RU2793697C2 - Heating assembly and method of induction heating of aerosol substrate - Google Patents

Abstract

FIELD: induction heating unit.
SUBSTANCE: heating unit contains an induction source connected to a DC power supply, which is configured to generate an alternating electromagnetic field for inductive heating of the current-collecting unit. The current collector assembly comprises the first current collector containing the first current collector material and the second current collector containing the second current collector material having a Curie temperature below the operating temperature. In addition, the heating unit contains a controller functionally connected to the induction source and DC power supply. The controller is configured to determine the actual apparent resistance of the current collector, which indicates the actual temperature of the current collector, to determine the minimum value of the apparent resistance that occurs when the current collector is preheated, and to regulate the operation of the induction source so that the actual apparent resistance corresponds to a certain minimum value of the apparent resistance plus a predetermined apparent resistivity offset value to control the heating of the aerosol generating substrate to operating temperature. The invention is an induction heating unit for inductively heating an aerosol-forming substrate to an operating temperature. The present invention further relates to an aerosol generating apparatus, an aerosol generating system, and a method for induction heating of an aerosol generating substrate using such a heating unit.

EFFECT: improve the operation of the device.

14 cl, 19 dwg

Description

The present invention relates to an induction heating unit and a method for induction heating of an aerosol generating 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 generating substrate that can form an inhalable aerosol when heated are well known in the art. To heat the aerosol-forming substrate, such systems may include an induction heating assembly comprising an induction source and a current collector (susceptor). The induction source is configured to generate an alternating electromagnetic field that induces at least one of heat generating eddy currents or hysteresis losses in the current collector (susceptor). Although the induction source is usually part of an aerosol generating device, the current collector (susceptor) may be either part of the device or an integral part of an aerosol generating product that is configured to be placed in an aerosol generating device, including an induction source. In either case, the current collector is positioned to be in thermal proximity to, or in direct physical contact with, the substrate during operation of the system.

To control the temperature of the substrate, current-collecting (susceptor) nodes are proposed, containing the first and second current collectors (susceptors) made of various materials. The first susceptor material is optimized with respect to heat loss and thus heating efficiency. In contrast, the second current-collecting (susceptor) material is used as a temperature marker. To do this, the second current-collecting material is chosen so that it has a Curie temperature corresponding to the specified operating temperature of the current-collecting (susceptor) node. The magnetic properties of the second current collector (susceptor) at its Curie temperature change from ferromagnetic or ferrimagnetic to paramagnetic, which is accompanied by a temporary change in its electrical resistance. Thus, by observing a corresponding change in the electrical current drawn by the induction source, it can be determined when the second current-collecting (susceptor) material has reached its Curie temperature and thus when the desired operating temperature has been reached.

However, when observing the change in electric current drawn by the induction source, it may be difficult to distinguish between the situation where the second current-collecting (susceptor) material 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 a similar change. characteristics. The change in electric current during a user's puff is due to the cooling of the current collector assembly caused by air being drawn through the aerosol generating product as the user takes a puff. Cooling causes a temporary change in the electrical resistance of the current collector. This, in turn, causes a corresponding change in the electrical current drawn by the induction source. Typically, the controller counteracts the cooling of the current collector during the user's puff by temporarily increasing the heating power. However, this controller-induced temporary increase in heating power can have the adverse effect of causing unwanted overheating of the susceptor assembly in the event that the monitored change in electric current, which is actually due to the second susceptor material reaching its Curie temperature, is erroneous. identified as user puff.

Therefore, it would be desirable to have an induction heating unit and a method for inductively heating an aerosol forming substrate with the advantages of the prior art, but without their limitations. In particular, it would be desirable to have an induction heating unit and a method for inductively heating an aerosol-forming substrate, which would improve temperature control.

According to the present invention, an induction heating unit is provided for heating an aerosol-forming substrate to an operating temperature. The heating unit comprises a DC power supply configured to supply a DC power supply voltage and a DC power supply current. The heating unit further comprises an induction source connected to a DC power supply unit and configured to generate an alternating electromagnetic field. The heating unit also contains a current-collecting unit for inductively heating the aerosol-forming substrate under the influence of an alternating magnetic field generated by the induction source. The current collector assembly contains the first current collector containing the first current collector material. The current collector also includes a second current collector containing a second current collector material having a Curie temperature below the operating temperature. In addition, the heating unit contains a controller functionally connected to the induction source and DC power supply. The controller is configured to determine, from the DC supply voltage and the DC supply current consumed from the DC power supply, the actual apparent resistance of the current collector, which indicates the actual temperature of the current collector. The controller is additionally configured to determine the minimum value of the apparent resistance that occurs during the preheating of the current collector assembly, from room temperature to operating temperature. In addition, the controller is configured to regulate (control) the operation of the induction source in a feedback configuration so that the actual apparent resistance corresponds to (the sum of) a certain minimum apparent resistance value plus a predetermined (set) apparent resistance offset value, to regulate the heating of the substrate, aerosol-forming to operating temperature.

