Aerosol generating device, and system and method for controlling same

Abstract

An aerosol generating device and a method of controlling aerosol generation in an aerosol generating device are provided, the method comprising receiving an aerosol-generating article by a heating chamber of the aerosol generating device, the aerosol-forming substrate of the aerosol-generating article having a total aerosol former content of greater than 30 weight percent, the aerosol-forming substrate being a solid or a gel, and heating the aerosol-forming substrate to form an aerosol for inhalation by a user by increasing the temperature of a heating element from an initial temperature to a first temperature and controlling power to maintain the temperature of the heating element constant at the first temperature for the duration of a first predetermined period, the first temperature being between 245 degrees Celsius and 285 degrees Celsius.

Description

[Technical field]

[0001] The present disclosure relates to a method of controlling aerosol generation in an aerosol generating device configured to heat an aerosol-generating article comprising a solid or gel aerosol-forming substrate, and also to a system comprising the aerosol generating device and the aerosol-generating article. [Background technology]

[0002] The aerosol generating device may comprise an electrically operated heat source configured to heat an aerosol generating article including an aerosol-forming substrate to generate an aerosol. Typically, in a heated aerosol generating article, the aerosol is generated by the transfer of heat from the heat source to a physically separate aerosol-forming substrate. In use, volatile compounds are released from the aerosol-forming substrate by the transfer of heat from the heat source to the aerosol-forming substrate and are entrained in air drawn through the aerosol-generating article. As the released compounds cool, they condense to form an aerosol that is inhaled by the user.

[0003] A number of handheld aerosol generating devices configured to heat an aerosol-forming substrate of a heated aerosol-generating article are known in the art. Such devices include electrically operated aerosol generating devices in which an aerosol is generated by heat transfer from one or more electric heating elements of the aerosol generating device to the aerosol-forming substrate of the heated aerosol-generating article. Known handheld electrically operated aerosol generating devices typically comprise a battery, control electronics, and one or more electric heating elements for heating the aerosol-forming substrate of the heated aerosol-generating article.

[0004] It is desirable to provide an aerosol generating device and a method of controlling aerosol production in an aerosol generating device whereby a large amount of volatile compounds are delivered to the user from the first puff, and where good delivery of volatile compounds is maintained throughout the user experience. Summary of the Invention

[0005] According to one embodiment, there is provided a method of controlling aerosol generation in an aerosol generating device. The device comprises a heating chamber configured to at least partially receive an aerosol-generating article including an aerosol-forming substrate, a heating system associated with a heating element configured to internally heat the aerosol-forming substrate from within the aerosol-forming substrate, and a power source for providing power to the heating system. The method includes receiving the aerosol-generating article by the heating chamber, the aerosol-forming substrate having a total aerosol former content greater than 30 weight percent, the aerosol-forming substrate being a solid or a gel, and heating the aerosol-forming substrate to form an aerosol for inhalation by a user by increasing a temperature of the heating element from an initial temperature to a first temperature and controlling the power to maintain the temperature of the heating element constant at the first temperature for the duration of a first predetermined period, the first temperature being between 245 degrees Celsius and 285 degrees Celsius.

[0006] By heating the heating element to a temperature within this range for a first predetermined period of time, the thermal inertia of the aerosol-forming substrate is overcome and the amount of desired volatile compounds vaporized in the aerosol inhaled by the user is improved from the first puff.

[0007] As used herein in connection with the present invention, the term "aerosol-generating device" is used to describe a device that interacts with an aerosol-forming substrate of an aerosol-generating article to generate an aerosol. The aerosol-generating device may be a hand-held, electrically operated device.

[0008] As used herein in connection with the present invention, the term "aerosol-generating article" is used to describe an article that includes an aerosol-forming substrate that is heated to generate an inhalable aerosol for delivery to a user. The aerosol-generating article may be disposable.

[0009] As used herein in connection with the present invention, the term "aerosol" is used to describe a dispersion of solid particles, or liquid droplets, or a combination of solid particles and liquid droplets, in a gas. Aerosols can be visible or invisible. Aerosols may include not only vapors of substances that are normally liquids or solids at room temperature, but also solid particles or liquid droplets, or a combination of solid particles and liquid droplets.

[0010] As used herein in connection with the present invention, the term "aerosol-forming substrate" is used to describe a substrate that includes an aerosol-generating material that is capable of releasing, upon heating, a volatile compound capable of generating an aerosol.

[0011] The power source is preferably a battery, such as a lithium ion battery. Alternatively, the power source may be another form of charge storage device, such as a capacitor. The power source may require recharging. For example, the power source may have a capacity sufficient to allow continuous generation of aerosol for approximately six minutes, or a multiple of six minutes. In another example, the power source may have a capacity sufficient to allow a predetermined number of puffs, or discontinuous activation of the heating system.

[0012] As used herein in connection with the present invention, the term "aerosol former" is used to describe a compound that facilitates the formation of an aerosol during use and that is preferably substantially resistant to thermal decomposition at the operating temperatures of an aerosol-generating article or an aerosol-generating system that includes the aerosol-forming substrate.

[0013] As used herein with respect to the present invention, the term "total aerosol former content" is used to describe the combined content of all aerosol formers in an aerosol-forming substrate.

[0014] Unless otherwise stated, the weight percentages of the components of the aerosol-forming substrate listed herein are based on the dry weight of the aerosol-forming substrate.

[0015] As used herein in connection with the present invention, the term "solid" is used to describe an aerosol-forming substrate that has a stable size and shape and does not flow at 23°C.

[0016] As used herein in connection with the present invention, the term "gel" is used to describe an aerosol-forming substrate that contains two or more components, one of which is a liquid. Gels are predominantly liquid by weight. Gels are substantially dilute crosslinked systems that do not exhibit flow when at steady state, although the liquid phase can still diffuse throughout the system.

[0017] The first period may have a duration of from 40 seconds to 300 seconds, preferably from 40 seconds to 150 seconds.

[0018] Controlling the power may further include adjusting the temperature of the heating element to a second temperature for a second predetermined period of time, the second predetermined period of time following the first predetermined period of time.

[0019] The second predetermined period may directly follow the first predetermined period.

[0020] The second temperature may be different from the first temperature.

[0021] The second temperature may be lower than the first temperature.

[0022] By reducing the temperature of the heating element in the second heating mode, the amount of vaporized desired volatile compounds in the aerosol inhaled by the user remains consistent with the amount during the first predetermined period, thereby providing the same sensory experience to the user.

[0023] The second temperature may be between 190 and 220 degrees Celsius.

[0024] Adjusting the temperature of the heating element to the second temperature during the second period of time can include two successive temperature steps.

[0025] The temperature of the first temperature step may be lower than the temperature of the second temperature step.

[0026] Having two temperature steps in the second heating mode allows for improved control of the amount of vaporized desired volatile compound in the aerosol inhaled by the user, thereby providing the same sensory experience to the user. Furthermore, if the temperature of the second heating step is higher than the temperature of the first heating step, the amount of vaporized desired volatile compound remains consistent even as the amount of desired volatile compound depletes over time with heating.

[0027] Adjusting the temperature of the heating element to a second temperature during the second predetermined period of time may include increasing the temperature of the heating element from the first temperature.

[0028] The second predetermined period may have a duration of 100 to 280 seconds.

[0029] Controlling the power may further include adjusting the temperature of the heating element to a third temperature for a third predetermined period of time, the third predetermined period of time following the second predetermined period of time.

[0030] The third temperature may correspond approximately to the first temperature.

[0031] By carrying out heating of the aerosol-forming substrate in three predetermined periods during which the temperature of the heating element is adjusted to each temperature to form an aerosol for the user to inhale, improved control of aerosol delivery is possible. In particular, toward the end of the user session in the third predetermined period, the amount of vaporized desired volatile compound for the user to inhale will be depleted. By increasing the temperature of the heating element to about the first temperature, the amount of vaporized desired volatile compound in the aerosol inhaled by the user can remain consistent with the amount during the first and second predetermined periods.

[0032] The third predetermined period may have a duration between 30 seconds and 120 seconds. The third predetermined period may directly follow the second predetermined period.

[0033] The power may be controlled based on a heating profile of a plurality of heating profiles, each heating profile defining how to regulate the temperature of the heating element during each of the time periods.

[0034] The method may further include selecting a heating profile based on the identity of the aerosol-generating article.

[0035] The power may be controlled based on a heating profile of a plurality of heating profiles, each heating profile may define how to regulate the temperature of the heating element during the second time period.

[0036] The method may further include selecting a heating profile based on the identity of the aerosol-generating article.

[0037] The heating system may include an induction coil configured to inductively heat the heating element.

[0038] As used herein, the term "inductively heat" refers to the heating of a heating element, such as a susceptor, when penetrated by an alternating magnetic field. The heating may be caused by the generation of eddy currents in the heating element. The heating may also be caused by magnetic hysteresis losses.

[0039] The heating element may be a susceptor. As used herein, the term "susceptor" refers to an element that includes a material capable of converting the energy of a magnetic field into heat. When the susceptor is located in an alternating magnetic field, the susceptor heats up. The heating of the susceptor may be the result of at least one of hysteresis losses and eddy currents induced in the susceptor, depending on the electrical and magnetic properties of the susceptor material. The susceptor may be an elongated susceptor. The term "elongated" as used herein in connection with the present invention is used to describe a susceptor that has a length that is greater than its width. For example, the length of the susceptor may be at least twice its width.

