Induction heated aerosol-generating device for use with aerosol-generating article

Abstract

An aerosol-generating system comprises an inductively heated aerosol-generating device (1) and an aerosol-generating article (2). The article comprises an aerosol-forming substrate (25) and a flat susceptor, in particular a sheet-like susceptor (22), arranged in an evaporation portion of the article. The device comprises a DC power source (12) and an induction heating device, the induction heating device comprising a DC / AC inverter. The DC / AC inverter comprises a switching power amplifier having at least one transistor switch (111), at least one transistor switch driver circuit (112) and an LC load network (113) having at least a capacitor and a cylindrical-spiral induction coil (L2). An interior space of the induction coil is configured to removably receive at least an evaporated portion of the aerosol-generating article. The invention relates to a cylindrical-helical induction coil having a non-circular planarized or oblong cross-sectional shape comprising two opposing flat sections connected by two opposing, at least partially curved sections, the cylindrical-helical induction coil having a non-circular planarized or oblong cross-sectional shape, the cylindrical-helical induction coil having a non-circular planarized or oblong cross-sectional shape, in particular, it consists of two opposing flat sections connected by two opposing, at least partially curved sections.

Description

[0001] The present disclosure relates to an induction heated aerosol generating device for use with an aerosol generating article. The present invention also relates to an aerosol generating system comprising such a device and such an article.

[0002] Aerosol generating devices and systems for generating inhalable aerosols by inductively heating an aerosol-forming substrate are generally known from the prior art. Such systems and devices may include an induction heating device, which includes an induction coil for generating an alternating magnetic field. The field is used to cause at least one of heat-generating eddy currents or hysteresis losses in a susceptor, which is arranged to be in thermal proximity or direct physical contact with an aerosol-forming substrate that can form an inhalable aerosol when heated. The susceptor and the substrate may be a part of an aerosol-generating article that can be received in the internal space of the induction coil. In particular, the substrate may be a liquid aerosol-forming substrate stored in a liquid reservoir of the article. The reservoir may be in fluid communication with a susceptor located in the evaporation portion of the article, in which the aerosol-forming liquid may evaporate by the interaction of the susceptor with the alternating magnetic field of the induction coil. Alternatively, the aerosol-forming substrate may be a solid or gel-like aerosol-forming substrate that is in thermal proximity or direct physical contact with the susceptor, wherein both the susceptor and the substrate are contained in the evaporation portion of the article. Alternatively, the susceptor may also be a part of the aerosol generating device.

[0003] In some articles, the susceptor may have a flat shape, such as a sheet-like shape, which provides a large surface-to-mass ratio. A large surface-to-mass ratio is beneficial for efficiently utilizing the heat generated by the susceptor and enhancing heat transfer from the susceptor to the aerosol-forming substrate.

[0004] During the user's experience, the induction heating device can be operated continuously or on demand (particularly in an intermittent mode, such as on a puff-by-puff basis). While in the continuous operation mode, the susceptor is permanently maintained at a temperature level sufficient to form a satisfactory amount of aerosol, if the heating system is operated intermittently, such as on demand by the user, achieving a sufficient temperature level within a short period of time may be a challenge.

[0005] It is therefore desirable to have an aerosol generating device and an aerosol generating system for inductively heating an aerosol-forming substrate that has the advantages of prior art solutions while alleviating their limitations. In particular, it is desirable to have an aerosol generating device and an aerosol generating system for inductively heating an aerosol-forming substrate that each allows achieving a higher heating efficiency, in particular reaching a sufficient temperature level in a shorter period of time, in thermal proximity to or direct physical contact with a flat susceptor, in particular a sheet-like susceptor.

[0006] According to the present invention, an induction heating aerosol generating device for use with an aerosol generating article is provided. The article comprises an aerosol-forming substrate and a flat susceptor, in particular a sheet-like susceptor, wherein the susceptor is arranged in a vaporizing portion of the article and is configured for heating the aerosol-forming substrate by interaction of the susceptor with an alternating magnetic field provided by the aerosol generating device. The device comprises a DC power supply and an induction heating device, the induction heating device comprising power supply electronics, the power supply electronics comprising a DC / AC inverter connected to the DC power supply. The DC / AC inverter comprises a switching power amplifier having at least one transistor switch, at least one transistor switch drive circuit associated with the transistor switch, and an LC load network comprising at least a capacitor and a cylindrical-spiral induction coil. The inner space of the induction coil is configured for removably receiving at least the vaporizing portion of the aerosol generating article. The cylindrical-spiral induction coil has a non-circular flattened cross-sectional shape, the non-circular flattened cross-sectional shape comprising two opposite flat sections connected by two opposite at least partially curved sections, in particular consisting of two opposite flat sections connected by two opposite at least partially curved sections.

[0007] As used herein, the term "aerosol generating device" is used to describe an electrically operated device capable of interacting with at least one aerosol generating article, the at least one aerosol generating article comprising an aerosol-forming substrate, in particular an aerosol-forming liquid, and a susceptor, so as to generate an aerosol by inductively heating the substrate via the interaction of the susceptor with an alternating magnetic field provided by the device. Preferably, the aerosol generating device is a suction 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 handheld aerosol generating device.

[0008] According to the present invention, it has been found that the heating efficiency of an induction-heated aerosol generating device having an induction coil intended for heating a flat susceptor, in particular a sheet-like susceptor, can be improved by adapting the geometry of the magnetic field within the inner space of the induction coil where the susceptor is to be placed to the flat shape of the susceptor. In particular, it has been found that, provided that the susceptor is placed such that the main surface faces or is aligned with, in particular substantially parallel to, two opposite flat sections of the cross-sectional shape of the periphery of the induction coil, i.e. such that the flat plane defined by the flat susceptor geometry is aligned with, in particular substantially parallel to, the flat plane defined by two opposite flat sections of the periphery of the induction coil (the flat plane defined by the two opposite flat sections of the periphery of the induction coil may include the long symmetry axis defined below and may additionally be perpendicular to the short symmetry axis defined below), by making the cross-sectional shape of the induction coil flat, the radial distance between the induction coil and the main surface (main surface) of the flat susceptor (i.e. the main surface of the susceptor determining the flat susceptor geometry) can be reduced. The reduced radial distance results in an increase in the magnetic field strength at the location of the susceptor, which in turn results in an increase in the heating efficiency. Thus, for a given power level passing through the induction coil, the level of heat generated in the susceptor increases, which allows, inter alia, to reach a desired temperature level in a shorter period of time.

[0009] The efficiency of induction heated aerosol generating devices is further improved by the use of a cylindrical-helical induction coil, which advantageously allows a uniform alternating magnetic field to be generated.

[0010] Preferably, the non-circular flattened cross-sectional shape of the induction coil comprises a short symmetry axis and a long symmetry axis. The short symmetry axis may extend between two opposing flat sections of the induction coil. Conversely, the long symmetry axis may extend between two opposing at least partially curved sections of the induction coil.

[0011] Preferably, the ratio of the maximum distance between two opposing at least partially curved sections along the long symmetry axis to the maximum distance between two opposing flat sections along the short symmetry axis is in the range between 1.2 and 3, in particular between 1.5 and 2.5. These ratios are particularly advantageous with regard to a suitable match between the geometry of the magnetic field and the flat shape of the susceptor to be heated.

