Induction heating assembly for inductively heating aerosol-forming substrate

Abstract

The present invention relates to an induction heating assembly configured to inductively heat an aerosol-forming substrate to a predetermined operating temperature. The heating assembly includes an inductive source configured to generate an alternating electromagnetic field. The heating assembly also includes a susceptor assembly for inductively heating the aerosol-forming substrate under the influence of an alternating magnetic field generated by an inductive source. The susceptor assembly includes a first susceptor having a first susceptor material and a second susceptor. The second susceptor includes a second susceptor material having a Curie temperature at least 20 degrees Celsius lower than an operating temperature of the heating assembly. The invention also relates to an aerosol-generating device and an aerosol-generating system comprising the induction heating assembly.

Description

[0001] This application is a divisional application of the invention patent application entitled "Induction heating component for induction heating aerosol forming substrate", with an international application date of September 24, 2019, an international application number of PCT / EP2019 / 075630, and a national application number of 201980062541.8. Technical Field

[0002] The present invention relates to an induction heating assembly for inductively heating an aerosol-forming substrate. The present invention also relates to an aerosol generating device and an aerosol generating system comprising such an induction heating assembly. Background Art

[0003] Aerosol generating systems based on inductive heating of an aerosol-forming substrate capable of forming an inhalable aerosol upon heating are generally known in the prior art. In order to heat the aerosol-forming substrate, such a system may include an inductive heating component, which includes an induction source and a susceptor. The induction source is configured to generate an alternating electromagnetic field that induces at least one of thermal eddy currents and / or hysteresis losses in the susceptor. Although the induction source is typically part of the aerosol generating device, the susceptor may be part of the device, or an integral part of an aerosol generating article that is configured to be received in an aerosol generating device including the induction source. In either case, the susceptor is arranged to be in such thermal proximity or direct physical contact with the substrate during operation of the system.

[0004] In order to control the temperature of a substrate, a susceptor assembly has been proposed, which comprises a first susceptor and a second susceptor made of different materials. The first susceptor material is optimized in terms of heat loss and therefore heating efficiency. In contrast, the second susceptor material serves as a temperature marker. To this end, the second susceptor material is selected so as to have a Curie temperature corresponding to a predetermined operating temperature of the susceptor assembly. At its Curie temperature, the magnetic properties of the second susceptor change from ferromagnetism or ferrimagnetism to paramagnetism, accompanied by a temporary change in its electrical resistance. Therefore, by monitoring the corresponding change in the current absorbed by the induction source, it is possible to detect when the second susceptor material has reached its Curie temperature, and therefore when the predetermined operating temperature has been reached.

[0005] However, when monitoring the change in the current absorbed by the inductive source, it may be difficult to distinguish between the situation when the second susceptor material has reached its Curie temperature and the situation when the user takes a puff (particularly the first puff), during which the current shows similar characteristic changes. The change in current during the user's puff is due to the cooling of the susceptor component caused by air being drawn through the aerosol-generating article when the user puffs. The cooling causes a temporary change in the resistance of the susceptor component. This in turn causes a corresponding change in the current absorbed by the inductive source. Typically, during the user's puff, the cooling of the susceptor component is offset on the controller side by a temporary increase in the heating power. However, if the monitored current change (which is actually due to the second susceptor material reaching the Curie temperature) is mistakenly identified as a puff by the user, this temporary increase in heating power caused by the controller may disadvantageously lead to undesirable overheating of the susceptor component.

[0006] Therefore, it is desirable to have an induction heating assembly having the advantages of prior art solutions without having their limitations. In particular, it is desirable to have an induction heating assembly capable of improved temperature control. Summary of the invention

[0007] According to the present invention, there is provided an induction heating assembly configured for inductively heating an aerosol-forming substrate to a predetermined operating temperature. The heating assembly comprises an induction source configured to generate an alternating electromagnetic field. The heating assembly further comprises a susceptor assembly for inductively heating the aerosol-forming substrate under the influence of the alternating magnetic field generated by the induction source. The susceptor assembly comprises a first susceptor having a first susceptor material and a second susceptor. The second susceptor comprises a second susceptor material having a Curie temperature at least 20 degrees Celsius lower than the operating temperature of the heating assembly.

[0008] According to the present invention, it has been recognised that a temperature difference of at least 20 degrees between the Curie temperature of the second susceptor material and the operating temperature of the heating assembly is large enough to reliably use the Curie temperature of the second susceptor material as a temperature marker to control the heating temperature of the aerosol-forming substrate without the risk of being misinterpreted as a puff by a user.

[0009] Preferably, the Curie temperature of the second susceptor material is at least 50 degrees Celsius, in particular at least 100 degrees Celsius, preferably at least 150 degrees Celsius, most preferably at least 200 degrees Celsius below the operating temperature. Advantageously, increasing the temperature difference between the Curie temperature of the second susceptor material and the operating temperature of the heating assembly can improve the correct recognition of the temperature signature, thereby increasing the reliability of the temperature control.

[0010] The predetermined operating temperature may be at least 300 degrees C, in particular at least 350 degrees C, preferably at least 370 degrees C, most preferably at least 400 degrees C. These temperatures are typical operating temperatures for heating but not burning an aerosol-forming substrate.

[0011] Therefore, the second susceptor material is preferably selected such that its Curie temperature is below 350 degrees Celsius, in particular below 300 degrees Celsius, preferably below 250 degrees Celsius, most preferably below 200 degrees Celsius. These values ​​are well below typical operating temperatures for heating aerosol-forming substrates. Thus, correct identification of the temperature signature is ensured.

[0012] As used herein, the term "susceptor" refers to an element that is capable of converting electromagnetic energy into heat when subjected to an alternating electromagnetic field. This may be the result of hysteresis losses and / 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 magnetic domains within the material being switched under the influence of the alternating electromagnetic 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.

[0013] According to the invention, the second susceptor material is at least ferrimagnetic or ferromagnetic with a specific Curie temperature. The Curie temperature is the temperature at which a ferrimagnetic or ferromagnetic material loses its ferrimagnetism or ferromagnetism, respectively, and becomes paramagnetic. In addition to being ferrimagnetic or ferromagnetic, the second susceptor material may also be electrically conductive.

[0014] Preferably, the second susceptor material may include one of mu-metal or permalloy.

[0015] While the second susceptor is primarily configured for monitoring the temperature of the susceptor assembly, the first susceptor is preferably configured for heating the aerosol-forming substrate. To this end, the first susceptor may be optimized in terms of heat loss and therefore heating efficiency. Thus, the first susceptor material may be conductive and / or one of paramagnetic, ferromagnetic or ferrimagnetic. In case the first susceptor material is ferromagnetic or ferrimagnetic, the corresponding Curie temperature of the first susceptor material is preferably different from the Curie temperature of the second susceptor, in particular higher than any typical operating temperature mentioned above for heating the aerosol-forming substrate. For example, the Curie temperature of the first susceptor material may be at least 400 degrees Celsius, in particular at least 500 degrees Celsius, preferably at least 600 degrees Celsius.

[0016] For example, the first susceptor material may include one of aluminum, iron, nickel, copper, bronze, cobalt, plain carbon steel, stainless steel, ferritic stainless steel, martensitic stainless steel, or austenitic stainless steel.

[0017] Preferably, the first susceptor material has a positive temperature coefficient of resistance, while the second susceptor material preferably has a negative temperature coefficient of resistance. According to the present invention, it has been recognized that a susceptor assembly comprising two susceptor materials having opposite temperature coefficients of resistance has a resistance-temperature curve comprising a minimum in resistance near the Curie temperature of the second susceptor material (e.g., ±5 degrees Celsius near the Curie temperature of the second susceptor material). Preferably, this minimum is the overall minimum of the resistance-temperature curve. The minimum is caused by the opposite temperature behavior of the respective resistances of the first and second susceptor materials and the magnetic properties of the second susceptor material. When the susceptor assembly is heated starting from room temperature, the resistance of the first susceptor material increases with increasing temperature, while the resistance of the second susceptor material decreases with increasing temperature. The total apparent resistance of the susceptor assembly ("seen" by the induction source used to inductively heat the susceptor assembly) is given by the combination of the respective resistances of the first and second susceptor materials. When the Curie temperature of the second susceptor material is reached from below, the decrease in the resistance of the second susceptor material generally dominates the increase in the resistance of the first susceptor material. Thus, the total apparent resistance of the susceptor assembly decreases in a temperature range below (particularly close to below) the Curie temperature of the second susceptor material. At the Curie temperature, the second susceptor material loses its magnetic properties. This results in an increase in the skin layer available for eddy currents in the second susceptor material, while its resistance suddenly decreases. Therefore, when the temperature of the susceptor assembly is further increased above the Curie temperature of the second susceptor material, the contribution of the resistance of the second susceptor material to the total apparent resistance of the susceptor assembly becomes smaller or even negligible. Therefore, after passing a minimum near the Curie temperature of the second susceptor material, the total apparent resistance of the susceptor assembly is mainly given by the increased resistance of the first susceptor material. That is, the total apparent resistance of the susceptor assembly increases again. Advantageously, near the Curie temperature of the second susceptor material, the decrease and subsequent increase of the resistance-temperature curve near the minimum can be well distinguished from the temporary change of the total apparent resistance during the user's puff. Therefore, the minimum value of the resistance near the Curie temperature of the second susceptor material can be reliably used as a temperature marker for controlling the heating temperature of the aerosol-forming substrate without the risk of being misinterpreted as a puff by the user. Thus, the protection against undesired overheating of the aerosol-forming substrate is further improved.