[0040] The method may further include controlling the power to raise the temperature of the heating element from the ambient temperature to the initial temperature during a pre-heat period before the first predetermined period.

[0041] The preheat period may have a duration of 10 to 20 seconds.

[0042] The pre-heating period ensures that the duration of the aerosol-forming substrate is sufficient for the substrate to reach a minimum operating temperature, regardless of the physical state of the substrate (e.g., dry or wet), in order to be ready to provide continuous power and reach the first operating temperature as quickly as possible to generate sufficient aerosol for the user to inhale. This is particularly advantageous for aerosol-forming substrates having a high aerosol former content (greater than 30 weight percent) since such substrates typically have a high moisture content after reaching thermal equilibrium.

[0043] The method may further include calibrating the heating element following the pre-heat period and prior to the first predetermined period.

[0044] Calibrating the heating element during heating of the aerosol-forming substrate to generate the aerosol (rather than during manufacture) advantageously provides a more accurate determination of the calibration values ​​used in temperature control, and thus improved temperature control is achieved.

[0045] The heating system may further comprise a heating element which is a resistive heating element.

[0046] The method may further include controlling the power to raise the temperature of the heating element from the ambient temperature to the initial temperature during a pre-heat period before the first predetermined period.

[0047] The preheat period may have a duration of 10 to 20 seconds.

[0048] The pre-heating period ensures that the duration of the aerosol-forming substrate is sufficient for the substrate to reach a minimum operating temperature, regardless of the physical state of the substrate (e.g., dry or wet), in order to be ready to provide continuous power and reach the first operating temperature as quickly as possible to generate sufficient aerosol for the user to inhale. This is particularly advantageous for aerosol-forming substrates having a high aerosol former content (greater than 30 weight percent) since such substrates typically have a high moisture content after reaching thermal equilibrium.

[0049] The aerosol-forming substrate may comprise a total aerosol former content of greater than 35 weight percent.The aerosol-forming substrate may comprise a total aerosol former content of greater than 40 weight percent.The aerosol-forming substrate may comprise a total aerosol former content of greater than 45 weight percent.

[0050] The aerosol-forming substrate may comprise one or more aerosol formers selected from 1,3-butanediol, glycerin, 1,3-propanediol, propylene glycol, triethylene glycol, glycerol monoacetate, glycerol diacetate, glycerol triacetate, dimethyl dodecanedioate, and dimethyl tetradecanedioate.

[0051] The aerosol-forming substrate may be tobacco-free.

[0052] The aerosol-forming substrate may further comprise nicotine.

[0053] As used herein in connection with the present invention, the term "nicotine" is used to describe nicotine, nicotine base, or nicotine salts. In embodiments in which the aerosol-forming substrate comprises nicotine base or nicotine salts, the amount of nicotine recited herein is the amount of free base nicotine or the amount of protonated nicotine, respectively.

[0054] The aerosol-forming substrate may comprise natural nicotine, or synthetic nicotine, or a combination of natural and synthetic nicotine.

[0055] The aerosol-forming substrate may further comprise one or more cellulosic agents and one or more carboxylic acids selected from fumaric acid, maleic acid, and malic acid.

[0056] The aerosol-forming substrate may have a total cellulosic agent content of at least 35 weight percent, and a total carboxylic acid content of at least 0.5 weight percent.

[0057] The term "cellulosic agent" as used herein in connection with the present invention is used to describe a cellulosic material. Examples of cellulosic agents include cellulosic film formers, cellulosic reinforcing agents, and cellulosic binders. For example, when an aerosol-forming substrate includes a plurality of cellulosic agents consisting of a cellulosic film former, a cellulosic reinforcing agent, and a cellulosic binder, the term "total cellulosic agent content" describes the total content of the cellulosic film former, the cellulosic reinforcing agent, and the cellulosic binder of the aerosol-forming substrate.

[0058] The term "total carboxylic acid content" as used herein in connection with the present invention is used to describe the combined content of all carboxylic acids in the aerosol-forming substrate. For example, if the aerosol-forming substrate comprises a plurality of carboxylic acids consisting of benzoic acid and fumaric acid, the term "total carboxylic acid content" describes the combined combined benzoic acid and fumaric acid content of the aerosol-forming substrate.

[0059] The aerosol-forming substrate may comprise water.

[0060] The aerosol-forming substrate may have a water content of from 5 percent to 35 percent by weight.

[0061] The aerosol-forming substrate may be a solid film.

[0062] As used herein in connection with the present invention, the term "film" is used to describe a solid aerosol-forming substrate having a thickness that is substantially less than its width or length.

[0063] As used herein in connection with the present invention, the term "thickness" is used to describe the smallest dimension between substantially parallel opposing surfaces of a solid aerosol-generating film.

[0064] According to a further embodiment, there is provided an aerosol-generating article comprising an aerosol-forming substrate having a total aerosol former content of 30 weight percent or more, the aerosol former substrate being a solid or gel, and an aerosol generating device comprising a heating chamber configured to at least partially receive the aerosol-generating article, a heating system associated with a heating element configured to internally heat the aerosol-forming substrate from within the aerosol-forming substrate, a power source for providing power to the heating system, and a controller configured to control the power during heating of the aerosol-forming substrate to increase the temperature of the heating element from an initial temperature to a first temperature and to maintain the temperature of the heating element constant at the first temperature for the duration of a first predetermined period to form an aerosol for inhalation by a user, the first temperature being between 245 degrees Celsius and 285 degrees Celsius.

[0065] The first period may have a duration of from 40 seconds to 300 seconds, preferably from 40 seconds to 150 seconds.

[0066] Controlling the power during heating of the aerosol-forming substrate to form an aerosol for inhalation by the user may further include adjusting the temperature of the heating element to a second temperature for a second predetermined period of time, the second predetermined period of time following the first predetermined period of time.

[0067] The second predetermined period may directly follow the first predetermined period.

[0068] The second temperature may be different from the first temperature.

[0069] The second temperature may be lower than the first temperature.

[0070] The second temperature may be between 190 and 220 degrees Celsius.

[0071] Adjusting the temperature of the heating element to the second temperature during the second predetermined period may include two successive temperature steps.

[0072] The temperature of the first temperature step may be lower than the temperature of the second temperature step.

[0073] Adjusting the temperature of the heating element to a second temperature during the second predetermined period of time may include increasing the temperature of the heating element from the first temperature.

[0074] The second predetermined period may have a duration of 100 to 280 seconds.

[0075] Controlling the power during heating of the aerosol-forming substrate to form an aerosol for inhalation by the user may further include adjusting the temperature of the heating element to a third temperature for a third predetermined period of time, which may follow the second predetermined period of time.

[0076] The third temperature may correspond approximately to the first temperature.

[0077] The third predetermined period may directly follow the second predetermined period.

[0078] The third predetermined period may have a duration between 30 seconds and 120 seconds.

[0079] The aerosol generating device may further comprise a memory configured to store a plurality of heating profiles, each heating profile may define how to adjust the temperature of the heating element during each of the time periods, and the controller may be further configured to control the power during heating of the aerosol-forming substrate to form an aerosol for inhalation by a user based on a heating profile of the plurality of heating profiles.

[0080] The controller may be further configured to select the heating profile based on an identity of the aerosol-generating article.

[0081] The aerosol generating device may further comprise a memory configured to store a plurality of heating profiles, each heating profile may define a manner of adjusting the temperature of the heating element during a second predetermined period of time, and the controller may be further configured to control power during heating of the aerosol-forming substrate to form an aerosol for inhalation by a user based on a heating profile of the plurality of heating profiles.

[0082] The controller may be further configured to select the heating profile based on an identity of the aerosol-generating article.

[0083] The aerosol-forming substrate may further comprise a heating element and the heating system may comprise an induction coil for inductively heating the heating element.

[0084] The controller may be further configured to control the power to raise the temperature of the heating element from an ambient temperature to an initial temperature during a pre-heat period before the first predetermined period.

[0085] The preheat period may have a duration of 10 to 20 seconds.

[0086] The controller may be further configured to calibrate the heating element following the pre-heat period and prior to the first period.

[0087] The heating system may include a heating element, which is a resistive heating element.

[0088] The controller may be further configured to control the power to raise the temperature of the heating element from an ambient temperature to an initial temperature during a pre-heat period before the first predetermined period.

[0089] The preheat period may have a duration of 10 to 20 seconds.

[0090] The aerosol-forming substrate may comprise a total aerosol former content of greater than 35 weight percent.

[0091] The aerosol-forming substrate may contain a total aerosol former content of greater than 40 weight percent.

[0092] The aerosol-forming substrate may comprise a total aerosol former content of greater than 45 weight percent.

[0093] The aerosol-forming substrate may comprise one or more aerosol formers selected from 1,3-butanediol, glycerin, 1,3-propanediol, propylene glycol, triethylene glycol, glycerol monoacetate, glycerol diacetate, glycerol triacetate, dimethyl dodecanedioate, and dimethyl tetradecanedioate.

[0094] The aerosol-forming substrate may be tobacco-free.

[0095] The aerosol-forming substrate may further comprise nicotine.

[0096] The aerosol-forming substrate may further comprise one or more cellulosic agents and one or more carboxylic acids selected from fumaric acid, maleic acid, and malic acid.

[0097] The aerosol-forming substrate may have a total cellulosic agent content of at least 35 weight percent, and a total carboxylic acid content of at least 0.5 weight percent.

[0098] The aerosol-forming substrate may comprise water.

[0099] The aerosol-forming substrate may have a water content of from 5 percent to 35 percent by weight.