According to the present invention, it has been recognized that the minimum value of apparent resistance that occurs during preheating of the current collector assembly, starting from room temperature, can be reliably used as a temperature marker to control the heating temperature of the aerosol generating substrate without the risk of being mistaken for a puff by the user. . This is due to the fact that the resistance passes a minimum value during the preheating of the current collector and therefore is in the temperature range below the operating temperature. As a result, there is a sufficiently large temperature range between the marker temperature and the operating temperature at which a temporary change in resistance usually occurs during the user's puff. Accordingly, unwanted overheating of the aerosol-generating substrate can be effectively prevented.

According to the present invention, heating temperature control is based on the principles of bias blocking or bias control using a predetermined apparent resistivity bias value. The offset value spans the interval between the measured apparent resistivity at marker temperature and the apparent resistivity at operating temperature. Advantageously, this avoids direct control of the heating temperature based on a predetermined target value of apparent resistance at operating temperature and hence avoids misinterpretation of the measured resistance parameter.

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 due to the fact that the measured absolute value of the apparent resistance, determined from the supply voltage and supply current, depends on various factors, such as, for example, 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 adjusting the heating temperature of the aerosol-forming substrate to the operating temperature may be predetermined by means of a calibration measurement, for example, during manufacture of the device.

Preferably, the minimum value close to the Curie temperature of the second current collector material is the global minimum of the resistance versus temperature profile.

In the context of this document, the term "starting at room temperature" preferably means that a minimum value close to the Curie temperature of the second current collector material occurs in the resistance versus temperature profile during preheating, i.e. heating of the current collector assembly from room temperature to operating temperature, to which the aerosol-forming substrate must be heated.

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

The minimum apparent resistance value that occurs when the current collector assembly is preheated is preferably in the temperature range of ±5 degrees Celsius around the Curie temperature of the second current collector material. According to the present invention, the Curie temperature of the second current collector material is below the operating temperature. That is, the first and second susceptor materials are preferably chosen such that during preheating of the susceptor assembly, starting at room temperature, the resistance versus temperature profile of the susceptor assembly has a minimum apparent resistance value in the temperature range of ±5 degrees Celsius around the Curie temperature of the second susceptor material. .

Preferably, the second current collector material is chosen to have 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 generating substrate within the aerosol generating article. Thus, the correct identification of the temperature marker at the minimum of the resistance temperature profile close to the Curie temperature of the second current-collecting material is further improved due to a sufficiently large temperature interval to the operating temperature at which the change in apparent total resistance usually occurs when the user tightens.

Operating temperatures used to heat the aerosol generating substrate within the aerosol generating article 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 combusting, an aerosol-forming substrate.

Similarly, the second current-collecting material has a Curie temperature of at least 20 degrees Celsius, in particular at least 50 degrees Celsius, more specifically at least 100 degrees Celsius, preferably at least 150 degrees Celsius, most preferably at least 200 degrees Celsius. below operating temperature.

In the context of this document, the term "current collector" means an element that can convert 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 current collector, depending on the electrical and magnetic properties of the current collector material. Hysteresis losses occur in ferromagnetic or ferrimagnetic current collectors due to the remagnetization of magnetic domains inside the material under the influence of an alternating electromagnetic field. Eddy currents can be induced if the current collector is electrically conductive. In the case of an electrically conductive ferromagnetic or ferrimagnetic current collector, heat can be generated by both eddy currents and hysteresis losses.

According to the present invention, the second current collector material is at least ferrimagnetic or ferromagnetic 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 second current collector material may also be electrically conductive.

Preferably, the second current collector material may comprise one of mu-metal or permalloy.

While the second current collector is generally adapted to monitor the temperature of the current collector assembly, the first current collector is preferably 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. Accordingly, the first current-collecting material may be electrically conductive and/or one of paramagnetic, ferromagnetic, or ferrimagnetic materials. In case the first current collector material is ferromagnetic or ferrimagnetic, the corresponding Curie temperature of the first current collector material is preferably different from the Curie temperature of the second current collector, in particular higher than any typical operating temperature mentioned above used to heat the aerosol forming substrate. For example, the first current collector material 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 first current collector material may comprise one of aluminium, iron, nickel, copper, bronze, cobalt, unalloyed carbon steel, stainless steel, ferritic stainless steel, martensitic stainless steel, or austenitic stainless steel.

Preferably the first current collector material has a positive temperature coefficient of resistance, while the second current collector material preferably has a negative temperature coefficient of resistance. According to the present invention, it has been recognized that a current collector assembly comprising two current collector materials having opposite temperature coefficients of resistance has a resistance versus temperature profile that includes a minimum resistance value around the Curie temperature of the second current collector material, for example ±5 degrees Celsius around the Curie temperature of the second current collector material. material. Preferably, this minimum value is the global minimum of the resistance versus temperature profile. This minimum is due to the opposite temperature behavior of the respective electrical resistance of the first and second current collector materials and the magnetic properties of the second current collector material. When the current-collecting assembly starts heating from room temperature, the resistance of the first current-collecting material increases, while the resistance of the second current-collecting material decreases with increasing temperature. The total apparent resistance of the susceptor assembly "seen" by the inductive source used to inductively heat the susceptor assembly is determined by the combination of the respective resistances of the first and second susceptor materials. When the Curie temperature of the second current-collecting material is reached from below, the decrease in the resistance of the second current-collecting material usually prevails over the increase in the resistance of the first current-collecting material. Accordingly, the overall apparent resistance of the current collector assembly decreases in the temperature range below, in particular approximately below, the Curie temperature of the second current collector material. At the Curie temperature, the second current-collecting material loses its magnetic properties. This causes an increase in the surface layer available for eddy currents in the second current collector material, which is accompanied by a sudden drop in its resistance. Thus, with a further increase in the temperature of the current collector above the Curie temperature of the second current collector material, the contribution of the resistance of the second current collector material to the total apparent resistance of the current collector node becomes smaller or even negligible. Therefore, after passing a minimum value near the Curie temperature of the second current collector material, the total apparent resistance of the current collector assembly is mainly determined by the increase in the resistance of the first current collector material. That is, the total apparent resistance of the current collector increases again. As a result, the current collector assembly has a resistance versus temperature profile that includes a desired minimum resistance value around the Curie temperature of the second current collector material.