[0018] Preferably, the first susceptor and the second susceptor are in close physical contact with each other. In particular, the first susceptor and the second susceptor may form an integral susceptor assembly. Thus, when heated, the first susceptor and the second susceptor have substantially the same temperature. Thus, the temperature control of the first susceptor by the second susceptor is very accurate. The close contact between the first susceptor and the second susceptor may be achieved by any suitable means. For example, the second susceptor may be electroplated, deposited, coated, clad or welded to the first susceptor. Preferred methods include electroplating (water electroplating), cladding, dip coating or roller coating.

[0019] The susceptor assembly according to the invention is preferably configured to be driven by an alternating, in particular high-frequency electromagnetic field. As mentioned herein, the high-frequency electromagnetic field may range between 500 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).

[0020] Each of the first susceptor and the second susceptor or the susceptor assembly may include a variety of geometric configurations. At least one of the first susceptor, the second susceptor or the susceptor assembly may be one of a granular susceptor, or a susceptor filament, or a susceptor mesh, or a susceptor core, or a susceptor pin, or a susceptor rod, or a susceptor blade, or a susceptor strip, or a susceptor sleeve, or a susceptor cup, or a cylindrical susceptor, or a planar susceptor.

[0021] For example, at least one of the first susceptor, the second susceptor or the susceptor assembly can be one of a filament susceptor, a mesh susceptor or a core susceptor. Such susceptors may have advantages in their manufacture, geometric regularity and reproducibility, and their wicking function. Geometric regularity and reproducibility can prove to be advantageous in terms of temperature control and controlled local heating. The wicking function can prove to be advantageous for use with a liquid aerosol-forming substrate. In use, any of these susceptors can be in direct physical contact with the aerosol-forming substrate to be heated. For example, the filamentous first susceptor and / or the second susceptor can be embedded in the aerosol-forming substrate of an aerosol-generating article. Similarly, the first susceptor and / or the second susceptor can be a mesh susceptor or a core susceptor, as part of an aerosol-generating article that preferably includes a liquid aerosol-forming substrate, or as part of an aerosol-generating device. In the latter configuration, the device can include a container for a liquid aerosol-forming substrate. Alternatively, the device may be configured to receive an aerosol-generating article, in particular a cartridge, comprising a liquid aerosol-forming substrate and configured to engage a filament susceptor or a mesh susceptor or a wick susceptor of the aerosol-generating device.

[0022] At least one of the first susceptor, the second susceptor or the susceptor assembly may be a susceptor blade or a susceptor rod or a susceptor pin. Preferably, the first susceptor and the second susceptor together form a susceptor blade or a susceptor rod or a susceptor pin. For example, one of the first susceptor or the second susceptor may form a core or inner layer of a susceptor blade or a susceptor rod or a susceptor pin, and the respective other of the first susceptor or the second susceptor may form a sheath or envelope of the susceptor blade or a susceptor rod or a susceptor pin.

[0023] As a susceptor blade or a susceptor rod or a susceptor pin, at least one of the first susceptor, the second susceptor or the susceptor assembly may be part of an aerosol-generating article, in particular may be arranged in an aerosol-forming substrate of the aerosol-generating article. One end of the susceptor blade or the susceptor rod or the susceptor pin may be tapered or pointed to facilitate the insertion of the susceptor blade or the susceptor rod or the susceptor pin into the aerosol-forming substrate of the article.

[0024] Alternatively, at least one of the first susceptor, the second susceptor or the susceptor assembly, each as a susceptor blade or a susceptor rod or a susceptor pin, may be part of an aerosol generating device. One of the ends, in particular the distal end, of the susceptor blade or the susceptor rod or the susceptor pin may be arranged at, in particular attached to, a bottom portion of a receiving cavity of the device. From there, the susceptor blade or the susceptor rod or the susceptor pin preferably extends towards the opening of the receiving cavity into the inner void of the receiving cavity. The opening of the receiving cavity is preferably located at the proximal end of the aerosol generating device. The other end, i.e. the distal free end of the susceptor blade or the susceptor rod or the susceptor pin, may be tapered or pointed so that the susceptor blade or the susceptor rod or the susceptor pin easily penetrates into the aerosol-forming substrate to be heated, for example into an aerosol-forming substrate arranged at the distal end portion of the aerosol generating article.

[0025] In each case, the length of the susceptor blade or the susceptor rod or the susceptor pin may be in the range of 8 mm (millimeter) to 16 mm (millimeter), in particular 10 mm (millimeter) to 14 mm (millimeter), preferably 12 mm (millimeter). In the case of a susceptor blade, the width of the first susceptor and / or the second susceptor, in particular the susceptor assembly, may for example be in the range of 2 mm (millimeter) to 6 mm (millimeter), in particular 4 mm (millimeter) to 5 mm (millimeter). Likewise, the thickness of the blade-shaped first susceptor and / or the second susceptor, in particular the blade-shaped susceptor assembly, is preferably in the range of 0.03 mm (millimeter) to 0.15 mm (millimeter), more preferably in the range of 0.05 mm (millimeter) to 0.09 mm (millimeter).

[0026] At least one of the first susceptor, the second susceptor or the susceptor assembly may be a cylindrical susceptor or a susceptor sleeve or a susceptor cup. The cylindrical susceptor or the susceptor sleeve or the susceptor cup may form a receiving cavity, or may be arranged circumferentially around the receiving cavity of the aerosol generating device, and the heating assembly may be part of the aerosol generating device. In this configuration, the first susceptor and / or the second susceptor or the susceptor assembly realizes an induction heating oven or a heating chamber, which is configured to receive the aerosol-forming substrate to be heated therein. Alternatively, at least one of the first susceptor, the second susceptor or the susceptor assembly (each of which is a cylindrical susceptor or a susceptor sleeve or a susceptor cup) may surround at least a portion of the aerosol-forming substrate to be heated, thereby realizing a heating oven or a heating chamber. In particular, each of them may form at least a portion of a shell, a packaging material, a shell or a housing of an aerosol generating article.

[0027] The susceptor assembly may be a multi-layer susceptor assembly. In this regard, the first susceptor and the second susceptor may form multiple layers, in particular adjacent layers of the multi-layer susceptor assembly.

[0028] In the multi-layer susceptor assembly, the first susceptor and the second susceptor may be in close physical contact with each other. Thus, since the first susceptor and the second susceptor have substantially the same temperature, the temperature control of the first susceptor by the second susceptor is sufficiently accurate.

[0029] The second susceptor may be plated, deposited, coated, clad or welded onto the first susceptor.Preferably, the second susceptor is applied to the first susceptor by spraying, dipping, rolling, plating or cladding.

[0030] Preferably, the second susceptor is present as a dense layer. The dense layer has a higher magnetic permeability than the porous layer, making it easier to detect subtle changes in Curie temperature.

[0031] The individual layers of the multilayer susceptor assembly may be bare or exposed to the environment on the circumferential outer surface of the multilayer susceptor assembly when viewed in any direction parallel and / or transverse to the layers.Alternatively, the multilayer susceptor assembly may be coated with a protective coating.

[0032] Multilayered susceptor assemblies can be used to achieve different geometric configurations of the susceptor assemblies.