[0100] As used herein, the terms "puffing" and "inhalation" are used interchangeably and are intended to mean the action of a user drawing an aerosol into their body through their mouth or nose. Inhalation includes situations where the aerosol is drawn into the user's lungs, as well as situations where the aerosol is drawn only into the user's mouth or nasal passages before being expelled from the user's body.

[0101] As used herein, a "use session" refers to a period of use of a device beginning with activation of the device by a user. A use session may include a pre-heating phase in which the aerosol generating device is configured to supply power to a heating system to heat an aerosol-forming substrate to generate an aerosol. A use session may include a calibration phase for calibrating the heating system to more precisely control the temperature of the heating element. A use session may include a main phase in which a user may inhale the generated aerosol. The main phase may be sufficiently long for multiple puffs. The main phase may be sufficiently long for three, four, five, or six puffs. The main phase may be sufficiently long for seven or more puffs. At the end of the use phase, the aerosol generating device may be configured to stop supplying power to the heating system. The aerosol-forming substrate may be removed from the aerosol generating device at the end of the use session. The aerosol-forming substrate may be replaced in a subsequent use session. The duration of the use session between the start of the use session and the end of the use session may be at least one, two, three, four, five, or six minutes. Preferably, a usage session may have a duration of about a quarter of a minute.

[0102] As used herein in referring to an aerosol generating device, the terms "upstream" and "forward," as well as "downstream" and "rearward," are used to describe the relative locations of components, or portions of components, of the aerosol generating device in relation to the direction in which air flows through the aerosol generating device during use. An aerosol generating device according to the invention comprises a proximal end through which aerosol exits the device during use. The proximal end of the aerosol generating device may also be referred to as the mouth end or downstream end. The mouth end is downstream of the distal end. The distal end of the aerosol-generating article may also be referred to as the upstream end. Components or portions of components of an aerosol generating device may be described as being upstream or downstream of one another based on their relative location with respect to the airflow path of the aerosol generating device.

[0103] As used herein in referring to an aerosol-generating article, the terms "upstream" and "forward," as well as "downstream" and "rearward" are used to describe the relative positions of components or parts of components of the aerosol-generating article in relation to the direction in which air flows through the aerosol-generating article during use of the aerosol-generating article. The aerosol-generating article according to the present invention comprises a proximal end through which the aerosol exits the article during use. The proximal end of the aerosol-generating article may also be referred to as the mouth end or the downstream end. The mouth end is downstream of the distal end. The distal end of the aerosol-generating article may also be referred to as the upstream end. Components or parts of components of the aerosol-generating article may be described as being upstream or downstream of each other based on their relative positions between the proximal end of the aerosol-generating article and the distal end of the aerosol-generating article. The forward of a component or part of a component of the aerosol-generating article is the part that is at the end closest to the upstream end of the aerosol-generating article. The rearward of a component or part of a component of the aerosol-generating article is the part that is at the end closest to the downstream end of the aerosol-generating article.

[0104] As used herein, "aerosol cooling element" refers to a component of an aerosol-generating article that is located downstream of an aerosol-forming substrate such that, during use, the aerosol formed by the volatile compounds emitted from the aerosol-forming substrate passes through and is cooled by the aerosol cooling element before being inhaled by the user. Aerosol cooling elements have a large surface area but generate a low pressure drop. Filters and other mouthpieces that generate a high pressure drop (e.g., filters formed of fiber bundles) are not considered aerosol cooling elements. Chambers and cavities within an aerosol-generating article are not considered aerosol cooling elements.

[0105] As used herein, the term "mouthpiece" means that portion of an aerosol-generating article, device, or system that is placed into the mouth of a user for direct inhalation of the aerosol.

[0106] As used herein with reference to the present invention, the term "mode" refers to an operating mode that the controller is programmed to implement. For example, in a calibration mode, the controller is configured to implement a preprogrammed calibration process. In a preheat mode, the controller is configured to implement a preprogrammed preheat process. In a heating mode, the controller is configured to implement a heating process. The term "phase" may be used interchangeably herein with the term "mode." The controller may include a microcontroller. The controller may comprise a microprocessor, such as a programmable microprocessor. The controller may comprise a non-volatile memory. The aerosol generating device may comprise an interface configured to allow the transfer of data from an external device to and from the controller. The interface may allow the uploading of software to the controller that runs on the programmable microprocessor. The interface may be a wired interface, such as a micro USB port, or a wireless interface. EXAMPLES

[0107] The present invention is defined in the claims. However, below is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of the other examples, embodiments, or aspects described herein.

