KR20260003038A - Aerosol generating device that detects airflow - Google Patents

Abstract

An aerosol generating device (1, 501, 601) for generating an aerosol from an aerosol forming substrate (201) defines a cavity (2) for accommodating at least a portion of the aerosol forming substrate, and an airflow path (6, 506) upstream of the cavity through which a user can draw air when using the device. The airflow path connects the cavity to an external environment. A pressure sensor (7, 507) is positioned in communication with the airflow path upstream of the cavity, and the device is configured to detect one or more user puffs taken during use of the device using a signal from the pressure sensor. Restricting the airflow path can enhance the pressure drop associated with the user puff, thereby amplifying the sensitivity of the pressure sensor.

Description

Aerosol generating device that detects airflow

The present disclosure relates to an aerosol generating device. The present disclosure also relates to an aerosol generating system including an aerosol generating device and a method for controlling the aerosol generating device.

Some known aerosol-generating systems include an aerosol-generating device and an aerosol-generating article comprising an aerosol-forming substrate. In use, the aerosol-generating device heats the aerosol-forming substrate of the aerosol-generating article to form an aerosol.

Aerosol-generating articles are known in the art in which the aerosol-forming substrate, such as a tobacco-containing substrate, is heated rather than combusted. Typically, in such heated aerosol-generating articles, the aerosol is generated by heat transfer from a heat source to the aerosol-forming substrate.

Electrically actuated aerosol-generating devices, such as small aerosol-generating devices, may be used with these aerosol-generating articles. These electrically actuated aerosol-generating devices may include a heating element configured to heat the aerosol-forming substrate to temperatures of several hundred degrees Celsius. This releases volatile compounds from the aerosol-forming substrate into air drawn through the aerosol-generating article. As the released compounds cool, they condense or nucleate to form an aerosol.

Examples of aerosol-generating devices for consuming aerosol-generating articles are disclosed in the art. These devices include, for example, electrically heated aerosol-generating devices in which the aerosol is generated by heat transfer from one or more electrical heating elements of the aerosol-generating device to the aerosol-generating element of the aerosol-generating article. To this end, the aerosol-generating article may be partially accommodated within a heating cavity of the aerosol-generating device, such that the upstream end of the aerosol-generating article is inserted into the cavity, while the downstream end of the aerosol-generating article protrudes outside the cavity.

For example, an electrically heated aerosol-generating device has been proposed that includes an internal heater blade adapted to be inserted within an aerosol-generating substrate when an aerosol-generating article is received within the heating cavity. Alternatively, heating of the aerosol-generating substrate has been achieved using external heating, such as by a tubular heater element that at least partially defines a heating cavity into which the aerosol-generating article is inserted, or by a tubular heater element that is otherwise coupled to a tubular element defining a heating cavity.

Inductively heated aerosol-generating articles have also been proposed, for example, in WO 2015/176898. These aerosol-generating articles comprise an aerosol-generating substrate, such as a tobacco-containing substrate, and an aerosol-generating element comprising a susceptor arranged within the aerosol-generating substrate. A functional connection between the susceptor and the inductive heater element of the aerosol-generating device is achieved when the aerosol-generating article is partially accommodated within the heating cavity of the aerosol-generating device.

The solid aerosol-generating substrate needs to be heated to a temperature sufficient to facilitate the extraction of aerosol species (e.g., nicotine and glycerin). Conventional heaters are typically configured to supply heat so that the solid aerosol-generating substrate is exposed to temperatures within this range throughout. However, such heating settings may have the disadvantage of less than optimal battery efficiency. Furthermore, such heating settings may limit the use of the solid aerosol-generating substrate to a predetermined finite number of puffs or a predetermined time (minutes). Furthermore, maintaining the solid aerosol-generating substrate at a temperature sufficient to facilitate the extraction of aerosol species between puffs may also undesirably increase the risk of generating hazardous and potentially hazardous constituents (HPHCs).

It would be desirable to provide an aerosol generating device configured to at least partially address at least one of the aforementioned disadvantages.

The present invention relates to an aerosol-generating device configured to generate an aerosol from an aerosol-forming substrate, for example, during a use session. The device may be configured to heat the aerosol-forming substrate to an ambient temperature or a maintenance temperature during the use session. The device may be configured to increase the temperature of the aerosol-forming substrate from the ambient temperature to, for example, an operating temperature when a user takes a puff. For example, the device may be configured to provide a heat boost to the aerosol-forming substrate during a user puff taken during a user session. This configuration allows the aerosol-forming substrate to be heated to a first temperature, for example, an ambient temperature that is at or slightly below the temperature required to form an aerosol, and then heated to an increased temperature, for example, an operating temperature, above the temperature required to form an aerosol during a user puff.

By selecting an appropriate ambient temperature, the aerosol-forming substrate can be heated almost instantaneously to its operating temperature when additional thermal energy is applied to the substrate. The temperature can then be cooled to ambient temperature after the user puffs.

The combination of heating to ambient temperature and rapid temperature increase to operating temperature during puffing allows for efficient harvesting of desired components of the aerosol-forming substrate, such as nicotine, flavoring ingredients, and aerosol-forming agents such as glycerin, without excessively overheating the substrate. The formation of undesirable aerosol components can be reduced, and optimal harvesting of desired components can be achieved.

An aerosol-generating device may define a cavity for receiving at least a portion of an aerosol-forming substrate. The aerosol-generating device may define an airflow path upstream of the cavity through which air can be drawn when a user uses the device. The airflow path may connect the cavity to an external environment. The device may include a flow detection means, for example, a pressure sensor, positioned in communication with the airflow path upstream of the cavity. The device may be configured to detect one or more user puffs taken during a use session using a signal from the flow detection means, for example, the pressure sensor.

According to an aspect of the present invention, an aerosol-generating device is provided that is configured to generate an aerosol from an aerosol-forming substrate. The device defines a cavity for receiving at least a portion of the aerosol-forming substrate, and an airflow path upstream of the cavity through which air can be drawn when a user uses the device, the airflow path connecting the cavity to an external environment. The device further comprises a flow detector or flow detection means, for example, comprising a pressure sensor, positioned in communication with the airflow path upstream of the cavity. The device is configured to detect one or more user puffs taken during a use session using a signal from the flow detector or flow detection means, for example, the pressure sensor.

It is noted that the cavity may be generally referred to as a chamber, and the terms cavity and chamber may be used interchangeably herein to mean a portion of a device for containing at least a portion of an aerosol-forming substrate such that the substrate is heated to generate an aerosol.

Preferably, the airflow path upstream of the cavity acts as or includes a flow restrictor. For example, the flow restrictor may include a mechanical element, such as an orifice plate, positioned within the airflow path. As a further example, a portion of the airflow path may be narrow enough to act as a flow restrictor. The flow restriction may increase the velocity of air drawn through the airflow path and create a pressure drop. The flow restriction may enhance the pressure drop created when a user draws air through the airflow path. Accordingly, the flow restriction may increase the sensitivity of puff detection. For example, the increased pressure drop associated with a flow restriction within a portion of the airflow path may improve the ability of a pressure sensor to accurately detect a user puff.

The flow restrictor may be a variable flow restrictor. For example, the flow restrictor may be a user-operable valve mechanism, such as an adjustable screw. Such a variable flow restrictor allows the user to optimize airflow through the device for different types of aerosol-generating articles. The restriction may be variable to optimize puff detection for a specific user.

A portion of the airflow path upstream of the cavity may have a cross-sectional area of less than 3 mm ² , for example less than 2 mm ² , or less than 1.5 mm ^{2 ,} or less than 0.5 mm ² . A portion of the airflow path upstream of the cavity may have a cross-sectional area of less than 0.5 mm ² , for example less than 0.4 mm ² , or less than 0.2 mm ^{2 ,} or less than 0.1 mm ² . Such cross-sectional areas may provide flow restriction to amplify the sensitivity of a pressure sensor to airflow changes associated with a user puff, for example.

The suction resistance to a flow restriction causes a pressure drop that can be detected by a pressure sensor. Therefore, it may be desirable for the flow restriction upstream of the pressure sensor to provide sufficient suction resistance to cause a detectable pressure drop. The suction resistance may be more important than the absolute cross-sectional area of the airflow path. For example, an airflow path comprising multiple small inlets may provide a greater suction resistance, and thus a greater pressure drop downstream of the inlet, than an airflow path comprising a single inlet of the same cross-sectional area as the combined multiple inlets.

The airflow path upstream of the cavity can preferably have a resistance to draw (RTD) greater than 10 mm H ₂ O. This RTD can provide a detectable pressure drop to a pressure sensor. For example, the RTD can be between 10 mm H ₂ O and 50 mm H ₂ O. For example, a portion of the airflow path that includes the flow restrictor can provide a resistance to draw (RTD) of between 10 mm H ₂ O and 50 mm H ₂ O.

As used herein, the suction resistance is measured according to the conditions specified in ISO 6565:2015. Accordingly, when measured according to the conditions specified in ISO 6565:2015, the suction resistance of the airflow path between the inlet and the pressure sensor can be at least about 70 Pascals (Pa), for example at least about 80 Pa, or at least about 90 Pa, or at least about 100 Pa. 100 Pa is about 10 mm water level (mmH ₂ O). The RTD can be at least 150 Pa, or at least 200 Pa, for example at least about 450 Pa. 450 Pa is about 45 mm water level (mmH ₂ O). The conditions specified in ISO 6565:2015 include an outlet flow rate of 17.5 milliliters per second, an ambient temperature of 22°C, and a relative ambient humidity of 60%.

The flow restrictor may be any suitable flow restriction that causes a pressure drop within the airflow path that is measurable by the pressure sensor when the user puffs the aerosol generating device.

In some preferred embodiments, the flow restrictor is provided by an inlet in the airflow path. The inlet may comprise a plurality of inlets. For example, the inlet may comprise 1 to 30 inlets, or 4 to 25 inlets, or 7 to 20 openings. In some embodiments, the inlet may comprise 14 to 17 inlets. The inlet or plurality of inlets may have any suitable size and shape to provide the desired aspiration resistance and pressure drop in the airflow path when a user puffs on the aerosol-generating device. For example, in some preferred embodiments, the inlet may comprise 5 to 25 inlets, more preferably 14 to 17 inlets, each of which has a substantially circular cross-sectional shape with a diameter in the range of about 0.3 to 1.2 mm, more preferably about 0.5 mm. Preferably, the inlet or plurality of inlets is arranged such that ambient air can be drawn into the aerosol-generating device. The inlet or multiple inlets may have a combined total cross-sectional area less than the cross-sectional area of the airflow path immediately behind the inlet(s).

A pressure sensor may be located on the flow restrictor and detect a pressure drop associated with an increased air velocity through the flow restrictor during a user puff. The pressure sensor may be located upstream of the cavity but downstream of the flow restrictor. The flow restrictor may enhance the pressure drop associated with the user puff, increase the sensitivity of the pressure sensor, and improve the accuracy of puff detection.

The airflow path upstream of the cavity may include a flow restrictor and may further include an expansion zone downstream of the flow restrictor. Preferably, the pressure sensor is located in the expansion zone. This configuration can optimally amplify the sensitivity of the pressure sensor. For example, the airflow path may be defined at least in part by a channel having a first portion having a first cross-sectional area and a second portion having a second cross-sectional area exceeding the first cross-sectional area. The first portion forms the flow restrictor, and preferably, the pressure sensor is located in the second portion.

The airflow path upstream of the cavity may further include an inlet portion having an inlet cross-sectional area. The inlet cross-sectional area may be greater than the first cross-sectional area. The airflow path may be defined at least in part by an upstream section having an upstream cross-sectional area, a middle section having an intermediate cross-sectional area, and a downstream section having a downstream cross-sectional area. The upstream cross-sectional area may be greater than the intermediate cross-sectional area. The downstream cross-sectional area may be greater than the intermediate cross-sectional area. Preferably, the pressure sensor is located within the downstream section. The middle section may form a flow restrictor. The downstream section may form an expansion zone.

For example, as described above, the upstream section may be the inlet section; the middle section may be the first section; and the downstream section may be the second section.

The airflow path upstream of the cavity may further include a third portion having a third cross-sectional area, the third cross-sectional area being smaller than the second cross-sectional area, e.g. the third portion forming a second flow restriction.

The airflow path upstream of the cavity may include a first flow restrictor and a second flow restrictor, and the pressure sensor is positioned between the first flow restrictor and the second flow restrictor, for example, the pressure sensor is positioned within an expansion portion or expansion chamber positioned between the first flow restrictor and the second flow restrictor. The second flow restrictor may advantageously help prevent backflow of vapor from the vapor chamber, which could potentially contaminate the pressure sensor.

The aerosol-generating device may include a plurality of air inlets that allow air to enter the cavity. For example, the device may include multiple air inlets, each associated with an airflow path leading into the cavity. A pressure sensor may be located in one of these airflow paths. One or more of the airflow paths may be associated with a pressure sensor. This may help build a degree of redundancy into the system.

The plurality of air inlets can provide an air flow path into an expansion cavity located downstream of the air inlets and upstream of the cavity. The pressure sensor is preferably located within the expansion cavity. Preferably, the total cross-sectional area of the plurality of air inlets is smaller than the cross-sectional area of the expansion cavity. Thus, the air flow path through the plurality of inlets upstream of the expansion cavity containing the pressure sensor can provide a resistance to draw (RTD) of greater than 10 mm H ₂ O, for example greater than 20 H ₂ O, or greater than 30 H ₂ O, preferably from 10 mm H ₂ O to 50 mm H ₂ O.

