RU2840681C2 - Aerosol generating device with puff detection - Google Patents

Abstract

FIELD: smoking accessories.

SUBSTANCE: aerosol-generating device for generating an aerosol from an aerosol-forming substrate. Aerosol-generating device may comprise a device body defining a chamber for receiving an aerosol-forming substrate; an air flow passage extending from the air inlet in the housing of the device through the chamber or in fluid communication with the chamber; and a puff sensor assembly comprising a heat transfer element and a temperature sensor in contact with the heat transfer element. First part of the air flow channel is at least partially formed by the wall of the air flow channel, and the second part of the air flow channel is at least partially formed by the heat transfer element, wherein the second part of the air flow channel is adjacent to the first part and is located outside the chamber. At least one of the heat conductivity and thermal diffusivity of the heat transfer element is greater than the corresponding thermal conductivity or thermal diffusivity of the wall of the air flow channel.

EFFECT: broader functional capabilities.

16 cl, 9 dwg

Description

The present invention relates to an aerosol generating device for generating an aerosol from an aerosol forming substrate. The present invention also relates to an aerosol generating system that comprises the aerosol generating device and to a method for detecting a user's puff on the aerosol generating device.

In the field of the art to which the present invention pertains, aerosol generating devices are known that are capable of generating an aerosol from an aerosol-forming substrate, such as a tobacco-containing substrate. Such devices typically generate an aerosol from a substrate by applying heat to the substrate, rather than by burning the substrate. In use, an aerosol generating device may accommodate an aerosol-forming substrate, for example, in a chamber of the device. The device may supply power to a heater assembly to heat the heater assembly, wherein the heat is transferred to the aerosol-forming substrate to release volatile compounds that condense to form an aerosol. Some aerosol generating devices comprise a puff detection system capable of automatically detecting when a user puffs on the device. Puff detection may be used in various ways. For example, a controller of the aerosol generating device may count the number of puffs detected with respect to a particular aerosol-generating article that is accommodated. If this number of puffs reaches or exceeds a predetermined number of puffs, the controller may inform the user of the device or even prevent use of the device until the aerosol-generating article is replaced. In another example, puff detection may be used to control the immediate supply of power to a heating element or other aerosol-generating element, such that increased power is provided when a puff is detected.

An illustrative known aerosol generating device that comprises a puff detection system comprises a heater assembly comprising a heating plate. The heating plate is configured to penetrate, when used, an aerosol generating article placed into the aerosol forming substrate. When used, power is supplied to the heating plate to heat the placed aerosol generating article in order to release volatile compounds. During a puff by the user, air is drawn through the aerosol forming substrate. This air has a cooling effect on the heating plate and thus causes a drop in resistance of at least one heating track formed from a material whose resistance depends on the temperature. By monitoring the resistance of said at least one heating track, puffs can be detected in accordance with the drop in resistance.

Such an arrangement has no practical significance for aerosol-generating devices that use an external heater assembly that heats the aerosol-generating substrate from the outside of the substrate, rather than from the inside of it. For example, a resistive heater assembly may surround a chamber wall of an aerosol-generating device, wherein the wall forms a chamber for housing an aerosol-generating article. In use, the heater assembly heats the chamber wall, and this heat is then transferred to the aerosol-generating substrate of the housed aerosol-generating article. The above-described puff detection system is not suitable for use in aerosol-generating devices that include such an external heater system, since air drawn through the aerosol-generating substrate when a user puffs does not pass over the external heating element. The cooling effect of such a user puff on the heating element is so small that it is difficult to measure.

It would be desirable to provide an aerosol generating device with a puff detection system that is more sensitive to user puffs than known systems. A more sensitive puff detection system would allow for more accurate puff counting, for example to reduce the likelihood of exceeding a maximum puff count of a particular aerosol generating product. A more sensitive puff detection system could also be used to control immediate power delivery to a heating element. It would also be desirable to provide an aerosol generating device that includes a puff detection system that has increased sensitivity regardless of whether the aerosol generating device includes an internal heater assembly or an external heater assembly.

In the first aspect, an aerosol generating device is proposed for generating an aerosol from an aerosol-forming substrate. The aerosol generating device may comprise a device housing. The device housing may form a chamber for accommodating the aerosol-forming substrate. The aerosol generating device may comprise an air flow channel. The air flow channel may extend from an air inlet in the device housing. The air flow channel may extend through the chamber. Alternatively, the air flow channel may be in fluid communication with the chamber. The aerosol generating device may comprise a puff sensor assembly. The puff sensor assembly may comprise a heat transfer element. The puff detector assembly may comprise a temperature sensor. The temperature sensor may be in contact with the heat transfer element. The first portion of the air flow channel may be at least partially formed by the wall of the air flow channel. The second portion of the air flow channel may be at least partially formed by the heat transfer element. The second portion of the air flow channel may be adjacent to the first portion. The second part may be located outside the chamber. At least one of the thermal conductivity or the thermal diffusivity of the heat transfer element may be greater than the corresponding thermal conductivity or the thermal diffusivity of the wall of the air flow duct. For example, the thermal conductivity of the heat transfer element may be greater than the thermal conductivity of the wall of the air flow duct. Alternatively or additionally, the thermal diffusivity of the heat transfer element may be greater than the thermal diffusivity of the wall of the air flow duct. At least one of the thermal conductivity or the thermal diffusivity of the heat transfer element may be 2 times, 5 times, 10 times, 25 times or 100 times greater than the corresponding thermal conductivity or the thermal diffusivity of the wall of the air flow duct. Both the thermal conductivity and the thermal diffusivity of the heat transfer element may be 2 times, 5 times, 10 times, 25 times or 100 times greater than the corresponding thermal conductivity and the thermal diffusivity of the wall of the air flow duct.

The aerosol generating device may comprise a heater assembly for heating an aerosol forming substrate, which is placed in a chamber. Alternatively, the chamber may be configured to accommodate a cartridge containing an aerosol forming substrate, wherein the cartridge comprises a heater assembly.

The second part of the air flow channel may be located upstream relative to the chamber. The second part of the air flow channel may be located further downstream relative to the chamber. This may ensure that the second part of the air flow channel is not blocked by the aerosol-forming substrate located in the device and that it is in direct contact with the air flow. The advantage of installing the second part in a certain position upstream relative to the chamber may be contact of the cooling atmospheric air with the second part. The advantage of installing the second part in a certain position upstream relative to the chamber may be minimizing the deposition of aerosol condensates on the second part of the air flow channel. The air flow channel may contain several parallel branches, and the second part may be installed in a certain position in the first branch parallel to the second branch, which contains the chamber. The second part of the air flow channel may be adjacent to the chamber. The chamber may be external relative to the air flow channel. In this case, the chamber may be adjacent to the second part of the air flow channel and communicate with it via a fluid medium.

In use, an aerosol-forming substrate may be placed in a chamber. Power from a power source of the aerosol-generating device may be supplied to the heater assembly. If the heater assembly is part of a placed cartridge, the aerosol-generating device may comprise electrical connections for connecting to corresponding electrical connections on the cartridge when the cartridge is placed in the chamber. Power may be supplied via electrical connections of the device and the cartridge. In either case, the heater assembly heats the aerosol-forming substrate so that volatile compounds of the substrate evaporate. Since the air flow channel extends through the chamber or is in fluid communication with it, vapor passes into the air flow channel. In use, air may be drawn through the air flow channel by a user who puffs on the aerosol-generating device or on an aerosol-generating article that is placed in the device and contains the aerosol-forming substrate. Air may enter the air flow channel through an air inlet.

Since the second part of the air flow channel can be at least partially formed by the heat transfer element, the air drawn through the air flow channel will pass over the heat transfer element. Preferably, the air drawn through the channel from outside the device has a lower temperature than the heat transfer element, and therefore the passing air exerts a cooling effect on the heat transfer element. This cooling effect can be the result of heat transfer from the heat transfer element to the cooling air passing by the heat transfer element. This heat transfer can advantageously lead to a decrease in the temperature of the heat transfer element.

The temperature sensor may be in contact with the heat-transmitting element, so that changes in the temperature of the heat-transmitting element can be detected using the temperature sensor. In particular, using the temperature sensor, it is possible to detect a decrease in the detectable temperature of the heat-transmitting element. Signals from the temperature sensor can be received by the controller of the aerosol-generating device, which is designed to detect a user's puff based on said decrease in the temperature of the heat-transmitting element.

The sensitivity of the puff sensor assembly to user puffs may depend on how quickly the cooling caused by the air flowing through the second part is detected by the temperature sensor. This, in turn, may depend on how quickly the heat is transferred through the heat transfer element. For example, the first surface of the heat transfer element may at least partially form the second part of the air flow channel. The temperature sensor may be in contact with the second surface of the heat transfer element. The cooling air in the air flow channel, as it flows over said first surface, will cause immediate cooling of the first surface of the heat transfer element, but there may be a delay before a significant change in temperature on the second surface of the heat transfer element, which can be detected using the temperature sensor. The faster the heat flow from the second surface to the first surface, the more sensitive the puff sensor assembly may be to a puff.

Heat moves faster through materials with higher thermal conductivity. Therefore, if the heat transfer element has a thermal conductivity greater than the wall of the air flow channel, heat will move faster through the heat transfer element than through the wall of the air flow channel. Thus, a temperature sensor that is in contact with the heat transfer element, rather than with the wall of the air flow channel, can advantageously lead to a puff detection unit that has increased sensitivity to puffs. This may be due to the fact that changes in the detected temperature of the heat transfer element during a user's puff can be rapid and pronounced. Based on such a change, the controller of the aerosol generating device can advantageously have the ability to reliably detect a user's puff even when using an inexpensive temperature sensor.