[0108] Example 1: 1. A method of controlling aerosol generation in an aerosol generating device, the device comprising: a heating chamber configured to at least partially receive an aerosol-generating article comprising an aerosol-forming substrate; a heating system associated with a heating element configured to internally heat the aerosol-forming substrate from within the aerosol-forming substrate; and a power source for providing power to the heating system, the method comprising: receiving the aerosol-generating article by the heating chamber, the aerosol-forming substrate having a total aerosol former content greater than 30 weight percent, the aerosol-forming substrate being a solid or a gel; and heating the aerosol-forming substrate to form an aerosol for inhalation by a user by increasing a temperature of the heating element from an initial temperature to a first temperature and controlling the power to maintain said temperature of the heating element constant at the first temperature for the duration of a first predetermined period of time, the first temperature being between 245 degrees Celsius and 285 degrees Celsius. Example 2: The method according to example 1, wherein the first period has a duration of from 40 seconds to 300 seconds, preferably from 40 seconds to 150 seconds. Example 3: The method according to example 1 or 2, wherein controlling the power further comprises adjusting the temperature of the heating element to a second temperature for a second predetermined period of time, the second predetermined period of time following the first predetermined period of time. Example 4: The method according to example 3, wherein the second temperature is different from the first temperature. Example 5: The process according to example 3 or 4, wherein the second temperature is lower than the first temperature. Example 6: The method according to example 5, wherein the second temperature is between 190 and 220 degrees Celsius. Example 7: The method according to any one of examples 3-6, wherein adjusting the temperature of the heating element to the second temperature during the second period of time comprises two successive temperature steps. Example 8: The method according to example 7, wherein the temperature of the first temperature step is lower than the temperature of the second temperature step. Example 9: The method according to example 3 or 4, wherein adjusting the temperature of the heating element to the second temperature during the second predetermined period of time includes increasing the temperature of the heating element from the first temperature. Example 10: The method according to any one of embodiments 3-9, wherein the duration of the second predetermined period is from 100 to 280 seconds. Example 11: The method according to any one of Examples 3-10, wherein controlling the power further comprises adjusting the temperature of the heating element to a third temperature for a third predetermined period of time, the third predetermined period of time following the second predetermined period of time. Example 12: The method according to example 11, wherein the third temperature corresponds approximately to the first temperature. Example 13: 13. The method according to example 11 or 12, wherein the duration of the third predetermined period is between 30 seconds and 120 seconds. Example 14: The method according to any one of Examples 3-13, wherein the power is controlled based on a heating profile of a plurality of heating profiles, each heating profile defining how to regulate the temperature of the heating element during each of the time periods. Example 15: The method according to example 14, further comprising selecting a heating profile based on the identity of the aerosol-generating article. Example 16: The method according to any one of Examples 3-13, wherein the power is controlled based on a heating profile of a plurality of heating profiles, each heating profile defining a manner of adjusting the temperature of the heating element during the second period of time. Example 17: The method according to example 16, further comprising selecting a heating profile based on the identity of the aerosol-generating article. Example 18: The method according to any one of Examples 1-17, wherein the heating system comprises an induction coil configured to inductively heat the heating element. Example 19: The method according to any one of examples 1-18, wherein the method further comprises controlling power to raise the temperature of the heating element from the ambient temperature to the initial temperature during a pre-heating period before the first predetermined period. Example 20: The method according to example 19, wherein the preheat period has a duration of 10 to 20 seconds. Example 21: The method according to one of examples 19 or 20, further comprising calibrating the heating element following the preheat period and prior to the first predetermined period. Example 22: The method according to any one of the preceding embodiments, wherein the heating system comprises a heating element, the heating element being a resistive heating element. Example 23: The method according to example 22, wherein the method further comprises controlling power to raise the temperature of the heating element from the ambient temperature to the initial temperature during a preheat period before the first predetermined period. Example 24: 24. The method according to example 23, wherein the preheat period has a duration of 10 to 20 seconds. Example 25: The method according to any one of Examples 1 to 24, wherein the aerosol-forming substrate comprises a total aerosol former content greater than 35 weight percent. Example 26: The method according to any one of Examples 1 to 25, wherein the aerosol-forming substrate comprises a total aerosol former content of greater than 40 weight percent. Example 27: The method according to any one of Examples 1 to 26, wherein the aerosol-forming substrate comprises a total aerosol former content greater than 45 weight percent. Example 28: The method according to any one of Examples 1-27, wherein the aerosol-forming substrate comprises one or more aerosol formers selected from 1,3-butanediol, glycerin, 1,3-propanediol, propylene glycol, triethylene glycol, glycerol monoacetate, glycerol diacetate, glycerol triacetate, dimethyl dodecanedioate, and dimethyl tetradecanedioate. Example 29: The method according to any one of Examples 1 to 28, wherein the aerosol-forming substrate does not contain tobacco. Example 30: The method according to any one of Examples 1 to 29, wherein the aerosol-forming substrate further comprises nicotine. Example 31: The method according to any one of examples 1-30, wherein the aerosol-forming substrate further comprises one or more cellulosic agents and one or more carboxylic acids selected from fumaric acid, maleic acid, and malic acid. Example 32: The method according to example 31, wherein the aerosol-forming substrate has a total cellulosic agent content of at least 35 weight percent, and a total carboxylic acid content of at least 0.5 weight percent. Example 33: The method according to any one of embodiments 1 to 32, wherein the aerosol-forming substrate comprises water. Example 34: The method according to example 33, wherein the aerosol-forming substrate has a water content of from 5 percent by weight to 35 percent by weight. Example 35: 1. The system comprising: an aerosol-generating article comprising an aerosol-forming substrate having a total aerosol former content of 30 weight percent or more, the aerosol former substrate being a solid or a gel; and an aerosol generating device comprising: a heating chamber configured to at least partially receive the aerosol-generating article; a heating system associated with a heating element configured to internally heat the aerosol-forming substrate from within the aerosol-forming substrate; a power source for providing power to the heating system; and a controller configured to: during heating of the aerosol-forming substrate, increase a temperature of the heating element from an initial temperature to a first temperature, and to control the power to maintain the temperature of the heating element constant at the first temperature for the duration of a first predetermined period of time to form an aerosol for inhalation by a user, wherein the first temperature is between 245 degrees Celsius and 285 degrees Celsius. Example 36: The system according to example 35, wherein the first period has a duration of 40 seconds to 300 seconds, preferably 40 seconds to 150 seconds. Example 37: A system according to example 35 or 36, wherein controlling the power during heating of the aerosol-forming substrate to form an aerosol for inhalation by the user may further include adjusting the temperature of the heating element to a second temperature for a second predetermined period of time, the second predetermined period of time following the first predetermined period of time. Example 38: 38. The system according to example 37, wherein the second temperature is different from the first temperature. Example 39: The system according to example 36 or 37, wherein the second temperature is lower than the first temperature. Example 40: 39. The system according to example 39, wherein the second temperature is between 190 and 220 degrees Celsius. Example 41: The system according to any one of Examples 37-39, wherein adjusting the temperature of the heating element to the second temperature during the second predetermined period of time includes two successive temperature steps. Example 42: The system according to example 41, wherein the temperature of the first temperature step is lower than the temperature of the second temperature step. Example 43: The system according to example 37 or 38, wherein adjusting the temperature of the heating element to the second temperature during the second predetermined period of time includes increasing the temperature of the heating element from the first temperature. Example 44: A system according to any one of Examples 37 to 43, wherein the duration of the second predetermined period is 100 to 280 seconds. Example 45: A system according to any one of Examples 37 to 40, wherein controlling the power during heating of the aerosol-forming substrate to form an aerosol for inhalation by the user further comprises adjusting the temperature of the heating element to a third temperature for a third predetermined period of time, the third predetermined period following the second predetermined period of time. Example 46: The system according to example 45, wherein the third temperature corresponds approximately to the first temperature. Example 47: The system according to example 45 or 46, wherein the duration of the third predetermined period is between 30 seconds and 120 seconds. Example 48: The system according to any one of Examples 37 to 47, wherein the aerosol generating device may further comprise a memory configured to store a plurality of heating profiles, each heating profile defining a manner of adjusting the temperature of the heating element during each of the time periods, and the controller is further configured to control power during heating of the aerosol-forming substrate to form an aerosol for inhalation by a user based on a heating profile of the plurality of temperature profiles. Example 49: The system according to example 48, wherein the controller is further configured to select a heating profile based on an identification of the aerosol-generating article. Example 50: A system according to any one of Examples 37 to 47, wherein the aerosol generating device further comprises a memory configured to store a plurality of temperature profiles, each heating profile defining a manner of adjusting the temperature of the heating element during a second predetermined period of time, and the controller is further configured to control power during heating of the aerosol-forming substrate to form an aerosol for inhalation by a user based on a heating profile of the plurality of temperature profiles. Example 51: A system according to example 50, wherein the controller is further configured to select a heating profile based on an identification of the aerosol-generating article. Example 52: The system according to any one of Examples 35 to 51, wherein the aerosol-forming substrate further comprises a heating element, and the heating system comprises an induction coil for inductively heating the heating element. Example 53: The system according to any one of Examples 35-52, wherein the controller is further configured to control power to raise the temperature of the heating element from the ambient temperature to the initial temperature during a pre-heating period before the first predetermined period. Example 54: 54. The system according to embodiment 52 or 53, wherein the preheat period has a duration of 10 to 20 seconds. Example 55: The system according to any one of Examples 52-54, wherein the controller is further configured to calibrate the heating element following the pre-heat period and prior to the first period. Example 56: The system according to any one of Examples 35 to 51, wherein the heating system comprises a heating element, the heating element being a resistive heating element. Example 57: 57. The system according to example 56, wherein the controller is further configured to control the power to raise the temperature of the heating element from the ambient temperature to the initial temperature during a pre-heating period before the first predetermined period. Example 58: 58. The system according to example 57, wherein the preheat period has a duration of 10 to 20 seconds. Example 59: The method according to any one of Examples 35-58, wherein the aerosol-forming substrate comprises a total aerosol former content greater than 35 weight percent. Example 60: The method according to any one of Examples 35 to 59, wherein the aerosol-forming substrate comprises a total aerosol former content of greater than 40 weight percent. Example 61: The method according to any one of Examples 35 to 60, wherein the aerosol-forming substrate comprises a total aerosol former content greater than 45 weight percent. Example 62: The system according to any one of Examples 35-61, wherein the aerosol-forming substrate comprises one or more aerosol formers selected from 1,3-butanediol, glycerin, 1,3-propanediol, propylene glycol, triethylene glycol, glycerol monoacetate, glycerol diacetate, glycerol triacetate, dimethyl dodecanedioate, and dimethyl tetradecanedioate. Example 63: A system according to any one of Examples 35 to 62, wherein the aerosol-forming substrate does not contain tobacco. Example 64: The system according to any one of Examples 35 to 63, wherein the aerosol-forming substrate further comprises nicotine. Example 65: The system according to any one of Examples 35-64, wherein the aerosol-forming substrate further comprises one or more cellulosic agents and one or more carboxylic acids selected from fumaric acid, maleic acid, and malic acid. Example 66: The system according to Example 65, wherein the aerosol-forming substrate has a total cellulosic agent content of at least 35 weight percent and a total carboxylic acid content of at least 0.5 weight percent. Example 67: The system according to any one of Examples 35 to 66, wherein the aerosol-forming substrate comprises water. Example 68: The system according to example 67, wherein the aerosol-forming substrate has a water content of 5 weight percent to 35 weight percent.

[0109] The embodiments will now be further described with reference to the figures. [Brief description of the drawings]

[0110] [Figure 1] FIG. 1 is a schematic cross-sectional view of an aerosol-generating article including an aerosol-forming substrate and a susceptor. [Diagram 2] FIG. 2 is a schematic cross-sectional view of an aerosol generating system comprising the aerosol generating article shown in FIG. 1 and an electrically operated aerosol generating device including an inductor. [Diagram 3] FIG. 3 is a graph of DC current versus time illustrating the remotely detectable change in electrical current that occurs as the susceptor material undergoes a phase transition associated with its Curie point. [Figure 4] FIG. 4 is a graph of conductance versus time illustrating the change in conductance corresponding to changes in temperature of the susceptor during user operation of the aerosol generating device. [Diagram 5] FIG. 5 shows a schematic cross-sectional view of an aerosol-generating article including an aerosol-forming substrate. [Figure 6] FIG. 6 shows a schematic cross-sectional view of an aerosol-generating system comprising the aerosol-generating article shown in FIG. 5 and an electrically operated aerosol-generating device including a resistive heater for internally heating the aerosol-forming substrate from within the aerosol-forming substrate. [Figure 7] FIG. 7 is a graph of temperature versus time illustrating a portion of a heating profile during user operation of the aerosol generating device illustrated in FIG. [Figure 8] FIG. 8 is a graph of temperature versus time illustrating a portion of a heating profile during user operation of the aerosol generating device illustrated in FIG. [Figure 9] FIG. 9 is a graph of temperature versus time illustrating a portion of a heating profile during user operation of the aerosol generating device illustrated in FIG. [Figure 10] FIG. 10 is a graph of temperature versus time illustrating a portion of a heating profile during user operation of the aerosol generating device illustrated in FIG. [Figure 11] FIG. 11 is a graph of temperature versus time illustrating a portion of a heating profile during user operation of the aerosol generating device illustrated in FIG. [Figure 12] FIG. 12 is a graph of temperature versus time illustrating a portion of a heating profile during user operation of the aerosol generating device illustrated in FIG. [Figure 13] FIG. 13 is a graph of temperature versus time illustrating a portion of a heating profile during user operation of the aerosol generating device illustrated in FIG. [Figure 14] FIG. 14 is a flow diagram of a method for controlling aerosol generation in an aerosol generating device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0111] FIG. 1 is a schematic cross-sectional view of an aerosol-generating article 10 in which an aerosol-forming substrate of the aerosol-generating article is inductively heated from within.

[0112] FIG. 2 is a schematic cross-sectional view of an aerosol generating system 100 comprising the aerosol generating article 10 shown in FIG. 1 and an electrically operated aerosol generating device 110 including an inductor.

[0113] The aerosol-generating article 10 shown in Figure 1 comprises an aerosol-generating rod 12, a proximal section 14 located downstream of the aerosol-generating rod 12, and a distal section 16 located upstream of the aerosol-generating rod 12. As shown in Figure 1, the aerosol-generating article 10 has an upstream or distal end 18 and a downstream or proximal end 20.