[0033] For example, the multi-layer susceptor assembly may be an elongated susceptor strip or susceptor leaf having a length in the range of 8 mm (millimeters) to 16 mm (millimeters), in particular in the range of 10 mm (millimeters) to 14 mm (millimeters), preferably 12 mm (millimeters). The width of the susceptor assembly may for example be in the range of 2 mm (millimeters) to 6 mm (millimeters), in particular in the range of 4 mm (millimeters) to 5 mm (millimeters). The thickness of the susceptor assembly is preferably in the range of 0.03 mm (millimeters) to 0.15 mm (millimeters), more preferably in the range of 0.05 mm (millimeters) to 0.09 mm (millimeters). The multi-layer susceptor leaf may have a free tapered tip.

[0034] For example, the multi-layer susceptor assembly may be an elongated strip having a first susceptor that is a 430 grade stainless steel strip having a length of 12 mm (millimeters), a width of 4 mm (millimeters) to 5 mm (millimeters), such as 4 mm (millimeters), and a thickness of about 50 μm (micrometers). The 430 grade stainless steel may be coated with a layer of mu metal or permalloy as a second susceptor having a thickness between 5 μm (micrometers) and 30 μm (micrometers), such as 10 μm (micrometers).

[0035] As used herein, the term "thickness" refers to the dimension extending between the top side and the bottom side, such as between the top side and the bottom side of a layer or between the top side and the bottom side of a multilayer susceptor assembly. As used herein, the term "width" refers to the dimension extending between two opposing sides. As used herein, the term "length" refers to the dimension extending between the front and back or between two other opposing sides that are orthogonal to the two opposing sides forming the width. The thickness, width, and length may be orthogonal to each other.

[0036] Likewise, the multi-layer susceptor assembly may be a multi-layer susceptor rod or a multi-layer susceptor pin, in particular as described above. In this configuration, one of the first susceptor or the second susceptor may form a core layer surrounded by a surrounding layer formed by the respective other of the first susceptor or the second susceptor. Preferably, where the first susceptor is optimized for heating the substrate, then the first susceptor forms the surrounding layer. Thus, heat transfer to the surrounding aerosol-forming substrate is enhanced.

[0037] Alternatively, the multilayer susceptor assembly may be a multilayer susceptor sleeve or a multilayer susceptor cup or a cylindrical multilayer susceptor, in particular as described above. One of the first or second susceptors may form an inner wall of the multilayer susceptor sleeve or the multilayer susceptor cup or the cylindrical multilayer susceptor. The respective other of the first or second susceptors may form an outer wall of the multilayer susceptor sleeve or the multilayer susceptor cup or the cylindrical multilayer susceptor. Preferably, in particular in case the first susceptor is optimized for heating a substrate, the first susceptor forms the inner wall. As described above, the multilayer susceptor sleeve or the multilayer susceptor cup or the cylindrical multilayer susceptor may surround at least a portion of an aerosol-forming substrate to be heated, in particular may form at least a portion of an outer layer, a packaging material, an outer shell or a housing of an aerosol-generating article. Alternatively, the multilayer susceptor sleeve or the multilayer susceptor cup or the cylindrical multilayer susceptor may form a receiving cavity or may be arranged circumferentially around a receiving cavity of an aerosol generating device, of which the heating assembly may be part.

[0038] For example, for the purposes of manufacturing an aerosol-generating article, it may be desirable for the first susceptor and the second susceptor to have similar geometric configurations, as described above.

[0039] Alternatively, the first susceptor and the second susceptor may have different geometric configurations. Thus, the first and second susceptors may be tailored to suit their specific functions. The first susceptor, which preferably has a heating function, may have a geometric configuration that presents a large surface area to the aerosol-forming substrate to enhance heat transfer. In contrast, the second susceptor, which preferably has a temperature control function, does not need to have a very large surface area. If the first susceptor material is optimized for heating the substrate, it may be preferred that the volume of the second susceptor material is no greater than the volume required to provide a detectable Curie point.

[0040] According to this aspect, the second susceptor may include one or more second susceptor elements. Preferably, the one or more second susceptor elements are significantly smaller than the first susceptor, i.e., their volume is smaller than the volume of the first susceptor. Each of the one or more second susceptor elements may be in close physical contact with the first susceptor. Thereby, the first susceptor and the second susceptor have substantially the same temperature, which improves the accuracy of the temperature control of the first susceptor via the second susceptor used as a temperature marker.

[0041] For example, the first susceptor may be in the form of a susceptor blade or a susceptor strip or a susceptor sleeve or a susceptor cup, and the second susceptor material may be in the form of discrete patches plated, deposited or welded onto the first susceptor material.

[0042] According to another example, the first susceptor may be a strip susceptor or a filament susceptor or a mesh susceptor, while the second susceptor is a particle susceptor. Both the filament or mesh shaped first susceptor and the particle shaped second susceptor may, for example, be embedded in the aerosol-generating article to be in direct physical contact with the aerosol-forming substrate to be heated. In this particular configuration, the first susceptor may extend through the center of the aerosol-generating article within the aerosol-forming substrate, while the second susceptor may be evenly distributed throughout the aerosol-forming substrate.

[0043] The first susceptor and the second susceptor need not be in close physical contact with each other. The first susceptor may be a susceptor blade implementing a heating blade for penetrating into the aerosol-forming substrate to be heated. Likewise, the first susceptor may be a susceptor sleeve or a susceptor cup implementing a heating oven or heating chamber. In any of these configurations, the second susceptor may be located at a different position within the heating assembly, spaced apart from the first susceptor but still in thermal proximity to the first susceptor.

[0044] The first susceptor and the second susceptor may form different parts of the susceptor assembly. For example, the first susceptor may form a sidewall portion or a sleeve portion of a cup-shaped susceptor assembly, while the second susceptor forms a bottom portion of the cup-shaped susceptor assembly.

[0045] At least a portion of at least one of the first susceptor and the second susceptor may include a protective cover. Likewise, at least a portion of the susceptor assembly may include a protective cover. The protective cover may be formed of glass, ceramic or an inert metal formed or coated on the first susceptor and / or the second susceptor or at least a portion of the susceptor assembly, respectively. Advantageously, the protective cover may be configured to achieve at least one of the following purposes: avoid adhesion of the aerosol-forming substrate to the surface of the susceptor; avoid diffusion of materials, such as metal diffusion, from the susceptor material into the aerosol-forming substrate to increase the mechanical stiffness of the susceptor assembly. Preferably, the protective cover is non-conductive.

[0046] For generating the alternating electromagnetic field, the induction source may comprise at least one inductor, preferably at least one induction coil.

[0047] The induction source may comprise a single induction coil or a plurality of induction coils. The number of induction coils may depend on the number of susceptors and / or the size and shape of the susceptor assembly. One or more induction coils may have a shape that matches the shape of the first susceptor and / or the second susceptor or the susceptor assembly, respectively. Likewise, one or more induction coils may have a shape that matches the shape of a housing of an aerosol generating device of which the heating assembly may be a part.

[0048] At least one induction coil may be a spiral coil or a planar coil, in particular a pancake coil or a bent planar coil. The use of a flat spiral coil allows for a compact design that is sturdy and cheap to manufacture. The use of a spiral induction coil advantageously allows for the generation of a uniform alternating electromagnetic field. As used herein, a "flat spiral coil" means a substantially planar coil in which the axis of the coil winding is perpendicular to the surface on which the coil is located. The flat spiral induction member may have any desired shape within the plane of the coil. For example, the flat spiral coil may have a circular shape, or may have a substantially oblong or rectangular shape. However, the term "flat spiral coil" as used herein encompasses both planar coils and flat spiral coils shaped to conform to a curved surface. For example, the induction coil may be a "bent" planar coil arranged around a preferably cylindrical coil support, such as a ferrite core. In addition, the flat spiral coil may include, for example, a two-layer four-turn flat spiral coil or a single-layer four-turn flat spiral coil.

[0049] The first induction coil and / or the second induction coil may be held within a housing of the heating assembly, or one of a body or housing of an aerosol generating device comprising the heating assembly. The first induction coil and / or the second induction coil may be wound around a preferably cylindrical coil support, such as a ferrite core.

[0050] The induction source may include an alternating current (AC) generator. The AC generator may be powered by a power source of the aerosol generating device. The AC generator may be operably coupled to the at least one induction coil. In particular, the at least one induction coil may be an integral part of the AC generator. The AC generator is configured to generate a high frequency oscillating current to pass through the at least one induction coil to generate an alternating electromagnetic field. The AC current may be continuously supplied to the at least one induction coil after activation of the system, or may be intermittently supplied, for example on a puff-by-puff basis.