Preferably, the first current collector and the second current collector are in direct 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 pantographs have substantially the same temperature. Due to this, the temperature control of the first pantograph by means of the second pantograph is extremely precise. Direct 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 electroplated, deposited, coated, applied by cladding, or welded to the first current collector. 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 actuated 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 the 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 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 plate, or a current-collector strip , or a current-collecting sleeve, or a pantograph in the form of a bowl, or a cylindrical pantograph, or a flat pantograph.

By way of example, at least one of the first current collector, the second current collector, or the current collector assembly may be one of a filament current collector, or a grid current collector, or a wick current collector. Such current collectors may have advantages in terms of their manufacture, their geometric order and reproducibility, and their capillary function. Geometrical order and reproducibility can be advantageous for both temperature control and controlled localized heating. The capillary function may be advantageous for use with an aerosol-forming liquid substrate. When used, 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 filament-type current collector may be embedded within the aerosol generating substrate of the aerosol generating article. Likewise, 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 an aerosol generating liquid substrate, or as part of an aerosol generating device. In the latter configuration, the device may comprise a reservoir for an aerosol-forming liquid substrate. Alternatively, the device may be configured to receive an aerosol generating article, in particular a cartridge which contains an aerosol generating liquid substrate and which is configured to engage with a filament current collector or a mesh current collector or a wick current collector of the device, generating aerosol.

At least one of the first current collector, the second current collector, or the current collector assembly may be a current collector plate, a current collector rod, or a current collector pin. Preferably, the first current collector and the second current collector together form a current collector plate, a current collector rod, or a current collector pin. For example, one of the first or second current collector may form the center or inner layer of the current collector plate, or current collector rod, or current collector pin, while the corresponding other of the first or second current collector may form the sheath or wrap of the current collector plate, or current collector rod, or current collector pin.

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

Alternatively, at least one of the first current collector, second current collector or current collector assembly, each in the form of a current collector plate 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 plate, or the current-collecting rod, or the current-collecting pin can be located at the lower part of the receiving cavity of the device, in particular attached to it. From there, the current-collecting plate or current-collecting rod or 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 far free end of the current collector plate or current collector rod or current collector pin, may be tapered or pointed so as to allow the current collector plate or current collector rod or current collector pin to easily penetrate into the aerosol forming substrate to be heated, for example in an aerosol generating substrate disposed at a distal end portion of the aerosol generating article.

In each case, the current collector plate or the current collector rod or the current collector pin may have a length in the range of 8 mm (millimeters) to 16 mm (millimeters), in particular from 10 mm (millimeters) to 14 mm (millimetres), preferably 12 mm ( millimeters). In the case of a current collector plate, 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 bowl-shaped pantograph. A cylindrical current collector, a current-collecting sleeve, or a cup-shaped current collector may form a receiving cavity or may be arranged circumferentially around the receiving cavity 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 implements 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 bowl-shaped current collector, may surround at least a portion of the aerosol-forming substrate to be heated, thereby realizing heating oven or heating chamber. In particular, each of them may form at least part of the shell, wrapper, housing or body 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 direct 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 electroplated, deposited, coated, applied by cladding, or welded to the first current collector. 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 small changes at the Curie temperature.

The individual layers of the laminated current collector assembly may be exposed or exposed to the environment on the circumferential outer surface of the laminated current collector assembly when viewed in any direction parallel and/or transverse to the 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 multilayer current collector assembly may be an elongated current collector strip or a current collector plate having a length in the range of 8 mm (millimeters) to 16 mm (millimeters), in particular from 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 current collector plate 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, particularly as previously described. In this configuration, one of the first or second current collector may form a core layer which is surrounded by a surrounding layer formed by the corresponding other of the first or second current collector. Preferably, it is the first current collector that forms the surrounding layer in the case where the first current collector is optimized for heating the substrate. Thus, heat transfer to the surrounding aerosol-forming substrate is improved.

