RU2793731C2 - Induction heating unit for induction heating of aerosol forming substrate - Google Patents

Abstract

FIELD: aerosols.

SUBSTANCE: induction heating unit, an aerosol generating device and an aerosol generating system. The heating unit contains an induction source configured to generate an alternating electromagnetic field. The heating unit also includes a susceptor unit for inductive heating of the aerosol-forming substrate under the action of an alternating magnetic field generated by the induction source. The susceptor unit comprises a first susceptor containing the material of the first susceptor and a second susceptor. The second susceptor comprises a second susceptor material having a Curie temperature of at least 50 degrees Celsius below the operating temperature of the heating unit.

EFFECT: provision of accurate temperature control.

15 cl, 19 dwg

Description

The present invention relates to an induction heating unit for induction heating of an aerosol-forming substrate. The present invention also relates to an aerosol generating device and an aerosol generating system comprising such an induction heating unit.

Aerosol generating systems based on inductive heating of an aerosol-forming substrate that is capable of producing an inhalable aerosol when heated are well known in the art. To heat the aerosol-forming substrate, such systems may comprise an induction heating assembly comprising an induction source and a susceptor (current collector). The induction source is configured to generate an alternating electromagnetic field that induces at least one of the heat-generating eddy currents or hysteresis losses in the susceptor (current collector). Although the induction source is usually part of the aerosol generating device, the susceptor (current collector) may be either part of the device or an integral part of the aerosol generating article that is configured to be placed in the aerosol generating device containing the induction source. In any case, the susceptor (current collector) is located in such a way that it is in thermal proximity to the substrate or in direct physical contact with it during operation of the system.

To regulate the temperature of the substrate, susceptor (current-collecting) units have been proposed, containing the first and second susceptors (current-collectors) made of different materials. The material of the first susceptor (current collector) is optimized in terms of heat loss and thus heating efficiency. In contrast, the material of the second susceptor (current collector) is used as a temperature marker. To do this, the material of the second susceptor (current collector) is chosen so that it has a Curie temperature corresponding to the specified operating temperature of the susceptor (current collector) assembly. The magnetic properties of the second susceptor (current collector) at its Curie temperature change from ferromagnetic or ferrimagnetic to paramagnetic, which is accompanied by a temporary change in its electrical resistance. Thus, by monitoring the corresponding change in the electrical current drawn by the induction source, it is possible to determine the moment when the material of the second susceptor (current collector) has reached its Curie temperature and thus the moment when the desired operating temperature has been reached.

However, when monitoring the change in electric current drawn by the induction source, it can be difficult to distinguish between the situation where the material of the second susceptor (current collector) has reached its Curie temperature, and the situation when the user takes a puff, in particular the first puff, during which the electric current shows similar change in performance. The change in electric current during a puff by the user is due to the cooling of the susceptor (current-collecting) assembly due to air being drawn through the aerosol generating article during the puff by the user. Cooling leads to a temporary change in the electrical resistance of the susceptor (current-collecting) node. This, in turn, leads to a corresponding change in the electric current consumed by the induction source. Typically, cooling of the susceptor (current-collecting) assembly during a puff by the user is counteracted by the controller by temporarily increasing the heating power. However, this controller-initiated temporary increase in heating power can have the adverse effect of undesirably overheating the susceptor (current collector) assembly, in case the observed change in electric current, which is actually due to the fact that the material of the second susceptor (current collector) has reached its Curie temperature, misidentified as a user puff.

Therefore, it would be desirable to have an induction heating unit with the advantages of prior art solutions, but without their limitations. In particular, it would be desirable to have an induction heating unit that would allow improved temperature control.

The present invention provides an induction heating assembly configured to inductively heat an aerosol-forming substrate to a predetermined operating temperature. The heating unit contains an induction source configured to generate an alternating electromagnetic field. The heating unit also contains a susceptor (current-collecting) unit for inductively heating the aerosol-forming substrate under the action of an alternating magnetic field generated by the induction source. Susceptor (current collector) node contains the first susceptor (current collector), containing the material of the first susceptor (current collector), and the second susceptor (current collector). Preferably, the second susceptor (current collector) comprises a second susceptor (current collector) material having a Curie temperature of at least 20 degrees Celsius below the operating temperature of the heating unit.

According to the present invention, it has been found that a temperature gap of at least 20 degrees between the Curie temperature of the second susceptor (current collector) material and the operating temperature of the heating assembly is large enough to reliably use the Curie temperature of the second susceptor (current collector) material as a temperature marker for temperature control. heating the aerosol-forming substrate without the risk of misinterpretation as a consequence of puffing by the user.

Preferably, the material of the second susceptor (current collector) has a Curie temperature of 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. Celsius below operating temperature. Increasing the temperature gap between the Curie temperature of the second susceptor (current collector) material and the operating temperature of the heating unit provides the advantage of improving the correct identification of the temperature marker and thus improving the reliability of temperature control.

Said desired operating temperature 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, the aerosol-forming substrate.

Accordingly, the material of the second susceptor (current collector) is chosen so that it has a Curie temperature 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 the typical operating temperatures used to heat the aerosol-forming substrate. This ensures correct identification of the temperature marker.

In the context of this document, the term "susceptor (current collector)" means an element that is capable of converting electromagnetic energy into heat when exposed to an alternating electromagnetic field. This may be the result of hysteresis losses and/or eddy currents induced in the susceptor (current collector), depending on the electrical and magnetic properties of the susceptor (current collector) material. Hysteresis losses occur in ferromagnetic or ferrimagnetic susceptors (current collectors) due to the remagnetization of magnetic domains inside the material under the action of an alternating electromagnetic field. Eddy currents can be induced if the susceptor (current collector) is electrically conductive. In the case of an electrically conductive ferromagnetic or ferrimagnetic susceptor (current collector), heat can be generated due to both eddy currents and hysteresis losses.

According to the present invention, the material of the second susceptor (current collector) is at least a ferrimagnet or a ferromagnet having a particular Curie temperature. The Curie temperature is the temperature above which a ferrimagnetic or ferromagnetic material loses its ferrimagnetism or ferromagnetism, respectively, and becomes paramagnetic. In addition to being ferrimagnetic or ferromagnetic, the material of the second susceptor (current collector) may also be electrically conductive.

Preferably, the material of the second susceptor (current collector) may contain one of mu-metal or permalloy.

While the second susceptor (current collector) is primarily configured to monitor the temperature of the susceptor (current collector) assembly, the first susceptor (current collector) is preferably configured to heat the aerosol-forming substrate. To this end, the first susceptor (current collector) can be optimized in terms of heat loss and thus heating efficiency. Accordingly, the material of the first susceptor (current collector) may be electrically conductive and/or be one of a paramagnet, a ferromagnet, or a ferrimagnet. If the material of the first susceptor (current collector) is ferromagnetic or ferrimagnetic, then the corresponding Curie temperature of the material of the first susceptor (current collector) is preferably different from the Curie temperature of the second susceptor (current collector), in particular it is higher than any of the above typical operating temperatures used for heating aerosol-forming substrate. For example, the material of the first susceptor (current collector) may have a Curie temperature of at least 400 degrees Celsius, in particular at least 500 degrees Celsius, preferably at least 600 degrees Celsius.

For example, the material of the first susceptor (current collector) may contain one of the following: aluminum, iron, nickel, copper, bronze, cobalt, unalloyed carbon steel, stainless steel, ferritic stainless steel, martensitic stainless steel, or austenitic stainless steel.