[0012] In order to arrange the induction coil as close as possible to the interior space of the induction coil where the susceptor is to be placed, the maximum distance between two opposing flat sections along the short symmetry axis may be in the range between 4 and 7 mm, in particular between 5 and 6 mm.

[0013] Likewise, the maximum distance along the major axis of symmetry between two opposing at least partially curved sections may be in the range between 7 mm and 10 mm, in particular between 8 mm and 9 mm.

[0014] Preferably, the two opposing flat sections are substantially parallel to each other. The parallel configuration is particularly helpful for matching the magnetic field geometry to a susceptor having a sheet-like shape. In particular, each of the two opposing flat sections may be a substantially straight line.

[0015] The shape of the two at least partially curved sections is selected to provide a smooth transition between two opposing flat sections to ensure smooth bending.Preferably, the at least partially curved section is one of substantially semicircular, substantially semi-oval, substantially semi-elliptical or substantially parabolic.

[0016] In particular, each (the respective end point of) two opposite flat sections (connecting the two opposite flat sections) may be tangent to (the respective end points of) the two opposite flat sections. Thus, the transition between the two opposite flat sections is particularly smooth.

[0017] Preferably, the non-circular flattened cross-sectional shape of the induction coil is oblong. As used herein, the term "oblong" defines a shape consisting of two semicircles connected by parallel lines tangent to their endpoints. Thus, the induction coil may have an oblong-cylindrical shape.

[0018] In general, a cylindrical-spiral induction coil can be formed by one or more turns of a coil wire. For example, the induction coil comprises 3 to 6 turns, in particular 4 to 5 turns. The number of turns does not necessarily need to be an integer. It can also be any number between two integers.

[0019] Preferably, the coil wire may have a circular cross-section.

[0020] The coil wire may be one of a solid wire, a stranded wire, and a Litz wire.

[0021] When the induction coil is driven by an AC current, the current through the coil wire flows only close to the outer surface of the coil wire. Therefore, the diameter of the coil wire does not need to be large to carry a large current. In order to achieve a compact coil design with a sufficiently large number of turns per length unit, it may be beneficial if the diameter of the coil wire is in the range between 0.8 mm and 1.5 mm, in particular between 1 mm and 1.2 mm.

[0022] Preferably, the induction coil has an axial length extension which is similar to the axial length extension of the susceptor measured in the same direction when received in the inner space of the induction coil. The axial length of the induction coil may be in the range between 4 mm and 12 mm, in particular between 5 mm and 8 mm.

[0023] Preferably, there is a gap between adjacent turns of the induction coil. That is, as seen in a longitudinal cross section of the induction coil, the pitch of the spiral induction coil may be greater than the extension of the cross section of the coil wire in the axial direction. In particular, in the case where the coil wire has a circular cross section, the pitch of the spiral induction coil may be greater than the diameter of the coil wire. Therefore, the coil wires of adjacent turns do not touch each other. This allows the use of coil wires without wire insulation. However, the coil wire may be an insulated coil wire. For example, the coil wire may be a coated copper wire, such as an enamel-coated copper wire. In addition, the gap between adjacent turns of the induction coil is used for better heat dissipation and thus makes the resistive power loss in the coil winding smaller. The gap between adjacent turns also helps to reduce undesirable ringing effects / crossover effects. As seen in a longitudinal cross section of the induction coil, the (center-to-center) distance between adjacent parts of the coil wire of adjacent turns may be in the range of between 1.1 and 1.4 times, in particular between 1.2 and 1.3 times, of the extension of the cross section of the coil wire in the axial direction. In particular, in the case of a coil wire having a circular cross section, the (center-to-center) distance between adjacent portions of the coil wire of adjacent turns is in the range between 1.1 and 1.4 times, in particular between 1.2 and 1.3 times, the diameter of the coil wire. These ranges have proven to provide sufficiently large distances (which still allow a compact coil design), i.e. a sufficiently large number of turns per length unit.

[0024] Additionally, the aerosol generating device may comprise a flux concentrator arranged around the induction coil and configured, in use, to distort the alternating magnetic field of the induction coil towards an interior space of the interior space of the induction coil.

[0025] In particular, the flux concentrator may comprise a sleeve portion circumferentially surrounding the induction coil and further comprising an annular protrusion portion protruding radially inwardly beyond the sleeve portion at each axial end of the sleeve portion, such that the induction coil is axially arranged between the annular protrusion portions. Advantageously, the annular protrusion portion protruding radially inwardly beyond the sleeve portion at each axial end of the sleeve portion results in a concentration or focusing of the magnetic field within the inner space of the induction coil. As a result, the level of heat generated in the susceptor for a given power level passing through the induction coil is increased compared to an induction coil without a flux concentrator or with only a sleeve-shaped flux concentrator without an annular protrusion portion at each axial end. This also contributes to improving the heating efficiency, in particular to reaching a desired temperature level in a shorter period of time. In addition to this, the flux concentrator acts as a magnetic shield, which can reduce the extent to which the magnetic field propagates beyond the induction coil.

[0026] Preferably, the flux concentrator comprises or is made of one or more layers of flux concentrator foil. According to a preferred arrangement of the flux concentrator, each of the annular protruding portions may be made of one or more layers of flux concentrator foil, wherein the one or more layers of the annular protruding portions extend in radially outward direction at least to the outer circumference of the induction coil, preferably beyond the outer circumference of the induction coil. On top of the annular protruding portions, the sleeve portion may be made of one or more layers of flux concentrator foil surrounding the induction coil and each of the annular protruding portions. According to an alternative arrangement of the flux concentrator, the sleeve portion may be made of one or more layers of flux concentrator foil surrounding the induction coil, while each of the annular protruding portions may be made of one or more layers of flux concentrator foil to end flush with the outer circumference of the sleeve portion in radial direction.

[0027] At least one of the annular protruding portions, preferably the more distal annular protruding portion, may comprise a recess or a feed-through opening for passing a connecting lead for the induction coil. In case the flux concentrator is formed by winding a flux concentrator foil, the recess or the feed-through opening may be cut into the annular protruding portion after winding the flux concentrator foil.

[0028] Similar to the induction coil, the flux concentrator may have a non-circular flattened cross-sectional shape corresponding to the non-circular flattened cross-sectional shape of the induction coil, i.e. a non-circular flattened cross-sectional shape comprising, in particular consisting of, two opposing flat sections connected by two opposing at least partially curved sections. In particular, the cross-sectional shape of the flux concentrator may be oblong.

[0029] The aerosol generating device may further comprise a coil support on which the induction coil and the flux concentrator (if present) are supported.

[0030] The coil support may comprise a support tube, in particular a cylindrical support tube, wherein the induction coil is arranged around the circumference of the support tube.

[0031] The interior space of the support tube may form a receiving cavity for removably receiving at least a portion, in particular at least a vaporizing portion, of an aerosol-generating article with which the device is configured to be used.

[0032] In order to provide lateral confinement of the coil windings in the axial direction, the coil support may comprise a circumferential collar at each axial end of the support tube.