Alternatively, the multilayer current collector assembly may be a multilayer current collector sleeve, or a bowl-shaped multilayer current collector, or a cylindrical multilayer current collector, particularly as previously described. One of the first or second pantograph may form the inner wall of the multilayer pantograph sleeve, or the bowl-shaped multilayer pantograph, or the cylindrical multilayer pantograph. A corresponding other of the first or second current collector may form the outer wall of the multilayer current collector sleeve, or the bowl-shaped multilayer current collector, or the cylindrical multilayer current collector. Preferably, it is the first current collector that forms the inner wall, in particular in the case where the first current collector is optimized for heating the substrate. As previously described, the multilayer current collector, or the cup-shaped multilayer current collector, or the cylindrical multilayer current collector may surround at least a portion of the aerosol-forming substrate to be heated, in particular, may form at least a portion of a sheath, wrapper, casing, or body of the article, generating aerosol. Alternatively, a multi-layered current collector, or a multi-layered bowl-shaped current collector, or a cylindrical multi-layer current collector may form a receiving cavity or 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 designed for their particular function. The first current collector, preferably having a heating function, may have a geometric configuration that provides a large surface area to the aerosol-forming substrate in order to improve heat transfer. In contrast, the second pantograph, which preferably has a temperature control function, does not need to have a very large surface area. If the first current collector material is optimized for heating the substrate, it may be preferable that the volume of material of the second current collector material does not exceed the volume necessary to provide a detectable Curie point.

According to this aspect, the second pantograph may include one or more elements of the second pantograph. Preferably, one or more elements of the second pantograph are significantly smaller than the first pantograph, that is, have a volume smaller than the volume of the first pantograph. Each of the one or more elements of the second pantograph may be in direct physical contact with the first pantograph. Because of this, 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 plate, or a current collector strip, or a current collector sleeve, or a cup-shaped current collector, while the second current collector material may be in the form of individual pads that are electroplated, deposited, or welded onto the first current collector material.

According to another example, the first pantograph may be a strip pantograph, a thread pantograph, or a mesh pantograph, while the second pantograph is a particulate pantograph. Both the first filament or mesh current collector and the second particulate current collector may, for example, be incorporated into the aerosol generating article 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 pantographs need not be in direct physical contact with each other. The first current collector may be a current collector plate realizing a heating plate for penetrating into a substrate forming an aerosol to be heated. Similarly, the first current collector may be a current-collecting sleeve or a bowl-shaped current collector realizing 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 pantograph may form part of the sidewall or sleeve portion of the cup-shaped pantograph, while the second pantograph forms the bottom of the cup-shaped pantograph.

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 using glass, ceramic, or an inert metal, formed on or applied to at least portions of the first current collector and/or the second current collector or current collector assembly, respectively. Advantageously, the protective coating may be adapted to at least one of: avoiding adherence of the aerosol-forming substrate to the surface of the current collector; avoid diffusion of material, such as metal diffusion, from current-collecting materials into the aerosol-forming substrate; improve the mechanical rigidity of the current collector. Preferably, the protective coating is electrically non-conductive.

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

The induction source may comprise one induction coil or a plurality of induction coils. The number of induction coils may depend on the number of current collectors and/or the size and shape of the current collector assembly. The induction 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 induction 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.

The at least one induction coil may be a helical coil or a flat coil of a planar type, in particular a disk coil or a bent coil of a planar type. The use of a flat helical coil provides a compact design that is reliable and inexpensive to manufacture. The use of a helical induction coil advantageously generates a uniform alternating electromagnetic field. In the context of this document, the term "flat helical bobbin" means a bobbin that is generally a planar bobbin, with the coil winding axis perpendicular to the plane in which the bobbin lies. The flat helical induction coil may have any desired shape in the plane of the coil. For example, a flat helical coil may be circular in shape, or may be generally oblong or rectangular in shape. However, the term "flat spiral coil" in the context of this document covers both coils that are planar and flat spiral coils whose shape corresponds to a curved surface. For example, the induction coil may be a "curved" planar coil placed 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 induction coil may be held within one of the housing of the heating unit or the body or housing of the aerosol generating device that contains the heating unit. The first and/or second induction coil 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 the power supply of the aerosol generating device. The alternator is operatively connected to at least one induction coil. In particular, at least one induction coil may be an integral part of the alternator. The alternator is configured to generate a high frequency oscillatory current to pass through at least one induction coil to generate an alternating electromagnetic field. The alternating current may be applied to the at least one induction coil continuously after activation of the system, or may be applied intermittently, for example from puff to puff.

Preferably, the induction source comprises a DC/AC converter connected to a DC power supply comprising an inductive-capacitive circuit, the inductive-capacitive circuit comprising 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 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 the main controller, or part thereof, of the aerosol generating device of which the heater assembly of 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 is particularly advantageous in relation to the compact design of the heating unit.

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

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 recharged, i.e. 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 by the user. 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 that is a multiple of six minutes. In another example, the power supply may have sufficient capacity to allow a given number of puffs or individual activations of the induction source to be performed. The power supply may be the main power supply of the aerosol generating device of which the heater 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 generating substrate. The device contains a receiving cavity for placing an aerosol-forming substrate to be heated. The device further comprises an induction heating assembly according to the present invention, as described herein, for inductively heating an aerosol generating substrate within a receiving cavity.

In the context of this document, the term "aerosol generating device" is used to describe an electrical device that can interact with at least one aerosol generating substrate, in particular with 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 a puff device for generating an aerosol 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" means a substrate capable of releasing volatile compounds that can form an aerosol when the aerosol-forming substrate is heated. The aerosol generating substrate is the 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 generating substrate may further comprise an aerosol generating 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 sachet of porous material containing an aerosol-forming substrate, or, for example, loose tobacco mixed with a gelling agent or adhesive, which may contain a conventional aerosolizing agent such as glycerol, and which is pressed or shaped into a rod.