The aerosol-generating device may include a second pressure sensor configured to sense ambient pressure. The ambient pressure sensor may provide a signal representing background pressure, which serves as a reference or baseline signal, to help improve the accuracy of puff detection. For example, small pressure changes may occur naturally due to weather changes, or when a user changes altitude, for example, by climbing stairs, or when there is a sudden noise. Measuring the background pressure may help prevent erroneous readings of the user's puff.

The airflow path may be partially defined by a channel adjacent to or in contact with a heater. For example, the airflow path may be positioned in thermal contact with a heater configured to heat an aerosol-forming substrate positioned within the cavity. Thus, the incoming airflow may be partially heated by the same heater configured to heat the substrate within the cavity. This may capture some of the thermal energy that would otherwise be lost. By allowing the airflow path to be heated in this manner, less energy may be required to achieve the desired temperature in the aerosol-forming substrate.

Preferably, the device comprises a pressure sensor, such as an absolute pressure sensor, for example a piezoresistive pressure sensor. The pressure sensor may comprise any suitable type of pressure sensor. The pressure sensor may be an absolute pressure sensor configured to determine an absolute pressure at a location within the airflow path. The pressure sensor may be a gauge pressure sensor configured to detect a relative pressure at a location within the airflow path compared to an ambient pressure adjacent to the aerosol-generating device. The pressure sensor may be a differential pressure sensor configured to detect a pressure difference between a first location within the airflow path and a second location within the airflow path. The pressure sensor may be a capacitive pressure sensor. The pressure sensor may be a piezoresistive pressure sensor. The pressure sensor may be a strain gauge. Preferably, the pressure sensor is a microelectromechanical systems (MEMS) pressure sensor. Advantageously, the MEMS pressure sensor may be sufficiently small to fit within the aerosol-generating device without significantly increasing the size of the aerosol-generating device. A non-limiting example of a suitable absolute pressure sensor is the MEMS nano pressure sensor LPS22HBTR manufactured by STMicroelectronics, which has an operating pressure of about 26 kiloPascals (kPa) to about 126 kiloPascals (kPa) and dimensions of 2 mm x 2 mm x 0.76 mm.

Preferably, the aerosol-generating device is configured to generate an aerosol from the aerosol-forming substrate during a use session having a start and an end of the use session. Advantageously, the device may be configured to distinguish between a puff period and a non-puff period. A puff period may be defined as any period during a use session during which the user actively puffs. A non-puff period may be defined as any period during a use session during which the user does not actively puff.

The device is preferably configured to heat the aerosol-forming substrate during a use session with reference to two different target temperatures: an ambient or maintenance target temperature and an operating target temperature. The ambient target temperature is preferably higher than room temperature, and the operating target temperature is higher than the ambient target temperature. Preferably, a signal from a flow detector, such as a pressure sensor, is used to control the temperature to the ambient target temperature or the operating target temperature.

Accordingly, the device is preferably configured to control the temperature of the aerosol-forming substrate with reference to the ambient target temperature during the non-puff period and with respect to the operating target temperature during the puff period. As a result, the temperature of the substrate is consistently maintained at the ambient target temperature during the non-puff period. When the start of a user puff is detected, the temperature may be increased to the operating target temperature, and after the user puff is terminated, the temperature may be further decreased to the ambient target temperature.

Accordingly, according to an aspect of the present invention, there may be provided an aerosol-generating device configured to generate an aerosol from an aerosol-forming substrate during a use session, for example an aerosol-generating device as described above, wherein the device is configured to heat the aerosol-forming substrate during the use session with reference to two different target temperatures, an ambient target temperature and an operating target temperature, wherein the ambient target temperature is higher than room temperature and the operating target temperature is higher than the ambient target temperature, the device being configured to heat the aerosol-forming substrate to the ambient temperature during the use session, the device being further configured to heat the aerosol-forming substrate from the ambient target temperature to the operating target temperature during a user puff performed during the use session, wherein the aerosol-forming substrate is enabled to cool from the operating target temperature after termination of the user puff.

Accordingly, according to an aspect of the present invention, there may be provided an aerosol-generating device configured to generate an aerosol from an aerosol-forming substrate during a use session, for example an aerosol-generating device as described above, wherein the device is configured to heat the aerosol-forming substrate during the use session with reference to two different target temperatures, an ambient target temperature and an operational target temperature, wherein the ambient target temperature is greater than room temperature and the operational target temperature is greater than the ambient target temperature, wherein a puff period is defined as any period during the use session during which a user actively takes a puff, and a non-puff period is defined as any period during the use session when a user does not actively take a puff, wherein the device is configured to operate in a standby mode during the non-puff period, the temperature of the aerosol-forming substrate being controlled with reference to the ambient target temperature when operated in the standby mode, and wherein the device is configured to operate in an operational mode during the puff period, the temperature of the aerosol-forming substrate being controlled with reference to the operational target temperature when operated in the operational mode.

Accordingly, according to an aspect of the present invention, there may be provided an aerosol-generating device configured to generate an aerosol from an aerosol-forming substrate during a use session, for example an aerosol-generating device as described above, wherein the device is configured to heat the aerosol-forming substrate during the use session according to a standby mode or an operating mode, wherein during the standby mode, the temperature of the aerosol-forming substrate is controlled with reference to a standby target temperature, and during the operating mode, the temperature of the aerosol-forming substrate is controlled with reference to an operating target temperature, wherein the standby target temperature is a temperature higher than room temperature, and the operating target temperature is a temperature higher than the standby target temperature, and wherein the operation of the device changes from the standby mode to the operating mode when a user starts taking a puff, and changes from the operating mode to the standby mode when a user ends taking a puff.

The ambient target temperature is preferably a temperature that is too low to generate substantial aerosol from the aerosol-forming substrate. That is, the ambient temperature may be below the effective aerosolization temperature of the aerosol-forming material or a component of the substrate. For example, the ambient target temperature may be lower than the vaporization temperature or effective boiling point of the aerosol former or aerosol former mixture of the aerosol-forming substrate. For example, the ambient target temperature may be set to be lower than the boiling point of propylene glycol, lower than the boiling point of glycerol, or lower than the boiling point of a particular mixture of propylene glycol and glycerol used as the aerosol former in the aerosol-forming substrate. The ambient temperature may alternatively be referred to as the maintenance temperature.

The target ambient temperature may be less than 250°C, for example less than 230°C, for example less than 210°C, preferably less than 200°C, for example less than 180°C, or less than 160°C. The target ambient temperature may be a temperature of 50°C to 250°C, for example 80°C to 200°C, for example 100°C to 180°C.

The target operating temperature is preferably a temperature sufficiently high to release an aerosol from the aerosol-forming substrate. That is, the target operating temperature may be higher than the effective aerosolization temperature for the substrate. For example, the target operating temperature may be higher than the effective boiling point of the aerosol former or aerosol former mixture of the aerosol-forming substrate, such as higher than the boiling point of propylene glycol, higher than the boiling point of glycerol, or higher than the boiling point of a particular mixture of propylene glycol and glycerol used as the aerosol former in the aerosol-forming substrate.

The operating target temperature may be greater than 160°C, for example greater than 180°C, or greater than 200°C, or greater than 250°C, for example greater than 280°C, or greater than 300°C, or greater than 320°C, or greater than 340°C. The operating target temperature may be a temperature of 160°C to 400°C, for example, 180°C to 340°C, for example, 220°C to 300°C.

The ambient target temperature may remain constant throughout the duration of the use session. Alternatively, the ambient target temperature may vary throughout the duration of the use session. That is, the ambient target temperature may vary during the use session to account for the depletion of aerosol-forming components as the user puffs during the use session.

The target operating temperature may remain constant throughout the duration of the use session. Alternatively, the target operating temperature may vary over the duration of the use session. The target operating temperature may vary from puff to puff. Varying the target operating temperature, for example, increasing the target operating temperature, may help optimize aerosol delivery from an aerosol-forming substrate whose aerosol-forming components are depleted during the use session.

Preferably, a use session has a use session start and a use session end. Preferably, the aerosol-forming substrate is heated to an ambient target temperature at the start of the use session and maintained above the ambient target temperature for the duration of the use session until the end of the use session. A use session can be defined between the start of the use session and the end of the use session, a puff period can be defined as any period during the use session during which a user actively takes a puff, a non-puff period can be defined as any period during the use session during which a user does not actively take a puff, and the temperature of the aerosol-forming substrate can be controlled with reference to the ambient target temperature during the non-puff period and with respect to the operating target temperature during the puff period.

Preferably, each of the one or more puffs taken during a use session has a puff start and a puff end, and the period between the puff start and the puff end is defined as the puff duration.

A use session may have a predetermined duration set by reference to the duration of the use session, for example, time, by reference to a use parameter, or by reference to both time and a use parameter. The use parameter may preferably be a parameter selected from a list consisting of the number of user puffs taken during the use session, the volume of aerosol generated during the use session, and the power supplied to the heater during the use session.

The device is preferably configured to detect one or more user puffs taken during a use session. The device is configured to detect the start of a user puff taken during a use session, for example, each user puff taken during the use session. The device is preferably configured to detect the end of a user puff taken during a use session, for example, each user puff taken during the use session. Accordingly, the device may be configured to determine the duration of a user puff taken during a use session, for example, each user puff taken during the use session.

Advantageously, the device may be configured to characterize user puffs taken during a use session, for example, each puff taken during a use session. For example, the device may be configured to determine the volume of aerosol generated during user puffs taken during a use session, for example, each user puff taken during a use session.

The device preferably comprises a power supply, for example a battery, such as a rechargeable battery, for supplying energy to heat the aerosol-forming substrate.

The device preferably comprises at least one heater for heating the aerosol-forming substrate. For example, the device may comprise a heater for heating an external portion of the aerosol-forming substrate. This external heater may surround or partially surround a portion of the aerosol-forming substrate contained within the device. The external heater may be a preferred heater for heating the substrate contained within the cavity to an ambient target temperature, as the aerosol-forming substrate can be heated to a uniform temperature without contact between the substrate and the heater.

The device may include a heater for heating an internal portion of the aerosol-forming substrate, for example a heater insertable into a portion of the aerosol-forming substrate accommodated within the device.

The device may include a heater for heating air within an airflow path upstream of the aerosol-forming substrate, for example, a heater for heating air drawn into the device such that the heated air acts to heat an aerosol-forming substrate contained within the device.

The device may be configured to activate the heater upon detecting a user puff. For example, the heater may be configured to heat the aerosol-forming substrate after the device detects the start of a user puff. The heater may be configured to deactivate after the device detects the end of a user puff.

Preferably, the aerosol-generating device comprises a controller for controlling the generation of the aerosol, such as a controller in communication with a power supply and a heater. This controller may receive an inflow signal, for example, from a pressure sensor, and determine whether a puff is being taken. The controller may control the power supply to one or more heaters based on this inflow signal.

The device may be configured to characterize a user puff by monitoring a parameter indicative of power supplied by the power supply. For example, the power supply may supply power to maintain a heater at a predetermined temperature during a use session. The controller may be configured to monitor the parameter indicative of power supplied by the power supply. When the user puffs the device to generate an aerosol, the heater cools, requiring more power to maintain the heater at the predetermined temperature. Thus, by monitoring the parameter indicative of power supplied by the power supply, the device may characterize a user puff, wherein the user puff is defined by a puff start and a puff end.

The device may include one or more resistive heaters arranged to heat an aerosol-forming substrate contained within a cavity of the device. For example, any of the heaters described above may be resistive heaters.

The device may include an induction heater arranged to heat an aerosol-forming substrate contained within a cavity of the device, for example, the device may include an inductor arranged to heat a susceptor arranged in thermal communication with the aerosol-forming substrate contained within the cavity of the device. Any of the heaters described above may be induction heaters. The susceptor, which may also be referred to as a susceptor element, may comprise or consist of one or more susceptor materials.

Suitable susceptor materials may include, but are not limited to, carbon, carbon-based materials, graphene, graphite, expanded graphite, molybdenum, silicon carbide, stainless steel, niobium, aluminum, nickel, nickel-containing compounds, titanium, and composites of metallic materials. Suitable susceptor materials may include ferromagnetic materials, such as ferritic iron, ferromagnetic alloys, such as ferromagnetic steel or stainless steel, ferromagnetic particles, and ferrite. The susceptor material may comprise greater than 5%, preferably greater than 20%, more preferably greater than 50% or greater than 90%, of a ferromagnetic or paramagnetic material. Preferred susceptor materials may include metals, metal alloys, or carbon.

The device may include a capacitive or dielectric heater for heating an aerosol-forming substrate contained within a cavity of the device, for example, the device may include two opposing electrodes supplied by a high frequency AC signal through an impedance matching circuit, thereby heating the substrate positioned within the cavity between the two opposing electrodes with microwaves.

In some embodiments, the aerosol-generating device may include a heater assembly. Thus, one or more heaters of the aerosol-generating device may be part of the heater assembly. The heater assembly may include a heater configured for resistive heating. The heater may include a polymer matrix and a polymer composite comprising at least one of graphite, a graphite-derived material, and hexagonal boron nitride dispersed within the polymer matrix. A heater comprising a polymer matrix and filler particles of at least one of graphite, a graphite-derived material, and hexagonal boron nitride dispersed within the polymer matrix may be easier to manufacture than similar heaters configured for resistive heating made of other conductive materials commonly used in existing heater assemblies for aerosol-generating devices. For example, the thermoplastic properties of the polymer matrix may allow the polymer composite to be tailored for convenient processing, making the polymer composite suitable for precise and controlled molding. In particular, the polymer composite may be easier to form into an elongated, hollow shape compared to conductive materials commonly used in heater assemblies of existing aerosol-generating devices.