[0033] At least one of the collars may include a recess or a feed-through opening for passing connecting leads for the induction coil.

[0034] Similar to the induction coil, the outer circumference of the support tube may also have a non-circular flattened cross-sectional shape, comprising, in particular consisting of, two opposite flat sections connected by two opposite at least partially curved sections. That is, the outer portion (outer portion) of the support tube along its outer circumference may comprise, in particular may consist of, two opposite flat outer portions connected by two opposite at least partially curved outer portions. In this configuration, the induction coil may be wound around the outer circumference of the support tube such that the non-circular flattened cross-sectional shape of the induction coil follows the non-circular flattened cross-sectional shape of the outer circumference of the support tube.

[0035] Preferably, the non-circular flattened cross-sectional shape of the support tube is oblong, in particular when the cross-sectional shape of the induction coil is also oblong. Thus, the support tube and the induction coil may have an oblong-cylindrical shape, i.e. a flattened cylindrical shape having two opposing planar side wall portions parallel to each other and having two opposing side hemispherical wall portions between the two opposing planar side wall portions.

[0036] In the case where the outer circumference of the support tube has a non-circular flattened cross-sectional shape as described above, each of the above-mentioned collars (if present) may also have a non-circular flattened cross-sectional shape corresponding to the non-circular flattened cross-sectional shape of the outer circumference of the support tube. In particular, each collar may have an oblong cross-sectional shape.

[0037] In order to stabilize the coil winding, the outer periphery of the support tube may include a wire recess pattern in which the coil wire is received. The wire recess pattern is preferably selected so that it corresponds to the desired winding pattern of the induction coil. Since the induction coil is a cylindrical-spiral induction coil, the wire recess pattern is preferably also a spiral wire recess pattern.

[0038] In addition, the wire recess pattern allows to further reduce the radial distance between the induction coil and the susceptor location within the inner space of the induction coil. As already described above, the reduced radial distance leads to an increase in the magnetic field strength at the susceptor location, which in turn leads to an increase in the heating efficiency. Thus, for a given power level passing through the induction coil, the level of heat generated in the susceptor is increased, which in addition to the non-circular flattened cross-sectional shape of the outer circumference of the support tube further serves to reach the desired temperature level within a shorter period of time. The greater the depth of the recesses of the wire recess pattern, the better the magnetic field strength at the susceptor location within the inner space of the induction coil. For example, in case the coil wire has a circular cross section, the depth of the recesses of the wire recess pattern in the radial direction is preferably in the range between 0.2 and 0.8 times, in particular between 0.3 and 0.5 times, the diameter of the coil wire.

[0039] The outer periphery of the support tube may further include a flux concentrator recess for each of the annular protrusions of the flux concentrator, in which the radially inward end of the corresponding annular protrusion is received. Thereby, the annular protrusion is securely supported, which helps prevent the flux concentrator from being displaced. Otherwise, the displacement may cause an undesirable change in the inductance of the induction coil and an undesirable change in the magnetic field density in the inner space of the induction coil.

[0040] With regard to simple and cheap manufacturing, the coil support may comprise or may be made of plastic. In case the induction heating module has to comply with certain regulatory requirements, the coil support may comprise or may be made of bisphenol A-free plastic.

[0041] According to the invention, the heating device comprises power supply electronics comprising a DC / AC inverter connected to a DC power supply, wherein the DC / AC inverter comprises a switching power amplifier having at least one transistor switch, at least one transistor switch drive circuit associated with the transistor switch and an LC load network comprising at least a capacitor. In this regard, it has also been found that the use of a switching power amplifier is beneficial in obtaining good heating efficiency for a given limited power, in particular available from a DC power supply such as a battery.

[0042] Preferably, the switching power amplifier is a single-ended switching power amplifier, which is less complex than a power amplifier in a push-pull configuration.

[0043] In particular, a switching power amplifier may include a single transistor switch, which also makes the amplifier less complex.

[0044] Preferably, the switching power amplifier is one of a class C power amplifier, a class D power amplifier and a class E power amplifier.

[0045] In the case where the DC / AC inverter includes a class E power amplifier, the switching power amplifier may include the following components: a transistor switch, a transistor switch supply circuit for supplying a switching signal (gate-source voltage) to the transistor switch, and an LC load network including a shunt capacitor and a series connection of a capacitor and an inductor, wherein the inductor corresponds to an induction coil for generating an alternating magnetic field for induction heating. The transistor switch may include a field effect transistor T (FET), for example, a metal oxide semiconductor field effect transistor (MOSFET). In addition, the switching power amplifier may include a choke for supplying a DC power supply voltage from a DC power supply to the LC load network.

[0046] In the case where the DC / AC inverter comprises a class D power amplifier, the switching power amplifier may comprise the following components: two transistors connected to a DC power supply, two switching elements for switching the two transistors on and off, and an LC load network comprising a first capacitor and a series connection of a capacitor and an inductor, wherein the inductor corresponds to an induction coil for generating an alternating magnetic field for induction heating. The switching element is controllable / controlled at high frequencies in a manner to ensure that one of the two transistors has been switched off when the other of the two transistors is switched on. In addition, there may be a second capacitor arranged symmetrically to the first capacitor.

[0047] The aerosol generating device may comprise a device housing in which the induction heating device and the DC power supply are located or arranged.

[0048] The aerosol generating device, in particular the device housing, may comprise an insertion opening allowing access to the interior space of the induction coil or the interior space of the support tube of the induction heating module in order to enable insertion of an aerosol generating article therein.

[0049] The aerosol generating device may further comprise a receiving cavity for removably receiving at least the evaporated portion of the aerosol generating article. The receiving cavity may be located at least partially within the inner space of the induction coil or the inner space of the support tube (if present). In particular, the receiving cavity may be at least partially formed by the inner space of the induction coil or the support tube, in particular by the inner space of the support tube (if present). When the aerosol generating article is received in the receiving cavity, the induction coil may be arranged so as to surround at least a portion of the receiving cavity, in particular so as to surround at least the evaporated portion of the aerosol generating article.

[0050] The aerosol generating device may be configured to operate continuously following activation of the system, or intermittently, for example on a puff-by-puff basis.

[0051] The LC network may further comprise a shunt capacitor connected in parallel with the transistor switch.In addition, the DC / AC converter may comprise a choke inductor for supplying a DC supply voltage from a DC power source.

[0052] The aerosol generating device is preferably configured to generate a high frequency changing magnetic field. As mentioned herein, the high frequency changing magnetic field can have a frequency in the range between 500kHz (kilohertz) and 30MHz (megahertz), in particular between 5MHz (megahertz) and 15MHz (megahertz), preferably between 5MHz (megahertz) and 10MHz (megahertz).

[0053] The aerosol generating device may further comprise a controller configured to control the operation of the device. In particular, the controller may be configured to control the operation of the induction heating device, preferably in a closed-loop configuration, for controlling the heating of the aerosol-forming substrate to a predetermined operating temperature. Depending 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, the operating temperature may 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.