[0114] The proximal section 14 of the aerosol-generating article 10 includes a support element 22 located immediately downstream of the aerosol-generating rod 12, an aerosol cooling element 24 located immediately downstream of the support element 22, and a mouthpiece element 42 located immediately downstream of the aerosol cooling element 24.

[0115] The support element 22 may include a first hollow tubular segment 26. The first hollow tubular segment 26 is in the form of a hollow cylindrical tube made of cellulose acetate. The first hollow tubular segment 26 defines an interior cavity 28 that extends from an upstream end 30 of the first hollow tubular segment to a downstream end 32 of the first hollow tubular segment 20.

[0116] The aerosol cooling element 24 includes a second hollow tubular segment 34. The second hollow tubular segment 34 is in the form of a hollow cylindrical tube made of cellulose acetate. The second hollow tubular segment 34 defines an interior cavity 36 that extends from an upstream end 38 of the second hollow tubular segment to a downstream end 40 of the second hollow tubular segment 34.

[0117] As shown by the vertical lines in FIG. 1, the aerosol-generating article 10 includes a ventilation zone 60 provided at a location along the second hollow tubular segment 34 .

[0118] Mouthpiece element 42 is in the form of a cylindrical plug of low density cellulose acetate.

[0119] The aerosol-generating rod 12 comprises an aerosol-forming substrate. The aerosol-forming substrate may be a solid or a gel. The aerosol-forming substrate comprises one or more aerosol formers, such as glycerin or propylene glycol. The total aerosol former content of the aerosol-forming substrate may be greater than 30 percent by weight. The total aerosol former content of the aerosol-forming substrate may be greater than 40 percent by weight. The total aerosol former content of the aerosol-forming substrate may be greater than 45 percent by weight. The aerosol-forming substrate may be a non-tobacco substrate that does not comprise tobacco-containing material. Alternatively, the aerosol-forming substrate may comprise tobacco-containing material. In addition, the aerosol-forming substrate may comprise water. The aerosol-forming substrate may have a water content of between 5 percent by weight and 35 percent by weight.

[0120] The aerosol-forming substrate may comprise nicotine. The aerosol-forming substrate may comprise one or more cellulosic agents. The aerosol-forming substrate may comprise one or more carboxylic acids. The one or more carboxylic acids may be selected from fumaric acid, maleic acid, and malic acid.

[0121] The aerosol-forming substrate may be an aerosol-generating film and the aerosol-generating rod 12 may comprise an assembly of crimped paper sheets coated with a solid aerosol-generating film.

[0122] The aerosol-generating article 10 comprises a heating element, such as a susceptor 44, located within the aerosol-generating rod 12. As shown in Figure 2, the susceptor 44 is surrounded by the aerosol-forming substrate and extends along the longitudinal axis of the aerosol-generating rod 12 from the upstream end of the aerosol-generating rod 12 to the downstream end of the aerosol-generating rod 12. The susceptor 44 is in direct contact with the aerosol-forming substrate.

[0123] The susceptor 44 may be in the form of a strip having a length of 12 millimeters, a width of 5 millimeters, and a thickness of 60 micrometers. The susceptor 44 includes at least two different materials. The susceptor 44 includes at least two layers, a first layer of a first susceptor material disposed in physical contact with a second layer of a second susceptor material. The first susceptor material and the second susceptor material may each have a Curie temperature. In this case, the Curie temperature of the second susceptor material is lower than the Curie temperature of the first susceptor material. The first material may not have a Curie temperature. The first susceptor material may be aluminum, iron, or stainless steel. The second susceptor material may be nickel or a nickel alloy.

[0124] The distal section 16 of the aerosol-generating article 10 includes an upstream element 46 located immediately upstream of the aerosol-generating rod 12 .

[0125] The upstream element 46 is in the form of a cylindrical plug of cellulose acetate surrounded by a rigid wrapper.

[0126] The aerosol generating system 100 shown in FIG. 2 comprises the aerosol generating article 10 shown in FIG.

[0127] The aerosol generating device 110 comprises a housing 112 defining a heated chamber 114 configured to receive a distal portion of the aerosol-generating article 10 .

[0128] The aerosol generating device 110 includes a power source (not shown) and a heating system (not shown). The heating system includes a controller, a DC / AC converter, and an inductor 116. The power source may be a battery, such as a rechargeable lithium-ion battery. The inductor 116 includes an induction coil. The controller controls the supply of power from the power source to the induction coil.

[0129] In use, the varying or alternating electromagnetic field generated by the induction coil of inductor 116 induces eddy currents in the susceptor 44 in the aerosol-generating rod 12 of the aerosol-generating article 10, heating the susceptor 44. The heat generated in the susceptor 44 is transferred by conduction to the aerosol-forming substrate in the aerosol-generating rod 12 of the aerosol-generating article 10.

[0130] A user inhales on the mouthpiece element 42 of the aerosol-generating article 10. As the user inhales on the mouthpiece element 42, air is drawn into the aerosol-generating article 10 via the distal end 18. The drawn-in air passes through the upstream element 46 to the aerosol-generating rod 12. Heating of the aerosol-forming substrate releases volatile and semi-volatile compounds, which form an aerosol that is entrained in the drawn-in air as it flows through the aerosol-generating rod 12. The drawn-in air and entrained aerosol pass through the intermediate hollow section 50 of the aerosol-generating article 10, where it cools and condenses. The cooled aerosol then passes downstream through the mouthpiece element 42 of the aerosol-generating article 10 into the user's mouth.

[0131] FIG. 3 illustrates the relationship between the DC current IDC drawn from the power supply over time as the temperature of the susceptor 44 (shown by the dashed line) increases. More specifically, FIG. 3 illustrates the remotely detectable change in DC current that occurs when the susceptor material undergoes a phase transition associated with its Curie point. The DC current IDC drawn from the power supply is measured at the input side of the DC / AC converter. For purposes of this illustration, it can be assumed that the voltage VDC of the power supply remains approximately constant.

[0132] When the susceptor 44 is inductively heated, the apparent resistance of the susceptor 44 increases. This increase in resistance is observed as a decrease in the DC current IDC drawn from the power supply, which at constant voltage decreases as the temperature of the susceptor 44 increases. The high frequency alternating magnetic field provided by the inductor induces eddy currents in close proximity to the susceptor surface, an effect known as the skin effect. The resistance of the susceptor 44 depends partly on the electrical resistivity of the first susceptor material, partly on the resistivity of the second susceptor material, and partly on the depth of the skin layers of each material available to the induced eddy currents, with the resistivity being temperature dependent.

[0133] As the second susceptor material reaches its Curie temperature, it loses its magnetism. This makes more of the skin layer available for eddy currents in the second susceptor material, which reduces the apparent resistance of the susceptor 44. This results in a temporary increase in the detected DC current IDC. The resistance then begins to decrease as the skin depth of the second susceptor material begins to increase. This is seen as the valley (local minimum) 310 in FIG. 3.

[0134] As heating continues, the current continues to increase until it reaches a maximum skin depth consistent with the point at which the second susceptor material loses its natural magnetic properties. This point is called the Curie temperature and is seen in FIG. 3 as a hill (local maximum) 320. At this point, the second susceptor material has undergone a phase change from a ferromagnetic or ferrimagnetic state to a paramagnetic state. At this point, the susceptor 160 is at a known temperature (the Curie temperature, which is a unique material specific temperature).

[0135] If inductive heating of the susceptor 44 continues after the Curie temperature is reached, eddy currents generated within the susceptor 44 will flow against the resistance of the susceptor 44, causing continued Joule heating of the susceptor 44, which causes the resistance to increase again (resistance has a polynomial dependence on temperature, which for most metallic susceptor materials can be approximated for our purposes to a third order polynomial dependence) and the current to begin to decrease again.

[0136] Thus, the second susceptor material undergoes a reversible phase transition between the valleys 310 and hills 320 shown in FIG. 3 when heated through a (known) temperature range. As can be seen from FIG. 3, the apparent resistance of the susceptor 44, and therefore the onset and end of the reversible phase transition, can be remotely detected by monitoring at least the DC current IDC drawn from the power supply. Although the DC supply voltage VDC is known, the DC supply voltage VDC may be monitored in addition to the DC current IDC. Thus, the apparent resistance of the susceptor 44, and therefore the onset and end of the phase transition, can be remotely detected by monitoring the conductance value (conductance is defined as the ratio of the DC current IDC to the DC supply voltage VDC) or the resistance value (resistance is defined as the ratio of the DC supply voltage VDC to the DC current IDC). The DC current IDC, the conductance value, and the resistance value may be referred to as power supply parameters.

[0137] As can be seen from FIG. 3, the apparent resistance of the susceptor 44 (and the corresponding current IDC drawn from the power supply) can vary with the temperature of the susceptor 44 in a strictly monotonic relationship between the start and end of the reversible phase transition, in other words, between the valley 310 and the hill 320. The strictly monotonic relationship allows for an unambiguous determination of the temperature of the susceptor 44 from a determination of the apparent resistance (R) or apparent conductance (1 / R). This is because each determined value of the apparent resistance represents only one value of temperature, and there is no ambiguity in the relationship. The monotonic relationship between the temperature of the susceptor 44 and the apparent resistance in the temperature range in which the second susceptor material undergoes a reversible phase transition allows for the temperature of the susceptor 44, and therefore the temperature of the aerosol-forming substrate, to be determined and controlled.