The receiving cavity may be contained within the housing of the aerosol generating device.

As described above, the aerosol generating device may include a main controller for controlling the operation of the device. The main controller may or may include a heating unit controller.

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

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 supply, and at least a portion of the receiving cavity.

In addition to the body, the aerosol generating device may further comprise a mouthpiece, in particular if 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 body. To attach the mouthpiece to the body, the proximal end of the body may comprise a magnetic or mechanical fastener, such as a bayonet or snap fastener, that engages a corresponding mating piece at the distal end of the mouthpiece. In case the device does not include a mouthpiece, 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 an air outlet in the mouthpiece, if present. 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 the mouthpiece into the wearer's mouth.

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

According to the present invention, an aerosol generating system is also provided. The system comprises an aerosol generating device, an aerosol generating article for use with an aerosol generating device, and an induction heating assembly according to the present invention and as 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 the aerosol generating article, while the second current collector of the current collector assembly is either part of the aerosol generating article or part of the aerosol generating device.

Preferably, the first current collector, as part of the aerosol generating article, can 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 plate, a current collector rod, a current collector pin, a current collector mesh, a current collector thread, or a particulate current collector disposed with the aerosol generating substrate of the aerosol generating article.

In contrast, the second pantograph may generally be adapted 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 be located in them. In any configuration, when the article is used with, in particular attached 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. Advantageously, this ensures that the second current collector is 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, proper and accurate temperature control can be achieved. 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 supply unit of the heating unit may be part of the aerosol generating device, in particular be located in it. Preferably, the power supply of the aerosol generating device may comprise or may be a heating unit power supply.

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 that, when heated, releases volatile compounds that can form an aerosol. Preferably, the aerosol generating article is a heated aerosol generating article. That is, the aerosol-generating article preferably contains at least one aerosol-forming 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, in particular a consumable to be discarded 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 substrate forming an aerosol to be heated. Alternatively, the product may be a rod-shaped product, in particular a tobacco product resembling conventional cigarettes and containing an aerosol-forming solid 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-collecting 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 for direct inhalation of 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 generating substrate. The wrapper may include a current collector. Advantageously, this ensures uniform and symmetrical heating of the aerosol-forming substrate surrounded by the current collector assembly.

In particular, with regard to an aerosol generating article having a rod-shaped article resembling conventional cigarettes and/or containing an aerosol-forming solid substrate, the article may further comprise: a support element having a central air passage, a cooling aerosol element, and a filter element . The filter element preferably functions as a mouthpiece. In particular, the article may comprise a substrate element that 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 respect to 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 shroud or wrapper surrounding at least a portion of the aerosol generating substrate. In particular, the article may comprise a wrapper surrounding at least a portion of the various segments and elements mentioned above so as to hold them together and retain the desired sectional shape of the article.

The casing or wrapper may include at least the first current collector or both the first and second current collectors of the current collector assembly. Advantageously, this allows uniform and symmetrical heating of 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 be released from the article or to allow air to be drawn into the article through its circumference. In addition, the wrapper may contain at least one volatile substance to be activated and released from the wrapper upon heating. For example, the wrapper may be impregnated with a flavoring 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 also provides a method for induction heating of an aerosol-forming substrate, particularly comprising such a heating assembly according to the present invention and as described herein. Preferably, the method is a method of operating a heating unit according to the present invention and as described herein, or operating an aerosol generating device according to the present invention and as described herein, or operating an aerosol generating system according to the present invention and as described herein. document.

This method includes the steps:

generating an alternating electromagnetic field by supplying a DC supply voltage and a DC supply current to the induction source to heat a current-collecting assembly inductively coupled to the induction source;

determining, from the DC supply voltage and the DC supply current drawn from the DC power supply, an actual apparent resistance indicative of the actual temperature of a current-collecting assembly that is inductively coupled to or inductively coupled to the induction source;

determination of the minimum value of the apparent resistance during the preheating of the current collector, from room temperature to operating temperature.

The method may further include the steps of:

adjusting the operation of the induction source in a feedback configuration so that the actual apparent resistance corresponds to a certain minimum apparent resistance value plus a predetermined apparent resistance offset value to control heating of the aerosol generating substrate to a predetermined operating temperature.

The stage of regulation of the operation of the induction source includes the following steps:

interrupting the alternating electromagnetic field generation step when the actual apparent resistivity is equal to or greater than the determined minimum apparent resistivity value plus the predetermined apparent resistivity offset value, and

resuming the alternating electromagnetic field generation step when the actual apparent resistivity is below a certain minimum apparent resistivity value plus a predetermined apparent resistivity offset value.

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

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

in fig. 1 is a schematic representation of an aerosol generating system comprising an aerosol generating apparatus with induction heating 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 an induction heated aerosol generating article according to 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 view of an aerosol generating system comprising a heating unit according to a fourth exemplary embodiment of the present invention;

in fig. 18 is a schematic representation 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.

In FIG. 1 schematically shows a first exemplary embodiment of an aerosol generating system 1 according to the present invention. The system 1 comprises an aerosol generating device 10 according to the present invention, as well as an aerosol generating article 100 which is capable of being used with the device and which contains an aerosol generating substrate to be heated.