Preferably, the material of the first susceptor (current collector) has a positive temperature coefficient of resistance, while the material of the second susceptor (current collector) preferably has a negative temperature coefficient of resistance. According to the present invention, it has been found that a susceptor (current collector) assembly containing two susceptor (current collector) materials having opposite temperature coefficients of resistance has a resistance versus temperature profile that includes a minimum resistance value in the vicinity of the Curie temperature of the material of the second susceptor (current collector) , for example, in the vicinity of ±5 degrees Celsius relative to the Curie temperature of the material of the second susceptor (current collector). Preferably, this minimum value is the absolute minimum of the resistance versus temperature profile. This minimum is due to the opposite temperature behavior of the corresponding electrical resistance of the first and second susceptor (current collector) materials and the magnetic properties of the material of the second susceptor (current collector). After the start of heating the susceptor (current collector) assembly from room temperature, the resistance of the material of the first susceptor (current collector) increases, while the resistance of the material of the second susceptor (current collector) decreases with increasing temperature. The total apparent resistance of the susceptor (current collector) assembly "seen" by the induction source used to inductively heat the susceptor (current collector) assembly is determined by the combination of the respective resistances of the first and second susceptor (current collector) materials. When the Curie temperature is reached by the material of the second susceptor (current collector) from below, the decrease in the resistance of the material of the second susceptor (current collector) usually prevails over the increase in the resistance of the material of the first susceptor (current collector). Accordingly, the overall apparent resistance of the susceptor (current collector) assembly decreases in a temperature range below, in particular approximately below, the Curie temperature of the material of the second susceptor (current collector). At the Curie temperature, the material of the second current collector loses its magnetic properties. This leads to an increase in the surface layer available for eddy currents in the second current-collecting material, which is accompanied by a sharp drop in its resistance. Thus, with a further increase in the temperature of the current collector above the Curie temperature of the material of the second current collector, the contribution of the resistance of the material of the second current collector to the total apparent resistance of the current collector becomes smaller or even negligible. Therefore, after passing the minimum value in the vicinity of the Curie temperature of the material of the second current collector, the total apparent resistance of the current collector assembly is mainly determined by the increase in the resistance of the material of the first current collector. In other words, the total apparent resistance of the current collector increases again. The decrease and subsequent increase in the resistance versus temperature profile in the vicinity of the minimum resistance value at approximately the Curie temperature of the second current collector material provides the advantage that it is sufficiently distinguishable from the temporal change in the total apparent resistance during user tightening. As a result, it is possible to reliably use the minimum resistance value in the vicinity of the Curie temperature of the material of the second current collector as a temperature marker for controlling the heating temperature of the aerosol-forming substrate without the risk of its misinterpretation as a consequence of the user puffing. Accordingly, the efficiency of preventing unwanted overheating of the aerosol-forming substrate is further improved.

Preferably, the first current collector and the second current collector are in close physical contact with each other. In particular, the first and second current collectors may form a single current collector assembly. Thus, when heated, the first and second current collectors have substantially the same temperature. Due to this, the temperature control of the first pantograph by the second pantograph is very accurate. Close contact between the first current collector and the second current collector may be realized by any suitable means. For example, the second current collector may be applied to the second current collector by electroplating, deposition, coating, cladding, or welding. Preferred methods include electroplating (electroplating), cladding, dip plating, or roll plating.

The current-collecting assembly according to the present invention is preferably configured to be activated by an alternating, in particular high-frequency, electromagnetic field. In the context of this document, the high frequency electromagnetic field may range from 500 kHz (kilohertz) to 30 MHz (megahertz), in particular from 5 MHz (megahertz) to 15 MHz (megahertz), preferably from 5 MHz (megahertz) to 10 MHz ( megahertz).

Each of the first pantograph and the second pantograph or current collector assembly may have a variety of geometric configurations. At least one of the first pantograph, the second pantograph, or the pantograph assembly may be one of the following: a particulate pantograph, or a current-collector filament, or a current-collector mesh, or a current-collector wick, or a current-collector pin, or a current-collector rod, or a current-collector blade, or a current-collecting strip, or a current-collecting sleeve, or a current-collecting bowl, or a cylindrical current-collector, or a planar current-collector.

By way of example, at least one of the first pantograph, the second pantograph, or the pantograph assembly may be one of a filamentous pantograph, a mesh pantograph, or a wick pantograph. Such current collectors may have advantages in terms of their manufacture, geometric ordering and reproducibility, as well as their capillary function. Geometrical order and reproducibility can provide an advantage in terms of both temperature control and controlled localized heating. The capillary function may provide an advantage when used with a liquid aerosol-forming substrate. In use, any of these current collectors may be in direct physical contact with the aerosol-forming substrate to be heated. For example, the first and/or second filamentous current collector may be embedded within the aerosol-forming substrate of the aerosol-generating article. Similarly, the first and/or second current collector may be a mesh current collector or a wick current collector, either as part of an aerosol-generating article, which preferably contains a liquid aerosol-generating substrate, or as part of an aerosol-generating device. In the latter configuration, the device may comprise a reservoir for a liquid aerosol-forming substrate. Alternatively, the device may be configured to receive an aerosol-generating article, in particular a cartridge that contains a liquid aerosol-generating substrate and is configured to interact with a filamentous current collector or mesh current collector or wick current collector of the aerosol generating device.

At least one of the first current collector, the second current collector, or the current collector assembly may be a current collector blade or a current collector rod or a current collector pin. Preferably, the first current collector and the second current collector together form a current-collecting blade or a current-collecting rod or a current-collecting pin. For example, one of the first or second current collectors may form the core or inner layer of the current collector blade or current collector rod or current collector pin, while the corresponding other of the first or second current collector may form a coating or sheath of the current collector blade or current collector rod or current collector pin.

As a current collector blade or a current collector rod or a current collector pin, at least one of the first current collector, second current collector or current collector assembly may be part of the aerosol generating article, in particular it may be located within the aerosol generating substrate of the aerosol generating article. One extreme end of the current-collecting blade or the current-collecting rod or the current-collecting pin may be tapered or pointed to facilitate insertion of the current-collector blade or the current-collector rod or the current-collector pin into the aerosol-forming substrate of the article.

Alternatively, at least one of the first current collector, the second current collector, or the current collector assembly, each in the form of a current collector blade or current collector rod or current collector pin, may be part of an aerosol generating device. With one of its ends, in particular the distal end, the current-collecting blade or the current-collecting rod or the current-collecting pin can be located in the lower part of the receiving cavity of the device, in particular, fixed in it. From here, the current-collecting blade or the current-collecting rod or the current-collecting pin preferably extends into the interior of the receiving cavity towards the opening of the receiving cavity. The receiving cavity opening is preferably located at the proximal end of the aerosol generating device. The other end, i.e. the distal free end, of the current-collecting blade or the current-collecting rod or the current-collecting pin may be tapered or pointed so as to allow the current-collecting blade or the current-collecting rod or the current-collecting pin to easily penetrate into the aerosol-forming substrate to be heated, for example, into the aerosol-generating substrate. a substrate located at the far end of the aerosol generating article.

In each case, the current-collecting blade or the current-collecting rod or the current-collecting pin may have a length in the range from 8 mm (millimeters) to 16 mm (millimeters), in particular from 10 mm (millimeters) to 14 mm (millimeters), preferably 12 mm (millimeters) . In the case of a current collector blade, the first current collector and/or the second current collector, in particular the current collector unit, may have a width, for example, in the range from 2 mm (millimeters) to 6 mm (millimeters), in particular from 4 mm (millimeters) to 5 mm ( millimeters). Similarly, the thickness of the first plate-shaped current collector and/or the second plate-shaped current collector, in particular the plate-shaped current collector assembly, preferably ranges from 0.03 mm (millimeter) to 0.15 mm (millimeter), more preferably from 0 .05 mm (millimeter) to 0.09 mm (millimeter).

At least one of the first pantograph, the second pantograph or the pantograph assembly may be a cylindrical pantograph or a current collector sleeve or a current collector cup. A cylindrical current collector, a current collector sleeve, or a current collector cup may form a receptacle, or they may be arranged circumferentially around the receptacle of an aerosol generating device, of which the heating assembly may be a part. In this configuration, the first and/or second current collector or current collector assembly forms an induction heating furnace or heating chamber configured to receive an aerosol-forming substrate to be heated therein. Alternatively, at least one of the first current collector, the second current collector, or the current collector assembly, each in the form of a cylindrical current collector or a current collector sleeve or a current collector cup, may surround at least a portion of the aerosol-forming substrate to be heated, thereby forming a heating oven or a heating furnace. camera. In particular, each of them may form at least part of the shell, wrapper, body or casing of the aerosol generating article.