[0054] The controller may include a microprocessor, such as a programmable microprocessor, a microcontroller or an application specific integrated chip (ASIC), or other electronic circuitry capable of providing control. The controller may include further electronic components, in particular parts of a DC / AC inverter and / or a power amplifier. In particular, the induction heating module may be at least partially part of the controller.

[0055] The aerosol generating device may further comprise a puff detector, such as a microphone or a pressure sensor, for detecting a puff by a user, i.e. the start of the user experience when the user starts to puff on the device. The puff detector may be operatively connected to the controller. Thus, the occurrence of a puff detected by means of the puff detector may trigger the delivery of power to the induction coil for generating an aerosol. That is, the controller may be configured to start the operation of the heating device, in particular the generation of an alternating magnetic field, in response to the puff detector detecting the occurrence of a puff by the user.

[0056] According to the present invention, the DC power supply is configured to provide a DC supply voltage and a DC supply current to the induction heating device. Preferably, the DC power supply is a battery, such as a lithium iron phosphate battery. The DC power supply may have sufficient capacity to allow continuous generation of aerosol for a period of about six minutes or a multiple of six minutes. Likewise, the power supply may have sufficient capacity to allow a predetermined number of puffs or discontinuous activation of the induction heating device.

[0057] The present invention also relates to an aerosol generating system comprising an aerosol generating device according to the present invention and as described herein. The system also comprises an aerosol generating article for use with the aerosol generating device. The article comprises an aerosol-forming substrate and a flat susceptor, in particular a sheet-like susceptor, arranged in the evaporation portion of the article and configured for heating the aerosol-forming substrate by interaction of the susceptor with an alternating magnetic field provided by the aerosol generating device.

[0058] 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 invention and as described herein. In the system, the article and the device cooperate to generate an inhalable aerosol.

[0059] As used herein, the term "aerosol-generating article" refers to an article comprising at least one aerosol-forming substrate which releases volatile compounds that can form an aerosol when heated. Preferably, the aerosol-generating article is a heated aerosol-generating article. That is, the aerosol-generating article comprises at least one aerosol-forming substrate which is intended to be heated rather than burned in order to release volatile compounds that can form an aerosol. The aerosol-generating article may be a consumable, in particular a consumable that is to be discarded after a single use. Preferably, the article may comprise a liquid aerosol-forming substrate, i.e. an aerosol-forming liquid. Alternatively, the article may comprise a solid aerosol-forming substrate or a gel-like aerosol-forming substrate or a combination thereof.

[0060] As used herein, the term "aerosol-forming substrate" generally refers to a substrate formed by or including an aerosol-forming material, which can release volatile compounds when heated to generate an aerosol. The aerosol-forming substrate is intended to be heated rather than burned to release aerosol-forming volatile compounds. The aerosol-forming substrate can be a solid aerosol-forming substrate, a liquid aerosol-forming substrate, a gel-like aerosol-forming substrate or any combination thereof. Preferably, the aerosol-forming substrate is a liquid aerosol-forming substrate, i.e., an aerosol-forming liquid. The aerosol-forming liquid can contain both solid aerosol-forming materials or components and liquid aerosol-forming materials or components. The aerosol-forming substrate, particularly the aerosol-forming liquid, can include a tobacco-containing material comprising volatile tobacco flavor compounds, which are released from the substrate when heated. Alternatively or in addition, the aerosol-forming substrate, particularly the aerosol-forming liquid, can include non-tobacco materials. The aerosol-forming substrate, particularly the aerosol-forming liquid, can also include an aerosol-forming agent. The example of suitable aerosol forming agent is glycerol and propylene glycol. Aerosol forming substrate, particularly aerosol forming liquid can also contain other additives and ingredients, such as nicotine or spices. In particular, aerosol forming liquid can include water, solvent, ethanol, plant extract and natural or artificial flavoring agent. Aerosol forming liquid can be water-based aerosol forming liquid or oil-based aerosol forming liquid. Aerosol forming substrate can also be a pasty material, including a porous material pouch of aerosol forming substrate, or for example loose tobacco mixed with a gelling agent or a tackifier, which can include common aerosol forming agents such as glycerol, and be compressed or molded into a rod.

[0061] As used herein, the term "susceptor" refers to an element capable of converting electromagnetic energy into heat when subjected to a changing magnetic field. This may be the result of at least one of hysteresis losses or eddy currents induced in the susceptor, depending on the electrical and magnetic properties of the susceptor material. In a ferromagnetic or ferrimagnetic susceptor, hysteresis losses occur due to the transformation of magnetic domains within the susceptor material under the influence of a changing magnetic field. If the susceptor is electrically conductive, eddy currents may be induced. In the case of an electrically conductive ferromagnetic or ferrimagnetic susceptor, heat may be generated due to both eddy currents and hysteresis losses.

[0062] Thus, the susceptor may be formed from any material that can be inductively heated to a temperature sufficient to generate an aerosol from the aerosol-forming substrate. Preferred susceptors include metal or carbon. Preferred susceptors may include ferromagnetic materials, such as ferritic iron or ferromagnetic steel or stainless steel. Suitable susceptors may be or include aluminum. Preferred susceptors may be made from 400 series stainless steel, such as 410 grade or 420 grade or 430 grade stainless steel.

[0063] The susceptor may comprise various geometric configurations depending, inter alia, on the type of aerosol-forming substrate.

[0064] A flat susceptor, in particular a sheet-like susceptor, may comprise or be a susceptor blade, a susceptor strip or a susceptor plate.In particular, where the substrate is a liquid, ie an aerosol-forming liquid, the susceptor may comprise or be a mesh-like susceptor.

[0065] In any of these configurations, the susceptor is advantageously capable of performing two functions: wicking (transport) and heating the aerosol-forming liquid. Thus, in any of the foregoing configurations, the susceptor may be considered a liquid transport susceptor.

[0066] Where the aerosol-forming substrate is a liquid substrate, the article may comprise a liquid reservoir for storing the aerosol-forming liquid. Preferably, the susceptor is in fluid communication with the liquid reservoir in which the aerosol-forming liquid is stored.

[0067] Further features and advantages of the aerosol generating system have been described in relation to the induction heating module and aerosol generating device of the present invention and are equally applicable.

[0068] As used herein, the terms "radial" and "axial" refer to the cylindrical geometry of a cylindrical induction coil.

[0069] The invention is defined in the claims. However, a non-exhaustive list of non-limiting examples is provided below. Any one or more features of these examples may be combined with any one or more features of another example, embodiment or aspect described herein.

[0070] Example Ex1: An induction heating aerosol generating device for use with an aerosol generating article, the article comprising an aerosol-forming substrate and a flat susceptor, in particular a sheet-like susceptor, the susceptor being arranged in an evaporation portion of the article and configured to heat the aerosol-forming substrate by interaction of the susceptor with an alternating magnetic field provided by the aerosol generating device, wherein the device comprises a DC power supply and an induction heating device, the heating device comprising power supply electronics, the power supply electronics comprising a DC / AC inverter connected to the DC power supply, wherein the DC / AC inverter comprises a switching power amplifier , the switching power amplifier has at least one transistor switch, at least one transistor switch driving circuit associated with the transistor switch, and an LC load network including at least a capacitor and a cylindrical-spiral induction coil, wherein the internal space of the induction coil is configured to removably receive at least the evaporation portion of the aerosol generating article, wherein the cylindrical-spiral induction coil has a non-circular flattened cross-sectional shape, the non-circular flattened cross-sectional shape includes two relative flat sections connected by two relative at least partially curved sections, in particular, consists of two relative flat sections connected by two relative at least partially curved sections.