Onfig. 2 shows additional details of the product 100, generating aerosol, and aerosol-generating article 100 is essentially rod-shaped and comprises four elements aligned in series: aerosol-generating rod segment 110 containing a current-collecting element 120 and aerosol-generating substrate 130, support element 140 containing a central air passage 141, element 150 , a cooling spray, and a filter element 160 that functions as a mouthpiece. The aerosol-forming rod segment 110 is located at the distal end 102 of article 100, while the filter element 160 is located at the distal end 103 of article 100. Each of these four elements is a substantially cylindrical element, all having substantially the same diameter. In addition, the 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 from paper. Additional details about the product, in particular about the four elements, in addition to the features of the current collector assembly 120 within the segment 110 of the rod, are disclosed in the document WO 2015/176898 A1.

With reference to 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 including 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 positioned such that the current collector assembly 120 of the aerosol generating article 100 is exposed to an electromagnetic field when the article 100 is engaged with the device 10. Thus, when the inductive source is activated, the current collector assembly 120 is heated due to eddy currents and/or hysteresis losses, which induced by an 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. From an electronics point of view, the induction source, other than the induction coil 30, is preferably at least partly an integral part of the controller 50.

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

In FIG. 3 shows a detailed view of the current collector assembly 120 used within the aerosol generating product 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 ferromagnetic or ferrimagnetic current collector 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 versus temperature profile that includes a minimum resistance value around the Curie temperature of the second susceptor material.

The corresponding resistance versus temperature profile is shown in FIG. 4 . During the start of heating of the current collector assembly 120 from room temperature T_R, the resistance of the first current collector material increases, while the resistance of the second current collector material decreases with increasing temperature T. The total apparent resistance R_a of the current collector assembly 120, as "seen" by the induction source of the device 10 used for induction heating current collector assembly 120 is determined by the combination of the respective resistance of the first and second current collector materials. When the Curie temperature T_C of the second current-collecting material is reached from below, the decrease in the resistance of the second current-collecting material, as a rule, prevails over the increase in the resistance of the first current-collecting material. Accordingly, the total apparent resistance R_a of the current collector assembly 120 decreases in the temperature range below, in particular approximately below, the Curie temperature T_C of the second current collector material. At the Curie temperature T_C, the second current-collecting material loses its magnetic properties. This causes an increase in the surface layer available for eddy currents in the second current collector material, which is accompanied by a sudden 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 the minimum value R_min y of the Curie temperature T_C of the second current-collecting material, the total apparent resistance R_a of the current-collecting assembly 120 is mainly determined by the increase in the resistance of the first current-collecting material. That is, the total apparent resistance R_a of the current collector 120 increases again towards the operating resistance R_op at the operating temperature T_op. Advantageously, the decrease and subsequent increase in the resistance versus temperature profile relative to a minimum value R_min around the Curie temperature T_C of the second susceptor material is sufficiently distinguishable from the temporal change in total apparent resistance during user puffing. As a result, a minimum value of resistance R_a around the Curie temperature T_C of the second current collector material can be reliably used as a temperature marker to control the heating temperature of the aerosol generating substrate without the risk of being mistaken for a puff by the user. Accordingly, unwanted overheating of the aerosol-generating substrate can be effectively prevented.

To control 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 adjust the operation of the induction source in a feedback and bias configuration so as to maintain the actual apparent resistivity at a value that corresponds to a certain minimum value R_min of the apparent resistivity R_a plus a predetermined bias value ΔR_offset. The offset value ΔR_offset spans the interval 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. Advantageously, this avoids direct control of the heating temperature based on a predetermined target value of the apparent resistivity at the operating temperature T_op. Also, 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.

When the actual apparent resistance equals or exceeds a certain minimum apparent resistance value plus a predetermined apparent resistance offset value, 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. When the actual apparent resistance is below a certain minimum apparent resistance value plus a predetermined apparent resistance offset value, the heating process can be resumed by continuing to generate an alternating electromagnetic field, i.e. by turning on the induction source again or by increasing the output power of the induction source again.

In the present 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. In order to provide a sufficiently large temperature interval of at least 20 degrees Celsius between the marker temperature at the Curie temperature T_C of the second current-collecting material and the operating temperature T_op, the second current-collecting material is chosen to have 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 constituting the first current collector 121 and a second layer constituting the 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 120 is in the form of an oblong strip having a length L of 12 millimeters and a width W of 4 millimeters, that is, both layers have a length L of 12 millimeters and a width W of 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 mu-metal or permalloy strip having a Curie temperature below the operating temperature. It is approximately 10 micrometers thick. The current collector assembly 120 is formed by applying a strip of the second current collector to the strip of the first current collector.

In 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 directly attached 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 pantographs 121, 122 of the two-layer pantograph assembly 120 shown in FIG. 1 and 2. The third pantograph 223 is identical to the first pantograph 221. That is, 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. Advantageously, this provides a highly symmetrical layered structure substantially free of out-of-plane deformations. In addition, the three-layer current-collecting assembly according to FIG. 5 provides higher mechanical stability.