[0051] Preferably, the inductive source comprises a DC / AC converter connected to a DC power source comprising an LC network, wherein the LC network comprises a series connection of a capacitor and an inductor.

[0052] The induction source is preferably configured to generate a high frequency electromagnetic field. As mentioned herein, the high frequency electromagnetic field may range between 500kHz (kilohertz) and 30MHz (megahertz), in particular between 5MHz (megahertz) and 15MHz (megahertz), preferably between 5MHz (megahertz) and 10MHz (megahertz).

[0053] The heating assembly may further comprise a controller configured to control the operation of the heating assembly. In particular, the controller may be configured to control the operation of the induction source, preferably in a closed loop configuration, for controlling the heating of the aerosol-forming substrate to a predetermined operating temperature. As previously mentioned, the operating temperature for heating the aerosol-forming substrate may be at least 300 degrees Celsius, in particular at least 350 degrees Celsius, preferably at least 370 degrees Celsius, most preferably at least 400 degrees Celsius. These temperatures are typical operating temperatures for heating but not burning an aerosol-forming substrate.

[0054] The controller may include a microprocessor, for example a programmable microprocessor, a microcontroller or an application specific integrated chip (ASIC) or other electronic circuit capable of providing control. The controller may include other electronic components, such as at least one DC / AC inverter and / or a power amplifier, for example a class D or class E power amplifier. In particular, the inductive source may be part of the controller.

[0055] The controller may be, or may be, technology that is an integral controller of the aerosol generating device of which the heating assembly according to the invention is a part.

[0056] The controller and at least some of the inductive sources, in particular those other than the inductors, can be arranged on a common printed circuit board. This has proven to be particularly advantageous with regard to a compact design of the heating assembly.

[0057] The controller may be configured to determine a minimum value of the apparent resistance occurring within a temperature range of ±5 degrees Celsius around the Curie temperature of the second susceptor material during warm-up of the susceptor assembly (starting from room temperature towards the operating temperature). Advantageously, this enables a correct identification of the temperature signature with respect to the Curie temperature of the second susceptor material. To this end, the controller may typically be configured to determine and form a supply current, in particular a DC supply current, drawn from the power supply from a supply voltage, in particular a DC supply voltage, the actual apparent resistance of the susceptor assembly in turn being indicative of the actual temperature of the susceptor assembly.

[0058] In order to determine the actual apparent resistance of the susceptor assembly indicating the actual temperature of the susceptor assembly, the controller of the heating assembly may comprise at least one of a voltage sensor, in particular a DC voltage sensor for measuring the supply voltage, in particular a DC supply voltage drawn from the power supply, or a current sensor, in particular a DC current sensor for measuring the supply current, in particular a DC supply current drawn from the power supply.

[0059] In addition, the controller may be configured to control the operation of the inductive source in a closed-loop configuration so that the actual apparent resistance corresponds to the minimum value of the determined apparent resistance plus a predetermined offset value of the apparent resistance for controlling the heating of the aerosol-forming substrate to the operating temperature. In this regard, the control of the heating temperature is preferably based on the principle of offset locking or offset control, which uses a predetermined offset value of the apparent resistance to compensate for the difference between the apparent resistance measured at the marking temperature and the apparent resistance at the operating temperature. Advantageously, this can avoid directly controlling the heating temperature based on a predetermined target value of the apparent resistance at the operating temperature and thus avoid misinterpretation of the measured resistance characteristics.

[0060] Furthermore, offset control of the heating temperature is more stable and reliable than temperature control based on the measured absolute value of the apparent resistance at the desired operating temperature. This is due to the fact that the measured absolute value of the apparent resistance determined from the supply voltage and the supply current depends on various factors, such as the resistance of the sensing source circuit and various contact resistances. Such factors are susceptible to environmental influences and may vary over time and / or between different sensing sources and susceptor assemblies of the same type, depending on manufacturing conditions. Advantageously, such influences substantially cancel the difference between the two measured absolute values ​​of the apparent resistance. Therefore, using an offset value of the apparent resistance to control the temperature is less prone to such adverse influences and variations.

[0061] The offset value of the apparent resistance used to control the heating temperature of the aerosol-forming substrate to the operating temperature may be predetermined by means of calibration measurements, for example during manufacture of the device.

[0062] Preferably, the minimum around the Curie temperature of the second susceptor material is an overall minimum of the resistance-temperature curve.

[0063] As used herein, the term "starting from room temperature" preferably means that a minimum around the Curie temperature of the second susceptor material appears in the resistance-temperature curve during preheating, i.e. heating of the susceptor assembly from room temperature towards the operating temperature of the aerosol-forming substrate to be heated.

[0064] As used herein, room temperature may correspond to a temperature in the range between 18 degrees Celsius and 25 degrees Celsius, in particular to a temperature of 20 degrees Celsius.

[0065] The heating assembly may include a power supply, in particular a DC power supply, which is configured to provide a DC supply voltage and a DC supply current to the induction source. Preferably, the power supply is a battery, such as a lithium iron phosphate battery. Alternatively, the power supply may be another form of charge storage device, such as a capacitor. The power supply may need to be charged, that is, the power supply may be rechargeable. The power supply may have a capacity that allows sufficient energy to be stored for one or more user experiences. For example, the power supply may have sufficient capacity to allow continuous generation of aerosols in a period of about six minutes or a period of an integral multiple of six minutes. In another example, the power supply may have sufficient capacity to allow a predetermined number of puffs or discontinuous activation of the induction source. The power supply may be an integral power supply of an aerosol generating device, and the heating assembly according to the present invention is part of the aerosol generating device.

[0066] According to the present invention, there is also provided an aerosol generating device for generating an aerosol by heating an aerosol-forming substrate. The device comprises a receiving cavity for receiving the aerosol-forming substrate to be heated. The device further comprises an induction heating assembly according to the present invention and as described herein, the induction heating assembly being used for inductively heating the aerosol-forming substrate in the receiving cavity.

[0067] As used herein, the term "aerosol generating device" is used to describe an electrically operated device capable of interacting with at least one aerosol-forming substrate, in particular an aerosol-forming substrate disposed within an aerosol-generating article, so as to generate an aerosol by heating the substrate. Preferably, the aerosol generating device is a suction device for generating an aerosol that can be inhaled directly by a user through the user's mouth. In particular, the aerosol generating device is a handheld aerosol generating device.

[0068] As used herein, the term "aerosol-forming substrate" refers to a substrate that can release volatile compounds that can form an aerosol after heating the aerosol-forming substrate. The aerosol-forming substrate is a part of an aerosol-generating article. The aerosol-forming substrate can be a solid or preferably a liquid aerosol-forming substrate. In both cases, the aerosol-forming substrate can include at least one of a solid and a liquid component. The aerosol-forming substrate can include a tobacco-containing material that contains volatile tobacco flavor compounds released from the substrate after heating. Alternatively or additionally, the aerosol-forming substrate can include non-tobacco materials. The aerosol-forming substrate can also include an aerosol-forming agent. The example of a suitable aerosol-forming agent is glycerol and propylene glycol. The aerosol-forming substrate can also include other additives and ingredients, such as nicotine or spices. The aerosol-forming substrate may also be a paste-like material, a pouch of porous material comprising the aerosol-forming substrate, or loose tobacco mixed with, for example, a gelling agent or adhesive, which may contain common aerosol formers such as glycerol, and compressed or moulded into a plug.

[0069] The receiving cavity may be embedded in the housing of the aerosol generating device.

[0070] As described above, the aerosol generating device may comprise an integral controller for controlling the operation of the device.The integral controller may contain or may comprise a controller of the heating assembly.

[0071] As further described above, the aerosol generating device may also comprise a power supply, in particular a DC power supply, such as a battery. In particular, the power supply may be an integral power supply of the aerosol generating device, in particular for providing a DC supply voltage and a DC supply current to the induction source of the heating assembly.

[0072] The aerosol generating device may comprise a body, which preferably comprises at least one of an induction source, at least one induction coil, a controller, a power source and at least a portion of the receiving cavity.

[0073] In addition to the body, the aerosol generating device may further comprise a mouthpiece, in particular in the case where the aerosol generating article to be used with the device does not comprise a mouthpiece. The mouthpiece may be mounted to the body of the device. The mouthpiece may be configured to close the receiving cavity when the mouthpiece is mounted to the body. In order to attach the mouthpiece to the body, the proximal portion of the body may comprise a magnetic or mechanical mounting, such as a bayonet mounting or a snap-fit ​​mounting, which engages with a corresponding counterpart at the distal portion of the mouthpiece. In the case where the device does not comprise a mouthpiece, the aerosol generating article to be used with the aerosol generating device may comprise a mouthpiece, such as a filter segment.