[0071] Example Ex2: The induction heating device according to example Ex1, wherein the non-circular flattened cross-sectional shape includes a short axis of symmetry and a long axis of symmetry.

[0072] Example Ex3: An induction heating device according to Example Ex2, wherein the ratio of the maximum distance between the two opposite at least partially curved sections along the long symmetry axis to the maximum distance between the two opposite flat sections along the short symmetry axis is in the range between 1.2 and 3, in particular between 1.5 and 2.5.

[0073] Example Ex4: The induction heating device according to any one of Examples Ex2 or Ex3, wherein the maximum distance between the two opposing flat sections along the short symmetry axis is in the range between 4 mm and 7 mm, in particular between 5 mm and 6 mm.

[0074] Example Ex5: The induction heating device according to any one of Examples Ex2 to Ex4, wherein the maximum distance between the two opposing at least partially curved sections along the long symmetry axis is in the range between 7 mm and 10 mm, in particular between 8 mm and 9 mm.

[0075] Example Ex6: The induction heating device according to any one of the preceding examples, wherein the two opposing flat sections are parallel to each other.

[0076] Example Ex7: The induction heating device according to any of the preceding examples, wherein each of the two opposing flat sections is a substantially straight line.

[0077] Example Ex8: The induction heating device according to any of the preceding examples, wherein each of the two opposing at least partially curved sections is substantially semicircular, substantially semi-oval, substantially semi-elliptical or substantially parabolic.

[0078] Example Ex9: The induction heating device according to any of the preceding examples, wherein the non-circular flattened cross-sectional shape of the induction coil is oblong.

[0079] Example Ex10: The induction heating device according to any of the preceding examples, wherein the induction coil has a cylindrical oblong shape.

[0080] Example Ex11: The induction heating device according to any of the preceding examples, wherein the induction coil is formed by one or more turns of a coil wire, the coil wire having a circular cross-section.

[0081] Example Ex12: The induction heating device according to any one of the preceding examples, wherein the switching power amplifier is a single-ended switching power amplifier.

[0082] Example Ex13: The induction heating device according to any one of the preceding examples, wherein the switching power amplifier is one of a class C power amplifier, a class D power amplifier, and a class E power amplifier.

[0083] Example Ex14: The induction heating device according to any of the preceding examples, wherein the induction heating device is configured to generate an alternating magnetic field in a range between 500 kHz and 30 MHz, in particular between 5 MHz and 15 MHz, preferably between 5 MHz and 10 MHz.

[0084] Example Ex15: An aerosol generating system, comprising an aerosol generating device according to any of the preceding examples and an aerosol generating article for use with the aerosol generating device, the article comprising an aerosol-forming substrate and a flat receptor, in particular a sheet-shaped receptor, the receptor being arranged in an evaporation part and configured to heat the aerosol-forming substrate by interaction between the receptor and an alternating magnetic field provided by the aerosol generating device.

[0085] Several examples will now be further described with reference to the accompanying drawings, in which:

[0086] Figure 1 An exemplary embodiment of an aerosol generating system according to the invention is shown in longitudinal cross-section;

[0087] Figure 2 Shown according to Figure 1 Detailed longitudinal cross-section of an aerosol generating system;

[0088] Figure 3 The perspective longitudinal section shows the Figure 1 details of the aerosol generating system;

[0089] Figure 4 Shown is the Figure 1 Details of a coil support in an aerosol generating device;

[0090] Figure 5 Shown is the Figure 1 Details of the induction heating device in the aerosol generating device;

[0091] Figure 6 Shown is the Figure 1 Further details of a coil support in an aerosol generating device of;

[0092] Figure 7 shows that it can be used according to Figure 1 Details of a first embodiment of power electronics in an aerosol generating device; and

[0093] Figure 8 shows an alternative for use according to Figure 1 Details of a second embodiment of power supply electronics for an aerosol generating device.

[0094] Figure 1-3 A schematic cross-sectional view of an aerosol generating system 1 according to an exemplary embodiment of the present invention is shown. The system 1 is configured to generate an inhalable aerosol by inductively heating a susceptor in thermal contact with a liquid aerosol-forming substrate 25, which is hereinafter also indicated as aerosol-forming liquid 25. The system 1 comprises two main components: an aerosol-generating article 2 and an aerosol-generating device 1 for use with the article 2. While the article 2 comprises a susceptor 22 and an aerosol-forming liquid 25 to be heated, the device 1 comprises a receiving cavity 16 for receiving the article 2, and an inductive heating device 10 configured to generate an alternating magnetic field for inductively heating the susceptor 22 and, thus, for vaporizing the aerosol-forming liquid 25 within the article when the article 2 is inserted into the cavity 16 of the device 1.

[0095] refer to Figure 1, which shows the device 1 and the article 2 separated from each other, the aerosol generating device 1 comprises a substantially strip-shaped body with a substantially cylindrical device housing 15. In the distal part 4, the device 1 comprises a power source 12, such as a lithium-ion battery, and a circuit system 11, which comprises a controller 160 for controlling the operation of the device 1, in particular for controlling the heating process. In the proximal part 5 opposite to the distal part 4, the device 1 comprises a receiving cavity 16 and at least part of the induction heating device 10. The receiving cavity 16 is an open-ended cavity, which comprises an insertion opening 19 at the proximal end of the device 1, so that the article 2 can be inserted into the receiving cavity 16.

[0096] The induction heating device 10 includes an induction coil 13 for generating an alternating magnetic field in a cavity 16. The induction coil 13 is a cylindrical-spiral coil circumferentially surrounding the cylindrical receiving cavity 16. In the present embodiment, the induction coil 13 has an axial length of about 8 mm and is formed by a single layer of 4.25 turns of coil wire having a circular cross-section. The turns of the induction coil 13 extend along the length extension of the cavity 16. Preferably, there is a gap between adjacent turns of the induction coil 13. That is, the pitch of the spiral induction coil 13 can be greater than the diameter of the coil wire. Therefore, the coil wires of adjacent turns do not contact each other, which allows the use of coil wires without wire insulation. However, the coil wire in the present embodiment is an enamel-coated copper wire with a diameter of 1.1 mm. In addition, the gap between adjacent turns of the induction coil is used for better heat dissipation, and thus the resistive power loss in the coil winding is smaller. In the present embodiment, the (center-to-center) distance between adjacent parts of the coil wires of adjacent turns is about 1.1 times the diameter of the coil wire. These ranges have been shown to provide a sufficiently large distance (which still allows a compact coil design), ie a sufficiently large number of turns per length unit.