The heat transfer element may have a thermal conductivity of at least approximately 100 watts per meter-kelvin. The heat transfer element may have a thermal conductivity of no more than 300 watts per meter-kelvin.

The presence of a heat transfer element having a thermal conductivity greater than the thermal conductivity of the air flow channel wall may also result in a puff detection unit having increased sensitivity to puffs, the cause of which may be the speed and severity of changes in the detected temperature of such a heat transfer element during a user's puff.

The thermal diffusivity of a material is defined as the thermal conductivity of the material divided by the product of its density and specific heat capacity at constant pressure. The product of density and specific heat capacity at constant pressure is also known as the volumetric heat capacity. The thermal diffusivity of a material is relevant when the system is not at steady state. It describes the rate of temperature propagation through the material to achieve thermal equilibrium. This property may not be described by thermal conductivity alone. For example, a first and second material may both have the same thermal conductivity, but the first material may have a higher volumetric heat capacity than the second material, in which case the first material has a lower thermal diffusivity than the second material. The higher the volumetric heat capacity, the greater the energy change required per unit volume of the material to change its temperature by one degree Kelvin. Thus, a first material and a second material may have the same thermal conductivity (i.e. the same ability to conduct heat), but the temperature of the second material, with its higher thermal diffusivity, will change faster than that of the first material when both are subjected to the same initial conditions in an unstable state. The reason for this is that less energy is required to achieve each one degree Kelvin change in temperature per unit volume of the first material compared to the second material.

By providing a heat transfer element having a thermal diffusivity greater than the thermal diffusivity of the air flow channel wall, the detectable change in the temperature of the heat transfer element can advantageously be faster and more pronounced than the change in the temperature of the air flow channel wall immediately after the start of the puff. As described above, the fast and pronounced change in the detectable temperature of the heat transfer element during the user's puff advantageously makes it possible for the controller of the aerosol generating device to reliably detect the user's puff.

The heat transfer element may have a thermal diffusivity of at least 50 square millimeters per second. Preferably, the heat transfer element may have a thermal diffusivity of more than 60, 70, 80, or most preferably 90 square millimeters per second.

Since thermal diffusivity is related to thermal conductivity, a material that has high thermal diffusivity may also have high thermal conductivity. Therefore, a heat transfer element may have both higher thermal diffusivity and higher thermal conductivity than the air flow duct wall.

A puff sensor assembly comprising a heat transfer element at least partially forming a second portion of an air flow channel is advantageously compatible with aerosol generating devices that comprise an external heater assembly or an internal heater assembly. In either case, air drawn through the air flow channel can have a cooling effect on the heat transfer element, allowing the controller to quickly and reliably detect a user's puff.

Preferably, when the aerosol generating device is in use, the heat transfer element can be heated above the ambient temperature. During puffs, between puffs, or both during puffs and between puffs, the heat transfer element can be heated to a temperature of at least 5 degrees Celsius above the ambient temperature. The heat transfer element can be heated to a temperature of at least 10, 20, 40 or 80 degrees Celsius above the ambient temperature. The heat transfer element can be heated to a temperature of 5 degrees Celsius to 80 degrees Celsius above the ambient temperature. Heating can occur before the user's first puff. Heating the heat transfer element above the ambient temperature advantageously increases the difference between the temperature of the heat transfer element and the temperature of the air drawn through the air flow channel. This can increase the cooling rate of the heat transfer element in response to a user's puff and thus advantageously results in an even more pronounced or sharp drop in the temperature of the heat transfer element, which further increases the speed and reliability of puff detection using the puff detection unit.

As described above, a heat transfer element having a higher thermal conductivity than the wall of the air flow duct results in a faster movement of heat through the heat transfer element than through the wall of the air flow duct. This may also be advantageous when heating the heat transfer element above the ambient temperature. Such a heat transfer element will heat up above the ambient temperature relatively quickly compared to the wall of the air flow duct, which means that the puff detection unit will be ready to detect a puff soon after the heating process of the heat transfer element is started. For similar reasons, it may be particularly advantageous to provide a heat transfer element having a thermal diffusivity higher than the thermal diffusivity of the wall of the air flow duct.

The aerosol generating device may comprise a heating element, and during use and between puffs, the heat transfer element may be heated to a temperature of at least 5 degrees Celsius above the ambient temperature by the heating element.

In those embodiments where the aerosol generating device comprises a heater assembly for heating an aerosol forming substrate located in the chamber, the heater assembly may comprise a heating element. Heating of the heat transfer element may result from heat transfer from the heating element of the heater assembly to the heat transfer element. During use and between puffs, the heat transfer element may be heated by the heating element to a temperature of at least 5 degrees Celsius above the ambient temperature. The heat transfer element may be heated by the heating element to a temperature of at least 10, 20, 40 or 80 degrees Celsius above the ambient temperature. The heat transfer element may be heated by the heating element to a temperature of 5 degrees Celsius to 80 degrees Celsius above the ambient temperature. Heat may be transferred from the heater assembly directly to the heat transfer element. For example, the heat transfer element may be in contact with the heater assembly, and heat may be transferred by conduction via a contact point between the heat transfer element and the heating element located outside the chamber. If the heater assembly is part of a cartridge, then when the cartridge is placed in the chamber, contact may occur between the heater assembly and the heat transfer element on the cartridge.

Alternatively, the heater assembly and the heat transfer element can be spaced apart, and the heat can be transferred by radiation and, alternatively or additionally, by conduction through other components of the aerosol generating device located between the heater assembly and the heat transfer element. The smaller the distance between the heater assembly and the heat transfer element, the greater the amount of heat transfer from the heater assembly to the heat transfer element. Preferably, the distance between the heater assembly and the heat transfer element is less than 50 millimeters. Even more preferably, the distance between the heater assembly and the heat transfer element is less than 10 millimeters or less than 5 millimeters. The distance between the heater assembly and the heat transfer element can be 0 millimeters. The distance between the heater assembly and the heat transfer element can be measured as the minimum distance between the heating element of the heater assembly and the heat transfer element. If the heater assembly is part of a cartridge, the distance between the heater assembly and the heat transfer element can be measured when the cartridge is placed in the chamber.

Alternatively or additionally, the puff sensor assembly may comprise a specialized heating element for heating the heat transfer element. For example, the temperature sensor may be a heated thermistor. Such a temperature sensor may be heated when power is applied. In use, heat from the heated thermistor may be transferred to the heat transfer element. The thermistor, which is in contact with the heat transfer element, may advantageously cause targeted heating of the heat transfer element. Since the wall of the air flow channel has a lower thermal conductivity than the heat transfer element, heat conduction away from the heat transfer element through the wall of the air flow channel may be relatively weak.

Passive heating of the heat transfer element by the heater assembly is advantageously characterized by lower power consumption and complexity than active heating by a dedicated heating element, for example when using a heated thermistor. However, an advantage of the active heating device may be the ability to place the puff sensor assembly anywhere along the length of the air flow channel. An advantage of the active heating device may also be the ability to heat the heat transfer element before actuating the heater assembly to heat the aerosol-forming substrate. Thus, the heater assembly for heating the aerosol-forming substrate may be actuated in response to a detected puff of the user. The active heating device may also be controlled so that the heat transfer element is heated only when the heater assembly is not actuated to heat the aerosol-forming substrate. For example, the heat transfer element may be heated intermittently or periodically to maintain its temperature above a threshold value during intervals between detected puffs.

Preferably, in use, as much of the heat generated by the heater assembly as possible is absorbed by the aerosol-forming substrate, which is located in the chamber. Although it may be advantageous for some of the heat to be released from the chamber and transferred to the heat transfer element, as described above, heat released beyond the heat transfer element to other components of the aerosol-generating device may be considered lost. An air flow channel wall having a thermal conductivity lower than that of the heat transfer element may advantageously reduce heat loss. A suitable material for the air flow channel wall may be a material containing plastics, such as thermoplastic materials, for example, polypropylene, polyetheretherketone (PEEK) and polyethylene. Such materials advantageously have a relatively low thermal conductivity.

The heat transfer element may extend along the air flow channel for a distance of less than 10 percent of its length. Preferably, the heat transfer element may extend along the air flow channel for a distance of less than 5 percent of its length. The heat transfer element may extend along the length of the air flow channel for a distance of from 2 millimeters to 10 millimeters. This may advantageously reduce heat losses, since only a small proportion of the air flow channel may be formed by the heat transfer element having a higher thermal conductivity than the wall of the air flow channel. Then the air flow channel may advantageously be formed by the wall of the air flow channel having a lower thermal conductivity, at least outside the chamber.

The heat transfer element may be integrated into the wall of the air flow channel. Preferably, the heat transfer element may be mounted in the wall of the air flow channel by means of a press fit. Such a heat transfer element may be effectively insulated from the chamber by means of the wall of the air flow channel, thereby reducing heat losses by conduction through the heat transfer element. This may be particularly advantageous when the puff sensor assembly comprises a dedicated heater for heating the heat transfer element during use.

The heat transfer element may be installed by means of a press fit in a part of the wall of the air flow channel, forming a channel with a diameter equal to or, preferably, somewhat smaller than that of the heat transfer element, before pressing the heat transfer element into the wall of the air flow channel. Then pressing the heat transfer element into the wall of the air flow channel may somewhat deform the wall of the air flow channel, due to which it may hold the heat transfer element in place after it is pressed into the air flow channel. The wall of the air flow channel may comprise a step formed on an abrupt change in the diameter of the air flow channel. The heat transfer element may adjoin the step.