[0074] The aerosol generating device may comprise at least one air outlet, for example in the mouthpiece (if present).

[0075] Preferably, the aerosol generating device comprises an air path extending from the at least one air inlet through the receiving chamber and, if present, further to an air outlet in the mouthpiece. Preferably, the aerosol generating device comprises at least one air inlet in fluid communication with the receiving chamber. Thus, the aerosol generating system may comprise an air path extending from the at least one air inlet into the receiving chamber and further through the aerosol-forming substrate and the mouthpiece in the article into the mouth of the user.

[0076] Other features and advantages of the aerosol generating device according to the invention have already been described with respect to the heating assembly and will not be repeated.

[0077] According to the present invention, there is also provided an aerosol generating system. The system comprises an aerosol generating device, an aerosol generating article for use with the aerosol generating device, and an induction heating assembly according to the present invention and as described herein. The induction source of the heating assembly is part of the aerosol generating device. The first susceptor of the susceptor assembly is part of the aerosol generating article, and the second susceptor of the susceptor assembly is part of the aerosol generating article or part of the aerosol generating device.

[0078] Advantageously, the first susceptor (as part of the aerosol-generating article) may be configured to heat the aerosol-forming substrate. To this end, the first susceptor may be optimized with respect to heat loss and thus heating efficiency. For example, the first susceptor may be a susceptor strip, a susceptor blade, a susceptor rod, a susceptor pin, a susceptor mesh, a susceptor filament or a particle susceptor arranged with the aerosol-forming substrate of the aerosol-generating article.

[0079] In contrast, the second susceptor may be primarily configured to monitor the temperature of the susceptor assembly. To this end, the second susceptor may be part of, and in particular be arranged in, an aerosol generating article or an aerosol generating device. In either configuration, when the article is used with the device, in particular when coupled to the device, the second susceptor is preferably arranged to be in thermal proximity to or even in thermal contact with the first susceptor and / or the aerosol forming substrate. Advantageously, this ensures that during operation of the aerosol generating system, the second susceptor has substantially the same temperature as the first susceptor and / or the aerosol forming substrate. Thus, correct and precise temperature control may be achieved. For example, the second susceptor may be arranged at the inner wall of the receiving chamber of the aerosol generating device.

[0080] If present, the controller of the heating assembly may be part of, in particular arranged in, the aerosol generating device.Preferably, the controller of the aerosol generating device may comprise or may be the controller of the heating assembly.

[0081] Likewise, if present, the power supply for the heating assembly may be part of, in particular arranged in, the aerosol generating device.Preferably, the power supply for the aerosol generating device may comprise or may be the power supply for the heating assembly.

[0082] The aerosol-generating device may comprise a receiving cavity for receiving at least a portion of the aerosol-generating article.

[0083] 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 comprising at least one aerosol-forming substrate is intended to be heated rather than burned in order to release volatile compounds that can form an aerosol. The aerosol-generating article can be a consumable, in particular a consumable that is discarded after a single use. The aerosol-generating article can be a tobacco product. For example, the article can be a cartridge comprising a liquid or solid aerosol-forming substrate to be heated. Alternatively, the article can be a rod-shaped article, in particular a tobacco product, similar to a conventional cigarette and comprising a solid aerosol-forming substrate.

[0084] Preferably, the aerosol-generating article has a circular or elliptical or oval or square or rectangular or triangular or polygonal cross-section.

[0085] In addition to the aerosol-forming substrate and the susceptor assembly, the article may comprise various elements.

[0086] In particular, the article may include a mouthpiece. As used herein, the term "mouthpiece" refers to the portion of the article that is placed in the user's mouth so as to inhale the aerosol directly from the article. Preferably, the mouthpiece includes a filter.

[0087] Furthermore, the article may comprise a housing, in particular a tubular packaging material, surrounding at least a portion of the aerosol-forming substrate. The packaging material may comprise a susceptor assembly. Advantageously, this allows uniform and symmetrical heating of the aerosol-forming substrate surrounded by the susceptor assembly.

[0088] In particular, with regard to aerosol-generating products having a rod-shaped product similar to a conventional cigarette and / or comprising a solid aerosol-forming substrate, the product may also include: a support element having a central air channel, an aerosol cooling element and a filter element. The filter element is preferably used as a mouthpiece. In particular, the product may include a substrate element, which includes an aerosol-forming substrate and a receptor assembly in contact with the aerosol-forming substrate. Any one or any combination of these elements may be arranged sequentially to the aerosol-forming rod segment. Preferably, the substrate element is arranged at the distal end of the product. Similarly, the filter element is preferably arranged at the proximal end of the product. In addition, these elements may have the same outer cross-section as the aerosol-forming rod segment.

[0089] Furthermore, the article may comprise a housing or packaging material surrounding at least a portion of the aerosol-forming substrate. In particular, the article may comprise a packaging material surrounding at least a portion of the above-mentioned different segments and elements so as to hold them together and maintain the desired cross-sectional shape of the article.

[0090] The housing or packaging material may comprise at least the first susceptor of the susceptor assembly or both the first susceptor and the second susceptor. Advantageously, this allows uniform and symmetrical heating of the aerosol-forming substrate surrounded by the first susceptor or the susceptor assembly.

[0091] Preferably, the shell or packaging material forms at least a portion of the outer surface of the article. The shell can form a tube including a container, and the container holds an aerosol-forming substrate, such as a liquid aerosol-forming substrate. The packaging material can be a wrapping paper, specifically a wrapping paper made of cigarette paper. Alternatively, the packaging material can be a foil, such as made of plastic. The packaging material can be fluid-permeable, so as to allow the vaporized aerosol-forming substrate to be released from the article, or to allow air to be sucked into the article around the article. In addition, the packaging material can include at least one volatile substance that will be activated and released from the packaging material after heating. For example, the packaging material can be impregnated with a flavoring volatile substance.

[0092] Further features and advantages of the aerosol generating system according to the invention have already been described with respect to the aerosol generating device and the heating assembly, and will not be repeated. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] The present invention will be further described, by way of example only, with reference to the accompanying drawings, in which:

[0094] Figure 1 is a schematic diagram of an aerosol generating system comprising an induction heated aerosol generating device and an aerosol generating article, wherein the system comprises a heating assembly according to a first exemplary embodiment of the present invention;

[0095] Figure 2 is based on Figure 1 A schematic diagram of an inductively heatable aerosol-generating article;

[0096] Figure 3 is based on Figure 1 and Figure 2 A perspective view of a susceptor assembly of an aerosol-generating article;

[0097] Figure 4 is a diagram schematically showing a resistance-temperature curve of a susceptor assembly according to the present invention;

[0098] Figures 5 to 7 shows the use of Figure 1 and Figure 2 Alternative embodiments of susceptor assemblies for use with articles of the invention;

[0099] Figures 8 to 10 Shown according to Figure 1 an aerosol generating article for use with a device comprising other alternative embodiments of a susceptor assembly;

[0100] Fig.11 is a schematic diagram of another aerosol generating system including a heating assembly according to a second exemplary embodiment of the present invention;

[0101] Fig.12 is included in the Fig.11 A perspective view of a sensor assembly in an aerosol generating device;

[0102] Figures 13 to 15 Shown according to Fig.11 Alternative embodiments of a susceptor assembly for use with a device;

[0103] Fig.16 is a schematic diagram of an aerosol generating system including a heating assembly according to a third exemplary embodiment of the present invention;

[0104] Fig.17 is a schematic diagram of an aerosol generating system including a heating assembly according to a fourth exemplary embodiment of the present invention;

[0105] Fig.18 is a schematic diagram of an aerosol generating system including a heating assembly according to a fifth exemplary embodiment of the present invention, and

[0106] Fig.19 is a schematic diagram of an aerosol generating system including a heating assembly according to a sixth exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0107] Figure 1 A first exemplary embodiment of an aerosol generating system 1 according to the invention is schematically shown. The system 1 comprises an aerosol generating device 10 according to the invention and an aerosol generating article 100 configured for use with the device and comprising an aerosol-forming substrate to be heated.