[0097] The induction coil 13 is a part of the induction module 30. In addition to the induction coil 13, the induction module also includes a coil support 17 arranged in the device housing 15 for supporting the induction coil 13. The details of the coil support 17 are shown in FIG. Figure 4 The coil support 17 comprises a cylindrical support tube 32 and a circumferential collar 33 at each axial end of the support tube 32. The distal collar 33 comprises a recess or feed-through opening 34 for passing a connecting lead 60 to the induction coil 13, such as Figure 5 As shown in Figure 1-3It can be seen that the inner space of the support tube 32 at least partially forms the receiving cavity 16 of the device 1 for removably receiving at least a portion of the aerosol generating article 2. That is, the inner surface along the inner circumference of the support tube 32 forms at least a portion of the inner surface of the receiving cavity 16. Regarding simple and cheap manufacturing, the coil support 17 can be made of plastic. In the case where the induction heating module 30 must comply with specific regulatory requirements, the coil support 17 can be made of bisphenol A-free plastic, for example.

[0098] In addition to the induction coil 13, the induction heating device 10 comprises power supply electronics which can be at least partially integrated in the circuit system 11 and connected via the connecting pads 131 (see Figure 1 ) is coupled to the induction coil 13. In conjunction with the induction coil 13, the power supply electronics are used to generate a high frequency alternating current through the induction coil 13, which causes the induction coil 31 to generate a high frequency changing magnetic field within the interior space of the induction coil 12 and thus within the cavity 16, such as Figure 2 The frequency of the high-frequency changing magnetic field may be in the range between 500kHz (kilohertz) and 30MHz (megahertz), in particular between 5MHz (megahertz) and 15MHz (megahertz), preferably between 5MHz (megahertz) and 10MHz (megahertz). As will be described in more detail below, the alternating magnetic field is used to induce at least one of heat-generating eddy currents or hysteresis losses in the susceptor 22 of the article 2 so as to vaporize the aerosol-forming liquid 25 contained in the article 2.

[0099] Next to device 1, Figure 1 Details of the aerosol-generating article 2 are also shown. In this embodiment, the article 2 is a cartridge having a mushroom-type shape that can be coupled to the device 1. At the distal end, the article 2 comprises an elongated evaporation portion 29 configured to be inserted into the receiving cavity 16 of the device 1, as shown in FIG. Figure 2 and Figure 3 In the evaporation portion 29, the article 2 includes a susceptor 22, which is arranged in the article 2 so that when the evaporation portion 29 of the article 2 is inserted into the cavity 16, the susceptor 22 is located in the inner space of the induction coil 13. Therefore, the susceptor 22 can experience the alternating magnetic field generated by the induction coil 13 during the operation of the heating device 10 so as to be heated.

[0100] In the present embodiment, the susceptor 22 is a flat sheet mesh made of ferromagnetic stainless steel that can be inductively heated. Therefore, the susceptor 22 can also be represented as a sheet mesh susceptor 22 that can perform two functions: wicking (transporting) and heating the aerosol-forming liquid 25. Since the material of the susceptor 22 at hand is conductive and magnetic, the alternating electromagnetic field of the induction coil 13 can induce both heat-generating eddy currents and hysteresis losses in the susceptor material.

[0101] The susceptor web 22 is in fluid communication with the aerosol-forming liquid 25 contained in the reservoir 24 of the article 2 by means of a wicking porous element 28. The wicking porous element 28 is in direct contact with the liquid 25 in the reservoir 24 and is configured to transport the liquid 25 to the mesh susceptor 22. Thus, the susceptor web 22 is continuously humidified. Figure 2 and Figure 3 ) and the heating device 10 is activated, the mesh susceptor 22 is heated until a temperature sufficient to vaporize the aerosol-forming liquid 25 in contact with the mesh susceptor 22 is reached.

[0102] As especially in Figure 1 As can be further seen in the figure, the mesh susceptor 22 is arranged in an air flow channel 26 passing through the article 2 along its central axis. The air flow channel 26 has an air inlet at the distal end of the article 2 and an outlet at the proximal end of the article 2: the outlet is formed by the mouthpiece 21, on which the user can draw. Thus, when the user draws at the mouthpiece 21 when using the system, air is entrained into the air flow channel 26 via the air inlet and passes along the mesh susceptor 22. There, vaporized material of the aerosol-forming liquid is entrained into the air flow through the air flow channel 26. Subsequently, when passing further downstream in the air flow channel 26 towards the mouthpiece 21, the air flow comprising the vaporized material cools so as to form an aerosol that escapes the article 2 through the outlet at the mouthpiece 21.

[0103] The aerosol generating device 1 according to the present embodiment further comprises a puff detector 14 for detecting a user's puff. The puff detector 14 is operatively connected to the power supply electronics so that the occurrence of a puff detected by means of the puff detector 14 triggers the delivery of power to the induction coil 13 for generating an aerosol. In this regard, the aerosol generating device 1 according to the present embodiment can be represented as an on-demand puff device. Once the user stops puffing, the power delivery to the induction coil is interrupted so that unnecessary unused aerosol is not generated. That is, the induction heating device operates intermittently according to the needs of the user.

[0104] While in a continuous mode of operation the susceptor will be permanently maintained at a temperature level sufficient to form a satisfactory amount of aerosol, if the heating device is to be operated intermittently, for example according to user demand (puff on demand), achieving sufficient temperature levels within short periods of time may be a challenge.

[0105] In order to achieve a higher heating efficiency, in particular to reach a sufficient temperature level in a shorter period of time, it has been found that with respect to the flat sheet-like shape of the susceptor 22, it is advantageous to adapt the geometry of the magnetic field within the inner space of the induction coil 13, where the susceptor 22 is to be placed, to the flat shape of the susceptor 22. In particular, it has been found that by making the cross-sectional shape of the induction coil 13 flat, the radial distance between the induction coil 13 and the main surface of the flat susceptor 22 can be reduced. The reduced radial distance leads to an increase in the magnetic field strength at the location of the susceptor, which in turn leads to an increase in the heating efficiency. Thus, for a given power level passing through the induction coil, the level of heat generated in the susceptor is increased, which in particular allows to reach the desired temperature level in a shorter period of time. Therefore, in the present embodiment, the outer circumference of the support tube 32 has a non-circular flattened cross-sectional shape (see Figure 4 ), the non-circular flattened cross-sectional shape is composed of two opposite flat sections 32.1 connected by two opposite at least partially curved sections 32.2. Since the induction coil 13 is wound around the outer circumference of the support tube 32, the cross-sectional shape of the induction coil 13 follows the non-circular flattened cross-sectional shape of the outer circumference of the support tube 32. That is, the cylindrical-spiral induction coil 13 also has a non-circular flattened cross-sectional shape (see Figure 5 ), the non-circular flattened cross-sectional shape consists of two opposing flat sections 13.1 connected by two opposing at least partially curved sections 13.2.

[0106] In this embodiment, the non-circular flattened cross-sectional shape of the support tube 32 and the induction coil 13 is an oblong shape, which is a shape consisting of two semicircles 13.2, 32.2 connected by parallel lines 13.1, 32.1 tangent to their end points. Therefore, the induction coil 13 and the support tube 17 have an oblong-cylindrical shape.