By controlling and adjusting the concentration and distribution of conductive filler particles dispersed within a polymer matrix, it may be possible to provide a heating element capable of generating sufficient heat by resistive heating to efficiently heat a solid aerosol-generating substrate of an aerosol-generating article thermally coupled to the heating element.

The heater assembly may comprise a substantially porous heater element. The porous heater element may be configured to convectively transfer heat to the airflow entering the aerosol-generating device, such that the airflow reaches the aerosol-generating substrate in a preheated state. This may be advantageous in that aerosol-forming species present in the aerosol-generating substrate may be more efficiently released upon heating. In general, this may enable more efficient supply and exchange of heat during use of the aerosol-generating device.

To be heated, air will be drawn through a porous heating element. The residence time of the air within the porous element—the average time spent by a fluid parcel within a control volume—will generally be a function of the porosity and tortuosity of the porous element, as well as its geometry. The porosity, average pore size and pore size distribution, and specific surface area of the porous element will also affect the amount of heat exchanged by convection. Simultaneously, the porosity and tortuosity of the porous element will affect the resistance to draw (RTD) of the porous element and the heating element as a whole. By adjusting the porosity, length, and diameter of the porous element, a satisfactory balance can be achieved between the ability to efficiently preheat the air flowing through the porous element and its RTD.

Preferably, the device is configured to determine the temperature of the aerosol-forming substrate during use. For example, the device may include a controller configured to determine the temperature of the aerosol-forming substrate during use, wherein the temperature is determined by monitoring the behavior of the heater during use, for example, by monitoring the apparent resistance or apparent conductivity of the heater. The device may include a sensor configured to determine the temperature of the aerosol-forming substrate during use, for example, a positive temperature coefficient (PTC) sensor, a thermocouple, a thermal switch, or any other temperature control element.

In some embodiments, the aerosol-generating device may further comprise a flow meter, for example, a flow meter for measuring flow in an airflow path upstream of a cavity for receiving the aerosol-forming substrate. The use of a flow meter may be advantageous in development applications because it may allow for effective calibration of the pressure sensor to optimize puff detection for a particular combination of device and substrate. A test system aerosol-generating device for setting or calibrating specific features, such as the pressure sensor, and optimizing features, such as the dimensions of the flow restrictor, may be any aerosol-generating device as described herein with the addition of a flow meter upstream of the restrictor. Such a test system may be particularly advantageous if the flow restrictor of the test system is a variable flow restrictor, which allows the restrictor dimensions to be optimized, for example, for a particular aerosol-generating article. Commercial versions of the aerosol-generating device can then be manufactured with the desired settings and without the need for a flow meter.

Advantageously, the aerosol-generating device may be configured to determine, during use, the start of a use session, enter a standby mode in which an aerosol-forming substrate housed within the device is heated, the temperature of the aerosol-forming substrate being controlled during the standby mode with reference to a standby target temperature, detect a user puff taken during the use session, and enter an operational mode in which greater thermal energy is supplied to the aerosol-forming substrate in response to the detected user puff to increase the temperature of the aerosol-forming substrate, the temperature of the aerosol-forming substrate being controlled during the operational mode with reference to an operational target temperature higher than the standby target temperature.

The aerosol-generating device may include a housing. The housing may be elongated. The housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics, or composites comprising one or more of these materials, or thermoplastics suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), and polyethylene. The material is preferably lightweight and non-brittle.

The device may include one or more power supplies or power sources, one or more heaters, and a controller. The controller may be configured to enter a standby mode at the start of a use session, detect the initiation of a user puff, transition from the standby mode to an operating mode in response to detecting the initiation of the user puff, detect the end of the user puff, and transition from the operating mode to the standby mode in response to detecting the end of the user puff.

The power supply may take the form of a battery. The battery may be rechargeable. The battery may be a lithium-based battery, such as a lithium-cobalt, lithium-iron-phosphate, lithium titanate, or lithium-polymer battery. The battery may be a nickel-metal hydride battery or a nickel-cadmium battery. The power supply may be another form of charge storage device, such as a capacitor. The power supply may be rechargeable and configured for numerous charge and discharge cycles. The power supply may have a capacity that allows for the storage of sufficient energy for one or more user experiences of the aerosol-generating system. For example, the power supply may have a capacity sufficient to allow continuous aerosol generation for a period of about six minutes, or a multiple of six minutes, corresponding to the typical time it takes to smoke a conventional cigarette. In another embodiment, the power supply may have a capacity sufficient to allow for a predetermined number of puffs or separate activations of the aerosol-generating system.

The controller or control circuit may be or include any suitable controller or electrical component. The controller may include memory. Information for performing the above-described method may be stored in the memory. The control circuit may include a microprocessor. The microprocessor may be a programmable microprocessor, a microcontroller, an application-specific integrated circuit (ASIC), or other electronic circuitry capable of providing control. The control circuit may be configured to continuously supply power to the heating element following activation of the device, or may be configured to intermittently supply power, such as with each puff. Power may be supplied to the heating element in the form of pulses of current, for example, by pulse width modulation (PWM). The control circuit may further include electronic components. For example, in some implementations, the control circuit may include any of a sensor, a switch, and a display element. The controller may be configured to increase power supplied to one or more heaters during an operating mode compared to a standby mode.

The device may include a first heater and a second heater. The first heater may be arranged to heat the aerosol-forming substrate during the standby mode, and the second heater may be arranged not to heat the aerosol-forming substrate during the standby mode.

Both the first heater and the second heater can be arranged to simultaneously heat the aerosol forming substrate during the operating mode.

The first heater may be arranged to operate throughout the entire use session, while the second heater may be arranged to operate only during a user puff. For example, the second heater may be switched on only during a user puff. Alternatively, the second heater may operate throughout the use session, but the power supplied to the second heater may be increased during a user puff.

According to an aspect of the present invention, an aerosol-generating system may be provided, comprising an aerosol-generating device as described above, and an aerosol-generating article comprising an aerosol-forming substrate. The aerosol-generating article is configured to be at least partially contained within the aerosol-generating device. The aerosol-forming article may comprise a plurality of components, each comprising an aerosol-forming substrate assembled within a wrapper.

In some embodiments, the aerosol-generating article may have a resistance to draw (RTD) of 10 mm H ₂ O to 50 mm H ₂ O.

The aerosol-generating system can have a system airflow path defined through the device and the aerosol-generating article when the aerosol-generating article is contained within the device, for example, the system airflow path includes an airflow path defined through the device and an airflow path defined through the aerosol-generating article. The system airflow path can have a resistance to draw (RTD) of 20 mm H ₂ O to 100 mm H ₂ O.

The article may appear substantially similar to a conventional cigarette. The article may be rod-shaped, or may have a rod-like or stick-like shape. The article may have a substantially cylindrical shape, for example, a rectangular cylinder. The article may have a length of 30 mm to 120 mm, for example, 40 mm to 80 mm, for example, about 45 mm. The article may have a diameter of 3.5 mm to 10 mm, for example, 4 mm to 8.5 mm, for example, 4.5 mm to 7.5 mm.

The substrate may be substantially cylindrical in shape, for example, a rectangular cylindrical shape. Reference is made herein to an inner portion and an outer portion of the aerosol-forming substrate. The inner portion may be or include an aerosol-forming material within an axially central portion of the aerosol-forming substrate, for example, an axially central cylindrical portion or an axially central rectangular cylindrical portion. The outer portion may be or include an aerosol-forming material within an axially outer portion of the aerosol-forming substrate. The outer portion may be cylindrical in shape, for example, a rectangular cylindrical portion. The outer portion may have an annular cross-section, for example, a circular annular cross-section. There may be no aerosol-forming substrate between the inner portion and the outer portion. The inner portion and the outer portion may be in contact. The entirety of the aerosol-forming material of the aerosol-forming substrate may be found in the inner and outer portions.

Optionally, the article comprises a front plug. Optionally, the article comprises an aerosol-forming substrate. Optionally, the article comprises a first hollow tube, for example, a first hollow acetate tube. Optionally, the article comprises a second hollow tube, for example, a second hollow acetate tube. Optionally, the second hollow tube comprises one or more ventilation holes. Optionally, the article comprises a mouth plug filter. Optionally, the article comprises a wrapper, for example, a paper wrapper. Optionally, one or more or all of the front plug, the aerosol-forming substrate, the first hollow tube, the second hollow tube, if present, and the mouth plug filter are surrounded by the wrapper.

Optionally, the front plug is arranged at the most upstream end of the article. Optionally, the aerosol-forming substrate is arranged downstream of the front plug. Optionally, the first hollow tube is arranged downstream of the aerosol-forming substrate. Optionally, the second hollow tube is arranged downstream of the first hollow tube. Optionally, the mouth plug filter is arranged downstream of one or both of the first hollow tube and the second hollow tube. Optionally, the mouth plug filter is arranged at the most downstream end of the article. Optionally, the most downstream end of the article, which may be referred to as the mouth end of the article, may be configured to be inserted into the mouth of a user. The user may, for example, inhale directly on the mouth end of the article.

At least one of the front plug, the aerosol-forming substrate, the first hollow tube, the second hollow tube, and the mouth plug filter can be substantially cylindrical, for example, a vertically cylindrical shape. At least one of the front plug, the aerosol-forming substrate, the first hollow tube, the second hollow tube, and the mouth plug filter can have a diameter of from 3.5 mm to 10 mm. Optionally, the front plug has a length of from 2 mm to 10 mm. Optionally, the aerosol-forming substrate within the article has a length of from 5 mm to 20 mm. Optionally, the first hollow tube has a length of from 2 mm to 20 mm. Optionally, the second hollow tube has a length of from 2 mm to 20 mm. Optionally, the mouth plug filter has a length of from 5 mm to 20 mm.

The article may comprise or be a cartridge. The cartridge may hold an aerosol-forming substrate. The cartridge may hold a susceptor. The cartridge may comprise a cartridge housing. One or both of the aerosol-forming substrate and the susceptor may be positioned within the cartridge housing.

The cartridge may have a length, width, and thickness. The thickness may be less than 0.5 or 0.2 times the length, width, or both. In this case, the cartridge may be referred to as a flat or planar cartridge. The cartridge may have any suitable shape and size, for example, a substantially rectangular cylinder or a rectangular parallelepiped. The cartridge may be any cartridge described in WO2015177043, the contents of which are incorporated herein by reference.

The susceptor can have a susceptor length, a susceptor width, and a susceptor thickness. The susceptor thickness can be less than 0.5 times or 0.2 times the susceptor length, the susceptor width, or both. In this case, the susceptor can be referred to as a flat or planar susceptor. The aerosol-forming substrate can have a substrate length, a substrate width, and a substrate thickness. The substrate thickness can be less than 0.5 times or 0.2 times the substrate length, the substrate width, or both. In this case, the aerosol-forming substrate can be referred to as a flat or planar aerosol-forming substrate.

The susceptor may form, be attached to, or be positioned adjacent to the interior surface of the cartridge housing. The susceptor may be in contact with the aerosol-forming substrate. The susceptor may be positioned between the aerosol-forming substrate and the interior surface. The largest or second largest surface of the susceptor may be positioned in contact with or adjacent to the largest or second largest surface of the aerosol-forming substrate. This may be particularly advantageous when one or both of the susceptor and the aerosol-forming substrate are flat or planar. Advantageously, this may maximize heat transfer from the susceptor to the aerosol-forming substrate during use.

According to one aspect of the present invention, a method of generating an aerosol using an aerosol-generating device may be provided, the aerosol-generating device comprising a cavity for receiving at least a portion of the aerosol-forming substrate, an airflow path upstream of the cavity through which a user can draw air when using the device, the airflow path connecting the cavity with the external environment, and comprising a pressure sensor positioned in communication with the airflow path upstream of the cavity, the method comprising the steps of arranging an aerosol-forming substrate within the cavity, operating the device, detecting a change in pressure in the airflow path associated with the start of a user puff, and detecting a change in pressure in the airflow path associated with the end of the user puff, thereby detecting a user puff.

According to one aspect of the present invention, a method of generating an aerosol using an aerosol-generating device may be provided, the aerosol-generating device comprising a cavity for receiving at least a portion of the aerosol-forming substrate, and an airflow path upstream of the cavity through which a user can draw air when using the device, the airflow path connecting the cavity with the external environment and including a pressure sensor positioned in communication with the airflow path upstream of the cavity, the method comprising the steps of: arranging an aerosol-forming substrate within the cavity; operating the device to operate in a standby mode; detecting a pressure change in the airflow path associated with the initiation of a user puff; switching an operating mode from the standby mode to an operating mode in response to the detected initiation of the user puff; detecting a pressure change in the airflow path associated with the termination of the user puff; and switching the operating mode from the operating mode to the standby mode in response to the detected termination of the user puff.

According to one aspect of the present invention, a method of generating an aerosol using an aerosol-generating device may be provided, the aerosol-generating device comprising a cavity for accommodating at least a portion of the aerosol-forming substrate, and an airflow path upstream of the cavity through which a user can draw air when using the device, the airflow path connecting the cavity to the external environment, the method comprising the steps of: arranging an aerosol-forming substrate within the cavity; operating the device to operate in a standby mode in which a temperature of the aerosol-forming substrate is controlled with reference to an ambient target temperature; and, in response to a user puff, switching an operating mode from the standby mode to an operating mode in which a temperature of the aerosol-forming substrate is controlled with reference to an operating target temperature, the operating target temperature being a temperature higher than the ambient target temperature.