[0138] The controller adjusts the supply of power provided to the heating system based on the measurements of the power supply parameters. The heating system may include a current sensor (not shown) for measuring the DC current IDC. The heating system may optionally include a voltage sensor (not shown) for measuring the DC supply voltage VDC. The current sensor and the voltage sensor are located on the input side of the DC / AC converter. The DC current IDC, and optionally the DC supply voltage VDC, are provided by a feedback channel to the controller to control the further supply of AC power PAC to the inductor 116.

[0139] The controller may control the temperature of the susceptor 44 by maintaining the measured power supply parameter value at a target value that corresponds to a target operating temperature of the susceptor 44. In other words, the controller regulates the temperature of the susceptor 44 by controlling the power provided to the heating system, which in turn regulates the power supply parameter value.

[0140] To take advantage of the strictly monotonic relationship between the apparent resistance (or apparent conductance) of the susceptor 44 and the temperature of the susceptor 44, during user operation to generate an aerosol, a power supply parameter measured at the input side of the DC / AC converter is maintained between a first calibration value corresponding to a first calibration temperature and a second calibration value corresponding to a second calibration temperature. The second calibration temperature is the Curie temperature of the second susceptor material (hill 320 of the current plot in FIG. 3). The first calibration temperature is a temperature at or above the temperature of the susceptor at which the skin depth of the second susceptor material begins to increase, resulting in a temporary drop in resistance (valley 310 of the current plot in FIG. 3). Thus, the first calibration temperature is a temperature at or above the temperature at maximum permeability of the second susceptor material. The first calibration temperature is at least 50 degrees Celsius lower than the second calibration temperature. At least the second calibration value is determined by calibration of the susceptor 44, as described in more detail below. The first calibration value and the second calibration value may be stored as calibration values ​​in the memory of the aerosol generating device 110.

[0141] Since the power supply parameters have a polynomial dependence on temperature, the power supply parameters behave nonlinearly as a function of temperature. However, the first and second calibration values ​​are selected such that this dependence can be approximated as linear between the first and second calibration values ​​because the difference between the first and second calibration values ​​is small, and such that the first and second calibration values ​​are in the upper part of the operating temperature range. Thus, to adjust the temperature to the target operating temperature, the power supply parameters are adjusted according to the first and second calibration values ​​via a linear equation.

[0142] For example, if the first and second calibration values ​​are conductance values, then a target conductance value G corresponding to the target operating temperature R can be given as: G R =G Lower +(x×ΔG) where ΔG is the difference between the first conductance value and the second conductance value, and x is a percentage of ΔG. Thus, the controller adjusts the power supply parameter value based on the power supply parameter value measured at the valley 310 during calibration and the difference between the power supply parameter value measured at the hill 320 and the power supply parameter value measured at the valley 310 during calibration.

[0143] The first and second calibration values ​​are obtained by performing a calibration process. The controller is programmed to perform the calibration process each time a user operates the aerosol generating device 110. For example, the controller may be configured to enter a calibration mode to perform the calibration process when a user turns on the aerosol generating device 110. The controller may be programmed to enter the calibration mode each time a user inserts an aerosol-generating article 10 into the aerosol generating device 110. Thus, the calibration process is performed during a first heating stage of the aerosol generating device, prior to a hand stage in which the user inhales the generated aerosol.

[0144] During the calibration process, the controller controls the DC / AC converter to continuously or intermittently supply power to the inductor 116 to heat the susceptor 44. The controller monitors the power supply parameters by measuring the current IDC drawn by the power supply and, optionally, the power supply voltage VDC. As the susceptor 44 heats up, the measured current decreases until it reaches a valley (first turning point) 310 and the current IDC begins to increase. This first turning point 310 corresponds to a local minimum conductance or current value (local maximum resistance value). The controller may record the power supply parameter value at the first turning point 310 as a first calibration value.

[0145] The temperature of the susceptor 44 at the first calibration value is the first calibration temperature. As the controller continues to control the power provided by the DC / AC converter to the inductor 116, the controller continues to monitor the power source parameter until a hill (second turning point) 320 is reached. The second turning point corresponds to a maximum current (corresponding to the Curie temperature of the second susceptor material) before the measured current begins to decrease. This second turning point 320 corresponds to a local maximum conductance or current value (local minimum resistance value). The control circuit records the power source parameter value at the second turning point 320 as the second calibration value. The temperature of the susceptor 44 at the second calibration value is the second calibration temperature. When the second turning point 320 is detected, the controller controls the DC / AC converter to interrupt the provision of power to the inductor 116, resulting in a decrease in the temperature of the susceptor 44 and a corresponding decrease in the measured current.

[0146] This process of continually heating the susceptor 44 to obtain first and second calibration values ​​due to the shape of graph 300 may be repeated at least once during the calibration mode. Preferably, the controller adjusts the power based on the power supply parameter values ​​obtained from the smallest iteration of the calibration process, which is more reliable because heat has had more time to disperse into the aerosol-forming substrate and susceptor 44.

[0147] The controller is configured to detect turning points 310 and 320 by measuring a sequence of power supply parameter values. With reference to Figure 3, the sequence of measured power supply parameter values ​​forms a curve, with each value being greater or less than the previous value. The controller is configured to measure the calibration value at the point where the curve begins to flatten. In other words, the controller records the calibration value when the difference between successive power supply parameter values ​​falls below a predefined threshold.

[0148] To further improve the reliability of the calibration process, the controller may be optionally programmed to perform a pre-heating process before the calibration process. For example, if the aerosol-forming substrate is particularly dry or in similar conditions, the calibration process may be performed before heat spreads into the aerosol-forming substrate, reducing the reliability of the calibration value. If the aerosol-forming substrate is wet, the susceptor 44 takes longer to reach the valley temperature (due to the moisture content of the aerosol-forming substrate).

[0149] To perform the preheating process, the controller is configured to continuously supply power to the inductor 116. As described above with respect to FIG. 3, the measured current begins to decrease as the temperature of the susceptor 44 increases until a turning point 310 corresponding to a minimum measured current (conductance) is reached. At this stage, the controller is configured to wait a predetermined period of time to allow the susceptor 44 to cool before continuing heating. Thus, the controller controls the DC / AC converter to interrupt the supply of power to the inductor 116. After the predetermined period of time, the controller controls the DC / AC converter to provide power until the turning point 310 corresponding to the minimum measured current is again reached. At this point, the controller controls the DC / AC converter to again interrupt the supply of power to the inductor 116. The controller again waits the same predetermined period of time to allow the susceptor 44 to cool before continuing heating. This heating and cooling of the susceptor 44 is repeated for a predetermined duration of the preheating process 410. The predetermined duration of the preheating process is 10 to 20 seconds, preferably 11 seconds. The duration of the calibration process is between 10 and 20 seconds. If the aerosol-forming substrate is dry, the first current minimum of the pre-heating process is reached within the predetermined period and the interruption of power is repeated until the end of the predetermined period. If the aerosol-forming substrate has a high moisture content, the first current minimum of the pre-heating process 410 is reached towards the end of the predetermined period. Thus, carrying out the pre-heating process for a predetermined duration ensures that the aerosol-forming substrate has enough time to reach a minimum operating temperature in order to be ready to be continuously powered to reach the first maximum, regardless of the physical state of the aerosol-forming substrate. This allows for calibration as early as possible without the risk that the aerosol-forming substrate has not reached the first calibration temperature beforehand.

[0150] In particular, aerosol-forming substrates containing high aerosol former content (e.g., greater than 30 weight percent) and high water content (e.g., greater than 5 weight percent) will have a higher thermal inertia. Thus, a preheating process ensures that a minimum operating temperature is reached before calibration.

[0151] The pre-heating process may be performed in response to receiving a user input, for example, user activation of the aerosol generating device 110. Additionally or alternatively, the control circuitry may be configured to detect the presence of an aerosol-generating article 10 in the aerosol generating device 110, and the pre-heating process may be performed in response to detecting the presence of an aerosol-generating article 10 in the heating chamber of the aerosol generating device 110.

[0152] 4 is a graph of conductance versus time showing a heating profile of the susceptor 44. The graph illustrates five stages of the heating profile, a pre-heating process 410 performed during a pre-heating mode, a calibration process 420 performed during a calibration mode, and the main stages during which a user inhales an aerosol, including heating modes 430, 440, and 450. Although FIG. 4 is illustrated as a graph of conductance versus time, it should be understood that the controller may be configured to control the heating of the susceptor 44 during each stage of the heating profile based on any measured power supply parameter, such as resistance or current, as discussed above.

[0153] Upon completion of the calibration process 420, the controller is configured to discontinue providing power to the heating system to allow the susceptor to cool to the initial temperature. After the susceptor temperature is detected to be at the initial temperature or after the susceptor temperature has been at the initial temperature for a predetermined period of time, the controller is configured to control the power provided to the heating system to increase the temperature of the susceptor 44 from the initial temperature to a first temperature. Specifically, the controller controls the power provided to the heating system to adjust the conductance to correspond to a first operating temperature of the susceptor 44 for a first predetermined period of time. In one embodiment, the conductance during the first heating mode 430 is 0.75×ΔG, or in other words, 75 percent of the difference in measured conductance between the hills 320 and the valleys 310.

[0154] The first operating temperature is selected so that the desired volatile compounds are vaporized from the substrate, but undesirable compounds that vaporize or evolve at higher temperatures are not released. Additionally, heating the susceptor 44 to the maximum operating temperature of the susceptor 44 immediately after the calibration process 420 improves the amount of desired volatile compounds vaporized, thereby providing improved delivery to the user from the first puff. The first operating temperature of the susceptor 44 may be the maximum operating temperature of the susceptor 44.