[0107] Due to the parallel and semicircular portions of the oblong shape, the non-circular flattened cross-sectional shape of the induction coil 13 and the support tube 32 includes a short symmetry axis and a long symmetry axis. Figure 5 As indicated on the middle right by the dash-dotted arrow about the induction coil 13, the short symmetry axis extends between two opposing flat sections 13.1 of the induction coil 13, while the long symmetry axis extends between two opposing curved sections 13.2 of the induction coil. Preferably, the ratio of the maximum distance between two opposing at least partially curved sections 13.2, 32.2 along the long symmetry axis to the maximum distance between two opposing flat sections 13.1, 32.1 along the short symmetry axis is in the range between 1.2 and 3, in particular between 1.5 and 2.5. These ratios are particularly advantageous in terms of a proper matching between the geometry of the magnetic field and the flat shape of the susceptor 22 to be heated.

[0108] In order to further improve the heating efficiency, the induction heating device 10 of the present embodiment includes a flux concentrator 50, which is arranged around the induction coil 13 and configured to distort the alternating magnetic field of the induction heating device 10 toward the inner space of the induction coil 13 during use. To this end, the flux concentrator 50 has a specific configuration, which includes a sleeve portion 52 circumferentially surrounding the induction coil 13, and further includes an annular protrusion portion 51 protruding radially inwardly beyond the sleeve portion 51 at each axial end of the sleeve portion 52, so that the induction coil 13 is axially arranged between the annular protrusion portions 51, such as particularly at Figure 1 and Figure 2 Thus, as seen in a longitudinal section through the flux concentrator 50 along the length axis of the induction coil 13 (see Figure 1 and Figure 2 ), the flux concentrator 50 has a U-shape or C-shape, wherein the sleeve portion 52 is part of the base of the U-shape or C-shape, and the annular protrusion portion 51 is part of the arm or leg of the U-shape or C-shape. In this regard, it has been found that by distorting the magnetic field toward the interior space of the induction coil 13 using the flux concentrator 50 shaped as described above, the density of the magnetic field at the location of the susceptor 22 can be increased. In particular, the annular protrusion portion 51 protruding radially inwardly beyond the sleeve portion 52 at each axial end of the sleeve portion 52 causes the magnetic field to be concentrated or focused within the interior space of the induction coil 13. Therefore, the level of heat generated in the susceptor 22 for a given power level passing through the induction coil 13 is increased compared to an induction coil without a flux concentrator or only a sleeve-shaped flux concentrator without an annular protrusion portion at each axial end. In addition to this, the flux concentrator 50 acts as a magnetic shield that can reduce the extent to which the magnetic field propagates beyond the induction coil 13. Thus, the flux concentrator 50 may help reduce undesired heating of other sensitive portions of the system or sensitive items external to the apparatus 1 .

[0109] Although the annular protrusion 51 should extend radially inward beyond the outer circumference of the induction coil 13 in order to ensure sufficient concentration of the magnetic field, it may be sufficient if the annular protrusion 51 extends radially inward at most to the inner circumference of the induction coil 13, that is, if the annular protrusion does not protrude radially inward beyond the inner circumference of the induction coil 13.

[0110] In the present embodiment, the flux concentrator 50 is constructed of a flux concentrator foil. More specifically, each of the annular protrusions 51 is made of a flux concentrator foil that is spirally wound in multiple layers on the coil support 17 so as to extend radially outward beyond the circumference of the induction coil 13. On top of the annular protrusions 51, a sleeve portion 52 is formed of several layers of the same flux concentrator foil material so as to surround the induction coil 13 and each of the annular protrusions 51. By way of example, a flexible three-layer ferrite sheet comprising a ferrite layer sandwiched between an adhesive layer and a cover layer can be used as the flux concentrator foil, which is available from Laird Company under the product name MHLL6060-300. MHLL6060-300 has a foil thickness of about 90 microns, a real magnetic permeability of about 130 at a frequency of 13.56 MHz, and an imaginary magnetic permeability of about 5. On hand, Figure 1-3 Each of the annular protrusions 51 shown in the figure has a height dimension of 2 mm (in the radial direction) and a width dimension of 2 mm (in the axial direction). The sleeve portion 52 has a thickness dimension of about 180 microns (in the radial direction) and a width dimension of 10 mm (in the axial direction). Therefore, using a foil material with a foil thickness of 90 microns requires about 22 windings to form an annular protrusion 51 with a height of 2 mm, and requires about 2 windings to form a sleeve portion 52 with a thickness of 180 microns.

[0111] The sleeve portion 52 is spaced apart from the induction coil 13 in the radial direction by a radial gap having a width (radial extension) in the range between 0.5 mm and 1.5 mm, in particular between 0.8 mm and 1 mm. Advantageously, the radial gap may help avoid heat loss from the induction coil to the sleeve portion to reduce losses in the induction coil and increase losses in the susceptor 22 to be heated, i.e., increase the heating efficiency of the aerosol generating device 1. Likewise, each of the annular protruding portions 51 is spaced apart from the induction coil 13 in the axial direction by an axial gap. The radial gap and / or the axial gap may be an air gap or a gap at least partially filled with a filling material.

[0112] Similar to the support tube 32 and the induction coil 13, the flux concentrator 50 may also have a non-circular flattened cross-sectional shape corresponding to the non-circular flattened cross-sectional shapes of the support tube 32 and the induction coil 13. In particular, the cross-sectional shape of the flux concentrator 50 may be oblong.

[0113] like Figure 6As shown in FIG, the more distal annular protruding portion 51 comprises a recess or feed-through opening 501 for passing a connecting lead 60 for the induction coil. The recess or feed-through opening 501 may be cut into the annular protruding portion 51 after winding the flux concentrator foil.

[0114] In order to further improve the heating efficiency, the outer periphery of the support tube 32 of this embodiment includes a spiral wire concave pattern 39, such as Figure 4 and Figure 6 , the coil wire is received in said spiral wire recess pattern. Advantageously, the wire recess pattern 39 allows a further reduction in the radial distance between the induction coil 13 and the susceptor location within the interior space of the induction coil 13. As already described above, the reduced radial distance results in an increase in the magnetic field strength at the susceptor location, which in turn results in an increase in the heating efficiency.

[0115] The greater the depth of the recesses of the wire recess pattern 39, the better the magnetic field strength at the susceptor position in the internal space of the induction coil 13. For example, in the case where the coil wire has a circular cross-section, the depth of the recesses of the wire recess pattern 39 in the radial direction is preferably in the range between 0.2 and 0.8 times, particularly between 0.3 and 0.5 times, the diameter of the coil wire. Figure 6 As indicated in FIG. 1 , the distance between the induction coil 13 and the inner periphery of the coil support 17 in the radial direction may be in the range of 0.1 mm to 1 mm, in particular, 0.2 mm to 0.5 mm, preferably about 0.3 mm. This ensures a specific short radial distance between the induction coil 13 and the inner space of the susceptor 22 to be received of the support tube 32. That is, the distance between the inner periphery of the support tube 32 and the bottom of the recessed pattern 39 in the radial direction is in the range of 0.1 mm to 1 mm, in particular, 0.2 mm to 0.5 mm, preferably about 0.3 mm.