[0108] Figure 2More details of an aerosol-generating article 100 are shown, which has essentially a rod shape and comprises four elements arranged in sequence in coaxial alignment: an aerosol-forming rod segment 110 comprising a susceptor assembly 120 and an aerosol-forming substrate 130, a support element 140 having a central air channel 141, an aerosol-cooling element 150, and a filter element 160 serving as a mouthpiece. The aerosol-forming rod segment 110 is arranged at the distal end 102 of the article 100, while the filter element 160 is arranged at the distal end 103 of the article 100. Each of the four elements is an essentially cylindrical element, all of which have essentially the same diameter. In addition, the four elements are surrounded by an outer packaging material 170 in order to hold the four elements together and maintain the desired circular cross-sectional shape of the rod-shaped article 100. The packaging material 170 is preferably made of paper. In addition to the details of the susceptor assembly 120 within the shaft segment 110, further details of the article, in particular further details of the four elements, are disclosed in WO 2015 / 176898 A1.

[0109] refer to Figure 1 , the aerosol generating device 10 comprises a cylindrical receiving cavity 20 defined within a proximal portion 12 of the device 10 for receiving at least a distal portion of an article 100 therein. The device 10 further comprises an induction source comprising an induction coil 30 for generating an alternating, in particular high frequency, electromagnetic field. In the present embodiment, the induction coil 30 is a helical coil circumferentially surrounding the cylindrical receiving cavity 20. The coil 30 is arranged such that a susceptor assembly 120 of the aerosol generating article 100 is subjected to the electromagnetic field when the article 100 is engaged with the device 10. Thus, upon activation of the induction source, the susceptor assembly 120 heats up due to eddy currents and / or hysteresis losses induced by the alternating electromagnetic field, depending on the magnetic and electrical properties of the susceptor material of the susceptor assembly 120. The susceptor assembly 120 is heated until an operating temperature is reached which is sufficient to vaporize an aerosol-forming substrate 130 surrounding the susceptor assembly 120 within the article 100.

[0110] Within the distal portion 13, the aerosol generating device 10 also includes a DC power supply 40 and a controller 50 (only in Figure 1 ), for powering and controlling the heating process. In electronic terms, the induction source (except the induction coil 30) is preferably at least partially an integral part of the controller 50.

[0111] Both the induction source (as part of the device 10 ) and the susceptor assembly 120 (as part of the aerosol-generating article 100 ) form essential parts of the induction heating assembly 5 according to the present invention.

[0112] Figure 3 Shows Figure 1 and Figure 2 Detailed view of a susceptor assembly 120 for use in an aerosol-generating article is shown. According to the present invention, the susceptor assembly 120 includes a first susceptor 121 and a second susceptor 122. The first susceptor 121 includes a first susceptor material having a positive temperature coefficient of resistance, and the second susceptor 122 includes a second ferromagnetic or ferrimagnetic susceptor material having a negative temperature coefficient of resistance. Because the first and second susceptor materials have opposite temperature coefficients of resistance, and because of the magnetic properties of the second susceptor material, the susceptor assembly 120 has a resistance-temperature curve that includes a minimum resistance value near the Curie temperature of the second susceptor material.

[0113] The corresponding resistance-temperature curve is Figure 4 . When the susceptor assembly 120 is initially heated from room temperature T_R, the resistance of the first susceptor material increases with increasing temperature T, while the resistance of the second susceptor material decreases with increasing temperature T. The total apparent resistance R_a of the susceptor assembly 120 (as "seen" by the induction source of the device 10 for inductively heating the susceptor assembly 120) is given by the combination of the respective resistances of the first susceptor material and the second susceptor material. When the Curie temperature T_C of the second susceptor material is reached from below, the decrease in the resistance of the second susceptor material generally dominates the increase in the resistance of the first susceptor material. Therefore, the total apparent resistance R_a of the susceptor assembly 120 decreases in a temperature range below (in particular close to below) the Curie temperature T_C of the second susceptor material. At the Curie temperature T_C, the second susceptor material loses its magnetic properties. This results in an increase in the skin layer available for eddy currents in the second susceptor material, while its resistance suddenly decreases. Therefore, when the temperature T of the susceptor assembly 120 is further increased above the Curie temperature T_C of the second susceptor material, the contribution of the resistance of the second susceptor material to the total apparent resistance R_a of the susceptor assembly 120 becomes smaller or even negligible. Therefore, after passing the minimum value R_min near the Curie temperature T_C of the second susceptor material, the total apparent resistance R_a of the susceptor assembly 120 is mainly given by the increased resistance of the first susceptor material. That is, the total apparent resistance R_a of the susceptor assembly 120 increases again towards the operating resistance R_op at the operating temperature T_op. Advantageously, the decrease and subsequent increase of the resistance-temperature curve near the minimum value R_min near the Curie temperature T_C of the second susceptor material can be sufficiently distinguished from the temporary change of the total apparent resistance during the user's puff. Therefore, the minimum value of the resistance R_a near the Curie temperature T_C of the second susceptor material can be reliably used as a temperature marker for controlling the heating temperature of the aerosol-forming substrate without the risk of being misinterpreted as a user's puff. Thus, undesired overheating of the aerosol-forming substrate may be effectively prevented.

[0114] In order to control the heating temperature of the aerosol-forming substrate to correspond to the desired operating temperature T_op, Figure 1 The controller 50 of the device 10 shown is configured to control the operation of the induction source in a closed-loop offset configuration so as to maintain the actual apparent resistance at a value corresponding to the minimum value R_min of the determined apparent resistance R_a plus a predetermined offset value ΔR_offset. The offset value ΔR_offset compensates for the difference between the apparent resistance R_min measured at the marking temperature T_C and the operating resistance R_op at the operating temperature T_op. Advantageously, this can avoid directly controlling the heating temperature based on a predetermined target value of the apparent resistance at the operating temperature T_op. Moreover, the offset control of the heating temperature is more stable and reliable than temperature control based on the measured absolute value of the apparent resistance at the desired operating temperature.

[0115] When the actual apparent resistance is equal to or exceeds the determined minimum value of the apparent resistance plus the predetermined offset value of the apparent resistance, the heating process can be stopped by interrupting the generation of the alternating electromagnetic field, i.e. by disconnecting the induction source or at least by reducing the output power of the induction source. When the actual apparent resistance is lower than the determined minimum value of the apparent resistance plus the predetermined offset value of the apparent resistance, the heating process can be resumed by resuming the generation of the alternating electromagnetic field, i.e. by switching on the induction source again or by re-increasing the output power of the induction source.

[0116] In the present embodiment, the operating temperature is about 370 degrees Celsius. This temperature is a typical operating temperature for heating but not burning an aerosol-forming substrate. In order to ensure a sufficiently large temperature difference of at least 20 degrees Celsius between the marking temperature at the Curie temperature T_C of the second susceptor material and the operating temperature T_op, the second susceptor material is selected so that the Curie temperature is below 350 degrees Celsius.

[0117] like Figure 3 As shown, in Figure 2The susceptor assembly 120 in the article is a multilayer susceptor assembly, more particularly a double-layer susceptor assembly. It comprises a first layer constituting a first susceptor 121 and a second layer constituting a second susceptor 122, the second layer being arranged on the first layer and closely coupled thereto. As described above, while the first susceptor 121 is optimized with respect to heat loss and thus with respect to heating efficiency, the second susceptor 122 is primarily a functional susceptor used as a temperature marker. The susceptor assembly 120 is in the form of an elongated strip having a length L of 12 mm and a width W of 4 mm, i.e., the length L of the two layers is 12 mm and the width W is 4 mm. The first susceptor 121 is a strip made of stainless steel having a Curie temperature exceeding 400° C., for example 430 grade stainless steel. Its thickness is about 35 microns. The second susceptor 122 is a strip of mu metal or permalloy having a Curie temperature below the operating temperature. Its thickness is about 10 microns. The susceptor assembly 120 is formed by cladding the second susceptor strip to the first susceptor strip.

[0118] Figure 5 An alternative embodiment of a strip-shaped susceptor assembly 220 is shown, which is similar to Figure 1 and Figure 2 Compared with the latter, according to Figure 5 The susceptor assembly 220 is a three-layer susceptor assembly including a third susceptor 223 forming a third layer in addition to first and second susceptors 221 and 222 forming the first and second layers, respectively. All three layers are arranged on top of each other, with adjacent layers being tightly coupled to each other. Figure 5 The first susceptor 221 and the second susceptor 222 of the three-layer susceptor assembly are shown Figure 1 and Figure 2 The first susceptor 121 and the second susceptor 122 of the illustrated dual layer susceptor assembly 120 are identical. The third susceptor 223 is identical to the first susceptor 221. That is, the third layer 223 comprises the same material as the first susceptor 221. Moreover, the layer thickness of the third susceptor 223 is equal to the layer thickness of the first susceptor 221. Therefore, the thermal expansion behavior of the first susceptor 221 and the third susceptor 223 is substantially identical. Advantageously, this provides a highly symmetrical layer structure that exhibits substantially no out-of-plane deformation. Additionally, according to Figure 5 The three-layer susceptor assembly provides higher mechanical stability.