The current collector assembly may be a multilayer current collector assembly. In this case, the first current collector and the second current collector can form layers, in particular adjacent layers, of a multilayer current collector assembly.

In a multilayer current collector assembly, the first current collector and the second current collector may be in close physical contact with each other. Due to this, the temperature control of the first pantograph by the second pantograph is sufficiently accurate, since the first and second pantographs have essentially the same temperature.

The second current collector may be applied to the first current collector by galvanization, deposition, coating, cladding, or welding. Preferably, the second current collector is applied to the first current collector by spraying, dip coating, roll coating, electroplating or cladding.

Preferably, the second current collector 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 at the Curie temperature.

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

The multilayer current collector assembly can be used to implement different geometries of the current collector assembly.

For example, the multi-layer susceptor assembly may be an elongated susceptor strip or a susceptor blade having a length in the range of 8 mm (millimeters) to 16 mm (millimeters), in particular 10 mm (millimeters) to 14 mm (millimeters), preferably 12 mm (millimeters). The width of the current collector can be, for example, in the range from 2 mm (millimeters) to 6 mm (millimeters), in particular from 4 mm (millimeters) to 5 mm (millimeters). The thickness of the current collector is preferably in the range of 0.03 mm (millimeter) to 0.15 mm (millimeter), more preferably 0.05 mm (millimeter) to 0.09 mm (millimeter). The multilayer susceptor blade may have a free tapered end.

As an example, the multi-layer current collector assembly may be an elongate strip having a first current collector which is a 430 stainless steel strip having a length of 12 mm (millimeters), a width of 4 mm (millimeters) to 5 mm (millimeters), for example 4 mm (millimeters), and a thickness of approximately 50 microns (micrometers). 430 stainless steel can be coated with a layer of mu-metal or permalloy as a second current collector having a thickness of 5 microns (micrometers) to 30 microns (micrometers), for example 10 microns (micrometers).

The term "thickness" is used herein to refer to dimensions extending between the top and bottom sides, such as between the top side and bottom side of a layer, or the top side and bottom side of a multilayer current collector assembly. The term "width" is used in this document to refer to the dimensions extending between two opposite sides. The term "length" is used in this document to refer to dimensions extending between the front and back, or between other two opposite sides, perpendicular to two opposite sides, forming a width. Thickness, width and length can be perpendicular to each other.

Similarly, the multi-layer current-collecting assembly may be a multi-layer current-collecting rod or a multi-layer current-collecting pin, such as those previously described. In this configuration, one of the first or second current collectors may form a core layer that is surrounded by a surrounding layer formed by the corresponding other of the first or second current collectors. Preferably, it is the first current collector that forms the surrounding layer in case the first current collector is optimized for heating the substrate. In this way, heat transfer to the surrounding aerosol-forming substrate is improved.

Alternatively, the multi-layer current collector assembly may be a multi-layer current collector sleeve or a multi-layer current collector bowl or a cylindrical multi-layer current collector, in particular as described previously. One of the first or second current collectors may form the inner wall of the multilayer current collector sleeve or the multilayer current collector bowl or the cylindrical multilayer current collector. A corresponding other of the first or second current collectors can form the outer wall of the multilayer current collector sleeve or the multilayer current collector bowl or the cylindrical multilayer current collector. Preferably, it is the first current collector that forms the inner wall, in particular if the first current collector is optimized for heating the substrate. As described above, the multi-layer current collector sleeve or the multi-layer current collector cup or the cylindrical multi-layer current collector may surround at least a portion of the aerosol-generating substrate to be heated, in particular, they may form at least a portion of the sheath, wrapper, body, or housing of the aerosol-generating article. Alternatively, a multi-layer current collector sleeve or a multi-layer current collector cup or a cylindrical multi-layer current collector may form a receiving cavity, or they may be located circumferentially around the receiving cavity of an aerosol generating device, of which the heating assembly may be a part.

For example, for purposes of manufacturing an aerosol generating article, it may be desirable for the first and second current collectors to have similar geometries, such as those described above.

Alternatively, the first pantograph and the second pantograph may have different geometries. Thus, the first and second pantographs can be adapted for their particular function. The first current collector, preferably having a heating function, may have a geometric configuration that provides a large surface area for the aerosol-forming substrate to improve heat transfer. In contrast, the second pantograph, which preferably has a temperature control function, need not have a very large surface area. If the material of the first current collector is optimized for heating the substrate, then it may be preferable that the volume of the material of the second current collector does not exceed the volume necessary to provide a detectable Curie temperature.

According to this aspect, the second pantograph may include one or more elements of the second pantograph. Preferably, said one or more elements of the second pantograph are significantly smaller than the first pantograph, that is, they have a volume less than the volume of the first pantograph. Each of the one or more elements of the second pantograph may be in close physical contact with the first pantograph. As a result, the first and second pantographs have substantially the same temperature, which improves the accuracy of temperature control of the first pantograph by the second pantograph serving as a temperature marker.

For example, the first current collector may be in the form of a current collector blade or a current collector strip or a current collector sleeve or a current collector bowl, while the second current collector material may be in the form of separate patches that are applied to the first current collector material by galvanization, deposition or welding.

According to another example, the first susceptor may be a strip susceptor or a filamentary susceptor or a mesh susceptor while the second susceptor is a particulate susceptor. Both the filamentous or mesh first current collector and the second particulate current collector may, for example, be incorporated into the aerosol generating article and be in direct physical contact with the aerosol generating substrate to be heated. In this particular configuration, the first current collector may extend within the aerosol-generating substrate through the center of the aerosol-generating article, while the second current collector may be evenly distributed throughout the aerosol-generating substrate.

The first and second current collectors need not be in close physical contact with each other. The first current collector may be a current-collecting blade forming a heating blade for penetrating the aerosol-forming substrate to be heated. Similarly, the first current collector may be a current-collecting sleeve or a current-collecting cup forming a heating furnace or a heating chamber. In either of these configurations, the second pantograph may be located elsewhere within the heating assembly, at a distance from the first pantograph, but still in thermal proximity to the first pantograph.

The first and second current collectors may form different parts of the current collector assembly. For example, the first current collector may form a side wall portion or sleeve portion of the cup-shaped current collector assembly, while the second current collector forms the bottom of the cup-shaped current collector assembly.

At least a portion of at least one of the first current collector and the second current collector may comprise a protective coating. Similarly, at least a portion of the current collector assembly may comprise a protective coating. The protective coating may be formed by glass, ceramic or inert metal formed or coated over at least a portion of the first current collector and/or the second current collector or current collector assembly, respectively. Preferably, the protective coating may be configured to at least one of the following: prevent adhesion of the aerosol-forming substrate to the surface of the current collector, prevent diffusion of material, such as metal diffusion, from the susceptor materials into the aerosol-forming substrate, and increase the mechanical rigidity of the current collector assembly. Preferably, the protective coating is non-conductive.

To generate an alternating electromagnetic field, the induction source may comprise at least one inductor, preferably at least one inductor.

The induction source may comprise a single inductor or a plurality of inductors. The number of inductors may depend on the number of current collectors and/or the size and shape of the current collector assembly. The coil or coils may be shaped to match the shape of the first and/or second current collector or current collector assembly, respectively. Similarly, the coil or coils may be shaped to match the shape of the body of the aerosol generating device, of which the heating assembly may be a part.

Said at least one inductor may be a helical coil or a flat planar coil, in particular a disk coil or a curved planar coil. The use of a flat helical coil allows a compact design that is reliable and inexpensive to manufacture. The use of a helical inductor provides the advantage of being able to generate a uniform alternating electromagnetic field. In the context of this document, the term "flat helical coil" means a coil that is generally a planar coil, the winding axis of this coil being perpendicular to the plane in which the coil lies. The flat helical inductor may be of any desired shape in the plane of the coil. For example, a flat helical coil may be circular in shape, or it may be generally oblong or rectangular in shape. However, the term "flat helical coil" in the context of this document covers both coils that are planar and flat helical coils whose shape conforms to a curved surface. For example, the inductor may be a "curvilinear" planar coil located around the circumference of a preferably cylindrical coil support, such as a ferrite core. In addition, the flat helical coil may comprise, for example, two layers of a four-turn flat helical coil or one layer of a four-turn flat helical coil.

