 220, and the second aerosol forming matrix 297 is arranged in the second section 222 of the cavity 220. Therefore, the first aerosol forming matrix 296 and the second aerosol forming matrix 297 can be heated separately from each other.

[0099] Figure 5 A schematic cross-section of an aerosol generation system 301 according to a fourth embodiment of the present invention is shown. Figure 5 System 301 is very similar to... Figure 4 System 201. Therefore, the same or similar features are indicated by the same reference numerals but incremented by 100. Compared with the third embodiment, the aerosol generating apparatus 310 according to the fourth embodiment includes a single sleeve-shaped sensor 360. The single sleeve-shaped sensor 360 is arranged relative to the first induction coil 331 and the second induction coil 332 at the inner surface of the cavity 320, such that in use, the first portion 361 of the sensor 360 experiences an electromagnetic field generated by the first induction coil 331, and the second portion 362 of the sensor 360 experiences an electromagnetic field generated by the second induction coil 332. Therefore, the heating device 330 of the apparatus 310 can be used to separately heat different portions of the aerosol forming matrix 391. That is, when the article 390 is inserted into the cavity 320 and the first induction coil 331 is activated, the first portion 361 of the sensor 360 heats the first portion 396 of the aerosol forming matrix. Similarly, when the second induction coil 332 is activated, the second portion 362 of the sensor 360 heats the second portion 397 of the aerosol forming matrix 391.

[0100] In addition, with Figure 1 , Figure 3 and Figure 4 Compared to the implementation scheme shown, according to Figure 5 The aerosol-generating article 390 does not include a support section. Instead, according to... Figure 5 The article comprises: a matrix section 391 including an aerosol-forming matrix to be heated; an aerosol cooling section 392 adjacent to the matrix section 391 for cooling volatile components of the aerosol-forming matrix; a filter section 394 adjacent to the aerosol cooling section 392 for filtering volatile components of the aerosol-forming matrix; and a mouth section 395 adjacent to the filter section 394 for receiving in a user's mouth. Additionally, the article 390 may include an end member (not shown) at its distal end opposite to the proximal end (i.e., opposite to the mouth section 395).

[0101] For example, the substrate segment 391 can comprise an aerosol-forming substrate comprising homogenised tobacco strands and an aerosol former, such as glycerol (glycerin), propylene glycol, triacetin (glyceryl triacetate) or combinations thereof.

[0102] The cooling segment 392 can comprise a hollow tube defining an air passage for the flow of volatilised components of the heated aerosol-forming substrate through and cooling. The thickness of the tube wall can be, for example, 0.29 mm. The length of the cooling segment 392 is preferably such that, when the article 390 is fully inserted into the device 310, the cooling segment 392 will be partially inserted into the cavity 320. The length of the cooling segment 392 can be between 20 mm and 30 mm, in particular between 23 mm and 27 mm, preferably 25 mm to 27 mm, for example 25 mm. The cooling segment 392 can be made of paper, such as a spirally wound paper tube.

[0103] The filter segment 394 can be formed of any filtration material sufficient to remove one or more compounds volatilised from the aerosol-forming substrate. For example, the filter segment 394 can be made of a monoacetate material, such as cellulose acetate. One or more flavours can be added to the filter segment 394 in the form of a flavouring liquid injected directly into the filter segment 394 or by embedding or arranging one or more flavourised friable capsules or other flavour carriers within, for example, a cellulose acetate plug of the filter segment 394. The length of the filter segment 394 can be between 6 mm and 10 mm, for example 8 mm.

[0104] The mouth end segment 395 serves to prevent any liquid condensate accumulated at the outlet of the filter segment 394 from coming into direct contact with the user. Like the cooling segment 392, the mouth end segment 395 can comprise a hollow, in particular annular, tube defining an air passage for the flow of volatilised components of the heated aerosol-forming substrate therethrough. The length of the mouth end segment 395 can be between 6 mm and 10 mm, for example 8 mm. The mouth end segment 395 can be made of paper, such as a spirally wound paper tube. The thickness of the tube wall can be, for example, 0.29 mm.