The method for generating an aerosol may comprise any of the devices or systems described above.

As used herein, the term "aerosol-generating article" or simply "article" may refer to an article capable of generating or emitting an aerosol, for example, when heated.

As used herein, the term "aerosol-forming substrate" may refer to a substrate capable of releasing an aerosol or a volatile compound capable of forming an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. The aerosol-forming substrate may comprise one or more aerosol-forming agents or aerosol-forming materials. The aerosol-forming substrate may be adsorbed onto, coated on, impregnated with, or otherwise loaded onto a carrier or support. The aerosol-forming substrate may conveniently be part of an aerosol-generating article or a smoking article.

Optionally, the aerosol-forming substrate is a solid aerosol-forming substrate. However, the aerosol-forming substrate may comprise both solid and liquid components. Alternatively, the aerosol-forming substrate may be a liquid aerosol-forming substrate.

Optionally, the aerosol-forming substrate comprises nicotine. Optionally, the aerosol-forming substrate comprises tobacco. Alternatively, or additionally, the aerosol-forming substrate may comprise a non-tobacco material containing an aerosol-forming material.

Optionally, the aerosol-forming substrate may comprise a sheet of aerosol-forming material. For example, the aerosol-forming substrate may comprise a sheet of homogenized tobacco material, such as a crimped and pleated sheet of homogenized tobacco material.

As used herein, the term "aerosol former" may refer to any suitable known compound or mixture of compounds which, when used, facilitates the formation of an aerosol and is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article. Suitable aerosol formers are known in the art and include, but are not limited to, polyhydric alcohols such as propylene glycol, triethylene glycol, 1,3-butanediol, and glycerin; esters of polyhydric alcohols such as glycerol mono-, di-, or triacetate; and aliphatic esters of mono-, di-, or polycarboxylic acids such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Preferred aerosol formers are polyhydric alcohols or mixtures thereof, such as propylene glycol, triethylene glycol, 1,3-butanediol, and most preferably glycerin. The aerosol-forming substrate may comprise one or more aerosol formers.

As used herein, the “aerosolization temperature” of an aerosol-forming substrate may refer to the minimum temperature at which the aerosol-forming substrate releases an aerosol or a volatile compound capable of forming an aerosol, or at which the aerosol-forming substrate releases a significant amount of an aerosol or a volatile compound capable of forming an aerosol.

As used herein, the term "use session" may refer to a period of time during which a series of puffs are applied by a user to extract an aerosol from an aerosol forming substrate.

As used herein, the term "aerosol-generating device" may refer to a device for use with an aerosol-generating article to enable the generation or emission of an aerosol.

As used herein, the term "susceptor" may refer to an element comprising a material capable of converting magnetic field energy into heat. When the susceptor is placed within an alternating magnetic field, the susceptor may be heated. The heating of the susceptor may be due to at least one of hysteresis loss and eddy current induced in the susceptor, depending on the electrical and magnetic properties of the susceptor material.

As used herein, when referring to an aerosol-generating article or an aerosol-generating device, the terms "upstream" and "downstream" may be used to describe the relative positions of components, or portions of components, of an aerosol-generating article or device with respect to the direction in which air flows through the aerosol-generating article or device during use. An aerosol-generating article may include an upstream end through which air enters the article during use. An aerosol-generating article may include a downstream end through which air or aerosol exits the article during use. An aerosol-generating device may include an upstream end through which air enters the device during use. An aerosol-generating article may include a downstream end through which air or aerosol exits the device during use. An aerosol-generating system may be configured such that air enters the upstream end of an aerosol-generating device, passes into an upstream end of an aerosol-generating article engaged with the device, and exits the downstream end of the aerosol-generating article.

As used herein and in reference to the present invention, the term "longitudinal" is used to describe the direction between the upstream and downstream ends of an aerosol-generating article or between the upstream and downstream ends of an aerosol-generating device. During use, air is drawn through the aerosol-generating article in the longitudinal direction.

As used herein with reference to the present invention, the term "length" is used to describe the maximum dimension of an aerosol-generating article or aerosol-generating device or the maximum dimension in the longitudinal direction of a component of an aerosol-generating article or aerosol-generating device.

As used herein in connection with the present invention, the term "transverse direction" is used to describe a direction perpendicular to the longitudinal direction. Unless otherwise specified, reference to a "cross-section" of an aerosol-generating article, aerosol-generating device, or a component of an aerosol-generating article or aerosol-generating device refers to a cross-section.

As used herein in connection with the present invention, the term "width" refers to the maximum dimension of an aerosol-generating article or device, or a component of an aerosol-generating article or device, in a transverse direction. For example, if the aerosol-generating article has a substantially circular cross-section, the width of the aerosol-generating article corresponds to the diameter of the aerosol-generating article. If a component of the aerosol-generating article has a substantially circular cross-section, the width of the component of the aerosol-generating article corresponds substantially to the diameter of the component of the aerosol-generating article.

As used herein, the term "heater" refers to a component configured to transfer thermal energy to a liquid aerosol generating substrate.

As used herein, the term "porous portion" refers to a body portion having a plurality of pores, at least some of which are interconnected. Thus, the porous portion of the body generally defines a flow path through the porous portion, such that a fluid can flow from one end surface of the porous portion to a second end surface of the porous portion opposite the first end surface. Generally, the pressure drop across the porous portion will be greater than the pressure drop across a hollow tubular element having the same length of the porous portion and a free cross-sectional area equal to the total cross-sectional area of the porous portion. Therefore, flow across the porous portion will generally be partially restricted compared to flow through a hollow tubular element of similar dimensions.

The term "porosity" of a body generally refers to the ratio of the volume of accessible pores and voids to the bulk volume occupied by the body. The term "cross-sectional porosity" refers to the fraction of void space in the cross-sectional area of a porous body, for example, a cross-section of a porous portion of a heating body of a heater assembly according to the present invention. Cross-sectional porosity is the area fraction of void space in the transverse cross-sectional area of the porous body. The cross-sectional area of a porous body is the area of the porous body in a plane perpendicular to the longitudinal axis of the porous body, which is also generally the longitudinal axis of the heater assembly and the longitudinal axis of an aerosol generating device comprising the heater assembly.

A porous body will typically be substantially cylindrical, and thus its cross-section will be substantially circular. However, more generally, it will be possible to identify a longitudinal axis of the porous body, and its cross-section will lie in a plane substantially perpendicular to said longitudinal axis.

As used herein, the term "electrically insulating" may refer to a material having an electrical conductivity of less than 0.8x10 ⁴ Siemens/m, for example, a resistivity of at least 1x10 ^-4 , 5x10 ^-4 , or 1x10 ^-5 ohm meters in at least one direction, for example in all directions, at room temperature (20° C.) and a relative humidity of 50%.

As used herein, the term "electrical resistivity" may refer to a material having an electrical conductivity of at least 0.8x10 ⁶ Siemens/m, for example, a resistivity of 1x10 ^-4 , 5x10 ^-5 , or 1x10 ^-5 ohm meters or less in at least one direction, for example, in all directions, at room temperature (20° C.) and a relative humidity of 50%.

As used herein, the term "thermal conductivity" may refer to a material having a thermal conductivity of at least 5, 10, 20, 50, or 100 W/m-Kelvin in at least one direction, for example in all directions, at room temperature (20°C) and a relative humidity of 50%.

Various references have been made to ranges herein, such as temperature ranges. For the avoidance of doubt, unless otherwise specified, any range referred to herein may have only an upper limit, only a lower limit, or both. The limits for a temperature range, for example, any upper or lower limit of any one or more of the temperature ranges for a heating zone, heater, or susceptor as described above, may be predetermined. The limits may be stored in the controller or memory, for example, in the memory of the controller. The limits may be stored as a temperature value or in another form representing a temperature value, for example, as a value of the electrical resistance of a component to which the temperature range applies. In this case, the electrical resistance of the component, rather than its temperature, may be monitored and compared to a temperature vs. electrical resistance dataset to estimate the temperature of the component.

The present invention is defined by 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 of the features of other embodiments, implementations, or aspects described herein.

A non-exhaustive list of non-limiting examples is provided below. Any one or more features of these examples may be combined with any one or more features of any other embodiment, implementation, or aspect described herein.

Ex1 - An aerosol-generating device configured to generate an aerosol from an aerosol-forming substrate during a use session, wherein the device is configured to heat the aerosol-forming substrate to an ambient temperature during the use session, and wherein the device is configured to increase the temperature of the aerosol-forming substrate from the ambient temperature when a user takes a puff.

Ex2 - An aerosol generating device according to Ex1, wherein the device is configured to provide a heat boost to the aerosol forming substrate during a user puff taken during the user session.

Ex3 - An aerosol generating device according to Ex1 or Ex2, wherein the device is configured to heat the aerosol-forming substrate during the use session according to a standby mode or an operating mode, wherein during the standby mode, the temperature of the aerosol-forming substrate is controlled with reference to a standby target temperature, and during the operating mode, the temperature of the aerosol-forming substrate is controlled with reference to an operating target temperature, wherein the standby target temperature is a temperature higher than room temperature, and the operating target temperature is a temperature higher than the standby target temperature.

Ex4 - An aerosol generating device according to Ex3, wherein the operation of the device changes from a standby mode to an operating mode when the user starts taking a puff and from an operating mode to a standby mode when the user ends taking a puff.

Ex5 - An aerosol generating device according to any of the preceding embodiments, wherein the device is configured to heat the aerosol-forming substrate during a use session in a standby mode or an operating mode, wherein during the standby mode, the temperature of the aerosol-forming substrate is controlled with reference to a standby target temperature, and during the operating mode, the temperature of the aerosol-forming substrate is controlled with reference to an operating target temperature, wherein the standby target temperature is a temperature higher than room temperature, and the operating target temperature is a temperature higher than the standby target temperature.

Ex6. An aerosol-generating device configured to generate an aerosol from an aerosol-forming substrate, for example, an aerosol-generating device according to any one of the preceding embodiments, wherein the device defines a cavity for receiving at least a portion of the aerosol-forming substrate, and defines an airflow path upstream of the cavity through which a user can draw air when using the device, the airflow path connecting the cavity with the external environment, the device comprising a flow detection means, for example, a pressure sensor positioned in communication with the airflow path upstream of the cavity, and wherein the device is configured to use a signal from the flow detection means, for example, the pressure sensor, to detect one or more user puffs taken during the use session.

Ex7. An aerosol-generating device configured to generate an aerosol from an aerosol-forming substrate, for example, an aerosol-generating device according to any one of the preceding embodiments, wherein the device defines a cavity for receiving at least a portion of the aerosol-forming substrate, and defines an airflow path upstream of the cavity through which a user can draw air when using the device, the airflow path connecting the cavity with the external environment, the device comprising a puff sensing element having a pressure sensor positioned in communication with the airflow path upstream of the cavity, and a flow restrictor positioned within the airflow path, the device further comprising a flow meter positioned upstream of the pressure sensor, wherein measurements from the flow meter can be used to calibrate the puff sensing element.

Ex8. An aerosol generating device according to Ex7, wherein the flow restrictor is a variable flow restrictor.

Ex9. An aerosol generating device according to any of the preceding embodiments, wherein the airflow path upstream of the cavity acts as or includes a flow restrictor, for example, the flow restrictor includes a mechanical element positioned within the airflow path, for example, an orifice plate positioned within the airflow path.

Ex10. An aerosol generating device according to Ex9, wherein the flow restrictor is a variable flow restrictor, for example, the flow restrictor is an adjustable valve, for example, the flow restrictor comprises a user-operable valve means such as an adjustable screw.

Ex11. An aerosol generating device in any of the preceding embodiments, wherein a portion of the airflow path upstream of the cavity has a cross-sectional area of less than 3 mm ² , for example less than 2 mm ² , or less than 1.5 mm ² , or less than 1 mm ² .

Ex12. An aerosol generating device according to any of the preceding embodiments, wherein the airflow path upstream of the cavity has a resistance to draw (RTD) greater than 10 mm H ₂ O, for example, from 10 mm H ₂ O to 50 mm H 2 O _, and for example, a portion of the airflow path including the flow restrictor provides a resistance to draw (RTD) of from 10 mm H ₂ O to 50 mm H ₂ O.

Ex13. An aerosol generating device according to any of the preceding embodiments, wherein the pressure sensor is located upstream of the cavity but downstream of the flow restrictor.

Ex14. An aerosol generating device according to Ex13, wherein the airflow path upstream of the cavity includes a flow restrictor and an expansion zone downstream of the flow restrictor, and the pressure sensor is located in the expansion zone.

Ex14A. An aerosol generating device according to Ex14, wherein the airflow path upstream of the expansion zone has a resistance to draw (RTD) of greater than 10 mm H ₂ O, for example greater than 20 H ₂ O, or greater than 30 H ₂ O, preferably from 10 mm H ₂ O to 50 mm H ₂ O, for example, a portion of the airflow path including the flow restrictor provides a resistance to draw (RTD) of from 10 mm H ₂ O to 50 mm H ₂ O.

Ex15. An aerosol generating device according to any of the preceding embodiments, wherein the airflow path has a channel having a first portion having a first cross-sectional area and a second portion having a second cross-sectional area greater than the first cross-sectional area, wherein the first portion forms the flow restrictor, and preferably, the pressure sensor is located in the second portion.

Ex15a. An aerosol generating device according to Ex15, wherein the airflow path has a channel having an inlet portion having an inlet cross-sectional area, wherein the inlet cross-sectional area exceeds the first cross-sectional area.