The first and/or second inductor may be held within one of the heating assembly housing or the main body or casing of the aerosol generating device that contains said heating assembly. The first and/or second inductor may be wound around a preferably cylindrical coil support, such as a ferrite core.

The induction source may comprise an alternating current (AC) generator. The alternator may be powered by a power source of the aerosol generating device. The alternator is operatively connected to said at least one inductor. In particular, said at least one inductor may be an integral part of the alternator. The alternator is configured to generate a high frequency oscillatory current for passing through said at least one inductor to generate an alternating electromagnetic field. The alternating current may be applied to said at least one inductor continuously after activation of the system, or it may be applied intermittently, for example from puff to puff.

Preferably, the inductive source comprises a DC/AC converter coupled to a DC power source comprising an inductive-capacitive circuit that includes a series connection of a capacitor and an inductor.

The induction source is preferably configured to generate a high frequency electromagnetic field. In the context of this document, the high frequency electromagnetic field may range from 500 kHz (kilohertz) to 30 MHz (megahertz), in particular from 5 MHz (megahertz) to 15 MHz (megahertz), preferably from 5 MHz (megahertz) to 10 MHz (megahertz).

The heating unit may also include a controller configured to control the operation of the heating unit. In particular, the controller may be configured to control the operation of the induction source, preferably in a closed loop configuration, to control the heating of the aerosol-forming substrate to a predetermined operating temperature. As mentioned above, the operating temperature used to heat 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, the aerosol-forming substrate.

The controller may comprise a microprocessor, such as a programmable microprocessor, microcontroller, or application specific integrated circuit (ASIC), or other electronic circuit capable of providing control. The controller may include additional electronic components such as at least one DC/AC converter and/or power amplifiers, such as a class D or class E power amplifier. In particular, an induction source may be part of the controller.

The controller may be a general controller or part of a general controller of the aerosol generating device of which the heating assembly according to the present invention is a part.

The controller and at least part of the induction source, in particular the induction source with the exception of the inductor, can be located on a common printed circuit board. This provides a particular advantage in terms of the compact design of the heating unit.

The controller can be configured to determine, during the preheating of the current collector from room temperature towards the operating temperature, the minimum value of the apparent impedance achieved in the temperature range of ±5 degrees Celsius in the vicinity of the Curie temperature of the material of the second current collector. This provides the advantage of being able to correctly identify a temperature marker near the Curie temperature of the second current collector material. To do this, the controller may be generally configured to determine, based on the supply voltage, in particular the DC supply voltage supplied from the power supply, the actual apparent resistance of the current collector, which in turn is indicative of the actual temperature of the current collector.

To determine the actual apparent resistance of the current collector, which is indicative of the actual temperature of the current collector, the controller of the heating node may comprise at least one of a voltage sensor, in particular a DC voltage sensor, for measuring the supply voltage, in particular the DC voltage supplied from the source power, or a current sensor, in particular a DC sensor, for measuring the supply current, in particular the DC supply supplied from the power supply.

In addition, the controller may be configured to control the operation of the induction source in a closed loop configuration such that the actual apparent resistivity corresponds to the sum of the determined apparent resistivity value and the predetermined apparent resistivity offset value to control the heating of the aerosol-forming substrate to the operating temperature. In this aspect, heating temperature control is preferably based on the principles of bias clamping or bias control using a predetermined apparent resistivity bias to bridge the gap between the apparent resistivity measured at the marker temperature and the apparent resistivity at operating temperature. This provides the advantage of avoiding direct control of the heating temperature based on a predetermined target value of apparent resistance at operating temperature and thus avoiding misinterpretation of the measured resistance value.

In addition, heating temperature offset control is more stable and reliable than temperature control based on measured absolute values of apparent resistivity at the desired operating temperature. This is because the measured absolute value of the apparent resistance, determined on the basis of the supply voltage and supply current, depends on various factors such as the resistance of the electrical circuit of the induction source and various contact resistances. Such factors are influenced by the environment and may change over time and/or between different induction sources and current collectors of the same type, depending on production. Preferably, such effects essentially negate the value of the difference between the measured absolute values of the apparent resistivity. Accordingly, the use of an apparent resistivity offset value for temperature control is less susceptible to such adverse effects and changes.

The apparent resistivity shift value for controlling the heating temperature of the aerosol-forming substrate to the operating temperature can be predetermined by means of a calibration measurement, for example, during manufacture of the device.

Preferably, the minimum resistance value at approximately the Curie temperature of the second current collector material is the absolute minimum of the resistance versus temperature profile.

In the context of this document, the term "starting at room temperature" preferably means that the minimum resistance value at approximately the Curie temperature of the second current collector material is reached on the resistance-temperature profile during preheating, i.e. heating the current collector assembly from room temperature to operating temperature, up to which the aerosol-forming substrate is to be heated.

In the context of this document, room temperature may correspond to a temperature in the range from 18 degrees Celsius to 25 degrees Celsius, in particular at a temperature of 20 degrees Celsius.

The heating unit may comprise a power source, in particular a DC power source configured to supply a DC supply voltage and a DC supply to the induction source. Preferably, the power source is a battery such as a lithium iron phosphate battery. Alternatively, the power supply may be another type of charge storage device, such as a capacitor. The power supply may need to be recharged, ie the power supply may be rechargeable. The power supply may have a capacity that allows sufficient energy to be stored for one or more uses. For example, the power supply may have sufficient capacity to allow continuous generation of the aerosol for a period of approximately six minutes, or for a period in multiples of six minutes. In yet another example, the power source may have sufficient capacity to allow for a given number of puffs or individual activations of the induction source. The power source may be a common power source for the aerosol generating device of which the heating assembly of the present invention is a part.

The present invention also provides an aerosol generating apparatus for generating an aerosol by heating an aerosol-forming substrate. The device comprises a receiving cavity for receiving an aerosol-forming substrate to be heated. The device further comprises an induction heating assembly according to the present invention described herein for inductively heating an aerosol-forming substrate within a receiving cavity.

In the context of this document, the term "aerosol-generating device" is used to describe an electrical device that is capable of interacting with at least one aerosol-generating substrate, in particular an aerosol-generating substrate provided within an aerosol-generating article, so as to generate an aerosol by heating the substrate. . Preferably, the aerosol generating device is an inhalation device for generating an aerosol that is directly inhaled by the user through the mouth. In particular, the aerosol generating device is a hand held aerosol generating device.

In the context of this document, the term "aerosol-forming substrate" refers to a substrate capable of releasing volatile compounds that can form an aerosol when the aerosol-forming substrate is heated. The aerosol-generating substrate is part of the aerosol-generating article. The aerosol-forming substrate may be a solid or, preferably, a liquid aerosol-forming substrate. In both cases, the aerosol-forming substrate may contain at least one of solid and liquid components. The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavor compounds that are released from the substrate upon heating. Alternatively or additionally, the aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may further comprise an aerosol-forming agent. Examples of suitable aerosol forming agents are glycerin and propylene glycol. The aerosol-forming substrate may also contain other additives and ingredients such as nicotine or flavors. The aerosol-forming substrate may also be a pasty material, a pouch of porous material containing an aerosol-forming substrate, or, for example, loose tobacco mixed with a gelling agent or adhesive; it may contain a conventional aerosolizing agent such as glycerin and be compressed or molded into a plug.

The receiving cavity may be provided inside the body of the aerosol generating device.

As described above, the aerosol generating device may include a common controller to control the operation of the device. The common controller may or may include a heating unit controller.

As further described above, the aerosol generating device may also comprise a power source, in particular a DC power source such as a battery. In particular, the power supply may be a common power supply of the aerosol generating device, which is used, among other things, to supply the DC power supply voltage and the DC power supply to the induction source of the heating unit.

The aerosol generating device may comprise a main body which preferably comprises at least one of an induction source, said at least one inductor, a controller, a power source, and at least a portion of the receiving cavity.