[0155] FIG. 5 is a schematic cross-sectional view of an aerosol-generating article 500 .

[0156] FIG. 6 is a schematic cross-sectional view of an aerosol generating system 600 comprising the aerosol-generating article 500 of FIG. 5 and an electrically powered aerosol generating device 610 including a resistive heater configured to heat the aerosol-generating article 500 from within the aerosol-generating article 500.

[0157] The aerosol-generating article 500 has generally the same structure as the aerosol-generating article 10 described above with respect to Figure 1, and like elements are indicated by like reference numerals. However, it should be noted that the aerosol-generating article 500 does not include a susceptor 44. In addition, the aerosol-generating article does not include an upstream element 46.

[0158] The aerosol generating device 610 comprises a heating chamber 630 for receiving the aerosol generating article 500. A heating element 620 is located within the heating chamber and positioned to engage the distal end 18 of the aerosol generating article 500. The heating element 620 is an electrically resistive heating element formed in the form of a blade terminating in a tip. The heating element 620 may be formed from a ceramic substrate with one or more resistive heating tracks formed from platinum or another suitable material and disposed on one or both sides of the blade. Alternatively, the heating element 620 may be one or more heating needles or rods that penetrate the center of the aerosol forming substrate 510. Other alternatives include heating wires or filaments, such as Ni-Cr (nickel chromium), platinum, tungsten, or alloy wires, or heating plates. Optionally, the heating element 620 may be disposed within or on a rigid carrier material. For example, the electrically resistive heating element 620 may be formed using a metal having a defined relationship between temperature and resistivity. In such an exemplary device, the metal may be formed as a track on a suitable insulating material, such as a ceramic material, and then covered by another insulating material, such as glass. A heater formed in this manner may be used to both heat the element and monitor its temperature during operation.

[0159] As the aerosol-generating article 500 is pressed onto the tip of the heating element 620, the application of force to the aerosol-generating article 500 causes the heating element 620 to penetrate the aerosol-forming substrate of the aerosol-generating rod 12. Further penetration is prevented because the distal end 18 of the aerosol-generating article 500 abuts the end wall 640 of the heating chamber 630, which acts as a stop.

[0160] When the aerosol-generating article 500 is properly engaged with the aerosol-generating device 610, the heating element 620 is located within the aerosol-forming substrate in contact with the aerosol-forming substrate. The heating element 620 heats the aerosol-forming substrate by conduction.

[0161] The aerosol generating device 610 includes a power source (not shown) and a heating system (not shown) electrically coupled to the power source. The heating system includes a controller and a heating element 620. The power source may be a battery, such as a rechargeable lithium ion battery. The power source is configured to provide power to the heating system to heat the heating element 620.

[0162] The controller obtains an indication of the temperature of the heating element 620 (e.g., the electrical resistance of the heating element) by measuring the electrical resistance of the heating element 620. The indication of temperature is used to adjust the current supplied to the heating element 620 to maintain the heating element 620 near a target temperature. In other words, the controller adjusts the temperature of the heating element by adjusting the current supplied to the heating element 620.

[0163] This approach relies on three or more temperature calibration points at which the resistance of the heating element 620 is measured. For temperatures intermediate the calibration points, the resistance values ​​are extrapolated from the values ​​at the calibration points. The calibration point temperatures are selected to cover the expected temperature range of the heating element 620 during operation. Calibration of the heating element 620 to obtain the calibration points is performed at the time of manufacture, and the calibration points may be stored in the memory of the controller.

[0164] When the heating element 620 is heated, the aerosol-forming substrate is heated and a volatile substance is formed. When a user inhales on the proximal end 20 of the aerosol-generating article 500, air is drawn into the aerosol-generating article 500 and the volatile substance condenses to form an inhalable aerosol. The aerosol passes through the proximal end 20 of the aerosol-generating article 500 and into the user's mouth.

[0165] Figure 7 is a graph of heating element temperature versus time showing a portion of the heating profile of an aerosol generating device using resistive heating described above with respect to Figure 6. During step 710, the heating element is at an initial temperature. Step 710 may be a pre-heat step in which the controller is programmed to pre-heat the heating element to a predetermined initial temperature for a predetermined duration.

[0166] The pre-heating stage ensures that the duration of the pre-heating stage is sufficient for the aerosol-forming substrate to reach a minimum operating temperature, regardless of the physical state of the aerosol-forming substrate (e.g., dry or wet), in order to provide continuous power and to be ready to reach the first operating temperature as quickly as possible in order to generate sufficient aerosol for a user to inhale.

[0167] In particular, aerosol-forming substrates comprising non-tobacco materials will have a higher thermal inertia than tobacco-based aerosol-forming substrates because non-tobacco aerosol-forming substrates contain a higher aerosol former content (e.g., greater than 30 weight percent) and a higher moisture content (e.g., greater than 5 weight percent). Thus, for non-tobacco aerosol-forming substrates with a high moisture content, the pre-heating process ensures that the minimum operating temperature is reached before the main stage. The duration of the pre-heating mode is 10-20 seconds, preferably 11 seconds.

[0168] Following the pre-heat phase, the controller is configured to enter a main phase, a first heating mode 720. The first heating mode may be entered in response to a timer indicating that a predetermined duration of the pre-heat phase 710 has elapsed, a user actuation of the aerosol generating device, or after detection of a user puff. During the first heating mode 720, the controller rapidly increases the temperature of the heating element from an initial temperature to a first temperature.

[0169] The first temperature is selected such that the desired volatile compound vaporizes from the substrate while undesirable compounds that vaporize or evolve at higher temperatures are not released. Additionally, rapidly heating the heating element to the first temperature of the heating element improves the amount of desired volatile compound vaporized, thereby providing improved delivery from the first puff to the user. The first temperature may be the maximum operating temperature of the heating element.

[0170] During steps 720, 730 and 740, the aerosol generating device generates an aerosol for inhalation by the user, and the controller is configured to control the power provided to the heating element to adjust the temperature of the heating element according to a heating profile.

[0171] The one or more heating profiles may be stored in a memory of a controller as described in relation to Figures 1, 2 and 6. The controller may be configured to select a heating profile during user operation of the device for generating an aerosol. For example, the aerosol generating device may be provided with means for identifying an aerosol-generating article or an aerosol-forming substrate and may select a heating profile based on the identification.

[0172] 8-13 are graphs of heating element temperature versus time showing exemplary heating profiles of a heating element during a main phase of heating an aerosol-forming substrate to form an aerosol for inhalation by a user. The illustrated heating profiles define temperature values ​​for each heating mode and the corresponding duration of each heating mode. However, it should be understood that the heating profile may include more than three heating modes.

[0173] Each of the heating profiles in Figures 8-13 shows a shaded region 810, 910, 1010, 1110, 1210 and 1310. The shaded regions correspond to the calibration and optional pre-heating stages of an aerosol generating device having an inductive heating system (Figure 2) or the pre-heating stage of an aerosol generating device having a resistive heating system (Figure 6).

[0174] Each of the heating profiles of Figures 8-13 illustrates that the temperature of the heating element increases from an initial temperature (not shown) to a first temperature in a first heating mode 820, 920, 1020, 1120, 1220, 1320. The controller may be configured to enter the first heating mode 820, 920, 1020, 1120, 1220, 1320 in response to a user activation of the aerosol generating device or detection of a user puff. The temperature remains constant at the first temperature for the duration of the first period. The initial temperature is above ambient temperature, between 140 and 170 degrees Celsius. In the case of induction heating, the initial temperature may be a temperature reached during the calibration process 420. For example, after reaching a maximum conductance during the calibration process at the hill 320, the heating element 44 may be allowed to cool to a temperature between the first and second calibration temperatures. The temperature to which the heating element 44 is cooled may be the initial temperature. In the case of resistive heating, the initial temperature may be the preheat temperature of the heating element 620 .

[0175] The first temperature may be between 245 and 285 degrees Celsius. As described above, by heating the heating element in the first heating mode 820, 920, 1020, 1120, 1220, 1320 to the first temperature of the heating element, the thermal inertia of the aerosol-forming substrate is overcome and the amount of desired volatile compounds vaporized in the aerosol inhaled by the user, such as nicotine and aerosol former, is improved from the first puff.

[0176] After the first predetermined period of time, the controller enters a second heating mode 830, 930, 1030, 1130, 1230, 1330. In the second heating mode, the controller adjusts the temperature of the heating element to one or more second temperatures for a second predetermined period of time. The one or more second temperatures may be between 190 and 220 degrees Celsius.

[0177] In the second heating mode 830, 930, 1030, 1130, 1230, 1330, the controller may adjust the temperature of the heating element to approximately correspond to the first temperature, as shown in FIG.

[0178] In the second heating mode 830, 930, 1030, 1130, 1230, 1330, the controller may adjust the temperature of the heating element to be lower than the first temperature, as shown in Figures 10, 11, 12 and 13. At the end of the first heating mode 820, 920, 1020, 1120, 1220, 1320, heat will be diffused throughout the aerosol-forming substrate. Thus, by lowering the temperature of the heating element in the second heating mode, the amount of vaporized desired volatile compounds in the aerosol inhaled by the user remains consistent with the amount during the first heating mode 820, 920, 1020, 1120, 1220, 1320, thereby providing the same sensory experience to the user.