Earlier in the flow direction relative to the heat transfer element, the wall of the air flow channel may form a narrowing air flow channel. The diameter of the air flow channel may decrease in a direction further along the flow direction. At its smallest diameter, the air flow channel may have a diameter smaller than that of the heat transfer element. The narrowing of the air flow channel may end with a step increase in the diameter of the channel formed by the wall of the air flow channel. This step increase may provide a surface to which the heat transfer element may abut when inserted into the wall of the air flow channel.

The wall of the air flow channel may comprise an opening. This opening may be adjacent to the heat transfer element. The temperature sensor may be in contact with the heat transfer element via the opening.

The thickness of the heat transfer element may be from 0.1 millimeters to 2 millimeters. Preferably, the thickness of the heat transfer element may be from 0.1 millimeters to 0.5 millimeters. Such a thickness may result in a heat transfer element that has a strength suitable for withstanding the processes involved in manufacturing the aerosol generating device, in particular, when pressing the heat transfer element into the air flow channel, and at the same time also results in a heat transfer element that has a low mass per unit length. The lower the mass per unit length of the heat transfer element, the faster the heat transfer element will cool when air is drawn through the air flow channel during the user's puff. In addition, the time it takes to cool the second surface of the heat transfer element, which is in contact with the temperature sensor, after the user draws air through the air flow channel, may depend on the shortest distance between the temperature sensor and the first surface of the heat transfer element, which at least partially forms the second part of the air flow channel. The shorter this distance, the faster the temperature drop can be detected, which is an indicator of the user's puff. The shortest distance between the temperature sensor and the first surface of the heat transfer element may depend on the thickness of the heat transfer element. For example, if the first surface of the heat transfer element is opposite the second surface, the shortest distance between the temperature sensor and the second surface of the heat transfer element can be equal to the thickness of the heat transfer element. A thickness of less than 2 millimeters or, preferably, less than 0.5 millimeters can advantageously be small enough for the cooling during the user's puff to be quickly detected by means of the temperature, which ensures the sensitivity of the puff sensor assembly.

As stated above, the first surface of the heat transfer element may at least partially form the second part of the air flow channel. The larger the area of the first surface, the stronger the cooling effect of the air passing through the air flow channel during puffing. The area of the first surface of the heat transfer element may preferably be at least 1, 2, 5, 10 or 20 square millimeters.

The heat transfer element may comprise or be composed of metal. The heat transfer element may comprise or be composed of aluminum. Aluminum is particularly preferred as a material with a relatively low density compared to other metals and a thermal conductivity of 247 watts per meter-Kelvin.

The heat transfer element may have the form of a sheet having a length, a width and a thickness. This may advantageously result in a heat transfer element having a large surface area to mass ratio compared to other forms of heat transfer element, which facilitates rapid cooling of the heat transfer element when air passes over the surface of the heat transfer element. Preferably, the thickness of the heat transfer element may be substantially less than the length and width. For example, the thickness of the heat transfer element may be at least five times less than the length and width. Preferably, the thickness of the heat transfer element may be at least ten times less than the length and width.

The heat transfer element may be tubular. This form is another form of the heat transfer element, which may have a larger surface area to mass ratio. The inner surface of the tubular heat transfer element may at least partially form the second part of the air flow channel. In other words, the air flow channel may be formed by the heat transfer element. The tubular heat transfer element may surround the air flow channel. When the heat transfer element is tubular, the thickness of the heat transfer element may be the shortest distance between the inner surface of the tubular heat transfer element and the outer surface of the tubular heat transfer element.

Several preferred features of the heat transfer element have been described above. Each of them increases the sensitivity of the heat transfer element to temperature changes during a user's puff, each of which leads to a pronounced or sharp drop in the temperature of the heat transfer element and, thus, increases the speed and reliability of puff detection using the puff detection unit. Of course, a heat transfer element that combines two or more of these preferred features can lead to an even more sensitive puff detection unit.

As described above, the temperature sensor can be in contact with the second surface of the heat transfer element, which differs from the first surface of the heat transfer element, at least partially forming the second part of the air flow channel, and thus the heat transfer element is located between the air flow channel and the temperature sensor. For example, when the heat transfer element has the form of a sheet, the first surface can be opposite the second surface. When the heat transfer element is a tubular heat transfer element, the inner surface of the tubular heat transfer element can at least partially form the air flow channel, and the temperature sensor can be in contact with the outer surface of the tubular heat transfer element. An advantage of such arrangements is the possibility of protecting the temperature sensor by the heat transfer element from dust, dirt or residues from the placed substrate forming an aerosol, which pass through the air flow channel.

The aerosol generating device may include a mouthpiece.

Alternatively, the aerosol generating device may be configured to accommodate an aerosol generating article, wherein the aerosol generating article comprises an aerosol forming substrate at or near the distal end. The aerosol generating article may comprise a mouthpiece at the proximal end. For example, during operation, the aerosol generating article may be partially accommodated in a chamber of the aerosol generating device, such that the mouthpiece at the proximal end protrudes from the chamber.

When the aerosol generating device comprises a heater assembly for heating an aerosol forming substrate which is arranged in a chamber, the heat transfer element may partially form an air flow path upstream or downstream of the heater assembly. However, the heat transfer element preferably partially forms an air flow path upstream of the heater assembly. The reason for this is that the air in the air flow path downstream of the heater assembly may be hotter than the air in the air flow path upstream of the heater assembly. This may be a result of the heating of the air downstream of the heater assembly, which is heated after passing through or near the chamber. Thus, the cooling air upstream of the heater assembly will advantageously have a greater cooling effect, which may result in a sharper and more pronounced drop in the temperature of the heat transfer element.

In the context of this document, the terms "upstream" and "downstream" are used to describe the relative positions of components or portions of components of an aerosol generating device with respect to the direction in which fluid flows through the aerosol generating device in use. The term "downstream" refers to a position relatively closer to the mouth end of the device. The term "upstream" may refer to a position relatively further from the mouth end and closer to the opposite end.

The chamber may be a heating chamber. The chamber may have a cylindrical shape. The chamber may have a hollow cylinder shape. The chamber may be tubular. The chamber may have a circular cross-section. If necessary, the chamber may have a shape deviating from a cylindrical shape, or a cross-section deviating from a circular cross-section. The chamber may have a shape corresponding to the shape of the aerosol-generating article to be placed in the chamber. The chamber may have an elliptical or rectangular cross-section. The chamber may have a base at the end of the chamber located upstream. The base may be circular. One or more air inlets may be located in the base or adjacent to it. The air flow channel may pass through the chamber. A mouthpiece may be located upstream of the chamber, between the aerosol-generating article and the user. Alternatively, the user may inhale directly on the aerosol-generating article. The air flow channel may pass through the mouthpiece.

The device body forming the chamber may connect the chamber base at the upstream end of the chamber to the downstream end of the chamber. The downstream end of the chamber may be open. The open downstream end may be configured to receive an aerosol generating article.

When the aerosol generating device comprises a heater assembly comprising a heating element, the heating element may surround the chamber. The heating element may surround the chamber along a portion of the chamber length. The heating element may surround a region of the chamber in which an aerosol forming substrate is placed. The device housing, which forms a portion of the chamber that is surrounded by the heating element, may be made of metal, such as stainless steel, or ceramic. Alternatively, the heating element may be enclosed in the device housing such that the heating element forms a portion of the chamber. The heating element may surround an aerosol forming substrate that is placed in the chamber.

The chamber may be tubular, and the aerosol generating device may comprise a heater assembly for heating the aerosol forming substrate, which is located in the chamber. The heater assembly may comprise a heating element surrounding the outer portion of the chamber.

Alternatively, the heating element may be contained in a cartridge.

In use, power may be supplied to the heating element, causing the heating element to heat up. The heat may then be transferred to the placed aerosol-forming substrate, such as by conduction through the device housing, which forms the chamber.

In one example, an aerosol generating device may comprise a heater assembly, and the heating element may be a resistive heating element. The heating element may comprise an electrically resistive material. Suitable electrically resistive materials include, but are not limited to: semiconductors such as doped ceramics, electrically "conductive" ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys, and composites made of a ceramic material and a metallic material. Such composites may include doped and undoped ceramics.

The aerosol generating device may comprise a power supply unit which may be configured to supply current to the resistive heating element.

The heating element may comprise a substrate layer of flexible material. The substrate layer may comprise a heat-resistant polymer, preferably polyimide.

The heating element may be located on the substrate layer. The heating element may be a resistive heating element. The heating element may comprise wire connections configured to be connected to a controller of the aerosol generating device. The heating element may comprise heating tracks located on the substrate layer. The heating tracks may comprise a heat-conducting material, preferably a metal such as stainless steel. The heating tracks may be electrically connected to said wire connections.

The heating element may also take other forms, such as a metal grid or grids, a flexible printed circuit board, a molded interface device (MID), a ceramic heater, a flexible carbon fiber heater, or may be formed using a coating technology such as plasma vapor deposition on a substrate of a suitable shape.

In another example, the heater assembly may comprise one or more induction coils, and the heating element may comprise one or more current collecting elements.