Ex15b. An aerosol generating device according to Ex15 or Ex15a, wherein the airflow path has an upstream section having an upstream cross-sectional area, a middle section having an intermediate cross-sectional area, and a downstream section having a downstream cross-sectional area.

Ex15c. In Ex15b, the inlet portion is an upstream section; the first portion is a middle section; and the second portion is a downstream section. An aerosol generating device.

Ex16. An aerosol generating device according to any one of Ex15 to Ex15c, wherein the airflow path upstream of the cavity further comprises a third portion having a third cross-sectional area, wherein the third cross-sectional area is smaller than the second cross-sectional area, for example, wherein the third portion forms a second flow restriction.

Ex17. An aerosol generating device according to any of the preceding embodiments, wherein the airflow path upstream of the cavity comprises a first flow restrictor and a second flow restrictor, and the pressure sensor is positioned between the first flow restrictor and the second flow restrictor, for example, the pressure sensor is positioned within an expansion portion or expansion chamber positioned between the first flow restrictor and the second flow restrictor.

Ex18. In any of the preceding embodiments, the plurality of air inlets allows air to flow into the cavity, for example, the device comprises a plurality of air inlets, each air inlet being associated with an airflow path leading into the cavity. An aerosol generating device.

Ex19. An aerosol generating device according to Ex18, wherein each air inlet is associated with an airflow path upstream of the cavity, and the pressure sensor is located in one of the airflow paths.

Ex19A. An aerosol generating device according to Ex18 or Ex19, wherein a plurality of air inlets supply an air flow path into an expansion cavity located downstream of the inlets and upstream of the cavity, and wherein the pressure sensor is located within the expansion cavity.

Ex19B. In Ex19A, the total cross-sectional area of the plurality of inlets is smaller than the cross-sectional area of the expansion cavity, an aerosol generating device.

Ex19C. Ex19B, an aerosol generating device, wherein the airflow path through the plurality of inlets upstream of the expansion cavity including the pressure sensor has a resistance to draw (RTD) of greater than 10 mm H ₂ O, for example greater than 20 H ₂ O, or greater than 30 H ₂ O, preferably from 10 mm H ₂ O to 50 mm H ₂ O.

Ex20. An aerosol generating device according to any of the preceding embodiments, comprising a second pressure sensor configured to detect ambient pressure.

Ex21. An aerosol generating device according to any of the preceding embodiments, wherein the airflow path is partially defined by a channel extending adjacent to or in contact with the heater, for example, wherein the airflow path extends in thermal contact with a heater configured to heat an aerosol-forming substrate positioned within the cavity.

Ex22. An aerosol generating device according to any of the preceding embodiments, wherein the purpose of the flow restrictor and/or the first flow restrictor and/or the second flow restrictor is to accelerate the airflow caused by a user puff.

Ex23. An aerosol generating device according to any of the preceding embodiments, wherein the device comprises a pressure sensor, wherein the pressure sensor is an absolute pressure sensor, for example, a piezoresistive pressure sensor.

Ex24. An aerosol generating device according to any of the preceding embodiments, wherein the device comprises a pressure sensor arranged to detect a pressure drop within the airflow path generated when a user takes a puff, for example, a pressure sensor arranged in a flow restriction within the airflow path or downstream of a flow restriction within the airflow path.

Ex25. An aerosol generating device according to any of the preceding embodiments, wherein the device is configured to generate an aerosol from an aerosol forming substrate during a use session having a start of the use session and an end of the use session.

Ex26. An aerosol-generating device according to Ex25, wherein the device is configured to distinguish between a puff period and a non-puff period, wherein the puff period is defined as any period during a use session during which the user actively takes a puff, and the non-puff period is defined as any period during a use session during which the user does not actively take a puff.

Ex27. In Ex26, the device is configured to heat the aerosol-forming substrate during a use session with reference to two different target temperatures, an ambient target temperature and an operating target temperature, wherein the ambient target temperature is higher than room temperature, the operating target temperature is higher than the ambient target temperature, and a signal from the pressure sensor is used to control the temperature to the ambient target temperature or the operating target temperature.

Ex27a. In Ex26, the device is configured to heat the aerosol-forming substrate during a use session with reference to two different target temperatures, an ambient target temperature and an operating target temperature, wherein the ambient target temperature is higher than room temperature and the operating target temperature is higher than the ambient target temperature, and a signal from a pressure sensor is used to determine which of the ambient target temperature or the operating target temperature is used to control the temperature of the aerosol-forming substrate.

Ex28. An aerosol generating device according to Ex27, wherein the device is configured to control the temperature of the aerosol forming substrate with reference to an ambient target temperature during a non-puff period and with respect to an operating target temperature during a puff period.

Ex29 An aerosol-generating device configured to generate an aerosol from an aerosol-forming substrate during a use session, for example, an aerosol-generating device according to any one of the preceding embodiments, wherein the device is configured to heat the aerosol-forming substrate during the use session with reference to two different target temperatures, an ambient target temperature and an operating target temperature, wherein the ambient target temperature is higher than room temperature and the operating target temperature is higher than the ambient target temperature, the device being configured to heat the aerosol-forming substrate to the ambient temperature during the use session, the device being further configured to heat the aerosol-forming substrate from the ambient target temperature to the operating target temperature during a user puff performed during the use session, wherein the aerosol-generating device is capable of cooling from the operating target temperature after termination of the user puff.

Ex30. An aerosol-generating device configured to generate an aerosol from an aerosol-forming substrate during a use session, for example, an aerosol-generating device according to any one of the preceding embodiments, wherein the device is configured to heat the aerosol-forming substrate during the use session with reference to two different target temperatures, an ambient target temperature and an operational target temperature, wherein the ambient target temperature is higher than room temperature, and the operational target temperature is higher than the ambient target temperature, wherein a puff period is defined as any period during the use session during which a user actively takes a puff, and a non-puff period is defined as any period during the use session during which a user does not actively take a puff, wherein the device is configured to operate in a standby mode during the non-puff period, and the temperature of the aerosol-forming substrate is controlled with reference to the ambient target temperature when operated in the standby mode, and wherein the device is configured to operate in an operational mode during the puff period, and the temperature of the aerosol-forming substrate is controlled with reference to the operational target temperature when operated in the operational mode.

Ex31. An aerosol-generating device configured to generate an aerosol from an aerosol-forming substrate during a use session, for example, an aerosol-generating device according to any one of the preceding embodiments, wherein the device is configured to heat the aerosol-forming substrate during the use session according to a standby mode or an operating mode, wherein during the standby mode, the temperature of the aerosol-forming substrate is controlled with reference to a standby target temperature, and during the operating mode, the temperature of the aerosol-forming substrate is controlled with reference to an operating target temperature, wherein the standby target temperature is a temperature higher than room temperature, and the operating target temperature is a temperature higher than the standby target temperature, and wherein operation of the device changes from the standby mode to the operating mode when a user starts taking a puff, and changes from the operating mode to the standby mode when a user ends taking a puff.

Ex32. An aerosol-generating device according to Ex31, wherein the puff period is defined as any period during a use session during which the user actively takes a puff, the non-puff period is defined as any period during a use session during which the user does not actively take a puff, and the device is configured to operate in standby mode during the non-puff period, and the device is configured to operate in operating mode during the puff period.

Ex33. An aerosol generating device according to any of the preceding embodiments, wherein the ambient target temperature is too low to emit a significant amount of aerosol from the aerosol forming substrate.

Ex34. An aerosol generating device according to any of the preceding embodiments, wherein the ambient target temperature is lower than the effective boiling point of the aerosol former or aerosol former mixture of the aerosol formers in the aerosol-forming substrate, for example, lower than the boiling point of propylene glycol, lower than the boiling point of glycerol, or lower than the boiling point of a specific mixture of propylene glycol and glycerol used as the aerosol former in the aerosol-forming substrate.

Ex35. An aerosol generating device according to any of the preceding embodiments, wherein the target ambient temperature is less than 250°C, for example less than 230°C, for example less than 210°C, preferably less than 200°C, for example less than 180°C, or less than 160°C.

Ex36. An aerosol generating device according to any of the preceding embodiments, wherein the target ambient temperature is a temperature of 50°C to 250°C, for example, 80°C to 200°C, for example, 100°C to 180°C.

Ex37. An aerosol generating device according to any of the preceding embodiments, wherein the target operating temperature is a temperature sufficiently high to emit an aerosol from the aerosol forming substrate.

Ex38. An aerosol generating device according to any of the preceding embodiments, wherein the operating target temperature is higher than the effective boiling point of the aerosol former or aerosol former mixture of the aerosol formers in the aerosol-forming substrate, for example, higher than the boiling point of propylene glycol, higher than the boiling point of glycerol, or higher than the boiling point of a specific mixture of propylene glycol and glycerol used as the aerosol former in the aerosol-forming substrate.

Ex39. An aerosol generating device according to any of the preceding embodiments, wherein the operating target temperature is greater than 160°C, for example, greater than 180°C, or greater than 200°C, or greater than 250°C, for example, greater than 280°C, or greater than 300°C, or greater than 320°C, or greater than 340°C.

Ex40. An aerosol generating device according to any of the preceding embodiments, wherein the target operating temperature is a temperature of 160°C to 400°C, for example, 180°C to 340°C, for example, 220°C to 300°C.

Ex41. An aerosol generating device according to any of the preceding embodiments, wherein the ambient target temperature is constant throughout the duration of the use session.

Ex42. Apart from Example Ex41, an aerosol generating device according to any of the preceding embodiments, wherein the ambient target temperature varies over the duration of the use session.

Ex43. An aerosol generating device according to any of the preceding embodiments, wherein the operating target temperature is constant throughout the duration of the use session.

Ex44. Independent of Example Ex43, an aerosol generating device according to any of the preceding embodiments, wherein the operating target temperature varies over the duration of the use session, for example, the operating target temperature varies from puff to puff.

Ex45. An aerosol generating device according to any of the preceding embodiments, wherein the use session has a use session start and a use session end, and the aerosol forming substrate is heated to an ambient target temperature at the start of the use session and maintained above the ambient target temperature throughout the duration of the use session until the end of the use session.

Ex46. An aerosol generating device according to any of the preceding embodiments, wherein the use session is defined between the start of the use session and the end of the use session, the puff period is defined as any period during the use session during which the user actively takes a puff, the non-puff period is defined as any period during the use session during which the user does not actively take a puff, and the temperature of the aerosol-forming substrate is controlled with reference to an ambient target temperature during the non-puff period and with respect to an operating target temperature during the puff period.

Ex47. An aerosol-generating device according to Example Ex46, wherein each of the one or more puffs taken during the use session has a puff start and a puff end, and the period between the puff start and the puff end is a puff period.

Ex48. An aerosol generating device according to any of the preceding embodiments, wherein the use session has a predetermined duration set based on the use session duration, for example, based on time, based on a use parameter, or based on both time and a use parameter.

Ex49. In Example Ex48, the use parameter is a parameter selected from a list consisting of the number of user puffs taken during a use session, the volume of aerosol generated during a use session, and the power supplied to the heater during the use session.

Ex50. An aerosol-generating device according to any of the preceding embodiments, wherein the device is configured to detect one or more user puffs taken during the use session.

Ex51. An aerosol-generating device according to any of the preceding embodiments, wherein the device is configured to distinguish between a puff period and a non-puff period, wherein the puff period is defined as any period during a use session during which the user actively takes a puff, and the non-puff period is defined as any period during a use session during which the user does not actively take a puff.

Ex52. An aerosol-generating device according to any of the preceding embodiments, wherein the device is configured to detect the start of a user puff taken during the use session, for example, each user puff taken during the use session.

Ex53. An aerosol-generating device according to any of the preceding embodiments, wherein the device is configured to detect the end of a user puff taken during the use session, for example, each user puff taken during the use session.

Ex54. An aerosol-generating device according to any of the preceding embodiments, wherein the device is configured to determine the number of user puffs taken during the use session, for example, the duration of each user puff taken during the use session.

Ex55. An aerosol-generating device according to any of the preceding embodiments, wherein the device is configured to characterize user puffs taken during the use session, for example, each puff taken during the use session.

Ex56. An aerosol generating device according to Ex55, wherein the device is configured to characterize detected user puffs taken during the use session, for example, each detected user puff taken during the use session.

Ex57. An aerosol generating device according to Ex55 or Ex56, wherein the device is configured to determine a volume of aerosol generated during each user puff taken during the use session, for example, each user puff taken during the use session.

Ex58. An aerosol generating device according to any of the preceding embodiments, wherein the device comprises a pressure sensor for use in detecting one or more user puffs taken during the use session.

Ex59. In Ex58, the pressure sensor detects a change in pressure in the airflow path as a result of the user taking a puff, for example, the puff includes the user drawing air through a portion of the device along the airflow path, and the pressure sensor detects a change in pressure in the airflow path as a result of the user taking a puff.

Ex59a. In Ex58, the pressure sensor detects a change in flow in the airflow path as a result of the user taking a puff, for example, the puff includes the user drawing air through a portion of the device along the airflow path, and the pressure sensor detects a change in pressure in the airflow path as a result of the user taking a puff.

Ex60. An aerosol generating device according to any of the preceding embodiments, wherein the device defines an airflow path through which air can be drawn when a user uses the device.

Ex61. An aerosol generating device according to any of the preceding embodiments, wherein the device defines a cavity having an opening for receiving at least a portion of the aerosol forming substrate.

Ex62. In Ex61, the device defines an airflow path upstream of the cavity through which a user can inhale air when using the device, and the airflow path connects the cavity to the external environment.