[0105] Additionally, according to Figure 5The aerosol-generating article 390 comprises ventilation zones to enable air to flow from the exterior of the article 390 into the interior of the article 390. For example, the ventilation zones can take the form of one or more ventilation holes formed through the outer layer of the article 390. In particular, the ventilation zones can comprise one or more rows of ventilation holes, wherein each row of holes is arranged circumferentially around the article 390 in a cross-section substantially perpendicular to the longitudinal axis of the article 390. Each row of ventilation holes can have between 12 and 36 ventilation holes. The diameter of the ventilation holes can be between 100 and 500 micrometres. The axial separation between rows of ventilation holes can be between 0.25 and 0.75 millimetres, for example 0.5 millimetres. In the present embodiment, the ventilation zones comprise two rows of ventilation holes 393, each row of ventilation holes being arranged circumferentially around the article 390. As can be seen in Figure 5 the ventilation holes 393 are located in the cooling segment 392 to assist with aerosol cooling. In particular, the ventilation holes 393 are arranged such that, when the article 390 is received in the cavity 320, the ventilation holes 393 are located outside of the cavity 320, thus allowing non-heated air to enter the article 390 from the exterior through the ventilation holes 393. For example, the ventilation holes 393 can be located at least 11 millimetres, in particular between 17 and 20 millimetres, from the proximal end of the article 390. In any case, the location of the ventilation holes is preferably chosen such that the user does not block the ventilation holes 393 during use.

[0106] Of course, the ventilation zones as described above, in particular the one or more ventilation holes as described above, can also be provided in the aerosol-generating articles 90, 190 and 290 shown in Figure 1 , Figure 3 and Figure 4 .

[0107] The cooling segment 392, the filter segment 394 and the mouth end segment 395 can together form a filter assembly. For example, the total length of the filter assembly can be between 37 and 45 millimetres. Preferably, the total length of the filter assembly is about 41 millimetres. The length of the substrate segment 391 can be between 34 and 50 millimetres, preferably between 38 and 46 millimetres, for example 42 millimetres. The total length of the article 390 can be between 71 and 95 millimetres, preferably between 79 and 87 millimetres, for example about 83 millimetres.

[0108] As in the other embodiments shown in Figure 1 , Figure 3 and Figure 4 , all segments 391, 392, 394 and 395 of the article 390 according to Figure 5 have substantially the same diameter and are defined by an outer wrapper 399 made of cigarette paper, for example to form a cylindrical rod.

Claims

1. An aerosol generating apparatus for generating aerosols by induction heating an aerosol-forming matrix, the aerosol generating apparatus comprising: A device housing, the device housing including a cavity configured to removably receive an aerosol forming matrix to be heated; At least a first induction coil and a second induction coil, wherein the first induction coil is arranged and configured to generate an alternating magnetic field in a first section of the cavity, and the second induction coil is arranged and configured to generate an alternating magnetic field in a second section of the cavity; A control circuit is provided for selectively driving the first induction coil and the second induction coil to selectively generate alternating magnetic fields in the first segment and the second segment, respectively. The control circuit includes: a first LC resonator circuit, comprising a first induction coil and a first capacitor; and a second LC resonator circuit, comprising a second induction coil and a second capacitor; wherein the first LC resonator circuit has a first resonant frequency, and the second LC resonator circuit has a second resonant frequency different from the first resonant frequency; and The control circuit further includes a drive oscillator circuit comprising a common oscillator coil for selectively generating an alternating magnetic oscillator field having a frequency close to or at the first resonant frequency or close to or at the second resonant frequency. The common oscillator coil is inducedly coupled to the first induction coil and the second induction coil such that when the frequency of the alternating magnetic oscillator field is close to or at the first resonant frequency and thus close to resonating with the first LC resonator circuit, an alternating magnetic field is generated in the first segment, and when the frequency of the alternating magnetic oscillator field is close to or at the second resonant frequency and thus close to resonating with the second LC resonator circuit, an alternating magnetic field is generated in the second segment.