[0179] In the second heating mode 830, 930, 1030, 1130, 1230, 1330, the controller may adjust the temperature of the heating element to be higher than the first temperature, as shown in FIG.

[0180] In the second heating mode 830, 930, 1030, 1130, 1230, 1330, the controller may adjust the temperature of the heating element to a second temperature for the duration of the second period, as shown in Figures 8, 9 and 13. Alternatively, in the second heating mode, the controller may adjust the temperature of the heating element in multiple successive temperature steps. For example, Figure 10 shows two temperature steps having the same duration, where the temperature of the heating element is lower during the first temperature step than during the second temperature step. Figure 11 shows two temperature steps, where the temperature of the heating element is lower during the first temperature step than during the second temperature step, and the duration of the first temperature step is shorter than the duration of the second temperature step.

[0181] In the third heating mode 840, 940, 1040, 1140, 1240, 1340, the controller is configured to adjust the temperature of the heating element to a third temperature. The temperature of the heating element remains constant at the third temperature for a predetermined duration of a third period. As shown in Figures 8-13, the third temperature corresponds approximately to the first temperature. At this stage of the use session, the aerosol-forming substrate will be depleted of the desired volatile compound. Thus, increasing the temperature of the heating element to approximately the first temperature allows the amount of vaporized desired volatile compound in the aerosol inhaled by the user to remain consistent with the amount during the first and second heating modes.

[0182] Each of the predetermined periods may be equal in length or may be different in length. For example, a first predetermined period may be shorter than a subsequent second predetermined period, for example, as shown in Figures 8, 9, 10 and 12. Additionally or alternatively, the first predetermined period may be shorter than a third predetermined period, for example, as shown in Figures 9 and 10. The second predetermined period may be longer than at least one of the first and third predetermined periods, for example, as shown in Figures 8-13. The first and third predetermined periods may have durations, for example, as illustrated in Figure 12.

[0183] The length of the first predetermined period may be between 40 seconds and 150 seconds, the length of the second predetermined period may be between 100 seconds and 280 seconds, and the length of the third predetermined period may be between 30 seconds and 120 seconds.

[0184] The length of the first predetermined period is selected such that the aerosol-forming substrate is capable of providing good delivery of the desired compound volatilized in the aerosol, and a first predetermined period that is at least shorter than the second predetermined period ensures good aerosol delivery to the user while ensuring a consistency of user experience throughout an entire use session.

[0185] A length of the second predetermined period that is at least longer than the first predetermined period provides improved control of the amount of vaporized desired volatile compounds in the aerosol inhaled by the user, particularly when the second temperature is lower than the first temperature, thereby providing a consistent user experience for as long as possible throughout an entire use session.

[0186] FIG. 14 is a flow chart illustrating a method of controlling aerosol generation in one of the aerosol generating devices by heating a heating item inserted into the heating chamber of the aerosol generating device, as described above.

[0187] The method begins at step 1410 when a user activates heating of the heating element, as described above. For example, the user may press one or more buttons on the aerosol generating device to initiate heating of the heating element. Additionally or alternatively, the user may insert an aerosol-generating article into a heating chamber of the aerosol generating device to initiate heating of the heating element.

[0188] The method then proceeds to step 1420 where the controller controls the power provided to the heating system to raise the temperature of the heating element from the ambient temperature to the initial temperature. During step 1420, the controller is in a pre-heat mode and maintains the temperature of the heating element at the initial temperature for a predetermined period of time.

[0189] If the aerosol generator heats the heating element by induction (the aerosol generator of FIG. 2), the preheat mode is followed by a calibration process in step 1430 to obtain first and second calibration values. The controller uses the first and second calibration values ​​to adjust the temperature of the susceptor as described above.

[0190] At step 1440, following step 1420 for an aerosol generating device using resistive heating and following step 1430 for an aerosol generating device using inductive heating, the controller enters a first heating mode. In the first heating mode, the controller adjusts the temperature of the heating element to increase the temperature from an initial temperature to a first temperature. The first temperature is maintained for a first predetermined period of time.

[0191] At the end of the first predetermined period, the controller enters a second heating mode at step 1450. In the second heating mode, the controller adjusts the temperature of the heating element to a second temperature. The second temperature may be maintained for a second predetermined period. Alternatively, the second temperature may be a first step of multiple temperature steps, each having a predetermined duration, the sum of the predetermined durations of each temperature step being the second predetermined period of the second heating mode. The second temperature may be lower, approximately equal to, or higher than the first temperature.

[0192] At the end of the second predetermined time period, the controller enters a third heating mode at step 1460. In the third heating mode, the controller adjusts the temperature of the heating element to a third temperature. The third temperature is maintained for a third predetermined time period. The third temperature is approximately equal to the first temperature and is maintained constant for the duration of the third time period.

[0193] It should be understood that the figures are for illustrative purposes and are not drawn to scale. Moreover, it will be understood that the aerosol-generating articles and aerosol-generating devices shown in the figures and described in detail above may have elements in addition to those discussed. Similarly, aerosol-generating articles or aerosol-generating devices according to the embodiments discussed herein may have fewer elements. Moreover, it will be apparent to one skilled in the art that the various dimensions of the elements discussed in connection with the various embodiments discussed herein are merely exemplary, and suitable alternative dimensions of the various elements may be selected.

[0194] For purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like are understood to be modified in all instances by the term "about." Also, all ranges include the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically recited herein. Thus, in this context, the number A is understood as A±10%. Within this context, the number A may be considered to include a numerical value that is within the general standard error for the measurement of the property that the number A modifies. The number A may deviate by the percentages recited above, in some instances used in the appended claims, provided that the amount by which A deviates does not materially affect the basic and novel properties of the claimed invention. Also, all ranges include the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically recited herein. Furthermore, in the context of the present invention, the expression that a number A "approximately corresponds to" a number B should be understood as meaning that the number A is equal to B ±10%.

Claims

1. A method for controlling aerosol generation in an aerosol generating device, wherein the device comprises a heating chamber configured to at least partially receive an aerosol generating article including an aerosol forming substrate, a heating system associated with a heating element configured to internally heat the aerosol forming substrate from within the aerosol forming substrate, and a power supply for supplying power to the heating system, wherein the method is The heating chamber receives the aerosol-generating article, wherein the aerosol-forming substrate has a total aerosol-forming content greater than 30 weight percent, and the aerosol-forming substrate is solid or gel. To form an aerosol for the user to inhale, The temperature of the heating element is raised from the initial temperature to a first temperature, and The method includes heating the aerosol-forming substrate by controlling the power to maintain the temperature of the heating element at a constant first temperature during the duration of a first predetermined period, wherein the first temperature is between 245 and 285 degrees Celsius. The method further includes controlling the power during a preheating period prior to the first predetermined period to raise the temperature of the heating element from the ambient temperature to the initial temperature, A method further comprising calibrating the heating element following the preheating period and before the first predetermined period.

2. The method according to claim 1, wherein controlling the power further includes adjusting the temperature of the heating element to a second temperature during a second predetermined period, the second predetermined period following the first predetermined period, and the second temperature being lower than the first temperature.

3. The method according to claim 2, wherein adjusting the temperature of the heating element to the second temperature during the second period includes two consecutive temperature steps.

4. The method according to claim 3, wherein the temperature in the first temperature step is lower than the temperature in the second temperature step.

5. The method according to any one of claims 2 to 4, wherein controlling the power further includes adjusting the temperature of the heating element to a third temperature during a third predetermined period, the third predetermined period following the second predetermined period, and the third temperature substantially corresponding to the first temperature.

6. It is a system, An aerosol generating article comprising an aerosol-forming substrate having a total aerosol-forming material content of 30% by weight or more, wherein the aerosol-forming substrate is solid or gel, Aerosol generator, A heating chamber configured to at least partially receive the aerosol generating article, A heating system associated with a heating element configured to internally heat the aerosol-forming substrate from within the aerosol-forming substrate, A power supply for providing power to the heating system, and In order to form an aerosol for the user to inhale, during the heating of the aerosol-forming substrate, The temperature of the heating element is raised from the initial temperature to a first temperature, and The aerosol generator includes a controller configured to control the power so as to maintain the temperature of the heating element at a constant first temperature during a predetermined duration, wherein the first temperature is between 245 and 285 degrees Celsius. The system is further configured such that the controller calibrates the heating element after the preheating period and before the first predetermined period, during the preheating period before the first predetermined period, so as to raise the temperature of the heating element from the ambient temperature to the initial temperature.

7. The system according to claim 6, wherein controlling the power during heating of the aerosol-forming substrate to form an aerosol for the user to inhale further includes adjusting the temperature of the heating element to a second temperature during a second predetermined period, the second predetermined period following the first predetermined period, and the second temperature being lower than the first temperature.

8. The system according to claim 7, wherein controlling the power during heating of the aerosol-forming substrate to form an aerosol for the user to inhale further includes adjusting the temperature of the heating element to a third temperature during a third predetermined period, the third predetermined period following the second predetermined period, and the third temperature substantially corresponding to the first temperature.

9. The system according to claim 6, wherein the aerosol-forming substrate further comprises the heating element, and the heating system comprises an induction coil for inductively heating the heating element.

10. The aforementioned controller The system according to claim 9, further configured to calibrate the heating element following the preheating period and before the first period.

11. The system according to claim 8, wherein the aerosol-forming substrate does not contain tobacco.

12. The system according to any one of claims 6 to 11, wherein the aerosol-forming substrate contains water, and the aerosol-forming substrate has a water content of 5% to 35% by weight.

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