Ex63. An aerosol generating device according to any of the preceding embodiments, wherein the device comprises a power supply unit.

Ex64. An aerosol generating device according to any of the preceding embodiments, wherein the device comprises a heater for heating the aerosol forming substrate.

Ex65. An aerosol-generating device according to any of the preceding embodiments, wherein the device comprises a heater for heating an external portion of the aerosol-forming substrate, for example, a heater surrounding or partially surrounding a portion of the aerosol-forming substrate contained within the device.

Ex66. An aerosol-generating device according to any of the preceding embodiments, wherein the device comprises a heater for heating an internal portion of the aerosol-forming substrate, for example, a heater insertable into a portion of the aerosol-forming substrate accommodated in the device.

Ex67. An aerosol-generating device according to any of the preceding embodiments, wherein the device comprises a heater for heating air within an airflow path upstream of the aerosol-forming substrate, for example, a heater for heating air drawn into the device such that the heated air acts to heat the aerosol-forming substrate contained within the device.

Ex68. An aerosol generating device according to any of the preceding embodiments, wherein the device comprises a controller for controlling the generation of an aerosol, for example, a controller communicating with a power supply and a heater.

Ex69. An aerosol generating device according to any of the preceding embodiments, wherein the device comprises a resistive heater arranged to heat an aerosol forming substrate contained within a cavity of the device.

Ex70. An aerosol generating device according to any of the preceding embodiments, wherein the device comprises an induction heater arranged to heat an aerosol-forming substrate contained within a cavity of the device, for example, wherein the device comprises an inductor arranged to heat a susceptor in thermal communication with the aerosol-forming substrate contained within the cavity of the device.

Ex71. An aerosol generating device according to any of the preceding embodiments, wherein the device is configured to determine the temperature of the aerosol forming substrate during use.

Ex72. An aerosol generating device according to any of the preceding embodiments, wherein the device comprises a controller configured to determine a temperature of the aerosol forming substrate during use, wherein the temperature is determined by monitoring the behavior of the heater during use, for example, by monitoring the apparent resistance or apparent conductivity of the heater.

Ex73. An aerosol generating device according to any of the preceding embodiments, wherein the device comprises a sensor configured to determine the temperature of the aerosol forming substrate during use, such as a positive temperature coefficient (PTC) sensor, a thermocouple, a thermal switch, or any other temperature control element.

Ex74. An aerosol generating device according to any of the preceding embodiments, wherein the device further comprises a flow meter, for example, a flow meter for measuring the flow in an airflow path upstream of the cavity for receiving the aerosol-forming substrate.

Ex75. In any of the preceding embodiments, the device, upon use, determines the start of the use session, enters a standby mode in which an aerosol-forming substrate housed within the device is heated, the temperature of the aerosol-forming substrate being controlled during the standby mode with reference to a standby target temperature, detects a user puff taken during the use session, and enters an operational mode in which greater thermal energy is supplied to the aerosol-forming substrate in response to the detected user puff to increase the temperature of the aerosol-forming substrate, and the temperature of the aerosol-forming substrate during the operational mode is controlled with reference to an operational target temperature higher than the standby target temperature.

Ex76. An aerosol generating device according to Ex75, wherein the device comprises one or more power sources, one or more heaters, and a controller, wherein the controller is configured to enter a standby mode at the start of the use session, detect the start of a user puff, switch from the standby mode to an operating mode in response to detecting the start of the user puff, detect the end of the user puff, and switch from the operating mode to the standby mode in response to detecting the end of the user puff.

Ex77. An aerosol generating device according to Ex75 or Ex76, wherein the controller increases the power supplied to one or more heaters during the operating mode relative to the standby mode.

Ex78. An aerosol generating device according to any one of Ex75 to Ex76, wherein the device comprises a first heater and a second heater, wherein the first heater is arranged to heat the aerosol-forming substrate during the standby mode, and the second heater is not arranged to heat the aerosol-forming substrate during the standby mode.

Ex79. An aerosol generating device according to any one of Ex75 to Ex78, wherein the device comprises a first heater and a second heater, and both the first heater and the second heater are arranged to heat the aerosol forming substrate during the operating mode.

Ex80. An aerosol generating device according to any one of Ex78 to Ex79, wherein the first heater is arranged to operate during the use session, and the second heater is arranged to operate during a user puff, for example, the second heater is switched on only during a user puff, or the power supplied to the second heater is increased during a user puff.

Ex81. An aerosol-generating system comprising an aerosol-generating device according to any one of the preceding embodiments and an aerosol-generating article comprising an aerosol-forming substrate, wherein the aerosol-generating article is configured to be at least partially contained within the aerosol-generating device.

Ex82. In Ex81, an aerosol-generating system comprising a plurality of components including an aerosol-forming substrate assembled within a wrapper.

Ex83. An aerosol-generating system according to Ex81 or Ex82, wherein the aerosol-generating article has a resistance to draw (RTD) of 10 mmH2O to 50 mmH2O.

Ex84. In Ex81 or Ex82, an aerosol-generating system wherein the system airflow path is defined through the device and the aerosol-generating article when the aerosol-generating article is contained within the device, for example, the system airflow path includes an airflow path defined through the device and an airflow path defined through the aerosol-generating article, for example, the system airflow path has a resistance to draw (RTD) of 20 mmH2O to 100 mmH2O.

Ex85. A method of generating an aerosol using an aerosol-generating device, the aerosol-generating device comprising a cavity for accommodating at least a portion of the aerosol-forming substrate, and an airflow path upstream of the cavity through which a user can draw air when using the device, the airflow path connecting the cavity with the external environment and including a pressure sensor positioned in communication with the airflow path upstream of the cavity, the method comprising the steps of: arranging an aerosol-forming substrate within the cavity; operating the device; detecting a pressure change in the airflow path associated with the initiation of a user puff; and detecting a user puff by detecting a pressure change in the airflow path associated with the end of the user puff.

Ex86. A method of generating an aerosol using an aerosol-generating device, the aerosol-generating device comprising a cavity for receiving at least a portion of the aerosol-forming substrate, and an airflow path upstream of the cavity through which a user can draw air when using the device, the airflow path connecting the cavity with the external environment, and including a pressure sensor positioned in communication with the airflow path upstream of the cavity, the method comprising the steps of: arranging an aerosol-forming substrate within the cavity; operating the device to operate in a standby mode; detecting a pressure change in the airflow path associated with the initiation of a user puff; switching an operating mode from the standby mode to an operating mode in response to the detected initiation of the user puff; detecting a pressure change in the airflow path associated with the termination of the user puff; and switching an operating mode from the operating mode to the standby mode in response to the detected termination of the user puff.

Ex87. A method of operating an aerosol using an aerosol-generating device, the aerosol-generating device comprising a cavity for accommodating at least a portion of the aerosol-forming substrate, and an airflow path upstream of the cavity through which a user can draw air when using the device, the airflow path connecting the cavity to the external environment, the method comprising the steps of: arranging an aerosol-forming substrate within the cavity; operating the device to operate in a standby mode in which the temperature of the aerosol-forming substrate is controlled with reference to an ambient target temperature; and, in response to a user puff, switching the operating mode from the standby mode to an operating mode in which the temperature of the aerosol-forming substrate is controlled with reference to an operating target temperature, wherein the operating target temperature is a temperature higher than the ambient target temperature.

Ex88. A method for generating an aerosol according to Ex85, Ex86, or Ex87 using a device as defined in any one of Examples Ex1 to Ex80, or a system as defined in any one of Examples Ex81 to Ex84.

The present invention will be further described, for purposes of example only, with reference to the accompanying drawings, in which:
Figure 1 shows a schematic cross-sectional view of a portion of an aerosol generating device;
Figure 2 shows the aerosol generating device of Figure 1 combined with an aerosol generating article;
FIG. 3 is a time/temperature plot illustrating the heating profile applied to the aerosol forming substrate using the device of FIG. 1;
FIG. 4 shows a schematic cross-sectional view of a portion of an aerosol generating device according to an embodiment of the present invention showing a pressure sensor positioned in the airflow path;
FIG. 5 shows a schematic cross-sectional view of a portion of an additional aerosol generating device according to an embodiment of the present invention showing a pressure sensor positioned in the airflow path;
FIG. 6 shows a schematic cross-sectional view of a portion of an aerosol generating device according to an embodiment of the present invention configured as a test device having an additional flow meter;
FIG. 7 shows a schematic diagram of a heater assembly for use in an aerosol generating device according to an embodiment of the present invention;
FIG. 8 shows a schematic cross-sectional view of a portion of an additional aerosol generating device according to one embodiment of the present invention including the heater assembly of FIG. 7;
FIG. 9 shows a schematic diagram of an additional heater assembly for use in an aerosol generating device according to an embodiment of the present invention;
FIG. 10 illustrates a schematic diagram of an additional aerosol generating device according to an embodiment of the present invention when combined with an aerosol generating article;
FIG. 11 shows a schematic cross-sectional view of an additional heater assembly for use in an aerosol generating device according to an embodiment of the present invention;
Figure 12 shows a schematic end projection of the heater assembly of Figure 11;
FIG. 13 shows a schematic cross-sectional view of an additional heater assembly for use in an aerosol generating device according to an embodiment of the present invention;
Figure 14 shows a schematic end projection of the heater assembly of Figure 13;
FIG. 15 shows a schematic cross-sectional view of an additional heater assembly for use in an aerosol generating device according to an embodiment of the present invention;
Figure 16 shows a schematic end projection of the heater assembly of Figure 15.

Figure 1 is a cross-sectional schematic drawing of a portion of an aerosol-generating device (1). The device (1) comprises an open end (12) through which a portion of an aerosol-generating article may be inserted into a heating chamber (2). The heating chamber (2), which may alternatively be referred to as a heating cavity, is dimensioned to accommodate a portion of a rod-shaped aerosol-generating article. The chamber (2) is defined by longitudinally extending walls (11), and a first heater (3) surrounds the walls (11) to provide thermal energy for heating the chamber (2) and any contents of the chamber. In an exemplary embodiment, the first heater is a resistive heater. The device defines an airflow path (6) leading from an inlet of the device into the chamber (2). A second heater (4) is positioned in the airflow path (6) upstream of the chamber (2). The second heater (4) is arranged to heat air drawn into the chamber (2) through the airflow path (6). The second heater (4) may provide a large heating surface area to efficiently heat the passing air. For example, the second heater (4) may include a plurality of heater plates (5) through which air is drawn. The second heater may include a highly porous heater body that acts as a heat exchanger.

The chamber (2), the first heater (3), the second heater (4), and the airflow path (6) are located within a housing (77). The housing also includes a power source, such as a battery, and a controller arranged to control the supply of power from the power source to the first and second heaters. Although the battery and the controller are not shown in FIG. 1, the arrangement of these components within the housing of an aerosol generating device is well known.

FIG. 2 illustrates portions of the same aerosol-generating device as illustrated in FIG. 1 with an aerosol-generating article (200) inserted into a chamber. The exemplary aerosol-generating article (200) illustrated in FIG. 2 comprises an aerosol-forming substrate (201) formed from a pleated sheet of homogenized tobacco, a hollow acetate tube (202) positioned immediately downstream of the aerosol-forming substrate, a free-flow filter (wide-bore tube) (203) positioned downstream of the hollow acetate tube, and a mouthpiece filter (204) positioned downstream of the free-flow filter. These components are arranged within a wrapper (205), for example, within a cigarette paper wrapper. This typical aerosol-generating article (200) resembles a conventional cigarette. In use, the front end or distal portion of the aerosol-generating article (200) is inserted into the chamber (2) of the aerosol-generating device (1) so that the aerosol-forming substrate (201) is positioned within the chamber (2). The mouth end or proximal end of the aerosol-generating article protrudes from the chamber (2), allowing the user to inhale the mouth end of the article (200). When the user inhales the mouth end of the article (200) positioned within the chamber (2), air is drawn into the inlet of the device, through the airflow path (6), through the second heater (4), into the chamber (2), through the aerosol-forming substrate (201) of the article (200), and into the user's mouth. When the aerosol-forming substrate is heated above the aerosolization temperature, volatile components of the aerosol-forming substrate may volatilize. These volatile components may be entrained in the airstream when the user inhales the article and may condense to form an inhalable aerosol that is consumed by the user.

In an exemplary method of use, an aerosol-generating article may be consumed during a use session using a dual heating mode regime. A chart illustrating such a heating profile is provided in FIG. 3 . When the article (200) is inserted into the chamber (2) of the device and a use session is initiated, the controller activates the first heater to heat the aerosol-forming substrate and controls the temperature of the aerosol-forming substrate at an ambient target temperature (310). The ambient target temperature (310) is a temperature below the aerosolization temperature of the aerosol-forming substrate. That is, the ambient temperature is below the temperature at which volatile components of the aerosol-forming substrate volatilize in significant amounts, and thus below the temperature at which an aerosol can be formed. Preferably, the ambient target temperature is only slightly lower than the aerosolization temperature of the substrate. For example, the ambient target temperature may be 170°C, in which case the temperature of the substrate is increased from ambient temperature to the ambient target temperature during the heating step (311). Once the substrate reaches the ambient target temperature, the power supply to the first heater is controlled to maintain the substrate temperature at the ambient target temperature. Therefore, the ambient target temperature may be referred to as the maintenance temperature, and the first heater may be referred to as the maintenance heater.

The temperature of the aerosol-forming substrate can be measured directly with a temperature sensor. Alternatively, the temperature of the substrate can be determined by monitoring electrical parameters of the heater, such as the resistance of the heater or the power supplied to the heater.