[0119] Figure 6 Another embodiment of a strip-shaped susceptor assembly 320 is shown, which can replace the double-layer susceptor 120 in Figure 2 The products are used in place of. Figure 6The susceptor assembly 320 is formed of a first susceptor 321 tightly coupled to a second susceptor 322. The first susceptor 321 is a strip of 430 grade stainless steel having dimensions of 12 mm by 4 mm by 35 microns. Thus, the first susceptor 321 defines the basic shape of the susceptor assembly 320. The second susceptor 322 is a patch of mu metal or permalloy having dimensions of 3 mm by 2 mm by 10 microns. The patch-shaped second susceptor 322 is electroplated onto the strip-shaped first susceptor 321. Although the second susceptor 322 is significantly smaller than the first susceptor 321, it is still large enough to allow precise control of the heating temperature. Advantageously, according to Figure 6 The susceptor assembly 320 provides a significant savings in second susceptor material. In other embodiments (not shown), there may be more than one patch of second susceptor positioned in close contact with the first susceptor.

[0120] Figure 7 Shown with Figure 1 and Figure 2 Another embodiment of a susceptor assembly 1020 for use with the article shown. According to this embodiment, the susceptor assembly 1020 forms a susceptor rod. The susceptor rod is cylindrical with a circular cross-section. Preferably, the susceptor rod is centrally arranged within the aerosol-forming substrate so as to extend Figure 2 1020 is a schematic diagram showing a schematic diagram of a susceptor assembly 1020. The susceptor assembly 1020 is a schematic diagram showing a schematic diagram of a susceptor assembly 1020. As can be seen from one of its end faces, the susceptor assembly 1020 comprises an inner core susceptor, which forms a second susceptor 1022 according to the present invention. The core susceptor is surrounded by a sheath susceptor, which forms a first susceptor 1021 according to the present invention. Since the first susceptor 1021 preferably has a heating function, this configuration proves to be advantageous in terms of direct heat transfer to the surrounding aerosol-forming substrate. In addition, the cylindrical shape of the susceptor pin provides a very symmetrical heating profile, which may be advantageous for rod-shaped aerosol-generating articles.

[0121] Figures 8 to 10 Different aerosol-generating articles 400, 500, 600 are schematically shown, which include other embodiments of a susceptor assembly as part of a heating assembly according to the present invention. Figure 1 and Figure 2 The articles 100 shown are very similar, particularly in terms of the general configuration of the articles. Thus, similar or identical features are described with reference to FIG. Figure 1 and Figure 2 The same reference numerals as in are used herein, but are increased by 300, 400 and 500 respectively.

[0122] and Figure 1 and Figure 2 The product 100 shown is compared to the Figure 8The aerosol-generating article 400 comprises a filament susceptor assembly 420. That is, a first susceptor 421 and a second susceptor 422 are filaments twisted with each other to form a twisted filament pair. The filament pair is centrally arranged in the aerosol-forming substrate 430, in direct contact with the substrate 430. The filament pair extends substantially along the extension of the article 400. The first susceptor 421 is a filament made of ferromagnetic stainless steel, and thus has a primary heating function. The second susceptor 422 is a filament made of a high-permeability nickel-iron alloy or permalloy, and thus is primarily used as a temperature marker.

[0123] according to Fig. 9 The aerosol-generating article 500 of the present invention comprises a particle susceptor assembly 520. The first susceptor 521 and the second susceptor 522 each comprise a plurality of susceptor particles dispersed within an aerosol-forming substrate 530 of the article 500. Thus, the susceptor particles are in direct physical contact with the aerosol-forming substrate 530. The susceptor particles of the first susceptor 521 are made of ferromagnetic stainless steel and thus are primarily used to heat the surrounding aerosol-forming substrate 530. In contrast, the susceptor particles of the second susceptor 422 are made of mu metal or permalloy and thus are primarily used as temperature markers.

[0124] according to Fig.10 The aerosol-generating article 600 of the present invention comprises a susceptor assembly 600 including a first susceptor 621 and a second susceptor 622 having different geometric configurations. The first susceptor 621 is a particulate susceptor comprising a plurality of susceptor particles dispersed in an aerosol-forming substrate 630. Due to its particulate nature, the first susceptor 621 has a large surface area to the surrounding aerosol-forming substrate 630, which advantageously enhances heat transfer. Therefore, the particle configuration of the first susceptor 621 is specifically selected with respect to the heating function. In contrast, the second susceptor 622 primarily has a temperature control function and therefore does not need to have a very large surface area. Therefore, the second susceptor 622 of the present embodiment is a susceptor strip extending through the center of the aerosol-generating article 600 within the aerosol-forming substrate 630.

[0125] Fig.11 A second exemplary embodiment of an aerosol generating system 2001 according to the present invention is schematically shown. In addition to the sensor assembly, the system 2001 is Figure 1 The system 1 shown is very similar. Therefore, similar or identical features are represented by Figure 1 and Figure 2 The same reference numerals as in are indicated, but increased by 2000. Figure 1 Compared with the embodiment shown, according to Fig.11 The susceptor assembly 2060 of the heating assembly 2005 of the embodiment is part of the aerosol generating device 2010.

[0126] Thus, the aerosol-generating article 2100 does not include any susceptor components. Thus, the article 2100 substantially corresponds to Figure 1 and Figure 2 The article 100 is shown, but without the susceptor assembly.

[0127] same, Fig.11 The aerosol generating device 2010 substantially corresponds to Figure 1 In contrast to the latter, the device 2010 comprises all the parts of the heating assembly 2005 according to the present invention. That is, the device 2010 comprises an induction source comprising a spiral induction coil 2030 circumferentially surrounding a cylindrical receiving cavity 2020. In addition, the device comprises a susceptor assembly 2060 arranged in the receiving cavity so as to be subjected to the electromagnetic field generated by the induction coil 2030.

[0128] The susceptor assembly 2060 is a susceptor blade. The susceptor blade 2060 is arranged with its distal end 2064 at the bottom portion of the receiving cavity 2020 of the device 2010. From there, the susceptor blade extends towards the opening of the receiving cavity 2020 into the inner void of the receiving cavity 2020. The opening of the receiving cavity 2020 is located at the proximal end 2014 of the aerosol generating device 2010, thereby allowing the aerosol generating article 2100 to be inserted into the receiving cavity 2020.

[0129] from Fig.12 In particular, it can be seen that according to Fig.11 The sensor assembly 2060 of the device 2010 is a double-layer sensor blade, very similar to Figures 1 to 3 The double-layer susceptor assembly 120 is shown. In contrast to the latter, the distal free end 2063 of the susceptor assembly 2060 is tapered so as to allow the blade-shaped susceptor assembly to easily penetrate into the aerosol-forming substrate 2130 within the distal end of the aerosol-generating article 2100.

[0130] In addition, according to Fig.11 The susceptor assembly 2060 and the heating assembly 2005 of the aerosol generating system 2001 are shown with Figure 1 The aerosol generating system has the same resistance-temperature curve, that is, Figure 4 The curve shown in .

[0131] Fig.13 , Fig.14 and Fig.15 Other embodiments of susceptor assemblies 2160, 2260, 2360 according to the present invention are shown, which can be used in conjunction with Fig.11 The sensor components 2160, 2260 and 360 basically correspond to Figure 5 , Figure 6 and Figure 7 The susceptor assemblies 220, 320 and 1020 are shown. Therefore, most of the features and advantages of these susceptor assemblies 2160, 2260, 2360 have been described with respect to the susceptor assemblies 220, 320, 1020 and will not be repeated. Like the susceptor assembly 120, the respective distal free ends 2163, 2263, 2361 of the susceptor assemblies 2160, 2260, 2360 are tapered to facilitate penetration into the aerosol-forming substrate.