One or more current-receiving elements may be configured to be heated by an alternating magnetic field generated by an induction coil or coils. In use, electrical power supplied to the induction coil (e.g., by the above-mentioned power supply unit of the device) causes the induction coil to induce eddy currents in the current-receiving element. These eddy currents, in turn, cause the current-receiving element to generate heat. Electrical power is supplied to the induction coil in the form of an alternating magnetic field. The alternating current may have any suitable frequency. The alternating current may preferably be a high-frequency alternating current. The alternating current may have a frequency of 100 kilohertz (kHz) to 30 megahertz (MHz). When the aerosol-forming substrate is placed in the chamber, the heat generated by the current-receiving element may heat the aerosol-forming substrate to a temperature sufficient to cause the aerosol to be emitted from the substrate. The current collecting element is formed from a material having the ability to absorb electromagnetic energy and convert it into heat. As an example and without limitation, the current collecting element can be formed from a ferromagnetic material, such as steel.

The aerosol generating device may comprise a current collecting element. Preferably, the current collecting element may surround the chamber or form at least a part of the chamber, as described above, and the induction coil may be a helical coil surrounding the current collecting element. Preferably, the induction coil may surround the current collecting element radially outside the current collecting element. The arrangement of the induction coil radially outside the current collecting part makes it possible to avoid damage to the induction coil upon contact with the aerosol forming substrate during insertion of the article into the chamber.

Alternatively, the current-collecting element may be part of a cartridge placed in the chamber. The cartridge may comprise the current-collecting element. The cartridge may also comprise an induction coil. Alternatively, the aerosol-generating device may comprise the induction coil. The induction coil of the aerosol-generating device may be designed such that it surrounds the current-collecting element of the cartridge or is adjacent to it when the cartridge is placed in the chamber.

In the context of this document, the term "current collector" or "current collector element" means a conductive element that heats up when exposed to a changing magnetic field. This may be a result of eddy currents induced in the current collector element or hysteresis losses (or both eddy currents induced in the current collector element and hysteresis losses). Possible materials for the current collector include graphite, molybdenum, silicon carbide, stainless steel, niobium, aluminum, and essentially any other conductive elements. Advantageously, the current collector element is a ferrite element. The material and geometry for the current collector element can be selected to provide a desired electrical resistance and heat generation. The current collector element can comprise, for example, a mesh, a flat spiral coil, fibers, or fabric. Advantageously, the current collector is in contact with the first substrate that forms the aerosol. The current collecting element may advantageously be permeable to the fluid medium.

The aerosol generating device may comprise a controller. The controller may be a microprocessor, which may be a programmable microprocessor, a microcontroller, or an application-specific integrated circuit (ASIC), or other electronic control circuit. The controller may be configured to receive signals from a temperature sensor for periodically determining the temperature measured by the temperature sensor. The controller may be configured to detect a user puff based on a drop in the measured temperature. The controller may comprise a memory device. The controller may store a counter of the number of detected puffs. This counter may relate to a specific placed aerosol generating product. The controller may be configured so that if the number of puffs reaches or exceeds a predetermined number of puffs, the controller may provide a warning signal to the user. The warning signal may be, for example, a tactile, audio, or optical signal. The controller may be configured so that if the number of puffs reaches or exceeds a predetermined number of puffs, it prevents the use of the device until the aerosol generating product is replaced. The prevention of use of the device may be carried out only after providing a warning signal. The specified number of puffs may refer to the average maximum number of puffs before the aerosol generated from a particular type of aerosol-forming substrate becomes unsatisfactory as a result of substrate degradation. The specified number of puffs may depend on the type of substrate for which the aerosol-generating device is designed for use. For example, if the aerosol-forming substrate is a solid substrate containing tobacco, the specified number of puffs before substrate degradation may be 14 puffs. The specified number of puffs may be determined or selected by the user. The specified number of puffs may be determined or selected by the user within a specified range.

The controller of the aerosol generating device may be configured to receive signals from a temperature sensor. The controller may be configured to repeatedly determine the temperature measured by the temperature sensor. The controller may be configured to detect a user's puff based on a drop in the measured temperature.

The controller may be configured to increase the supply of power to the heater assembly in response to the detected puff. For example, between puffs of the user, the heater assembly may be supplied with a first power to heat the substrate that forms the aerosol, but during the detected puff of the user or for a predetermined period of time after the detected puff of the user, a second power may be supplied that exceeds the first power.

As described previously, the aerosol generating device may comprise a power supply. The power supply may be a DC power supply having a DC supply voltage in the range of about 2.5 volts to about 4.5 volts and a DC supply current in the range of about 1 ampere to about 10 amperes (which corresponds to a DC power supply power in the range of about 2.5 watts to about 45 watts). The power supply may be a battery, such as a rechargeable lithium-ion battery. Alternatively, the power supply may be another type of charge storage device, such as a capacitor. The power supply may be rechargeable. The power supply may have a capacity that allows storing a sufficient amount of energy for one or more uses of the aerosol generating device. For example, the power supply may have sufficient capacity to ensure continuous aerosol generation for a period of about six minutes, which corresponds to the typical time required to smoke a conventional cigarette, or for a period that is a multiple of six minutes. In another example, the power supply may have sufficient capacity to enable a predetermined number of puffs or individual activations.

As described above, the power supply unit may be configured to supply alternating current. In this case, the aerosol generating device may advantageously comprise a DC/AC converter for converting direct current supplied by a DC power source into alternating current. The DC/AC converter may comprise a class D or class E power amplifier. The power supply unit may be configured to supply alternating current.

The power supply unit may be connected to the heater assembly. Advantageously, the power supply unit may be controlled by the controller. In particular, the controller may be designed so that when the puff counter stored in the memory device of the controller exceeds a specified number of puffs, the power supply to the heater assembly by the power supply unit is prevented.

The controller may comprise a bandpass filter. The bandpass filter may be configured to filter signals received from the temperature sensor. The bandpass filter may advantageously be configured to remove frequencies above 100 Hz from the signal. These frequencies may correspond to electrical noise. The bandpass filter may advantageously be configured to remove frequencies below 0.2 Hz from the signal. This may remove slow temperature changes from the signal that may not correspond to a tightening.

The heat transfer element may contain a thermal paste in contact with the temperature sensor. The thermal paste may advantageously provide contact between the heat transfer element and the temperature sensor. The thermal paste is advantageously electrically insulating. The thermal paste usually consists of a polymerizable liquid matrix and large volume fractions of an electrically insulating but thermally conductive filler.

The aerosol generating device may be an electric smoking device. The device may be a portable aerosol generating device. The aerosol generating device may be of a size comparable to a traditional cigar or cigarette. The aerosol generating device may have an overall length of 30 mm to 150 mm. The aerosol generating device may have an outside diameter of 5 mm to 30 mm.

In the second aspect, an aerosol generating system is proposed. The aerosol generating system may comprise an aerosol generating device according to the first aspect. The aerosol generating system may comprise a heater assembly for heating an aerosol forming substrate, which is located in a chamber.

The aerosol generating system may comprise an aerosol generating article. The aerosol generating article may comprise an aerosol forming substrate. The aerosol generating article may be housed in a chamber.

An aerosol-generating article may comprise a rod containing an aerosol-generating substrate. The rod may be surrounded by a wrapper. The aerosol-generating substrate may comprise tobacco.

In the context of this document, the term "aerosol-forming substrate" refers to a substrate that can release volatile compounds capable of forming an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. The aerosol-forming substrate may conveniently be a part of an aerosol-generating article or a smoking article.

The aerosol-forming substrate may be a solid aerosol-forming substrate. Alternatively, the aerosol-forming substrate may comprise both solid and liquid components. The aerosol-forming substrate may comprise a tobacco-containing material comprising volatile tobacco flavor compounds that are released from the substrate upon heating. Alternatively, the aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may further comprise an aerosol-forming agent that facilitates the formation of a dense and stable aerosol. Examples of suitable aerosol-forming agents include glycerol and propylene glycol.

In a particularly preferred embodiment, the aerosol-forming substrate comprises an assembled corrugated sheet of homogenized tobacco material. As used herein, the term "corrugated sheet" means a sheet having a plurality of substantially parallel ridges or corrugations.

The aerosol generating system may comprise a cartridge containing an aerosol forming substrate. The cartridge may be positioned in a chamber of the aerosol generating device. The aerosol forming substrate may be solid or liquid, or may comprise both solid and liquid components. Preferably, the aerosol forming substrate is a liquid.

The aerosol-forming substrate may comprise a material of plant origin. The aerosol-forming substrate may comprise tobacco. The aerosol-forming substrate may comprise a tobacco-containing material comprising volatile tobacco flavouring compounds that are released from the aerosol-forming substrate upon heating. Preferably, the aerosol-forming substrate may alternatively comprise a material that does not contain tobacco.

The cartridge may comprise a heating element, such as a resistive heating element or a current collecting element. The heating element may be fluid-permeable. In use, the vaporized aerosol-forming substrate may pass through the fluid-permeable element and subsequently cool to form an aerosol delivered to the user. Preferably, the cartridge comprises a cartridge body configured to come into contact with a chamber of the aerosol-generating device in use. The cartridge body may have an outer surface surrounding the aerosol-forming substrate contained in the cartridge. At least a portion of the outer surface may be formed by a fluid-permeable heating element. A portion of the outer surface formed by the fluid-permeable heating element may, in use, be in fluid communication with air flowing through an air flow channel of the aerosol-generating device when the cartridge is placed in the chamber of the aerosol-generating device. Therefore, during use, the vaporized substrate, which forms the aerosol, can pass from the cartridge into the air flow channel through the heating element and subsequently cool to form an aerosol that is delivered to the user.

In the context of this document, the term "fluid-permeable" element means an element through which a liquid or gas can pass. The heating element may have a plurality of openings formed therein to allow a fluid to pass through it. In particular, the heating element allows an aerosol-forming substrate, either in the gas phase or in both the gas and liquid phases, to pass through it.