The second heater (4) may be activated at the start of a use session or may be activated only when the user takes a puff. When the user inhales the article (200), air is drawn through the airflow path (6) and the second heater (4). The air passing through the second heater (4) is heated, and then this heated air passes into the chamber (2) and through the aerosol-forming substrate (201). The aerosol-forming substrate is already maintained at the ambient target temperature. Heat from the incoming airflow provides a boost to the temperature of the aerosol-forming substrate, and the substrate (201) is heated almost immediately to a temperature higher than the ambient temperature. Therefore, the second heater (4) may be referred to as a boost heater. The temperature may be controlled to a second temperature higher than the ambient target temperature (310). This second temperature may also be referred to as an operating target temperature (320). The operating target temperature is a temperature higher than the aerosolization temperature for the aerosol-forming substrate. For example, the target operating temperature may be a temperature of 250°C, at which temperature the aerosol former and nicotine volatilize and an aerosol comprising these components may be formed.

Thus, the temperature of the aerosol-forming substrate is maintained at a temperature just below the aerosolization temperature using a maintenance heater, and then boosted to a temperature above the aerosolization temperature when the user takes a puff. This provides the advantage of allowing less aerosol-forming material to be used in the article, as the aerosol-forming component in the aerosol-forming substrate is depleted only when the user takes a puff. If the boost heater is activated only during the user puff, the dual-heating mode configuration can provide energy savings over the duration of the use session.

In the embodiments described with reference to FIGS. 1 to 3, the maintenance heater is a resistive heater surrounding the chamber (2), and the boost heater is a high surface area heater arranged in the airflow path upstream of the cavity. However, it is possible to provide a dual heating mode aerosol generating device having other heater configurations. For example, the boost heater may be a heater arranged to directly heat the chamber. For example, the boost heater may be an induction heater arranged to heat a susceptor in thermal contact with the aerosol-forming substrate. As a further example, the maintenance heater may surround the chamber, while the boost heater may be an internal heater designed to penetrate the aerosol-forming substrate. Either or both of the heaters may be induction heaters. In another variation, the maintenance heater may be a capacitive or dielectric heater that heats the substrate material with microwaves. Either or both of the heaters may be capacitive or dielectric heaters.

Figure 4 illustrates a portion of an aerosol generating device (1) as described above, further comprising a pressure sensor (7) positioned upstream of the second heater (4) in the airflow path (6). An exemplary and non-limiting implementation of the pressure sensor may be the STMicroelectronics LPS22HB, which is a compact piezoresistive absolute pressure sensor and is coupled to the controller of the device (1). The channel (80) extending from the air inlet (87) and defining the airflow path (6) has a larger cross-sectional area at the sensing section (9) where the pressure sensor (7) is positioned than at the restriction section (8) upstream of the sensing section (9). In this exemplary embodiment, the air inlet (87) has a transverse upstream cross-sectional area at section A1; the restriction section (8) has a transverse intermediate cross-sectional area at section A2; and the sensing section (9) has a transverse downstream cross-sectional area at section A3. The upstream cross-sectional area is larger than the intermediate cross-sectional area. The downstream cross-sectional area is larger than the intermediate cross-sectional area. The air inlet (87), the restriction (8), and the sensing portion (9) are continuous sections along the flow direction of the continuous airflow path (6). The restriction (8) of the channel (80) defining the airflow path (6) acts as a restriction of the airflow path, which causes a pressure drop at the sensing portion when the user inhales air through the airflow channel (80). Therefore, the restriction (8) can be referred to as a flow restrictor. This pressure drop can be detected by a pressure sensor, and this signal is transmitted to the controller to allow detection of the start and end of the user puff. The pressure drop due to the user puff is increased in the restricted area due to the increase in air velocity through the restriction. This increased pressure drop is easier to distinguish from background pressure changes, i.e., the increased pressure drop due to the restriction helps to raise the pressure signal due to the user puff above the background noise, which helps to enable detection of the user puff using a single sensor. Therefore, positioning the pressure sensor immediately downstream of the restriction in this manner increases the detection sensitivity of the user puff.

During use, an aerosol-generating article (200) is inserted into the chamber (2) and the device is activated. This initiates a use session. The first heater (3) is rapidly heated to its ambient operating target temperature, for example, 170°C as described above. The user then puffs or inhales through the mouthpiece (204) of the article (200). This causes airflow to be drawn through the device air inlet (87), through the flow restriction (8), through the second heater (4), through the article (200), and then into the user's mouth.

The flow restrictor (8) reduces the cross-sectional area of the device's airflow path. Therefore, when air flows through the flow restrictor (8), the airflow accelerates and the pressure decreases. The pressure drop created by the flow restrictor (8) is detected by the pressure sensor (7) of the puff detection device and transmitted to the device's controller continuously or at frequent intervals, such as every 50 milliseconds. A puff is detected when the pressure within the flow restrictor decreases by a significant amount.

In response to detecting a puff, the controller supplies power to the second heater (4). Air passing through the heater is heated to a temperature of about 250°C to 300°C. The heated air then passes through the aerosol-forming substrate (201) of the article (200), thereby increasing the temperature of the aerosol-forming substrate from the ambient target temperature of 170°C to the operating target temperature of 250°C. This heats the aerosol-forming substrate (201) above the aerosolization temperature of the aerosol-forming substrate (201) to form an aerosol.

Note that the secondary heater may be activated from the start of a usage session, in which case the controller may supply greater power to the secondary heater upon detection of a user puff.

When the pressure sensor (7) no longer detects a pressure drop in the airflow path, this may indicate that the puff has ended. Accordingly, the controller adjusts the power supplied to the second heater (4) to the value prior to the user puff. Since the aerosol-forming substrate no longer receives a heat boost from the stream of heated air, the temperature of the aerosol-forming substrate drops back to the ambient target temperature.

This process is repeated for each of a plurality of puffs during a use session until the use session ends, for example, after a predetermined number of puffs have been taken or after a predetermined duration from the start of the use session.

Figure 5 illustrates a portion of an aerosol generating device (501) having an alternative airflow path configuration. The device (501) is shown coupled to an aerosol generating article (200). The device (501) is substantially identical to the devices illustrated in Figures 1 to 4, with common components being given the same reference numerals as in Figure 5.

An air inlet (587) of the device (501) is defined by an opening into a channel (580) that defines an airflow path (506) upstream of the second heater (4). The air inlet (587) is located adjacent to the opening (12) of the chamber (2). The channel (580) extends along the length of the chamber and makes thermal contact with the first heater (3) before opening to the second heater (4) located upstream of the chamber (2). Air drawn into the airflow path (506) through the inlet (587) passes through the orifice plate (518), passes through the pressure sensor (507), enters the second heater (4), and then enters the chamber (2). The orifice plate (518) forms a restriction in the airflow path (506) that causes a detectable pressure drop at the location of the sensor (507) when a user takes a puff.

In use, the device (501) operates in the same manner as the device described above with respect to FIG. 4. Incoming air passing along the channel (580) is heated to some extent by the first heater (3), so that some of the heat energy that would otherwise be lost to the system is recovered from the air flowing through the device and transferred to the aerosol-forming substrate (201) of the article (200) located in the chamber (2).

Different aerosol-generating devices may present different resistance to draw (RTD) values. This can alter the overall RTD of the system (i.e., the RTD of the combined aerosol-generating device and aerosol-generating device). It may be desirable to adjust the pressure drop caused by the restriction to optimize puff detection for a particular system. Therefore, it may be desirable to provide a test device that allows optimal restriction dimensions to be determined and pressure sensors to be calibrated for a particular system.

Figure 6 illustrates a portion of a test aerosol-generating device (601) coupled with an aerosol-generating article (200). The device (601) is substantially identical to the device illustrated in Figure 4, with common components being given the same reference numerals in Figure 6. Accordingly, the device (601) comprises a chamber (2) for receiving the article (200). The chamber is heated by a first heater (3). A second heater (4) and a pressure sensor (7) are arranged in an airflow path (6) upstream of the chamber (2). A variable flow restrictor (618) is positioned upstream of the pressure sensor (7), and a flow meter (630) is positioned upstream of the variable flow restrictor (618). The variable flow restrictor comprises a screw thread that can be adjusted to vary the cross-sectional area of the airflow path at the restriction. It should be noted that many other types of variable flow restrictors, such as ball valves, gate valves, or butterfly valves, can be used. The flow meter is configured to measure the actual flow rate and volume through the airflow path as air is drawn through the system. Knowing the actual flow through the system allows the signal from the pressure sensor to be compensated. By using a variable restriction, the effect of different pressure drops on the sensitivity of the pressure sensor can be evaluated. Once the appropriate restriction dimensions are selected, an aerosol generating device can be manufactured with a fixed restriction and without the need for a flow meter.

In some specific embodiments, the first heater (maintenance heater) and the second heater (boost heater) may be combined into a single heater assembly. Figure 7 is a schematic diagram of a heater assembly that may be used in an aerosol-generating device according to an embodiment of the present invention. The heater assembly (712) includes a hollow portion (714) that partially defines a chamber (716) for receiving a portion of an aerosol-generating article. The chamber (716) includes an open end (718) into which the aerosol-generating article may be inserted and a closed end (720) opposite the open end (718). More specifically, the hollow portion (714) includes a tubular element (728) that partially defines a cylindrical wall (722) of the chamber (716) extending between the open end (718) and the closed end (720). The tubular element (728) is arranged such that the aerosol-generating article is received within the tubular element (728) and is in direct contact with the tubular element (728) when the aerosol-generating article is inserted into the chamber (716). Advantageously, the direct contact between the tubular element (728) and the aerosol-generating article facilitates heat transfer from the tubular element (728) to the aerosol-generating article. The tubular element is formed of a thermally conductive material, for example, a metallic material such as stainless steel.

The heater assembly further includes a body portion (730) that is permeable or allows airflow to pass through it. In certain embodiments, the body portion is a porous portion (730) that defines an airflow path (732) therethrough. The airflow path (732) is upstream of the chamber (716) and in fluid communication therewith. The porous portion (730) includes a porous plug (734) provided within the tubular element (728).

A first resistance heater (740) is arranged in contact with an outer surface (727) of a hollow body portion (714) of the heater assembly. The first resistance heater is electrically connected to power supply terminals (741, 742) to supply power to the heater (740). The first resistance heater (740) is arranged to provide maintenance heating to an aerosol-forming substrate positioned within the chamber (716) by maintaining the temperature of the substrate at an ambient target temperature lower than an aerosolization temperature for the substrate.

A second resistive heater (750) is arranged in contact with the outer surface (727) of the porous portion (730) of the heater assembly. The second resistive heater is electrically connected to power supply terminals (751, 752) to supply power to the heater (750). The second resistive heater is arranged to heat the porous plug (734) and any air flowing therethrough. The air heated in this manner provides a thermal boost to the aerosol-forming substrate positioned within the chamber (716) when the user takes a puff, thereby increasing the temperature of the substrate to an operating temperature higher than the aerosolization temperature for the substrate while the user takes a puff. Note that the same power supply may be used to power both the first and second resistive heaters. Alternatively, each heater may have a separate power supply.

FIG. 8 illustrates a portion of an aerosol generating device (800) including the heater assembly (712) of FIG. 7. The heater assembly (712) is positioned within a housing (810). A channel (805) defines an airflow path (806) leading from an air inlet (887) defined in the housing of the device through a porous plug (734) of the heater assembly (712) into a chamber (716). An orifice plate (818) is arranged within the airflow path downstream of the inlet to provide a restriction, and a pressure sensor (807) is positioned within the airflow path downstream of the restriction (818).

In use, the device (800) of FIG. 8 functions in the same manner as described above with respect to the device of FIG. 4. That is, a use session is initiated when an aerosol generating device is inserted into the chamber (716) and the device is activated. A first heater (740) heats the aerosol forming substrate (201) to an ambient operating target temperature, for example, 170° C. The user then puffs or inhales through the mouthpiece (204) of the article (200). This causes airflow to be drawn through the device air inlet (887), through the orifice plate (818), through the porous plug (734), through the article (200), and then into the user's mouth. A second heater (750) supplies heat to heat the porous plug (734). When the controller receives a signal from the pressure sensor (807) indicating that a user puff is occurring, power is supplied to the second heater (750). Heated air passing through the porous plug (734) raises the temperature of the aerosol forming substrate to an operating temperature at which aerosols can be generated.

The heater assembly (712) described in connection with FIG. 7 utilizes a resistive heater disposed on a surface of a conductive material. In some specific embodiments, the heater assembly may be manufactured by molding a conductive, resistive heating polymer. Electrodes may then be directly attached to portions of the heater assembly to heat those portions of the heater assembly. An example is illustrated in FIG. 9.

Figure 9 is a schematic diagram of a heater assembly (912) formed of a conductive and resistive heating polymer (901). The polymer (901) is a polymer composite comprising a polymer matrix and conductive filler particles. In a specific example, the polymer (901) comprises a polymer material and at least one particulate filler selected from the list consisting of graphite, graphite-derived materials, and hexagonal boron nitride, wherein the filler is dispersed within the polymer material. In a specific embodiment, the polymer material forming the matrix is polyether ether ketone (PEEK), but may alternatively be a liquid crystal polymer (LCP). The polymer (901) comprises the polymer material in an amount of 27 wt%, but this amount may range from 22% to 33%. The polymer (901) comprises the filler in an amount of 65 wt%, but this amount may range from 62% to 69%. The polymer (901) further comprises an additive, carbon black, dispersed within the polymer material. The polymer (901) contains additives in an amount of 7 wt%, but this can be between 5% and 9%.