2. The aerosol generating apparatus according to claim 1, wherein the first resonant frequency is in the range of 1% to 20% of the second resonant frequency.

3. The aerosol generating apparatus according to claim 1 or 2, wherein the first resonant frequency differs from the second resonant frequency by at least 40 kHz.

4. The aerosol generating apparatus according to claim 1 or 2, wherein the first resonant frequency and the second resonant frequency are in the range between 100 kHz and 30 MHz.

5. The aerosol generating apparatus according to claim 1 or 2, wherein the common oscillator coil is arranged coaxially with each of the first induction coil and the second induction coil.

6. The aerosol generating apparatus according to claim 1 or 2, wherein the common oscillator coil, the first induction coil and the second induction coil are helical coils.

7. The aerosol generating apparatus according to claim 1 or 2, wherein the common oscillator coil at least partially surrounds each of the first induction coil and the second induction coil.

8. The aerosol generating apparatus according to claim 1 or 2, wherein the driving oscillator circuit includes a single transistor switch, the single transistor switch being selectively operable at the first resonant frequency or the second resonant frequency for driving the common oscillator coil at the first resonant frequency or the second resonant frequency.

9. The aerosol generating apparatus according to claim 1 or 2, wherein at least one of the first capacitor and the second capacitor has a capacitance in the range of 1 nF to 10 μF.

10. The aerosol generating apparatus according to claim 1 or 2, wherein the inductance of the first induction coil is equal to the inductance of the second induction coil, and wherein the capacitance of the first capacitor is smaller or larger than the capacitance of the second capacitor.

11. The aerosol generating apparatus according to claim 1 or 2, wherein at least one of the first LC resonator circuit and the second LC resonator circuit has a quality factor in the range of 2 to 50.

12. The aerosol generating apparatus according to claim 1 or 2 further includes a magnetic flux concentrator, the magnetic flux concentrator being used to inductively couple the common oscillator coil to the first induction coil and the second induction coil.

13. The aerosol generating apparatus according to claim 1 or 2, further comprising at least one sensor disposed at least partially within the cavity and surrounded by the first induction coil and the second induction coil.

14. The aerosol generating apparatus according to claim 3, wherein the first resonant frequency differs from the second resonant frequency by at least 100 kHz.

15. The aerosol generating apparatus according to claim 14, wherein the first resonant frequency differs from the second resonant frequency by at least 500 kHz.

16. The aerosol generating apparatus according to claim 15, wherein the first resonant frequency differs from the second resonant frequency by at least 1 MHz.

17. The aerosol generating apparatus according to claim 4, wherein the first resonant frequency and the second resonant frequency are in the range between 5 MHz and 15 MHz.

18. The aerosol generating apparatus according to claim 17, wherein the first resonant frequency and the second resonant frequency are in the range of 5MHz and 10MHz.

19. The aerosol generating apparatus according to claim 10, wherein the capacitance of the first capacitor is 2% smaller or larger than the capacitance of the second capacitor.

20. The aerosol generating apparatus according to claim 19, wherein the capacitance of the first capacitor is 5% smaller or larger than the capacitance of the second capacitor.

21. The aerosol generating apparatus according to claim 20, wherein the capacitance of the first capacitor is 10% smaller or larger than the capacitance of the second capacitor.

22. The aerosol generating apparatus according to claim 11, wherein at least one of the first LC resonator circuit and the second LC resonator circuit has a quality factor in the range of 2 to 20.

23. An aerosol generation system comprising an aerosol generation apparatus according to any one of claims 1 to 22 and an aerosol generation article that at least partially receives or is capable of receiving in the cavity of the aerosol generation apparatus, wherein the aerosol generation article comprises at least one aerosol forming matrix to be heated.

24. The aerosol generation system of claim 23, wherein the aerosol generation article includes at least one sensor positioned in thermal proximity or thermal contact with the at least one aerosol forming matrix, such that, in use of the aerosol generation system, when the aerosol generation article is received in the cavity of the aerosol generation apparatus, the sensor can be inductively heated by an induction source.

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