[0132] Figures 16 to 18 Other embodiments of the aerosol generating systems 2701, 2801, 2901 of the present invention are schematically shown, wherein each induction heating assembly 2705, 2805, 2905 is only a part of each aerosol generating device 2710, 2810, 2910. The systems 2701, 2801 and 2901 are Fig.11 The system 2001 shown is very similar, particularly in the general arrangement of the apparatus 2710, 2810, 2910 and articles 2700, 2800, 2900. Thus, similar or identical features of the apparatus are described with reference to FIG. Fig.11 The same reference numerals in FIG. 7 represent an increase of 700, 800 and 900, respectively.

[0133] and Fig.11 The device shown in 2010 is compared to the Fig.16 The aerosol generating article 2710 of the aerosol generating system 2701 of the invention includes a susceptor assembly 2760, wherein a first susceptor 2761 and a second susceptor 2762 have different geometric configurations. The first susceptor 2761 is similar to Fig.11 and Fig.12 27. The double-layer susceptor assembly 2060 shown in FIG. 27 shows a single-layer susceptor blade of the double-layer susceptor assembly 2060, but without the second susceptor layer. In this configuration, the first susceptor 1761 essentially forms an induction heating blade, as it primarily has a heating function. In contrast, the second susceptor 2762 is a susceptor sleeve that forms at least a portion of the circumferential inner side wall of the receiving cavity 2720. Of course, the opposite configuration is also possible, in which the first susceptor can be a susceptor sleeve that forms at least a portion of the circumferential inner side wall of the cylindrical receiving cavity 2720, and the second susceptor can be a single-layer susceptor blade to be inserted into the aerosol-forming substrate. In the latter configuration, the first susceptor can realize an induction oven heater or heating chamber. In any of these configurations, the first susceptor 2761 and the second susceptor 2762 are located at different locations within the aerosol generating device 2710, spaced apart from each other but still in thermal proximity to each other.

[0134] Fig.17The aerosol generating device 2810 of the illustrated aerosol generating system 2801 comprises a susceptor assembly 2860 as a susceptor cup, thereby realizing an induction oven heater or heating chamber. In this configuration, the first susceptor 2861 is a susceptor sleeve forming a circumferential side wall of the cup-shaped susceptor assembly 2860, and is therefore at least a portion of the inner side wall of the cylindrical receiving cavity 2820. In contrast, the second susceptor 2862 forms a bottom portion of the cup-shaped susceptor assembly 2860. When the aerosol generating article 2100 is received in the receiving cavity 2820 of the device 2810, the first susceptor 2861 and the second susceptor 2862 are in thermal proximity to the aerosol-forming substrate 2130 of the aerosol generating article.

[0135] Fig.18 The aerosol generating device 2910 of the illustrated aerosol generating system 2901 comprises a susceptor assembly 2960 as a multi-layer susceptor sleeve. In this configuration, the second susceptor 2962 forms the outer wall of the multi-layer susceptor sleeve, while the first susceptor 2961 forms the inner wall of the multi-layer susceptor sleeve. This particular arrangement of the first susceptor 2961 and the second susceptor 2962 is preferred because the first susceptor 2961, which is primarily used for heating the aerosol-forming substrate 2130, is closer to the substrate 2130. Advantageously, the susceptor assembly 2960 also implements an induction oven heater or heating chamber.

[0136] Fig.19 Another exemplary embodiment of an aerosol generating system 3701 according to the present invention is schematically shown. The system 3701 is very similar to Fig.16 Thus, similar or identical features are provided by Fig.16 The same reference numerals as in are indicated, but increased by 1000. Fig.16 Compared with the embodiment shown, according to Fig.16 The susceptor assembly 3760 of the embodiment of the heating assembly 3705 is separate. Although the first susceptor 3761 of the susceptor assembly 3760 is part of the aerosol generating article 3100, the second susceptor 3762 of the susceptor assembly 3760 is part of the aerosol generating device 3710. The first susceptor 3761 is similar to Figures 1 to 3The single layer susceptor strip of the dual layer susceptor assembly 120 shown, but arranged within the aerosol-forming substrate 3130 of the article 3100 and without the second susceptor layer. Thus, the first susceptor 1761 essentially forms an induction heating element as an integral part of the article 3100. The second susceptor 2762 is a susceptor sleeve that forms at least a portion of the circumferential inner side wall of the receiving cavity 2720 to implement an induction oven heater or heating chamber. Although spaced apart from the first susceptor 3761, the second susceptor 3762 is still in thermal proximity to the first susceptor 3761 and the aerosol-forming substrate 3130 and can therefore easily be used as a temperature marker.

[0137] about Figures 16 to 19 For all three embodiments shown, the first susceptor is preferably made of ferromagnetic stainless steel, which is optimized for heating the aerosol-forming substrate. In contrast, the second susceptor is preferably made of mu metal or permalloy, which are suitable temperature marking materials.

Claims

1. An induction heating assembly, the induction heating assembly being configured to inductively heat an aerosol-forming substrate to a predetermined operating temperature, wherein the induction heating assembly comprises: - an induction source configured to generate an alternating electromagnetic field; as well as - a susceptor assembly for inductively heating the aerosol-forming substrate under the influence of the alternating electromagnetic field generated by the induction source, wherein the susceptor assembly comprises a first susceptor having a first susceptor material and a second susceptor having a second susceptor material having a Curie temperature at least 20 degrees Celsius lower than the operating temperature of the heating assembly; a controller operably connected to the induction source and configured to control operation of the induction source, wherein the controller is configured to determine a minimum value of the apparent resistance occurring within a temperature range of ±5 degrees Celsius around the Curie temperature of the second susceptor material during warm-up of the induction heating assembly from room temperature toward an operating temperature.

2. The induction heating assembly according to claim 1, wherein the predetermined operating temperature is at least 300 degrees Celsius, in particular at least 350 degrees Celsius, preferably at least 370 degrees Celsius, most preferably at least 400 degrees Celsius.

3. The induction heating assembly according to any of the preceding claims, wherein the Curie temperature of the second susceptor material is at least 50 degrees Celsius, in particular at least 100 degrees Celsius, preferably at least 150 degrees Celsius, most preferably at least 200 degrees Celsius below the operating temperature.

4. The induction heating assembly according to any of the preceding claims, wherein the Curie temperature of the second susceptor material is below 350 degrees Celsius, in particular below 300 degrees Celsius, preferably below 250 degrees Celsius, most preferably below 200 degrees Celsius.

5. The induction heating assembly of any one of the preceding claims, wherein the second susceptor comprises one of mu metal or permalloy.

6. An induction heating assembly according to any one of the preceding claims, wherein the first susceptor material is electrically conductive and / or one of paramagnetic, ferromagnetic or ferrimagnetic.

7. The induction heating assembly of any one of the preceding claims, wherein the first susceptor material comprises one of aluminum, iron, nickel, copper, bronze, cobalt, plain carbon steel, stainless steel, ferritic stainless steel, martensitic stainless steel, or austenitic stainless steel.

8. An induction heating assembly according to any one of the preceding claims, wherein the first susceptor material has a positive temperature coefficient of resistance, and wherein the second susceptor material has a negative temperature coefficient of resistance.

9. The induction heating assembly of any one of the preceding claims, wherein the first susceptor and the second susceptor are in close physical contact with each other.

10. The induction heating assembly according to any one of the preceding claims, wherein the first susceptor or the second susceptor or both the first susceptor and the second susceptor, in particular the entire susceptor assembly, is one of a granular susceptor, or a susceptor filament, or a susceptor mesh, or a susceptor core, or a susceptor pin, or a susceptor rod, or a susceptor blade, or a susceptor strip, or a susceptor sleeve, or a susceptor cup, or a cylindrical susceptor, or a planar susceptor.

11. An induction heating assembly according to any preceding claim, the controller being configured to control operation of the induction source in a closed loop configuration for controlling heating of the aerosol-forming substrate to the predetermined operating temperature.

12. An induction heating assembly according to any one of the preceding claims, comprising a DC power supply configured to provide a DC supply voltage and a DC supply current to the induction source.

13. An aerosol generating device for generating an aerosol by heating an aerosol-forming substrate, the aerosol generating device comprising: - a receiving chamber for receiving the aerosol-forming substrate to be heated; and - An induction heating assembly according to any one of the preceding claims, for inductively heating the aerosol-forming substrate within the receiving cavity.

14. An aerosol generating system, comprising an aerosol generating device, an aerosol generating article for use with the aerosol generating device, and an induction heating component according to any one of claims 1 to 12, wherein the induction source of the heating component is part of the aerosol generating device, wherein the first sensor of the sensor component is part of the aerosol generating article, and wherein the second sensor of the sensor component is part of the aerosol generating article or part of the aerosol generating device.

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