A heater comprising a polymer matrix and conductive filler particles of at least one of graphite, graphite-derived material, and hexagonal boron nitride dispersed within the polymer matrix is generally easier to manufacture than similar heaters configured for resistive heating. In particular, the thermoplastic properties of the polymer matrix allow the polymer composite to be tailored for convenient processing, making the polymer composite suitable for precise and controlled molding. Accordingly, the described polymer (901) is easier to form into an elongated hollow shape compared to other conductive materials commonly used in heater assemblies of existing aerosol-generating devices. By controlling and adjusting the concentration and distribution of the conductive filler particles dispersed within the polymer matrix, it is possible to provide a polymer heater that is capable of generating sufficient heat by resistive heating to efficiently heat a solid aerosol-generating substrate of an aerosol-generating article that is advantageously thermally coupled to the heater. For example, by adjusting the formulation of the polymer matrix and the degree of dispersion of conductive filler particles within the polymer matrix, it is possible to control the conductivity of the resulting polymer, and consequently, the amount of heat generated by the heater assembly as a resistor when voltage is applied to the heater.

To form the heater assembly (912) illustrated in FIG. 9, a resistive heating polymer (901) is heated and extruded to form a hollow tube. This tube forms the outer portion (920) of the heater assembly (912). A granular polymer is then placed at one end of the tube and lightly sintered to form a porous plug (934) extending across one end of the tube. Preferably, the granular polymer particles sintered to form the porous plug have a number average particle diameter of less than 800 μm, for example, from 50 μm to 600 μm. Preferably, the cross-sectional porosity of the porous plug is greater than 15% and less than 45%. Preferably, the total pore volume of the porous plug is from 0.5 cm3 to 5 cm3, for example, from 2 cm3 to 3.5 cm3. Preferably, the porous plug provides a suction resistance of from 10 mm _H2O to 40 mm H2O, for example about 15 mm _H2O or about 20 mm _H2O .

The generated heater assembly (912) has an opening (918) at one end leading to a chamber (916) defined by an inner wall (922).

A first pair of electrodes (941, 942) attached to the heater assembly in the region of the cavity (916) allows current to pass through a portion of the wall of the heater assembly. Since the polymer (901) is resistively heatable, the act of passing current through the portion of the heater assembly causes the wall of the heater assembly to heat, thereby providing heat to an aerosol-generating substrate positioned within the cavity. Thus, the wall of the cavity (930) can act as a first heater to provide sustained heating to the substrate positioned within the cavity.

A second pair of electrodes (951, 952) attached to the heater assembly in the area of the porous plug (934) allows current to pass through that portion of the wall of the heater assembly. These electrodes allow the wall of the heater assembly and the porous plug to be resistively heated. Thus, the porous plug (934) can act as a second heater to heat air passing through the porous plug and provide a thermal boost to the aerosol-forming substrate when the user puffs.

A heater assembly as described in connection with FIG. 9 can be used as a heater assembly in the device (800) described in connection with FIG. 8.

Figure 10 illustrates a further specific example of a heater assembly (1012) that may be used in embodiments of the present invention. The heater assembly (1012) includes a hollow portion (1014) that partially defines a chamber (1016) for receiving a portion of an aerosol-generating article (200). The chamber (1016) includes an open end (1018) through which the aerosol-generating article (200) may be inserted into the chamber (1016) and a closed end (1020) opposite the open end (1018).

More specifically, the hollow body portion (1014) includes a tubular element (1028) that partially defines a cylindrical wall (1022) of a chamber (1016) extending between an open end (1018) and a closed end (1020). The tubular element (1028) is arranged such that when an aerosol-generating article is inserted into the chamber (1016), the aerosol-generating article is received within the tubular element (1028) and is in direct contact with the tubular element (1028). The tubular element is formed of a ceramic material, for example, alumina.

Protrusions (1019) extending from the inner wall (1022) of the cavity (1016) limit the extent to which an aerosol-generating article can be inserted into the chamber (1016). These protrusions allow a gap between the distal end of the aerosol-generating article and the porous plug (1034). For example, the gap may be between 1 mm and 5 mm, for example between 1.5 mm and 3 mm. The gap helps to thermally insulate the aerosol-generating article from the porous plug (1034) such that the porous plug only affects the temperature of the article when a user takes a puff.

The heater assembly further includes a porous portion (1030) defining an airflow path (1032) through the porous portion (1030). The airflow path (1032) is upstream of the chamber (1016) and in fluid communication with the chamber. The porous portion (1030) includes a porous plug (1034) provided within the tubular element (1028).

A first resistance heater (1040) is arranged within a tubular element (1028) in a hollow body portion (1014) of the heater assembly. The first resistance heater is electrically connected to power supply terminals (1041, 1042) to supply power to the heater (1040). The first resistance heater (1040) is arranged to provide maintenance heating to an aerosol-forming substrate positioned within the chamber (1016) by maintaining the temperature of the substrate at an ambient target temperature that is lower than an aerosolization temperature for the substrate.

A second resistive heater (1050) is arranged within the tubular element (1028) in the porous portion (1030) of the heater assembly. The second resistive heater is electrically connected to power supply terminals (1051, 1052) to supply power to the heater (1050). The second resistive heater is arranged to heat the porous plug (1034) and any air flowing therethrough. The air heated in this manner provides a thermal boost to the aerosol-forming substrate positioned within the chamber (1016) when the user takes a puff, thereby increasing the temperature of the substrate to an operating temperature higher than the aerosolization temperature for the substrate while the user takes a puff.

Figures 11 and 12 are schematic diagrams of additional specific examples of heater assemblies (1112) that may be used in embodiments of the present invention. The heater assembly (1112) is formed of a conductive and resistive heating polymer (901) formed of a polymer composite comprising a polymer matrix and conductive filler particles. The heater assembly (1112) is substantially identical to the heater assembly (912) described with respect to Figure 9, and similar features are given the same reference numerals as the assembly of Figure 9. A protrusion (1119) may be positioned within the chamber (916) to provide a gap between an aerosol-forming substrate inserted within the chamber and a porous plug (934) defining an end of the chamber.

The resistive heating polymer (901) of the heater assembly (1112) is heated by a current passing between a first annular contact (1141) disposed at a first end (1121) of the tubular outer portion (920) of the heater assembly and a second annular contact (1142) disposed at a second end (1122) of the tubular outer portion (920). The contacts (1141, 1142) may be copper rings attached to the heater body, for example, by mechanical interaction or by an overmolding process. A conductive adhesive may also be used to attach the contacts, for example, HT-carbon adhesive or silver epoxy adhesive may be used. The arrangement of the porous plug (934) spanning the second annular contact (1142), the tubular outer portion (920) of the heating assembly (112) and the second end (1122) of the heater assembly (1112) is illustrated in the end projection of the heater assembly (1112) as shown in FIG. 12.

In use, a voltage is applied between the first annular contact (1141) and the second annular contact (1142) to cause current to flow, which resistively heats the outer portion (920) of the heater assembly (1112). Heat from the heater assembly within the cavity area can heat an aerosol-forming substrate inserted within the cavity. Heat from the heater assembly within the area of the porous plug (934) can heat the porous plug. When a user puffs, the incoming air is heated as it passes through the porous plug (934) and provides a heat boost to the aerosol-forming substrate within the cavity.

Figures 13 and 14 illustrate alternative electrical connections for a heater assembly (1312) formed of a resistive heating polymer as described above. The heater assembly (1312) may include a first annular contact (1341) positioned at a first end (1321) of the heater assembly and a second contact (1342) embedded in a porous plug (934) portion of the heater assembly (1312). The second contact (1342) may include a plurality of branches (1343) to spread the electrical connection over a wide area of the porous plug (934). Operation of the heater assembly is substantially as described above with respect to Figures 11 and 12.

Figures 15 and 16 illustrate alternative electrical connections for a heater assembly (1412) formed of a resistive heating polymer as described above. Instead of contacts positioned at opposite ends (1421, 1422) of the heater assembly (1412), the assembly includes first contacts (1441) and second contacts (1442) positioned at radially opposite portions of a second end (1422) of the assembly. Current passed between the first contacts (1441) and the second contacts (1442) acts to resistively heat the heater assembly (1412) at the second end (1422) and to heat the porous plug (934). Heat generated at the second end (1422) of the heater assembly is conducted toward the first end (1421) of the heater assembly (1412). Thus, the heat transferred toward the first end (1421) of the heater assembly can be used to provide sustained heating to the aerosol forming substrate positioned within the cavity (916). The electrical configuration illustrated in FIGS. 15 and 16 allows the porous plug to be heated to a higher temperature than the portion of the heater assembly defining the chamber (916).

For the purposes of this description and the appended claims, unless otherwise indicated, all numbers expressing quantities, amounts, percentages, and the like will be understood to be modified in all instances by the term "about." Furthermore, all ranges are inclusive of the disclosed maximum and minimum points, and include therein any intermediate ranges that may or may not be specifically enumerated herein. Thus, in this context, the number A is understood as A plus or minus ten percent (10%) of A. Within this context, the number A may be considered to include a numerical value that is within the normal standard error for measurement of the property that the number A describes. In some instances used in the appended claims, the number A may deviate by the above-recited percentages, provided that the amount by which A deviates does not materially affect the basic and novel characteristics(s) of the claimed invention. Furthermore, all ranges are inclusive of the disclosed maximum and minimum points, and include therein any intermediate ranges that may or may not be specifically enumerated herein.

Claims (15)

An aerosol generating device configured to generate an aerosol from an aerosol forming substrate,
The device defines a cavity for receiving at least a portion of the aerosol-forming substrate, and an airflow path upstream of the cavity through which a user can draw air when using the device, the airflow path connecting the cavity with the external environment;
The airflow path includes an upstream section having an upstream cross-sectional area, a middle section having an intermediate cross-sectional area, and a downstream section having a downstream cross-sectional area,
The above upstream cross-sectional area is larger than the above intermediate cross-sectional area,
The above downstream cross-sectional area is larger than the above intermediate cross-sectional area,
An aerosol generating device, wherein the device comprises a pressure sensor positioned within a downstream section of the airflow path upstream of the cavity, and wherein the device is configured to detect one or more user puffs taken during use of the device using a signal from the pressure sensor. An aerosol generating device in accordance with claim 1, wherein the airflow path upstream of the cavity acts as a flow restrictor or includes a flow restrictor. An aerosol generating device in claim 2, wherein the flow restrictor comprises a mechanical element positioned within the airflow path, for example, an orifice plate positioned within the airflow path. An aerosol generating device according to claim 2 or 3, wherein the flow restrictor is a variable flow restrictor, for example, the flow restrictor is an adjustable valve. An aerosol generating device according to any one of claims 1 to 4, wherein a portion of the airflow path upstream of the cavity has a cross-sectional area of less than 0.5 mm ² , for example less than 0.4 mm ² . An aerosol generating device according to any one of claims 1 to 5, wherein the airflow path upstream of the cavity has a resistance to draw (RTD) of 10 mmH ₂ O to 50 mmH ₂ O. An aerosol generating device according to any one of claims 1 to 6, wherein the device is configured to generate an aerosol from an aerosol-forming substrate during a use session having a use session start and a use session end, and wherein the device is configured to detect one or more user puffs taken during the use session. An aerosol-generating device according to any one of claims 1 to 7, wherein the device is configured to distinguish between a puff period and a non-puff period, wherein the puff period is defined as any period during a use session when the user actively takes a puff, and the non-puff period is defined as any period during the use session when the user does not actively take a puff. An aerosol-generating device according to any one of claims 1 to 8, wherein the device is configured to characterize user puffs taken during use, for example, each puff taken during a use session. An aerosol generating device according to claim 9, wherein the device is configured to characterize detected user puffs taken during the use session, for example, each detected user puff taken during the use session. An aerosol generating device according to claim 9 or 10, wherein the device is configured to determine a volume of aerosol generated during said or each user puff, for example, during each user puff taken during said use session. An aerosol generating device according to any one of claims 1 to 11, wherein the pressure sensor detects a change in flow in an airflow path as a result of a user taking a puff, for example, wherein the puff includes the user drawing air through a portion of the device along an airflow path, and the pressure sensor detects a change in pressure in the airflow path as a result of the user taking a puff. An aerosol generating device according to any one of claims 1 to 12, wherein the device is configured to heat the aerosol-forming substrate during a use session with reference to two different target temperatures, an ambient target temperature and an operating target temperature, wherein the ambient target temperature is a temperature higher than room temperature and the operating target temperature is a temperature higher than the ambient target temperature, and wherein a signal from a pressure sensor is used to determine which of the ambient target temperature or the operating target temperature is used to control the temperature of the aerosol-forming substrate. An aerosol-generating system comprising an aerosol-generating device and an aerosol-forming substrate according to any one of claims 1 to 13, wherein the aerosol-generating device is configured to be at least partially contained within the aerosol-generating device. A method for generating an aerosol using an aerosol generating device, wherein the aerosol generating device comprises:
a cavity for accommodating at least a portion of the aerosol-forming substrate, and an airflow path upstream of the cavity through which a user can draw air when using the device, the airflow path connecting the cavity with the external environment, and
Including a pressure sensor positioned in communication with the airflow path upstream of the above cavity, wherein the method comprises:
A step of arranging an aerosol forming substrate within the above cavity,
Steps for operating the above device,
a step of detecting a pressure change in the airflow path associated with the start of the user puff, and
A method comprising the step of detecting a user puff by detecting a pressure change in the airflow path associated with the termination of the user puff.