In FIG. 6 shows another embodiment of a strip-shaped current collector assembly 320 that 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 electrolytically superimposed on the first pantograph 321 in the form of a strip. Although the second pantograph 322 is significantly smaller than the first pantograph 321, it is still suitable for being able to accurately control the heating temperature. Advantageously, the current collector assembly 320 shown in FIG. 6 provides significant savings in the second current collector material. In additional embodiments (not shown), there may be more than one second pantograph pad placed in direct contact with the first pantograph.

In 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 so as to extend along the longitudinal axis of the article shown in FIG. 2. As can be seen on one of its end surfaces, the current collector assembly 1020 includes an internal central current collector that forms the second current collector 1022 according to the present invention. The central current collector is surrounded by a sheath current collector, which forms the first current collector 1021 according to the present invention. Since the first current collector 1021 preferably performs a heating function, this configuration is advantageous in terms of direct heat transfer to the surrounding aerosol forming substrate. In addition, the cylindrical shape of the current-collecting pin provides a very symmetrical heating profile, which can be advantageous with respect to a rod-like aerosol generating article.

In FIG. 8-10 schematically depict various aerosol generating articles 400, 500, 600 comprising further embodiments of a current collector assembly that is part of the heating assembly of 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 design of the product. Therefore, similar or identical features are designated with 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. That is, the first and second current collectors 421, 422 are threads that are twisted with each other so as to form a pair of twisted threads. The pair of filaments is located centrally within the aerosol forming substrate 430 and is in direct contact with the substrate 430. The pair of filaments essentially extend along the length of the article 400. performs the heating function. The second current collector 422 is a filament made of mu-metal or permalloy and thus primarily serves as a temperature marker.

The aerosol generating product 500 of FIG. 9 includes a particulate current collector assembly 520. Both the first current collector 521 and the second current collector 522 comprise a plurality of current-collecting particles distributed within the aerosol-forming substrate 530 of the article 500. Thus, the current-collecting 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 mainly serve to heat the surrounding aerosol forming substrate 530. In contrast, the current collector (susceptor) particles of the second current collector 422 are made of mu-metal or permalloy and thus primarily serve as a temperature marker.

An aerosol generating product 600 according to 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 advantageously improves 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 primarily performs a temperature control function and therefore does not need to 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.

In 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. Therefore, similar or identical features are designated with the same reference numerals as in FIG. 1 and 2, but magnified by 2000. In contrast to the embodiment shown in FIG. 1, the current collector assembly 2060 of the heating assembly 2005 according to the embodiment of FIG. 11 is part of an aerosol generating device 2010.

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

Similarly, the aerosol generating device 2010 shown in FIG. 11 essentially 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. That is, the device 2010 includes an induction source comprising a helical induction coil 2030 that circumferentially surrounds a cylindrical receiving cavity 2020. In addition, the device further comprises a current-collecting assembly 2060, which is located within the receiving cavity so as to be exposed to the electromagnetic field generated by the induction coil 2030.

The current collector assembly 2060 is a current collector plate. With its distal end 2064, the current-collecting plate 2060 is located on the lower part of the receiving cavity 2020 of the device 2010. From there, the current-collecting plate extends into the interior of the receiving cavity 2020 towards the opening of the receiving cavity 2020. thus allowing the aerosol generating article 2100 to be inserted 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 collector plate very similar to the two layer current collector assembly 120 shown in FIG. 1-3. Unlike the latter, the distal free end 2063 of the current collector assembly 2060 tapers to allow the plate-shaped current collector assembly to easily penetrate the aerosol generating substrate 2130 within the distal end of the aerosol generating article 2100.

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

In FIG. 13 , fig. 14 and FIG. 15 shows additional 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 2360 essentially 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. Like the current collector assembly 120, the respective distal free end 2163, 2263, 2361 of the current collector nodes 2160, 2260, 2360 is tapered to facilitate penetration into the aerosol generating substrate.

In FIG. 16-18 schematically depict further embodiments of aerosol generating systems 2701, 2801, 2901 according to the present invention, wherein 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 construction of devices 2710, 2810, 2910 and articles 2700, 2800, 2900. Therefore, similar or identical features of the devices are designated 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 plate similar to the two layer current collector assembly 2060 shown in FIG. 11 and FIG. 12, but without the second current collector layer. In this configuration, the first pantograph 2761 essentially forms an induction heating plate since it primarily performs a heating function. In contrast, the second current collector 2762 is a current-collecting 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 current collector may be a current-collecting sleeve that forms at least a portion of the circumferential inner side wall cylindrical receiving cavity 2720, while the second current collector may be a single layer current collector plate to be inserted into the aerosol forming substrate. In the latter configuration, the first pantograph may implement an induction furnace heater or a heating chamber. In either of these configurations, the first and second current collectors 2761, 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.

The aerosol generating device 2810 of the aerosol generating system 2801 shown in FIG. 17 includes a current collector 2860, which is a bowl-shaped current collector, thus realizing an induction furnace heater or a heating chamber. In this configuration, the first current collector 2861 is a current collector sleeve forming the circumferential side wall of the cup-shaped current collector assembly 2860 and thus at least a portion of the inner side wall of the cylindrical receiving cavity 2820. In contrast, the second current collector 2862 forms the bottom of the cup-shaped current collector assembly 2860 . Both 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.