In addition to the main body, the aerosol generating device may also comprise a mouthpiece, in particular in case the aerosol generating article to be used with the device does not comprise a mouthpiece. The mouthpiece can be mounted on the main body of the device. The mouthpiece may be configured to close the receiving cavity when the mouthpiece is mounted on the main body. To attach the mouthpiece to the main body, the proximal end portion of the main body may include a magnetic or mechanical fastener, such as a bayonet or snap fastener, that engages with a corresponding counterpart at the distal end portion of the mouthpiece. If the device does not include a mouthpiece, then the aerosol generating article to be used with the aerosol generating device may include a mouthpiece, such as a filter plug.

The aerosol generating device may include at least one air outlet, such as an air outlet in a mouthpiece (if any).

Preferably, the aerosol generating device comprises an air path extending from the at least one air inlet, through the receiving cavity, and possibly further to the mouthpiece air outlet, if any. Preferably, the aerosol generating device comprises at least one air inlet in fluid communication with the receiving cavity. Accordingly, the aerosol generating system may include an air path extending from the at least one air inlet to the receiving cavity and possibly further through the aerosol generating substrate within the article and through the mouthpiece into the wearer's mouth.

Additional features and advantages of the aerosol generating article according to the present invention have already been described in relation to the heating unit and will not be described again.

The present invention also provides 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 described herein. The induction source of the heating unit is part of the aerosol generating device. The first current collector of the current collector assembly is part of an aerosol generating article, while the second current collector of the current collector assembly is either a part of an aerosol generating article or a part of an aerosol generating device.

Preferably, the first current collector as part of the aerosol generating article may be configured to heat the aerosol generating substrate. To this end, the first pantograph can be optimized with regard to heat loss and thus heating efficiency. For example, the first current collector may be a current collector strip, a current collector blade, a current collector rod, a current collector pin, a current collector mesh, a current collector thread, or a particulate current collector located together with the aerosol-forming substrate of the aerosol generating article.

In contrast, the second pantograph may be primarily configured to monitor the temperature of the pantograph. To this end, the second current collector can be part of either the aerosol-generating article or the aerosol-generating device, in particular it can be located in them. In any configuration, if the article is used with, in particular connected to, the device, the second current collector is preferably located in thermal proximity or even in thermal contact with the first current collector and/or the aerosol-forming substrate. This provides the advantage that the second current collector has substantially the same temperature as the first current collector and/or the aerosol generating substrate during operation of the aerosol generating system. In this way, it is possible to achieve proper and accurate temperature control. For example, the second current collector may be located on the inner wall of the receiving cavity of the aerosol generating device.

If present, the controller of the heating unit may be part of the aerosol generating device, in particular be located in it. Preferably, the controller of the aerosol generating device may comprise or may be a heating unit controller.

Similarly, if present, the power source of the heating unit may be part of the aerosol generating device, in particular be located in it. Preferably, the power source for the aerosol generating device may comprise or may be a power source for a heating unit.

The aerosol generating device may include a receiving cavity for receiving at least a portion of the aerosol generating article.

In the context of this document, the term "aerosol-generating article" refers to an article containing at least one aerosol-forming substrate, which, when heated, releases volatile compounds capable of forming an aerosol. Preferably, the aerosol generating article is a heated aerosol generating article. In other words, the aerosol-generating article preferably contains at least one aerosol-generating substrate that is intended to be heated, rather than combusted, to release volatile compounds that can form an aerosol. The aerosol generating article may be a consumable part, in particular a consumable part to be disposed of after a single use. The aerosol generating product may be a tobacco product. For example, the article may be a cartridge containing a liquid or solid aerosol-forming substrate to be heated. Alternatively, the product may be a rod-shaped product, in particular a tobacco product similar to conventional cigarettes and containing a solid aerosol-forming substrate.

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

In addition to the aerosol-forming substrate and the current collector assembly, the article may further comprise various elements.

In particular, the article may comprise a mouthpiece. In the context of this document, the term "mouthpiece" refers to the part of the device that is placed in the user's mouth to directly inhale the aerosol from the product. Preferably, the mouthpiece contains a filter.

In addition, the article may include a casing, in particular a tubular wrapper, surrounding at least a portion of the aerosol-forming substrate. The wrapper may include a current collector. This provides the advantage of being able to uniformly and symmetrically heat the aerosol-forming substrate surrounded by the current collector assembly.

In particular, with regard to an aerosol-generating article having a rod-like shape resembling conventional cigarettes and/or containing a solid aerosol-forming substrate, the article may further comprise: a support element having a central air path, an element for cooling the aerosol and a filter element. The filter element preferably functions as a mouthpiece. In particular, the article may comprise a substrate element which comprises an aerosol-forming substrate and a current-collecting assembly in contact with the aerosol-forming substrate. Any of these elements, or any combination thereof, may be arranged in series with the aerosol-forming rod segment. Preferably, the substrate element is located at the distal end of the article. Likewise, the filter element is preferably located at the proximal end of the article. In addition, these elements may have the same outer cross-section as the aerosol-generating rod segment.

In addition, the article may include a casing or wrapper surrounding at least a portion of the aerosol-forming substrate. In particular, the product may include a wrapper surrounding at least a portion of the various segments and elements mentioned above in such a way as to hold them together and maintain the desired cross-sectional shape of the product.

The casing or wrapper may include at least the first current collector or both of the first and second current collectors of the current collector assembly. This provides the advantage of being able to uniformly and symmetrically heat the aerosol-forming substrate surrounded by the first current collector or current collector assembly.

Preferably, the casing or wrapper forms at least a portion of the outer surface of the article. The casing may form a cartridge containing a reservoir that contains an aerosol-forming substrate, such as a liquid aerosol-forming substrate. The wrapper may be a paper wrapper, in particular a paper wrapper made from cigarette paper. Alternatively, the wrapper may be a foil, for example made from plastic. The wrapper may be fluid-permeable to allow the vaporized aerosol-forming substrate to escape from the article, or to allow air to be drawn into the article through its circumferential surface. In addition, the wrapper may contain at least one volatile substance to be activated and released from the wrapper when heated. For example, the wrapper may be impregnated with an aromatic volatile substance.

Additional features and advantages of the aerosol generating system according to the present invention have been described in relation to the aerosol generating device and the heating unit and will not be described again.

The present invention will be further described solely by way of examples with reference to the accompanying drawings, in which:

in FIG. 1 is a schematic representation of an aerosol generating system comprising an inductively heated aerosol generating device and an aerosol generating article, the system comprising a heating assembly according to a first exemplary embodiment of the present invention;

in FIG. 2 is a schematic representation of the inductively heated aerosol generating article of FIG. 1;

in FIG. 3 is a perspective view of the current-collecting assembly of the aerosol-generating article of FIG. 1 and FIG. 2;

in FIG. 4 is a graph schematically illustrating the resistance versus temperature profile of a current collector assembly according to the present invention;

in FIG. 5-7 show alternative embodiments of a current collector assembly for use with the product of FIG. 1 and FIG. 2;

in FIG. 8-10 show aerosol generating articles for use with the apparatus of FIG. 1, which include additional alternative embodiments of current collector assemblies;

in FIG. 11 is a schematic view of another aerosol generating system comprising a heating unit according to a second exemplary embodiment of the present invention;

in FIG. 12 is a perspective view of the current collector included in the aerosol generating device of FIG. eleven;

in FIG. 13-15 show alternative embodiments of a current collector assembly for use with the apparatus of FIG. eleven;

in FIG. 16 is a schematic view of an aerosol generating system comprising a heating unit according to a third exemplary embodiment of the present invention;

in FIG. 17 is a schematic diagram of an aerosol generating system comprising a heating unit according to a fourth illustrative embodiment of the present invention;

in FIG. 18 is a schematic diagram of an aerosol generating system comprising a heating unit according to a fifth exemplary embodiment of the present invention; And

in FIG. 19 is a schematic representation of an aerosol generating system comprising a heating unit according to a sixth exemplary embodiment of the present invention.