[0116] like Figure 2 and Figure 6 As shown in , the outer circumference of the support tube 32 may further include a flux concentrator recess 38 for each of the annular protrusions 51 of the flux concentrator 50, in which the radially inward end of the corresponding annular protrusion 51 is received. Thus, the annular protrusions 51 are securely supported, which helps prevent the flux concentrator 50 from being displaced. Otherwise, the displacement may cause an undesirable change in the inductance of the induction coil 13 and an undesirable change in the magnetic field density in the internal space of the induction coil 13.

[0117] Figure 7 Shows the available Figure 1-3Further details of the induction heating device 10, in particular the power supply electronics, in the aerosol generating device shown in FIG. According to the present embodiment, the induction heating device 10 comprises a DC / AC inverter connected to Figure 1 The DC power supply 12 shown in FIG. The DC / AC inverter includes a class E power amplifier, which in turn includes the following components: a transistor switch 111, which includes a field effect transistor T (FET), such as a metal oxide semiconductor field effect transistor (MOSFET); a transistor switch supply circuit, which is indicated by an arrow 112, for supplying a switching signal (gate-source voltage) to the transistor switch 111; and an LC load network 113 including a shunt capacitor C1 and a series connection of a capacitor C2 and an inductor L2. The inductor L2 corresponds to Figure 1-3 The induction coil 13 shown in FIG. 1 is used to generate an alternating magnetic field in the cavity 16. In addition, a choke L1 for supplying a DC power supply voltage +V_DC from the DC power supply 12 is provided. Figure 7 Also shown is an ohmic resistance R representing a total equivalent resistance or total resistive load 114, which is the sum of the ohmic resistance of the induction coil 13, referenced L2, and the ohmic resistance of the susceptor 22 when the system is in use, i.e. when the product 2 is inserted into the cavity 16 of the device 1. Otherwise, in the case where no product is inserted into the cavity 16, the equivalent resistance or resistive load 114 corresponds only to the ohmic resistance of the induction coil 13.

[0118] Figure 8 Another embodiment of a power supply electronic device is shown, which can alternatively be used for Figure 1-3 In the aerosol generating device shown in , a high-frequency oscillating current is provided to the induction coil 13 . Figure 8 The configuration shown in corresponds to the configuration of a class D amplifier. There, a DC power supply 12 is connected to two transistors 1210, 1212. Two switching elements 1220, 1222 are provided for switching the two transistors 1210, 1212 on and off. The switching elements 1220, 1222 are controlled at high frequency in a way so as to ensure that one of the two transistors 1210, 1212 has been switched off when the other of the two transistors is switched on. The induction coil 13 for generating an alternating magnetic field for induction heating is again indicated by L2, while the combined ohmic resistance of the induction coil 13 and the susceptor 22 is indicated by R, the values ​​of C1 and C2 being selected to maximize the efficient dissipation of power in the susceptor element. The capacitor C1 is not necessary for configuring the architecture as class D and can therefore be omitted.

[0119] For the purpose of this specification and the appended claims, unless otherwise indicated, all numbers representing amounts, quantities, percentages, etc. should be understood to be modified by the term "about" in all cases. Moreover, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges therein that may or may not be specifically listed herein. Therefore, in this context, the number A is understood to be A±5%A. In this context, the number A can be regarded as including a value within the general standard error for the measurement of the attribute modified by the number A. In certain cases used in the appended claims, the number A may deviate from the percentages listed above, provided that the amount of A deviation does not substantially affect the basic features and novel features of the invention claimed for protection. Moreover, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges therein that may or may not be specifically listed herein.

Claims

1. An aerosol generating system, comprising an aerosol generating article and an induction heating aerosol generating device for use with the aerosol generating article, the article comprising an aerosol-forming liquid and a flat susceptor, in particular a sheet-like susceptor, arranged in an evaporation portion of the article and configured for heating the aerosol-forming liquid by interaction of the susceptor with an alternating magnetic field provided by the aerosol generating device, wherein the device comprises a DC power supply and an induction heating device, the heating device comprising power supply electronics, the power supply electronics comprising a DC / AC inverter connected to the DC power supply, wherein the DC / AC The inverter includes a switching power amplifier having at least one transistor switch, at least one transistor switch drive circuit associated with the transistor switch, and an LC load network including at least a capacitor and a cylindrical-spiral induction coil, wherein the internal space of the induction coil is configured to removably receive at least a vaporized portion of the aerosol generating article, wherein the cylindrical-spiral induction coil has a non-circular flattened cross-sectional shape, and the non-circular flattened cross-sectional shape includes two relative flat sections connected by two relative at least partially curved sections, and in particular consists of two relative flat sections connected by two relative at least partially curved sections.

2. An aerosol generating system according to claim 1, wherein the non-circular flattened cross-sectional shape comprises a short axis of symmetry and a long axis of symmetry.

3. An aerosol generating system according to claim 2, wherein the ratio of the maximum distance between the two relative at least partially curved segments along the long axis of symmetry to the maximum distance between the two relative flat segments along the short axis of symmetry is in the range between 1.2 and 3, in particular between 1.5 and 2.

5.

4. An aerosol generating system according to any one of claims 2 or claim 3, wherein the maximum distance between the two opposing flat sections along the short axis of symmetry is in the range between 4 mm and 7 mm, in particular between 5 mm and 6 mm.

5. An aerosol generating system according to any one of claims 2 to 4, wherein the maximum distance between the two opposing at least partially curved segments along the long axis of symmetry is in the range between 7 mm and 10 mm, in particular between 8 mm and 9 mm.

6. An aerosol generating system according to any one of the preceding claims, wherein the two opposing planar sections are parallel to each other.

7. An aerosol generating system according to any one of the preceding claims, wherein each of the two opposing flat sections is a substantially straight line.

8. An aerosol generating system according to any one of the preceding claims, wherein each of the two opposing at least partially curved sections is substantially semi-circular, substantially semi-oval, substantially semi-elliptical or substantially parabolic.

9. An aerosol generating system according to any one of the preceding claims, wherein the non-circular flattened cross-sectional shape of the induction coil is oblong.

10. An aerosol generating system according to any one of the preceding claims, wherein the induction coil has a cylindrical oblong shape.

11. An aerosol generating system according to any one of the preceding claims, wherein the induction coil is formed from one or more turns of coil wire, the coil wire having a circular cross-section.

12. An aerosol generating system according to any preceding claim, wherein the switching power amplifier is a single-ended switching power amplifier.

13. An aerosol generating system according to any one of the preceding claims, wherein the switching power amplifier is one of a class C power amplifier, a class D power amplifier and a class E power amplifier.

14. An aerosol generating system according to any one of the preceding claims, wherein the induction heating device is configured to generate an alternating magnetic field in the range between 500 kHz and 30 MHz, in particular between 5 MHz and 15 MHz, preferably between 5 MHz and 10 MHz.

15. An aerosol generating system according to any one of the preceding claims, wherein the flat susceptor is positioned so that when the vaporized portion of the aerosol generating article is received in the interior space of the induction coil, a major surface of the flat susceptor is aligned with two opposing flat sections of the cross-sectional shape of the induction coil.

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