In the third aspect, a method for detecting a user's puff through an aerosol-generating system is proposed. In particular, a method for detecting a user's puff on an aerosol-generating system is proposed according to the second aspect. For example, a user can puff on an aerosol-generating device. The user can puff through a mouthpiece of the aerosol-generating device. Alternatively, the user can puff through a mouthpiece of an aerosol-generating article that contains an aerosol-forming substrate located in the aerosol-generating device. The article can be located in a chamber of the aerosol-generating device.

The method may include placing an aerosol-forming substrate in a chamber of an aerosol-generating device. The method may include heating the placed aerosol-forming substrate. The method may include heating the heat-transfer element. The method may include receiving signals from a temperature sensor in a controller of the aerosol-generating device for repeatedly determining the measured temperature of the temperature sensor. The method may include detecting a user's puff based on a drop in the measured temperature.

The step of heating the heat transfer element may include supplying power to a heater assembly that includes a heating element used to heat the placed substrate that forms the aerosol. The aerosol generating device may preferably include the heater assembly. The aerosol generating device may preferably include the heating element.

Alternatively, the tightening sensor assembly may comprise a heating element for heating the heat transfer element. The step of heating the heat transfer element may include using the heating element of the tightening sensor assembly to heat the heat transfer element.

During use and between puffs, the heat transfer element may heat up to a temperature of at least 5, 10, 20, 40 or 80 degrees Celsius above the ambient temperature. The heat transfer element may heat up to a temperature of 5 degrees Celsius to 80 degrees Celsius above the ambient temperature.

The method may further include a filtering step for removing fluctuations in the temperature measurement results that are not indicative of the user's puff, using a bandpass filter.

In a fourth aspect, an aerosol generating device is provided for generating an aerosol from an aerosol-forming substrate, wherein the aerosol generating device comprises:

a device body that forms a chamber for placing an aerosol-forming substrate;

a heater assembly comprising a heating element for heating an aerosol-forming substrate, which is located in a chamber, for the purpose of generating an aerosol;

an air flow passage extending from an air inlet in the device housing through the chamber or in fluid communication with the chamber; and

a puff sensor assembly outside the chamber containing a temperature sensor, wherein a portion of the puff sensor assembly partially forms a channel for the air flow;

wherein the heating element is designed such that during use and between puffs the puff sensor assembly is heated to a temperature of at least 5 degrees Celsius above the ambient temperature.

The heating element may be designed so that during use and between puffs, the puff sensor assembly is heated to a temperature of at least 10, 20, 40 or 80 degrees Celsius above the ambient temperature. The heating element may be designed so that during use and between puffs, the puff sensor assembly is heated to a temperature of 5 degrees Celsius to 80 degrees Celsius above the ambient temperature.

The aerosol generating device can operate similarly to the aerosol generating device according to the first aspect in that the puff sensor assembly can be used to detect puffs based on a decrease in temperature detected by the puff sensor assembly. In particular, the puff sensor assembly can comprise a temperature sensor and a heat transfer element. The temperature sensor can be in contact with the heat transfer element. The first portion of the air flow channel can be at least partially formed by a wall of the air flow channel. The second portion of the air flow channel can be at least partially formed by the heat transfer element. In use, a decrease in the detected temperature of the heat transfer element can be detected by the temperature sensor after the user draws air through the air flow channel during use, as described in relation to the first aspect.

Heating the puff sensor assembly by at least 5 degrees Celsius above the ambient temperature advantageously increases the difference between the temperatures of the puff sensor assembly and the air passing through the air flow channel during use. This increases the cooling rate of the puff sensor assembly in response to a user's puff and, thus, advantageously leads to an even more pronounced or sharp drop in the temperature of the puff sensor assembly, which increases the speed and reliability of detecting a puff by the aerosol generating device. A large temperature difference can provide a greater cooling rate.

Since the heating of the puff sensor assembly is performed by the heater assembly containing the heating element for heating the aerosol-forming substrate, which is located in the chamber, and not by a specialized heater that is part of the puff sensor assembly, the power consumption of the puff sensor assembly itself is minimal. In addition, this puff sensor assembly can be manufactured more simply and inexpensively than a puff sensor assembly containing a heating element in addition to the heating element of the heater assembly.

The features described with respect to one aspect may be applied to other aspects of the present invention. In particular, the advantageous or optional features described with respect to the first aspect of the invention may be applied to the second, third and fourth aspects of the present invention. For example, the advantageous or optional features of the puff sensor assembly and, in particular, the heat transfer element of the puff sensor assembly described with respect to the aerosol generating device according to the first aspect may be applied to the aerosol generating device according to the fourth aspect.

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

EX1. An aerosol generating device for generating an aerosol from an aerosol forming substrate, wherein the aerosol generating device comprises:

a device body that forms a chamber for placing an aerosol-forming substrate;

an air flow passage extending from an air inlet in the device housing through the chamber or in fluid communication with the chamber; and

a tightening sensor assembly comprising a heat transfer element and a temperature sensor in contact with the heat transfer element;

wherein the first part of the air flow channel is at least partially formed by the wall of the air flow channel, and the second part of the air flow channel is at least partially formed by the heat transfer element, wherein the second part of the air flow channel is adjacent to the first part and is located outside the chamber.

EX2. An aerosol generating device according to example EX1, wherein the heat transfer element has a greater thermal conductivity than the wall of the air flow duct.

EX3. An aerosol generating device according to example EX1 or EX2, wherein the heat transfer element has a greater thermal conductivity than the wall of the air flow duct.

EX4. An aerosol generating device according to any of the previous examples, wherein the aerosol generating device comprises a heater assembly for heating an aerosol-forming substrate that is located in a chamber.

EX5. An aerosol generating device according to any of the examples EX1-EX3, wherein the chamber is configured to accommodate a cartridge containing an aerosol-forming substrate, wherein the cartridge contains a heater assembly.

EX6. An aerosol generating device according to any of the preceding examples, wherein in use air is drawn through the air flow channel by a user puffing on the aerosol generating device or on an aerosol generating article that is housed in the aerosol generating device and contains an aerosol forming substrate.

EX7. An aerosol generating device according to any of the preceding examples, wherein the heat transfer element has a thermal conductivity of at least 100 watts per meter-Kelvin.

EX8. An aerosol generating device according to any of the preceding examples, wherein the heat transfer element has a thermal conductivity of not more than 300 watts per meter-Kelvin.

EX9. An aerosol generating device according to any of the previous examples, wherein the heat transfer element has a thermal diffusivity of at least 50 square millimeters per second, preferably greater than 60, 70, 80 or 90 square millimeters per second.

EX10. An aerosol generating device according to any of the preceding examples, wherein, when the aerosol generating device is used, the heat transfer element is heated above the ambient temperature.

EX11. An aerosol generating device according to any of the preceding examples, wherein during use and between puffs, the heat transfer element is heated to a temperature of at least 5, 10, 20, 40 or 80 degrees Celsius above the ambient temperature.

EX12. An aerosol generating device as in EX10 or EX11, wherein heating occurs prior to the user's first puff.

EX13. An aerosol generating device according to any of the previous examples, which comprises a heater assembly comprising a heating element, wherein during use and between puffs, the heat transfer element is heated by the heating element to a temperature of at least 5, 10, 20, 40 or 80 degrees Celsius above the ambient temperature.

EX14. An aerosol generating device according to example EX13, wherein the distance between the heat transfer element and the heating element is less than 50 millimetres.

EX15. An aerosol generating device according to example EX13 or EX14, wherein the distance between the heater assembly and the heat transfer element is less than 10 millimeters or less than 5 millimeters.

EX16. An aerosol generating device according to any of EX13-EX15, wherein the heat transfer element is in contact with the heater assembly.

EX17. An aerosol generating device according to any one of examples EX13-EX16, wherein the puff sensor assembly comprises a heating element for heating the heat transfer element.

EX18. An aerosol generating device according to example EX17, wherein the temperature sensor is a heated thermistor.

EX19. An aerosol generating device according to any of the preceding examples, wherein the wall of the air flow channel is formed from a material containing plastics, such as thermoplastic materials.

EX20. An aerosol generating device according to example EX19, wherein the air flow wall is formed from polypropylene, polyetheretherketone (PEEK) or polyethylene.

EX21. An aerosol generating device according to any of the preceding examples, wherein the heat transfer element extends through the air flow channel for a distance less than 10 percent of its length.

EX22. An aerosol generating device according to any of the preceding examples, wherein the heat transfer element extends through the air flow channel for a distance of less than 5 percent of its length.

EX23. An aerosol generating device according to any of the preceding examples, wherein the heat transfer element extends along the length of the air flow channel at a distance of from 2 millimeters to 10 millimeters.

EX24. An aerosol generating device according to any of the preceding examples, wherein the heat transfer element is embedded in the wall of the air flow duct.

EX25. An aerosol generating device according to any of the preceding examples, wherein the heat transfer element is mounted by a press fit into the wall of the air flow duct.

EX26. An aerosol generating device according to example EX25, wherein the heat transfer element is mounted by means of a press fit into a portion of the wall of the air flow channel which forms a channel with a diameter equal to or, preferably, slightly smaller than that of the heat transfer element.

EX27. An aerosol generating device according to any of the preceding examples, wherein the air flow channel formed by the wall of the air flow channel narrows upstream of the heat transfer element.

EX28. An aerosol generating device according to any of the preceding examples, wherein the wall of the air flow channel comprises an opening.

EX29. An aerosol generating device according to example EX28, wherein the opening is adjacent to the heat transfer element.

EX30. An aerosol generating device according to example EX28 or EX29, wherein the temperature sensor is placed through the opening so that it is in contact with the heat transfer element.