On FIG. 1 schematically shows a first exemplary embodiment of an aerosol generating system 1 according to the present invention. System 1 comprises an aerosol generating device 10 according to the present invention, as well as an aerosol generating article 100 which is configured for use with the device and contains an aerosol generating substrate to be heated.

On FIG. 2 shows additional details of an aerosol-generating article 100, wherein the aerosol-generating article 100 is substantially rod-shaped and comprises four elements arranged in series with coaxial alignment: an aerosol-generating rod segment 110, containing a current-collecting element 120 and an aerosol-generating substrate 130, a supporting element 140 containing a central air path 141, an aerosol cooling element 150, and a filter element 160 that serves as a mouthpiece. The aerosol generating rod segment 110 is located at the distal end 102 of the article 100, while the filter element 160 is located at the proximal end 103 of the article 100. Each of these four elements is a substantially cylindrical element, and they all have essentially the same diameter. In addition, these four elements are surrounded by an outer wrap 170 in order to hold the four elements together and maintain the desired circular cross-sectional shape of the rod 100. The wrap 170 is preferably made of paper. Additional details of the product, in particular these four elements, with the exception of the features of the current collector 120 inside the rod segment 110, are disclosed in WO 2015/176898 A1.

As shown in FIG. 1, the aerosol generating device 10 comprises a cylindrical receiving cavity 20 formed within the proximal portion 12 of the device 10 to accommodate at least the distal portion of the article 100. The device 10 further comprises an induction source comprising an inductor 30 for generating an alternating, in particular high frequency , electromagnetic field. In this embodiment, the inductor 30 is a helical coil surrounding the cylindrical receiving cavity 20 in a circumferential manner. The coil 30 is positioned such that the current collector assembly 120 of the aerosol generating article 100 is exposed to an electromagnetic field when the article 100 interacts with the device 10. Thus, when the inductive source is activated, the current collector assembly 120 is heated by the eddy currents and/or hysteresis losses that are induced alternating electromagnetic field, depending on the magnetic and electrical properties of the current-collecting materials of the current-collector assembly 120. The current-collector assembly 120 is heated until it reaches an operating temperature sufficient to vaporize the aerosol-forming substrate 130 surrounding the current-collector assembly 120 within the product 100.

Within the distal portion 13, the aerosol generating device 10 further comprises a DC power supply 40 and a controller 50 (shown only schematically in FIG. 1) for powering and controlling the heating process. In an electronic aspect, the induction source, with the exception of the inductor 30, is preferably at least partially integral to the controller 50.

Both the induction source as part of the apparatus 10 and the current collector assembly 120 as part of the aerosol generating article 100 constitute essential parts of the induction heating assembly 5 according to the present invention.

On FIG. 3 is a detailed view of the current collector assembly 120 used within the aerosol generating article shown in FIG. 1 and FIG. 2. According to the present invention, the current collector assembly 120 includes a first current collector 121 and a second current collector 122. The first current collector 121 includes a first current collector material having a positive temperature coefficient of resistance, while the second current collector 122 includes a second current collector material that is a ferromagnetic or ferrimagnetic material. pantograph having a negative temperature coefficient of resistance. Due to the fact that the materials of the first and second pantographs have opposite temperature coefficients of resistance, and due to the magnetic properties of the material of the second pantograph, the pantograph assembly 120 has a resistance versus temperature profile that includes a minimum resistance value in the vicinity of the Curie temperature of the second pantograph material.

The corresponding resistance versus temperature profile is shown in FIG. 4 . From the start of heating the current collector 120 from room temperature T_R, the resistance of the material of the first current collector increases, while the resistance of the material of the second current collector decreases with increasing temperature T. heating current collector node 120, is determined by the combination of the respective resistances of the materials of the first and second current collectors. When the temperature T_C Curie is reached by the material of the second pantograph from below, the decrease in the resistance of the material of the second pantograph usually prevails over the increase in the resistance of the material of the first pantograph. Accordingly, the total apparent resistance R_a of the current collector assembly 120 decreases in a temperature range below, in particular approximately below, the Curie temperature T_C of the material of the second current collector. At the temperature T_C Curie, the material of the second current collector loses its magnetic properties. This leads to an increase in the surface layer available for eddy currents in the second current-collecting material, which is accompanied by a sharp drop in its resistance. Thus, as the temperature T of the current collector 120 increases further beyond the Curie temperature T_C of the second current collector material, the contribution of the resistance of the second current collector material to the total apparent resistance R_a of the current collector assembly 120 becomes smaller or even negligible. Therefore, after passing through the minimum value R_min in the vicinity of the Curie temperature T_C of the material of the second current collector, the total apparent resistance R_a of the current collector assembly 120 is mainly determined by the increase in the resistance of the material of the first current collector. In other words, the total apparent resistance R_a of the current collector 120 increases again in the direction of the operating resistance R_op at the operating temperature T_op. The decrease and subsequent increase in the resistance versus temperature profile near the minimum value R_min in the vicinity of the Curie temperature T_C of the second current collector material provides the advantage that it is sufficiently distinct from the temporal change in the total apparent resistance during user puffing. As a result, it is possible to reliably use the minimum resistance value R_a in the vicinity of the Curie temperature T_C of the material of the second current collector as a temperature marker for controlling the heating temperature of the aerosol-forming substrate without the risk of its erroneous interpretation as a consequence of the user puffing. Accordingly, it is possible to effectively prevent unwanted overheating of the aerosol-forming substrate.

In order to adjust the heating temperature of the aerosol-forming substrate to match the desired operating temperature T_op, the controller 50 of the device 10 shown in FIG. 1 is configured to control the operation of the induction source in a feedback and biased configuration such that the actual apparent resistivity is maintained at a value that corresponds to the sum of the determined minimum apparent resistivity value R_min R_a and the predetermined bias value ΔR_offset. The offset value ΔR_offset bridges the gap between the apparent resistance R_min measured at the marker temperature T_C and the operating resistance R_op at the operating temperature T_op. This provides the advantage of avoiding direct control of the heating temperature based on a predetermined target apparent resistivity at operating temperature T_op. In addition, heating temperature offset control is more stable and reliable than temperature control based on measured absolute values of apparent resistivity at the desired operating temperature.

If the actual apparent resistance is equal to or higher than the sum of the predetermined minimum apparent resistivity value and the predetermined apparent resistivity offset value, then the heating process can be stopped by interrupting the generation of the alternating electromagnetic field, i.e. by turning off the induction source, or at least by reducing the output power of the induction source. If the actual apparent resistivity is below the sum of the predetermined minimum apparent resistivity value and the predetermined apparent resistivity offset value, then the heating process can be resumed by resuming the generation of an alternating electromagnetic field, that is, by turning on the induction source again or by increasing the output power of the induction source again.

In this embodiment, the operating temperature is approximately 370 degrees Celsius. This temperature is the normal operating temperature for heating, but not burning, the aerosol-forming substrate. To provide a sufficiently large temperature gap of at least 20 degrees Celsius between the marker temperature at the temperature T_C Curie of the material of the second current collector and the operating temperature T_op, the material of the second current collector is chosen so that it has a Curie temperature below 350 degrees Celsius.

As shown in FIG. 3, the current collector 120 within the product shown in FIG. 2 is a multi-layer current collector assembly, more specifically a two-layer current collector assembly. It comprises a first layer forming a first current collector 121 and a second layer forming a second current collector 122 which is located on and directly attached to the first layer. While the first pantograph 121 is optimized for heat loss and thus heating efficiency, the second pantograph 122 is basically a functional pantograph used as a temperature marker as described above. The current collector assembly 120 is made in the form of an oblong strip having a length L equal to 12 millimeters and a width W equal to 4 millimeters, that is, both layers have a length L equal to 12 millimeters and a width W equal to 4 millimeters. The first current collector 121 is a strip made of stainless steel having a Curie temperature above 400°C, such as 430 stainless steel. It has a thickness of approximately 35 micrometers. The second current collector 122 is a strip of mu-metal or permalloy having a Curie temperature below the operating temperature. It is approximately 10 micrometers thick. The current collector assembly 120 is made by applying a strip of the second current collector to the strip of the first current collector by the cladding method.