The 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 for heating the aerosol forming substrate 2130, closer to the substrate 2130. Advantageously, the current collector assembly 2960 also implements an induction furnace heater or heating chamber.

In 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. Therefore, 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. 19, the current collector 3760 of the heating unit 3705 according to the embodiment of FIG. 16 divided. While the first current collector 3761 of the current collector assembly 3760 is part of the aerosol generating product 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 the article 3100 and without the second current collector layer. Thus, the first current collector 3761 essentially forms an induction heating element as an integral part of the product 3100. The second current collector 2762 is a current-collecting sleeve that forms at least a portion of the circumferential inner side wall of the receiving cavity 2720, implements an induction furnace heater or a heating chamber. Although the second pantograph 3762 is located at a distance from the first pantograph 3761, it is still in thermal proximity with the first pantograph 3761 and the aerosol forming substrate 3130 and thus can be easily used as a temperature marker.

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

Claims (29)

1. An induction heating unit for heating an aerosol-forming substrate to an operating temperature, the heating unit comprising: a DC power supply configured to supply a DC power supply voltage and a DC power supply current; an induction source connected to a DC power supply and configured to generate an alternating electromagnetic field, a susceptor assembly for inductively heating an aerosol-forming substrate under the influence of an alternating magnetic field generated by 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 operating temperature, with the first and second susceptor materials selected such that during preheating of the susceptor assembly, starting at room temperature, the resistance versus temperature profile of the susceptor assembly has a minimum apparent resistivity over a temperature range of ±5 degrees Celsius near the Curie temperature second susceptor material; a controller operatively connected to the induction source and DC power supply and configured to: determining from the DC supply voltage and DC supply current, from the DC power supply, the actual apparent resistance of the susceptor node, which indicates the actual temperature of the susceptor node, determining the minimum value of apparent resistance that occurs during preheating of the susceptor node from room temperature to operating temperature, and controlling the induction source in a feedback configuration such that the actual apparent resistance corresponds to the sum of the minimum apparent resistance value determined above and the apparent resistance offset set value, to control the heating of the aerosol generating substrate to the operating temperature. 2. The heating unit according to claim 1, characterized in that the controller comprises at least one of a DC voltage sensor for measuring the DC supply voltage from the DC power supply, or a DC current sensor for measuring the DC supply current supplied from the DC power supply. 3. A heating unit according to any one of the preceding claims, characterized in that the induction source comprises at least one inductor. 4. The heating unit according to claim. 3, characterized in that the inductor is a helical coil or a planar-type flat coil, in particular a disk coil or a planar-type curved coil. 5. Heating unit according to any one of paragraphs. 3 or 4, characterized in that the induction source contains a DC / AC converter connected to a DC power supply containing an inductive-capacitive circuit, while the inductive-capacitive circuit contains a series connection of a capacitor and an inductor. 6. Heating unit according to any one of the preceding claims, characterized in that the controller and at least part of the induction source, in particular the induction source, in addition to the inductor, are located on a common printed circuit board. 7. A heating unit according to any one of the preceding claims, characterized in that the minimum value of the apparent resistance is in the temperature range of ± 5 degrees Celsius around the Curie temperature of the second susceptor material. 8. 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. 9. Heating unit according to any of the preceding claims, characterized in that the 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. 10. A 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 comprises a second susceptor material having a negative temperature coefficient of resistance. 11. An aerosol generating device for generating an aerosol by heating an aerosol generating substrate, the device comprising: a receiving cavity for accommodating an aerosol-forming substrate to be heated; And an induction heating unit according to any one of the preceding claims for inductively heating an aerosol-forming substrate within the receiving cavity. 12. An aerosol generating system comprising an aerosol generating device and an aerosol generating article for use with an aerosol generating device, characterized in that the system comprises an induction heating assembly according to any one of paragraphs. 1-10, wherein the induction source and DC power supply of the heating assembly are part of an aerosol generating device, wherein the first susceptor of the susceptor assembly is part of an aerosol generating article, and wherein the second susceptor of the susceptor assembly is part of an aerosol generating article or part aerosol generating device. 13. The method of operation of the heating unit according to any one of paragraphs. 1-10, or operation of an aerosol generating device according to claim 11, or operation of an aerosol generating system according to claim 12, wherein the method includes the steps of: generating an alternating electromagnetic field by applying a DC supply voltage and a DC supply current to the induction source so as to heat the susceptor assembly inductively coupled to the induction source; determining, from the DC supply voltage and the DC supply current from the DC power supply, the actual apparent resistance indicative of the actual temperature of the susceptor node; determining a minimum apparent resistivity value during preheating of the susceptor assembly from room temperature to operating temperature; controlling the induction source in a feedback configuration so that the actual apparent resistance corresponds to the sum of the minimum apparent resistance value determined above and the apparent resistance offset set value, to control heating of the aerosol generating substrate to a predetermined operating temperature. 14. The method according to claim 13, characterized in that the step of controlling the induction source includes the steps: interrupting the alternating electromagnetic field generation step when the actual apparent resistivity is equal to or greater than the sum of the minimum apparent resistivity value determined above and the predetermined apparent resistivity offset value, and resuming the alternating electromagnetic field generation step when the actual apparent resistivity is lower than the sum of the minimum apparent resistivity value determined above and the predetermined apparent resistivity offset value.

Images