EX31. An aerosol generating device according to any of the preceding examples, wherein the thickness of the heat transfer element is from 0.1 millimeters to 2 millimeters.

EX32. An aerosol generating device according to any of the preceding examples, wherein the thickness of the heat transfer element is from 0.1 millimeter to 0.5 millimeter.

EX33. An aerosol generating device according to any of the previous examples, wherein the first surface of the heat transfer element at least partially forms a second portion of the air flow channel.

EX34. An aerosol generating device according to example EX33, wherein the temperature sensor is in contact with a second surface of the heat transfer element, which is different from the first surface of the heat transfer element such that the heat transfer element is located between the air flow channel and the temperature sensor.

EX35. An aerosol generating device according to example EX33 or EX34, wherein the first surface is opposite the second surface.

EX36. An aerosol generating device according to any of EX33-EX35, wherein the area of the first surface of the heat transfer element is at least 1, 2, 5, 10 or 20 square millimeters.

EX37. An aerosol generating device according to any of the preceding examples, wherein the heat transfer element comprises or consists of a metal.

EX38. An aerosol generating device according to any of the preceding examples, wherein the heat transfer element comprises or consists of aluminum.

EX39. An aerosol generating device according to any of the preceding examples, wherein the heat transfer element is in the form of a sheet having a length, a width, and a thickness.

EX40. An aerosol generating device according to any of the examples EX1-EX38, wherein the heat transfer element is tubular.

EX41. An aerosol generating device according to any of the preceding examples, wherein the aerosol generating device comprises a mouthpiece.

EX42. An aerosol generating device according to any of the examples EX1-EX40, wherein the aerosol generating device is configured to accommodate an aerosol generating article, wherein the aerosol generating article comprises an aerosol forming substrate at or near a distal end, and the aerosol generating article comprises a mouthpiece at a proximal end.

EX43. An aerosol generating device according to any of the preceding examples, wherein the heat transfer element partially defines an air flow channel upstream of the heater assembly.

EX44. An aerosol generating device according to any of the preceding examples, wherein the aerosol generating device comprises a heater assembly comprising a heating element, wherein the heating element surrounds a chamber.

EX45. An aerosol generating device according to example EX44, wherein the housing of the device forming part of the chamber that is surrounded by the heating element is made of a metal such as stainless steel or ceramic.

EX46. An aerosol generating device according to any of the examples EX1-EX43, wherein the heating element is enclosed in the housing of the device such that the heating element forms part of the chamber.

EX47. An aerosol generating device according to any of the preceding examples, further comprising a controller.

EX48. An aerosol generating device according to example EX47, wherein the controller comprises a bandpass filter configured to filter signals received from the temperature sensor.

EX49. An aerosol generating device according to example EX48, wherein the bandpass filter is configured to remove frequencies above 100 Hz from the signal.

EX50. An aerosol generating device according to example EX48 or EX49, wherein the bandpass filter is configured to remove signal frequencies below 0.2 Hz.

EX51. An aerosol generating device according to any of the preceding examples, wherein the heat transfer element comprises thermal paste in contact with the temperature sensor.

EX52. An aerosol generating device according to any of the preceding examples, which is an electric smoking device.

EX53. An aerosol generating device according to any of the preceding examples, wherein the aerosol generating device is a portable aerosol generating device.

EX54. An aerosol generating system that comprises an aerosol generating device according to any of the preceding examples and an aerosol generating article that comprises an aerosol forming substrate, wherein the aerosol generating article is disposed in a chamber.

EX55. An aerosol generating system according to example EX57, wherein the system comprises an aerosol generating article.

EX56. An aerosol generating system according to example EX58, wherein the aerosol generating article comprises an aerosol forming substrate.

EX57. An aerosol generating system according to example EX55 or EX56, wherein the aerosol generating article comprises a rod containing an aerosol forming substrate.

EX58. An aerosol generating system according to EX57, wherein the rod is surrounded by a wrapper.

EX59. An aerosol generating system according to example EX54, wherein the aerosol generating system comprises a cartridge containing an aerosol forming substrate.

EX60. An aerosol generating system according to example EX59, wherein the cartridge is disposed in a chamber of the aerosol generating device.

EX61. An aerosol generating system according to example EX62 or EX63, wherein the aerosol forming substrate is a solid or a liquid, or contains both solid and liquid components.

EX62. An aerosol generating system according to example EX59 or EX60, wherein the aerosol forming substrate is a liquid.

EX63. An aerosol generating system according to any of EX59-EX62, wherein the cartridge comprises a heating element, such as a resistive heating element or a current collecting element.

EX64. An aerosol generating system according to EX63, wherein the heating element is permeable to the fluid.

EX65. A method for detecting a user's puff on an aerosol generating system according to any one of EX54-EX64, wherein the method comprises:

placing an aerosol-forming substrate in the chamber of an aerosol-generating device;

heating of the placed substrate, forming an aerosol;

heating of the heat transfer element;

receiving signals from the temperature sensor by the controller of the aerosol generating device to repeatedly determine the measured temperature of the temperature sensor; and

detecting a user's puff based on a drop in measured temperature.

EX66. The method according to example EX65, wherein the step of heating the heat transfer element includes supplying power to a heater assembly that contains a heating element used to heat a placed aerosol-forming substrate.

EX67. The method according to example EX65, wherein the tightening sensor assembly may comprise a heating element for heating the heat transfer element, and the step of heating the heat transfer element includes using the heating element of the tightening sensor assembly to heat the transfer element.

EX68. The method according to any of the examples EX65-EX67, wherein during use and between puffs, the heat transfer element is heated to a temperature of at least 5, 10, 20, 40 or 80 degrees Celsius above the ambient temperature.

EX69. The method according to any one of examples EX65-EX68, further comprising a filtering step for removing fluctuations in the temperature measurement results that are not indicators of the user's puff, using a bandpass filter.

EX70. An aerosol generating device for generating an aerosol from an aerosol forming substrate, the aerosol generating device comprising:

a device body that forms a chamber for placing an aerosol-forming substrate;

a heater assembly comprising a heating element for heating an aerosol-forming substrate, which is located in a chamber, for the purpose of generating an aerosol;

an air flow passage extending from an air inlet in the device housing through the chamber or in fluid communication with the chamber; and

a puff sensor assembly outside the chamber containing a temperature sensor, wherein a portion of the puff sensor assembly partially forms a channel for the air flow;

wherein the heating element is designed such that during use and between puffs the puff sensor assembly is heated to a temperature of at least 5, 10, 20, 40 or 80 degrees Celsius above the ambient temperature.

Features described with respect to one example or embodiment may also be applied to other examples and embodiments.

The examples will now be further described with reference to figures, where:

Fig. 1 shows a schematic cross-sectional view of a first aerosol generating device that comprises a puff sensor assembly and an aerosol generating article that is housed in a chamber of the device;

Fig. 2 shows a cross-sectional view of the puff sensor assembly and the air flow channel of the aerosol generating device according to Fig. 1;

Fig. 3 shows a horizontal section through the puff sensor assembly and the air flow channel according to Fig. 2;

Fig. 4 shows a section of the wall of the air flow channel of the aerosol generating device according to Fig. 1 with a heat transfer element before press fitting into the wall of the air flow channel;

Fig. 5 shows a similar section of the air flow channel wall after press fitting of the heat transfer element and with the temperature sensor in place;

Fig. 6 shows a method for detecting a user's puff on the aerosol generating device according to Fig. 1;

Fig. 7 shows a schematic cross-sectional view of a second aerosol generating device that includes an assembled induction heater;

Fig. 8 shows a schematic cross-sectional view of a third aerosol generating device that includes a heater assembly that includes a heating element that extends upstream of the chamber for contacting the puff sensor assembly; and

Fig. 9 shows a schematic cross-sectional view of a fourth aerosol generating device that comprises a chamber configured to accommodate a cartridge containing an aerosol-forming substrate and a cartridge positioned in the chamber.

Fig. 1 shows a schematic representation of a sectional view of a first aerosol generating device 100. The aerosol generating device 100 comprises a chamber 10, which is formed by a housing 11 of the device. The chamber 10 is tubular, made of stainless steel and comprises a base 12 at the end located upstream of the flow. The chamber 10 is designed with the possibility of accommodating an aerosol generating article 200.

An aerosol-generating article 200 is placed in a chamber 10. The aerosol-generating article 200 contains an aerosol-generating substrate 202. The aerosol-generating substrate is a solid tobacco-containing substrate. In particular, the aerosol-generating substrate is an assembled sheet of homogenized tobacco. As shown in Fig. 1, the aerosol-generating article and the chamber are designed so that, when the aerosol-generating article is placed in the chamber, the mouth end of the aerosol-generating article 200 projects from the chamber 10 and from the aerosol-generating device. This mouth end forms a mouthpiece 204, through which the user of the aerosol-generating device can puff during use.

The aerosol generating device 100 together with the aerosol generating article 200 may be referred to as an aerosol generating system.

The aerosol generating device 100 comprises a heater assembly comprising a heating element 110. The heating element 110 surrounds the chamber 10 along a portion of the chamber in which the aerosol generating substrate 202 of the aerosol generating article 200 is placed. In an alternative embodiment, the heating element 110 forms a portion of the chamber wall that forms a portion of the chamber in which the aerosol generating substrate is placed. The heating element 110 is a resistive heating element.