On FIG. 5 shows an alternative embodiment of the strip-shaped current collector assembly 220, which is similar to the embodiment of the current collector assembly 120 shown in FIG. 1 and 2. Unlike the latter, the current collector 220 according to FIG. 5 is a three-layer current collector assembly which, in addition to the first and second current collectors 221, 222 forming the first and second layers, respectively, includes a third current collector 223 which forms the third layer. All three layers are stacked on top of each other, with adjacent layers closely connected to each other. The first and second pantographs 221, 222 of the three-layer pantograph assembly shown in FIG. 5 are identical to the first and second current collectors 121, 122 of the two-layer current collector assembly 120 shown in FIG. 1 and 2. The third pantograph 223 is identical to the first pantograph 221. In other words, the third layer 223 contains the same material as the first pantograph 221. In addition, the thickness of the layer of the third pantograph 223 is equal to the thickness of the layer of the first pantograph 221. Accordingly, the thermal expansion characteristics of the first and third pantographs 221, 223 are essentially the same. This provides the advantage of creating a layered structure with a high degree of symmetry, essentially showing no out-of-plane deformations. In addition, the three-layer current-collecting assembly according to FIG. 5 provides higher mechanical stability.

On FIG. 6 shows another embodiment of the strip-shaped current collector assembly 320, which may alternatively be used in the product shown in FIG. 2 instead of the two-layer current collector 120. The current collector assembly 320 of FIG. 6 is formed from a first pantograph 321 which is directly connected to a second pantograph 322. The first pantograph 321 is a 430 stainless steel strip measuring 12 millimeters by 4 millimeters by 35 micrometers. Thus, the first current collector 321 defines the basic shape of the current collector assembly 320. The second current collector 322 is a mu-metal or permalloy patch measuring 3 millimeters by 2 millimeters by 10 micrometers. The second pantograph 322 in the form of an overlay is applied to the first pantograph 321 in the form of a strip by galvanization. Although the second pantograph 322 is significantly smaller than the first pantograph 321, it is still sufficient to enable precise control of the heating temperature. The current collector 320 of FIG. 6 provides the advantage of significant savings in the material of the second pantograph. In additional embodiments (not shown), more than one pad may be present in intimate contact with the first current collector.

On FIG. 7 shows another embodiment of a current collector assembly 1020 for use with the product shown in FIG. 1 and FIG. 2. According to this embodiment, the current collector assembly 1020 forms a current collector bar. The collector rod is cylindrical and has a round cross section. Preferably, the current-collecting rod is positioned centrally within the aerosol-forming substrate such that it extends along the longitudinal axis of the article shown in FIG. 2. As can be seen on one of its end faces, the current collector assembly 1020 includes an internal core current collector that forms the second current collector 1022 according to the present invention. The core current collector is surrounded by a sheath current collector, which forms the first current collector 1021 according to the present invention. Since the first pantograph 1021 preferably has a heating function, this configuration provides an advantage in terms of direct heat transfer to the surrounding aerosol-forming substrate. In addition, the cylindrical shape of the current-collecting pin provides a heating profile with a very high degree of symmetry, which can be advantageous for a rod-shaped aerosol generating article.

On FIG. 8-10 schematically depict various aerosol generating articles 400, 500, 600 containing additional embodiments of a current collector assembly that is part of a heating assembly according to the present invention. Articles 400, 500, 600 are very similar to article 100 shown in FIG. 1 and 2, in particular with regard to the overall layout of the product. Therefore, similar or identical features are designated by the same reference numerals as in FIG. 1 and 2, but with an increase of 300, 400 and 500, respectively.

Unlike product 100 shown in FIG. 1 and 2, the aerosol generating article 400 of FIG. 8 includes a thread-like current collector assembly 420. In other words, the first and second current collectors 421, 422 are threads that are twisted with each other such that they form a twisted pair of threads. Said pair of threads is located centrally within the aerosol-forming substrate 430 and is in direct contact with the substrate 430. Said pair of threads essentially extends along the length of the article 400. The first current collector 421 is a thread made of ferromagnetic stainless steel, and thus performs mainly heating function. The second current collector 422 is a mu-metal or permalloy filament and thus serves primarily as a temperature marker.

The aerosol generating article 500 of FIG. 9 includes a particulate current collector assembly 520. Both of the first current collector 521 and the second current collector 522 comprise a plurality of current collector particles distributed within the aerosol-forming substrate 530 of the article 500. Thus, the current-collector particles are in direct physical contact with the aerosol-forming substrate 530. The current-collector particles of the first current collector 521 are made of ferromagnetic stainless steel and thus serving primarily to heat the surrounding aerosol-forming substrate 530. In contrast, the current-collecting particles of the second current collector 422 are made of mu-metal or permalloy and thus serve primarily as a temperature marker.

The aerosol generating article 600 of FIG. 10 includes a current collector assembly 600 comprising a first current collector 621 and a second current collector 622 that have different geometries. The first current collector 621 is a particulate current collector containing a plurality of current-collecting particles dispersed in the aerosol-forming substrate 630. Due to its particulate structure, the first current collector 621 provides a large surface area for the surrounding aerosol-forming substrate 630, which provides the advantage of improving heat transfer. Accordingly, the particulate configuration of the first pantograph 621 is specifically selected in consideration of the heating function. In contrast, the second pantograph 622 has primarily a temperature control function and therefore need not have a very large surface area. Accordingly, the second current collector 622 according to the present invention is a current-collecting strip extending within the aerosol-generating substrate 630 through the center of the aerosol-generating article 600.

On FIG. 11 schematically depicts a second exemplary embodiment of an aerosol generating system 2001 according to the present invention. System 2001 is very similar to system 1 shown in FIG. 1, with the exception of the current collector. In this regard, similar or identical features are designated by the same reference numerals as in FIG. 1 and 2, but magnified by 2000. Unlike the embodiment shown in FIG. 1, the current collector 2060 of the heating unit 2005 according to the embodiment of FIG. 11 is part of the aerosol generating device 2010.

Accordingly, the aerosol generating article 2100 does not include any current collector assembly. Therefore, product 2100 basically corresponds to product 100 shown in FIG. 1 and 2, but without the current collector.

Similarly, the aerosol generating device 2010 of FIG. 11 basically corresponds to the device 10 shown in FIG. 1. Unlike the latter, the device 2010 contains all parts of the heating unit 2005 according to the present invention. In other words, the device 2010 includes an induction source containing a helical inductor 2030 that surrounds the cylindrical receiving cavity 2020 in a circle. In addition, the device also includes a current-collecting assembly 2060 that is positioned within the receiving cavity so as to be exposed to the electromagnetic field generated by the inductor 2030.

The susceptor assembly 2060 is a susceptor blade. With its distal end 2064, the current-collecting blade 2060 is located at the bottom of the receiving cavity 2020 of the device 2010. From there, the current-collecting blade extends into the interior of the receiving cavity 2020 towards the opening of the receiving cavity 2020. The receiving cavity opening 2020 is located at the proximal end 2014 of the aerosol generating device 2010, thus providing thus, the possibility of inserting the aerosol generating article 2100 into the receiving cavity 2020.

As can be seen in particular in FIG. 12 , the current collector assembly 2060 of the device 2010 of FIG. 11 is a two-layer current-collecting blade very similar to the two-layer current-collecting assembly 120 shown in FIG. 1-3. In contrast to the latter, the distal free end 2063 of the current collector assembly 2060 is tapered in such a way that the blade-shaped current collector assembly can easily penetrate the aerosol-forming substrate 2130 within the distal end of the aerosol-generating article 2100.

In addition, the current receiving unit 2060 and the heating unit 2005 of the aerosol generating system 2001 of FIG. 11 show the same resistance versus temperature profile as the aerosol generating system of FIG. 1, that is, the profile shown in FIG. 4.