The air flow channel 120 extends from the air inlet 122 of the aerosol generating device 100. Earlier in the flow direction relative to the chamber, the air flow channel 120 is formed mainly by the wall 124 of the air flow channel. Further in the flow direction relative to the wall 124 of the air flow channel, the air flow channel 120 passes through the air inlet formed in the base 12 of the chamber. The air flow channel 120 then passes through the chamber 10.

The aerosol generating device 100 further comprises a puff sensor assembly. The puff sensor assembly comprises a heat transfer element 132. The heat transfer element 132 is circular. The inner, or first, surface of the heat transfer element 132 forms a portion of the air flow channel 120 upstream of the flow relative to the chamber and the heater assembly. The portion of the air flow channel 120 formed by the heat transfer element 132 is adjacent to the portions of the air flow channel formed by the wall 124 of the air flow channel, as shown in Fig. 1. The heat transfer element 132 has a thickness of 0.8 millimeters, a length of 5 millimeters and an inner circumference of 30 mm. The heat transfer element 132 is made of aluminum. The heat transfer element is installed using a press fit in the wall 124 of the air flow channel.

The puff sensor assembly and the wall 124 of the air flow channel are shown more clearly in Fig. 2 and 3. Fig. 2 shows a top sectional view of the puff sensor assembly and the wall 124 of the air flow channel of the device. Fig. 3 shows a horizontal section through the puff sensor assembly and the wall 124 of the air flow channel. Fig. 3 shows only a portion of the air flow channel. The full extent of the wall 124 of the air flow channel upstream of the heat transfer element or the chamber 10 downstream of the heat transfer element is not shown.

The wall 124 of the air flow channel is made of polyetheretherketone (PEEK). The thermal conductivity and thermal conductivity of PEEK are significantly lower than those of aluminum. Thus, the heat transfer element 132 has a thermal conductivity and thermal diffusivity greater than the corresponding parameters of the wall 124 of the air flow channel.

The tightening sensor assembly additionally comprises a temperature sensor 134, which is in contact with the heat-transfer element 132. In particular, the temperature sensor 134 is in contact with the outer, or second, surface of the tubular heat-transfer element 132. This second surface is opposite the first surface, and thus the heat-transfer element is located between the air flow channel and the temperature sensor. Therefore, the heat-transfer element 132 protects the temperature sensor 134 from any dust and dirt passing through the air flow channel or in this channel.

The temperature sensor 134 comprises a housing 136, electrical connections 138 and a measuring element 138. The temperature sensor is a temperature sensor with a negative temperature coefficient of resistance (NTC). This is shown more clearly in Fig. 3. The temperature sensor 134 is connected to a controller 140 of the aerosol generating device.

Fig. 4 and 5 show how the heat transfer element 132 is installed by means of a press fit in the wall 124 of the air flow duct. Fig. 4 shows a section of the wall 124 of the air flow duct with the heat transfer element 132 ready for a press fit. Fig. 5 shows a similar section of the wall 124 of the air flow duct after a press fit of the heat transfer element 132 and with the temperature sensor 134 in place.

Fig. 4 and 5 show how the upstream portion 127 of the air flow channel wall 124 forms a narrowing air flow channel 122 with a diameter that decreases in a direction further downstream. The narrowing of the air flow channel 122 ends with a stepwise increase 129 in the diameter of the channel formed by the inner surface of the air flow channel wall 124. The inner surface of the downstream portion 131 of the air flow channel wall 124 further downstream relative to the stepwise increase in diameter forms a channel having an inner surface with a diameter that remains constant.

The diameter of the air flow channel formed by the downstream portion 131 of the air flow channel wall 124 is somewhat smaller than the diameter of the tubular heat transfer element 132. Thus, when the heat transfer element 132 is inserted into the downstream portion 131 in the direction shown by the arrow in Fig. 4, the air flow channel wall 124 must deform somewhat to accommodate the heat transfer element. The air flow channel 132 formed from PEEK is flexible and elastic enough to allow this deformation and to press on the inserted heat transfer element 132, holding it in place. When manufacturing the device, the heat transfer element 132 is pushed into the downstream portion of the air flow channel wall 124 so that it adjoins a step formed by a step change in the diameter of the inner surface of the air flow channel wall 124.

The wall 124 of the air flow channel additionally comprises an opening 125 in the part located further along the flow path. This opening 125 is intended for accommodating the temperature sensor 134, and thus the measuring element 138 of the temperature sensor 134 is in contact with the heat transfer element 132.

The aerosol generating device 100 further comprises a power supply unit 142 in the form of a rechargeable battery for supplying power to the heating element 20 controlled by the controller 140. The power supply unit is connected to the controller and the heating element 110 by means of electrical wires and connections that are not shown in the figures. The aerosol generating device may comprise additional elements that are not shown in the figures, such as a button for activating the aerosol generating device.

A method for detecting a puff of a user on an aerosol generating device 100 is described with respect to Fig. 6. Fig. 6 is a flow chart showing the steps of the method. In step 502, a user of the aerosol generating device 100 inserts an aerosol generating substrate 202 into a chamber of the aerosol generating device 100. As described above, the aerosol generating substrate 202 is contained in an aerosol generating article 200, so step 502 includes inserting the article 200 into a chamber 10 of the device, and thus the aerosol generating substrate 202 is located in a part of the chamber 10 surrounded by a heating element 110, as shown in Fig. 1.

In step 504, the placed aerosol-forming substrate 102 is heated. This step follows the activation of the aerosol-generating device by the user, for example, using a button or switch on the aerosol-generating device. This causes the controller 140 to supply power from the power supply unit 142 to the heating element 110 so that an electric current flows through the heating element 110, causing the heating element 110 to heat up. Heat can be transferred to the aerosol-forming substrate so that volatile compounds evaporate from the aerosol-forming substrate.

At step 506, the heat transfer element is heated. In the aerosol generating device 100, this is achieved by radiating heat from the heating element 110 and by conducting heat through a portion of the wall 124 of the air flow channel that separates the heat transfer element 132 from the heating element 110 (after the device is turned on). Heating the heat transfer element by the heating element 110 is particularly effective due to the fact that the distance between the heat transfer element and the heating element 110 is 5 millimeters.

In some embodiments, the heat transfer element 132 is additionally or alternatively itself equipped with a temperature sensor 134. For example, the temperature sensor can be a self-heating thermistor connected to a power supply unit 142, which can be configured to pass a current through the thermistor, causing it to heat up. This heat can then be supplied to the heat transfer element 132.

In step 508, the controller 140 receives signals from the temperature sensor 134. The controller 140 can then determine the temperature measured by the temperature sensor based on its signal. In particular, when the temperature sensor 134 is a thermistor, the signal can relate to the resistance of the thermistor. The resistance of the thermistor is highly dependent on the temperature as the temperature of the thermistor increases, which leads to either an increase or a decrease in resistance depending on whether the thermistor has a positive or negative temperature coefficient of resistance. Therefore, in such embodiments, the controller 140 can receive a signal related to the resistance of the thermistor, which is used to conclude the temperature of the thermistor.

At step 510, a user puff is detected based on a drop in the measured temperature using the controller 140, wherein the temperature is repeatedly determined in the same way as at step 508.

Before the device is turned on, the temperature measured by the temperature sensor 134 will be low. It will be equal to or close to room temperature if the device has not been used recently. After the device is turned on, the measured temperature will quickly increase as the heat transfer element 132 is heated by the heating element 110. When the device reaches the operating temperature, the temperature measured by the temperature sensor 134 will become stationary as the heat transfer element 132 reaches a steady state.

When using the aerosol generating device 100, the user will puff through the mouthpiece 204 of the placed aerosol generating article 200, which leads to air being drawn through the air flow channel 120 in the direction of the user's mouth. During the puff, air will be drawn from outside the aerosol generating device into the air flow channel 120 through the air inlet 122. The air will be drawn through parts of the air flow channel formed by the wall 124 of the air flow channel and the heat transfer element 132, and through the air inlet formed in the base 12 of the chamber 10, into the chamber. Since the aerosol generating article 200 is placed in the chamber, the air drawn into the chamber will enter the aerosol generating article 200 at its distal end. In this way, the air passes through the substrate 202 forming the aerosol. Thus, the volatile compounds generated by heating the substrate 202 will be entrained in the air. As the air continues to move toward the mouth end of the aerosol-generating article 200, the volatile compounds are cooled to form an aerosol. The direction of air flow through the aerosol-generating device and the aerosol-generating article is shown in Fig. 1 by a dashed arrow.

During the puff, the air drawn through the air flow channel 120 will cool the warm inner surface of the air flow channel 120. The aluminum of the heat transfer element 132 has a much higher thermal conductivity and thermal diffusivity than the PEEK of the wall 124 of the air flow channel. Therefore, in response to the user's puff, the heat transfer element 132 cools faster than the wall 124 of the air flow channel. The cooling also spreads quickly through the heat transfer element 132, and thus the drop in the measured temperature is quickly detected by the temperature sensor 134 and the controller. The heat transfer element 132 has a size of 0.5 millimeters in thickness and such a length that it extends a distance of 4 millimeters along the length of the air flow channel. A tubular heat transfer element having such dimensions advantageously has a relatively small mass and a relatively large ratio of the surface area to mass or the ratio of the surface area to volume. Therefore, during a puff, there is a pronounced and rapid drop in temperature of the heat transfer element 132, measured by the temperature sensor 134. The controller 140 uses these drops in temperature to reliably and accurately detect the user's puff.

The controller 140 comprises a memory device, which is not shown, in which a counter of the number of detected puffs is stored. Each time a puff is detected, the count is increased by one. The memory device also stores a predetermined value representing the maximum number of times the user can puff through the aerosol-forming substrate 202 before its degradation. The controller 140 is designed so that when the number of puffs reaches or exceeds the counter's predetermined value, the controller prevents the use of the device until the aerosol-generating article is replaced.