On FIG. 13 , Fig. 14 and FIG. 15 shows further embodiments of current collector assemblies 2160, 2260, 2360 according to the present invention, which may alternatively be used with the apparatus of FIG. 11. Current collector nodes 2160, 2260, and 360 generally correspond to current collector nodes 220, 320, and 1020 shown in FIG. 5, Fig. 6 and FIG. 7 respectively. Therefore, most of the features and benefits of these current collector nodes 2160, 2260, 2360 have been described in relation to the current collector nodes 220, 320, 1020 and therefore will not be described again. Similar to the current collector node 120, the respective distal free end 2163, 2263, 2361 of the current collector nodes 2160, 2260, 2360 tapers to facilitate penetration into the aerosol-forming substrate.

On FIG. 16-18 schematically depict additional embodiments of aerosol generating systems 2701, 2801, 2901 according to the present invention, in which the respective induction heating assembly 2705, 2805, 2905 is exclusively part of the respective aerosol generating device 2710, 2810, 2910. Systems 2701, 2801 and 2901 are very similar to system 2001 shown in FIG. 11, in particular with respect to the general layout of devices 2710, 2810, 2910 and products 2700, 2800, 2900. In this regard, similar or identical features of devices are indicated by the same reference numbers as in FIG. 11, magnified by 700, 800 and 900, respectively.

Unlike the device 2010 shown in FIG. 11, the aerosol generating device 2710 of the aerosol generating system 2701 of FIG. 16 includes a current collector assembly 2760 in which the first current collector 2761 and the second current collector 2762 have different geometries. The first current collector 2761 is a single layer current collector blade similar to the double layer current collector assembly 2060 shown in FIG. 11 and FIG. 12, but without the second current-collecting layer. In this configuration, the first pantograph 1761 generally forms an induction heating blade, since it mainly has a heating function. In contrast, the second current collector 2762 is a current collector sleeve that forms at least part of the circumferential inner side wall of the receiving cavity 2720. the inner side wall of the cylindrical receiving cavity 2720, while the second current collector may be a single-layer current-collecting blade to be inserted into the aerosol-forming substrate. In the latter configuration, the first current collector may form a heater or heating chamber in the form of an induction furnace. In either of these configurations, the first and second current collectors 2761, 2762 are located at different locations within the aerosol generating device 2710 at a distance from each other, but still in thermal proximity to each other.

Aerosol generating device 2810 of the aerosol generating system 2801 shown in FIG. 17 includes a susceptor assembly 2860, which is a susceptor bowl, thus forming a heater or heating chamber in the form of an induction furnace. In this configuration, the first current collector 2861 is a current collector sleeve forming the circumferential side wall of the cup current collector assembly 2860 and thus at least a portion of the inner side wall of the cylindrical current collector cavity 2820. In contrast, the second current collector 2862 forms the bottom of the cup current collector assembly 2860. Both of the first and second current collectors 2861, 2862 are in thermal proximity to the aerosol-generating substrate 2130 of the aerosol-generating article 2100 when placed in the receiving cavity 2820 of the device 2810.

Aerosol generating device 2910 of the aerosol generating system 2901 shown in FIG. 18 includes a current collector assembly 2960, which is a multilayer current collector sleeve. In this configuration, the second current collector 2962 forms the outer wall of the multilayer current collector sleeve, while the first current collector 2961 forms the inner wall of the multilayer current collector sleeve. This particular arrangement of the first and second current collectors 2961, 2962 is advantageous because it places the first current collector 2961, used primarily to heat the aerosol-forming substrate 2130, closer to the substrate 2130. Preferably, the current collector assembly 2960 also forms a heater or heating chamber in the form of an induction ovens.

On FIG. 19 schematically depicts another embodiment of an aerosol generating system 3701 according to the present invention. System 3701 is very similar to system 2701 shown in FIG. 16. In view of this, similar or identical features are designated by the same reference numerals as in FIG. 16, but magnified by 1000. Unlike the embodiment shown in FIG. 16, the current collector 3760 of the heater 3705 according to the embodiment of FIG. 16 is divided. While the first current collector 3761 of the current collector assembly 3760 is part of the aerosol generating article 3100, the second current collector 3762 of the current collector assembly 3760 is part of the aerosol generating device 3710. The first current collector 3761 is a single layer current collector strip similar to the two layer current collector assembly 120 shown in Fig. 1-3, but located within the aerosol-forming substrate 3130 of article 3100 and not having a second current-collecting layer. Thus, the first current collector 1761 generally forms an induction heating element as an integral part of the product 3100. The second current collector 2762 is a current collector sleeve that forms at least a portion of the circumferential inner side wall of the receiving cavity 2720, forming a heater or heating chamber in the form of an induction furnace. Although the second pantograph 3762 is located at a distance from the first pantograph 3761, it is still in thermal proximity to the first pantograph 3761 and the aerosol forming substrate 3130, and thus can be easily used as a temperature marker.

For all three embodiments shown in FIG. 16-19, the first current collector is preferably made of a ferromagnetic stainless steel that is optimized for heating the aerosol-forming substrate. In contrast, the second current collector is preferably made of mu-metal or permalloy, which is a suitable temperature marker material.

Claims (15)

1. An induction heating unit configured to inductively heat an aerosol-forming substrate to a predetermined operating temperature, the heating unit comprising an induction source configured to generate an alternating electromagnetic field and a susceptor unit for inductively heating an aerosol-forming substrate under the action of an alternating magnetic field generated an induction source, wherein the susceptor assembly comprises a first susceptor containing a first susceptor material and a second susceptor containing a second susceptor material having a Curie temperature of at least 50 degrees Celsius below the operating temperature of the heating assembly. 2. The heating unit according to claim. 1, in which the specified 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 Celsius. 3. A heating assembly according to any one of the preceding claims, wherein the second susceptor material has a Curie temperature of at least 100 degrees Celsius, preferably at least 150 degrees Celsius, most preferably at least 200 degrees Celsius below operating temperature . 4. A heating unit according to any one of the preceding claims, wherein the second susceptor material has a Curie temperature below 350 degrees Celsius, in particular below 300 degrees Celsius, preferably below 250 degrees Celsius, most preferably below 200 degrees Celsius. 5. A heating assembly according to any one of the preceding claims, wherein the second susceptor comprises one of mu-metal or permalloy. 6. A heating unit according to any one of the preceding claims, wherein the material of the first susceptor is electrically conductive and/or one of paramagnetic, ferromagnetic or ferrimagnetic. 7. A heating assembly according to any one of the preceding claims, wherein the material of the first susceptor comprises one of the following: aluminum, iron, nickel, copper, bronze, cobalt, carbon steel, stainless steel, ferritic stainless steel, martensitic stainless steel, or austenitic stainless steel. 8. A heating assembly according to any one of the preceding claims, wherein the first susceptor material has a positive temperature coefficient of resistance and the second susceptor material has a negative temperature coefficient of resistance. 9. A heating assembly according to any one of the preceding claims, wherein the first susceptor and the second susceptor are in close physical contact with each other. 10. A 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 the following: a particulate susceptor, or a susceptor thread, or a susceptor mesh, or a susceptor wick, 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. A heating assembly according to any one of the preceding claims, further comprising a controller operatively coupled to the induction source and configured to control the operation of the induction source, particularly in a closed loop configuration, to control the heating of the aerosol-forming substrate to a predetermined operating temperature. 12. The heating assembly according to claim 11, wherein the controller is configured to determine, during preheating of the susceptor assembly from room temperature to operating temperature, the minimum value of apparent impedance achievable in a temperature range of ±5 degrees Celsius relative to the Curie temperature of the material of the second susceptor. 13. A heating unit according to any one of the preceding claims, further comprising a DC power supply configured to supply a DC supply voltage and a DC supply to the induction source. 14. A device for generating an aerosol by heating an aerosol-forming substrate, comprising a receiving cavity for accommodating an 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. 15. An aerosol generating system comprising an aerosol generating device, an aerosol generating article for use with an aerosol generating device, and an induction heating assembly according to any one of paragraphs. 1-13, wherein the induction source of the heating assembly is part of an aerosol generating device, wherein the first susceptor of the susceptor assembly is part of an aerosol generating article and the second susceptor of the susceptor assembly is a part of an aerosol generating article or a part of an aerosol generating device.

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