The controller 140 includes a bandpass filter, not shown, for filtering signals received from the temperature sensor. The bandpass filter removes frequencies from the signal above 100 Hz and frequencies of the signal below 0.2 Hz.

Fig. 7 shows a schematic representation of a sectional view of a second aerosol generating device 400. The second aerosol generating device 400 operates similarly to the first aerosol generating device 100. The same numbering is used for the features of the second aerosol generating device 400 that correspond to the features of the first aerosol generating device 100. For example, the puff sensor assemblies in both devices are the same.

The difference between the second aerosol generating device 400 and the first aerosol generating device 100 is that the second aerosol generating device 400 comprises an induction heater assembly comprising a current collecting element 402 and an induction coil 404. The current collecting element 402 surrounds the chamber 10 along a portion of the chamber in which the aerosol generating substrate 202 of the aerosol generating article 200 is placed. In an alternative embodiment, the current collecting element 402 forms a portion of the chamber wall that forms a portion of the chamber in which the aerosol generating substrate is placed.

The induction coil 404 surrounds the current-collecting element. The induction coil 404 in this embodiment is a helical induction coil.

In the second aerosol generating device 400, the power supply unit 142 is configured to supply alternating current to the induction coil 404 when the device is used. The alternating current is a high-frequency alternating current. This results in heating of the current receiving element 402, and this heat is transferred to the placed substrate 202 forming the aerosol, causing the generation of volatile compounds in the same way as in the case of the resistive heating element 110 described above with respect to step 504 according to Fig. 6.

Fig. 8 shows a schematic cross-sectional view of the third aerosol generating device 500. Again, the third aerosol generating device 500 operates in a similar manner to the first aerosol generating device 100. The same numbering is used for the features of the third aerosol generating device 500 that correspond to the features of the first aerosol generating device 100.

Like the first aerosol generating device 100, the third aerosol generating device 500 comprises a resistive heater assembly. However, in the third aerosol generating device 500, the resistive heating element 502 does not simply surround the chamber. The resistive heating element 502 also extends behind the chamber, upstream of the base 12. The heat transfer element 504 is identical to the heat transfer element 132 in terms of physical properties, such as the properties and size of the material. However, in the third aerosol generating device 500, the heat transfer element 504 is installed in a certain position immediately upstream of the base 12 of the chamber 10. Thus, the resistive heating element 502 is in contact with the heat transfer element 504. When using the aerosol generating device 500, the heat transfer element 504 is heated by the resistive heating element 502.

In some embodiments, the resistive heater assembly may be replaced with an induction heater assembly in which the susceptor element extends upstream of the chamber to contact the heat transfer element.

Fig. 9 is a schematic illustration of a sectional view of a fourth aerosol generating device 600. The fourth aerosol generating device 600 comprises a chamber 610 configured to receive a cartridge containing an aerosol generating substrate, rather than an aerosol generating article. A cartridge 700 is received in the aerosol generating device 600. The cartridge 700 comprises a cartridge body 704 that has an outer surface surrounding and containing a liquid aerosol generating substrate 702. The liquid substrate is retained in a capillary material, which is not shown, in some embodiments. As shown in Fig. 9, when received in the chamber, the cartridge 700 is completely contained in the aerosol generating device 600. For inserting and removing the cartridge 700 from the chamber 610, the aerosol generating device 600 comprises a means for accessing the chamber, which is not shown. For example, the upper part of the aerosol generating device 600 can be hinged, which allows it to be opened to access the chamber and closed to close the chamber, and the cartridge 700 is retained in the chamber 610.

The fourth aerosol generating device 600 comprises an air flow channel 620 extending from an air inlet 622 of the aerosol generating device 600. The air flow channel 620 is mainly formed by a wall 624 of the air flow channel. An opening 625 is provided in the wall 624 of the air flow channel corresponding to the chamber 610. After passing the opening 625, the air flow channel 620 passes through a mouthpiece 623, which, unlike the previously described aerosol generating devices, is part of the aerosol generating device 600. In use, the user draws in through the mouthpiece 623 when taking a puff.

The aerosol generating device 600 further comprises a puff sensor assembly. The puff sensor assembly comprises a heat transfer element 632 and a temperature sensor 634. The puff sensor assembly is similar to the sensor shown in Fig. 1. For example, the heat transfer element 632 is round and forms part of the air flow channel 620.

Unlike the first, second and third aerosol generating devices 100, 400, 500, the fourth aerosol generating device 600 does not comprise a heater assembly. Instead, the cartridge 700 comprises a heater assembly comprising a resistive heating element 706. The heating element 706 is permeable to the fluid and forms part of the outer surface of the cartridge body 704. As shown in Fig. 9, when the cartridge 700 is placed in the chamber 610, the fluid-permeable heating element forms part of the air flow channel 620. Therefore, the heating element 606 is in fluid communication with the air flowing through the air flow channel of the aerosol generating device.

The aerosol generating device 600 further comprises a power supply unit 642 in the form of a rechargeable battery for supplying power to the heating element 606 controlled by the controller 640. The power supply unit is connected to the controller by means of electrical wires and connections that are not shown in the figures. In addition, the aerosol generating device and the cartridge comprise corresponding electrical connections that are not shown for electrically connecting the cartridge 700 to the device when the cartridge is placed in the chamber. Suitable wires that are not shown connect the power supply unit 642 to electrical connectors of the device. Suitable wires that are not shown connect the electrical connections of the cartridge to the heating element 606. In this way, when the cartridge is placed in the chamber, power can be supplied to the heating element 606 from the power supply unit 642.

In use, power is supplied to the heating element 606. The power heats the aerosol-forming substrate 702, and thus the aerosol-forming substrate at least partially evaporates. The evaporated aerosol-forming substrate passes from the cartridge 700 into the air flow channel 620 through the heating element 606 and is subsequently cooled in the air flow channel to form an aerosol that is delivered to the user.

Except for the above-described differences, the fourth aerosol generating device 600 operates in the same manner as described above with respect to the first aerosol generating device 100.

Claims (26)

1. An aerosol generating device for generating an aerosol from an aerosol forming substrate, wherein the aerosol generating device comprises: a device body that forms a chamber for placing an aerosol-forming substrate; an air flow passage extending from an air inlet in the device housing and through or in fluid communication with the chamber; and a tightening sensor assembly comprising a heat transfer element and a temperature sensor in contact with the heat transfer element; wherein the first part of the air flow channel is at least partially formed by the wall of the air flow channel, and the second part of the air flow channel is at least partially formed by said heat transfer element, wherein the second part of the air flow channel is adjacent to the first part and is located outside the chamber; and wherein at least one of the thermal conductivity or thermal diffusivity of the heat transfer element is greater than the corresponding thermal conductivity or thermal diffusivity of the wall of the air flow channel. 2. An aerosol generating device according to claim 1, characterized in that it contains a heater assembly for heating an aerosol-forming substrate, which is placed in a chamber. 3. An aerosol generating device according to claim 1 or 2, characterized in that the heat transfer element has a thermal conductivity of 100 watts per meter Kelvin to 300 watts per meter Kelvin. 4. An aerosol generating device according to any of the preceding paragraphs, characterized in that the heat transfer element has a thermal conductivity of more than 50 square millimeters per second. 5. An aerosol generating device according to any one of claims 2 to 4, characterized in that the heater assembly comprises a heating element, and during use and between puffs the heat transfer element is heated by the heating element to a temperature of at least 5, 10, 20, 40 or 80 degrees Celsius above the ambient temperature. 6. An aerosol generating device according to paragraph 5, characterized in that the distance between the heat transfer element and the heating element is less than 50 millimeters. 7. An aerosol generating device according to any of the preceding paragraphs, characterized in that the thickness of the heat transfer element is from 0.1 millimeter to 0.5 millimeter. 8. An aerosol generating device according to any of the preceding claims, characterized in that the surface area of the part of the heat transfer element partially forming the air flow channel is at least 1, 2, 5, 10 or 20 square millimeters. 9. An aerosol generating device according to any of the preceding claims, characterized in that the heat transfer element is installed by means of a press fit into the wall of the air flow channel. 10. An aerosol generating device according to any of the preceding claims, characterized in that the wall of the air flow channel contains an opening adjacent to the heat transfer element. 11. An aerosol generating device according to claim 10, characterized in that the temperature sensor is placed through the opening so that it is in contact with the heat transfer element. 12. An aerosol generating device according to any of the preceding paragraphs, characterized in that the heat transfer element is tubular. 13. An aerosol generating device according to any one of the preceding claims, characterized in that the first surface of the heat transfer element at least partially forms a second part of the air flow channel, and the temperature sensor is in contact with the second surface of the heat transfer element, wherein the first surface is different from the second surface. 14. An aerosol generating device according to any one of the preceding claims, characterized in that it comprises a heater assembly, and wherein the second part of the air flow channel is located upstream of the heater assembly. 15. An aerosol generating system comprising an aerosol generating device according to any of the preceding claims and an aerosol generating article comprising an aerosol forming substrate, wherein the aerosol generating article is disposed in a chamber. 16. A method for detecting a user's puff on an aerosol generating system according to claim 15, wherein the method comprises: placing an aerosol-forming substrate in the chamber of an aerosol-generating device; heating of the placed substrate, forming an aerosol; heating of the heat transfer element; receiving signals from the temperature sensor by the controller of the aerosol generating device to repeatedly determine the measured temperature of the temperature sensor; and detecting a user's puff based on a drop in measured temperature.